Setting Up Parabolic Velocity Profile for Fully Developed Flow Inlet in ANSYS Fluent 2D Simulation

In this comprehensive guide, you will learn how to create a parabolic velocity profile for a fully developed flow at the inlet in ANSYS Fluent 2D. This important step is crucial for achieving accurate and realistic simulations, especially in fluid dynamics studies. The guide covers the complete workflow from setting up the geometry to running and analyzing the simulation results.

Step 1: Prepare Your Geometry

The first step is to create the geometry that represents your flow domain. You can use ANSYS DesignModeler or any other CAD tool to create a 2D geometry. Ensure that the geometry is properly defined and that it accurately reflects the flow area you are studying.

Step 2: Define the Boundary Conditions

Open ANSYS Fluent and once your geometry is ready, proceed to the next step.

Mesh the Geometry: Generate a suitable mesh for your domain. The quality of the mesh significantly affects the accuracy of the simulation. Ensure that the mesh is fine enough to capture the important features of the flow.

Set Up the Solver: Choose the appropriate solver settings, either pressure-based or density-based, depending on the nature of the flow. This step is crucial as it defines the solver's behavior during the simulation process.

Step 3: Apply the Inlet Boundary Condition

Go to the Boundary Conditions panel in ANSYS Fluent.

Select the boundary that represents your inlet and set the type to Velocity Inlet.

Step 4: Define the Parabolic Velocity Profile

Since Fluent does not have a built-in option for parabolic profiles, you will need to write a User-Defined Function (UDF). The equation for a parabolic velocity profile in a fully developed flow is as follows:

[ uy U_{text{max}} left( 1 - left( frac{y}{R} right)^2 right) ]

Where:

( U_{text{max}} ) is the maximum velocity at the centerline. ( R ) is the radius or half the height for a rectangular channel. ( y ) is the distance from the centerline.

Example UDF Code

#include ""

DEFINE_PROFILE parabolic_inlet thread position
{
  real y, Umax  1.0 // Set the maximum velocity
  real R  0.5 // Adjust as per your geometry half height for rectangular
  face_t f
  BEGIN_F_LOOP f thread
  {
    y  F_CENTROID f thread[1] // Get the y-coordinate of the face centroid
    F_PROFILE f thread position  Umax * ( 1 - (y / R)**2 ) / R // Parabolic profile
  }
  END_F_LOOP f thread
}

Step 5: Configure Solver Settings

Set Solver Parameters: Configure the solver settings including time step iterations and convergence criteria as needed for your simulation. Proper setting of these parameters ensures that the simulation reaches a stable and accurate result.

Step 6: Run the Simulation

Initialize: Initialize the flow field to set the initial conditions.

Run Calculation: Start the simulation and monitor convergence. Ensure that the simulation is proceeding smoothly and that it converges to a stable state.

Step 7: Post-Processing

After the simulation completes, use ANSYS Fluent's post-processing tools to visualize and analyze the flow field. This step is crucial for understanding the behavior of the flow and validating the simulation results.

In conclusion, setting up a parabolic velocity profile for a fully developed flow in ANSYS Fluent 2D involves several key steps, from preparing the geometry to defining the boundary conditions and setting solver parameters. By following these steps, you can ensure that your simulations are as accurate and reliable as possible, providing valuable insights into fluid dynamics phenomena.