The circular hydraulic jump in low gravity

Email alerting service here click or sign up in the box at the top right-hand corner of the article Receive free email alerts when new articles cite this article-An experimental study of the circular hydraulic jump (CHJ) was carried out to show how reducing gravity to 10 ¡ 2 times that of the Earth's normal gravity a¬ects the CHJ diameter and the downstream ®ow patterns. Water was the working ®uid. Measurements of the CHJ diameter and the shape of the free liquid surface across the jump were made in low gravity using the downstream ®uid height and the ®ow rate as the parameters. Comparisons are made with normal-gravity ®ow conditions. A drop tower was used to create low gravity. The measurements are compared with an existing theory for predicting how gravity a¬ects the CHJ diameter. Results show that the steady-state CHJ diameter is larger at low gravity than normal gravity. As the downstream ®uid height is increased, the CHJ diameter at normal gravity moves inward, but at low gravity the CHJ diameter does not show a similar in®uence of downstream ®uid height. The curvature across the CHJ is higher at normal gravity than at low gravity and the length of the transition zone from the upstream to downstream height increases as gravity is reduced. Waves in the downstream ®ow are observed for all low-gravity ®ow conditions but at normal gravity they were observed only for selected ®ow conditions, suggesting that the in®uence of surface tension and viscosity dominate at low gravity. Measured normal-gravity and low-gravity CHJ diameters were bounded by theoretical predictions which assume either fully developed or developing ®ow conditions for the upstream thin ­ lm.