Water Flowing (Discharging) Steadily from a Tank 
Calculation and equations 

Register to enable "Calculate" button. Units in Steady State Tank Discharge calculator: cm=centimeter, ft=foot, gal=U.S. gallon, m=meter, min=minute, s=second. Either the free discharge orifice or the submerged orifice can be modeled. The equations are the same for both cases. A dropdown menu allows you to select circular or square orifice geometry. For a circular orifice, B is orifice diameter. For a square orifice, B is orifice width and height. A dropdown menu allows you to select an orifice type. Discharge coefficients for the four orifice types are built into the calculation. Userdefined discharge coefficients are permitted but be sure that C_{o}= C_{c}C_{v}. The calculation only checks to see if inputs are positive; we do not check to see if C_{o}= C_{c}C_{v}. Builtin values for orifice discharge coefficients Rounded
Sharpedged
Short tube
Borda
where: A = orifice area, B = orifice diameter or width and height, C_{c} = contraction coefficient, C_{v} = velocity coefficient, C_{o} = orifice coefficient = C_{c}C_{v}, g = acceleration due to gravity = 32.174 ft/s^{2} or 9.8066 m/s^{2}, H = head defined in diagrams above, Q = flow rate (discharge), V = horizontal velocity through orifice, X = horizontal trajectory, Y = vertical trajectory.
Streeter, V. L., E. G. Wylie, and K. W. Bedford. 1985. Fluid Mechanics. McGrawHill. 9ed.
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