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Matlab - plot pressure distribution around a circle

  1. Aug 16, 2010 #1
    I'm trying to plot the pressure distribution around a cylinder in a uniform flow field, so that the graphic is a circle with the pressure curve around it, like in the image below.
    http://img843.imageshack.us/img843/4649/63792687.th.jpg [Broken]

    Uploaded with ImageShack.us

    I have the equation for the ideal pressure coefficient Cp (which is what I'm wanting to display), and t is the theta values. (See code below)

    Then I use the polar function to plot it... polar(t,Cp)... but that starts at the origin, which isn't what I want. I thought it might help if I added the radius of my proposed circle to Cp, but it doesn't. So maybe I need a scaling factor on Cp or something..?

    Could someone help me out?
    Thanks.

    Code (Text):

    %%% Flow Around a Cylinder %%%

    % Initialise variables
    clear all
    clc

    U = 12;     % Freestream velocity m/s
    M = 2;      % Doublet strength
    radius = sqrt(M/2/pi/U);    % Cylinder radius
    t = linspace(0,2*pi,50);    % Range of theta values
    circle = ones(1,50);        % Create vector
    circle = radius.*circle;    % Circle of required radius

    % Calculations
    cp = 1 - 4.*(sin(t)).^2;     % Pressure coefficient
    cp_scaled = cp + radius;     % Attempted scaling

    % Display graphs
    polar(t,cp,'--r')
    hold on
    polar(t,circle)
    hold off
    figure
    polar(t,cp_scaled,'--r')
    hold on
    polar(t,circle)
    hold off
     
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Sep 28, 2011 #2
    Pretty useless now,

    just in case if you ever wonder what was missing

     
    Last edited by a moderator: May 5, 2017
  4. Sep 28, 2011 #3
    Thanks :)
    I never did figure it out, so it was helpful to know in case I have to do it again.
     
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