Flow Analysis of Underwater Water Jet System Using Computational Fluid Dynamics and Particle Image Velocimetry

Abstract

The width and depth of excavation are important for the development of a water jet system for underwater surface excavation in the water. This is determined by the pressure distribution affecting the ground. Therefore, it is necessary to analyze the flow of the water jet, but it is difficult to grasp visually, and generally used sensors are difficult to use in water. To overcome this problem, the flow analysis was simulated by using Computational Fluid Dynamics(CFD), Particle Image Velocimetry(PIV) experiment was performed to confirm the accuracy of CFD and to visualize the nozzle flow. The CFD was simulated by using MIDAS NFX and various pressures of nozzle injection, velocity distribution and pressure distribution were analyzed. For the PIV experiment, the water jet system is installed at L22m x W3.5m x D3m water tank, and a 5W Nd-yag laser was installed at the surface of the water, and a high-speed camera was installed to capture the flow in the side observation field. And particles of 20 micrometer size were mixed in the water. In the results of the CFD simulations, the nozzle injection pressure which is the measurable velocity by the PIV system was selected, the nozzle flow was visualized and the velocity distribution was measured by using the PIV experiment. The velocity distribution measured by PIV is compared with the CFD - analyzed velocity distribution under the same conditions.