Question

State the relationship between discharge rate and pressure in a hydraulic spray noule.

Answer 1

Flow through a pipe can be determined using the Darcy-Weisbach equation or one of the other equations for irreversible pressure drop. These equations are generally restricted to small changes in density, so if you have a gas, the density change needs to be less than about 20% for the equations to be accurate. For density changes in excess of that, we generally break up the pipe into sections and recalculate properties as the pressure changes. The DW equation is: where hf is the head loss due to friction (SI units: m); L is the length of the pipe (m); D is the hydraulic diameter of the pipe (for a pipe of circular section, this equals the internal diameter of the pipe) (m); V is the average velocity of the fluid flow, equal to the volumetric flow rate per unit cross-sectional wetted area (m/s); g is the loc