Prediction of cavitation in orifice plates—A novel and simple rule-of-thumb

Abstract

New experiments have been carried out on the generic case of the flow through orifice plates. The aim has been to validate empirical correlations used for the prediction of cavitation. The new accurate experimental data base shows that earlier proposed empirical correlations work well for the prediction of cavitation, e.g., Tullis (1993), Miller (2009), and Nilsson (2011). Using the present data together with earlier data from Tullis (1993), it has been shown that, at the onset of cavitation, the ratio between the downstream and the upstream pressure over the orifice plate is a simple linear function of the orifice plate diameter ratio, β = d/D. This has been shown to hold independent of flowrate, downstream pressure, orifice diameter (for 0.4 < β < 0.8, which corresponds to a pressure loss coefficient 1 < ξ < 100) and boundary conditions (e.g., upstream pipe bends), at moderate temperatures and as long as the pressure drop is large compared to the saturation pressure. A novel and simple rule-of-thumb for when the cavitation becomes a problem (i.e., in between critical cavitation and incipient damage) has been demonstrated to be when the ratio between the downstream and the upstream pressure over the orifice plate equals the orifice plate diameter ratio.