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Review of State-Of-The-Art Achieved by NTS in Grey Area Mitigation

Review of State-Of-The-Art Achieved by NTS in Grey Area Mitigation. GAM-Tools We Have Today: Non-Zonal Approaches. Stochastic forcing proposed by NLR in the course of ATAAC Is incorporated into IDDES Shown to be helpful based on the Wall-Mounted Hump in ATAAC, but not sufficient

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Review of State-Of-The-Art Achieved by NTS in Grey Area Mitigation

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  1. Review of State-Of-The-Art Achieved by NTS in Grey Area Mitigation

  2. GAM-Tools We Have Today: Non-Zonal Approaches • Stochastic forcing proposed by NLR in the course of ATAAC • Is incorporated into IDDES • Shown to be helpful based on the Wall-Mounted Hump in ATAAC, but not sufficient • Better approaches are needed • One of possible directions of thinking is a modification of the sub-grid length scale accounting for nearly 2D character of initial region of separated shear layers and strong anisotropy of grids typical of this region (a variant is suggested in the works of ONERA) • Work in this direction was not initially planned on by NTS within Go4Hybrid but it may be that we’ll still do this in collaboration with CFDB (in addition to implementation and validation of new elements of PANS developed by FOI and CFBD initially planned on)

  3. GAM-Tools We Have Today: Zonal Approaches • NTS Synthetic Turbulence Generator (STG) developed within the • ATAAC and VALIANT Projects • It is proven to be rather efficient: Ensures a relaxation region about (2-3)d in both canonic shear flows and complex generic flows • Channel, ZPG BL, Plane Mixing Layer, Trailing edge, Wing-Flap, 2D Hump • Its “acoustically adapted” version ensures damping of spurious noise generated at the RANS-LES interface

  4. Examples of performance of NTS Synthetic Turbulence Generator (STG) Zonal M-SST based IDDES of ZPGBL z/L x/L • Plausible representation of turbulence: elongated vortices near the wall and nearly isotropic vortices in the outer region of BL • Based on Cf distribution, “adaptation region” required to establish “mature” turbulence downstream of the interface is about 2.5d 2.5d0

  5. Examples of performance of NTS Synthetic Turbulence Generator (STG) Zonal M-SST based IDDES of ZPGBL Symbols: DNS of Spalart Dashed lines: “Global” M-SST IDDES with recycling Solid lines: Zonal M-SST IDDES with STG • Rapid recovery of anisotropy of normal stresses

  6. Examples of performance of NTS Synthetic Turbulence Generator (STG) Zonal M-SST Based IDDES of Mixing Layer of Bell & Mehta (1990) U-contours • IDDES solution virtually does not • depend on the interface location • No visible discontinuities at 3 RANS-IDDES interfaces Vorticity-contours IDDES Sub-domain 1 IDDES Sub-domain 2 RANS-LES interface IDDES Sub-domain 3 Three above flow-fields pasted together

  7. Examples of performance of NTS Synthetic Turbulence Generator (STG) Zonal M-SST Based IDDES of Plane Spatial Shear Layer Longitudinal variation of shear layer momentum thickness Profiles of velocity, Reynolds shear stress, and kinetic energy in self-similar region

  8. Performance of Acoustically Adapted STG Version: TE Noise RANS-IDDES Interface Aerodynamic STG Acoustically adapted STG

  9. Drawbacks of NTS STG and Possible Improvements • Current version of the STG has some, mostly technological, • drawbacks / restrictions • Fully-coupled one-stage option requires overlapping grids capability not always available in industrial/commercial codes • Implementation of the STG on unstructured grids is not straightforward • A modified version of the STG is developed in the form of volume • sources in the RANS momentum equation and k - transport equation • Its a-version (with the volume source width of one cell) is tested and shown to be applicable with grids of arbitrary topology • Thorough assessment based on Go4Hybrid TC’s and, if needed, • further improvement of this approach will be carried out within • Go4Hybrid

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