Description

Given the inlet flow (Q), the upstream and throat diameters (D1, D2), and the upstream piezometric head (P1/γ), this computes the velocity heads at sections 1 and 2, the piezometric heads at the throat (P2/γ) and downstream (P3/γ), and the head losses in the nozzle (hf¹²) and diffuser (hf¹³).

Assumptions: steady, incompressible flow, same elevation reference (no elevation terms), empirical correlations for nozzle and diffuser losses.

Venturi

Equations

$$ \begin{aligned} A_1 &= \frac{\pi D_1^2}{4}, \quad A_2 = \frac{\pi D_2^2}{4} \ U_1 &= \frac{Q}{A_1}, \quad U_2 = \frac{Q}{A_2} \ h_f^{12} &= 0.15,\frac{U_2^2}{2g} \ h_f^{13} &= 2.5,\frac{U_2^2}{2g} \ \frac{P_2}{\gamma} &= \frac{P_1}{\gamma} + \frac{U_1^2}{2g} - \frac{U_2^2}{2g} - h_f^{12} \ \frac{P_3}{\gamma} &= \frac{P_1}{\gamma} - h_f^{13} \end{aligned} $$

Default input units: Q in L/s, D1 and D2 in mm; heads in m.

Inputs

Outputs