Curl, Divergence calculation from velocity data

Question

Turbulence Analysis 2020-8-6

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https://ww2.mathworks.cn/matlabcentral/answers/576244-curl-divergence-calculation-from-velocity-data

回答： Turbulence Analysis 2020-8-7

matlab.mat

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);

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Sudheer Bhimireddy 2020-8-6

"some error" doesn't help much. Post your error so that we can help.

Turbulence Analysis 2020-8-7

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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Answer 1

Bruno Luong 2020-8-7

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/576244-curl-divergence-calculation-from-velocity-data#answer_476416

编辑：Bruno Luong 2020-8-7

在 MATLAB Online 中打开

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');

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Turbulence Analysis 2020-8-7

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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Answer 2

Turbulence Analysis 2020-8-7

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/576244-curl-divergence-calculation-from-velocity-data#answer_476428

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...