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TunnelSys - Version 1.0d

Glenn
Research
Center

This is a beta 1.0d version of the TunnelSys program, and you are invited to participate in the beta testing. TunnelSys is actually three separate programs that pass information between them. The User's Manual that is given below the program is always available to describe the many variables in the programs. If you find errors in the program or would like to suggest improvements, please send an e-mail to Thomas.J.Benson@nasa.gov.

Due to IT security concerns, many users are currently experiencing problems running NASA Glenn educational applets. There are security settings that you can adjust that may correct this problem.


This page contains an interactive Java applet to explore the design, testing, and post-processing of a wing model in a wind tunnel. All of the information presented by the applet are available within the Beginner's Guide to Wind Tunnels. You should start with the slide describing the design of a wind tunnel.

TunnelSys

Aerospace engineers use wind tunnels to determine the performance and operation of a proposed aircraft by measuring the forces on a model of the aircraft or some component of the aircraft. In the process of wind tunnel testing, an engineer must first design and build the wind tunnel model with appropriate instrumentation included. The model is then placed in the tunnel test section, air is blown over the model, and the forces on the model are recorded. Diagnostic techniques may also be employed during a wind tunnel test to provide detailed information to the design engineer. The engineer who conducts the wind tunnel test is not normally the same engineer who designed the model, but someone who is a specialist at wind tunnel operation. Raw data from the test is reduced to performance plots by another engineer and the results are then reported to the design engineer.

TunnelSys is a series of three Java computer programs which simulate the process of model design, wind tunnel testing, and data reduction. The output from the design program becomes the input to the testing program, the output of the testing program is the input to the data reduction program. To demonstrate the process used to conduct wind tunnel testing, we have produced the applet version of TunnelSys which is shown at the top of this page. Because of security limitations within Java, you can not save designs or results produced with the applet version. However, the more powerful application version of TunnelSys does permit a team of students to work on the various systems engineering aspects of wind tunnel testing. Each student works only on their particular task of the project (design, test, or data reduction) and information is passed between the programs by data files which must be stored on their computers.

The TunnelSys applet comes in two versions. The version presented here includes the on-line user's manual which describes the various options available in the program and includes hyperlinks to pages in the Beginner's Guide to Wind Tunnels describing the math and science of wind tunnels. More experienced users can select a streamlined version of the program which does not include these instructions and loads faster on your computer. You can also download the program to your computer by clicking on this yellow button:

Button to Download a Copy of the Program

With the downloaded version, you can run the program off-line and do not have to be connected to the Internet.

GENERAL INSTRUCTIONS

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 blue or 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. Buttons are colored black, blue, red, or magenta with white print. To activate a button, move the cursor over the button and left click on the mouse. Some buttons turn yellow with black print when activated. There are information text fields in TunnelSys that help the user to know what to do next.

If you see only a grey box at the top of this page, be sure that Java is enabled in your browser. If Java is enabled, and you are using the Windows XP operating system, you need to get a newer version of Java. Go to this link: http://www.java.com/en/index.jsp, try the "Download It Now" button, and then select "Yes" when the download box from Sun pops up.

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.

SCREEN LAYOUT

TunnelSys is a a combination of three interactive programs. The first program is used to design wing models. The output from the design program is used as input to the wind tunnel test program. The wind tunnel program can be used for diagnostic purposes, to study the flow around the wing, and can be used to develop performance curves describing how the lift changes as a function of speed, angle of attack, and tunnel pressure. Output from the wind tunnel program is used as input to the post-processing program. The post-processing program produces plots and can be used to compare the results from several experiments.

The initial panel displayed in TunnelSys is called the Title Panel. The Title Panel allows you to invoke the the three interactive programs by using buttons, and displays the status of your investigation. As you invoke each program, the new program is displayed and the Title Panel vanishes. You hit a red "Return" button on each program panel to retrieve the Title Panel and the status of that program is then noted as "Completed". We will now describe each of three programs of TunnelSys, beginning with the Design Program.

DESIGN PROGRAM

The Design Program screen is divided into three main parts:

  1. On the top left side of the screen is the View Window. The view window includes a graphic of the wing model that you are designing and a slider which control the graphic. Details of the window are given in the Graphics section.
  2. On the right side of the screen is an Engineering Drawing of your model. The size and scale of the model is given at the upper right of the panel. Clicking on the words "Double" and "Half" will change the size of the picture.
  3. On the lower left side of the screen is the Input/Output Panel. Details of the variables are given below.

Design Graphics

The View Window contains a computer drawing of the wing model that you are designing and some controls for the schematic drawing. You can move the picture within the window by moving the cursor into the window, holding down the left mouse button, and dragging the model to a new location. You can also "Zoom" in close to the model by using the green slider at the left of the window. If you get lost, pushing the yellow Find button will return the model to the initial position.

