Gallery of the Australasian Fluid Mechanics Society

1st Prize
Fluid mechanics of tail-first swimming in mosquito larvae

The larvae of mosquitoes swim tail-first, which is quite distinct from head-first swimming seen in most fishes. Here, we experimentally investigate the propulsive mechanism of tail-first swimming in mosquito larvae through flow visualization and body tracking.

Karthick Dhileep, mentored by Dr Sridhar Ravi, Prof. John Young, A/Prof. Fang-Bao Tian and Prof. Joseph Lai, The University of New South Wales Canberra

2nd Prize
Cratering dynamics on lunar surface

Crewed lunar exploration for the NASA Artemis program will involve interactions between plumes generated by landers with the lunar surface, known as Plume-Surface Interaction (PSI). This interaction constitutes a significant obstacle to the missions due to the formation of craters that might destabilize the landers. Similarly, the ejection of high-velocity dust particles and rocks can damage the surrounding structures. To characterize these effects, we start by visually exploring the differences in cratering dynamics at atmospheric and near-vacuum ambient conditions. The features are vastly different, and the governing physics stands to be discerned.

Lokesh Silwal, mentored by A/Prof. Vrishank Raghav, Auburn University

3rd Prize
Comparing high and low temperature and momentum flux ratios for jets in a hypersonic crossflow

In the engine of a hypersonic scramjet aircraft, fuel is injected into the stream of air that enters the burner for combustion. As the air flows transversely to the fuel stream, this injection scheme is denoted as a jet in hypersonic crossflow. Here, the complex variability of this injection scheme is demonstrated with the comparison of two fuel streams injected into the same crossflow. Low and high momentum flux and temperature ratios are compared, with the turbulence visualised by the positive Q-criterion coloured by the velocity magnitude, and the shocks presented as volumes of the gradient of the density field.

Harry Colin Rowton, mentored by Dr Rey Chin and A/Prof. Paul Medwell, University of Adelaide

1st Prize
Time evolution of a circular release gravity current

The images show the evolution and mixing of a circular release gravity current. As the dense fluid slumps, lobe and cleft structures emergences and are associated with the radially aligned hairpin like structures. Kelvin-Helmholtz roller formed behind the gravity current head led to the generation of vortex rings (middle image). Counter rotating vortices are also formed close to the no-slip bottom wall due to high shear. These structures interact and breakdown via the elliptical instability forming secondary perpendicular filaments. These structures, coloured by density, have significant importance on the entrainment and mixing of ambient fluid.

Wai Kit Lam, mentored by Prof. Andrew Ooi, Dr Leon Chan, Dr Duncan Sutherland, Prof. Richard Manasseh and Prof. Khalid Moinuddin, University of Melbourne

2nd Prize
Coupled wakes behind a pair of Seal-whisker inspired elliptic cylinders

Seals have two or more whiskers emanating from the same follicle, helping them to maneuver and hunt prey efficiently. Inspired by Seal whiskers, the wake behind a pair of elliptic cylinders is studied using dye flow visualization. Fluorescein (green) and rhodamine (orange) dye is applied to the individual ellipses, and the flowfield is visualized using a planar laser sheet. The vortex wake is symmetric about the centerline, and an anti-phase synchronization of these vortices is observed under this Reynolds number condition (Re = 1000). Interestingly, the rolling up of the two outer vortices yields a logarithmic spiral pattern.

Abbishek Gururaj, mentored by A/Prof. Vrishank Raghav and Dr Sarah Morris, Auburn University

3rd Prize
Comparing high and low temperature and momentum flux ratios for jets in a hypersonic crossflow

Two air jets injected into the same Mach 5 hypersonic crossflow are compared in a mirrored visualisation. The jets differ in their ratios of temperature between the jet and crossflow streams, and therefore also differ in their respective Mach numbers and momentum flux ratios. The lower (top) momentum flux ratio jet visualised by the positive Q-criterion, as well as the resulting shocks shown by the gradient of the density field, both differ dramatically to the stronger jet (bottom) in size and structure. These differences alter the performance of the jet for fuel injection in the combustors of hypersonic aircraft.

Harry Colin Rowton, mentored by Dr Rey Chin and A/Prof. Paul Medwell, University of Adelaide

1st Prize
Dynamics of droplets and aerosols generated during respiratory exhalations

Infection control guidelines are based on the assumptions of the risk of droplets spread from various respiratory exhalations. Here, we present a method to visualize droplets expelled during various exhalations and a framework to understand their dynamics. We also presents the results of applying these visualisation techniques to show the efficacy of various facemasks.

