Carnegie Mellon

Mechanical Engineering

Self-paced learning on the Web
FEM/ANSYS

 

Test F2: Flow Over a Baseball
Home Up Course Info Problems Students Reference

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)

bullet

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.

bullet

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.

bullet

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)

bullet

Plot the Velocity distribution in the X and Y directions, this is the answer you should obtain with 20 iterations:

 

(Contour Plot)

 

 

(Vector Plot) 

 

 

Home Up Course Info Problems Students Reference
Send mail to the Teaching Staff with questions or comments about this web site.