Ultimate Dimensions of Local Scour

Abstract

A mathematical method is presented for determining the ultimate dimensions of local scour from relatively short term measurement of the progression of scour with time. The method involves plotting the logarithm of the rate of change of the scour dimension against the logarithm of time. A hyperbolic curve is fitted to the plotted data, and the asymptote of the hyperbola is used to determine the ultimate scour dimension. A example is used to compare the hyperbolic logarithmic method with the linear logarithmic and linear semilogarithmic methods (in which the scour depth increases without limit) which require an estimate of the time required to reach a practical equilibrium. The hyperbolic logarithmic method predicts both the time progression of scour and the ultimate scour dimensions.