Carnegie Mellon Mechanical Engineering

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FEM/ANSYS ## Test F2: Flow Over a Baseball      Fluid #2: Flow Around A Baseball USING FLOTRAN

Introduction: In this example you will model air flow over a baseball.

Physical Problem: Compute and plot the velocity distribution over the baseball shown below.

Problem Description:

·         A Baseball is 7.48 cm in diameter. (radius of 3.74cm)

·         The flow velocity (of air) over the baseball is approximately 40 m/s.

·         Objective:

To plot the velocity profile around the ball.

To graph the velocity distribution above and below the ball.

·         You are required to hand in print outs for the above.

·         Figure: IMPORTANT: Convert all dimensions and forces into SI units.

·         Create the larger area, then the area defining the baseball.

·         Subtract the baseball area from the larger area.

·         Define the Element Properties as a 2D Air Element

·         Define the Material Properties of the Air Element (Density and Viscosity are the important qualities) Mesh the plate with a mesh size of 0.005 on the edges of the baseball, and 0.2 on the edges of the outer area. Apply Boundary Conditions (No Slip along the edges of the baseball, velocity along the left line of the large area, and Atmospheric Pressure (P=0 in ANSYS) along the top, right and bottom lines of the large area. Iterate 20 times and solve. (Ideally the iteration count would be at least several thousand times to make sure that the solution converges… but computational time dictates that in order to be able to solve the problem in a reasonable amount of time, the iteration number should be trimmed down to 20) Plot the Velocity distribution in the X and Y directions, this is the answer you should obtain with 20 iterations:

(Contour Plot)  (Vector Plot) 