2021 
Djenidi L, Antonia RA, Tang SL, 'Mathematical constraints on the scaling exponents in the inertial range of fluid turbulence', Physics of Fluids, 33 (2021) [C1]
The dominant view in the theory of fluid turbulence assumes that, once the effect of the Reynolds number is negligible, moments of order n of the longitudinal velocity increment, ... [more]
The dominant view in the theory of fluid turbulence assumes that, once the effect of the Reynolds number is negligible, moments of order n of the longitudinal velocity increment, (d u), can be described by a simple powerlaw r ¿ n, where the scaling exponent ¿n depends on n and, except for ¿ 3 (= 1), needs to be determined. In this Letter, we show that applying Hölder's inequality to the powerlaw form (d u) n ¯ ~ (r L) ¿ n (with r / L « 1; L is an integral length scale) leads to the following mathematical constraint: ¿ 2 p = p ¿ 2. When we further apply the CauchySchwarz inequality, a particular case of Hölder's inequality, to  (d u) 3 ¯  with ¿ 3 = 1, we obtain the following constraint: ¿ 2 = 2 / 3. Finally, when Hölder's inequality is also applied to the powerlaw form ( d u ) n ¯ ~ (r L) ¿ n (this form is often used in the extended selfsimilarity analysis) while assuming ¿ 3 = 1, it leads to ¿ 2 = 2 / 3. The present results show that the scaling exponents predicted by the 1941 theory of Kolmogorov in the limit of infinitely large Reynolds number comply with Hölder's inequality. On the other hand, scaling exponents, except for ¿3, predicted by current smallscale intermittency models do not comply with Hölder's inequality, most probably because they were estimated in finite Reynolds number turbulence. The results reported in this Letter should guide the development of new theoretical and modeling approaches so that they are consistent with the constraints imposed by Hölder's inequality.



2021 
Ghanadi F, Djenidi L, 'Reynolds number effect on the response of a rough wall turbulent boundary layer to local wall suction', Journal of Fluid Mechanics, 916 (2021) [C1]
The combined effect of Reynolds number and localised wall suction applied through a porous strip on a fully rough wall turbulent boundary layer (TBL) is investigated using hotwir... [more]
The combined effect of Reynolds number and localised wall suction applied through a porous strip on a fully rough wall turbulent boundary layer (TBL) is investigated using hotwire anemometry. The measurements show that the response of the TBL to suction is modulated by the ratio, where and are the suction and friction velocities, respectively. For example the suction impact on the mean velocity and the turbulence intensity profiles, which is felt across the boundary layer, decreases as decreases. Interestingly, the velocity spectra contour maps reveal that suction reduces the energy at all scales of motion across the boundary layer. Further, measurements of the velocity skewness indicate that the TBL undergoes a structural change when the ratio is relatively important. However, the measurements also reveal that TBL does not show a relaminarisation behaviour as it can be observed in a smooth wall TBL with similar localised wall suction. This lack of relaminarisation is due to the development of a growing internal boundary layer which evolves on a rough surface within the existing TBL.



2021 
Djenidi L, Antonia RA, 'Modeling the thirdorder velocity structure function in the scaling range at finite Reynolds numbers', JOURNAL OF MATHEMATICAL PHYSICS, 62 (2021)



2021 
Meldi M, Djenidi L, Antonia RA, 'Sensitivity analysis of the second and thirdorder velocity structure functions to the Reynolds number in decaying and forced isotropic turbulence using the EDQNM model', European Journal of Mechanics, B/Fluids, 88 229242 (2021) [C1]
Numerical calculations based on a recent version of the eddydamped quasinormal model (EDQNMLMFA) are carried out for homogeneous isotropic turbulence (HIT) with the aim of inve... [more]
Numerical calculations based on a recent version of the eddydamped quasinormal model (EDQNMLMFA) are carried out for homogeneous isotropic turbulence (HIT) with the aim of investigating the dependency on the Reynolds number of second and third order velocity structure functions. The quantities investigated include the energy spectrum E, the nonlinear energy transfer T as well as the second (S2) and third (S3) order moments of the longitudinal velocity increment. Both free decaying HIT and (steady state) forced HIT are considered. The analysis of the structure functions for Re¿¿[50,106] indicates that, regardless of whether one considers decaying or forced HIT, the large scales affect S2 and S3 in the scaling range. In that range, forcing affects S2 and S3 differently. For forced HIT, S2/(¿¯r)2/3 exhibits a distinct ¿bump¿ near the upper end of the scaling range while no such bump is seen for S3/(¿¯r). The latter quantity remains approximately constant for values of r which extend to the scale corresponding to the forcing. For decaying HIT, there is no discernible bump in either S2/(¿¯r)2/3 or S3/(¿¯r). The slope of S3 in the scaling range approaches the theoretical value of 1, when Re¿ is sufficiently large. However, at similar Re¿, the slope of S2 has not yet reached a constant for either decaying or forced HIT.



2021 
Khezerloo M, Djenidi L, Tardu S, 'Combined effect of roughness and suction on heat transfer in a laminar channel flow', International Communications in Heat and Mass Transfer, 126 (2021)
A twodimensional numerical simulation is carried with the aim to investigate the combined effects of roughness and wall suction on heat transfer performance of a steadystate lam... [more]
A twodimensional numerical simulation is carried with the aim to investigate the combined effects of roughness and wall suction on heat transfer performance of a steadystate laminar channel flow. The roughness considered as a square element mounted on the bottom wall of the channel and suction is applied on its walls. Different Reynolds numbers, different suction rates, and various locations of the suction area on the roughness elements are considered. The governing NavierStokes equations are solved using open source OpenFOAM software. The results are tested against theoretical results. It is shown that the simple addition of roughness element increases the local Nusselt number in comparison to that without roughness. That increase is further enhanced when localised suction is applied. In addition, it is observed that by applying suction strategically on the roughness, one can reduce the thickness of thermal boundary layer, and remove or at least weaken the vortical motion behind the backface of element, which in turn leads to an increase in local Nusselt number, demonstrating that suction is an effective means for improving the heat transfer rate in a laminar channel flow. As continuation of study, the effect of space between two elements was investigated and the best space was obtained. It is found that this method is useful to enhance heat transfer performance, especially at high Reynolds numbers.



