Dr Nicholas Giannelis

Dr Nicholas Giannelis

Lecturer

School of Engineering

Career Summary

Biography

Nicholas Giannelis was born in Sydney, Australia and received his BE/BCom and PhD degrees from the University of Sydney in 2013 and 2019, respectively. In 2021, he was appointed as Lecturer in Aerospace Systems Engineering and the University of Newcastle, Australia. His research interests broadly spans aeroelasticity, computational aerodynamics, fluid-structure interaction, nonlinear dynamics and vibrations, with previous projects including:

  • Computational Aeroelasticity - Modelling of complex fluid flows (transonic shock buffet), approaching aerodynamics and structures from a systems perspective to assess the sensitivity of aeroelastic systems to changes in sub-system components and the development of data-driven methods for physics model extraction and stability analysis.
  • High-Fidelity Modelling of a Cavity Aeroacoustics - developing efficient simulation workflows for modelling complex aerodynamic flows and assessing the influence of large-scale pressure fluctuations on the structural response of immersed bodies.
  • Underwater Effector Parametric Modelling - developing parametric models of vehicle dynamics for the design of high-speed underwater vehicles.
  • Nonlinear Vibration Energy Harvesting - optimisation of nonlinear energy harvesters for application in Australian Defence rotorcraft considering the intersection of structural dynamics, materials science and electronics.

Qualifications

  • Doctor of Philosophy, University of Sydney
  • Bachelor of Commerce, University of Sydney
  • Bachelor of Engineering (Honours), University of Sydney

Keywords

  • Aeroelasticity
  • Compressible flows
  • Computational aerodynamics
  • Fluid-structure interaction
  • Nonlinear dynamics
  • Structural dynamics

Languages

  • English (Mother)
  • Greek (Fluent)

Fields of Research

Code Description Percentage
401201 Aerodynamics (excl. hypersonic aerodynamics) 40
401204 Computational methods in fluid flow, heat and mass transfer (incl. computational fluid dynamics) 30
401702 Dynamics, vibration and vibration control 30

Professional Experience

UON Appointment

Title Organisation / Department
Lecturer University of Newcastle
School of Engineering
Australia

Academic appointment

Dates Title Organisation / Department
1/6/2019 - 7/1/2021 Associate Lecturer The University of Sydney
School of Aeronautical, Mechanical and Mechatronic Engineering
Australia

Teaching

Code Course Role Duration
AERO2703 Aircraft Performance and Operations
The University of Sydney
This unit aimed to develop in students an understanding of the fundamental concepts involved in the operation and performance of aircraft, including: calculation of take-off, climb, cruise, turn, descent and landing performance; weight and balance calculations; understanding the use of aerodynamic derivatives and their impact on aircraft performance; mission specific optimisation; modern issues of airport congestion, noise restrictions, aviation certification requirements for the use of different aircraft categories and novel methods for solving these problems.
Lecturer 1/1/2019 - 31/12/2020
AERO1560 Introduction to Aerospace Engineering
The University of Sydney
This unit of study introduced students to the role of professional aerospace engineers, along with the development of fundamental engineering knowledge and skills for aerospace vehicle design, analysis performance and operation.
Lecturer 1/1/2019 - 31/12/2020
AERO3400 Aerospace Propulsion Systems
The University of Newcastle
Analysis and control of thrust generation mechanisms common in modern aerospace systems with a strong emphasis on testing and control of engines and developing an understanding of engine response to control and integration with other relevant aircraft systems.
Lecturer 11/1/2021 - 31/12/2030
AERO4560 AERO4560: Flight Mechanics 2
The University of Sydney
This unit aimed to develop an understanding of the application of flight mechanics principles in the control of modern aircraft systems. The material spanned: understanding of dynamic aircraft behaviour,;aircraft system identification; aircraft sensitivity to wind gusts; automatic flight control systems development and aircraft handling analysis.
Lecturer 1/1/2019 - 31/12/2020
Edit

Publications

For publications that are currently unpublished or in-press, details are shown in italics.

Highlighted Publications

Year Citation Altmetrics Link
2017 Giannelis NF, Vio GA, Levinski O, 'A review of recent developments in the understanding of transonic shock buffet', Progress in Aerospace Sciences, 92 39-84 (2017)

Within a narrow band of flight conditions in the transonic regime, interactions between shock-waves and intermittently separated shear layers result in large amplitude, self-susta... [more]

Within a narrow band of flight conditions in the transonic regime, interactions between shock-waves and intermittently separated shear layers result in large amplitude, self-sustained shock oscillations. This phenomenon, known as transonic shock buffet, limits the flight envelope and is detrimental to both platform handling quality and structural integrity. The severity of this instability has incited a plethora of research to ascertain an underlying physical mechanism, and yet, with over six decades of investigation, aspects of this complex phenomenon remain inexplicable. To promote continual progress in the understanding of transonic shock buffet, this review presents a consolidation of recent investigations in the field. The paper begins with a conspectus of the seminal literature on shock-induced separation and modes of shock oscillation. The currently prevailing theories for the governing physics of transonic shock buffet are then detailed. This is followed by an overview of computational studies exploring the phenomenon, where the results of simulation are shown to be highly sensitive to the specific numerical methods employed. Wind tunnel investigations on two-dimensional aerofoils at shock buffet conditions are then outlined and the importance of these experiments for the development of physical models stressed. Research considering dynamic structural interactions in the presence of shock buffet is also highlighted, with a particular emphasis on the emergence of a frequency synchronisation phenomenon. An overview of three-dimensional buffet is provided next, where investigations suggest the governing mechanism may differ significantly from that of two-dimensional sections. Subsequently, a number of buffet suppression technologies are described and their efficacy in mitigating shock oscillations is assessed. To conclude, recommendations for the direction of future research efforts are given.

