Velocity Fields/Stream Equations
 

hi

I am making a small cfd code and want to test my output in different flow fields

i want to test my output in a rotational / translation/ revolving flow field and any combination of these . could anyone tell me how to get the stream function corresponding to these

thanks a newbie

Re: Velocity Fields/Stream Equations
 

If you have the velocity field tecplot can plot the streamlines. You can even use matlab (stream2, stream3, streamline).

Re: Velocity Fields/Stream Equations
 

"rotational / translation/ revolving flow field"?

Does this mean it's a three dimensional (x - y - z) flow? If so, the stream function will be a vector function and so not too useful for visualization of the flow.

To get a stream function that's scalar, your flow must be 2-d, either Cartesian (x - y) or cylindrical (r - z although a rotational component can be included if it's axisymmetric).

You can visualize the flow using virtual particle traces or streaklines. Generate the tracks for those by for a series of points (x, y, z)_i by

x_i+1 = x_i + u(x_i, y_j, z_k)*dx

with similar for y_j+1 and z_(k+1).

Hope this helps.

Re: Velocity ... corrected post!
 

My previous reply to this was a bit hasty. See correction in the partical trace discussion below:

"rotational / translation/ revolving flow field"?

Does this mean it's a three dimensional (x - y - z) flow? If so, the stream function will be a vector function and so not too useful for visualization of the flow.

To get a stream function that's scalar, your flow must be 2-d, either Cartesian (x - y) or cylindrical (r - z although a rotational component can be included if it's axisymmetric).

You can visualize the flow using virtual particle traces or streaklines. Generate the tracks for those by for a series of points (x, y, z)_i by

*** Corrected text below ***

x_i+1 = x_i + u(x_i, y_i, z_i)*dx

with similar for y_i+1 and z_(i+1).

For the particle coordinates (x, y, z), the index "i" counts the locations generated for the virtual particle through the flow field. It is NOT an index for a grid line or node.

Hope this helps.