Hello all. I am new to this forum. I am an electrical engineer, and I am working on a system which requires me to calculate a flow rate. Once I know this, I can continue with the design. Since I am an electrical engineer, I have insufficient knowledge of fluid dynamics to know how to set up the necessary equation(s) to compute the needed information. That being stated, I will tell all that I can about the system variables, and hopefully if I have given enough info, I will get some assistance in setting up the equation. I have a cubic (6-sided) liquid reservoir which will contain hydrochloric acid (30% ~ density 1149 kg/m^3). The bottom side of this reservoir has a 1" (2.54cm) hose that is used to drain this tank. The hose is connected to a valve with a sharp-edged opening (orifice coefficient,Co, I assume is 1 (?)) which measures 3/8" (0.9525cm) in diameter. I need to calculate the time that it will take the tank to drain. For calculation purposes, say that the tank is 1m x 1m x 1m, and the tank is full (height of HCl = 1m). I feel that the height must be a variable for integration (i.e. dV/dy)...but I also want to know the height of HCl in the tank at any given time (i.e. dV/dt). I have been looking online for the answers all day, but my head is starting to hurt from all of the information that I am finding, and I think that I am making this way too complicated for myself. Any help is GREATLY appreciated.