Direct Measurement of Bottom Shear Stresses in Open Channel Flows

Abstract

A high sensitive device for measuring the shearing stresses on the bottom of an open channel by means of the method of a direct balance is described. The noticeable features of the device are that a very small shear to 0.01 dyn/cm^2 in magnitude can be measured, the sensitivity adjustment can be easily made in wide extent and a complete linearity between the shear stress and the displacement of sensing element is assured. Estimations of the Karman's constant, those of a resistance coefficient in a flow with very mild hydraulic gradient and measurements of the power spectra of the bottom shear fluctuation are made with success.