Study on wall shear stress in the flow with sand waves.

Abstract

According to previous investigations, it is well known that the phase lag between the form of river bed and wall shear stress is the essential factor in the formation of sand ripples or dunes. In the present paper, we calculate the phase lag mentioned above in two ways using cartesian and boundary layer co-ordinates.The obtained results are;(1) The phase lag shows a peak value in a range of wave numbers of sand waves.(2) The phase lag of wall shear stress calculated in boundary layer co-ordinate shows the better fitting to the expremental values than in cartesian ones.(3) In case of rough baundary, the distribution of phase lag dose not reveal a peak in wave number domain.