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Navier-Stokes Simulation using Coefficient Form PDE

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Hi: I need to simulate fluid flow in a triangular duct, but I need to run it on a high reynold number. The problem is that when I run the model using the default "Laminar Flow" physics tab, I need a large domain tho reach the fully developed flow and memory problems arise. So I decide to run other model. I made a different nondimensionalization of the NS equations, but when I run the simulation in a 3d coefficient form with 4 variables, I can't get convergence.

I have the 3 momentum equations and the continuity equation.

I attach the coefficients in the way I set them, and below I show you the BC:

Inlet:
u=1
v, w=0

p=not specified

Outlet
u, v, w=not specified
p=0

Wall
u, v, w=0
p=not specified

Why can I reach convergence? Can someone please help me? I'd appreciate a lot!


15 Replies Last Post 17 mag 2017, 07:34 GMT-4

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Posted: 1 decade ago 8 lug 2013, 17:36 GMT-4
Dear Mehrez,

Would you mind send a copy of the model to me since I have been working on high reynold number problem but can not get any convergent solution so far.

Thanks a lot,

Jian
Dear Mehrez, Would you mind send a copy of the model to me since I have been working on high reynold number problem but can not get any convergent solution so far. Thanks a lot, Jian

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Posted: 1 decade ago 12 mag 2014, 09:49 GMT-4
Dear Mehrez,
may I ask you informaton on how to apply Navier Stokes with coefficient form? i´m stuck in a MHD problem, without the possibility to use , due to license, the CFD module.

Thanks in advance!
Gianmarco
Dear Mehrez, may I ask you informaton on how to apply Navier Stokes with coefficient form? i´m stuck in a MHD problem, without the possibility to use , due to license, the CFD module. Thanks in advance! Gianmarco

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Posted: 1 decade ago 12 mag 2014, 10:03 GMT-4
Hi dear Gianmarco
I've implemented NS equations under General PDE module. Is it what you want ?
Hi dear Gianmarco I've implemented NS equations under General PDE module. Is it what you want ?

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Posted: 1 decade ago 13 mag 2014, 09:21 GMT-4
Dear Mehrez,
really thanks if it´s possible, cause i cannot understand how to start with, it will be a very big help!
Dear Mehrez, really thanks if it´s possible, cause i cannot understand how to start with, it will be a very big help!

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Posted: 1 decade ago 13 mag 2014, 09:28 GMT-4
Ok no problem.
Just send me the form of your equation.
Do you want your equation to be implemented on Comsol under PDE weak form or general form ?
Mehrez
Ok no problem. Just send me the form of your equation. Do you want your equation to be implemented on Comsol under PDE weak form or general form ? Mehrez

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Posted: 1 decade ago 13 mag 2014, 10:06 GMT-4
Dear Mehrez ,
i attached the photo related to theory i´ve been follwing (it´s the TEMPUS european programme, 2012): concerning the weak form, i don´t know actually what could fit to my project: if i had the possibility ( but i i´m working with a workstation that has a few problems with the comsol forum itself, but strangely not the support one) i will send you the file. it´s easy to see it, it´snot so compicate: just i need to understand how to work with pde. i think weak form won´t be used for a simple case like this

Thanks for everything
Gianmarco
Dear Mehrez , i attached the photo related to theory i´ve been follwing (it´s the TEMPUS european programme, 2012): concerning the weak form, i don´t know actually what could fit to my project: if i had the possibility ( but i i´m working with a workstation that has a few problems with the comsol forum itself, but strangely not the support one) i will send you the file. it´s easy to see it, it´snot so compicate: just i need to understand how to work with pde. i think weak form won´t be used for a simple case like this Thanks for everything Gianmarco


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Posted: 1 decade ago 13 mag 2014, 10:08 GMT-4
i forgot to say, the equations at the top of both photo are the equation i need to use, one with dimensional coefficient and the other in the adimensional form,'; from here i don ´t know actually what to take

still thanks
i forgot to say, the equations at the top of both photo are the equation i need to use, one with dimensional coefficient and the other in the adimensional form,'; from here i don ´t know actually what to take still thanks

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Posted: 1 decade ago 13 mag 2014, 10:50 GMT-4
I have sent you the model in a private message.
Hope it will halp you.
Mehrez
I have sent you the model in a private message. Hope it will halp you. Mehrez

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Posted: 1 decade ago 4 lug 2014, 03:54 GMT-4
Dear Mehrez,
I'll be thankful if you can help me out on a similar problem.
I am trying to model a non-isothermal fluid flow problem, in which mass is not conserved within the domain. There is a vapor flux that exits the domain as soon as it is formed.

The problem with the fluid flow module is that I am not able to override the mass conservation equation. I have an expression for the mass flow rate of vapor, but I do not have a way to incorporate it into the model. I have read that using weak expressions helps, but I do not know how to implement that either.

