Roughness strip is a necessary technology for wind tunnel experiment. In order to improve the accuracy and reliability of transition simulation, a new fixed transition technology based on the three-dimensional discrete roughness elements has been established. The configuration parameters of roughness elements are calculated theoretically and the formula and manufacturing processes of roughness elements are developed. Using two-dimensional airfoil and three-dimensional combination models, the transition and additional resistance characteristics of discrete roughness elements are studied. Finally, the scale effect of roughness elements is analyzed and the influence laws of height, diameter, and spacing on transition characteristics have been obtained through numerical calculation. The results of this study indicate that this new discrete roughness is better in transition and additional resistance performance than conventional grit roughness. The results obtained in this paper has created a more reliable and accurate fixed transition technology for wind tunnel experiment and provided some reference for cross-flow transition mechanism.
The influence of a porous, compliant layer with overlying discrete roughness elements as exhaust pipe wall on friction and heat transfer
