Law of boundary shear in open rectangular channels with uniform roughness

In accordance with the characteristics of the rectangular prismatic channel, the flow in the channel was divided into two parts, the bed part and the wall part. On the basis of general principles of mechanics, the area relation between the bed part and the wall part was described. A formula for determining the shear acting on the bed and the walls in rectangular channels was derived, which has a simple form and is related to the ratio of the width to the depth. The difference between the calculated value with the presented formula and the data published was illustrated to be less than that with other formulas, which shows that the formula is reasonable and can model the flow in the rectangular prismatic channel with higher accuracy and reliability.