Bulletin of the American Physical Society
70th Annual Meeting of the APS Division of Fluid Dynamics
Volume 62, Number 14
Sunday–Tuesday, November 19–21, 2017; Denver, Colorado
Session M28: Turbulence: DNSCFD Turbulence

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Chair: Kai Schneider, AixMarseille Universite Room: 207 
Tuesday, November 21, 2017 8:00AM  8:13AM 
M28.00001: Abstract Withdrawn Direct numerical simulations (DNS) of spanwiserotating turbulent channel flow were conducted. The data base obtained from these DNS simulations were used to investigate the effects of rotation on the coherent structures of the turbulence generation cycle. At high rotation numbers, relaminarization mechanisms fully suppressed turbulence production in the nearwall region of the suction side but for a low rotation number, characteristics of transitional turbulence were identified. In addition, lower and higherReynolds number simulations conducted at a rotation number Ro$_{\mathrm{b}} \quad =$ 0.2 were compared and significant characteristical differences in the turbulence production cycle were identified. The analyses of coherent structures was also used to determine the proper computational box size for a minimal flow unit (MFU) at Ro$_{\mathrm{b}} \quad \le $ 0.5. Proper realization of TaylorGortler vortices in the highly turbulent pressure region was demonstrated to be necessary for acceptably accurate MFU turbulence statistics, which required a minimum spanwise domain length L$_{\mathrm{z}} \quad = \quad \pi $. 
Tuesday, November 21, 2017 8:13AM  8:26AM 
M28.00002: Numerical simulation of fluidstructure interaction of turbulent boundary layer with an elastic plate Sreevatsa Anantharamu, Krishnan Mahesh Understanding the influence of turbulent boundary layer wallpressure fluctuations on elastic structures is essential to understand the acoustic radiation to farfield due to their vibration. A parallel unsteady structural solver is being developed to solve linear/nonlinear elasticity problems using Finite Element Method. Several wallpressure crossspectral density models have been proposed in literature for turbulent boundary layers. A methodology will be discussed to synthetically generate spacetime wallpressure fluctuations given its crossspectral density. The crossspectral density of plate displacement from PoissonKirchhoff theory will be compared to the results obtained numerically using the synthetically generated pressure fluctuations. Pressure fluctuations from a DNS of turbulent channel flow will then be used to excite the plate. Unsteady stresses inside the plate and the resulting deformation will be discussed. [Preview Abstract] 
Tuesday, November 21, 2017 8:26AM  8:39AM 
M28.00003: Effects of a strong magnetic field on turbulence subjected to axisymmetric contraction X.M. Zhai, M.P. Clay, P.K Yeung Many engineering applications and laboratory experiments involve the flow of fluids subjected to axisymmetric mean strain associated with the effects of varying crosssectional area. If the fluid is conducting and a magnetic field is present then the Lorentz force leads to further complexities. In this work we apply a uniform magnetic field to homogeneous turbulence after a timedependent axisymmetric contraction (Clay \& Yeung, {\em J. Fluid Mech.} {\bf 805}, 460493 (2016)) designed to mimic experiments. A magnetic field along the extensional direction is observed to initially weaken the anisotropy that developed from the contraction, but at later times the flow shows a high degree of anisotropy resembling that seen in simulations with isotropic initial conditions. The small scales no longer return to isotropy although they remain statistically axisymmetric. The anisotropy development is analyzed by computing various terms (including the Joule dissipation tensor) in the Reynolds stress budget equation, and studying directional properties of energy transfer in wavenumber space. We also compare results at different Reynolds numbers and magnetic interaction parameters. [Preview Abstract] 
Tuesday, November 21, 2017 8:39AM  8:52AM 
M28.00004: Nonlinear amplification in hydrodynamic turbulence Kartik Iyer, Katepalli Sreenivasan, P.K Yeung Using Direct Numerical Simulations performed on periodic cubes of various sizes, the largest one being $8192^3$, we examine the nonlinear advection term in the NavierStokes equations in fully developed turbulence. Flow regions with depleted nonlinearity are not found to be correlated with low dissipation, in contrast to theoretical claims (Moffat $\&$ Tsinober, Annu.~Rev.~Fluid Mech.~{\bf 24} 281312 (1992)). With increasing Reynolds number ($R_\lambda$), the NavierStokes dynamics amplifies the solenoidal (divergence free) part of the nonlinear term, in contrast to the nonlinear suppression observed in past studies (Kraichnan $\&$ Panda, Phys.~Fluids {\bf 31} 23952397 (1988); Shtilman, Phys.~Fluids A {\bf 4} 197199 (1992)), at low $R_\lambda$. With increasing $R_\lambda$, the nonlinear amplification makes the vortex stretching mechanism more intermittent, with the vortex stretching spectrum displaying a scaling anomaly similar to other smallscale quantities commonly examined in turbulence. At higher $R_\lambda$, the vortex tubes are passively advected for much of the time, with the intense stretching of the vortex tubes occurring rarely, but accounting for much of the forward cascade dynamics. [Preview Abstract] 
