Please help me to solve this problem!
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I have been asked to calculate vorticity of three velocity components u, v & w. I have attached .txt file for the same. As I knew curl does the same in MATLAB. Hence i tried these lines of code:
u=VarName1;
>> v=VarName2;
>> w =VarName3;
>> Ulin =linspace(min(u),max(u),33);
>> Vlin =linspace(min(v),max(v),33);
>> Wlin =linspace(min(w),max(w),33);
>> [U,V,W]=meshgrid(Ulin,Vlin,Wlin);
>> [CURLX, CURLY, CURLZ, CAV] = curl(U,V,W);
But when I type CURLX all are showing zero values...
回答（2 个）
Jos (10584)
2014-2-11
0 个投票
Did you check the contents of each variable?
Roger Stafford
2014-2-11
0 个投票
By the way you have defined U, V, and W, they must have a curl of identically zero. There can be no vorticity. That is because U = (max(u)-min(u)/32*x, V = (max(v)-min(v)/32*y, and W = (max(w)-min(w)/32*z, so all the partial derivatives that go to make up the curl must be zero: dU/dy = dU/dz = dV/x = dV/dz = dW/dx = dW/dy = 0.
3 个评论
the cyclist
2014-2-11
As a way of confirming Roger's wise words, note that if you add some random noise to your vectors:
U = U + rand(33,33,33);
V = V + rand(33,33,33);
W = W + rand(33,33,33);
then you will see non-zero curl everywhere.
Rizwana
2014-2-12
Roger Stafford
2014-2-13
You will need to use the 'curl' function in the form
[curlx,curly,curlz] = curl(X,Y,Z,U,V,W);
unless your X, Y, and Z are unit-spaced (see the documention.) The X, Y, Z need to be monotonic and in a form as if produced by 'meshgrid' though the spacing can be variable. These represent positions in the field, while U, V, and W represent the corresponding x, y, and z components of the vector field at these positions.
If your points are so numerous that you are running out of memory, you will have to do the computation in small enough sections of the field that you don't run out of memory. However, be aware that since the curl of the field is also a vector field, it will occupy just as much memory as the three arrays U, V, and W do.
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2014-2-13
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