DOI 10.1016/j.paerosci.2017.05.004
Citations Scopus - 72Web of Science - 49
2018 Dimitriadis G, Giannelis NF, Vio GA, 'A modal frequency-domain generalised force matrix for the unsteady Vortex Lattice method', Journal of Fluids and Structures, 76 216-228 (2018)

The unsteady Vortex Lattice method is becoming an increasingly popular aerodynamic modelling method for incompressible aeroelastic problems, such as flexible low-speed aircraft, w... [more]

The unsteady Vortex Lattice method is becoming an increasingly popular aerodynamic modelling method for incompressible aeroelastic problems, such as flexible low-speed aircraft, wind turbines and flapping flight. It leads to discrete time aeroelastic state space equations, which must be solved in a time-marching framework. Eigenvalue or singular value decompositions of the discrete time equations can be used in order to perform stability analysis but such procedures must be accompanied by model order reduction because the size of the equations is large. This work proposes a modal frequency domain implementation of the Vortex Lattice method, resulting in a modal generalised force matrix. Model order reduction is implicit in the modal approach and stability analysis can be carried out using industry-standard flutter analysis techniques, such as the p¿k method. The approach is validated by comparison to wind tunnel flutter data obtained from rectangular cantilever flat plate wings of different aspect ratios and sweep angles. It is found that the aeroelastic model predictions follow the experimental trends for both flutter speed and frequency but tend to be moderately conservative.

DOI 10.1016/j.jfluidstructs.2017.10.010
Citations Scopus - 13Web of Science - 8
2018 Giannelis NF, Levinski O, Vio GA, 'Influence of Mach number and angle of attack on the two-dimensional transonic buffet phenomenon', Aerospace Science and Technology, 78 89-101 (2018)

Within a narrow band of flight conditions in the transonic regime, self-sustained shock oscillations that involve the interaction between shock-waves and intermittently separated ... [more]

Within a narrow band of flight conditions in the transonic regime, self-sustained shock oscillations that involve the interaction between shock-waves and intermittently separated shear layers may develop. This phenomenon, known as transonic shock buffet, limits the flight envelope and is detrimental to both aircraft handling quality and structural integrity. In this investigation, numerical simulation of transonic shock buffet over the OAT15A aerofoil is performed to explore the buffet envelope. Unsteady Reynolds-Averaged Navier¿Stokes simulations are validated against available experimental data to ascertain the most effective combination of simulation parameters to reproduce autonomous shock oscillations. From the baseline test case, the influence of Mach number and angle of attack on the nature of the buffet response is investigated. Radial Basis Function surrogate models are developed to represent the variation of buffet amplitude and frequency with flight condition. While the frequency is found to increase monotonically with both parameters, variation in buffet amplitude through the region of shock unsteadiness is more complex, particularly at high angles of attack. This is related to a bifurcation in the behaviour of the shock. As incidence increases from onset, the shock dynamics transition from periodic oscillations over the suction surface to quasi-periodic motions, whereby the shock is propelled forward into the oncoming flow during its upstream excursion.

DOI 10.1016/j.ast.2018.03.045
Citations Scopus - 18Web of Science - 12

Journal article (7 outputs)

Year Citation Altmetrics Link
2020 Geoghegan JA, Giannelis NF, Vio GA, 'A numerical investigation of the geometric parametrisation of shock control bumps for transonic shock oscillation control', Fluids, 5 (2020)

At transonic flight conditions, shock oscillations on wing surfaces are known to occur and result in degraded aerodynamic performance and handling qualities. This is a purely flow... [more]

At transonic flight conditions, shock oscillations on wing surfaces are known to occur and result in degraded aerodynamic performance and handling qualities. This is a purely flow-driven phenomenon, known as transonic buffet, that causes limit cycle oscillations and may present itself within the operational flight envelope. Hence, there is significant research interest in the development of shock control techniques to either stabilise the unsteady flow or raise the boundary onset. This paper explores the efficacy of dynamically activated contour-based shock control bumps within the buffet envelope of the OAT15A aerofoil on transonic flow control numerically through unsteady Reynolds-averaged Navier-Stokes modelling. A parametric evaluation of the geometric variables that define the Hicks-Henne-derived shock control bump will show that bumps of this type lead to a large design space of applicable shapes for buffet suppression. Assessment of the flow field, local to the deployed shock control bump geometries, reveals that control is achieved through a weakening of the rear shock leg, combined with the formation of dual re-circulatory cells within the separated shear-layer. Within this design space, favourable aerodynamic performance can also be achieved. The off-design performance of two optimal shock control bump configurations is explored over the buffet region for M = 0.73, where the designs demonstrate the ability to suppress shock oscillations deep into the buffet envelope.

DOI 10.3390/fluids5020046
Citations Scopus - 2
2020 Giannelis NF, Levinski O, Vio GA, 'Origins of atypical shock buffet motions on a supercritical aerofoil', AEROSPACE SCIENCE AND TECHNOLOGY, 107 (2020)
DOI 10.1016/j.ast.2020.106304
Citations Scopus - 1Web of Science - 1
2018 Dimitriadis G, Giannelis NF, Vio GA, 'A modal frequency-domain generalised force matrix for the unsteady Vortex Lattice method', Journal of Fluids and Structures, 76 216-228 (2018)

The unsteady Vortex Lattice method is becoming an increasingly popular aerodynamic modelling method for incompressible aeroelastic problems, such as flexible low-speed aircraft, w... [more]

The unsteady Vortex Lattice method is becoming an increasingly popular aerodynamic modelling method for incompressible aeroelastic problems, such as flexible low-speed aircraft, wind turbines and flapping flight. It leads to discrete time aeroelastic state space equations, which must be solved in a time-marching framework. Eigenvalue or singular value decompositions of the discrete time equations can be used in order to perform stability analysis but such procedures must be accompanied by model order reduction because the size of the equations is large. This work proposes a modal frequency domain implementation of the Vortex Lattice method, resulting in a modal generalised force matrix. Model order reduction is implicit in the modal approach and stability analysis can be carried out using industry-standard flutter analysis techniques, such as the p¿k method. The approach is validated by comparison to wind tunnel flutter data obtained from rectangular cantilever flat plate wings of different aspect ratios and sweep angles. It is found that the aeroelastic model predictions follow the experimental trends for both flutter speed and frequency but tend to be moderately conservative.