Design Input/Output Variables

The input/output variables are located on the panel that is displayed at the lower left. There are four input variables; the type of airfoil, the camber (curvature), thickness, and chord of the wing. The meanings of these terms are described on the geometry web page of the Beginner's Guide. The span of the wing is fixed to fit within the wind tunnel. As you vary any of the input variables, the resulting geometry is shown in the view window and the drawing window. Output from the program includes the wing projected area and the aspect ratio which are also defined on the geometry page. Calculations can be performed in either Imperial or Metric units by using the choice button at the bottom of the page. As you develop a wing design, click on the blue "Save Data" button to save the results for wind tunnel testing. When you complete your designs you can return to the Title Panel by clicking the red button. You can start over at any time by clicking the "Restart" button.

WIND TUNNEL PROGRAM

The Wind Tunnel Program screen is divided into five main parts:

  1. 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 tunnnel will change depending on your inputs. Particle traces will indicate that there is flow through the tunnel.
  2. 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 above the graph. 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.
  3. On the lower left side of the screen is the Input Panel. Details of the variables are given below. Calculations can be performed in either Imperial or Metric units by using the choice button. You can return to the Title Panel by clicking the red button and start over by clicking the "Restart" button at the bottom of the panel.
  4. On the middle right side of the screen is the Probe Panel. Details of the probe operation are given below.
  5. On the lower right side of the screen is the Output Panel. Details of the output variables are given below.

Probe Operation

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.

Input Variables

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.

You begin the wind tunnel test by clicking the blue "Load Models" button. The text box to the right will give the total number of wings designed using the previous program. You next select a wing to test by entering the Model # on the panel to the right below the probe gauge. You then click "Install Model" and the shape of the model in the view window will change. The details of the model design are loaded into the output panel as described below.

You now change the values of the flow variables as described above to set up flow in the tunnel. Then you select which flow variable you are going to change while holding the other variables fixed during a test. You indicate the choice by clicking on the blue buttons labeled "Select Test". Next you click the "Begin Test" button, then set the selected variable value to the first value. Click "Take Data Point" and the "Point #" will increase by one. Set the next value of the input variable and again click "Take Data Point". Continue this process until you are finished with this test, then click "End Test". You may now select a new test, or install a different model and begin the process all over again. When you have finished all of your tests, click the "Return" button to go back to the Title Panel.

Output Variables

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 lift of the wing. The lift depends on the tunnel conditions so the dynamic and total pressure in the tunnel are also displayed. As you load different wing designs, the output panel gives a description of the wing geometry.

POST-PROCESSING PROGRAM

The Data Processing Program screen is divided into four main parts:

  1. On the top left side of the screen is the Main Plotter Window. The plotter window displays a graph of the data obtained from the wind tunnel test program. Multiple plots can be displayed in this window to compare the results from several tests. The data appears as small dots with straight lines connected the data points. You can rescale the plots by using the buttons at the top of the window.
  2. On the top right side of the screen is the Diagnostic Plotter Window. You can choose to display either a graph of the test data for a specific test or a "movie" of the wing in the tunnel for a given data point. For a graph of the test data, the plotter shows the data points as small dots plotted on the theoretical result for the given test conditions. A selected data point is shown as a red dot on the plot.
  3. On the lower left side of the screen is the Control Panel. Details of the plot generation are given below. Data can be displayed in either Imperial or Metric units by using the choice button. You can return to the Title Panel by clicking the red button and start over by clicking the "Restart" button at the bottom of the panel.
  4. On the lower right side of the screen is the Diagnostics Selection Panel. Details of the selection process are given below.

Plot Generation

The Control Panel contains buttons to select the types of plots displayed in the Main Plotter Window. The process begins by clicking on the "Load Data" button. The text field to the right of the button will display the total number of tests completed using the wind tunnel program. You select which test data you are going to plot by using the input box labeled "Select Test #". You then enter the test data into the plotter by clicking "Open Test". The number of data points in the test is shown to the right, plots appear in the plotter windows, and the type of test (lift versus speed, angle of attack, or pressure) is noted. During the wind tunnel test, the lift is measured as well as the tunnel conditions. A more useful parameter for design is the lift coefficient, which is calculated by the post-processing program. You can select to plot the lift coefficient (Cl) by using the buttons in the lower portion of the Control Panel.

Diagnostic Selection Panel

The Diagnostic Selection Panel is at the lower right of the Post-Processing Program screen. With the diagnostic selection panel, you can display detailed data about selected points on the test plot. The data point is selected by using the "Increase" and "Decrease" buttons at the top of the panel. The test conditions, measured lift, and calculated lift coefficient are then displayed for the selected data point. The selected point is also shown in red on the diagnostic plot above the panel.

NEW FEATURES

The Education Programs Office will continue to improve and update TunnelSys based on user input. Changes from previous versions of the program include:

  1. On 7 Aug 09, version 1.0d was released. This is the first released version of the TunnelSys program.

Guided Tours

Navigation..


Button to Display Wind Tunnel Index Button to Display Aerodynamics Index
Beginner's Guide to Wind Tunnels
Beginner's Guide to Aeronautics

 

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Editor: Tom Benson
NASA Official: Tom Benson
Last Updated: Jun 12 2014

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