Active model split hybrid RANS/LES

Haering, Sigfried; Oliver, Todd; Moser, Robert D.

doi:10.1103/physrevfluids.7.014603

Cited by 11 publications

(5 citation statements)

References 73 publications

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“…In particular, the modeled-stress depletion problem, the slow development of resolved motion after a RANS-to-LES transition, is caused by this imbalance [10,18]. This requires then empirical techniques to transfer energy from the modeled to the resolved scales and vice versa.…”

mentioning

confidence: 99%

Continuous Eddy Simulation vs. Resolution-Imposing Simulation Methods for Turbulent Flows

Fagbade,

Heinz

2024

Fluids

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The usual concept of simulation methods for turbulent flows is to impose a certain (partial) flow resolution. This concept becomes problematic away from limit regimes of no or an almost complete flow resolution: discrepancies between the imposed and actual flow resolution may imply an unreliable model behavior and high computational cost to compensate for simulation deficiencies. An exact mathematical approach based on variational analysis provides a solution to these problems. Minimal error continuous eddy simulation (CES) designed in this way enables simulations in which the model actively responds to variations in flow resolution by increasing or decreasing its contribution to the simulation as required. This paper presents the first application of CES methods to a moderately complex, relatively high Reynolds number turbulent flow simulation: the NASA wall-mounted hump flow. It is shown that CES performs equally well or better than almost resolving simulation methods at a little fraction of computational cost. Significant computational cost and performance advantages are reported in comparison to popular partially resolving simulation methods including detached eddy simulation and wall-modeled large eddy simulation. Characteristic features of the asymptotic flow structure are identified on the basis of CES simulations.

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mentioning

confidence: 99%

Continuous Eddy Simulation vs. Resolution-Imposing Simulation Methods for Turbulent Flows

Fagbade,

Heinz

2024

Fluids

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“…Hybrid methods are still in a state of constant improvement, and some of them are more forgiving of coarse grids than others. Techniques like Partially Averaged Navier-Stokes (PANS [69]) or the more recently established Active-Model Split [70] may contribute to making hybrid simulations more affordable for engineering purposes.…”

Section: Three-dimensional Separated Diffuser Simulationsmentioning

confidence: 99%

A Review of the Computational Studies on the Separated Subsonic Flow in Asymmetric Diffusers Focused on Turbulence Modeling Assessment

2023

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Separated turbulent diffuser flows have long been an object of experimental and computational investigations due to their wide use in engineering applications and fundamental importance for understanding turbulent effects. The accuracy of simulating such flows depends mainly on turbulence modeling subtleties, numerical method, and the correspondence between the boundary conditions and the experimental set-up. The current review of selected articles focuses on revealing some of the computational challenges that may occur while modeling asymmetric subsonic diffuser flows. These challenges include the influence of sidewalls on the separation, issues with grid convergence, and the definition of boundary conditions. Several known experimental test cases and attempts at simulating them are studied. The novelty of this paper is in the fact that it is focused on a specific type of diffusers (asymmetric and subsonic) and based on relatively recent data. It is concluded that for all the test cases considered, Reynolds stress models and hybrid eddy-resolving methods are the most appropriate tools for obtaining reasonable results.

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“…Such a model may not be strictly categorized as WMLES. WMLES can relax the grid resolution requirements in the wall-normal direction resulting in lower computational costs [18].…”

Section: Introductionmentioning

confidence: 99%

“…Perhaps the most popular hybrid LES/RANS model is detached eddy simulation (DES) [20], which can be categorized as a uniőed hybrid model. In uniőed hybrid models there is only one mesh and one solver, which switches or blends between LES and RANS in each grid cell (either predeőned or dynamic based on the local ŕow features [18]). Taking advantage of the fact that the structure of unsteady RANS and LES equations is the same, the main task of a hybrid model is to compute the Reynolds and residual stresses (or the eddy viscosity, if both models are based on the Boussinesq assumption) by blending or switching between the two.…”

Section: Introductionmentioning

confidence: 99%

“…Taking advantage of the fact that the structure of unsteady RANS and LES equations is the same, the main task of a hybrid model is to compute the Reynolds and residual stresses (or the eddy viscosity, if both models are based on the Boussinesq assumption) by blending or switching between the two. In such methods, the wall-normal direction should be resolved at least up to the buffer layer (for RANS to resolve the inner layer), but in the wall-parallel direction, the grid only resolves the geometry and the mean ŕow (in contrast to WMLES) [18].…”

Section: Introductionmentioning

confidence: 99%

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Loosely Coupled Under-Resolved LES/RANS Simulation Augmented by Sparse Near-Wall Measurement

Piroozmand,

Brenner,

Jenny

2023

Preprint

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We investigate scenarios, where only sparse wall shear stress measurements are available, while accurate wall shear stress and velocity profiles are sought. Applying discrete adjoint-based data assimilation, with only near-wall measurements, accurate wall shear stress profiles are achieved at the expense of unrealistic velocity profiles. We therefore add and employ internal reference data generated by performing a relatively cheap hybrid simulation. We modified the dual-mesh hybrid LES/RANS framework recently proposed by Xiao and Jenny~\cite{xiao12} by loosely coupling under-resolved LES in the interior with steady RANS near the walls. The framework was developed in OpenFOAM and tested for flow over periodic hills with Re = 10595. Results show that the devised framework outperforms conventional dual-mesh hybrid LES/RANS and standalone sparse wall-data assimilated RANS models.

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Active model split hybrid RANS/LES

Cited by 11 publications

References 73 publications

Continuous Eddy Simulation vs. Resolution-Imposing Simulation Methods for Turbulent Flows

Continuous Eddy Simulation vs. Resolution-Imposing Simulation Methods for Turbulent Flows

A Review of the Computational Studies on the Separated Subsonic Flow in Asymmetric Diffusers Focused on Turbulence Modeling Assessment

Loosely Coupled Under-Resolved LES/RANS Simulation Augmented by Sparse Near-Wall Measurement

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