DOI 10.1016/j.jfluidstructs.2017.10.010
Citations Scopus - 13Web of Science - 8
2018 Giannelis NF, Levinski O, Vio GA, 'Influence of Mach number and angle of attack on the two-dimensional transonic buffet phenomenon', Aerospace Science and Technology, 78 89-101 (2018)

Within a narrow band of flight conditions in the transonic regime, self-sustained shock oscillations that involve the interaction between shock-waves and intermittently separated ... [more]

Within a narrow band of flight conditions in the transonic regime, self-sustained shock oscillations that involve the interaction between shock-waves and intermittently separated shear layers may develop. This phenomenon, known as transonic shock buffet, limits the flight envelope and is detrimental to both aircraft handling quality and structural integrity. In this investigation, numerical simulation of transonic shock buffet over the OAT15A aerofoil is performed to explore the buffet envelope. Unsteady Reynolds-Averaged Navier¿Stokes simulations are validated against available experimental data to ascertain the most effective combination of simulation parameters to reproduce autonomous shock oscillations. From the baseline test case, the influence of Mach number and angle of attack on the nature of the buffet response is investigated. Radial Basis Function surrogate models are developed to represent the variation of buffet amplitude and frequency with flight condition. While the frequency is found to increase monotonically with both parameters, variation in buffet amplitude through the region of shock unsteadiness is more complex, particularly at high angles of attack. This is related to a bifurcation in the behaviour of the shock. As incidence increases from onset, the shock dynamics transition from periodic oscillations over the suction surface to quasi-periodic motions, whereby the shock is propelled forward into the oncoming flow during its upstream excursion.

DOI 10.1016/j.ast.2018.03.045
Citations Scopus - 18Web of Science - 12
2018 Levy JC, Giannelis NF, Thornber B, Vio GA, 'Stratospheric drogue instability analysis', Journal of Aircraft, 55 2524-2529 (2018)
DOI 10.2514/1.C034796
2017 Giannelis NF, Vio GA, Levinski O, 'A review of recent developments in the understanding of transonic shock buffet', Progress in Aerospace Sciences, 92 39-84 (2017)

Within a narrow band of flight conditions in the transonic regime, interactions between shock-waves and intermittently separated shear layers result in large amplitude, self-susta... [more]

Within a narrow band of flight conditions in the transonic regime, interactions between shock-waves and intermittently separated shear layers result in large amplitude, self-sustained shock oscillations. This phenomenon, known as transonic shock buffet, limits the flight envelope and is detrimental to both platform handling quality and structural integrity. The severity of this instability has incited a plethora of research to ascertain an underlying physical mechanism, and yet, with over six decades of investigation, aspects of this complex phenomenon remain inexplicable. To promote continual progress in the understanding of transonic shock buffet, this review presents a consolidation of recent investigations in the field. The paper begins with a conspectus of the seminal literature on shock-induced separation and modes of shock oscillation. The currently prevailing theories for the governing physics of transonic shock buffet are then detailed. This is followed by an overview of computational studies exploring the phenomenon, where the results of simulation are shown to be highly sensitive to the specific numerical methods employed. Wind tunnel investigations on two-dimensional aerofoils at shock buffet conditions are then outlined and the importance of these experiments for the development of physical models stressed. Research considering dynamic structural interactions in the presence of shock buffet is also highlighted, with a particular emphasis on the emergence of a frequency synchronisation phenomenon. An overview of three-dimensional buffet is provided next, where investigations suggest the governing mechanism may differ significantly from that of two-dimensional sections. Subsequently, a number of buffet suppression technologies are described and their efficacy in mitigating shock oscillations is assessed. To conclude, recommendations for the direction of future research efforts are given.

DOI 10.1016/j.paerosci.2017.05.004
Citations Scopus - 72Web of Science - 49
2014 Giannelis NF, Vio GA, Verstraete D, Steelant J, 'Temperature effect on the structural design of a mach 8 vehicle', Applied Mechanics and Materials, 553 249-254 (2014)

Hypersonic aircraft design is a pressing area of research. The motivation to create aircraft that can cross the globe in only a few hours is driving this forward but there are a n... [more]

Hypersonic aircraft design is a pressing area of research. The motivation to create aircraft that can cross the globe in only a few hours is driving this forward but there are a number of challenges that need to be overcome. One of the principle challenges is the effect that temperature has on the structure. Temperature changes cause heating of the structure as well as changing the material properties of the affected structure. This has a compound effect in that the structures gets geometrically deformed, stiffness is reduced, and this will have an impact on the aerodynamic and structural performance of the vehicle. This article investigates the effect of two different structural concepts: a conventional rib-spar configuration and a pillow tank. A number of different structural options in terms of number of ribs / spars will be investigated. The structure will be optimised based on critical loading conditions. Results for various temperature distributions will be investigated, while looking at change on structural strength, in-flight static deformation and dynamic response. © (2014) Trans Tech Publications, Switzerland.

DOI 10.4028/www.scientific.net/AMM.553.249
Show 4 more journal articles

Conference (21 outputs)

Year Citation Altmetrics Link
2021 Hamilton-Smith COL, Vio GA, Murray AJ, Thornber B, Giannelis NF, 'Simulation of low speed cavity flow with complex geometry', AIAA Scitech 2021 Forum (2021)

Modelling of noise and pressure fluctuations from the flow over a cavity is of critical importance to the understanding of loads within the cavity to ultimately allow for accurate... [more]

Modelling of noise and pressure fluctuations from the flow over a cavity is of critical importance to the understanding of loads within the cavity to ultimately allow for accurate fatigue life prediction of bodies subjected to such flows. The length to depth (L/D) ratio is a critical parameter in determining key flow characteristics. This paper details a computational study to model low-speed cavity flow for complex geometries. Two base cavities will be used, with L/D = 0.5 and L/D = 1. In addition to these clean cavities, a half-closed configuration and a geometry comprised of a curved upstream ramp will also be studied. All computations will are performed at standard ground atmospheric conditions with a freestream airspeed of 60 m/s. The Computational Fluid Dynamics simulations conducted in this study are performed using an explicit, massively parallel, fully compressible structured multi-block Large Eddy Simulation flow solver. The effects of the complex geometries are compared against the clean cavity by observing the variations in the root-mean square and mean pressure coefficients, along velocity field flow visualisations. Conclusions will be drawn as to the effect of the different geometries.

