Comparison of Theoretical and Measured Momentum Forces of Water Jets Deflected at Different Angles from the Attachment Profiles

Abstract

The aim of this study is designed to compare measured reactions and calculated momentum forces of water jets when aimed at a series of different profile attachments positioned on a balanced pivot with adjustable weights. The relationship between theoretical momentum and measured reaction forces was recorded as the water jets deflect at different angles from the attachment profiles. Measured reaction forces will be calculated by summing moments about the pivot using the weight that is required to keep the balance device level. Theoretical momentum forces were determined by recording mass flow rate, calculating velocities, and applying these values to the momentum equation. In the case of flat plate attachment measurements, 6mm and 4.5mm nozzle was found to be less consistent at approximately 60% and 55% respectively, due to the water jets not being horizontal when hitting the plate and losing forces to deflection that is not converted into thrust. In contrast, more than 98% consistent results were found corresponding to cup, 90° and 180° plate attachment measurements due to most of the jet flow being deflected back at the incoming flow and the majority of the fluid force was able to be captured, and converted to thrust. The study finding suggests that if the incoming flow can be directed back in the direction it came then the momentum force will be converted to thrust force in effect doubling the momentum force to give a higher reaction force.