2021 
Ghanadi F, Djenidi L, 'Spatial resolution effects on measurements in a rough wall turbulent boundary layer', EXPERIMENTS IN FLUIDS, 62 (2021)



2021 
Mishra A, Djenidi L, Agrawal A, 'Dynamics of wall jet flow under external pulsation', Physics of Fluids, 33 (2021)
The present study aims to identify the dominant coherent structures in the wall jet flow subjected to external pulsation at Reynolds number 2600 (based on average jet exit velocit... [more]
The present study aims to identify the dominant coherent structures in the wall jet flow subjected to external pulsation at Reynolds number 2600 (based on average jet exit velocity and nozzle diameter). The forcing frequency is varied between St¿=¿0 and 0.99 (St is the Strouhal number). Quadrant analysis is employed to identify the relative contribution of different quadrant motions to the total Reynolds shear stress. Unlike boundary layer flows and channel flows, two distinct regions (inner shear region and outer shear region) are observed in the wall jet flows, and the characteristics of different quadrant motions change in these regions. About 70% of the total shear stress is contributed from the first and fourth quadrants in the outer shear region. We observe that ejection motion is more energetic than sweep motion in the downstream direction, although less frequent. The ejection motion is observed to be more violent for St¿=¿0.44 than for the other frequencies. A proper orthogonal decomposition (POD) analysis reveals while the modal structures exist in different regions of the wall for different jet pulsation; there are no dominant modes (30 modes are required to recover about 75% of the total energy), and the energy is fairly distributed over a large number of modes. However, the POD analyses are capable of capturing the response of the wall jet to different jet pulsations. The most dominant and strongest modal structures are found nearer to the impingement region of the wall when St¿=¿0.44 and the jet tends to laminarize for St¿>¿0.9.



2021 
Mishra A, Yadav H, Djenidi L, Agrawal A, 'Effect of pulsation on the wall jet flow in the near region of an impinging jet', EXPERIMENTS IN FLUIDS, 62 (2021)



2020 
Tang SL, Antonia RA, Djenidi L, Zhou Y, 'Scaling of the turbulent energy dissipation correlation function', Journal of Fluid Mechanics, 891 (2020) [C1]



2020 
Mishra A, Yadav H, Djenidi L, Agrawal A, 'Experimental study of flow characteristics of an oblique impinging jet', Experiments in Fluids, 61 (2020) [C1]



2020 
Anika NN, Djenidi L, Tardu S, 'Roughness effect in an initially laminar channel flow', Journal of Fluid Mechanics, 892 (2020) [C1]



2020 
Djenidi L, Antonia RA, 'Assessment of largescale forcing in isotropic turbulence using a closed KarmanHowarth equation', Physics of Fluids, 32 (2020) [C1]



2020 
Lemay J, Djenidi L, Antonia R, 'Estimation of mean turbulent kinetic energy and temperature variance dissipation rates using a spectral chart method', Physics of Fluids, 32 (2020) [C1]



2019 
Djenidi L, Talluru KM, Antonia RA, 'A velocity defect chart method for estimating the friction velocity in turbulent boundary layers', FLUID DYNAMICS RESEARCH, 51 (2019) [C1]



2019 
Antonia RA, Tang SL, Djenidi L, Zhou Y, 'Finite Reynolds number effect and the 4/5 law', PHYSICAL REVIEW FLUIDS, 4 (2019) [C1]



2019 
Tang S, Antonia RA, Djenidi L, Zhou Y, 'Can smallscale turbulence approach a quasiuniversal state?', PHYSICAL REVIEW FLUIDS, 4 (2019) [C1]



2019 
Djenidi L, Antonia RA, Tang SL, 'Scale invariance in finite Reynolds number homogeneous isotropic turbulence', Journal of Fluid Mechanics, 864 244272 (2019) [C1]



2019 
Lemay J, Djenidi L, Antonia RA, Benaissa A, 'An empirical expression for epsilon(theta) on the axis of a slightly heated turbulent round jet', JOURNAL OF FLUID MECHANICS, 867 392413 (2019) [C1]



2019 
Djenidi L, Kamruzzaman M, Dostal L, 'Effects of wall suction on a 2D rough wall turbulent boundary layer', Experiments in Fluids, 60 (2019) [C1]



2018 
Kamruzzaman M, Djenidi L, Antonia RA, 'Behaviour of the energy dissipation coefficient in a rough wall turbulent boundary layer', Experiments in Fluids, 59 (2018) [C1]



2018 
Tang SL, Antonia RA, Djenidi L, Danaila L, Zhou Y, 'Reappraisal of the velocity derivative flatness factor in various turbulent flows', Journal of Fluid Mechanics, 847 244265 (2018) [C1]



2018 
Tang SL, Djenidi L, Antonia RA, Zhou Y, 'Secondary vortex street in the intermediate wake of a circular cylinder', Experiments in Fluids, 59 (2018) [C1]



2018 
Anika NN, Djenidi L, Tardu S, 'Bypass transition mechanism in a rough wall channel flow', PHYSICAL REVIEW FLUIDS, 3 (2018) [C1]



2018 
Meldi M, Djenidi L, Antonia R, 'Reynolds number effect on the velocity derivative flatness factor', JOURNAL OF FLUID MECHANICS, 856 426443 (2018) [C1]



2018 
Djenidi L, Talluru KM, Antonia RA, 'Can a turbulent boundary layer become independent of the Reynolds number?', JOURNAL OF FLUID MECHANICS, 851 (2018) [C1]



2017 
Djenidi L, Antonia RA, Danaila L, 'Selfpreservation relation to the Kolmogorov similarity hypotheses', PHYSICAL REVIEW FLUIDS, 2 (2017) [C1]



2017 
Djenidi L, Lefeuvre N, Kamruzzaman M, Antonia RA, 'On the normalized dissipation parameter Cepsilon in decaying turbulence', JOURNAL OF FLUID MECHANICS, 817 6179 (2017) [C1]



2017 
Tang SL, Antonia RA, Djenidi L, Danaila L, Zhou Y, 'Finite Reynolds number effect on the scaling range behaviour of turbulent longitudinal velocity structure functions', JOURNAL OF FLUID MECHANICS, 820 341369 (2017) [C1]



2017 
Antonia RA, Djenidi L, Danaila L, Tang SL, 'Small scale turbulence and the finite Reynolds number effect', PHYSICS OF FLUIDS, 29 (2017) [C1]



2017 
Djenidi L, Danaila L, Antonia RA, Tang S, 'A note on the velocity derivative flatness factor in decaying HIT', PHYSICS OF FLUIDS, 29 (2017) [C1]



2017 
Djenidi L, Antonia RA, Talluru MK, Abe H, 'Skewness and flatness factors of the longitudinal velocity derivative in wallbounded flows', PHYSICAL REVIEW FLUIDS, 2 (2017) [C1]



2016 
Djenidi L, Antonia RA, Lefeuvre N, Lemay J, 'Complete selfpreservation on the axis of a turbulent round jet', Journal of Fluid Mechanics, 790 5770 (2016) [C1]
Selfpreservation (SP) solutions on the axis of a turbulent round jet are derived for the transport equation of the secondorder structure function of the turbulent kinetic energy... [more]
Selfpreservation (SP) solutions on the axis of a turbulent round jet are derived for the transport equation of the secondorder structure function of the turbulent kinetic energy , which may be interpreted as a scalebyscale (s.b.s.) energy budget. The analysis shows that the mean turbulent energy dissipation rate, , evolves like ( is the streamwise direction). It is important to stress that this derivation does not use the constancy of the nondimensional dissipation rate parameter ( and are the integral length scale and root mean square of the longitudinal velocity fluctuation respectively). We show, in fact, that the constancy of is simply a consequence of complete SP (i.e. SP at all scales of motion). The significance of the analysis relates to the fact that the SP requirements for the mean velocity and mean turbulent kinetic energy (i.e. and respectively) are derived without invoking the transport equations for and . Experimental hotwire data along the axis of a turbulent round jet show that, after a transient downstream distance which increases with Reynolds number, the turbulence statistics comply with complete SP. For example, the measured agrees well with the SP prediction, i.e. , while the Taylor microscale Reynolds number remains constant. The analytical expression for the prefactor for (where is a virtual origin), first developed by Thiesset et al. (J. Fluid Mech., vol. 748, 2014, R2) and rederived here solely from the SP analysis of the s.b.s. energy budget, is validated and provides a relatively simple and accurate method for estimating along the axis of a turbulent round jet.



