[COMSOL_Users] CFD Module

[Nunzio Piro]

hi guys,
I am a new member of this group. I recently started using COMSOL.
I have a problem with a CFD simulation. 
I must simulate a pipe flow with  water of costant diameter, D, equal to 0.004 m, and 0.2 m long.
I need to know the friction factor,  i need to use Turbolent Flow, k-epsilon (spf) and i study the tutorial model but i don't know where i can put the material propiety of the pipe that can define the friction factor. 
can someone help me? 

thank you  

[avkolesnikov]

Hi Nunzio,

You dont have to include pipe walls into your model (and therefore you dont need to define material property for the pipe).

Just model turbulent flow in 2D axisymmetrical domain (that is your pipe) with inlet, outlet and wall boundary conditions.

Andrei

Post by Nunzio Piro
hi guys,
I am a new member of this group. I recently started using COMSOL.
I have a problem with a CFD simulation. 
I must simulate a pipe flow with  water of costant diameter, D, equal to 0.004 m, and 0.2 m long.
I need to know the friction factor,  i need to use Turbolent Flow, k-epsilon (spf) and i study the tutorial model but i don't know where i can put the material propiety of the pipe that can define the friction factor. 
can someone help me? 
thank you  

[Nunzio Piro]

Hi Andrei,
i model turbolent flow (turbolent flow, k-epsilon phisics) in 2D. i create 3 triangles, one for water flow and two for pipe. i select iron for pipe. i define inlet, outlet conditions. the simulation is ok. 
i want know the friction factor that i want compare with the results that came from pipe flow phisics.
how can i valuete the friction factor in turbolent flow, k-epsilon?

thank you so much


________________________________
Da: avkolesnikov <***@yahoo.com>
A: ***@yahoogroups.com
Inviato: Venerdì 24 Maggio 2013 10:37
Oggetto: [COMSOL_Users] Re: CFD Module



 

Hi Nunzio,

You dont have to include pipe walls into your model (and therefore you dont need to define material property for the pipe).

Just model turbulent flow in 2D axisymmetrical domain (that is your pipe) with inlet, outlet and wall boundary conditions.

Andrei

Post by Nunzio Piro
hi guys,
I am a new member of this group. I recently started using COMSOL.
I have a problem with a CFD simulation. 
I must simulate a pipe flow with  water of costant diameter, D, equal to 0.004 m, and 0.2 m long.
I need to know the friction factor,  i need to use Turbolent Flow, k-epsilon (spf) and i study the tutorial model but i don't know where i can put the material propiety of the pipe that can define the friction factor. 
can someone help me? 
thank you  

[avkolesnikov]

Hi Nunzio,

You can determine friction factor from Darcy–Weisbach equation using water flow simulation in COMSOL to find out pressure loss in your pipe.

The D-W equation can be written in terms of pressure loss:
P_inlet-P_outlet=f_D * (L/D) * (rho*V^2)/2

where f_D is friction factor
L is pipe length
D is pipe inner diameter
rho is water density
V is average flow velocity

COMSOL will calculate outlet pressure P_outlet (the inlet pressure P_inlet you need to specify as inlet boundary condition), and outlet velocity V(r). You need to average outlet velocity profile V(r) to get V. You can use Boundary Probe function under Definitions in your model to obtain V.

Andrei

Post by Nunzio Piro
Hi Andrei,
i model turbolent flow (turbolent flow, k-epsilon phisics) in 2D. i create 3 triangles, one for water flow and two for pipe. i select iron for pipe. i define inlet, outlet conditions. the simulation is ok. 
i want know the friction factor that i want compare with the results that came from pipe flow phisics.
how can i valuete the friction factor in turbolent flow, k-epsilon?
thank you so much
________________________________
Inviato: Venerdì 24 Maggio 2013 10:37
Oggetto: [COMSOL_Users] Re: CFD Module
 
Hi Nunzio,
You dont have to include pipe walls into your model (and therefore you dont need to define material property for the pipe).
Just model turbulent flow in 2D axisymmetrical domain (that is your pipe) with inlet, outlet and wall boundary conditions.
Andrei

