Adam Fincham

University of Southern California, Aerospace & Mechanical Engineering, Faculty Member

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Hai-Yao DENG

The University of Manchester

Armando Marques-Guedes

UNL - New University of Lisbon

K.W. Chau

Hong Kong Polytechnic University

Antonio Bula

Universidad del Norte - Barranquilla, Colombia

naveen noronha

Visvesvaraya Technological University

Mikail F Lumentut

National Taiwan University

OMAR YAAKOB

Universiti Teknologi Malaysia - UTM

Isad Saric

University of Sarajevo

Richard Crawford

The University of Texas at Austin

Wei-Liang Qian

Universidade de São Paulo

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Papers by Adam Fincham

3D time-resolved Vorticity field Measurements in Stratified Rotating fluids

By exploiting the extreme anisotropy present is late time stratified flows where the vertical com... more By exploiting the extreme anisotropy present is late time stratified flows where the vertical component of velocity has been suppressed, a stack of horiz ontal slices is sufficient to fully reconstruct the 3D vorticity field. Though the velocity field is quasi 2D in nature, these flows exhibit a complex three di mensional vortex structure. The fully turbulent state consists of

Wave generator and surface gravity wave pool

A wave pool (100; 300; 400) comprising: - a channel (106) containing water and having a side wall... more A wave pool (100; 300; 400) comprising: - a channel (106) containing water and having a side wall (200) having a height, and a contour line having a slope upwards away from the side wall (200) to a bank (206); - one or more sheets (500; 600; 704; 906; 1006) being disposed each sheet (500; 600; 704; 906; 1006) a major portion of the side wall (200) vertically along at least and adapted for movement in a direction along a length of the side wall (200), each sheet (500; 600; 704; 906; 006) geometry curvilinear cross-section defining a leading face (502) which is adapted to generate a wave in water after its movement, and an exit surface (504) characterized in that the exit surface (504) is configured for recovery flow to avoid separation of the water flow in the wave and to mitigate the drag from the sheet (500; 600; 704; 906; 1006) by movement, and that the side wall (200) includes a flexible outer wall and a rigid inner wall, and a mechanism of formation of the sheet between the flex...

Comparative behavior of piloted turbulent premixed jet flames of C 1 C 8 hydrocarbons

Combustion and Flame

Abstract An exploratory study was performed on highly turbulent piloted premixed jet flames of st... more Abstract An exploratory study was performed on highly turbulent piloted premixed jet flames of straight chain (paraffin and olefin), branched, cyclo, and aromatic C 1 C 8 hydrocarbons. The goal was to investigate fuel effects on global and local flame observables under flow conditions corresponding to the transition from the thin to the broken reaction zone regimes. The experiments were performed at atmospheric pressure, reactant temperature of 298 K, jet Reynolds numbers of 12,500 and 25,000, and various equivalence ratios and fuels in order to assess the attendant effects on the flame characteristics. The effects of heat losses from the flame were considered also in order to sensitize kinetic effects. Measurements were performed using particle image velocimetry and spontaneous luminosity imaging. The averaged and fluctuating velocity components as well the average flame height were determined to scale in general with the laminar flame speed. The exception to this scaling was the height of methane flames that exhibit notable differences compared to large molecular weight fuels. Subtle differences were identified even among the large hydrocarbon flames and became evident from measurements of the instantaneous luminosity field. Finally, high-speed luminosity imaging revealed that there are apparent fuel effects on the local structure of the flame as evident by the distribution and size of luminous pockets. These results suggest that the fuel effects should be also the focus of further investigations by the community.

Experimental and numerical studies of fuel and hydrodynamic effects on piloted turbulent premixed jet flames

Proceedings of the Combustion Institute

An experimental and numerical investigation of fuel and hydrodynamic effects is performed on pilo... more An experimental and numerical investigation of fuel and hydrodynamic effects is performed on piloted premixed jet flames. The investigation is carried out at a constant laminar flame speed, varying heat losses, jet Reynolds number, fuel molecular weight, and fuel chemical classification. Large Eddy Simulations are performed in an attempt to reproduce the behaviors observed experimentally. Simulations are compared against well-characterized boundary conditions, well-resolved two-dimensional velocity fields from particle image velocimetry, and line-of-sight CH⁎ profiles. Experimental results indicate that small amounts of heat losses may play a significant role on the jet reactivity as the flame heights scale with the heat loss from the jet. However, differences between flames with different fuels can still be seen in the absence of heat losses and these differences are magnified at higher Reynolds numbers. Particularly, methane flames are consistently taller and ethylene flames consistently shorter while other fuels present approximately the same flame height. LES reproduce the experimentally observed trends in global flame heights (effects of heat losses and Reynolds number) but some of the differences between fuels are not captured.

