Ansys

ANSYS EXERCISE – ANSYS 8.1 Flow Over a Flat Plate Copyright 2001-2005, John R. Baker John R. Baker; phone: 270-534-3114; email: jbaker@engr.uky.edu

This exercise is intended only as an educational tool to assist those who wish to learn how to use ANSYS. It is not intended to be used as a guide for determining suitable modeling methods for any application. The author assumes no responsibilityfor the use of any of the information in this tutorial. There has been no formal quality control process applied to this tutorial, so there is certainly no guarantee that there are not mistakes on the following pages. The author would appreciate feedback at the email address above if mistakes are discovered in this tutorial.

In this exercise, you will solve the classical flat plate 2-D airflowproblem, illustrated below, using ANSYS. The problem is adapted from the textbook, Fundamentals of Fluid Mechanics, by Munson, Young, and Okiishi. The airflow velocity for flow over the flat plate will be solved for, based on the specified velocity and pressure boundary conditions, and the plate dimensions. Step-by-step instructions are provided beginning on the following page. Notes: The fluidis air, with density, ρ=1.23 kg/m3, and dynamic viscosity, μ =1.79E-5 N-s/m2. The plate is 1 m long, as shown, and is very thin. It will be modeled with a thickness of 0.001 m. The plate is modeled in a square field, with edge lengths of 2 m. The 2 m edge length dimensions are arbitrary. These lengths are chosen large enough such that the effects of the flat plate on the flow are capturedcompletely within the square field. Also, the flow velocity in all directions is zero along the sides of the flat plate.

Atmospheric Pressure 2m

Velocity=0.072764 m/s

1m 2m

The

steps that will

Atmospheric Pressure 1

be followed, after launching ANSYS, are: Preprocessing: 1. Change Preferences 2. Change Jobname. 3. Define element type. (Fluid141 element, which is a 2-D element forfluid analysis.) 4. Define the fluid. (Air – SI Units.) 5. Create keypoints. 6. Create areas. 7. Specify meshing controls / Mesh the areas to create nodes and elements. 8. Zoom in to see flat plate region (optional). Solution: 9. Specify boundary conditions. 10. Specify number of solution iterations. 11. Solve. Postprocessing: 11. Plot the x-direction velocity (VX) distribution. 12. List VX atNodes. Exit 13. Exit the ANSYS program, saving all data.
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Notes: • • It is assumed in this tutorial that the user has already launched ANSYS and is working in the Graphical User Interface (GUI). The menu picks needed to perform all required tasks are specified in italics in the stepby-step instructions below. It issometimes more convenient to enter certain commands directly at the command line. The method of direct command line entry, however, is not emphasized in this exercise. Primarily, in this exercise, the analysis will be performed using menu picks from the ANSYS Graphical User Interface.

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SUGGESTION: As you work through this exercise, on the ANSYS Toolbar click on “SAVE_DB” often!

At anypoint, if you want to resume from the previous time the model was saved, simply click on “RESUM_DB” on this same Toolbar. Any information entered since the last save will be lost, but this is a nice feature in the event that you make an input mistake, and are unsure of how to correct it.

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Note: Most of the required tasks are performed using menu picks from the ANSYS GUI, as specified initalics in the step-by-step instructions below. It is sometimes more convenient, however, to enter certain commands directly at the command line. The command line is seen on the screen.

The Main Menu is on the left side of the screen. The method of direct command line entry is used in some cases in this exercise, whenever this method seems more convenient than using menu picks. Often, as an...