Post by Nunzio Piro
hi guys,
I am a new member of this group. I recently started using COMSOL.
I have a problem with a CFD simulation. 
I must simulate a pipe flow with  water of costant diameter, D, equal to 0.004 m, and 0.2 m long.
I need to know the friction factor,  i need to use Turbolent Flow, k-epsilon (spf) and i study the tutorial model but i don't know where i can put the material propiety of the pipe that can define the friction factor. 
can someone help me? 
thank you  

[Tammy]

The friction factors are empirically derived relations that are related to the roughness of the wall of the geometry that the fluid is flowing in. If one were to develope a CFD model using a semi-empirical model like the k-epsilon model, it would be expected that a geometry modeled with a rough wall would be able accurately reproduce the relations of the friction factor charts. The closest you could get to modeling a fully rough wall would be to model the velocity at the wall as zero. To simulate wall conditions other than fully rough you would have to define some slip velocity at the wall. There is no place to input the friction factor into the k-epsilon model.

Post by Nunzio Piro
hi guys,
I am a new member of this group. I recently started using COMSOL.
I have a problem with a CFD simulation. 
I must simulate a pipe flow with  water of costant diameter, D, equal to 0.004 m, and 0.2 m long.
I need to know the friction factor,  i need to use Turbolent Flow, k-epsilon (spf) and i study the tutorial model but i don't know where i can put the material propiety of the pipe that can define the friction factor. 
can someone help me? 
thank you  

[Thanh Long Vu]

Hi all,
I have a problem a conduct where it decompose solid phase and fluid phase, so I have a heat source in the solid phase. For the boundary condition I put the isotherm temperature at inlet for the fluid phase and all others it's adiabatic condition (flux=0). Normally, the heat flux go out only the fluid phase because all faces of solid phase are adiabatic but Comsol give the heat flux out also the inlet face of solid phase. I think it's not physic. Can someone help me ? 

Thanks in advance


Long VU




________________________________
From: Tammy <***@yahoo.com>
To: ***@yahoogroups.com
Sent: Friday, May 24, 2013 3:55 AM
Subject: [COMSOL_Users] Re: CFD Module



 
The friction factors are empirically derived relations that are related to the roughness of the wall of the geometry that the fluid is flowing in. If one were to develope a CFD model using a semi-empirical model like the k-epsilon model, it would be expected that a geometry modeled with a rough wall would be able accurately reproduce the relations of the friction factor charts. The closest you could get to modeling a fully rough wall would be to model the velocity at the wall as zero. To simulate wall conditions other than fully rough you would have to define some slip velocity at the wall. There is no place to input the friction factor into the k-epsilon model.

Post by Nunzio Piro
hi guys,
I am a new member of this group. I recently started using COMSOL.
I have a problem with a CFD simulation. 
I must simulate a pipe flow with  water of costant diameter, D, equal to 0.004 m, and 0.2 m long.
I need to know the friction factor,  i need to use Turbolent Flow, k-epsilon (spf) and i study the tutorial model but i don't know where i can put the material propiety of the pipe that can define the friction factor. 
can someone help me? 
thank you  

[nunziopiro]

hi guys,
I am a new member of this group. I recently started using COMSOL.
I have a problem with a CFD simulation.
I must simulate a pipe flow with water of costant diameter, D, equal to 0.004 m, and 0.2 m long.
I need to know the friction factor, i use Turbolent Flow, k-epsilon (spf) and i study the tutorial model but i don't know where i can put the material propiety of the pipe that can define the friction factor.
can someone help me?

thank you

[Nunzio Piro]

Hi guys,
i read on comsol's forum many discussions. in one of this i read that the friction factor in turbolence model (Turbolent Flow, k-epsilon) can be varied with the parameter B that appears in Turbolence Model Parameters. 
Do you know something about this? In particular, do you know as it come out? 

thank you

Nunzio Piro


________________________________
Da: Nunzio Piro <***@yahoo.it>
A: "***@yahoogroups.com" <***@yahoogroups.com>
Inviato: Giovedì 23 Maggio 2013 23:06
Oggetto: CFD Module



hi guys,
I am a new member of this group. I recently started using COMSOL.
I have a problem with a CFD simulation. 
I must simulate a pipe flow with  water of costant diameter, D, equal to 0.004 m, and 0.2 m long.
I need to know the friction factor,  i need to use Turbolent Flow, k-epsilon (spf) and i study the tutorial model but i don't know where i can put the material propiety of the pipe that can define the friction factor. 
can someone help me? 

thank you