Dissipation of Vortex Structures in Stratified Rotating Fluids

Agu Spring Meeting Abstracts, May 1, 2002

The late time evolution of turbulence in the presence of stable density stratification leads to a... more The late time evolution of turbulence in the presence of stable density stratification leads to a state of quasi-2D vortices separated vertically by strong horizontal vortex sheets. As both the buoyancy scale u/N and the vertical velocity w approach zero the vorticity field remains highly 3D as strong vertical shearing between structures promotes a horizontal alignment of the vorticity vector,

Vorticity Measurement and Vortex Structure in Stratified Fluids

A new laboratory measurement technique is used to directly simulate the time evolution of flows i... more A new laboratory measurement technique is used to directly simulate the time evolution of flows in large scale hydraulic facilities and make full field 3D time-resolved vorticity measurements. This technique, Direct Laboratory Simulation (DLS) relies on getting the Reynolds number from the length scale while keeping the velocity small, hence providing a characteristic time scale that is sufficiently large to

3D vortex structures in rotating stratified fluids

The structure of the vorticity field of freely decaying stably stratified turbulence in the low F... more The structure of the vorticity field of freely decaying stably stratified turbulence in the low Froude number regime is experimentally investigated for late times with a high resolution Correlation Image Velocimetry system (CIV). Quasi-2D vortices seperated vertically by strong horizontal vortex sheets are quickly formed. As the buoyancy scale u/N approaches zero the vorticity field remains highly 3D as strong

Can DPIV measure high Reynolds number turbulence ?

The application of Imaging Velocimetry (IV) measurements to fully turbulent flows is nowadays com... more The application of Imaging Velocimetry (IV) measurements to fully turbulent flows is nowadays commonplace. Although the work in this area is quite extensive, adequate analysis of the interaction of the imaging constraints with the turbulent flow itself has not been made. Extensive work involving both simulations with DNS datasets, and high Reynolds number laboratory experiments, shows good agreement with a

Effects of background rotation on a towed-sphere wake in a stably stratified fluid

Nuovo Cimento C Geophysics Space Physics C, Nov 1, 1999

The wake of a towed sphere in a stable background density gradient can be considered a convenient... more The wake of a towed sphere in a stable background density gradient can be considered a convenient model problem for studying the emergence and longevity of the coherent patches of alternate-signed vertical vorticity that comprise the late wake. In practical applications it is likely that the lifetime is such that rotation effects should also be considered, and strong rotation can also be used to deliberately disturb the inferred three-dimensional wake structure. Competing effects of stratification and rotation can be measured by the ratio of rotation to buoyancy timescales, fON, which varies from 0.05 to 0.22 in experiments conducted on the 14 m diameter rotating table at Coriolis. Wake anticyclones, with sense of rotation opposite to the background rotation, were spread out over a larger area, and were less strongly peaked than their cyclonic counterparts, with the magnitude of the asymmetry depending on fON. Deformation of anticyclones into highly elliptical shapes coincided with a broader range of wake vortex interactions than in the non-rotating case. At much longer times (hundreds of buoyancy periods, 5-10 rotation times), a recircularisation of elliptical anticyclones can occur. The observed asymmetries are consistent with existing data on homogeneous wake flows with rotation.

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Continuous scanning, laser imaging velocimetry

Journal of Visualization, 2006

Careful exploitation of the anisotropy native to late time stratified and rotating flows permits ... more Careful exploitation of the anisotropy native to late time stratified and rotating flows permits the use of a laser scanning measurement technique to simultaneously resolve the 2D velocity field in O(100) slices. The technique relies on getting the Reynolds number from the length scale while keeping the velocity small, this provides a characteristic time scale that is sufficiently large to permit full 3D scanning through the measurement volume in a relatively short time. As the vertical velocity component of these late time stratified flows is effectively zero, all components of the deformation tensor are resolved. 3D, time resolved measurements of the vorticity and enstrophy fields associated with stratified rotating flows such as vortex dipoles, monopoles and wakes are presented.

