Hydrodynamic Forces on Spherical Roughness Elements

The purpose of this paper is to study the charactristics of fluid forces acting on spherical roughness elements which placed densely and sparsely. By measuring the velocity distribution above the roughness elements, it is possible to determine the shearing stress on the rough wall with the aid of the logarithmic formula and hence the equivalent roughness length. On the other hand, Drag Force and Lift Force were calcurated from the surface pressure of the roughness elements which were measured directly. The integrated mean shear values have been compared with those estimated from directry measured Drag Force and the energy gradient.