Bulletin of the American Physical Society
67th Annual Meeting of the APS Division of Fluid Dynamics
Volume 59, Number 20
Sunday–Tuesday, November 23–25, 2014; San Francisco, California
Session R27: Turbulence: General II 
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Chair: Meng Wang, University of Notre Dame Room: 2009 

R27.00001: ABSTRACT WITHDRAWN 
Tuesday, November 25, 2014 1:18PM  1:31PM 
R27.00002: Unsteady ReynoldsAveraged NavierStokes Analysis of Turbulent Flow in the Venturi Dustiness Tester Prahit Dubey, Urmila Ghia, Leonid A. Turkevich Dustiness quantifies the propensity of a finely divided solid to be aerosolized by a prescribed mechanical stimulus. Dustiness is relevant wherever powders are mixed, transferred or handled, and is important in the control of hazardous exposures and the prevention of dust explosions and product loss. Limited (mg) quantities of pharmaceutical powders available for testing led to the development (at University of North Carolina) of a Venturidriven dustiness tester. The powder is turbulently injected at highspeed (for 1.5 sec) into a glass chamber; the aerosol is then gently sampled (for 240 sec) through two filters located at the top of the chamber; the dustiness index is the ratio of sampled to injected mass of powder. Injection is activated by suction at a port at the top of the chamber; loss of powder during injection compromises the sampled dustiness. The present work analyzes the flow inside the Venturi Dustiness Tester, using an Unsteady ReynoldsAveraged NavierStokes formulation with the k$\omega $ Shear Stress Transport turbulence model. The simulation considers singlephase flow, valid for small particles (Stokes number Stk \textless 1). Results for velocity, turbulence kinetic energy, and pathlines during highspeed injection are presented. The results show that 24{\%} of the injected powder escapes from the chamber during injection. [Preview Abstract] 
Tuesday, November 25, 2014 1:31PM  1:44PM 
R27.00003: The effective surface tension coefficient in twophase flows with interface in the framework of grouptheoretical model of turbulence Mikhail Gorokhovski, Vladimir Saveliev In our paper PRE 72, 016302 (2005), three main results concern: (i) a new model of stationary homogeneous turbulence on the basis of the Euler equations; (ii) the regularized averaging formula for the product of two fields; (iii) the renormalization of the NavierStokes equation in which the turbulent viscosity appeared not from averaging of the nonlinear term, but from the molecular viscosity term. The new raised question is as follows. In immiscible gasliquid turbulent flows with a fluidinterface, the NavierStokes equations are completed by the surface tension force, acting on the interface. Then in the framework of the aforementioned paper, what is the renormalized form of this force at a high Weber and Reynolds numbers, and in terms of LES, what are the governing equations. The result is this: the surface tension force appears in its effective (``turbulent'') form, which depends on the filtered strain rate, the thickness of the filter, and the ratio between dissipative and critical scales. Also different formulations of the specific volume transport equation are discussed. [Preview Abstract] 
Tuesday, November 25, 2014 1:44PM  1:57PM 
R27.00004: Spatially resolved measurements of finescale structure in a turbulent flow between two counterrotating disks using scanning PIV John Lawson, James Dawson The smallest lengthscales of turbulent motion contain important features of its character: they are strongly intermittent and are responsible for the dissipation of kinetic energy and microscale mixing. Until recently, access to space and timeresolved, 3D measurements of turbulent velocity fields has largely been the purview of numerical simulation. The capabilities of existing experimental techniques, such as tomographic PIV and stereo PIV, have limited their application to laboratory investigation of the fine scale motion. We have developed a variant upon scanning PIV using two high speed cameras, combining aspects of tomographic reconstruction and 3D crosscorrelation techniques to yield time resolved, 3D3C measurements in a turbulent flow between two counterrotating disks at $R_\lambda \simeq 219$. The measurement is low noise, exhibits a variety of finescale phenomena and captures the turbulent dissipation to within 3\%. Statistics of velocity gradients are consistent with homogeneous, axisymmetric turbulence but not isotropy. This new capability permits us to present a handful of results concerning the finescale structure of the velocity field and its derivatives, from the perspective of an observer travelling with the flow and aligned with the strain eigenframe. [Preview Abstract] 
Tuesday, November 25, 2014 1:57PM  2:10PM 
R27.00005: Multiple states in highly turbulent TaylorCouette flow Sander Huisman, Roeland van der Veen, Chao Sun, Detlef Lohse The ubiquity of turbulent flows in nature and technology makes it of utmost importance to fundamentally understand turbulence. Kolmogorov's 1941 paradigm suggests that for strongly turbulent flows with many degrees of freedom and its large fluctuations, there would only be \emph{one} turbulent state as the large fluctuations would explore the entire higherdimensional phase space. Here we report the first conclusive evidence of multiple turbulent states for large Reynolds number Re $ = \mathcal{O}$($10^6$) (Taylor number Ta $= \mathcal{O}$($10^{12}$) TaylorCouette flow in the regime of ultimate turbulence, by probing the phase space spanned by the rotation rates of the inner and outer cylinder. The manifestation of multiple turbulent states is exemplified by providing combined global torque and local velocity measurements. This result verifies the notion that bifurcations can occur in highdimensional flows (i.e. very large Re) and questions Kolmogorov's paradigm. [Preview Abstract] 
Tuesday, November 25, 2014 2:10PM  2:23PM 