2020 Geoghegan JA, Giannelis NF, Vio GA, 'Parametric study of active shock control bumps for transonic shock buffet alleviation', AIAA Scitech 2020 Forum (2020)

A numerical investigation into the efficacy of surface deformed activated shock control bumps (SCBs) for the purpose of transonic shock-buffet alleviation has been carried out. Th... [more]

A numerical investigation into the efficacy of surface deformed activated shock control bumps (SCBs) for the purpose of transonic shock-buffet alleviation has been carried out. The geometry of the bump is derived from a Hicks-Henne shape-function which guarantees smoothness and surface continuity such that shape does not produce surface discontinuities. Simulations were performed on the OAT15A at M8 = 0.73 and a = 3.5, with a symmetric SCB at various positions relative to the mean shock position and at maximum positive/negative deflections. The symmetric SCB placed within xs /c = -0.05 to 0.1 was able to completely stabilise the transonic shock motion and also demonstrated the ability to control the resulting steady-state lift coefficient. The performance of the tested geometries are evaluated at different ramp speeds, which showed that only the transient lift coefficient is impacted, as a steady-state was still achieved. Further the SCB presented in this paper demonstrated the ability to switch between equilibrium states, or recover the original flow field, through actuation. The efficacy of this type of SCB is based on the resulting aerofoil upper surface curvature post-deployment, which suggests that it is possible to tailor the aerofoil surface to mitigate buffet with the application to an adaptive wing.

DOI 10.2514/6.2020-1989
Citations Scopus - 3
2020 Munk DJ, Dooner D, Best F, Vio GA, Giannelis NF, Murray AJ, Dimitriadis G, 'Limit cycle oscillations of cantilever rectangular wings designed using topology optimisation', AIAA Scitech 2020 Forum (2020)

A closed form state-space model for the nonlinear aeroelastic response of thin cantilevered flat plates is derived using a combination of von Kármán thin plate theory and a linear... [more]

A closed form state-space model for the nonlinear aeroelastic response of thin cantilevered flat plates is derived using a combination of von Kármán thin plate theory and a linearized continuous time vortex lattice aerodynamic model. The modal-based model is solved for the amplitude and period of the limit cycles of the flat plates using numerical continuation. The resulting predictions are compared to experimental data obtained from identical flat plates in the wind tunnel. Both conventional and topologically optimised flat rectangular plates are investigated. It is shown that the aeroelastic model predicts the linear flutter conditions and nonlinear response of the plates with reasonable accuracy, although the predicted limit cycle amplitude variation with airspeed is different to the one measured experimentally due to unmodelled physics.

DOI 10.2514/6.2020-1907
Citations Scopus - 2
2020 Murray A, Giannelis N, Vio GA, 'Catastrophe theoretic modelling of hysteresis in transonic shock buffet', AIAA Scitech 2020 Forum (2020)

Given particular flow conditions within the transonic flow regime, undesirable dynamic lift and pitch profiles are produced due to the emergence of self sustaining oscillating sho... [more]

Given particular flow conditions within the transonic flow regime, undesirable dynamic lift and pitch profiles are produced due to the emergence of self sustaining oscillating shock waves known as shock buffet. Shock buffet onset has been observed to exhibit hysteresis with changes in angle of attack both experimentally and numerically. Here we model this hysteresis in the onset phase by way of catastrophe theory, a sub-branch of bifurcation theory in which bifurcations are studied using the geometry of a sufficiently smooth Lyapanov function. Numerical simulations are conducted for 2D flow over a thin aerofoil in the transonic regime and the nominal buffet response is discussed. The hysteresis behaviour is modelled using a cusp-catastrophic model of the interactions between Mach number, angle of attack, and lift coefficient, with buffet onset determined to be when the lift coefficient becomes oscillatory. The hysteresis boundary and cusp (bifurcation) points of the cusp-catastrophic model is then fit using a subset of the numerical data (including the cusp point) as a training set. The remaining numerical data is compared to the model predictions for the hysteresis boundary, both interior and exterior to the training set. The model is found to agree with numerical results within 3%. Future work will include investigating a dual cusp treatment for entry/exit into the buffet regime, expansion of the model to describe additional aspects of the buffet phenomenon, and the applicability of the model in the three dimensional case, which has clear importance for transonic applications.

DOI 10.2514/6.2020-1987
2020 Giannelis NF, Vio GA, 'A modal approach to shock buffet lock-in analysis', PROCEEDINGS OF INTERNATIONAL CONFERENCE ON NOISE AND VIBRATION ENGINEERING (ISMA2020) / INTERNATIONAL CONFERENCE ON UNCERTAINTY IN STRUCTURAL DYNAMICS (USD2020), Leuven, BELGIUM (2020)
2019 Giannelis NF, Murray AJ, Vio GA, 'Application of the hilbert-huang transform in the identification of frequency synchronisation in transonic aeroelastic systems', AIAA Scitech 2019 Forum (2019)

For a narrow range of flight conditions in the transonic regime, complex interactions between shock-waves and intermittently separated shear layers result in large amplitude, auto... [more]

For a narrow range of flight conditions in the transonic regime, complex interactions between shock-waves and intermittently separated shear layers result in large amplitude, autonomous shock oscillations. When this transonic buffet instability interacts with a forced or freely oscillating structure, frequency lock-in between the aerodynamic and structural modes can occur, yielding large amplitude limit cycle oscillations. In this study, the lock-in phenomenon is investigated by means of Reynolds-Averaged Navier-Stokes simulations. Single degree-of-freedom elastically-suspended pitching simulations are performed for the supercriti-cal OAT15A aerofoil section. The aeroelastic system is found to exhibit lock-in for pitch natural frequencies exceeding the buffet frequency and an increase in mass ratio is shown to narrow the extent of the lock-in region. Through application of the Hilbert-Huang transform, the aeroelas-tic response of an aerofoil at shock buffet conditions has been decomposed into its aerodynamic and structural components. From this, lock-in has been shown to be a single degree-of-freedom flutter type instability, characterised by an unstable structural mode, supporting the findings of previous studies conducted for the NACA 0012.

