Check Valve CFD Simulation, Dynamic Mesh

Description

This project is related to the numerical flow simulation through the Check Valve using ANSYS Fluent software. A check valve is a unidirectional valve that passes fluid in one direction but prevents no flow in the opposite direction.

This product is the third chapter of the Dynamic Mesh Training Course.

In this project, we considered a pipe in which water flows. We put a check valve in the water flow path in the pipe. We also put a seat valve behind this valve. This causes the valve to operate in one direction.

First, on the way, the fluid hits the valve and opens it. Then, when the inflow is interrupted, the fluid on the return path hits the valve again and closes it.

This project aims to model the check valve motion inside the pipe. As the valve inside the tube opens and closes, the mesh of the computational zone undergoes deformation over time.

We modeled the geometry of the project using Design Modeler software. The geometry corresponds to a horizontal pipe with a check valve. In the middle of this pipe, a simple valve with a seat valve is designed. Then we meshed the model with ANSYS Meshing software. The model mesh is unstructured, and the number of cells equals 14,586.

Check Valve Methodology

The Dynamic Mesh Model is used in this simulation. We generally use a dynamic mesh whenever we have a moving boundary or a deforming zone.

Here, a valve has a rotational motion inside a pipe. So this causes the mesh to deform over time.

The fluid flow inside the pipe causes the valve to move by hitting the valve. By applying the force of fluid flow, the valve starts to rotate around its central axis.

So we use six degrees of freedom (6 DOF) solver. The 6-DOF solver allows the object to move in six degrees (three degrees of freedom in translational motion and three degrees of freedom in rotational motion). This means that by defining data such as mass and inertia tensor, etc., we allow the solver to move the object.

In this simulation, the valve only rotates on its axis. So we have to limit the movement of the valve to one degree of freedom rotational motion.

Now, we must define the rotational motion of the valve. We have to define the boundary related to the valve walls as a Rigid Body; so that we define motion for these rigid bodies.

To define the movement of the valve, we use the motion defined by the 6-DOF solver.

According to the rotational motion of the valve as a rigid body, the mesh zone inside the tube is deformed. So, for this zone, we use the Deforming option.

Due to the nature of this modeling, flow behavior is time-dependent. Hence, we use the unsteady (Transient) solver.

We want the pipe to be empty of water flow at first. That is, there is only air in the inner space of the tube. Then the water flow enters the pipe. So in this simulation, we need two fluids.

Therefore, we use the Multiphase Model. Since the flow of water and air are separate and have a distinct separation boundary, we use the volume of fluid (VOF) multiphase model.

We aim to cut off the incoming water flow after a specific time to see the return of the flow and, consequently, the closing of the valve. We used an Execute Command to define the interruption of the input flow.

Check Valve Conclusion

After the solution, we obtained the contour of the mass fraction of water. In addition, we obtained an animation of the mass fraction of water.

The results show that the mechanism of the check valve is working correctly. First, the water flow enters the empty pipe, and applying force to the valve causes the valve to be open.

Then the incoming water flow is cut off. The return water flow by applying force to the valve causes the valve to close.