How to locate the vortex eyes in a vector field without using the data cursor and find the circulation around the eye.

Question

raj sekhar 2020-1-15

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评论： Ashfaq Ahmed 2022-4-25

greetings of the day

I am unable to extract the velocity values around the vortex eye inside a closed contour, so a to get the circulation. Dose anyone know how to isolate the velocity contour containg the vortex eye and find the circulation it. Ihave a .mat file of the velocity vector feild. I have calculated the curl but the i think its for the whole vector feild not at the particular region of recirculation . heres my code;

clear all

close all

load('B00001_X0_70_AvgV.mat')

x=x1';

y=y1';

vy=vy';

figure

contour(x,y,vy,15,'linewidth',1,'linecolor','b')

hold on

sr=surf(x,y,vy);

sr.EdgeColor='none';

sr.FaceColor='interp';

sr.FaceAlpha=0.8;

% [c,h]=contourf(x,y,vy,[0,-30.46],'linewidth',2);

contour(x,y,vy,[0,-30.46],'linewidth',1,'linecolor','k');

qv=quiver(x,y,vx',vy,'Color','k');

qv.LineWidth=2;

qv.AutoScaleFactor=1.5;

grid off

figure

surf(x,y,curl(vx',vy))

view(2)

% [curlx,curly,cav]=curl(x,y,vy);

%%It would be of great help if i can get some leads on it.

thanks

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raj sekhar 2020-1-15

i need to find the recirculation inside the contours defined by black lines. i have also attached the .mat file.

Thankyou for any help

raj

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Answer 1

darova 2020-1-15

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https://ww2.mathworks.cn/matlabcentral/answers/500358-how-to-locate-the-vortex-eyes-in-a-vector-field-without-using-the-data-cursor-and-find-the-circulati#answer_410229

在 MATLAB Online 中打开

You want to find velocities inbetween [0,-30.46]. So just select appropriate indices:

idx = -30.46 < vy & vy <= 0;
vy1 = vy;
vy1(~idx) = nan;
surf(x,y,vy1)

Maybe interpolation will be needed

x2 = linspace(min(x),max(x),100);
y2 = linspace(min(y),max(y),100);
[X2,Y2] = meshgrid(x2,y2);
vy2 = interp2(x,y,vy,X2,Y2);
idx = -30.46 < vy2 & vy2 <= 0;
vy2(~idx) = nan;
surf(X2,Y2,vy2)

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darova 2020-1-16

YOu are welcome! Please accept the answer if it helped

Ashfaq Ahmed 2022-4-25

hi @raj sekhar could you kindly let me know how did you find the location of the center of the vortex using the local maxima method? I am stack at the similar problem and it would be a great help if you kindly share your ideas.

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