2016 
Tang SL, Antonia RA, Djenidi L, Zhou Y, 'Complete selfpreservation along the axis of a circular cylinder far wake', Journal of Fluid Mechanics, 786 253274 (2016) [C1]



2016 
Tang SL, Antonia RA, Djenidi L, Danaila L, Zhou Y, 'Boundedness of the mixed velocitytemperature derivative skewness in homogeneous isotropic turbulence', Physics of Fluids, 28 (2016) [C1]
The transport equation for the mean scalar dissipation rate ¿¿ is derived by applyingthe limit at small separations to the generalized form of Yaglom's equation in twotypes o... [more]
The transport equation for the mean scalar dissipation rate ¿¿ is derived by applyingthe limit at small separations to the generalized form of Yaglom's equation in twotypes of flows, those dominated mainly by a decay of energy in the streamwisedirection and those which are forced, through a continuous injection of energy atlarge scales. In grid turbulence, the imbalance between the production of ¿¿ dueto stretching of the temperature field and the destruction of ¿¿ by the thermaldiffusivity is governed by the streamwise advection of ¿¿ by the mean velocity.This imbalance is intrinsically different from that in stationary forced periodic boxturbulence (or SFPBT), which is virtually negligible. In essence, the different typesof imbalance represent different constraints imposed by the largescale motion on therelation between the socalled mixed velocitytemperature derivative skewness STand the scalar enstrophy destruction coefficient G¿ in different flows, thus resultingin nonuniversal approaches of ST towards a constant value as Re¿ increases. Thedata for ST collected in grid turbulence and in SFPBT indicate that the magnitudeof ST is bounded, this limit being close to 0.5.



2016 
Tang SL, Antonia RA, Danaila L, Djenidi L, Zhou T, Zhou Y, 'Towards local isotropy of higherorder statistics in the intermediate wake', EXPERIMENTS IN FLUIDS, 57 (2016) [C1]



2016 
Talluru KM, Djenidi L, Kamruzzaman M, Antonia RA, 'Selfpreservation in a zero pressure gradient roughwall turbulent boundary layer', JOURNAL OF FLUID MECHANICS, 788 5769 (2016) [C1]



2015 
Tang SL, Djenidi L, Antonia RA, Zhou Y, 'Comparison between velocity and vorticitybased POD methods in a turbulent wake', Experiments in Fluids, 56 (2015) [C1]
In this paper, the velocitybased POD and the vorticitybased POD have been systematically compared in three characteristic regions of the flow downstream of a twodimensional cir... [more]
In this paper, the velocitybased POD and the vorticitybased POD have been systematically compared in three characteristic regions of the flow downstream of a twodimensional circular cylinder, namely the near, intermediate and far wakes. The twopoint space correlation function is used to determine which of the two methods is better suited for extracting the largescale flow structures based on the repartition of energy among the different POD modes. It is found that the POD, based on the lateral velocity fluctuation v, leads to the most optimum extraction in all three flow regions, while the vorticitybased POD is only effective in the near and intermediate wakes. Based on twopoint space correlation functions, a scenario is proposed for the application of POD to the present twodimensional wake.



2015 
Kamruzzaman M, Djenidi L, Antonia RA, Talluru KM, 'Scalebyscale energy budget in a turbulent boundary layer over a rough wall', International Journal of Heat and Fluid Flow, (2015) [C1]
Hotwire velocity measurements are carried out in a turbulent boundary layer over a rough wall consisting of transverse circular rods, with a ratio of 8 between the spacing (w) of... [more]
Hotwire velocity measurements are carried out in a turbulent boundary layer over a rough wall consisting of transverse circular rods, with a ratio of 8 between the spacing (w) of two consecutive rods and the rod height (k). The pressure distribution around the roughness element is used to accurately measure the mean friction velocity (Ut) and the error in the origin. It is found that Ut remained practically constant in the streamwise direction suggesting that the boundary layer over this surface is evolving in a selfsimilar manner. This is further corroborated by the similarity observed at all scales of motion, in the region 0.2=y/d=0.6, as reflected in the constancy of Reynolds number (R¿) based on Taylor's microscale and the collapse of Kolmogorov normalized velocity spectra at all wavenumbers.A scalebyscale budget for the secondorder structure function <(du)2> (du=u(x+r)u(x), where u is the fluctuating streamwise velocity component and r is the longitudinal separation) is carried out to investigate the energy distribution amongst different scales in the boundary layer. It is found that while the small scales are controlled by the viscosity, intermediate scales over which the transfer of energy (or <(du)3>) is important are affected by mechanisms induced by the largescale inhomogeneities in the flow, such as production, advection and turbulent diffusion. For example, there are nonnegligible contributions from the largescale inhomogeneity to the budget at scales of the order of ¿, the Taylor microscale, in the region of the boundary layer extending from y/d=0.2 to 0.6 (d is the boundary layer thickness).



2015 
Tang SL, Antonia RA, Djenidi L, Zhou Y, 'Transport equation for the isotropic turbulent energy dissipation rate in the farwake of a circular cylinder', Journal of Fluid Mechanics, 784 109129 (2015) [C1]
The transport equation for the isotropic turbulent energy dissipation rate along the centreline in the farwake of a circular cylinder is derived by applying the limit at small se... [more]
The transport equation for the isotropic turbulent energy dissipation rate along the centreline in the farwake of a circular cylinder is derived by applying the limit at small separations to the twopoint energy budget equation. It is found that the imbalance between the production and the destruction of eiso, respectively due to vortex stretching and viscosity, is governed by both the streamwise advection and the lateral turbulent diffusion (the former contributes more to the budget than the latter). This imbalance differs intrinsically from that in other flows, e.g. grid turbulence and the flow along the centreline of a fully developed channel, where either the streamwise advection or the lateral turbulent diffusion of eiso governs the imbalance. More importantly, the different types of imbalance represent different constraints on the relation between the skewness of the longitudinal velocity derivative and the destruction coefficient of enstrophy G. This results in a nonuniversal approach of towards a constant value as the Taylor microscale Reynolds number R¿ increases. For the present flow, the magnitude of S decreases initially before increasing (R¿ > 40) towards this constant value. The constancy of S at large R¿ violates the modified similarity hypothesis introduced by Kolmogorov (J. Fluid Mech., vol. 13, 1962, pp. 8285) but is consistent with the original similarity hypotheses (Kolmogorov, Dokl. Akad. Nauk SSSR, vol. 30, 1941b, pp. 299303 (see also 1991 Proc. R. Soc. Lond. A, vol. 434, pp. 913)) , and, more importantly, with the almost completely selfpreserving nature of the plane farwake.



