Help needed

shaswat · January 26, 2012, 04:18

Dear all

I am new to CFX. I am doing the tutorial 12 flow in a catalytic converter.
I have a question in "creating porous domain"

As in the tutorial They have introduced

Basic setting > fluid and particle definition>Fluid 1>Material> Air Ideal gas

My question is

1. Why do they put "Air Ideal gas" instead of porous material honeycomb ceramic material?

Thank you

Regards
Shashwat

ghorrocks · January 26, 2012, 06:07

The material they define is the fluid. You do not define a material for the cat converter, instead you merely define resistance coefficients.

shaswat · January 27, 2012, 02:10

Dear friend

I am new to CFX. I am doing the tutorial 12 flow in a catalytic converter.
I have a question in "setting initial values" in the catalytic housing

How come they set the initial velocity -2.8m/s.? why is not zero along the Z direction?

As far as my knowledge is concerned, -ve sign indicates that the flow is in the opposite direction.

How did they calculate the initial velocity?

Please clarify

Thank you

Regards

Shashwat

energy382 · January 27, 2012, 02:41

Do you also read the Tutorial!? That may help

12.6.6. Setting Initial Values

A sensible guess for the initial velocity is the expected velocity through the catalyst housing. You can assume incompressible flow and apply conservation of mass to obtain an approximate velocity of 2.8 [m s^-1] through the housing based on the following known information:
The inlet velocity: 25 [m s^-1]
The cross sectional area of the inlet and housing, which can be determined using the function calculator in CFD-Post: 0.001913 m^2 and 0.024039 m^2 respectively
The porosity of the honeycomb structure: 70%

January 26, 2012, 04:18	Help needed	#1
shaswat Senior Member Shashwat Join Date: Nov 2011 Posts: 107 Rep Power: 14	Dear all I am new to CFX. I am doing the tutorial 12 flow in a catalytic converter. I have a question in "creating porous domain" As in the tutorial They have introduced Basic setting > fluid and particle definition>Fluid 1>Material> Air Ideal gas My question is 1. Why do they put "Air Ideal gas" instead of porous material honeycomb ceramic material? Thank you Regards Shashwat

January 27, 2012, 02:10	help needed	#3
shaswat Senior Member Shashwat Join Date: Nov 2011 Posts: 107 Rep Power: 14	Dear friend I am new to CFX. I am doing the tutorial 12 flow in a catalytic converter. I have a question in "setting initial values" in the catalytic housing How come they set the initial velocity -2.8m/s.? why is not zero along the Z direction? As far as my knowledge is concerned, -ve sign indicates that the flow is in the opposite direction. How did they calculate the initial velocity? Please clarify Thank you Regards Shashwat

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January 26, 2012, 06:07		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	The material they define is the fluid. You do not define a material for the cat converter, instead you merely define resistance coefficients.

January 27, 2012, 02:41		#4
energy382 Senior Member Christoph Join Date: May 2011 Location: Germany Posts: 182 Rep Power: 17	Do you also read the Tutorial!? That may help 12.6.6. Setting Initial Values A sensible guess for the initial velocity is the expected velocity through the catalyst housing. You can assume incompressible flow and apply conservation of mass to obtain an approximate velocity of 2.8 [m s^-1] through the housing based on the following known information: The inlet velocity: 25 [m s^-1] The cross sectional area of the inlet and housing, which can be determined using the function calculator in CFD-Post: 0.001913 m^2 and 0.024039 m^2 respectively The porosity of the honeycomb structure: 70%