High-pressure water nozzle jets are important components of many industrial processes, from cutting and cleaning to fighting fires and hydraulic mining. These jets use the head of water under high pressure to do operations that need to be done with accuracy and force. To make these jets work better and more efficiently, you need to understand the fluid mechanics. This study goes into detail about the physics of high-pressure water nozzle jets. It looks at how they are made, work, and the physical rules governing how they act. The current water jet nozzle study relies on the reference paper entitled “ Study on the Influence Rule of High-Pressure Water Jet Nozzle Parameters on the Effect of Hydraulic Slotting [1]”.

• Reference [1]: Gu, Beifang, et al. “Study on the Influence Rule of High‐Pressure Water Jet Nozzle Parameters on the Effect of Hydraulic Slotting.” Geofluids1 (2022): 4510194.

Figure 1: Water Nozzle Jet CFD Simulation

Simulation Process

The model has a 60° contraction angle, a 10 mm contraction section, an 8 mm straight column section, a 2 mm nozzle outlet diameter, and a 20 MPa water pressure at the nozzle opening. Quadrilateral (Structured) grids are used with numerical models (see Fig.2). Importantly, the axisymmetric method drastically decreases the computational cost and is compatible because of symmetric flow in high-pressure water nozzle jets.

Figure 2: Water nozzle jet configuration [1]

Post-processing

The high-pressure water nozzle jet’s analysis data gives us important information about how it flows and how it works. A contour of the turbulence intensity within the jet is shown in Figure 3. This gives a clear picture of how the flow behaves as it leaves the nozzle and moves downstream. From blue (low turbulence) to red (high turbulence), the color scale makes it easy to see how the turbulence is spread out in the jet. As soon as the jet leaves the nozzle, the core has the most turbulence, which is shown by the red and orange areas. The heart of high turbulence goes down a long way, and as it gets farther downstream, the green and blue hues show areas of lower turbulence. This high-turbulence core means that there is a lot of mixing and energy loss in the middle of the jet, which is important for situations where the water stream needs to hit something hard or spread out widely.

Figure 3: Turbulent Intensity of water nozzle jet CFD simulation

Interestingly, the blue areas around the center core show that the edges of the jet have much less turbulent flow. This pattern indicates a shear layer between the fast jet and the fluid that is not moving. As you move downstream, the low-turbulence area slowly grows. This suggests that the surrounding fluid is being sucked into the jet and its energy is gradually being lost. Also, the uneven distribution of turbulence, which is especially visible further downstream, could be a sign of minor flaws in the design of the nozzle or the flow conditions that could be fixed in future improvements.