2015 
Leonardi S, Orlandi P, Djenidi L, Antonia RA, 'Heat transfer in a turbulent channel flow with square bars or circular rods on one wall', Journal of Fluid Mechanics, 776 512530 (2015) [C1]
Direct numerical simulations (DNS) are carried out to study the passive heat transport in a turbulent channel flow with either square bars or circular rods on one wall. Several va... [more]
Direct numerical simulations (DNS) are carried out to study the passive heat transport in a turbulent channel flow with either square bars or circular rods on one wall. Several values of the pitch to height ratio and two Reynolds numbers are considered. The roughness increases the heat transfer by inducing ejections at the leading edge of the roughness elements. The amounts of heat transfer and mixing depend on the separation between the roughness elements, an increase in heat transfer accompanying an increase in drag. The ratio of nondimensional heat flux to the nondimensional wall shear stress is higher for circular rods than square bars irrespectively of the pitch to height ratio. The turbulent heat flux varies within the cavities and is larger near the roughness elements. Both momentum and thermal eddy diffusivities increase relative to the smooth wall. For square cavities the turbulent Prandtl number is smaller than for a smooth channel near the wall. As increases, the turbulent Prandtl number increases up to a maximum of 2.5 at the crests plane of the square bars . With increasing distance from the wall, the differences with respect to the smooth wall vanish and at three roughness heights above the crests plane, the turbulent Prandtl number is essentially the same for smooth and rough walls.



2015 
Tang SL, Antonia RA, Djenidi L, Abe H, Zhou T, Danaila L, Zhou Y, 'Transport equation for the mean turbulent energy dissipation rate on the centreline of a fully developed channel flow', Journal of Fluid Mechanics, 777 151177 (2015) [C1]
The transport equation for the mean turbulent energy dissipation rate along the centreline of a fully developed channel flow is derived by applying the limit at small separations ... [more]
The transport equation for the mean turbulent energy dissipation rate along the centreline of a fully developed channel flow is derived by applying the limit at small separations to the twopoint budget equation. Since the ratio of the isotropic energy dissipation rate to the mean turbulent energy dissipation rate is sufficiently close to 1 on the centreline, our main focus is on the isotropic form of the transport equation. It is found that the imbalance between the production of due to vortex stretching and the destruction of caused by the action of viscosity is governed by the diffusion of by the wallnormal velocity fluctuation. This imbalance is intrinsically different from the advectiondriven imbalance in decayingtype flows, such as grid turbulence, jets and wakes. In effect, the different types of imbalance represent different constraints on the relation between the skewness of the longitudinal velocity derivative and the destruction coefficient of enstrophy in different flows, thus resulting in nonuniversal approaches of towards a constant value as the Taylor microscale Reynolds number, , increases. For example, the approach is slower for the measured values of along either the channel or pipe centreline than along the axis in the selfpreserving region of a round jet. The data for collected in different flows strongly suggest that, in each flow, the magnitude of is bounded, the value being slightly larger than 0.5.



2015 
Djenidi L, Antonia RA, 'A general selfpreservation analysis for decaying homogeneous isotropic turbulence', Journal of Fluid Mechanics, 773 345365 (2015) [C1]
A general framework of selfpreservation (SP) is established, based on the transport equation of the secondorder longitudinal velocity structure function in decaying homogeneous ... [more]
A general framework of selfpreservation (SP) is established, based on the transport equation of the secondorder longitudinal velocity structure function in decaying homogeneous isotropic turbulence (HIT). The analysis introduces the skewness of the longitudinal velocity increment, S(r, t) (r and t are space increment and time), as an SP controlling parameter. The present SP framework allows a critical appraisal of the specific assumptions that have been made in previous SP analyses. It is shown that SP is achieved when S(r, t) varies in a selfsimilar manner, i.e. S=c(t)f(r/l) where l is a scaling length, and c(t) and f(r/l) are dimensionless functions of time and (r/l), respectively. When c(t) is constant, l can be identified with the Kolmogorov length scale ¿, even when the Reynolds number is relatively small. On the other hand, the Taylor microscale ¿ is a relevant SP length scale only when certain conditions are met. The decay law for the turbulent kinetic energy (k) ensuing from the present SP is a generalization of the existing laws and can be expressed as k ~ (tt<inf>0</inf>)<sup>n</sup>+B, where B is a constant representing the energy of the motions whose scales are excluded from the SP range of scales. When B = 0, SP is achieved at all scales of motion and ¿ becomes a relevant scaling length together with ¿. The analysis underlines the relation between the initial conditions and the powerlaw exponent n and also provides a link between them. In particular, an expression relating n to the initial values of the scaling length and velocity is developed. Finally, the present SP analysis is consistent with both experimental grid turbulence data and the eddydamped quasinormal Markovian numerical simulation of decaying HIT by Meldi & Sagaut (J. Turbul., vol. 14, 2013, pp. 2453).



2015 
Djenidi L, Kamruzzaman M, Antonia RA, 'Powerlaw exponent in the transition period of decay in grid turbulence', JOURNAL OF FLUID MECHANICS, 779 (2015) [C1]



2015 
Kamruzzaman M, Djenidi L, Antonia RA, Talluru KM, 'Drag of a turbulent boundary layer with transverse 2D circular rods on the wall', EXPERIMENTS IN FLUIDS, 56 (2015) [C1]



2015 
Antonia RA, Tang SL, Djenidi L, Danaila L, 'Boundedness of the velocity derivative skewness in various turbulent flows', Journal of Fluid Mechanics, 781 727744 (2015) [C1]
The variation of S, the velocity derivative skewness, with the Taylor microscale Reynolds number Re¿ is examined for different turbulent flows by considering the locally isotropic... [more]
The variation of S, the velocity derivative skewness, with the Taylor microscale Reynolds number Re¿ is examined for different turbulent flows by considering the locally isotropic form of the transport equation for the mean energy dissipation rate e¯iso. In each flow, the equation can be expressed in the form S C 2G=Re¿ D C=Re¿, where G is a nondimensional rate of destruction of e¯iso and C is a flowdependent constant. Since 2G=Re¿ is found to be very nearly constant for Re¿ = 70, S should approach a universal constant when Re¿ is sufficiently large, but the way this constant is approached is flow dependent. For example, the approach is slow in grid turbulence and rapid along the axis of a round jet. For all the flows considered, the approach is reasonably well supported by experimental and numerical data. The constancy of S at large Re¿ has obvious ramifications for smallscale turbulence research since it violates the modified similarity hypothesis introduced by Kolmogorov (J. Fluid Mech., vol. 13, 1962, pp. 8285) but is consistent with the original similarity hypothesis (Kolmogorov, Dokl. Akad. Nauk SSSR, vol. 30, 1941, pp. 299303).