DOI 10.2514/6.2019-1341
Citations Scopus - 7
2019 Giannelis NF, Murray AJ, Vio GA, 'Influence of control surface deflections on a thin aerofoil at transonic buffet conditions', AIAA Scitech 2019 Forum (2019)

Although transonic shock buffet has been an issue restricting aircraft performance for decades, a robust means of control remains elusive. Additionally, the majority of literature... [more]

Although transonic shock buffet has been an issue restricting aircraft performance for decades, a robust means of control remains elusive. Additionally, the majority of literature in the field is concerned with thick, supercritical profiles, with limited research available on thinner aerofoils. In this study, the influence of both static and dynamic control surface deflections on the buffet response of the thin NACA 64A204 aerofoil is investigated. Static trailing edge control surface deflections are found to be beneficial in extending the buffet-free flight envelope by increasing the mean lift coefficient at onset. Small amplitude static leading edge slat deflections are found to have a marginal influence on the buffet response, whereas large slat deflections produce an abrupt loss in mean lift due to a shift in the sonic region aft of the slat hinge line. Forced harmonic excitation of both the trailing edge and leading edge control surfaces may induce lock-in of the aerodynamic response to the structural excitation at sufficient driving amplitudes. Depending on the ratio of excitation frequency to the frequency of shock oscillation, the aerodynamic response may be significantly amplified (at driving frequencies below the buffet) or attenuated (at driving frequencies above the buffet).

DOI 10.2514/6.2019-1339
Citations Scopus - 2
2018 Geoghegan JA, Giannelis NF, Vio GA, 'A numerical study on transonic shock buffet alleviation through oscillating shock control bumps', AIAA Aerospace Sciences Meeting, 2018 (2018)

Shock Control Bumps (SCBs) have been used extensively as a method of flow control in minimising transonic wave drag. Recent literature has suggested the potential for this method ... [more]

Shock Control Bumps (SCBs) have been used extensively as a method of flow control in minimising transonic wave drag. Recent literature has suggested the potential for this method of control to be used in transonic shock buffet alleviation, as well as the possibility of actuated flexible surfaces to generate geometrically smooth 2D bump profiles. The present paper provides a numerical investigation into the application of a Gaussian-based oscillating SCB at two positions along the OAT15A aerofoil developed by ONERA. An analysis of the geometric constraints as well as driving frequency are obtained from time-resolved URANS simulations with the intention of revealing a configuration within the tested design space to minimise shock effects, in addition to developing an understanding of the relationships between time-varying SCB design with buffet behaviour. To this effect, bump stream-wise position, amplitude and driving frequency are analysed with respect to the lift differential, mean lift offset and unsteady pressures. The analysis has suggested that time-varying SCBs placed at the clean aerofoil mean shock location, greatly reduce the peak to peak loading with minimal deviation from the design flight condition. Further it is observed that lock-in occurs over the entire tested frequency range with the shock oscillation and the SCB, proving the potential to control the shock frequency, with mitigate buffet loading.

DOI 10.2514/6.2018-1787
Citations Scopus - 2
2018 Giannelis NF, Vio GA, 'On the effect of control surface deflections on the aeroelastic response of an aerofoil at transonic buffet conditions', Proceedings of ISMA 2018 - International Conference on Noise and Vibration Engineering and USD 2018 - International Conference on Uncertainty in Structural Dynamics (2018)

At certain conditions in the transonic flight regime, interactions between oscillating shock waves and a forced or freely oscillating structure may incite frequency lock-in betwee... [more]

At certain conditions in the transonic flight regime, interactions between oscillating shock waves and a forced or freely oscillating structure may incite frequency lock-in between the aerodynamic and structural modes, resulting in large amplitude limit cycle oscillations. This study investigates the influence of both static and dynamic control surface deflections on this aerodynamic instability. A static trailing edge flap deflection is found to reduce the buffet onset incidence, while simultaneously increasing the mean lift coefficient. This is advantageous for extending the flight envelope. Static leading edge deflections are less promising, reducing the mean lift at buffet onset. Forced harmonic excitation of the trailing edge flap induces synchronisation of the buffet response with the control surface motion. With large amplitude deflections, at driving frequencies above the buffet, the root mean square buffet loads are significantly attenuated. This, however, does not extend to an elastically-suspended aerofoil, where harmonic flap excitation exacerbates the buffet response.

Citations Scopus - 4
2018 Huang H, Giannelis N, Geoghegan J, Vio GA, Thornber B, Giacobello M, Lam S, 'Numerical investigation of wall effects on shock-induced oscillation', Proceedings of the 21st Australasian Fluid Mechanics Conference, AFMC 2018 (2018)

A numerical study on the wall effects of the DST Group Transonic Wind Tunnel on self-sustained shock-induced oscillation was conducted using computational fluid dynamics. The test... [more]

A numerical study on the wall effects of the DST Group Transonic Wind Tunnel on self-sustained shock-induced oscillation was conducted using computational fluid dynamics. The test article was a NACA0012 aerofoil. Volume blockage effects were investigated by a parameter sweep of the chord length, and wall boundary effects were investigated by varying the porous wall inertial loss coefficient. The aerofoil mean and root-mean-square surface pressure was found to be relatively insensitive to the inertial loss coefficient, while a non-linear relationship to the chord length was observed.

