Falling Objects into Water Simulation, Dynamic Mesh, ANSYS Fluent Training

Description

In this project, the fluid flow around two cubes falling into the water by the dynamic mesh method is simulated by ANSYS Fluent software. We perform this CFD project and investigate it by CFD analysis.

The present model is designed in two dimensions using Design Modeler software. Two cubes are placed inside a square domain and are supposed to fall into the fluid due to gravity acceleration.

The meshing of the model has been done using ANSYS Meshing software. Moreover, the element number is 8727.

Also, the transient solver has been enabled due to the dynamic mesh option.

Falling Objects Methodology

In problems where the location and shape of mesh cells change, it is mandatory to use the dynamic mesh model to prevent the extreme deterioration of elements’ quality.

Smoothing and remeshing methods create higher-quality elements when the previous ones may cause errors and are no longer useful to perform calculations with.

Two cubes are initially assumed to be kept still in the air, and when the simulation process starts, they will fall to collide with the free surface of water and air. As mentioned, the VOF Multiphase model option can simulate the two phases of water and air.

Furthermore, a UDF is used to impose cubes’ motion toward the water surface based on gravitational acceleration. Finally, the standard k-epsilon model is used to solve the turbulent fluid equations.

Falling Objects Conclusion

At the end of the solution process, two-dimensional contours related to the velocity, pressure, turbulent viscosity, and streamlines inside the computational domain are obtained.

As can be seen from the contours, due to the cubes’ movement and the sloshing phenomenon, the pressure along the cubes’ movement length has increased.

The pressure in the sharp corner of the tank and the cubes has its maximum value and a minimum value in the cubes’ vertical lengths (due to the separation of the flow because of the cubes’ movement in the fluid).

The kinetic energy contour also shows that the average kinetic energy due to vortices (vortices formed due to cubes’ movement in the fluid) around the cubes is higher than in other areas. The cubes’ movement has led to more turbulence in the flow and the formation of vortices.

We can easily see the wake areas in streamlines and vectors.