# hydraulic jump

What's a hydraulic jump?

Watch the video on the left.

### Determining the loss of specific energy in a hydraulic jump

At the hydraulic jump a supercritical discharge** Q** becomes subcritical again. The discharge depth **h** rises rapidly and increases after the hydraulic jump. Energy is dissipated at the hydraulic jump due to the resulting turbulence. However, the momentum is retained, which means that there are two sequent depths **h** for the same specific force **F**. The ratio of the sequent depths **h1** and **h2** is described by the following formula:

Using the given specifi c energy diagram and an analogue specifi c force diagram, it is a simple matter to determine the resulting specific energy loss **ΔE **graphically:

The discharge depth **h1** is entered in the specific energy diagram and the specific force diagram (points 1 and 2). To determine the discharge depth **h2** after the hydraulic jump, the sequent depth to** h1** is determined graphically in the specific force diagram (point 3). The specific forces **F1** in point 2 and **F2** in point 3 are equal (conservation of momentum). Then the discharge depth **h2** is entered in the specific energy diagram (point 4). The specific energies **E1** and **E2** are read in the diagram. The specific energy loss **ΔE** that occurs in the hydraulic jump is equal to the difference between the specific energies.

The resulting specific energy loss **ΔE** can also be calculated using the following formula: