Curl, Divergence calculation from velocity data

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Hi,
I have calculate the Curl, Divergence from the velocity data file available in 4650 x 4 array. Here 1, 2, 3, and 4 columns reprsents x, y, u, v. I have tried with below script, but I am getting some error. Please help..
X = data (:,1);
Y = data (:,2);
UU = data (:,3);
VV = data (:,4);
[X,Y] = meshgrid(X,Y);
[UU, VV] = meshgrid(UU,VV);
f = curl(UU,VV);
  2 Comments
Turbulence Analysis
Turbulence Analysis on 7 Aug 2020
Hi, The error msg is as below
Index in position 1 is invalid. Array indices must be positive integers or logical values.

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Answers (3)

Bruno Luong
Bruno Luong on 7 Aug 2020
Edited: Bruno Luong on 7 Aug 2020
Your data is already gridded, no need to gridded on top of it
load('matlab.mat')
UU=reshape(data(:,3),[75 62]);
VV=reshape(data(:,4),[75 62]);
X=reshape(data(:,1),[75 62]);
Y=reshape(data(:,2),[75 62]);
close all
figure
quiver(X,Y,UU,VV);
f = curl(UU,VV);
figure
imagesc(f');
  1 Comment
Turbulence Analysis
Turbulence Analysis on 7 Aug 2020
Hi, Bruno,
Many thanks for your quick reply..
Actually, I am getting only vector plot. Stiil, getting below error while exceuting 'curl'
Index in position 1 is invalid. Array indices must be positive integers or logical values.

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Turbulence Analysis
Turbulence Analysis on 7 Aug 2020
Hi, Bruno,
Now, I am able to execute curl function. However, it seems, some mistake in curl computtaion. Actually, the calculated vorticity should look something similar to the attached fig.
Furthermore, I would like to get the vector plot and vorticty plot on the same fig, I tried with 'hold on', but I am not gettting correct figure..
I would be great if you could help me with this...
  5 Comments

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Turbulence Analysis
Turbulence Analysis on 7 Aug 2020
Hi,
Many thanks for your support..
For gradieant I have used as follows
[dx, dy]= gradient (UU');
I am getting good results
I am getting good results...

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