[Paraview] Computing a normal derivative of velocity

[Martin Vymazal]

Dear ParaView users and developers,

  I have an output file of a Finite Element code, which contains a  
fluid velocity vector field. I would like to plot the values of dv/dn  
on the walls of my domain. My idea was this: plot a gradient of  
velocity magnitude, generate surface normals and then compute the  
scalar product (grad(v),n). Unfortunately, I have several problems:  
when I plot the gradient of velocity  
(Filters->GradientOfUnstructuredDataSet), I have a scalar field of  
gradient magnitude (I guess), but no vector field, even though  
mathematically speaking, grad(scalar) results in a vector. Could you  
tell me how to generate a vector field where the vector components are  
(grad(v)_x,grad(v)_y,grad(v)_z) ?

Second, I don't understand why Filters->Generate Surface Normals is  
disabled when I load my data file (in Ensight format). The only way of  
plotting some normals is using 'glyphs', but these glyphs are then not  
available in the 'Calculator' filter which I wanted to use to compute  
the final scalar product (grad(v),n). One strange thing I also noticed  
is that the glyphs are not plotted on a part of the domain boundary  
(which is smooth).

Could you please give me a hint how to obtain the plot of dv/dn ?

Thank you.

  Martin Vymazal

----------------------------------------------------------------
This message was sent using IMP, the Internet Messaging Program.