Prateek Bahl, mentored by Prof. Con Doolan, Dr. Charitha de Silva, Prof. Raina MacIntyre and Dr. Abrar Chughta, The University of New South Wales Sydney

2nd Prize
Modelling the flow in the upper airway subjected to high-frequency ventilation

High-frequency ventilation (HFV) is a technique used to ventilate patients with critical respiratory failure and this animation manifest the flow in the trachea and main bronchi of the human airway subjected to HFV. The animation is based on the DNS data obtained by the open-source spectral element solver Nek5000 and the reciprocating flow driven by imposing time-varying Womersley solution at the free-end of the trachea. Conditional turbulence is observed downstream of the bifurcation when the flow rate passes a critical velocity and findings of this study will be used in controlling and optimising the HFV process.

Chinthaka Jacob, mentored by A/Prof. Justin Leontini, Swinburne University of Technology

3rd Prize
A-priori evaluation of data-driven models for large-eddy simulations in natural convection

Natural convection is a commonly occurring heat-transfer problems in many industrial flows. In this video, we chose a complicated case, that is the natural convection in a horizontal annulus, which background is the heat exchanger in industry. For low Rayleigh number case, the coexistence of fully turbulence, transitional flow, laminar and stagnation pose a challenge in turbulence modelling. The video shows the structure of the flow in this case.

Liyuan Liu, mentored by Dr. Chitrarth Lav and Prof. Richard Sandberg, University of Melbourne

1st Prize
Vortex formation around a downwind-sailing Olympic-class sailboat

A "sports-mimetic" approach is used to study unsteady sail motion techniques, inspired by Olympic sailors as they maneuver their sailboats when racing. Here, we use an Olympic Class Laser Sailboat sailed by a member of the Cornell Sailing Team in Ithaca, NY, to study the underlying vortex dynamics of a downwind-sailing boat via full-scale smoke visualization. An Enola Gaye WP40 smoke grenade is used to generate a smoke cloud large enough to see the large-scale flow features around the sail. As the smoke flows around the leech (trailing edge), we see the formation of a large counter-clockwise vortex.

Sarah Morris, mentored by Prof. C.H.K. Williamson, Cornell University, USA

Runner-up
Wall shear stress of the aortic dissection after surgical repair

Aortic dissection is an injury that occurs at the vessel walls of the human aorta allowing the undesirable situation of blood flowing in between the layers of the vessel walls. It has been shown that for long term health, the wall shear stress on vessel walls must be at an optimum level. This image shows wall shear stress distribution inside of an aorta of a patien with aortic dissection, visualised using data from direct numerical simulation. The visualisation may provide additional information for doctors to manage aortic dissection patients in the future.

Qingdi Wang, mentored by Prof. Andrew Ooi, University of Melbourne

1st Prize
Direct Numerical Simulation of Shock-Induced Turbulent Mixing

Direct numerical simulation of a turbulent mixing layer evolving from a three-dimensional, multimode Richtmyer-Meshkov instability. The animation depicts the evolution of volume fraction isosurfaces, showing red bubbles of rising light fluid and blue spikes of penetrating heavy fluid, after the interface between the two fluids is impacted by a shock wave.

Michael Groom, mentored by A/Prof. Ben Thornber, University of Sydney

2nd Prize
Direct numerical simulations of turbulent sheared thermal convection

The visualization reveals the final outcome of clear large scale meandering structures which are significantly more prominent than the large structures already observed in plane Couette flow. Depending on the choice of control parameters, these structures can be varied in thickness, number and wavelength. This type of flow, where buoyancy and shear interact, is a vital process in the area of fluid dynamics and the foundation for many mechanisms in nature.

Alexander Blass¹, Xiaojue Zhu¹, Jean M. Favre², Roberto Verzicco¹, Detlef Lohse¹, Richard J.A.M. Stevens¹, mentored by Prof. Detlef Lohse^1
1 Physics of Fluids Group, University of Twente, The Netherlands
² Swiss National Supercomputing Center

3rd Prize
Actuator Surface Modelling of the Sikorsky X2 Rotor

The Sikorsky X2 coaxial rotor was simulated in forward flight using an Actuator Surface Model (ASM). The ASM couples an aerodynamics model for the rotor blades and near wake to a CFD solver, reducing the computational cost and the pre-processing time by eliminating the body-fitted mesh. The X2 is an example of the kind of complex rotors which can be simulated using the ASM. Visualisation of the vortical structures in the wake clearly shows the strong interactions between the wakes of the upper and lower rotors, and the unsteady blade loading predictions reflect the interaction between the rotors.

