October 2019 - Nektar-users

Element with max CFL
by Vishal Saini 02 Apr '20

02 Apr '20

Hi all, Quick question: Has anyone tried to check the location of a particular element in the mesh? A log file reports the maximum (?) CFL and the corresponding element as: "CFL: 0.0337915 (in elmt 94488)"? Is there a quick way to locate "elmt 94488"? Cheers, Vishal

2 2

Manipulate 3DH1 chk/fld file in Fourier space
by F Mellibovsky 16 Mar '20

16 Mar '20

Dear all, I have run a 3DH1 simulation and I need to set all Fourier coefficients to zero except those corresponding to a fundamental wavelength and its harmonics (e.g. keep only modes 0, +-5, +-10, etc and set all the rest to zero). I have the intuition that some combination of FieldConvert options can accomplish exactly this, but I am unsure of what is the best (or some) way to proceed. My guess is that the "homplane:wavespace:planeid=?" can be used to extract the individual Fourier modes, but I am unsure as to how the Fourier modes are sorted and which ones must be extracted to recover a chosen fundamental wavelength and its harmonics (both real and imaginary parts, or modulus and argument, or however the Fourier modes are stored). The only one I'm pretty sure of is mode 0 or mean mode. Once I get the individual fld files for each one of the modes, I was intending to use the "addfld:fromfld=mode1.fld:scale=1 mode1.xml mode2.fld newfile.fld" sequentially to build a solution from the chosen modes. The issue here is that the fields extracted with "homplane" seem to be 2D and would therefore need to be recast in 3DH1 form before proceeding to "addfld". How can this be done? Thanks in advance for your help Fer Mellibovksy

4 5

Product between base flow derivative and the aerodynamic forces
by Daiane Iglesia Dolci 13 Oct '19

13 Oct '19

Dear all, I need to solve a mathematical operation that is shown in the figure attached below. I am simulating an adjoint field and I wanna compute the product between a derivative of the base flow velocity and the aerodynamic force of the adjoint field, at the wall boundary. I know that in the FilterAeroforces.cpp, the forces are computed in each element, then an integral is applied. So I would like to know how I can take the derivative of the base flow in these elements by reading the baseflow.fld. If someone can help me, I thank you. Daiane I. Dolci.

2 1

"True" pressure in periodic BC
by Adriano Takata 13 Oct '19

13 Oct '19

Hi, how are you? (Nektar++ 5.0) I am working in Poiseuille flow 2D with periodic boundary conditions. I get the solutions (u = (1 + y) * (1-y), v = 0, and p = 0) with the solver. The pressure is 0 due to the flowrateforce, but I would like to know if I can get the "true" pressure thought the velocity field. Thank you. Adriano Sueke Takata

2 1

Compressible solver queries
by Vishal Saini 09 Oct '19

09 Oct '19

Hi all, I was giving the compressible flow solver a try and have a couple of queries. 1. Are the history probes set up for this solver? 2. I was looking into the possibility of adding a passive scalar term for some validation. From a first glance, it seems that an additional scalar transport equation is not implemented in the CompressibleFlowSolver (at least in the v4.5.0). Is that correct? If yes, has anyone tried that yet? If not, could you please give me some ideas on how to start about it? I guess, we just need to add convective and diffusive fluxes to the system of equations somehow (in CompressibleFlowSystem.cpp and NavierStokesCFE.cpp?). And I guess the Boundary Conditions can be generically defined for extra variables as in CompressibleFlowSystem::DoOdeProjection function(?) PS. What is the "smooth viscosity model"? 446 // For the smooth viscosity model 447 if (nVariables == m_spacedim+3) 448 { 449 // Add a zero row for the advective fluxes 450 for (j = 0; j < m_spacedim; ++j) 451 { 452 Vmath::Zero(nq, flux[m_spacedim+2][j], 1); 453 } 454 } Thank you in advance for your time. Best Regards, Vishal --- *Vishal SAINI* PhD Student Loughborough University

3 2