Bulletin of the American Physical Society
65th Annual Meeting of the APS Division of Fluid Dynamics
Volume 57, Number 17
Sunday–Tuesday, November 18–20, 2012; San Diego, California
Session E22: Turbulence Modeling: LES |
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Chair: James McDonough, University of Kentucky Room: 30C |
Sunday, November 18, 2012 4:45PM - 4:58PM |
E22.00001: Compressible Explicitly Filtered Large-Eddy Simulation Subgrid-Scale Models Based on the Poor Man's Navier--Stokes Equations J.M. McDonough, J.P. Strodtbeck A single-parameter large-eddy simulation (LES) method for compressible flows that combines explicit filtering with a chaotic backscatter term based on the compressible ``poor man's'' Navier--Stokes (PMNS) equation (Strodtbeck {\it et al., Int.\ J.\ Bifur.\ and Chaos}, 2012) is presented and compared to direct numerical simulation (DNS) of homogeneous, isotropic, decaying turbulence in a periodic cube with a turbulent Mach number of 0.3 and Taylor micro-scale Reynolds number of 72. The DNS employed a $129^3$ mesh, and LES was run on a $65^3$ mesh. The backscatter is created by utilizing output from the PMNS equations as a multiplier on the high-pass filtered momentum to induce mixing, then using the results in a single-parameter linear forcing term that is simply added to the solution procedure. It is demonstrated that with a judicious choice of model parameter, the backscatter model is capable of enhancing small-scale turbulent flow structures and improving the flow statistics and spectral characteristics of the LES solution to more closely match the DNS results. [Preview Abstract] |
Sunday, November 18, 2012 4:58PM - 5:11PM |
E22.00002: Constrained Large Eddy Simulation of Wall-bounded Turbulent Flows with Massive Separations Zhenhua Xia, Yipeng Shi, Zuoli Xiao, Shiyi Chen Constrained Large-eddy Simulation (CLES) has~been recently developed to simulate turbulent flows with massive separations. Different from traditional large eddy simulation (LES) and hybrid RANS/LES approaches, the CLES simulates the whole flow domain by large eddy simulation while enforcing a Reynolds stress constraint on the subgrid-scale (SGS) stress models in the near-wall region. In this paper, we use the CLES method to simulate two separated flows, i.e. flow over periodic-hills and flow around NACA0021 airfoil at 60 degrees angle of attack. The results are compared with those from DES and other traditional simulation methods using the same grid resolution. In flow over periodic-hills, the results show that CLES can capture the mean separation location and reattachment location more accurately. In flow around NACA0021 airfoil at 60$^{\circ}$ angle of attack, CLES can estimate the pressure coefficients after separations more precisely. Furthermore, the computational cost of the CLES is almost the same as that of DES. We will also discuss the application of CLES for aerodynamic. [Preview Abstract] |
Sunday, November 18, 2012 5:11PM - 5:24PM |
E22.00003: Nonequilibrium energy spectrum in subgrid-scale one-equation model in LES Kiyosi Horiuti, Takahiro Tamaki The subgrid-scale (SGS) modeling in LES which accounts for effect of unsteadiness and nonequilibrium state is considered by employing the transport equation for the SGS energy (one-equation model). Perturbation expansion about the Kolmogorov -5/3 energy spectrum which constitutes a base equilibrium state in the inertial subrange yields -7/3 spectrum. These spectra are extracted in the DNS data, and their roles in generation of energy cascade have been revealed. The SGS energy spectrum which governs one-equation model is sought in a perturbative manner. Besides the base -5/3 spectrum assumed in the Smagorinsky model, -7/3 power component is derived, which is induced by temporal variations of SGS energy. We propose the nonequilibrium Smagorinsky model in which estimate of the SGS energy based on the -7/3 spectrum is added to the Smagorinsky model. Assessment in forced homogeneous isotropic turbulence showed that performance of the Smagorinsky and one-equation models for prediction of temporal variations of turbulence energy is not satisfactory, whereas improvement is achieved in the new model. This occurred because natural continuation of grid-scale spectrum, which contains both -5/3 and -7/3 components, into the SGS and associated energy transfer is established in the new model. [Preview Abstract] |
Sunday, November 18, 2012 5:24PM - 5:37PM |
E22.00004: ABSTRACT WITHDRAWN |
Sunday, November 18, 2012 5:37PM - 5:50PM |
E22.00005: ABSTRACT WITHDRAWN |
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