2017 Doughney TF, Moss SD, Blunt D, Becker A, Wang W, Giannelis N, Vio G, 'Design considerations for a PIN-PMN-PT relaxor ferroelectric based vibration energy harvester for use on a helicopter main-transmission', 9th Australasian Congress on Applied Mechanics, ACAM 2017 (2017)

High frequency vibration energy harvesting is being investigated as a potential power source for the Prognostic Health Monitoring (PHM) of helicopter transmissions. Potentially, t... [more]

High frequency vibration energy harvesting is being investigated as a potential power source for the Prognostic Health Monitoring (PHM) of helicopter transmissions. Potentially, the use of vibration energy harvesting will reduce the requirement for power cabling or batteries for PHM applications. Gear meshing frequencies in the range of kilo-Hertz are found within helicopter main transmissions, and the meshing frequencies are often accompanied by large regular periodic vibrations present on the casing of the transmission. The prototype harvester described in this paper uses a relaxor ferroelectric single crystal ([011] cut PIN-PMN-PT) for mechanical to electrical transduction. This relaxor ferroelectric was chosen because of its giant piezoelectric charge constant of 1200 pC/N which is significantly greater than that of traditional sintered piezoceramics (e.g. PZT). The prototype harvester described in this paper was designed for harvesting from the vibrations present in a Bell206B Kiowa main-transmission. Kiowa main-transmission vibrations include periodic accelerations with amplitudes of up to 12 g (where g = 9.8 m/s2), and contain a major frequency component centred at around 1900 Hz corresponding to the input pinion meshing frequency. To ensure successful harvesting operation near 1900 Hz the mechanical energy transfer behaviour of the adhesive used to manufacture the prototype harvester (CB359) was investigated and found suitable for use at both room temperature and the elevated temperatures expected in the main-transmission environment. The mechanical quality factor (Qm) and natural frequency (fn) of the prototype harvester were measured under short circuit conditions and found to be ~20 and 1570 Hz respectively. The harvester response to (i) a 30-3000 Hz broadband excitation and (ii) an acceleration-magnitude scaled time-history derived from actual Kiowa main-transmission accelerations were measured over a range of resistive loads. The harvester response at the frequency of interest of 1900 Hz was 4.13 µW/g.

2017 Giannelis NF, Vio GA, 'Investigation of frequency lock-in phenomena on a supercritical aerofoil in the presence of transonic shock oscillations', 17th International Forum on Aeroelasticity and Structural Dynamics, IFASD 2017 (2017)

Within a narrow band of the transonic flight regime, shock-wave/boundary layer interactions yield large amplitude, self-sustained shock oscillations. When this transonic buffet in... [more]

Within a narrow band of the transonic flight regime, shock-wave/boundary layer interactions yield large amplitude, self-sustained shock oscillations. When this transonic buffet instability interacts with a forced or freely oscillating structure, frequency lock-in between the aerodynamic and structural modes can occur, resulting in large amplitude limit cycle oscillations of the structure. In this study, the lock-in phenomenon is investigated by means of Reynolds-Averaged Navier-Stokes simulations. Harmonically driven pitching simulations are performed for a range of driving frequencies and amplitudes for the supercritical OAT15A aerofoil section. The results show that for a band of driving frequencies near the buffet, frequency synchronisation develops for sufficient driving amplitudes. The flow topology within the lock-in regions differs for driving frequencies above and below the buffet. This is attributed to a phase reversal of the aerodynamic coefficients as the excitation frequency passes through the fundamental flow frequency. Analysis of the gain and phase relationships of the aerodynamic coefficients supports the findings of prior studies, where the lock-in phenomenon is related to bounded single degree-of-freedom flutter.

Citations Scopus - 13
2017 Munk DJ, Vio GA, Giannelis NF, Cooper JE, 'Topology optimisation of representative aircraft wing geometries with an experimental validation', 17th International Forum on Aeroelasticity and Structural Dynamics, IFASD 2017 (2017)

Increasingly aircraft are being designed to be more environmentally friendly and fuel efficient, as defined by the 2020-Vision and Flight-Path EU initiatives. This entails a reduc... [more]

Increasingly aircraft are being designed to be more environmentally friendly and fuel efficient, as defined by the 2020-Vision and Flight-Path EU initiatives. This entails a reduction in aircraft weight while still maintaining all the other constraints. The conventional, semi-monocoque, aircraft design has not changed for the past 50 years. Recently, developments in aircraft design has mainly come from the use of novel materials. A technique has recently been proposed, whereby topology optimisation is used, to determine the material distribution of simple flat plate wings for improved flutter characteristics. It was found that by modifying eigenmode shapes and separating the static natural frequencies the flutter velocity of the simple models could be improved. However, topology optimisation of continuum structures for dynamic stability is, thus far, limited to relatively small design problems. Therefore, this study has two aims. Firstly, it is to extend the method to representative aircraft wing structures and secondly to verify the theoretical results by experiment.

Citations Scopus - 2
2017 Giannelis N, Vio GA, Dimitriadis G, 'Limit cycle oscillations of cantilever rectangular flat plates in a wind tunnel', 17th International Forum on Aeroelasticity and Structural Dynamics, IFASD 2017 (2017)

A closed form state-space model of the nonlinear aeroelastic response of thin cantilevered flat plates is derived using a combination of Von Kármán thin plate theory and a lineari... [more]

A closed form state-space model of the nonlinear aeroelastic response of thin cantilevered flat plates is derived using a combination of Von Kármán thin plate theory and a linearized continuous time vortex lattice aerodynamic model. The modal-based model is solved for the amplitude and period of the limit cycles of the flat plates using numerical continuation. The resulting predictions are compared to experimental data obtained from identical flat plates in the wind tunnel. It is shown that the aeroelastic model predicts the linear flutter conditions and nonlinear response of the plates with reasonable accuracy, although the predicted limit cycle amplitude variation with airspeed is different to the one measured experimentally due to unmodelled physics.