2014 
Thiesset F, Antonia RA, Djenidi L, 'Consequences of selfpreservation on the axis of a turbulent round jet', JOURNAL OF FLUID MECHANICS, 748 (2014) [C1]



2014 
Djenidi L, Antonia RA, 'Transport equation for the mean turbulent energy dissipation rate in lowRlambda grid turbulence', JOURNAL OF FLUID MECHANICS, 747 288315 (2014) [C1]



2014 
Lee SK, Djenidi L, Antonia RA, 'Empirical correlations for slightly heated decaying passivegrid turbulence', Heat Transfer Engineering, 35 14821490 (2014) [C1]
For homogeneous isotropic turbulence approximated by grid turbulence, velocity and temperature fluctuations decay under the effects of viscosity and thermal diffusivity of the flu... [more]
For homogeneous isotropic turbulence approximated by grid turbulence, velocity and temperature fluctuations decay under the effects of viscosity and thermal diffusivity of the fluid. In the selfsimilar region of grid flow, there is no mean shear and no turbulence production, and the decay rate is well represented by a power law; this is supported by the present measurements in three different grid flows and by previously published data for passivegrid turbulence obtained over different ranges of streamwise distance and/or Reynolds number. The grid flow is slightly heated so that temperature acts as a passive scalar. From dimensional analysis and empirical powerlaw correlations, relations for basic flow parameters, such as the Kolmogorov, Taylor, and Corrsin microscales, and the Reynolds and Péclet numbers, are established as functions of the normalized streamwise distance downstream of the grid. With these relations, it is possible to determine the flow parameters for a specific passivegrid geometry or, more generally, a specific set of initial conditions. © 2014 Copyright Taylor & Francis Group, LLC.



2014 
Djenidi L, Antonia RA, Amielh M, Anselmet F, 'Use of PIV to highlight possible errors in hotwire Reynolds stress data over a 2D rough wall', EXPERIMENTS IN FLUIDS, 55 (2014) [C1]



2014 
Lefeuvre N, Thiesset F, Djenidi L, Antonia RA, 'Statistics of the turbulent kinetic energy dissipation rate and its surrogates in a square cylinder wake flow', Physics of Fluids, 26 (2014) [C1]
A numerical simulation based on the lattice Boltzmann method is carried out in the wake of a square cylinder with the view to investigating possible surrogates for the instantaneo... [more]
A numerical simulation based on the lattice Boltzmann method is carried out in the wake of a square cylinder with the view to investigating possible surrogates for the instantaneous turbulent kinetic energy dissipation rate, Ie{cyrillic, ukrainian}, as well as its mean value, \documentclass[12pt]{minimal}\begin{document}$\overline{\epsilon }$\end{document}Ie{cyrillic, ukrainian}. Various surrogate approximations of Ie{cyrillic, ukrainian}, based on local isotropy (Ie{cyrillic, ukrainian}iso), local axisymmetry along the streamwise direction x (Ie{cyrillic, ukrainian}a, x) and the transverse direction y (Ie{cyrillic, ukrainian}a, y), local homogeneity (Ie{cyrillic,ukrainian}hom), and homogeneity in the transverse plane, (Ie{cyrillic,ukrainian}4x), are assessed. All the approximations are in agreement with \documentclass[12pt]{minimal}\begin{document}$\overline{\epsilon }$\end{document}Ie{cyrillic,ukrainian}when the distance downstream of the obstacle is larger than about 40 diameters. Closer to the obstacle, the agreement remains reasonable only for \documentclass[12pt]{minimal}\begin{document}$\overline{\epsilon }_{a,x}$\end{document}Ie{cyrillic, ukrainian}a,x, \documentclass[12pt]{minimal}\begin{document}$\overline{\epsilon }{hom}$\end{document}?hom and \documentclass[12pt]{minimal}\begin{document}$\overline{\epsilon }{4x}$\end{document}Ie{cyrillic, ukrainian}4x. The probability density functions (PDF) and joint PDFs of Ie{cyrillic, ukrainian} and its surrogates show that Ie{cyrillic, ukrainian}4x correlates best withIe{cyrillic, ukrainian}while ?iso and Ie{cyrillic, ukrainian}hom present the smallest correlation. The results indicate that Ie{cyrillic, ukrainian}4x is a very good surrogate for Ie{cyrillic, ukrainian}and can be used for correctly determining the behaviour of Ie{cyrillic, ukrainian}.



2014 
Antonia RA, Djenidi L, Danaila L, 'Collapse of the turbulent dissipative range on Kolmogorov scales', PHYSICS OF FLUIDS, 26 (2014) [C1]



2014 
Thiesset F, Schaeffer V, Djenidi L, Antonia RA, 'On selfpreservation and logsimilarity in a slightly heated axisymmetric mixing layer', PHYSICS OF FLUIDS, 26 (2014) [C1]



2014 
Djenidi L, Tardu SF, Antonia RA, Danaila L, 'Breakdown of Kolmogorov's first similarity hypothesis in grid turbulence', JOURNAL OF TURBULENCE, 15 596610 (2014) [C1]



2013 
Antonia RA, Lee SK, Djenidi L, Lavoie P, Danaila L, 'Invariants for slightly heated decaying grid turbulence', JOURNAL OF FLUID MECHANICS, 727 379406 (2013) [C1]



2013 
Rajagopalan S, Antonia RA, Djenidi L, 'Effect of mesh grids on the turbulent mixing layer of an axisymmetric jet', Heat Transfer Engineering, 34 12161225 (2013) [C1]
This article focuses on the effect that two different mesh grids have on the structure of the mixing layer of an axisymmetric jet. Detailed measurements of mean velocity and turbu... [more]
This article focuses on the effect that two different mesh grids have on the structure of the mixing layer of an axisymmetric jet. Detailed measurements of mean velocity and turbulent velocity fluctuations are made with an X hotwire probe in the range 0.5 = x/d = 10, where x is the longitudinal distance from the nozzle exit plane and d is the nozzle diameter. The grids are introduced at two locationsone location just downstream of the nozzle exit plane and the other location upstream of the nozzle exit plane in order to perturb the nozzle exit boundary layer. One mesh completely covers the nozzle (full mesh or FM) and the other mesh covers the central, highspeed zone (disk mesh or DM). With reference to the undisturbed jet, FM yields a significant reduction in the turbulence intensity and width of the shear layer, whereas DM enhances the turbulence intensity and increases the width of the shear layer. Both grids suppress the formation of the KelvinHelmholtz instability in the mixing layer. Results are presented, mainly at x/d = 5 and 6 in both the spectral domain and physical space. In the latter context, secondand thirdorder structure functions associated with u (the longitudinal velocity fluctuation) and v (the lateral or radial velocity fluctuation) are presented only for the flow perturbed by placing the mesh outside the nozzle. All mesh geometries have a more significant effect on the secondorder structure function of u than on that of v. The thirdorder energy transfer term is affected in such a way that, relative to the undisturbed jet, its peak location is shifted to a smaller scale when FM is used and to a larger scale with DM. This is consistent with our observations that FM reduces the turbulence in the shear layer while DM enhances it. It is suggested that the largescale vortices that are formed at the edge of the grids play a significant role in the transfer of energy. © 2013 Taylor & Francis Group, LLC.



