Prediction of laminar, transitional and turbulent flow regimes, based on three-equation k-ω turbulence model

Abstract

A recently developed transitional model for boundary-layer flows has been examined on a flat plate and the well-known S809 wind turbine blade. Proposed numerical model tries to simulate streamwise fluctuations, induced by freestream turbulence, in pre-transitional boundary-layer flows by introducing an additional transport equation for laminar kinetic energy term. This new approach can be used for modeling of transitional flows which are exposed to both the freestream turbulence intensity and streamwise pressure gradient, which are known as the most dominant factors in occurrence of transition. Computational method of this model is based on the solution of the Reynolds averaged Navier-Stokes (RANS) equations and the eddy-viscosity concept. The model includes three transport equations of laminar kinetic energy, turbulent kinetic energy and dissipation rate frequency. The present model is capable of predicting either natural or bypass transitional mechanisms, which may occur in attached boundary-layer flows. In addition, the model can simulate transition in the separated free shear layers and the subsequent turbulent re-attachment to form a laminar separation bubble. Flat plate was exposed to different freestream turbulence intensities and streamwise pressure gradients. Wind turbine blade was examined under two different Reynolds numbers, with one of them suitable for the occurrence of laminar separation bubbles on its surfaces. To evaluate the performance of this new model in resolving transitional boundary-layer flows, final results have been compared to those obtained through application of conventional turbulence models. Comparison of final results for the flat plate and the S809 aerofoil with available experimental data show very close agreements.

Modeling, Integration, and Automation of Degradation to Generate Asset Lifespan Analytics Using

“…Unlike corrosion, which involves chemical reactions, erosion is the physical removal of tiny bits of the alloy by either the fluid or stream itself (fluid-or stream-induced erosion) or by the stream-borne particles (solid-particle erosion). Fluid flow is governed by two distinct regimes: the laminar-flow region and the turbulent-flow region (Taghavi-Zenouz et al, 2008). "When the flow is orderly and predictable, the flow pattern is often amenable to mathematical solutions.…”