
[Sponsors] 
Flow through rectangular channel using SIMPLER algorithm 

LinkBack  Thread Tools  Search this Thread  Display Modes 
November 19, 2022, 09:56 
Flow through rectangular channel using SIMPLER algorithm

#1 
New Member
Apoorv Mishra
Join Date: Nov 2022
Posts: 5
Rep Power: 2 
I am new to the community and CFD itself and am working on my first CFD program in Scilab based on the SIMPLER algorithm i.e. modeling a flow through a rectangular cross section channel. I want to get a Poiseuilli kind of flow profile but I'm stuck at a couple of boundary conditions. I have given a dirichlet type of Boundary condition i.e. constant velocity inlet at the face of the inlet and no slip at the 4 walls but I'm not understanding what should be the y and z (perpendicular to the length of channel) direction velocities (v & w respectively) at the inlet and outlet of the channel. It's a 3D staggered grid arrangement like the image below (image just for illustration), the black points being the points for pressure. https://drive.google.com/file/d/1oBm...ew?usp=sharing Let's say the red velocities on the extreme left are the constant u inlet velocities and the right ones being the outlet. So, for such an arrangement, there exists a series of v velocities (green) on the left of the inlet and also on the right of the outlet out of the main domain. For the no slip boundary conditions at the walls I did, v( :,:,1 ) = v( :,:,2); & v(:,:,npz+1) = v(:,:,npz); (npz = (no. of pressure elements along z direction) + 1) and similar for u & w. But what should be the condition for v and w at the inlet? I've tried v(1,:,: ) = v(2,:,: ) & same for w since both should be 0 at inlet face but it doesn't work and the solution seem to diverge after just the first iteration. Also I just want to give the constant inlet velocity as the initial condition so is there any need to specify pressure as boundary condition anywhere? Because as opposed to SIMPLE, SIMPLER requires an initial guessed velocity field and no pressure guess. Any help will be appreciated. Last edited by Mishra Apoorv; November 20, 2022 at 12:17. 

November 19, 2022, 13:42 

#2 
Senior Member

Let's split what you want from how you implement it.
At inlet, assuming an incompressible flow, you should assign all the velocity components, and having v and w as 0 is probably what you want. For the implementation,.it depends from what code you have. Is this a staggered finite difference code? 

November 20, 2022, 05:23 

#3 
New Member
Apoorv Mishra
Join Date: Nov 2022
Posts: 5
Rep Power: 2 
Thanks for taking time to respond.
I've edited the question with details. 

November 21, 2022, 11:17 

#4  
Senior Member

Quote:
Have you tested the code in 2D, or even 1D using symmetry bc and just one cell in that direction? Have you tested the code on any other case? 

November 25, 2022, 04:32 

#5  
New Member
Apoorv Mishra
Join Date: Nov 2022
Posts: 5
Rep Power: 2 
Quote:
https://drive.google.com/file/d/1Rwg...ew?usp=sharing Here I'm attaching my code for reference. If you have any insights or have worked with SIMPLER before, then please suggest how to troubleshoot such issues and if there's any good source to study the coding for CFD/FVM that you know of, then please mention it. Thank you. 

November 25, 2022, 16:19 

#6  
Senior Member

Quote:
The way these things are debugged is to focus on the most simple problem that doesn't work, possibly on the coarsest possible grid, and then analyze the algo step by step, comparing at each step what you get with what you expect. At some point you must find something that doesn't work, then you investigate its input. If it is legit than you have found your bug, otherwise you proceed backward until the input to a line is legit but the output isn't. 

November 25, 2022, 17:11 

#7  
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,290
Rep Power: 67 
Quote:
Why? You should suppose that this is a Dirichlet condition corresponding to a flow having only one velocity component, the one in streamwise direction, 

Tags 
boundary condition, poiseuille flow, scilab, simpler algorithm 
Thread Tools  Search this Thread 
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Applyinga one phase LES to rectangular channel flow  roi247  FLUENT  5  January 30, 2020 14:59 
modeling entering two phase flow in open channel flow  hesamabtahi  FLUENT  0  May 2, 2018 10:13 
How to validate a 3D poiseuille flow in a rectangular channel?  dhouha  FLOW3D  1  August 30, 2017 11:06 
Using LES simulating flow through a rectangular channel  roi247  FLUENT  22  March 16, 2016 12:13 
VOF modelling open channel river flow  Matthew Roberts  FLUENT  6  July 31, 2009 12:52 