Daniel Linton, mentored by A/Prof. Ben Thornber, University of Sydney

1st Prize
Trailing vortices formed by a gliding delta wing in ground proximity

Understanding vortex-wall interactions has applications in the context of airplane trailing vortices, as well as in fundamental turbulence. We generate a counter-rotating vortex pair by towing a delta wing through water, supported by thin wires that do not generate a vortex wake. Fluorescein dye is applied to the leading and trailing edge of the delta wing, and made visible by an argon-ion laser. Rather than using a traditional flood-light of the entire wake, we use a technique whereby only a cross-section of the von Kármán vortex street “braid wake” is illuminated, whilst still simultaneously illuminating the out-of- plane vortex pair.

Sarah E. Morris, mentored by Prof. C.H.K. Williamson, Cornell University, USA

2nd Prize
Renderings of temperature iso-surfaces from direct numerical simulations of two-phase vertical natural convection of water

Top left image: Vertical natural convection without light droplets.
Bottom left image: Vertical natural convection with light driplets at 0.5% of the domain volume fraction.
Right image: Vertical natural convection with light droplets at 2.0% of the domain volume fraction. The rising droplets disturb the initially quiescent temperature field, increasing mixing of warmer (towards red colour) and cooler (towards blue colour) fluids, which translates to an increase in heat transfer in the system.

Chong Shen Ng, Vamsi Spandan, Detlef Lohse and Roberto Verzicco, mentored by Prof. Detlef Lohse and Prof. Roberto Verzicco, University of Twente, The Netherlands

3rd Prize
Direct numerical simulations of turbulent sheared thermal convection

Direct numerical simulations of Rayleigh-Bénard flow with induced wall shearing have been performed on a 6912x3456x384 grid. Large coherent thermal structures emerge from the heated plate and meander. The vorticity formations are visualized with the Q-criterion. The zooms show small-scale structures in the flow.

Alexander Blass¹, Xiaojue Zhu¹, Jean M. Favre², Roberto Verzicco¹, Detlef Lohse¹, Richard J.A.M. Stevens¹, mentored by Prof. Detlef Lohse1.
¹Physics of Fluids Group, University of Twente, The Netherlands
² Swiss National Supercomputing Center

1st Prize
Dancing with the Stars

A smoothed particle hydrodynamics simulation of two stars undergoing the common envelope interaction.

Thomas Reichardt, mentored by Orsola De Marco, Macquarie University

2nd Prize
Turbulence in a linearly stratified body of fluid

When disturbance is created by an oscillating grid into a linearly stratified body of fluid, a special instability can be observed.

Scott Becker, Yanik Salgadoe, Imran Vilcassim and Ceser Daguet, mentored by Jimmy Philip, University of Melbourne

3rd Prize
Visualisation of wake flow induced by a moving manikin

CFD and Experimental techniques used for flow visualisation.

Yao Tao, mentored by Kiao Inthavong, RMIT
References: Tao, Y., Inthavong, K., Tu, J. (2016). Computational fluid dynamics study of human-induced wake and particle dispersion in indoor environment. Indoor and Built Environment
Inthavong, K., Tao, Y., Petersen, P., Mohanarangam, K., Yang, W., Tu, J. (2016) ‘A smoke visualisation technique for wake flow from a moving human manikin’ Journal of Visualization

Tidal bore of the Garonne River (France)

A tidal bore is an unsteady rapidly-varied free-surface flow generated by the rapid rise in water elevation during the early flood tide, when the tidal range exceeds 4.5 to 6 m and the channel bathymetry amplifies the flood tidal wave. The photograph shows the tidal bore of the Garonne River at Podensac (France) on 23 August 2013, about 28 km upstream of the city of Bordeaux. Detailed field measurements were conducted in this tidal bore.

Prof. Hubert Chanson, the University of Queensland
Reference: Reungoat, D., Chanson, H., and Keevil, C.E. (2015), Journal of Hydraulic Research, IAHR, Vol. 53, No. 3, pp. 291-301 (DOI: 10.1080/00221686.2015.1021717))

Oil film flow visualisation of tubercled, swept wing at a Reynolds number of 220,000 based on Mean Aerodynamic Chord

Flow is from left to right. Talcum powder and oil were painted on the foil surface, revealing the surface streak pattern. The image shows that the flow behind the outboard trough has undergone complete stall, but the inboard progression of the separation zone is limited by the presence of the tubercles. Although the flow behind the tubercle peaks remain attached, the accumulation of powder at the trailing edge behind the troughs demonstrates that these zones undergo separation at a lower angle of attack than a similar wing without tubercles.

