WIND TUNNEL 2D - V3.0
PROGRAMMED BY: AARON K. KNOLL
DATE: September 2010
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DESCRIPTION:
    This program simulates a two dimensional wind tunnel for low
    Reynolds' number flows.  The code uses the Semi-Lagrangian technique 
    for solving the viscous incompressible Navier Stokes equations.
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GETTING STARTED:
    The best way to learn is by trying.  This simple tutorial is all you
    need to know to get started.

    Step 1:  Define your geometry.
        This step is aimed at simplicity rather than geometric accuracy.
        All you need to do is create a JPEG picture of the object or
        domain you wish to analyze.  All solid surfaces should be black
        and the fluid domain should be white.  That's it!  Check
        "wing.jpg" for an example.

    Step 2:  Run the program.
        Now run the program "windtunnel2d.exe" (or windtunnel2d on
        a UNIX machine).  Enter the following input when prompted:

        >>Input JPEG image: wing.jpg
        This sets the geometry file you wish to use.

        >>Reynold's No.: 100
        This tells the program what inlet velocity to use.  The Reynolds'
        number is a non-dimensional measure of the flow speed given
        by V*L/Nu, where V is the velocity, L is the length reference
        (channel height in this program), and Nu is the kinematic 
        viscosity.  Check the following website for further details
        regarding the Reynold's number:
        
            http://en.wikipedia.org/wiki/Reynolds_number

        >>Kinematic viscosity [m^2/s]:  1.46e-5
        This sets the kinematic viscosity of the fluid.  Here we are
        using the viscosity of air at standard temperature and
        pressure.  Here are some common kinematic viscosities:

            Air = 1.46e-5
            Water = 1.0e-6
            Oil = 9e-4

        >>Density [kg/m^3]: 1.184
        This sets the density of the fluid.  Here we are using the
        density of air.  Here are some common material densities:

            Air = 1.184
            Water = 997
            Oil = 920

        >>Wind tunnel height [m]: 1
        Here we set the wind tunnel height to 1 meter.

        >>Wind tunnel length [m]: 2
        Here we set the wind tunnel length to 2 meters.

        >>Mesh spacing (0=coarse, 1=standard, 2=fine): 0
        This is an especially important parameter that defines the
        mesh density used in the calculation.  The finer the mesh
        spacing the more accurate the solution.  However, a fine
        mesh will take much longer to calculate.  Here is a rough
        estimate.  On a decently fast computer, a coarse mesh
        will take 5 to 10 minutes, a standard mesh takes 1/2 hour
        to an hour, and a fine mesh will take a couple hours.
        So, try your calculation on a coarse mesh first.  Then
        move to the standard mesh or fine mesh when you are ready
        for the final accurate solution.

        >>Maximum number of iterations: 10000
        This sets an upper limit on the number of iterations.  It
        should be used when you feel you are waiting too long for
        a solution, and want to see how things are progressing.
        For a complete simulation, set this parameter to a vary
        large value so that the simulation completes before
        reaching the maximum count.  Try 100000 in most cases
        to make sure.

        Alright, that's it!  Now the simulation will run to completion
        and you can view your first results.

    Step 3:  Analyze the results.
        The program will automatically output the lift and drag of
        the object when the simulation completes.  Also, new JPEG
        pictures will be produced:

        pressure.jpg:  A picture of the pressure field.

        velocity.jpg:  A picture of the velocity field and streamlines.

        U.jpg:  A picture of the x-component of velocity.

        V.jpg:  A picture of the y-component of velocity.

        Also, for detailed analysis, a text file containing the x-
        component of velocity (U.dat), y-component of velocity
        (V.dat), and pressure terms (P.dat) will be output.
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    CONTACT: Aaron K. Knoll
        e-mail: a.knoll@surrey.ac.uk
