Embedded LES Using PANS

Peng

2013

AIAA Journal

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An embedded LES modelling approach is explored and verified using the PANS (Partially Averaged Navier-Stokes) model as a platform. With the same base model, the turbulence-resolving LES region is embedded by setting the PANS model coefficient to f k < 1 as distinguished from its neighboring RANS region, where f k = 1 is specified. The embedded LES approach is verified in computations of a turbulent channel flow and a turbulent flow over a hump. Emphasis is placed on the impact of turbulent conditions at the RANS-LES interface using anisotropic velocity fluctuations generated from synthetic turbulence. The effect of the spanwise size of the computational domain is investigated.It is shown that the embedded LES method based on the PANS modelling approach is computationally feasible and able to provide reasonable turbulence-resolving predictions in the embedded LES region. The WALE (Wall-adapting local eddy-viscosity) model is also evaluated for the hump flow and it is found that its performance is worse than that of the the LRN (Low-Reynolds Number) PANS model when the results are compared with experiments.

Section: Vb Hump Flowsupporting

confidence: 71%

“…28 The upwinding is used because in Ref. 29 it was found that pure central differencing gave rise to unphysical resolved stresses near the inlet. The…”

Section: Methodsmentioning

confidence: 99%

Section: Vb Hump Flowmentioning

confidence: 99%

See 1 more Smart Citation

Embedded Large-Eddy Simulation Using the Partially Averaged Navier–Stokes Model

Peng

2013

AIAA Journal

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“…A blend of the two discretization schemes was motivated by a previous investigation of the hump flow by Davidson and Peng,22 where it was shown that 100% central differencing gave unphysical fluctuations, especially in the interface region. The turbulent transport equations were discretized using a first order hybrid scheme.…”

Section: Ivd Hump Flowmentioning

confidence: 98%

Hybrid RANS-LES Modeling Using a Low-Reynolds-Number k-ω Based Model

Arvidson

52nd Aerospace Sciences Meeting

Peng

2014

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Hybrid RANS-LES modeling is proposed using a Low-Reynold-Number (LRN) k − ω model. The model is demonstrated in a zonal RANS-LES approach and in an embedded LES approach. The model is calibrated and evaluated using Decaying Homogeneous Isotropic Turbulence (DHIT), turbulent channel flow and turbulent flow over a hump. The effect of different LES length scales on log-layer mismatch and turbulence resolving capability is demonstrated using the proposed model. Interface conditions are proposed in the embedded LES approach in order to reduce the grey area zone in the LES domain downstream of the RANS region. To further improve the development of turbulence resolving flow in the LES region downstream of the interface, anisotropic turbulent velocity fluctuations from synthetic turbulence are added. The hybrid RANS-LES modeling approaches that are presented, using the LRN k − ω based model, show that predictions of turbulence resolving flows are in reasonable agreement with experimental data and DNS data. Moreover, the choice of the LES length scale using the proposed model is shown to be of great importance in reducing the log-layer mismatch.

“…where u ′ i,synt denotes anisotropic synthetic fluctuations that were obtained using the same procedure as in [10]. In the present work, contrary to [10], the synthetic fluctuations are scaled with k RAN S /k RAN S,max . The inlet modelled turbulent kinetic energy and its dissipation are computed as [10].…”

Section: Boundary Layer Flowmentioning

confidence: 99%

Large Eddy Simulation of Heat Transfer in Boundary Layer and Backstep Flow Using PANS

Proceeding of THMT-12. Proceedings of the Seventh International Symposium on Turbulence, Heat and Mass Transfer Palermo, Italy,

2012

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Developing boundary layer flow and the flow over a backward-facing step are studied here. The LRN PANS k − ε [1] and the WALE turbulence model [2] are used as SGS models. The PANS (Partially Averaged-Navier-Stokes) modelling approach [3, 4] is a modified k − ε model that can operate in both RANS and LES mode. An extension of PANS based on a four-equation k − ε − ζ − f model was recently proposed [5]. Synthetic, anisotropic, turbulent fluctuations are prescribed at the inlet to trigger the momentum equations into turbulenceresolving mode. The effect of the amplitude of the synthetic fluctuations is investigated. Different values of f k are used. Two different discretization approaches are compared: 100% central differencing (CDS) or 95% CDS and 5% van Leer second-order bounded upwinding scheme. One 2D RANS simulation using the k − ω SST model is made for the backstep flow. A detailed comparison is made between 2D RANS and PANS including an analysis of the balancing terms in the momentum and temperature equations.