Does the curl function in matlab calculates vorticity?

Iam suppose to calculate vorticity using 3 velocity component u,v and w. Does the built function curl helps to do the job??

[Jan]

The question is not clear. Please do not post multiple questions for the same problem.

Answer 1

[David Young]

Yes it does. See http://en.wikipedia.org/wiki/Vorticity

[Roger Stafford]

True, but for matlab's 'curl' function only if cartesian coordinates are being used. In other coordinate systems, the curl requires corresponding modifications. I see no evidence that matlab has made a provision for this in the 'curl' function.

[David Young]

Indeed - I should have pointed that out. Ritzwana: are you working in cartesian or some other coordinates?

[Rizwana]

I have computed u , v and w using following set of formula

u = V * cos(beta) * cos(alpha) % alpha-yaw angle,beta-pitch angle

v = V * Cos(beta) * sin(alpha)

w = V * sin(alpha)

though my data was in spherical coordinates i.e, (V,alpha,beta), but i made use of conversion and got u,v,w in cartesian form. Please feel free to correct me, because iam still learning this coordinate system.

I can compute curl using u,v,w using matlab function but not able to plot its contours as it is m by n by p matrix and contour z(curl) should be always m* n format.

[David Young]

I'm not an expert on visualisation (I didn't realise that was the main issue from your original post), but maybe what you need is contour3.

[Roger Stafford]

It's not only the velocity components, u, v, w that need to be relative to a cartesian coordinate system but their associated position values, x, y, z that also must be in the same cartesian coordinate system, to enable matlab's curl function to be used, Rizwana. In your related query on Answer thread #116134 you appeared to be working either with a cylindrical or a spherical coordinate system, and for these you need a different formula for the curl.

[Rizwana]

Ok thanks.

Is there a way to do it manually. If you help me with formula then i may compute it at least manually. I have V--> Velocity(V), Beta() and yaw. How to compute curl manually using these three variables.

[David Young]

The problem is that I don't know for sure whether your position coordinates are cartesian, cylindrical or spherical. As Roger Stafford points out, they need to be cartesian for the curl function. You might find the functions pol2cart and sph2cart useful for conversions.