SAS – SST simulations of the flow and heat transfer inside a square ribbed duct with artificial forcing

Scale Resolving Simulations (SRS) are emerging as a promising compromise of cost and accuracy for industrial simulations of flows inside turbine blade cooling systems as they represent a necessary increase of accuracy with respect to Reynolds Averaged Navier Stokes (RANS) in the field. In this paper, several hybrid RANS-LES (Large Eddy Simulation) and SRS approaches are investigated. A Scale Adaptive Simulation (SAS) with spectrally calibrated artificial forcing is used to simulate flow inside a development section of a square duct with eight square equispaced ribs. Energy spectra, two-point correlations as well as other standard metrics are used to assess resolved content qualitatively as well as quantitatively. It is found that unmodified SST-SAS offers a marginal improvement over Unsteady RANS (URANS) for the present type of flow even on a LES-type grid and the solution is essentially steady. The artificial forcing used seems to trigger the resolving capability of the model and the solution is noticeably closer to experimental results while requiring minor extra computational demand. Effects of rotation are examined and it is found that the rotation appears to trigger the resolving mode of the unforced SAS model

Evaluation of the SST-SAS model for prediction of separated flow inside turbine internal cooling passages

The flow and heat transfer over a three-dimensional axisym-metric hill and rectangular ribbed duct is computed in order to evaluate the Shear Stress Transport - Scale Adaptive Simulation (SST-SAS) turbulence model. The study presented here is rele¬vant to turbine blade internal cooling passages and the aim is to establish whether SAS-SST is a viable alternative to other turbulence models for computations of such flows. The model investigated is based on Menter‘s modification to Rotta‘s k-kL model and comparison is made against experimental data as well as other models including some with scale resolving capability, such as LES, DES & hybrid LES-RANS. For the hill case the SAS model dramatically overpredicts the size of the separation bubble. The LES on the other hand proved to be more accurate even though the mesh is courser by LES standards. There is little improvement of SST-SAS compared with RANS. Broadly speaking all models predict streamwise ve¬locity profiles for the ribbed channel with reasonable accuracy. The cross-stream velocity is underpredicted by all models. Heat transfer prediction is more accurately predicted by LES than RANS, DES & SST-SAS on a mesh that is slightly coarser than required by LES standard, however it still exhibits significant er¬ror. It is concluded that more investigation of the SST-SAS model is required to more broadly assess its viability for industrial com¬putation

SAS – SST simulations of the flow and heat transfer inside a square ribbed duct with artificial forcing

Scale Resolving Simulations (SRS) are emerging as a promising compromise of cost and accuracy for industrial simulations of flows inside turbine blade cooling systems as they represent a necessary increase of accuracy with respect to Reynolds Averaged Navier Stokes (RANS) in the field. In this paper, several hybrid RANS-LES (Large Eddy Simulation) and SRS approaches are investigated. A Scale Adaptive Simulation (SAS) with spectrally calibrated artificial forcing is used to simulate flow inside a development section of a square duct with eight square equispaced ribs. Energy spectra, two-point correlations as well as other standard metrics are used to assess resolved content qualitatively as well as quantitatively. It is found that unmodified SST-SAS offers a marginal improvement over Unsteady RANS (URANS) for the present type of flow even on a LES-type grid and the solution is essentially steady. The artificial forcing used seems to trigger the resolving capability of the model and the solution is noticeably closer to experimental results while requiring minor extra computational demand. Effects of rotation are examined and it is found that the rotation appears to trigger the resolving mode of the unforced SAS model

Evaluation of the SST-SAS model for prediction of separated flow inside turbine internal cooling passages

The flow and heat transfer over a three-dimensional axisym-metric hill and rectangular ribbed duct is computed in order to evaluate the Shear Stress Transport - Scale Adaptive Simulation (SST-SAS) turbulence model. The study presented here is rele¬vant to turbine blade internal cooling passages and the aim is to establish whether SAS-SST is a viable alternative to other turbulence models for computations of such flows. The model investigated is based on Menter‘s modification to Rotta‘s k-kL model and comparison is made against experimental data as well as other models including some with scale resolving capability, such as LES, DES & hybrid LES-RANS. For the hill case the SAS model dramatically overpredicts the size of the separation bubble. The LES on the other hand proved to be more accurate even though the mesh is courser by LES standards. There is little improvement of SST-SAS compared with RANS. Broadly speaking all models predict streamwise ve¬locity profiles for the ribbed channel with reasonable accuracy. The cross-stream velocity is underpredicted by all models. Heat transfer prediction is more accurately predicted by LES than RANS, DES & SST-SAS on a mesh that is slightly coarser than required by LES standard, however it still exhibits significant er¬ror. It is concluded that more investigation of the SST-SAS model is required to more broadly assess its viability for industrial com¬putation