Wind Tunnel Testing Interactive
Please note: the simulation below is best viewed on a desktop computer. It may take a few minutes for the simulation to load.
With this simulator you can investigate the process of wind tunnel testing by changing the conditions of a test of a representative wing model. You can look at surface pressure distributions, probe the flow field, and use several flow visualization techniques.
In wind tunnel testing, an engineer must first design and build a wind tunnel model with all of the appropriate instrumentation included. The model is then placed in the tunnel test section and air is blown over the model. Different diagnostic techniques may be employed during a wind tunnel test. The instrumentation records the desired information for the model designer. The engineer who conducts the wind tunnel test is not normally the same person who designed the model, but someone who is a specialist at wind tunnel operation. The data from the test normally goes to a third engineer who performs the necessary data reduction and produces performance plots for the initial engineer.
This program is designed to be interactive, so you have to work with the program. There are a variety of choices which you must make regarding the display of results by using a choice box. A choice box has a descriptive word displayed and an arrow at the right of the box. To make a choice, click on the arrow, hold down and drag to make your selection. The current values of the design variables are presented to you in boxes. By convention, a white box with black numbers is an input box and you can change the value of the number. A black box with yellow or green numbers is an output box and the value is computed by the program. To change the value in an input box, select the box by moving the cursor into the box and clicking the mouse, then backspace over the old number, enter a new number, then hit the Enter key on your keyboard. You must hit Enter to send the new value to the program. For most input variables you can also use a slider located next to the input box. Click on the slider bar, hold down and drag the slider bar to change values, or you can click on the arrows at either end of the slider.
If you experience difficulties when using the sliders to change variables, simply click away from the slider and then back to it. If the arrows on the end of the sliders disappear, click in the areas where the left and right arrow images should appear, and they should reappear.
The program screen is divided into five main parts:
- On the top left side of the screen is the View Window. The view window includes a graphic of a wing model in a wind tunnel. During the test, the view in the tunnel will change depending on your inputs. You can view either a solid model or a transparent model by selecting the buttons below the graphics. The yellow-lighted button is your selection.
- On the top right side of the screen is the Diagnostics Window for your model. You can choose to display either the surface pressure or velocity by selecting the button below the window. There are three lines plotted on the screen; the yellow line is the surface distribution of the flow variable on the lower surface of the model, the magenta line is the distribution on the upper surface, and the green line is the reference value for the free stream conditions.
- On the lower left side of the screen is the Input Panel. Details of the variables are given below. There are also some selection buttons for Flow Visualization. You can choose to display smoke traces, particle traces, or no trace in the view window by clicking on the appropriate button. Calculations can be performed in either Imperial or Metric units by using the choice button.
- On the middle right side of the screen is the Probe Panel. Details of the probe operation are given below.
- On the lower right side of the screen is the Output Panel. Details of the output variables are given below.
The Probe Panel contains a computer drawing of an output gauge and some buttons to the left. By default, the probe is turned off. You turn the probe on by pushing one of the white buttons on the Probe Panel. The probe itself will then appear in the View Window. You change the location of the probe using the sliders to the left and below the gauge on the Probe Panel. The value of the pressure or the velocity at the location of the probe tip (magenta ball on the view window) is displayed on the gauge. Or a green trail of “smoke” is swept downstream from the probe location. You turn the probe off by using the red button.
The input variables are located on the panel that is displayed at the lower left below the View Window. There are three input variables; the speed of the flow, the angle of attack of the model, and the tunnel static pressure. As you vary any of the input variables, the resulting orientation is shown in the View Window, the values of the surface variable are shown in the Diagnostic Window, and the computed lift is shown on the Output Panel. By default, the program begins with no flow through the tunnel.
The output variables are located on the panel that is displayed at the lower right below the Probe Panel. The chief output from the program is the computed the lift of the wing. The lift depends on the tunnel conditions so the dynamic and total pressure in the tunnel are also displayed. For the full system version, as you load different wing designs, the output panel gives a description of the wing geometry.