Analytical Determination of Form Friction Factor

Abstract

The form friction factors for an idealized series of two‐dimensional bedforms simulating a train of ripples or dunes in alluvial channels are obtained analytically by integrating the pressure along the bedform profiles. The roughness element is assumed to act independently so that the form friction factor can be obtained by analyzing the flow over a single bedform. The pressure distribution along the bedform is obtained by analyzing the incompressible, rotational inviscid flow over a theoretical ripple profile with the help of the Finite Element Method. A family of curves representing the relationship between form friction factor and relative depth with different bedform steepness ratios are numerically obtained. The comparison with the observed data shows a fair agreement.