Effect of Irregular Surface in a Turbulent Channel
The effect of highly irregular surfaces in a turbulent channel is studied through DNS through the use of the immersed boundary method to reproduce complex surfaces. The height of the surfaces analyzed is proportional to the streamwise velocity component u or the pressure p in a wall parallel plane of a smooth channel at \(y^+=12\). The surface with height proportional to u is drag reducing, that proportional to p is drag increasing. The relative magnitude of the friction components allows to identify the type of roughness as k-type, since the form drag is larger than the viscous drag. An additional surface has been obtained by smoothing a regular geometry made of staggered cubes. In this case, the resistance is doubled, and the form drag is much larger than the viscous drag.
KeywordsTurbulent Kinetic Energy Turbulent Viscosity Roughness Element Viscous Drag Immerse Boundary Method