R27.00006: Simultaneous measurement of aerooptical distortion and turbulent structure in a heated boundary layer Theresa SaxtonFox, Beverley McKeon, Adam Smith, Stanislav Gordeyev This study examines the relationship between turbulent structures and the aerooptical distortion of a laser beam passing through a turbulent boundary layer. Previous studies by Smith et al (AIAA, 2014  2491) have found a bulk convection velocity of $0.8U_{\infty}$ for aerooptical distortion in turbulent boundary layers, motivating a comparison of the distortion with the outer boundary layer. In this study, a turbulent boundary layer is developed over a flat plate with a moderatelyheated section of length $25\delta$. Density variation in the thermal boundary layer leads to aerooptical distortion, which is measured with a Malley probe (Smith et al, AIAA, 2013  3133). Simultaneously, 2D PIV measurements are recorded in a wallnormal, streamwise plane centered on the Malley probe location. Experiments are run at $Re_{\theta}=2100$ and at a Mach number of 0.03, with the heated wall 10 to $20^{\circ}$C above the free stream temperature. Correlations and conditional averages are carried out between Malley probe distortion angles and flow features in the PIV vector fields. Aerooptical distortion in this study will be compared to distortion in higher Mach number flows studied by Gordeyev et al (J Fluid Mech, 2014), with the aim of extending conclusions into compressible flows. [Preview Abstract] 
Tuesday, November 25, 2014 2:23PM  2:36PM 
R27.00007: AeroOptical Distortions by Supersonic Turbulent Boundary Layers Kan Wang, Meng Wang Largeeddy simulations are performed to investigate the aerooptical distortions caused by Mach 2 flatplate turbulent boundary layers at $Re_\theta = 2650$ with wall temperatures at 0.8, 1.0 and 1.2 times the adiabatic wall temperature. The optical distortions for the adiabatic wall temperature case are compared with those caused by a subsonic turbulent boundary layer at a similar Reynolds number. It is found that the distortion magnitude normalized by the product of freestream density, square of Mach number and boundarylayer thickness is slightly lower in the supersonic boundary layer than that in the subsonic boundary layer. The relative contributions from different flow regions to the optical path difference and its twopoint spatial correlations are similar for subsonic and supersonic boundary layers. The contribution of Mach waves generated in the supersonic boundary layer to optical distortions is found to be small. The wall temperature significantly affects optical distortions. The distortion magnitude decreases with decreasing wall temperature, which is consistent with experimental findings. [Preview Abstract] 
Tuesday, November 25, 2014 2:36PM  2:49PM 
R27.00008: Aerooptical predictions using wallmodeled LES Mohammed Kamel, Kan Wang, Meng Wang The accuracy of LES with wallmodeling for predicting aerooptical distortions is evaluated in turbulent boundary layers and flow over a cylindrical turret by comparing results with those from previous wallresolved LES and experiments. For turbulent boundarylayer flows at Mach 0.5 and momentumthickness Reynolds numbers up to $31000$, the velocity statistics in the majority of the logarithmic layer and the wake region are well predicted with an equilibrium stressbalance model, but the level of density fluctuations and hence optical wavefront distortions are overpredicted. The causes for the overprediction and model improvement are investigated. When wallmodeled LES is applied to compute the turbulent flow over a cylindrical turret with a flat window at Mach 0.5 and the experimental Reynolds number of $5.6 \times 10^5$ based on the cylinder radius, both the flow statistics and optical distortions induced by the separated shear layer agree well with experimental measurements and previous wallresolved LES results at a lower Reynolds number. The incorporation of the pressure gradient effect in wallmodel equations is shown to improve the prediction of the fluctuating density field and optical distortions. [Preview Abstract] 
Tuesday, November 25, 2014 2:49PM  3:02PM 
R27.00009: Effects of Viscosity Switch in the Evolution of a Free Shear Layer Ujjayan Paul A free shear layer starting from smooth initial conditions can lose accuracy during time evolution and then blow up at a critical time. This difficulty arises intrisically from the equations of motion. An artificial dissipation at each time step is applied. Since a real fluid will always be viscous, the artificial dissipation is not non physical after all. An adaptive grid size is used to resolve a flow at very small scales since a constant grid will always fail to resolve micro structures. As the flow passes the critical time point large scale motion strains the sheet and the problem of an increasing number of singularities is eliminated using a vortex switch. [Preview Abstract] 
Tuesday, November 25, 2014 3:02PM  3:15PM 
R27.00010: Symmetry breaking in 3D wake of a bluff body generates rotation and drift Ugis Lacis, Nicolas Brosse, Shervin Bagheri, Fredrik Lundell, Andrea Mazzino, Stefano Olivieri, Hamid Kellay Bluff body wakes have historically been important for understanding nature and aiding industry. For Reynolds numbers above approximately Re $\approx 10$, a recirculation bubble develops behind the bluff body. If a solid or elastic appendage is attached to the bluff body, it may exert a torque and a side force on the body. Previously we have used theory, numerical simulations and experiments to investigate and explain this phenomenon in two dimensions. Now we advance our investigation to three dimensional objects. More specifically, we consider a sphere and attach a sheet of given shape behind it for Re $= 200$. We investigate the problem using numerical simulations and extend our theoretical model developed in two dimensions. Then we complement our findings with water tank experiments of freely falling cylinder with sheet of various mass behind it. We show that the torque and side force can be greatly changed if the density of the sheet is different compared to the cylinder. Finally we discuss the possibility of optimal configurations for propulsion generation. [Preview Abstract] 
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