2013 
Djenidi L, Tardu SF, Antonia RA, 'Relationship between temporal and spatial averages in grid turbulence', Journal of Fluid Mechanics, 730 593606 (2013) [C1]



2013 
Thiesset F, Antonia RA, Danaila L, Djenidi L, 'KarmanHowarth closure equation on the basis of a universal eddy viscosity', PHYSICAL REVIEW E, 88 (2013) [C1]



2013 
Kamruzzaman M, Wahiduzzaman M, Alam MM, Djenidi L, 'The effects of magnetic field on the fluid flow through a rotating straight duct with large aspect ratio', Procedia Engineering, 56 239244 (2013) [C1]
This paper presents a numerical study of an investigation of a fluid flow through a rotating rectangular straight duct in the presence of magnetic field. The straight duct of rect... [more]
This paper presents a numerical study of an investigation of a fluid flow through a rotating rectangular straight duct in the presence of magnetic field. The straight duct of rectangular crosssection rotates at a constant angular velocity about the centre of the duct crosssection is same as the axis of the magnetic field along the positive direction in the stream wise direction of the flows. Numerical calculation is based on the Magneto hydrodynamics incompressible viscous steady fluid model whereas Spectral method is applied as a main tool. Flow depends on the Magnetic parameter, Dean number and Taylor number. One of the interesting phenomena of the fluid flow is the solution curve and the flow structures in case of rotation of the duct axis. The calculation are carried out for 5 = Mg = 50000, 50 = Tr 100000, Dn 500, 1000, 1500 and 2000 where the aspect ratio ¿ 3.0. The maximum axial flow will be shifted to the centre from the wall and turn into the ring shape under the effects of high magnetic parameter and large Taylor number whereas the fluid particles strength is weak. © 2013 The Authors. Published by Elsevier Ltd.



2012 
Djenidi L, Tardu SF, 'On the anisotropy of a lowReynoldsnumber grid turbulence', Journal of Fluid Mechanics, 702 332353 (2012) [C1]



2012 
Djenidi L, Antonia RA, 'A spectral chart method for estimating the mean turbulent kinetic energy dissipation rate', Experiments in Fluids, 53 10051013 (2012) [C1]



2012 
Lee SK, Benaissa A, Djenidi L, Lavoie P, Antonia RA, 'Decay of passivescalar fluctuations in slightly stretched grid turbulence', Experiments in Fluids, 53 909923 (2012) [C1]



2012 
Lee SK, Benaissa A, Djenidi L, Lavoie P, Antonia RA, 'Scaling range of velocity and passive scalar spectra in grid turbulence (vol 24, 075101, 2012)', PHYSICS OF FLUIDS, 24 (2012) [C3]



2012 
Lee SK, Benaissa A, Djenidi L, Lavoie P, Antonia RA, 'Scaling range of velocity and passive scalar spectra in grid turbulence', Physics of Fluids, 24 (2012) [C1]



2011 
Lefeuvre N, Djenidi L, Tardu S, 'Momentum and scalar transport in a localised synthetic turbulence in a channel flow with a short contraction', Journal of Physics: Conference Series, 318 (2011) [C1]



2010 
Djenidi L, Antonia R, Amielh M, Anselmet F, 'POD analysis of the nearwall region of a rough wall turbulent boundary layer', IUTAM Bookseries, 22 4954 (2010)
A proper orthogonal decomposition (POD) analysis is carried out with particle image velocity (PIV) measurements of a turbulent boundary layer over a rough wall made of transverse ... [more]
A proper orthogonal decomposition (POD) analysis is carried out with particle image velocity (PIV) measurements of a turbulent boundary layer over a rough wall made of transverse square bars. Two bar spacings were investigated (w/k = 3 and 7, w is the bar spacing and k the bar diameter). This ratio affects the energy distribution amongst the POD modes throughout the boundary layer, the higher modes, i.e. the relatively smallscale and less energetic motions, being the most perturbed. The first few nearwall POD modes were also affected by the spacing. © Springer Science+Business Media B.V. 2010.



2010 
Agrawal A, Djenidi L, Antonia RA, 'Nearfield measurements and development of a new boundary layer over a flat plate with localized suction', Experiments in Fluids, 48 747762 (2010) [C1]



2010 
Antonia RA, Lavoie P, Djenidi L, Benaissa A, 'Effect of a small axisymmetric contraction on grid turbulence', Experiments in Fluids, 49 310 (2010) [C1]



2009 
Djenidi L, Antonia RA, 'Momentum and heat transport in a threedimensional transitional wake of a heated square cylinder', Journal of Fluid Mechanics, 640 109129 (2009) [C1]



2009 
Agrawal A, Djenidi L, Agrawal A, 'Simulation of gas flow in microchannels with a single 90 degrees bend', Computers & Fluids, 38 16291637 (2009) [C1]



2009 
Djenidi L, Agrawal A, Antonia RA, 'Anisotropy measurements in the boundary layer over a flat plate with suction', Experimental Thermal and Fluid Science, 33 11061111 (2009) [C1]



2008 
Djenidi L, 'Structure of a turbulent crossbar nearwake studied by means of lattice Boltzmann simulation', Physical Review E, 77 (2008) [C1]



2008 
Oyewola O, Djenidi L, Antonia RA, 'Response of mean turbulent energy dissipation rate and spectra to concentrated wall suction', Experiments in Fluids, 44 159165 (2008) [C1]



2008 
Djenidi L, Antonia RA, Amielh M, Anselmet F, 'A turbulent boundary layer over a twodimensional rough wall', Experiments in Fluids, 44 3747 (2008) [C1]



2007 
Oyewola O, Djenidi L, Antonia RA, 'Influence of localised double suction on a turbulent boundary layer', Journal of Fluids and Structures, 23 787798 (2007) [C1]



2007 
Oyewola MO, Djenidi L, Antonia RA, 'Examination of anisotropy of the smallscale motion in a perturbed low Reynolds number turbulent boundary layer', Experimental Thermal and Fluid Science, 32 309315 (2007) [C1]



2007 
Benaissa A, Djenidi L, Antonia RA, Parker R, 'Effect of initial conditions on the scalar decay in grid turbulence at low R
Decaying grid turbulence is considered at low Reynolds number (R ¿~ 50) for different initial conditions. Three different grid geometries are used. Heat is injected via a mandolin... [more]
Decaying grid turbulence is considered at low Reynolds number (R ¿~ 50) for different initial conditions. Three different grid geometries are used. Heat is injected via a mandoline at a distance of 1.5 M from the grid. The amount of heating is such that temperature may be treated as a passive scalar. A small contraction (1.36:1) is added at a distance of 11M downstream of the grid. The powerlaw exponents for the scalar variance are compared with those for the turbulent kinetic energy. These exponents depend on the grid geometry. For the isotropic dissipation rate (Chi;) iso, the powerlaw exponent agrees with that inferred from the temperature variance transport equation. Restricting the range of validity of the decay law affects the magnitudes of the origin and decay exponent. Secondorder temperature structure functions collapse when the normalization is based on the local temperature variance and the Corrsin microscale but the asymptotic form of this collapse depends on the initial conditions.



