When a vertical liquid jet impinges on a horizontal flat plate, at a certain distance from the location of impingement, the depth and velocity of the liquid change and a circular hydraulic jump is formed. The importance of this phenomenon in certain industries has motivated continued quest for more thorough knowledge of the parameters affecting it. Previous research has shown that physical parameters, such as flow rate, jet diameter and geometry of target plate, significantly affect the size and shape of hydraulic jumps. In this study, the effect of target plate roughness on the parameters of circular hydraulic jumps is experimentally investigated. The results show that adding roughness to the target plate leads to an increase in hydraulic jump radius. Furthermore, utilizing the results obtained from the experiments, an empirical law is proposed which determines the hydraulic jump radius and fluid height downstream of the jump position for a given surface roughness of target plate. One of the best-known models for the characterization of the behavior of circular hydraulic jumps is the Bush and Aristoff’s model, which is presented as a curve for smooth surfaces. Since the effect of roughness of target plate surface is ignored in the Bush and Arisstof’s model, the results obtained in this investigation are further used, for the first time, to improve this model for different degrees of surface roughness.

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