Hence I decided to use the coefficient form PDE, where I can define the equations as per will. I need to know how to implement the compressible Navier Stokes equation in the coefficient form, with all the diadic terms. Kindly help me out on this.

I also look forward to any suggestions/guidance on using the weak form for Navier Stokes' mass conservation equation.

Thanks and regards
Syed Nadeem Akhtar
Dear Mehrez, I'll be thankful if you can help me out on a similar problem. I am trying to model a non-isothermal fluid flow problem, in which mass is not conserved within the domain. There is a vapor flux that exits the domain as soon as it is formed. The problem with the fluid flow module is that I am not able to override the mass conservation equation. I have an expression for the mass flow rate of vapor, but I do not have a way to incorporate it into the model. I have read that using weak expressions helps, but I do not know how to implement that either. Hence I decided to use the coefficient form PDE, where I can define the equations as per will. I need to know how to implement the compressible Navier Stokes equation in the coefficient form, with all the diadic terms. Kindly help me out on this. I also look forward to any suggestions/guidance on using the weak form for Navier Stokes' mass conservation equation. Thanks and regards Syed Nadeem Akhtar

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Posted: 1 decade ago 2 ott 2014, 10:15 GMT-4
Hello,

I am very interesting to write my own equations. Please Mehrez can you send me your NS model in PDE form? I would be a starting point for me to understand PDE implementation

jgivernaud@emix.fr

Best regards
Hello, I am very interesting to write my own equations. Please Mehrez can you send me your NS model in PDE form? I would be a starting point for me to understand PDE implementation jgivernaud@emix.fr Best regards

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Posted: 1 decade ago 8 nov 2014, 03:10 GMT-5
Hello,

I am very interesting to write my own equations. Please Mehrez can you send me your NS model in PDE form? I would be a starting point for me to understand PDE implementation

912437789@qq.com

Best regards
Hello, I am very interesting to write my own equations. Please Mehrez can you send me your NS model in PDE form? I would be a starting point for me to understand PDE implementation 912437789@qq.com Best regards

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Posted: 1 decade ago 11 nov 2014, 07:20 GMT-5
Hi Mehrez,
Please, i believe this will really be a good starting point for this my problem. Can you send me your NS model in PDE form? and how do i write temperature Eqn. together with the Navier stokes Eqn.

Am trying to solve 2D coupled navier stokes equation with temperature equation in comsol version 4.4 but don't really know how to input the temperature equation along side with the navier stokes equation as shown below
∇⋅v = 0
( ∂v/ ∂t) +(v ⋅∇v) = −∇P + k∇^2v + F
( ∂T/ ∂t) +(v ⋅∇T) = B∇^2T

and how do i remove this term (∇⋅v)^T in the momentum equation as it is in comsol
Hi Mehrez, Please, i believe this will really be a good starting point for this my problem. Can you send me your NS model in PDE form? and how do i write temperature Eqn. together with the Navier stokes Eqn. Am trying to solve 2D coupled navier stokes equation with temperature equation in comsol version 4.4 but don't really know how to input the temperature equation along side with the navier stokes equation as shown below ∇⋅v = 0 ( ∂v/ ∂t) +(v ⋅∇v) = −∇P + k∇^2v + F ( ∂T/ ∂t) +(v ⋅∇T) = B∇^2T and how do i remove this term (∇⋅v)^T in the momentum equation as it is in comsol

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Posted: 9 years ago 30 giu 2015, 06:48 GMT-4
Good Morning Mehrez,

I want to implement the simulation of a suspension through an Annulus using the coefficient form PDE, as the built in models do not have the required equations that I need.

So I want your help as to how to implement a simple Navier Stokes equation using coefficient form PDE where the velocity has three components and how to specify the inlet and outlet conditions.

Thank You
Good Morning Mehrez, I want to implement the simulation of a suspension through an Annulus using the coefficient form PDE, as the built in models do not have the required equations that I need. So I want your help as to how to implement a simple Navier Stokes equation using coefficient form PDE where the velocity has three components and how to specify the inlet and outlet conditions. Thank You

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Posted: 8 years ago 24 ott 2016, 13:04 GMT-4
Dear Mehrez

Hi, Mehrez, recently I encountered a similar problem for apply the incompressible condition.. SO could you please send me a copy of the general form pde? It will help me a lot if you could give me a hand!

xdengae@connect.ust.hk
Thanks a lot!
Dear Mehrez Hi, Mehrez, recently I encountered a similar problem for apply the incompressible condition.. SO could you please send me a copy of the general form pde? It will help me a lot if you could give me a hand! xdengae@connect.ust.hk Thanks a lot!

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Posted: 8 years ago 17 mag 2017, 07:34 GMT-4
Hey Mehraz!

I am facing the same problem with the coefficients when I use the Coefficient form PDE to write the Navier Stokes Equations. Can you help me out??
Hey Mehraz! I am facing the same problem with the coefficients when I use the Coefficient form PDE to write the Navier Stokes Equations. Can you help me out??

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