PROJECT REPORT

    TITLE
    3-D CFD flow visualization of flow across delta winglet.

    INSTRUCTOR
    Mr Amithabh Mukherjee

    PROJECT GROUP
    SUBRATO ROY CHOUDHARY (95300)
    SHASHANK SINHA (94275)

    INTRODUCTION
    Fluid Mechanics is an important area and its computational part is generally very extensive. For every flow situation, there are large output files which contain diffrent results in numerical form. By seeing these output files, we are unable to visualize the flow. So its important to convert the results in graphical form, so that one can have better feel of flow that is taking place. Persons involved with CFD portion is mainly interesrted in the result and its accuracy. They use simple graphs etc. to visualize flow in a particular sitution. But we will do 3-D visualization which will be more realistic.

    PROBLEM STATEMENT
    My flow situation is flow across a delta winglet. Delta winglet is a traingular wing and is placed in a rectangular channel in such a way that two of the vertices are in contact with the base and the third vertex is free. Median from the third vertex make an acute angle with the axis of the channel and is known as 'angle of attack'. As flow take place there will formation of vortex behind the wing. This will generate a particular velocity field at different time instant. This velocity field changes with time as flow progress. Flow will depends on the following input parameters
    1> CHANNEL DIMENSION
    2> SIZE OF DELTA WINGLET AND ITS POSITION
    3> INLET VELOCITY PROFILE
    4> ANGLE OF ATTACK
    5> REYNOLDS NUMBER etc.

    OUTPUT
    For different input parameters we will velocity, pressure and temperature at different node points. Then this velocity field will be plotted in 3 dimension. For doing graphics portion, we will mainly use OPENGL. This type of velocity field will be plotted at different time instant and if combined in a sequencial fashion, will generate animated effect for proper visualization.

    METHOD 
    Now we will discuss about the different features of our program and logic, which we have used in making this program. We can cut three dimension flow field by a vertical plane parallel to the flow direction. Then we divide this two dimension region into different elements. We have considered this element having rectangular shape. There will be four corner points to each element . These points are termed as PIXELS.

    Surface is divided into pixels as

    Most of the pixels are shared by as many as four elements. Some are shared by 2 elements and four corner pixels are shared by only one element.

    Using our CFD program we calculate velocity componets and pressure etc. and and then we make a data file which will have following details. 1. Connectivity matrix i.e Corner points of each element (either in clockwise or in anticlockwise direction). Corner points have global No. 2. x and y co-ordinates are stored for each element for Node No= 1 to (total no. of nodes). 3. Then degree of fredoms are stored for each element. This dof will be velocity components or pressure at the nodal points. Vx are stored first, then Vy and pressure is stored in the data file. When all the datas are read by the program then it uses OpenGL graphics language to do the graphics portion. We have following feature.

    1. VELOCITY REPRESENTATION
    If there are x and y components of velocity then our program will plot this field as vector representation. Program ask for scale factor for better representation. Velocity components are multiplied with this factor and the plotted as a vector. Our program will plot this vector which will be proportional to the magnitude of velocity. Also we have assigned a color scheme for this vector representation. Red color shows lower magnitude and blue color shows higher value. Green color is an intermediate color between this two colors. We can show other colors as mixture of this colors. In this way we can plot a colored flowfield.

    Example of Velocity Representation

    2. ISOBAR REPRESENTATION
    We can plot location of constant pressure by connected by same color line. We use same color scheme in this case also.Here we have used following algorithem. User can provied data such as difference between two contour lines. For each element it will use dof value and use inter -polation and calculate other points on the edge of the rectangle and then it will join two points on two different edge by a straight line. In this way different contours are drawn. When all elements are visualised simultaneously then it will give a contour outlook.
     Example of Isobarlines


    3. SHADING
    We have also done shading portion . Contour representation are seen as lines of different colors. This colors lines are removed in this portion and there colors are smoothened and give a better representation of the d.o.f.
    Example of Shading

    MANUAL FOR USER

    f - Zoomin
    b - Zoomout
    l - X_left
    r - X_right
    u - Y_up
    d - Y_down
    m - Mesh_Off_On
    p - Pixel
    w - Wire
    R - Refresh
    D - New_Data
    o - New_Color
    O - Default_Color
    P - Show_Palette
    z - Refine
    x - Unrefine
    c - Cont_Surf_Off_On
    C - New_Cont_Surf
    v - Vel_Vec_Off_On
    V - New_Vel_Vec
    s - Shade_Off_On
    S - New_Shade