Numerical simulation method of roughness induced transition

For the purpose of simulating roughness induced transition, the boundary conditions of turbulent dissipation rate and eddy viscosity for rough surface were added to Langtry's γ-Reθ transition model; furthermore, equivalent sand surface roughness height was introduced to rewrite the correlation equations of the transition momentum thickness Reynolds number, making it appropriate for roughness-induced transition. Numerical simulation was made by referring to the wind tunnel data of several rough flat plate experiments and variable-pressure-gradient plate experiment, in which the results were satisfactory. Main conclusions are made as follows: surface roughness will enhance the heat transfer, increase the skin friction coefficient and shift the transition position upstream in general compared with smooth cases; effects for natural transition is significant, as surface roughness of 0.15 mm could shift the transition position upstream about 40%; while affect for separating induced transition is weaker; with the increase of surface roughness, transition position and separating bubble position are shifted backwards a little, the strength of separating bubble becomes weaker while the friction coefficient increases. © 2016, Press of Chinese Journal of Aeronautics. All right reserved.