scholarly journals Inner-layer intensities for the flat-plate turbulent boundary layer combining a predictive wall-model with large-eddy simulations

2012 ◽  
Vol 24 (7) ◽  
pp. 075102 ◽  
Author(s):  
M. Inoue ◽  
R. Mathis ◽  
I. Marusic ◽  
D. I. Pullin
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Flat Plate ◽  
Large Eddy Simulations ◽  
Wall Model ◽  
Large Eddy

scholarly journals Large-eddy simulation of separation and reattachment of a flat plate turbulent boundary layer

2015 ◽  
Vol 785 ◽  
pp. 78-108 ◽  
Author(s):  
W. Cheng ◽  
D. I. Pullin ◽  
R. Samtaney
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Pressure Gradient ◽  
Flat Plate ◽  
Skin Friction ◽  
Separation Bubble ◽  
Reynolds Numbers ◽  
Wall Model ◽  
Large Eddy ◽  
Layer Flow

We present large-eddy simulations (LES) of separation and reattachment of a flat-plate turbulent boundary-layer flow. Instead of resolving the near wall region, we develop a two-dimensional virtual wall model which can calculate the time- and space-dependent skin-friction vector field at the wall, at the resolved scale. By combining the virtual-wall model with the stretched-vortex subgrid-scale (SGS) model, we construct a self-consistent framework for the LES of separating and reattaching turbulent wall-bounded flows at large Reynolds numbers. The present LES methodology is applied to two different experimental flows designed to produce separation/reattachment of a flat-plate turbulent boundary layer at medium Reynolds number $Re_{{\it\theta}}$ based on the momentum boundary-layer thickness ${\it\theta}$. Comparison with data from the first case at $Re_{{\it\theta}}=2000$ demonstrates the present capability for accurate calculation of the variation, with the streamwise co-ordinate up to separation, of the skin friction coefficient, $Re_{{\it\theta}}$, the boundary-layer shape factor and a non-dimensional pressure-gradient parameter. Additionally the main large-scale features of the separation bubble, including the mean streamwise velocity profiles, show good agreement with experiment. At the larger $Re_{{\it\theta}}=11\,000$ of the second case, the LES provides good postdiction of the measured skin-friction variation along the whole streamwise extent of the experiment, consisting of a very strong adverse pressure gradient leading to separation within the separation bubble itself, and in the recovering or reattachment region of strongly-favourable pressure gradient. Overall, the present two-dimensional wall model used in LES appears to be capable of capturing the quantitative features of a separation-reattachment turbulent boundary-layer flow at low to moderately large Reynolds numbers.

Large Eddy Simulations on Fan Shaped Film Cooling Hole with Upstream Boundary Layer Turbulence Effect Generated by Trip Strip

2021 ◽  
pp. 1-37
Author(s):  
Young Seok Kang ◽  
Sangook Jun ◽  
Dong-Ho Rhee
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Film Cooling ◽  
Main Flow ◽  
Large Eddy Simulations ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Flow ◽  
Large Eddy ◽  
Cooling Hole

Abstract Large eddy simulations on the well-known 7-7-7 fan shaped cooling hole were carried out. Like using a trip strip to create turbulent boundary layer in practical experiments, trip strips with different configurations were placed upstream of the cooling hole to investigate incoming turbulent boundary layer effect on the film cooling flow behavior. Without the trip, horseshoe vortex generated by laminar boundary layer induced laterally discharging cooling flow in the lateral direction. Meanwhile, the induced cooling flow formed high film cooling effectiveness region around the film cooling hole. When the incoming boundary flow was turbulent, laterally discharged cooling flow was influenced by the turbulent boundary layer to dissipate to the main flow and resultant high effectiveness region disappeared. Depending on the trip configuration, quantitative characteristics of boundary layer such as turbulent intensity, momentum thickness and shape factor were strongly affected. Some trip configurations resulted in fully developed turbulent boundary layer just before leading edge of the film cooling hole. In such cases, distribution of the film cooling effectiveness showed a reasonable agreement with available experimental data where the quantitative properties of the turbulent boundary layer were similar. However, when the trip was located too close to the film cooling hole, the separated and reattached flow did not develop into the stabilized turbulent boundary layer. Then strong turbulence intensity in the main flow boundary layer stimulated break down of the cooling flow vortex structure and early dissipation to the main flow. It resulted in restricted film cooling flow coverage.

High-Pass Filtered Eddy-Viscosity Models for Large-Eddy Simulations of Compressible Wall-Bounded Flows

2004 ◽  
Author(s):  
Steffen Stolz
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Eddy Viscosity ◽  
Large Eddy Simulations ◽  
Scale Model ◽  
Subgrid Scale ◽  
Smagorinsky Model ◽  
Viscosity Models ◽  
Large Eddy ◽  
High Pass

Eddy-viscosity models such as the Smagorinsky model [1] are the most often employed subgrid-scale (SGS) models for large-eddy simulations (LES). However, for a correct prediction of the viscous sublayer of wall-bounded turbulent flows van-Driest wall damping functions or a dynamic determination of the constant [2] have to be employed. Alternatively, high-pass filtered (HPF) quantities can be used instead of the full velocity field for the computation of the subgrid-scale model terms. This approach has been independently proposed by Vreman [3] and Stolz et al. [4]. In this contribution we consider LES of a spatially developing supersonic turbulent boundary layer at a Mach number of 2.5 and momentum-thickness Reynolds numbers at inflow of approximately 4500, using the HPF Smagorinsky model. The model is supplemented by a HPF eddy-diffusivity ansatz for the SGS heat flux in the energy equation. Turbulent inflow conditions are generated by a rescaling and recycling technique proposed by [5] where the mean and fluctuating part of the turbulent boundary layer at some distance downstream of inflow is rescaled and reintroduced at inflow.

Large-Eddy Simulations of Longitudinal Vortices Embedded in a Turbulent Boundary Layer

AIAA Journal ◽  
2006 ◽  
Vol 44 (12) ◽  
pp. 3032-3039 ◽  
Author(s):  
Donghyun You ◽  
Meng Wang ◽  
Rajat Mittal ◽  
Parviz Moin
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Large Eddy Simulations ◽  
Longitudinal Vortices ◽  
Large Eddy
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