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One of the key factors in simulating realistic wall-bounded flows at high Reynolds numbers is the selection of an appropriate turbulence model for the steady Reynolds Averaged Navier–Stokes equations (RANS) equations. In this investigation, the performance of several turbulence models was explored for the simulation of steady, compressible, turbulent flow on complex geometries (concave and convex surface curvatures) and unstructured grids. The turbulence models considered were the Spalart–Allmaras model, the Wilcox k- ω model and the Menter shear stress transport (SST) model. The FLITE3D flow solver was employed, which utilizes a stabilized finite volume method with discontinuity capturing. A numerical benchmarking of the different models was performed for classical Computational Fluid Dynamic (CFD) cases, such as supersonic flow over an isothermal flat plate, transonic flow over the RAE2822 airfoil, the ONERA M6 wing and a generic F15 aircraft configuration. Validation was performed by means of available experimental data from the literature as well as high spatial/temporal resolution Direct Numerical Simulation (DNS). For attached or mildly separated flows, the performance of all turbulence models was consistent. However, the contrary was observed in separated flows with recirculation zones. Particularly, the Menter SST model showed the best compromise between accurately describing the physics of the flow and numerical stability.
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Computational fluid dynamics-based modeling of liquefied soils
The residual shear strength of liquefied soil is a key parameter in evaluating liquefaction flow failures. Results from a series of dynamic centrifuge experiments where the shear strength of liquefied soil was inferred by measuring the force required to pull a thin metal plate (coupon) horizontally through the liquefied soil are assessed here using a computational fluid dynamics (CFD) based model. Viscosity is a key parameter for the Newtonian fluid constitutive model used in the simulations, and apparent viscosities of liquefied soil in the range of about 5,800 – 13,300 Pa·s were obtained when the CFD model was calibrated against coupons pulled through liquefied soil in dynamic centrifuge tests. These computational values agree reasonably with apparent viscosities of liquefied soil reported in the literature when the Reynold’s numbers exceeded 1.0. Importantly, the CFD simulations illustrated that in cases where Reynold’s numbers are < 1.0, apparent viscosities of liquefied soil back-calculated using simplistic closed-form solutions commonly applied in geotechnical literature are several orders of magnitude too large; and therefore, such closed-form solutions should not be used for these cases.
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- Award ID(s):
- 1728172
- PAR ID:
- 10104124
- Date Published:
- Journal Name:
- 7th International Conference on Earthquake Geotechnical Engineering
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
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