VOF to DPM, Water Jets Impingement CFD Simulation

VOF to DPM, Water Jets Impingement  CFD Simulation, ANSYS Fluent training

Description

The water jet impingement process includes directing high-velocity fluid jets onto a surface to remove heat from the surface or improve heat transmission. It’s used in various fields, from aerospace, food processing, metal forming, and electronic cooling.

Computational fluid dynamics (CFD) relies on simulations to better explain and enhance jet impingement processes. ANSYS Fluent provides VOF to DPM simulations to correctly describe the multiphase flow behavior and particle tracking in jet impingement. To capture the intricate interactions between the high-velocity jets, the VOF approach employs an accurate model of the fluid-air interface.

The DPM model allows the detection and tracking of droplets typically seen in jet impingement processes.

Engineers and researchers can better understand flow patterns, heat transfer rates, and particle trajectories in jet impingement processes using VOF to DPM simulations in ANSYS Fluent. This data can be used to optimize cooling methods, boost device functionality, increase heat exchanger efficiency, avoid metal from warping during the forming process, and ensure consistent heat transfer in the food industry.

In this project, the VOF-to-DPM model is used to model the transition of liquid bulk or lump into droplets generated due to the impingement of two jets. The jets are injected into the domain with a velocity of 1.5 m/s.

In conclusion, ANSYS Fluent VOF to DPM simulations are a powerful tool for researching and improving jet impingement processes across various industries.

The geometry is generated in Design Modeler and meshed in ANSYS Meshing with 72000 elements. The automatic mesh adaptation is a mandatory option that needs to be enabled. Of course, small mesh cells are unnecessary in the initial stage, where the jet is absent in the domain.

VOF to DPM,Water jets impingement methodology

In this project, the formation of droplets due to the impingement of two water jets is simulated. Different modules, including the VOF multiphase model and the DPM, are enabled to model such a process.

When enabling the two VOF multiphase and DPM models simultaneously, two transition mechanisms of DPM-to-VOF and VOF-to-DPM become available, which the user can use to switch between the Eulerian VOF model to discrete phase elements or vice versa.

When the water is injected into the domain, the mesh adaptation starts to refine the mesh cells over the water and air interface. Once the liquid lump is turned into droplets (i.e., the particles), the mesh cell size can return to its original size, as small-sized mesh cells are unnecessary to resolve their behavior.

Conclusion

As shown in the results, as the two jets impinge on each other, a planar surface of the liquid is formed. Meanwhile, some particles are also formed due to the intensity of the jet’s impact. As time goes by, the liquid surface starts to expand, and more particles are formed on the body of jets, accumulating over the expanded surface of the water in the middle of the domain. Their velocity starts to decrease as they near the liquid surface while they have different diameters.

Moreover, as shown in the image depicting the mesh inside the domain, it is obvious that the mesh cell size is much smaller on the interface of water and air than in other regions. This is since in order to capture the flow instabilities that cause droplet formation, the surface tension on the water-air interface must be calculated accurately. Otherwise, the droplet formation location, the droplet diameter, and their velocities would not be according to the real physics.