2007 
Lavoie PLD, Djenidi L, Antonia RA, 'Effects of initial conditions in decaying turbulence generated by passive grids', Journal of Fluid Mechanics, 585 395420 (2007) [C1]



2006 
Djenidi L, 'LatticeBoltzmann simulation of gridgenerated turbulence', Journal of Fluid Mechanics, 552 1335 (2006) [C1]



2006 
Djenidi L, Moghtaderi B, 'Numerical investigation of laminar mixing in a coaxial microreactor', Journal of Fluid Mechanics, 568 223242 (2006) [C1]



2006 
Moghtaderi B, Shames I, Djenidi L, 'Microfluidic characteristics of a multiholed baffle plate microreactor', International Journal of Heat and Fluid Flow, 27 10691077 (2006) [C1]



2006 
Burattini P, Lavoie P, Agrawal A, Djenidi L, Antonia RA, 'Power law of decaying homogeneous isotropic turbulence at low Reynolds number.', Phys Rev E Stat Nonlin Soft Matter Phys, 73 066304 (2006)



2006 
Agrawal A, Djenidi L, Antonia RA, 'Investigation of flow around a pair of sidebyside square cylinders using the lattice Boltzmann method', Computers and Fluids, 35 10931107 (2006) [C1]



2006 
Leonardi S, Orlandi P, Djenidi L, Antonia RA, 'Guidelines for modeling a 2D rough wall channel flow', Flow Turbulence and Combustion, 77 4157 (2006) [C1]



2006 
Burattini P, Lavoie PLD, Agrawal A, Djenidi L, Antonia RA, 'Power law of decaying homogeneous isotropic turbulence at low Reynolds number', Physical Review E, 73 (2006) [C1]



2005 
Oyewola O, Djenidi L, Antonia RA, 'Spanwise vorticity measurements in a perturbed boundary layer', Experiments in Fluids, 39 152155 (2005) [C1]



2005 
Lavoie PLD, Burattini P, Djenidi L, Antonia RA, 'Effect of initial conditions on decaying grid turbulence at low Rgimel', Experiments in Fluids, 39 865874 (2005) [C1]



2005 
Agrawal A, Djenidi L, Antonia RA, 'Simulation of gas flow in microchannels with a sudden expansion or contraction', Journal of Fluid Mechanics, 530 135144 (2005) [C1]



2004 
Oyewola O, Djenidi L, Antonia RA, 'The response of a turbulent boundary layer to concentrated suction applied through a pair of porous wall strips', Journal of Fluids Engineereing, 126 888890 (2004) [C1]



2004 
Leonardi S, Orlandi P, Djenidi L, Antonia RA, 'Structure of turbulent channel flow with square bars on one wall', International Journal of Heat and Fluid Flow, 25 384392 (2004) [C1]



2004 
Oyewola O, Djenidi L, Antonia RA, 'Influence of localised wall suction on the anisotropy of the Reynolds stress tensor in a turbulent boundary layer', Experiments in Fluids, 37 187193 (2004) [C1]



2004 
Agrawal A, Djenidi L, Antonia RA, 'LIF based detection of lowspeed streaks', experiments in fluids, 36 600603 (2004) [C1]



2004 
Burattini P, Djenidi L, 'Velocity and passive scalar characteristics in a round jet with grids at the nozzle exit', Flow, Turbulence and Combustion, 72 199218 (2004) [C1]



2003 
Djenidi L, Antonia RA, Savill AM, 'A numerical study of drag reduction by minibelts in a smooth wall turbulent boundary layer', The Aeronautical Journal, Paper No.2728 (2003) [C1]



2003 
Leonardi S, Orlandi P, Smalley RJ, Djenidi L, Antonia RA, 'Direct numerical simulations of turbulent channel flow with transverse square bars on one wall', Journal of Fluid Mechanics, 491 229238 (2003) [C1]



2003 
Oyewola O, Djenidi L, Antonia RA, 'Combined influence of the Reynolds number and localised wall suction on a turbulent boundary layer', Experiments in Fluids, 35 199206 (2003) [C1]



2002 
Smalley RJ, Leonardi S, Antonia RA, Djenidi L, Orlandi P, 'Reynolds stress anistropy of turbulent rough wall layers', Experiments in Fluids, 33 3137 (2002) [C1]



2001 
Djenidi L, Antonia RA, 'Calculation of the effect of concentrated wall suction on a turbulent boundary layer using a secondorder moment closure', International Journal of Heat and Fluid Flow, 22 487494 (2001) [C1]



2001 
Rehab H, Antonia RA, Djenidi L, 'Steamwise evloution of a highSchmidtnumber passive scalar in a turbulent plane wake', Experiments in Fluids, 31 186192 (2001) [C1]



2001 
Smalley RJ, Antonia RA, Djenidi L, 'Selfpreservation of roughwall turbulent boundary layers', European Journal of Mechanics BFluids, 20 591602 (2001) [C1]



2000 
Rehab H, Antonia RA, Djenidi L, Mi J, 'Characteristics of fluorescein dye and temperature fluctuations in a turbulent nearwake', Experiments in Fluids, 28 462470 (2000) [C1]



1999 
Djenidi L, Elavarasan R, Antonia RA, 'The Turbulent Boundary Layer Over Transverse Square Cavities', Journal of Fluid Mechanics, 395 271294 (1999) [C1]



1998 
Djenidi L, Antonia RA, Hundseid J, Krogstad PA, 'Combined Effect of Wall Suction and Riblets on a Low R Turbulent Boundary Layer', The Aeronautical Journal, 102 5357 (1998) [C1]



1997 
Antonia RA, Djenidi L, 'Reynolds stress producing motions in smooth and rough wall boundary layers', Advances in Fluid Mechanics, 15 181199 (1997)
Motions that are responsible for the production and maintenance of the Reynolds shear stress in a turbulent boundary layer may be affected by the Reynolds number and the surface r... [more]
Motions that are responsible for the production and maintenance of the Reynolds shear stress in a turbulent boundary layer may be affected by the Reynolds number and the surface roughness. Evidence for each of these effects is presented, based mainly on experiments carried out in our laboratory. The effects are felt in both inner and outer regions of the layer. The evidence points to the nonuniversality of the active motion and to the sensitivity of the large scale motion to boundary conditions.



