One-Equation Subgrid Scale Model Using Dynamic Procedure for the Energy Production

2005 ◽  
Vol 73 (3) ◽  
pp. 368-373 ◽  
Author(s):  
Takeo Kajishima ◽  
Takayuki Nomachi
Keyword(s):  
Transport Equation ◽  
Plane Channel ◽  
Suction Side ◽  
Scale Model ◽  
Subgrid Scale ◽  
Production Term ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Fully Developed Turbulent Flow ◽  
Subgrid Scale Model

The transport equation of subgrid scale (SGS) kinetic energy, KSGS, is used for the large-eddy simulation (LES), considering its consistency with dynamic procedure. The dynamically determined parameter is suitable for describing the energy transfer from resolved turbulence to SGS portion. Thus the procedure is applied to the production term in the transport equation of KSGS, while the eddy viscosity in the filtered equation of motion is determined indirectly through KSGS. The statistically derived model for KSGS equation is adopted for the basis of our improvement. Computational examination has been conducted for fully developed turbulent flow in a plane channel. Agreement with DNS database was satisfactory. Moreover, in a channel on solid body rotation, our model reasonably reproduced the decay of SGS turbulence in the vicinity of the suction side.

One-Equation Subgrid Scale Model Using Dynamic Procedure for the Energy Production

2003 ◽  
Author(s):  
Takeo Kajishima ◽  
Takayuki Nomachi
Keyword(s):  
Energy Transfer ◽  
Transport Equation ◽  
Plane Channel ◽  
Scale Model ◽  
Subgrid Scale ◽  
Production Term ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Fully Developed Turbulent Flow ◽  
Subgrid Scale Model

The transport equation of subgrid scale (SGS) kinetic energy, KSGS, is used for the large-eddy simulation (LES), considering its possible consistency with dynamic procedure. The smallest scale portion in computationally resolved turbulence, which is estimated in the dynamic model, has closer relationship with largest scale in SGS. Therefore the dynamically determined parameter is more suitable for describing the energy transfer between resolved and SGS turbulence, rather than the energy dissipation through the SGS eddy-viscosity in the filtered equation of motion. Such an energy transfer is represented by the production term in the transport equation of KSGS in our model. Computational examination has been conducted for fully developed turbulent flow in a plane channel. Agreement with DNS database was fine and it was improved by refining the grid.

Large-Eddy Simulation of Flow in a Low-Pressure Turbine Cascade

2012 ◽  
Author(s):  
Gorazd Medic ◽  
Om Sharma
Keyword(s):  
Reynolds Number ◽  
Turbulence Intensity ◽  
Free Stream ◽  
Reynolds Numbers ◽  
Scale Model ◽  
Subgrid Scale ◽  
Low Pressure Turbine ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Subgrid Scale Model

Flow over three low-pressure turbine airfoils presented in [1] is analyzed for a range of Reynolds numbers (30,000 to 150,000) by means of large-eddy simulation. Baseline computational grid for these 2D linear cascade configurations consisted of 35 millions cells, and additional finer grids of 70 millions cells were used for grid sensitivity studies. For these low Reynolds number flows, this represents a quasi-DNS resolution which minimizes the role of the subgrid-scale model — however, WALE subgrid-scale model [7] was still employed. The configurations were analyzed for low free-stream turbulence intensity, as well as for 4% turbulence intensity at free-stream. Laminar separation exists on the suction side, and, depending on the Reynolds number, the flow at the outer edge of the separation either transitions, and the separation closes before the trailing edge, or not. Detailed comparisons to measurements are presented for computed surface pressure and total pressure losses over the range of Reynolds numbers for all three airfoils; these show that LES analyses are able to capture the main trends across all three geometries.

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