Spatially Variable Thresholding for Stochastic Coherent Adaptive LES

Nejadmalayeri, Alireza; Vasilyev, Oleg V.; Vezolainen, Alexei; Stefano, Giuliano De

doi:10.1007/978-94-007-2482-2_16

ERCOFTAC Series

2011

DOI: 10.1007/978-94-007-2482-2_16

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Spatially Variable Thresholding for Stochastic Coherent Adaptive LES

Alireza Nejadmalayeri

Oleg V. Vasilyev²,

Alexei Vezolainen³

et al.

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Cited by 2 publications

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“…The same volume-averaged relaxation time scale τ −1 = |S > ij | has been successfully tested for the present space-time-varying methodology with linear interpolation (5.2) in Nejadmalayeri et al (2011). Numerical simulations of linearly forced homogeneous turbulence, where the turbulent resolution is maintained at different prescribed goal values for many eddy turnover times, have been conducted.…”

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Fully adaptive turbulence simulations based on Lagrangian spatio-temporally varying wavelet thresholding

Nejadmalayeri

Vezolainen

Stefano³

et al. 2014

J. Fluid Mech.

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A new framework for spatio-temporally adaptive turbulence simulations is proposed. The method is based on a variable-fidelity representation that tightly integrates numerics and modelling of subgrid-scale turbulence and aims to capture the flow physics on a near-optimal adaptive mesh. The integration is achieved by combining hierarchical wavelet-based computational modelling with spatially and temporally varying wavelet threshold filtering. The proposed approach provides automatic smooth transition from directly resolving all flow physics to capturing only the energetic/coherent structures, which leads to a dynamically adaptive variable-fidelity approach. The self-regulating continuous switch between different fidelity regimes is accomplished through a two-way feedback mechanism between the modelled dissipation and the local grid resolution, which is based on spatio-temporal variation of the wavelet filtering threshold. The proposed methodology systematically accounts for and exploits the spatial and temporal intermittency of turbulence. Thus, it overcomes the major limitation of all existing wavelet-based multi-resolution techniques, namely, the use of a global thresholding criterion. The procedure consists of tracking the wavelet thresholding factor within a Lagrangian frame by exploiting a Lagrangian path-line diffusive averaging approach, based on either interpolation along characteristics or direct solution of the corresponding evolution equation. This new methodology is tested for linearly forced homogeneous turbulence at different Reynolds numbers and provides very promising results on a benchmark with time-varying prescribed level of turbulence resolution.

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confidence: 99%

Fully adaptive turbulence simulations based on Lagrangian spatio-temporally varying wavelet thresholding

Nejadmalayeri

Vezolainen

Stefano³

et al. 2014

J. Fluid Mech.

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Reynolds number scaling of coherent vortex simulation and stochastic coherent adaptive large eddy simulation

2013

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In view of the ongoing longtime pursuit of numerical approaches that can capture important flow physics of high Reynolds number flows with fewest degrees of freedom, two important wavelet-based multi-resolution schemes are thoroughly examined, namely, the Coherent Vortex Simulation (CVS) and the Stochastic Coherent Adaptive Large Eddy Simulation (SCALES) with constant and spatially/temporarily variable thresholding. Reynolds number scaling of active spatial modes for CVS and SCALES of linearly forced homogeneous turbulence at high Reynolds numbers is investigated in dynamic study for the first time. This dynamic computational complexity study demonstrates that wavelet-based methods can capture flow-physics while using substantially fewer degrees of freedom than both direct numerical simulation and marginally resolved LES with the same level of fidelity or turbulence resolution, defined as ratio of subgrid scale and the total dissipations. The study provides four important observations: (1) the linear Reynolds number scaling of energy containing structures at a fixed level of kinetic energy, (2) small, close to unity, fractal dimension for constant-threshold CVS and SCALES simulations, (3) constant, close to two, fractal dimension for constant-dissipation SCALES that is insensitive to the level of fidelity, and (4) faster than quadratic decay of the compression ratio as a function of turbulence resolution. The very promising slope for Reynolds number scaling of CVS and SCALES demonstrates the potential of the wavelet-based methodologies for hierarchical multiscale space/time adaptive variable fidelity simulations of high Reynolds number turbulent flows.

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Spatially Variable Thresholding for Stochastic Coherent Adaptive LES

Cited by 2 publications

References 8 publications

Fully adaptive turbulence simulations based on Lagrangian spatio-temporally varying wavelet thresholding

Fully adaptive turbulence simulations based on Lagrangian spatio-temporally varying wavelet thresholding

Reynolds number scaling of coherent vortex simulation and stochastic coherent adaptive large eddy simulation

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