1997 
Djenidi L, Antonia RA, 'Modeling of the Reynolds stress transport equation', AIAA JOURNAL, 35 450455 (1997)



1997 
Dubief Y, Djenidi L, Antonia RA, 'The measurement of partial derivative u/partial derivative y in a turbulent boundary layer over a riblet surface', INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW, 18 183187 (1997)



1997 
Dubief Y, Djenidi L, Antonia RA, 'The measurement of u/ y in a turbulent boundary layer over a riblet surface', International Journal of Heat and Fluid Flow, 18 183187 (1997)
Statistics of ¿u/¿y have been measured in a turbulent boundary layer over either a smooth wall or a riblet surface using parallel hot wires. Over the riblets, the mean square valu... [more]
Statistics of ¿u/¿y have been measured in a turbulent boundary layer over either a smooth wall or a riblet surface using parallel hot wires. Over the riblets, the mean square value of ¿u/¿y (normalised with smooth wall variables) is smaller than over the smooth wall; the difference increases as the distance to the wall decreases. Also this difference is larger when the riblets operate in a dragaugmenting mode. These changes would reflect changes in the nearwall turbulence structure. Furthermore, on the basis that ¿u/¿y is a major contributor to the spanwise vorticity, the results indicate that, relative to the smooth wall, the mean square spanwise vorticity is reduced near a riblet surface. © 1997 by Elsevier Science Inc.



1997 
Djenidi L, Dubief Y, Antonia RA, 'Advantages of using a power law in a low R(theta) turbulent boundary layer', EXPERIMENTS IN FLUIDS, 22 348350 (1997)



1996 
Djenidi L, Antonia RA, 'Laser Doppler anemometer measurements of turbulent boundary layer over a riblet surface', AIAA JOURNAL, 34 10071012 (1996)



1995 
CHING CY, DJENIDI L, ANTONIA RA, 'LOWREYNOLDSNUMBER EFFECTS IN A TURBULENT BOUNDARYLAYER', EXPERIMENTS IN FLUIDS, 19 6168 (1995)



1994 
DJENIDI L, ANSELMET F, ANTONIA RA, 'LDA MEASUREMENTS IN A TURBULENT BOUNDARYLAYER OVER A DTYPE ROUGH WALL', EXPERIMENTS IN FLUIDS, 16 323329 (1994)



1994 
ANTONIA RA, DJENIDI L, SPALART PR, 'ANISOTROPY OF THE DISPERSION TENSOR IN A TURBULENT BOUNDARYLAYER', PHYSICS OF FLUIDS, 6 24752479 (1994)



1994 
Djenidi L, Anselmet F, Liandrat J, Fulachier L, 'Laminar boundary layer over riblets', Physics of Fluids, 6 29932999 (1994)
Laser doppler anemometry (LDA) measurements and numerical calculations have been made for a laminar boundary layer on triangular riblets. Calculated mean velocity distributions al... [more]
Laser doppler anemometry (LDA) measurements and numerical calculations have been made for a laminar boundary layer on triangular riblets. Calculated mean velocity distributions along the riblet contour are in good agreement with the measured ones. The results show that no transversal motion exists above and within the riblet valleys (e.g., no secondary motion). It is found that despite the large wetted area increase, the frictional drag is not increased on riblets relative to a smooth wall. This result suggests that the viscous effects are at play in the drag reduction for a turbulent boundary layer, in the sense that they compensate for the increase in wetted area. © 1994 American Institute of Physics.



1993 
DJENIDI L, ANTONIA RA, 'LDA MEASUREMENTS IN LOW REYNOLDSNUMBER TURBULENT BOUNDARYLAYER', EXPERIMENTS IN FLUIDS, 14 280288 (1993)



1991 
Liandrat J, Coustols E, Djenidi L, Anselmet F, de SaintVictor X, Fioc F, et al., 'Effect of riblets on either fully developed boundary layers or internal flows in laminar regime (1991)
The present paper summarizes the status of the numerical research carried out both at ONERA/CERT and IMST, as regards the efficiency of 'internal' manipulators, more com... [more]
The present paper summarizes the status of the numerical research carried out both at ONERA/CERT and IMST, as regards the efficiency of 'internal' manipulators, more commonly named by many researchers, 'riblets', in external as well as internal flows, under laminar conditions. First results obtained at CERT during preliminary studies are briefly recalled. From a numerical point of view, many difficulties arose; most of them stemmed from the singularity at the riblet edge. First of all, results issued from different grid refinements are presented. Then, emphasis is put on analogies and differences between manipulated fully developed internal and external flows in the presence of either V or Lshaped riblets; the latter corresponds in fact to half of a Ushaped groove. These theoretical studies showed that the wetted area increase did not induce extra skin friction in laminar boundary layers over V or Lshaped grooves. (A)



1991 
Liandrat J, Coustols E, Djenidi L, Anselmet F, de Saint Victor X, Fioc F, Fulachier L, 'Effect of riblets on either fully developed boundary layers or internal flows in laminar regime (1991)
The present paper summarizes the status of the numerical research carried out both at ONERA/CERT and IMST, as regards the efficiency of 'internal' manipulators, more com... [more]
The present paper summarizes the status of the numerical research carried out both at ONERA/CERT and IMST, as regards the efficiency of 'internal' manipulators, more commonly named by many researchers, 'riblets', in external as well as internal flows, under laminar conditions. First results obtained at CERT during preliminary studies are briefly recalled. From a numerical point of view, many difficulties arose; most of them stemmed from the singularity at the riblet edge. First of all, results issued from different grid refinements are presented. Then, emphasis is put on analogies and differences between manipulated fully developed internal and external flows in the presence of either V or Lshaped riblets; the latter corresponds in fact to half of a Ushaped groove. These theoretical studies showed that the wetted area increase did not induce extra skin friction in laminar boundary layers over V or Lshaped grooves. (A)



1989 
Djenidi L, Liandrat J, Anselmet F, Fulachier L, 'Numerical and experimental investigation of the laminar boundary layer over riblets', Applied Scientific Research, 46 263270 (1989)
One of the main aims of this work is to show to what extent drag reduction in a turbulent boundary layer can be ascribed to a purely viscous effect. A numerical and experimental s... [more]
One of the main aims of this work is to show to what extent drag reduction in a turbulent boundary layer can be ascribed to a purely viscous effect. A numerical and experimental study is performed in a laminar boundary layer over triangular riblets. The 2D parabolic equations of motion are integrated using an x marching method and the discretised system is solved with the MSI algorithm. The influence of the riblet geometrical parameters and of the number of grid points is studied. Measurements are carried out in a water tunnel with forward scatter and backscatter laserDoppler velocimetry extending within the riblets. The longitudinal velocity component measurements and computations are practically identical. Numerical results presented herein show that a slight drag reduction is obtained for s/h=1.2. It appears that, as far as friction is concerned, the wetted area is not the surface to be considered. Thus, the boundary layer over riblets would behave like a boundary layer on an equivalent smooth plate located beneath the crest plane. The numerical study in terms of the riblet height h shows best results are for h tending to zero, with the ratio s/h being equal to 1.2. © 1989 Kluwer Academic Publishers.


