The formation of hydraulic jump at the foot of a spillway is one of the common methods of energy dissipation because it destroys more than 90% of total energy by the turbulence produced in the jump.


When water flows over a spillway, it possesses a certain amount of energy known as the total energy. The hydraulic jump is a phenomenon that occurs when the supercritical flow transitions to subcritical flow. It is characterized by a sudden change in flow velocity, depth, and turbulence. The hydraulic jump is an effective method of energy dissipation and is commonly used at the foot of spillways to prevent erosion and damage.


The hydraulic jump is a process in which the supercritical flow rapidly undergoes a significant decrease in velocity, resulting in the dissipation of energy. This energy dissipation occurs primarily due to the turbulence produced in the jump. The turbulence causes intense mixing and friction between the water layers, converting the kinetic energy of the flow into heat energy. As a result, a significant portion of the total energy is destroyed.


The formation of a hydraulic jump leads to the generation of turbulent flow. Turbulence is characterized by chaotic and irregular motion of fluid particles. In the case of a hydraulic jump, the sudden change in flow velocity and depth creates vortices and eddies, which contribute to the turbulent flow. Turbulence enhances the mixing of water layers with different velocities, causing energy dissipation.


The hydraulic jump is a preferred method of energy dissipation compared to other methods due to its effectiveness in destroying a significant amount of energy. Let's compare the hydraulic jump with the other options mentioned in the question:

- Increasing the depth of flow (option B): While increasing the depth of flow can reduce the kinetic energy, it is not as efficient as the hydraulic jump. The hydraulic jump creates intense turbulence, resulting in a greater amount of energy dissipation.
- Action not understood (option C): This option suggests a lack of understanding of the hydraulic jump. However, the hydraulic jump is a well-studied phenomenon, and its energy dissipation mechanism is well-known.
- Decreasing the depth of flow (option D): This option is incorrect because the hydraulic jump actually increases the depth of flow. By rapidly increasing the flow depth, the hydraulic jump converts the excess kinetic energy into potential energy, leading to energy dissipation.


The formation of a hydraulic jump at the foot of a spillway is an effective method of energy dissipation because it destroys more than 90% of the total energy through the turbulence generated in the jump. The intense mixing and friction between water layers result in the conversion of kinetic energy into heat energy, preventing erosion and damage downstream.