2016 Giannelis NF, Vio GA, 'Aeroelastic interactions of a supercritical aerofoil in the presence of transonic shock buffet', 54th AIAA Aerospace Sciences Meeting (2016)

Within a small region of flight conditions in a transonic flow, shock-wave/boundary-layer interactions give rise to large amplitude, self-sustained shock oscillations that are det... [more]

Within a small region of flight conditions in a transonic flow, shock-wave/boundary-layer interactions give rise to large amplitude, self-sustained shock oscillations that are detrimental to both platform handling quality and structural fatigue life. In this study, the aeroelastic interactions between this transonic buffet instability and a spring suspended supercritical aerofoil are investigated by means of Reynolds-averaged Navier-Stokes simulation. The computational method is validated against static aerofoil data, from which single degree-of-freedom pitching and heaving simulations are performed for a range of sectional mass ratios. The results show that with a decrease in mass ratio, the structural and aerodynamic responses are amplified. This amplification is particularly pertinent to the pitching aerofoil at low sectional masses, where bifurcation in the aeroelastic system yields a topological change in buffeting flow field. Additionally, with structural eigenfrequencies in close proximity to the frequency of shock oscillation, sychronisation of the buffeting and structural modes occurs. This so called lock-in phenomenon has been previously identified and provides a mechanism for Limit Cycle Oscillations in aircraft structures. From this study, it is suggested that in a spring suspended aerofoil system, the onset of such lock- in phenomena is not heavily influenced by the sectional mass ratio, but rather, critically dependent on the relative structural and aerodynamic frequencies. The authors would like to thank Dr Robert Carrese from RMIT University and Dr Oleg Levinksi from the Defence Science and Technology Group Australia for their comprehensive insight into transonic buffet phenomenon, and for providing the preliminary test cases from which the present work was developed. This research was partially funded by the Defence Science and Technology Group.

Citations Scopus - 10
2016 Giannelis NF, Vio GA, Dimitriadis G, 'Dynamic interactions of a supercritical aerofoil in the presence of transonic shock buffet', Proceedings of ISMA 2016 - International Conference on Noise and Vibration Engineering and USD2016 - International Conference on Uncertainty in Structural Dynamics (2016)

Within a narrow transonic flight region, shock-wave/boundary-layer interactions yield large amplitude, selfsustained shock oscillations that are detrimental to both platform handl... [more]

Within a narrow transonic flight region, shock-wave/boundary-layer interactions yield large amplitude, selfsustained shock oscillations that are detrimental to both platform handling quality and structural integrity. In this study, the aeroelastic interactions between this transonic buffet instability and a spring-suspended supercritical aerofoil are investigated by means of Reynolds-Averaged Navier-Stokes simulations. Single degree-of-freedom pitching simulations are performed for a range of structural to aerodynamic frequency ratios, sectional mass ratios and levels of structural damping. The results show that for a range of pitch eigenfrequencies above the fundamental buffet frequency, sychronisation of the aerodynamic and structural modes occurs. This so called lock-in phenomenon acts as a mechanism for large amplitude Limit Cycle Oscillation in aircraft structures within the transonic flow regime. The sectional mass and the addition of structural damping are both found to have a pronounced effect on the nature of the limit cycles.

Citations Scopus - 10
2016 Munk DJ, Giannelis NF, Vio GA, 'Experimental validation of structures optimised for frequency constraints and dynamic loading', 57th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference (2016)

The optimum design of structures with frequency constraints is of great importance in the aeronautical industry. In order to avoid severe vibration, it is necessary to shift the f... [more]

The optimum design of structures with frequency constraints is of great importance in the aeronautical industry. In order to avoid severe vibration, it is necessary to shift the fundamental frequency of the structure away from the frequency range of any applied dynamic loading. Furthermore, structures with a high fundamental frequency result in a stiff design which is good for static loads. In the literature there are several techniques: SIMP, ESO, genetic algorithms, to name just a few that have been applied to this problem. However, there has been no experimental confirmation to show these solutions reflect reality. Unlike compliance minimisation, where analytical solutions exist for a specific range of problems, there are no concrete test cases. Furthermore, these analytical solutions use finite element methods that do not consider imperfections in the model/material present in reality. In this paper an experimental validation is given for structures that have been optimised for frequency maximisation and separation. The experimental results are compared with analytical solutions to quantify the effect of uncertainties in the model. It is shown that the experimental results validate the numerical results, where simplified plate wing models are compared, along with a wing box for industry application.

DOI 10.2514/6.2016-0941
2016 Cheema P, Vio G, Giannelis NF, 'Experimental validation of polynomial chaos theory on an aircraft T-tail', 18th AIAA Non-Deterministic Approaches Conference (2016)

Uncertainty quantification (UQ) is a notion which has received much interest over the past decade. It involves the extraction of statistical information from a problem with inhere... [more]

Uncertainty quantification (UQ) is a notion which has received much interest over the past decade. It involves the extraction of statistical information from a problem with inherent variability, where this variability may stem from a lack of model knowledge or through observational uncertainty. Traditionally, UQ has been a challenging pursuit owing to the lack of efficient methods available. The archetypal UQ method is Monte Carlo theory, however this method possesses a slow convergence rate and is therefore a computational burden. In contrast to Monte Carlo theory, polynomial chaos theory aims to spectrally expand the modelled uncertainty via polynomials of random variables which have deterministic coefficients. Once the spectral expansion has been fully defined, it is possible to obtain statistical properties using simple integration procedures. Although literature has proven polynomial chaos theory to be more efficient than Monte Carlo theory in several contexts, there has been very little effort to experimentally validate polynomial chaos theory. Hence, it is the aim of this paper to perform an experimental validation on an in-house physical T-Tail structure by analysing the first six vibrational modes of this structure, and comparing these against the predicted uncertainty bounds of polynomial chaos theory.

DOI 10.2514/6.2016-0953
Citations Scopus - 8
2016 Giannelis NF, Geoghegan JA, Vio GA, 'Gust response of a supercritical aerofoil in the vicinity of transonic shock buffet', Proceedings of the 20th Australasian Fluid Mechanics Conference, AFMC 2016 (2016)

Within a narrow region of the transonic flight regime, shock-wave/boundary layer interactions yield large amplitude, self-sustained shock oscillations that are detrimental to both... [more]

Within a narrow region of the transonic flight regime, shock-wave/boundary layer interactions yield large amplitude, self-sustained shock oscillations that are detrimental to both platform handling quality and structural integrity. In this study, the aeroelastic interactions between this transonic buffet instability and a spring-suspended aerofoil are investigated by means of Reynolds-Averaged Navier-Stokes simulations. Two degree-of-freedom simulations of a supercritical aerofoil subject to a discrete gust excitation are performed at a flow state in the vicinity of the buffet instability boundary. The results show that for a small perturbation in heave, the system crosses the instability boundary and the aerodynamic and heave modes synchronise with the pitch mode. This so-called lock-in phenomenon acts a mechanism for large amplitude Limit Cycle Oscillation in aircraft structures within the transonic flow regime.

Citations Scopus - 9
2015 Giannelis NF, Vio GA, 'Computational benchmark of commercial fluid-structure interaction software for aeroelastic applications', International Forum on Aeroelasticity and Structural Dynamics, IFASD 2015 (2015)

Advances in the field of fluid-structure interaction are improving the feasibility of fully coupled Computational Fluid Dynamics (CFD)/Computational Structural Mechanics (CSM) sol... [more]

Advances in the field of fluid-structure interaction are improving the feasibility of fully coupled Computational Fluid Dynamics (CFD)/Computational Structural Mechanics (CSM) solutions in large scale aeroelastic problems. With such emerging technologies, validation of developed codes and software packages is imperative to ensure accurate and robust solution schemes. In this paper two fluid-structure interaction benchmark cases, the Turek-Hron channel flow and AGARD 445.6 weakened wing, are investigated using the ANSYS software suite with Multiphysics capabilities. An implicit, sub-iterative coupling scheme is adopted, with under-relaxation of the fluid load transfer to achieve tightly coupled solutions. Results obtained from the Turek-Hron test case indicate the individual structural and fluid solvers convey excellent agreement with the benchmark solution. The ANSYS System Coupling workflow is also found to effectively address large grid deformations in the Turek-Hron case and captures the majority of the AGARD flutter boundary well. Discrepancies are however found in addressing added-mass effects in the Turek-Hron benchmark. As these effects are not prevalent in flows of aeronautic significance, the ANSYS System Coupling package is found to be effective in addressing aeroelastic fluid-structure interaction problems.

Citations Scopus - 1
2015 Giannelis NF, Vio GA, 'Bifurcation analysis of the aeroelastic galloping problem via input-output parametric modelling', International Forum on Aeroelasticity and Structural Dynamics, IFASD 2015 (2015)

This paper explores the bifurcation behaviour of the aeroelastic galloping system through an input-output parametric modelling. The models are trained with periodic output data an... [more]

This paper explores the bifurcation behaviour of the aeroelastic galloping system through an input-output parametric modelling. The models are trained with periodic output data and parametrised with respect to flow velocity and initial condition. Comparisons to numerical integration find that while the system identification routine can accurately predict limit cycle amplitudes, a divergence in long term simulation error persists.

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Grants and Funding

Summary

Number of grants 4
Total funding $235,000

Click on a grant title below to expand the full details for that specific grant.


20211 grants / $40,000

High-Fidelity Modelling of a Cavity Aeroacoustics Phase 2$40,000

Development of efficient simulation workflows for modelling complex aerodynamic flows and assessing the influence of large-scale pressure fluctuations on the structural response of immersed bodies.

Funding body: Defence Science and Technology Group

Funding body Defence Science and Technology Group
Project Team

G.A. Vio, N.F. Giannelis & B. Thornber

Scheme Research Project
Role Investigator
Funding Start 2021
Funding Finish 2021
GNo
Type Of Funding C2110 - Aust Commonwealth - Own Purpose
Category 2110
UON N

20192 grants / $145,000

Underwater Effector Parametric Model Phase 2$95,000

Higher-fidelity modelling integration to parametric model of vehicle dynamics for the design of high-speed underwater vehicles.

Funding body: Thales

Funding body Thales
Project Team

S. Williams, G.A. Vio, D. Verstraete, L. Toohey & N.F. Giannelis

Scheme Research Project
Role Investigator
Funding Start 2019
Funding Finish 2020
GNo
Type Of Funding C3111 - Aust For profit
Category 3111
UON N

High-Fidelity Modelling of a Cavity Aeroacoustics Phase 1$50,000

Development of efficient simulation workflows for modelling complex aerodynamic flows and assessing the influence of large-scale pressure fluctuations on the structural response of immersed bodies.

Funding body: Defence Science and Technology Group

Funding body Defence Science and Technology Group
Project Team

G.A. Vio, N.F. Giannelis & B. Thornber

Scheme Research Project
Role Investigator
Funding Start 2019
Funding Finish 2019
GNo
Type Of Funding C2110 - Aust Commonwealth - Own Purpose
Category 2110
UON N

20181 grants / $50,000

Underwater Effector Parametric Model Phase 1$50,000

Development of a parametric model of vehicle dynamics for the design of high-speed underwater vehicles.

Funding body: Thales

Funding body Thales
Project Team

S. Williams, G.A. Vio, D. Verstraete, L. Toohey & N.F. Giannelis

Scheme Research Project
Role Investigator
Funding Start 2018
Funding Finish 2019
GNo
Type Of Funding C3111 - Aust For profit
Category 3111
UON N
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Research Supervision

Number of supervisions

Completed0
Current3

Current Supervision

Commenced Level of Study Research Title Program Supervisor Type
2021 PhD Fluid-structure interaction in junction flows Aerospace Engineering, The University of Sydney Consultant Supervisor
2020 Masters Research of Underactuated Swashplateless Unmanned Aerial Platform Designs Aerospace Engineering, The University of Sydney Consultant Supervisor
2019 PhD Non-linearity in Aeroelastic Structures Aerospace Engineering, The University of Sydney Consultant Supervisor
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Dr Nicholas Giannelis

Position

Lecturer
School of Engineering
College of Engineering, Science and Environment

Contact Details

Email nicholas.giannelis@newcastle.edu.au
Phone 02 4985 4437
Link Research Networks

Office

Room ES338
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