How to use the streamline function for a circular area?

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Xinchen Zhang 2019-10-14

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https://ww2.mathworks.cn/matlabcentral/answers/485120-how-to-use-the-streamline-function-for-a-circular-area

评论： Xinchen Zhang 2019-10-14

test.mat

Hi all,

Let's say, 'x' and 'y' in the mat file are the coordinate of the circular area, consist of 64 ununiformly distributed points on radial lines and 180 uniformly distributed angles. 'ux' and 'uy' in the mat file are the velocity on x and y directions. But when I use 'streamline(x,y,ux,uy,0.1,0.1)' or 'stream2(x,y,ux,uy,0.1,0.1)' to plot the streamline of the circular area, it always gives me the error message

"Error using griddedInterpolant

Interpolation requires at least two sample points in each dimension."

So I would like to know how to use the streamline function for a circular area.

Thank all in advance, any advice would be much appreciated.

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Answer 1

darova 2019-10-14

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https://ww2.mathworks.cn/matlabcentral/answers/485120-how-to-use-the-streamline-function-for-a-circular-area#answer_396234

在 MATLAB Online 中打开

You can just make new grid/mesh for your data (standard rectangular, corners are NaN)

Here is a way:

clc,clear
load test.mat
[m,n] = size(x);
x1 = linspace( min(x(:)), max(x(:)), 50 );  % x boundary
y1 = linspace( min(y(:)), max(y(:)), 50 );  % y boundary
[X,Y] = meshgrid(x1,y1);                    % new mesh
U = griddata(x,y,Ux,X,Y);                   % new Ux
V = griddata(x,y,Uy,X,Y);                   % new Uy
t = linspace(0,2*pi,20);
[sx1,sy1] = pol2cart(t,5e-3);               % start points
cla
streamline(X,Y,U,V, sx1, sy1)
hold on
plot(sx1,sy1,'*r')                          % start points of streamlines
plot(x(end,:),y(end,:),'.-r')               % boundary of a region
hold off
axis equal