Journal of Fluid Mechanics, 1996

Late wakes (Nt > 20) of towed spheres in a stably stratified fluid were analysed in a plane us... more Late wakes (Nt > 20) of towed spheres in a stably stratified fluid were analysed in a plane using a reliable, customized DPIV technique that provides sufficient spatial and temporal resolution to cover all important scales of motion in this freely decaying geophysical flow. Systematic experiments were conducted with independent variation of Re ∈ [103, 104] and F ∈ [1, 10] (F ≡ 2U/ND is an internal Froude number based on the buoyancy frequency, N, and the sphere radius, D/2), and for selected {Re, F} pairs above this range.The normalized wake width grows at approximately the same rate as in a three-dimensional unstratified wake, but it becomes narrower, not wider, with decreasing F (i.e. as stratification effects become more important). The centreline defect velocity, on the other hand, reaches values an order of magnitude above those measured for three-dimensional unstratified wakes at equivalent downstream locations. Both observations are argued to be consequences of the very hi...

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Advanced optimization of correlation imaging velocimetry algorithms

Experiments in Fluids, 2000

Signi®cant developments aimed at improving the performance of digital particle imaging velocimetr... more Signi®cant developments aimed at improving the performance of digital particle imaging velocimetry (DPIV) type techniques are presented. The analysis applies directly to the correlation imaging velocity (CIV) technique but is applicable to all forms of imaging velocimetry measurement. These improvements revolve around a hierarchical processing scheme, and take into account the effects of the local¯uid deformation calculated from successive passes. Crucial to the implementation of these techniques is the ability to transform the discrete image into a continuous function that can be deformed and resampled at arbitrary resolution. Alternative methods of sub-pixel positioning are presented along with a new diagnostic tool for evaluating the severity of peak-locking errors in actual laboratory data. The performance of the new algorithms is illustrated with examples of turbulent laboratory¯ows, and simulated images obtained from analytic¯ow solutions or direct numerical simulations (DNS).

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The long-time evolution of the initially turbulent wake of a sphere in a stable stratification

Dynamics of Atmospheres and Oceans, 1996

Experiments on late wakes (Nt > 20) of towed spheres in a stably stratified fluid reveal some sta... more Experiments on late wakes (Nt > 20) of towed spheres in a stably stratified fluid reveal some startling similarities and differences when compared with unstratified, 3D wakes. Predicted decay rates stemming from 3D, turbulent wake studies are unexpectedly successful in accounting for the decay in fluctuating horizontal velocity components and their spatial gradients, even at late times when the vertical velocity component is almost or exactly zero. On the other hand, the mean wake defect velocity is almost one order of magnitude higher than in the unstratified case. This is due to the increased coherence and organisation of the patches of vertical vorticity, which are stable, and persist for very long times. A correct accounting for this type of wake structure will be essential in modelling efforts for certain practical ocean applications.

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Energy dissipation and vortex structure in freely decaying, stratified grid turbulence

Dynamics of Atmospheres and Oceans, 1996

Full field digital particle image velocimetry (DPIV) measurements of strongly stratified grid tur... more Full field digital particle image velocimetry (DPIV) measurements of strongly stratified grid turbulence have been carried out for long times (up to Nt = 1000). Quasi-2D vortices were formed that were separated vertically by strong horizontal vortex sheets. Dissipation scales were resolved and the relative dissipation fractions in the horizontal and vertical planes were determined. A simple vortex model, involving a dense packing of discus-shaped structures connected by vortex lines that alternate between horizontal and vertical orientation, is shown to be consistent with both the observed velocity and vorticity fields, and the evolution of the measured length scales in orthogonal planes.

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An experimental study of sonic boom penetration under a wavy air-water interface

Public reporting burden for the collection of information is estimated to average 1 hour per resp... more

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Stratified Turbulence in the Pancake Regime

Careful application of new laser scanning velocimetry techniques has allowed for detailed, time-r... more

Large-scale experimental study of the formation of zonal jets in convectively-driven geostrophic turbulence on a beta-plane

One of the most striking aspects of the appearance of the gas giant planets in the outer solar sy... more One of the most striking aspects of the appearance of the gas giant planets in the outer solar system is the persistent and stable organisation of their upper cloud decks into zonal-oriented belts and zones, in association with a pattern of strong latitudinally-alternating zonal winds. Since the early numerical model simulations of Williams (1978), it has been suggested that this

Wave Generator System and Method for Free-Form Bodies of Water

Surface Gravity Wave Generator and Wave Pool

Soot formation in flames of model biodiesel fuels

Combustion and Flame, 2012

3D time-resolved Vorticity field Measurements in Stratified Rotating fluids