March 2015 - Nektar-users - imperial.ac.uk

Generating curved edge in ICEM CFD for Nektar++
by Kamil ÖZDEN 03 Apr '15

03 Apr '15

Dear All, I found such a way to generate my meshes to use in Nektar++: 1) First I create my mesh in ICEM CFD. 2) Then I export that mesh from ICEM CFD as a Nastran file (with *.dat extension). 3) After that I open that *.dat file in Gmsh and save it as a *.msh file. 4) Finally I generate my *.xml file from that *.msh file. This works in Nektar++ but I have a problem about generating curved edges in ICEM CFD. There is no such option or I couldn't find how to succeed this. Is there any one who use this method to generate mesh for Nektar or can inform me about generating high order edge in ICEM CFD? NOTE: I've tried to generate curved edge in Gmsh with the imported *.dat file but it didn't work. Regards, Kamil

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Parabolic velocity profile for inlet boundary condition
by Kamil ÖZDEN 31 Mar '15

31 Mar '15

Dear All, In a stenosed pipe flow problem, I specify parabolic velocity profile u=2*(1−(r^2)), where r=sqrt(y^2+z^2) as seen below. /*<BOUNDARYREGIONS>*//* *//* C[7] *//* *//* C[9] *//* *//* C[8] *//* *//* </BOUNDARYREGIONS>*//* *//* *//* <BOUNDARYCONDITIONS>*//* *//* <REGION REF="0">*//* *//* <D VAR="u" VALUE="2*(1-(rad(y,z)^2))" />*//* *//* <D VAR="v" VALUE="0" />*//* *//* <D VAR="w" VALUE="0" />*//* *//* <N VAR="p" USERDEFINEDTYPE="H" VALUE="0" />*//* *//* </REGION>*//* *//* <REGION REF="1">*//* *//* <N VAR="u" VALUE="0" />*//* *//* <N VAR="v" VALUE="0" />*//* *//* <N VAR="w" VALUE="0" />*//* *//* <D VAR="p" VALUE="0" />*//* *//* </REGION>*//* *//* <REGION REF="2">*//* *//* <D VAR="u" VALUE="0" />*//* *//* <D VAR="v" VALUE="0" />*//* *//* <D VAR="w" VALUE="0" />*//* *//* <N VAR="p" USERDEFINEDTYPE="H" VALUE="0" />*//* *//* </REGION>*//* *//* </BOUNDARYCONDITIONS>*//**/ However, since u=0 at wall of the pipe due to no slip boundary condition definition, the calculated value of parabolic velocity profile at the wall (u = 1.5 ) can not be achieved. Is there any way to overcome this problem? Regards, Kamil

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Interest in potential Nektar++ workshop
by David Moxey 20 Mar '15

20 Mar '15

Dear all, As our user base is growing, we are considering arranging a workshop, where users and developers can present their work with Nektar++, as well as provide a forum for discussing long-term goals, feature requests and implementation challenges/bugs that you are finding within the current structure. The purpose of this email is to see if there is sufficient interest to arrange such a workshop. Probably it would take place over summer this year, across one or two days, and take the format of short-form presentations and some general discussion and support sessions. Please let us know by replying to the mailing list if you're interested! Also, if you are aware of any users who are not subscribed to this list, feel free to pass this email on (and encourage them to subscribe!) Cheers, Dave -- David Moxey (Research Associate) d.moxey(a)imperial.ac.uk | www.imperial.ac.uk/people/d.moxey Room 363, Department of Aeronautics, Imperial College London, London, SW7 2AZ, UK.

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Defining kinematic viscosity
by Kamil ÖZDEN 08 Mar '15

08 Mar '15

Dear All, I've a question about defining kinematic viscosity. In general I'm defining kinematic viscosity parameter in a non-dimensional way by taking both diameter and inlet velocity as 1 by dividing dimensional values of these parameters with reference velocity and length values. So kinematic viscosity becomes equal to 1/Re. However, in aortic blood flow tutorial kinvis is calculated by taking D=3.32 mm and mean inlet velocity=1 (there is no unit specified). Is there any inconsistency in terms of units of diameter and velocity? Could you please explain how Kinvis parameter is defined in this tutorial? Is my logic true in defining Kinvis non-dimensionally? Regards, Kamil

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Solution of Navier Stokes equation with steady-state solver
by Kamil ÖZDEN 05 Mar '15

05 Mar '15

Dear All, I want to solve a constricted pipe flow problem (for Re=100) using Navier Stokes equation with steady-state solver of Nektar++. By reading the user guide of Nektar++ I prepared solver info and parameters part of my xml file for this purpose as seen below: /* <SOLVERINFO>*//* *//* *//* *//* *//* *//* *//* *//* *//* *//* </SOLVERINFO>*//* *//* *//* *//* <PARAMETERS>*//* *//* ControlCoeff = 1 *//* *//* FilterWidth = 1 *//* *//* TOL = 10e-9 *//* *//* Kinvis = 0.1 *//* *//* </PARAMETERS>*/ When I tried to run an analysis I got such an error: /*Fatal : Level 0 assertion violation*//* *//*EquationSystem 'SteadyLinearisedNS' is not defined.*//* *//*Ensure equation name is correct and module is compiled.*/ I also tried other equation types (Steady Stokes, Unsteady NS etc.) What is the source of this error? I also want to ask if it is possible to write a history file for steady solutions? Regards, Kamil

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Defining time dependent velocity boundary condition
by Kamil ÖZDEN 03 Mar '15

03 Mar '15

Dear all, I wonder if it is possible to define a time dependent function for velocity boundary condition at the inlet in Nektar++? Like ramp function which gives U(t=0) = 0 and U(t=1) = 1? Regards, Kamil

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