comparison of different discharge estimation methods for sharp-crested semi-circular side weir under subcritical flow regimes

side weir is a flow control structure that used extensively in irrigation and drainage as well as sewer networks. throughout the present research, a study comprised of 162 experiments was done on sharp-crested semi-circular side weir. since the height in this side weir varies along its length, this feature enables it to more properly control flood than rectangular side weirs in various flood conditions. the governing differential equation of the circular side weir has no analytical solution, and thus it is necessary to use numerical methods to be solved. since numerical methods bear computational costs, normal weir equation along with linear assumption of water surface profile are employed in solving the problem. lastly, by doing three other experiments under completely different conditions from the former ones, it was found that the method of considering linear water surface profile is of less error in comparison with other methods employed in the current research.