Micheal Bolzon, University of Adelaide

Direct numerical simulation of a turbulent lifted flame

The animation depicts a direct numerical simulation of a turbulent, lifted slot-jet flame. Vorticity magnitude is shown in blue/white, while heat release rate is shown in orange/red. The DNS were used to study the stabilisation mechanism of lifted flames, which is a long-standing problem in the combustion community. The analysis, published in the Journal of Fluid mechanics [S. Karami, E. R. Hawkes, M. Talei, J. H. Chen, J. Fluid Mech. 777 (2015), pp. 633-689], shows that the flame is stabilised by the propagation of partially premixed edge flames, moderated by the passage of large eddies. The research was supported by the Australian Research Council, and the simulation was performed on Raijin, operated by the National Computational Infrastructure (NCI).

Shahram Karami, University of New South Wales

LES of a supersonic impinging jet

Dr Shahram Karami and a team of PhD students in a project led by Professor Julio Soria at Laboratory for Turbulence Research in Aerospace and Combustion (LTRAC) within the Department of Mechanical and Aerospace Engineering at Monash University are developing a numerical framework to simulate supersonic free and impinging jets and study the instabilities and complex spatio-temporal structure of these flows. The animation presents the time evolution of the key parameters of one of the large eddy simulations of under-expanded supersonic impinging jets. The visualisation depicts the temporal evolution of isosurface of vorticity magnitude colored by total energy (left), velocity magnitude (right-top) and magnitude of the density gradient (right-bottom) where the quantities are normalised by the speed of sound and jet diameter (D).

Dr Shahram Karami and Prof Julio Soria, Laboratory for Turbulence Research in Aerospace & Combustion (LTRAC), Department of Mechanical and Aerospace Engineering, Monash University
The research was supported by the Australian Research Council via Discovery and LIEF grants and National Computational Merit Allocation Scheme (NCMAS) grants
The simulation was performed on Raijin, operated by the National Computational Infrastructure (NCI)

Schlieren flow visualisation and large eddy simulation (LES) of impinging under-expanded supersonic jet flow at a nozzle pressure ratio of 3.4

Upper Image: The Schlieren flow visualization by Nick Mason-Smith, Daniel Edgington-Mitchell, Nicolas Buchmann, Damon Honnery and Julio Soria is at a stand-off distance of 2.5 (Mitchell, D. M., Honnery, D. R., & Soria, J. (2012). The visualization of the acoustic feedback loop in impinging underexpanded supersonic jet flows using ultra-high frame rate Schlieren, 15(4), 333–341.).
Lower Image: The LES by Paul Stegeman, Andrew Ooi and Julio Soria was computed using a compressible in-house developed code at a standoff-off distance of 2.0, where the blue iso-surface of the second invariant of the velocity gradient tensor represents vortical structures, the red iso-surface represents negative divergence indicating highly compressible regions which are representative of the location of shocks and the planar contour plot represents the density of the fluid.

Prof. Julio Soria, Monash University

Pressure distribution on the surface of the upper airway

Pressure distribution (colour spectrum from: red = 0Pa to blue = -44.3Pa) on the surface of the upper airway, from the nares (nose) to the tracheal-oesophageal branch, during inspiration for a flow-rate of 21L/min. The geometry is reconstructed from CT data and discretised using an unstructured mesh of 6 million cells.

Dr Julien Cisonni, Fluid Dynamics Research Group, Curtin University

Streakline image of acoustic microstreaming around a 225+/-25 micron diameter bubble excited into n=7 shape modes at 12 kHz

Prof. Richard Manasseh, Swinburne Institute of Technology
Reference: Tho et al 2007, J. Fluid Mech. Vol. 576, 191-233

Time-averaged streamlines of a pitched and skewed vortex generating jet issuing into a turbulent boundary layer

The streamlines show higher momentum fluid from the outer regions of the boundary layer (red streamlines) being swept into the near-wall region. The simulation was computed using a custom LES boundary-layer code; inlet boundary conditions were provided with a variant of the Lund et al inflow generation condition.

Dr James Jewkes, Fluid Dynamics Research Group, Curtin University
Reference: Jewkes et al., AIAA J. 49(1):247–250, 2011

Flow over an Austin Mini

CFD flow field (pressure contours and streamlines) over an Austin Mini at 72 km/h computed with RANS k­ω turbulence model using OpenFOAM on a 48‐core commodity cluster

Dr Andrew King, Fluid Dynamics Research Group, Curtin University