|
[Sponsors] |
August 22, 2017, 18:22 |
Passive Scalar Out of Bounds Channel
|
#1 |
Senior Member
Join Date: Mar 2016
Location: Bergamo
Posts: 157
Rep Power: 10 |
Hello to all,
I'm solving the flow in a very simple geometry: the well known Tjunction channel. It is a microfluids device so the dimensions are of the order of 10^(-6). The flow is completely laminar due to the very low Re number (Re=100). The channel is characterized by two inlets and one outlet. I linked an image to be more clear. My flow is single phase, water at ambient temperature. Now, after the calculation of the velocity and pressure field with simpleFoam, i run a simulation to calculate the passive scalar (DT=3*10^(-10)). At one inlet i imposed a T=0 while at the other T=1 and then i run scalarTransportFoam. In this manner i can observe how the two flows mix in the outlet channel. The big problem is that my scalar goes out of bound, this means i find value larger 1 and it shouldn't happen. I tried to fix the problem using different schemes for the divergence as suggested in other threads but nothing, the problem is always there. Is there someone who have experience in this type of problems? I link also the two cases. Thanks for help. Best Regards, Roberto |
|
August 23, 2017, 05:24 |
|
#3 |
Senior Member
Join Date: Mar 2016
Location: Bergamo
Posts: 157
Rep Power: 10 |
Hi akidess, first thank you for your reply.
What do you mean? Sorry, i don't understand. Here there is my output after running checkMesh Code:
/*---------------------------------------------------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: v1612+ | | \\ / A nd | Web: www.OpenFOAM.com | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ Build : v1612+ Exec : checkMesh Date : Aug 23 2017 Time : 10:19:27 Host : "Nitro" PID : 4231 Case : /home/roby/Scrivania/0.4/Direct nProcs : 1 sigFpe : Enabling floating point exception trapping (FOAM_SIGFPE). fileModificationChecking : Monitoring run-time modified files using timeStampMaster (fileModificationSkew 10) allowSystemOperations : Allowing user-supplied system call operations // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // Create time Create polyMesh for time = 0 Time = 0 Mesh stats points: 306516 faces: 863850 internal faces: 810150 cells: 279000 faces per cell: 6 boundary patches: 5 point zones: 0 face zones: 0 cell zones: 0 Overall number of cells of each type: hexahedra: 279000 prisms: 0 wedges: 0 pyramids: 0 tet wedges: 0 tetrahedra: 0 polyhedra: 0 Checking topology... Boundary definition OK. Cell to face addressing OK. Point usage OK. Upper triangular ordering OK. Face vertices OK. Number of regions: 1 (OK). Checking patch topology for multiply connected surfaces... Patch Faces Points Surface topology walls 45900 46330 ok (non-closed singly connected) inlet1 300 336 ok (non-closed singly connected) inlet2 300 336 ok (non-closed singly connected) movable 6600 6951 ok (non-closed singly connected) outlet 600 651 ok (non-closed singly connected) Checking geometry... Overall domain bounding box (-0.00015 -0.00165 0) (0.003 0.00165 0.0002) Mesh has 3 geometric (non-empty/wedge) directions (1 1 1) Mesh has 3 solution (non-empty) directions (1 1 1) Boundary openness (-6.91724e-18 1.96638e-18 2.57098e-17) OK. Max cell openness = 1.29247e-16 OK. Max aspect ratio = 1 OK. Minimum face area = 1e-10. Maximum face area = 1e-10. Face area magnitudes OK. Min volume = 1e-15. Max volume = 1e-15. Total volume = 2.79e-10. Cell volumes OK. Mesh non-orthogonality Max: 0 average: 0 Non-orthogonality check OK. Face pyramids OK. Max skewness = 3.4169e-13 OK. Coupled point location match (average 0) OK. Mesh OK. End Best Regards, Roberto |
|
August 23, 2017, 05:41 |
|
#4 |
Senior Member
Robert
Join Date: May 2015
Location: Bremen, GER
Posts: 292
Rep Power: 12 |
Hello Roberto,
did you check your fvSchemes settings? Using Gauss limitedLinear 1; for the divergence scheme of the passive scalar usually works fine for me. Last edited by RobertHB; August 23, 2017 at 06:57. |
|
August 23, 2017, 09:51 |
|
#5 | |
Senior Member
Join Date: Mar 2016
Location: Bergamo
Posts: 157
Rep Power: 10 |
Quote:
I tried the "Gauss limitedLinear01 1" scheme for the divergence but nothing, the solution continues to be out of bounds |
||
August 25, 2017, 04:31 |
|
#6 |
Senior Member
Join Date: Mar 2016
Location: Bergamo
Posts: 157
Rep Power: 10 |
Little update
I noticed few days ago something strange: of you not copy the phi file in the 0 folder scalarTransportFoam produces a phi file which is different from that produced by simpleFoam. This is very strange. Using the phi file produced by simpleFoam the solution improves but not enough. Why this difference? Best Regards, Roberto |
|
June 6, 2019, 09:37 |
|
#7 |
Senior Member
Alejandro
Join Date: Jan 2014
Location: Argentina
Posts: 128
Rep Power: 12 |
I am facing a similar problem. Did u manage to solve the problem?
|
|
July 17, 2019, 04:42 |
|
#8 |
Senior Member
Join Date: Mar 2016
Location: Bergamo
Posts: 157
Rep Power: 10 |
||
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
problem during mpi in server: expected Scalar, found on line 0 the word 'nan' | muth | OpenFOAM Running, Solving & CFD | 3 | August 27, 2018 05:18 |
Division by zero exception - loop over scalarField | Pat84 | OpenFOAM Programming & Development | 6 | February 18, 2017 06:57 |
Issue symmetryPlane 2.5d extruded airfoil simulation | 281419 | OpenFOAM Running, Solving & CFD | 5 | November 28, 2015 14:09 |
Diverging solution in transonicMRFDyMFoam | tsalter | OpenFOAM Running, Solving & CFD | 30 | July 7, 2014 07:20 |
compressible flow in turbocharger | riesotto | OpenFOAM | 50 | May 26, 2014 02:47 |