Hi Wasim, Sorry for a slow response. i am not aware anyone has put in this type of functionality. We have something along these lines to read in unsteady base flows that have been expressed as a Fourier expansion and then internally we do the interpolation to an unsteady base flow. Similarly for an inflow for an unsteady pipe we have a Womersley input profile but this has an analytic definition to evaluate. So this is something you would have to consider implementing. To add more information to the input file we have tended to extend the UserDefinedType string with colons so it reads something like USERDEFINEDTYPE=“TimeDependent:ReadMultipeFiles:Filename.rst:” Cheers, Spencer. On 11 Jul 2018, at 16:45, wasim sarwar <waseemsarwar121@hotmail.com<mailto:waseemsarwar121@hotmail.com>> wrote: Hi all, Is it possible in nektar++ to read the time-dependent boundary conditions from a file. Actually, I am simulating Vortex induced Vibration (VIV) of cylinder with blowing and suction from the surface. The motion of the cylinder is defined by the flag "userdefinedtype"=movingwall which accounts for the structural dynamics under the action of fluid forces. In order to implement blowing and suction, I need to update the value of velocity field at the cylinder surface at each time step. I cannot use the flag "userdefinedtype" twice in the same boundary condition tag to introduce this time-dependence. The way i could think of to implement this idea is to the read this time-dependent boundary condition from the file. I would also need to overwrite the content of the boundary file at each time step so that i donot need to write all file corresponding to the time steps. So, my question is, is there a way to generate the time-dependent boundary condition through a given function or by any other means, and then read the same time-dependent boundary condition from a given file for the next time step. cheers _______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk<mailto:Nektar-users@imperial.ac.uk> https://mailman.ic.ac.uk/mailman/listinfo/nektar-users Spencer Sherwin FREng, FRAeS Head, Aerodynamics, Director of Research Computing Service, Professor of Computational Fluid Mechanics, Department of Aeronautics, s.sherwin@imperial.ac.uk<mailto:s.sherwin@imperial.ac.uk> South Kensington Campus, Phone: +44 (0)20 7594 5052 Imperial College London, Fax: +44 (0)20 7594 1974 London, SW7 2AZ, UK http://www.imperial.ac.uk/people/s.sherwin/