Drainers are a group of devices that move water from a dam lake to a downstream disposal point. This research aimed to determine the numerical and laboratory permeability coefficients in the lower discharge ducts. The physical model of ducts and valves created in the Soil Conservation and Watershed Management Research Center laboratory was utilized in this study and the relevant testing. The numerical discharge model was simulated using Flow 3D software to compare experimental and numerical results and prior results in this work. The findings revealed that variations in the permeability coefficient up to 50% opening of the service valve did not follow a predictable pattern but increased with increasing openness from 50% onwards. The flow rate via the duct was studied, and it was discovered that raising the opening of the valves increased the flow rate, which logically demonstrates high performance and is compatible with previous models. Compared to experimental data, the quantity of flow rate received from the software has a pretty acceptable accuracy, but the flow rate obtained from the program is always higher than the flow rate recorded in the laboratory. The proportion of mistakes varies between 2 and 16 percent for a single valve and 3 to 15 percent for combined operation, with most errors occurring at the lowest opening, i.e., 30 percent.