Tuesday, November 21, 2017 8:52AM  9:05AM 
M28.00005: Fine scale eddy cluster in turbulent channel flow Kosuke Osawa, Yuki Minamoto, Masayasu Shimura, Mamoru Tanahashi Geometry and distribution of fine scale eddy clusters in wall turbulence are studied. Databases of direct numerical simulation of turbulent channel flow at $Re_{\tau } \approx 10^{3}$ are used for the investigation. To take account of every fine scale eddies existed in the flow independent of their strength, the eddies are identified by their swirling motion. Clustering of the fine scale eddies are evaluated quantitatively by introducing Voronoi diagram. Dimensions and topological properties of the clusters are also studied based on the diagram. The results show that the spacing of individual eddies is roughly scaled by the Taylor micro scale at the given height. Comparison with the result from unbounded turbulence suggests that dimension of the vortex clusters are significantly affected by their distance from the walls. Relative position of the vortex clusters and high and low momentum region is investigated to discuss the role of the vortex clusters in wall turbulence. [Preview Abstract] 
Tuesday, November 21, 2017 9:05AM  9:18AM 
M28.00006: DNS of a nonequilibrium adverse pressure gradient turbulent boundary layer Taygun R. Gungor, Ayse G. Gungor, Yvan Maciel, Mark P. Simens A new direct numerical simulation (DNS) dataset of a nonequilibrium adverse pressure gradient (APG) turbulent boundary layer (TBL) that evolves from a zeropressuregradient (ZPG) TBL to a TBL which is very close to separation at $Re_\theta$ is around 8200 is presented. There are two simulations running together in the DNS computational setup. The APG TBL spans $Re_\theta = 1476  8276$. Mean velocity results do not satisfy the log law as the defect in the velocity increases. The production and the Reynolds stress peak are observed around $y/\delta^*=1$ after the flow is evolved up to a certain point. The new dataset is compared with other datasets in terms of mean values, Reynolds stresses and turbulent kinetic energy budgets and using this comparison scaling study is performed. [Preview Abstract] 
Tuesday, November 21, 2017 9:18AM  9:31AM 
M28.00007: Direct Numerical Simulation of Passive Scalar Mixing in Shock Turbulence Interaction Xiangyu Gao, Ivan BermejoMoreno, Johan Larsson Passive scalar mixing in the canonical shockturbulence interaction configuration is investigated through shockcapturing Direct Numerical Simulations (DNS). Scalar fields with different Schmidt numbers are transported by an initially isotropic turbulent flow field passing across a nominally planar shock wave. A solutionadaptive hybrid numerical scheme on Cartesian structured grids is used, that combines a fifthorder WENO scheme near shocks and a sixthorder centraldifference scheme away from shocks. The simulations target variations in the shock Mach number, $M$ (from $1.5$ to $3$), turbulent Mach number, $M_t$ (from 0.1 to 0.4, including wrinkled and brokenshock regimes), and scalar Schmidt numbers, $Sc$ (from 0.5 to 2), while keeping the Taylor microscale Reynolds number constant ($Re_{\lambda}\approx40$). The effects on passive scalar statistics are investigated, including the streamwise evolution of scalar variance budgets, pdfs and spectra, in comparison with their temporal evolution in decaying isotropic turbulence. [Preview Abstract] 
Tuesday, November 21, 2017 9:31AM  9:44AM 
M28.00008: Waveletbased regularization of the Galerkin truncated threedimensional incompressible Euler equations Marie Farge, Naoya Okamoto, Kai Schneider, Katsunori Yoshimatsu We present numerical simulations of the threedimensional Galerkin truncated incompressible Euler equations that we integrate in time while regularizing the solution by applying a waveletbased denoising. For this, at each time step, the vorticity field is decomposed into wavelet coefficients, that are split into strong and weak coefficients, before reconstructing them in physical space to obtain the corresponding coherent and incoherent vorticities. Both components are multiscale and orthogonal to each other. Then, by using the BiotSavart kernel, one obtains the coherent and incoherent velocities. Advancing the coherent flow in time, while filtering out the noiselike incoherent flow, models turbulent dissipation and corresponds to an adaptive regularization. In order to track the flow evolution in both space and scale, a safety zone is added in wavelet coefficient space to the coherent wavelet coefficients. It is shown that the coherent flow indeed exhibits an intermittent nonlinear dynamics and a $k^{5/3}$ energy spectrum, where $k$ is the wavenumber, characteristic of turbulent flows. Finally, we compare the dynamical and statistical properties of Euler flows subjected to dissipative, hyperdissipative, dispersive (EulerVoigt) and waveletbased regularizations. [Preview Abstract] 
Tuesday, November 21, 2017 9:44AM  9:57AM 
M28.00009: Turbulence and secondary motions in square duct flow 
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