'Generate Surface Normals' requires a vtkPolyData as input. Run 'Extract Surface' which will give you a vtkPolyData, which you can generate surface normals from.
Running GradientOfUnstructuredDataSet on a scalar will give you a vector. You may have to compute the velocity magnitude first and store it as a variable before trying to compute the gradient. You can do this using the calculator with a function 'mag(v)' naming it something creative like say 'mag_v', then selecting mag_v as your input to the gradient computor. Similarly, to compute the dot product of two vectors, in the calculator it is simply '(Normals).(grad_mag_v)'. =================================== Adriano Gagliardi MEng PhD Business Sector Leader Computational Aerodynamics Aircraft Research Association Ltd. Manton Lane Bedford Tel: 01234 32 4644 E-mail: [email protected] Url: www.ara.co.uk -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Martin Vymazal Sent: 31 August 2010 19:18 To: [email protected] Subject: [Paraview] Computing a normal derivative of velocity 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. _______________________________________________ Powered by www.kitware.com Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html Please keep messages on-topic and check the ParaView Wiki at: http://paraview.org/Wiki/ParaView Follow this link to subscribe/unsubscribe: http://www.paraview.org/mailman/listinfo/paraview ********************************************************************** This email contains information that is private and confidential and is intended only for the addressee. If you are not the intended recipient please delete it and notify us immediately by e-mailing the sender. Note: All email sent to or from this address may be accessed by someone other than the recipient, for system management and security reasons. Aircraft Research Association Ltd. Registered in England, Registration No 503668 Registered Office: Manton Lane, Bedford MK41 7PF England VAT No GB 196351245 ********************************************************************** _______________________________________________ Powered by www.kitware.com Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html Please keep messages on-topic and check the ParaView Wiki at: http://paraview.org/Wiki/ParaView Follow this link to subscribe/unsubscribe: http://www.paraview.org/mailman/listinfo/paraview
