Surface Tension and the Hydraulic Jump

Circular Jumps and Crowns

Figure 1: A small circular jump. Figure 2: A large circular jump. Figure 3: A turbulent circular jump with a crown.

The circular hydraulic jump may arise when a fluid jet falling vertically at high Reynolds number strikes a horizontal plate. Fluid is expelled radially, and the layer generally thins until reaching a critical radius at which the layer depth increases abruptly. Predictions for the jump radius based on inviscid theory were presented by Rayleigh (1914). The dominant influence of fluid viscosity on the jump radius was elucidated by Watson (1964), who developed an appropriate description of the boundary layer that develops from the lower boundary. We have recently examined the influence of surface tension on the circular hydraulic jump, both its size and stability, through a combined theoretical and experimental investigation. Figures 1 and 2 illustrate the laminar circular hydraulic jump, and Figure 3 shows a turbulent circular jump with a pronounced outer crown.

The Polygonal Regime

Figure 4: A three sided polygonal jump. Figure 5: A four sided polygonal jump. Figure 6: A five sided polygonal jump.