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An incoming canonical spatially developing turbulent boundary layer (SDTBL) over a 2-D curved hill is numerically investigated via the Reynolds-averaged Navier–Stokes (RANS) equations plus two eddy-viscosity models: the K−ω SST (henceforth SST) and the Spalart–Allmaras (henceforth SA) turbulence models. A spatially evolving thermal boundary layer has also been included, assuming temperature as a passive scalar (Pr = 0.71) and a turbulent Prandtl number, Prt, of 0.90 for wall-normal turbulent heat flux modeling. The complex flow with a combined strong adverse/favorable streamline curvature-driven pressure gradient caused by concave/convex surface curvatures has been replicated from wind-tunnel experiments from the literature, and the measured velocity and pressure fields have been used for validation purposes (the thermal field was not experimentally measured). Furthermore, direct numerical simulation (DNS) databases from the literature were also employed for the incoming turbulent flow assessment. Concerning first-order statistics, the SA model demonstrated a better agreement with experiments where the turbulent boundary layer remained attached, for instance, in Cp, Cf, and Us predictions. Conversely, the SST model has shown a slightly better match with experiments over the flow separation zone (in terms of Cp and Cf) and in Us profiles just upstream of the bubble. The Reynolds analogy, based on the St/(Cf/2) ratio, holds in zero-pressure gradient (ZPG) zones; however, it is significantly deteriorated by the presence of streamline curvature-driven pressure gradient, particularly due to concave wall curvature or adverse-pressure gradient (APG). In terms of second-order statistics, the SST model has better captured the positively correlated characteristics of u′ and v′ or positive Reynolds shear stresses ( > 0) inside the recirculating zone. Very strong APG induced outer secondary peaks in and turbulence production as well as an evident negative slope on the constant shear layer.
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Statistics of a Turbulent Boundary Layer Under a Favorable-Adverse Pressure Gradient
A statically deformable ceiling was used at the Turbulence Dynamic Research facility at the University of Illinois at Urbana-Champaign. This facility was used to impose static spatially varying pressure gradients in a favorable-adverse (FAPG) arrangement. This study focuses on the FPG region of this flowfield which experiences a rapid spatial variation of its pressure gradient over 6.2𝛿. Non-time-resolved particle imaging velocimetry data were captured for 6 pressure gradients and 6 Reynolds numbers. This manuscript focuses on 𝑅𝑒𝜏 = 953 and four pressure gradient cases that have maximum acceleration parameters of 𝐾𝑚𝑎𝑥 × 106 = 0, 2.43, 4.77, and 5.97. The Reynolds stresses and turbulent kinetic energy of the boundary layer were investigated. The results were analyzed for the occurrence of relaminarization and it was concluded that no relaminarization occurred in any of the cases. The Reynolds stresses showed behavior suggestive of an internal layer, including knee points in 𝑢′𝑢′. However, no conclusive evidence was found to support this hypothesis.
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- Award ID(s):
- 2339665
- PAR ID:
- 10648389
- Publisher / Repository:
- American Institute of Aeronautics and Astronautics
- Date Published:
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.2514/6.2025-2753
