orthotropic viscous resistance

chaudhry_hashim · July 16, 2014, 06:16

hi i want add orthotropic viscous resistance in the downstrean duct of fan for the calclation of pressure drop Kindly guide me at what distance should i create this resistance, should I put at the end of the downstream duct .
As far as I know I have to give value in the porous viscous resistance

me3840 · July 17, 2014, 01:32

You can enter in a porous inertial and viscous resistance, but they should be calculated based on a porous media's pressure loss response to a certain velocity field.

If you punch in the tensor type as axisymmetric tensor you can define a streamwise and cross-stream dimension which will suffice for your orthotropic resistance.

chaudhry_hashim · July 17, 2014, 02:55

Thanks for your guidance how can I find these values is there any specific formulas for that, the value I have to give as a axial component is the pressure drop with respect to the volume flow rate or velocity in the fan curve that I have.

Thankyou so much for your precious time

me3840 · July 17, 2014, 23:35

Pressure drop on a fan curve? That doesn't make any sense. Fans put energy into flows. The pressure should rise.

chaudhry_hashim · July 18, 2014, 01:57

I am sorry I mean I have curve pressure rise vs flow rate so should I put Pressure rise value in the axial component value with respect to mass flow rate I am giving at the inlet ? and I put this resistance at the end of the downstream duct in the z-direction because my duct is along z-direction just before the pressure outlet is it ok ?

me3840 · July 20, 2014, 22:23

I'm still confused. What does a porous media have to do with a fan? They do different things.

chaudhry_hashim · July 21, 2014, 02:50

actually i am trying to create a fan curve at different flow rates so for that reason i put some resistance at the end of downstream duct but its not really work i think and now i am just focusing on what you told me i made exruded duct on both side of the fan and boundary condition i am using is pressure outlet as inlet and same for outlet. I just fixed the pressure specification to total pressure (0.0 Pa) at inlet and outlet to static but i am confused what value should I give at outlet I just have fan curve from the manufacturer. I am measuring the massflowrate total and static pressures at 10 times of fan dia.

July 16, 2014, 06:16	orthotropic viscous resistance	#1
chaudhry_hashim Member hashim chaudhry Join Date: Jun 2014 Location: turkey Posts: 46 Rep Power: 11	hi i want add orthotropic viscous resistance in the downstrean duct of fan for the calclation of pressure drop Kindly guide me at what distance should i create this resistance, should I put at the end of the downstream duct . As far as I know I have to give value in the porous viscous resistance

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July 17, 2014, 01:32		#2
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 24	You can enter in a porous inertial and viscous resistance, but they should be calculated based on a porous media's pressure loss response to a certain velocity field. If you punch in the tensor type as axisymmetric tensor you can define a streamwise and cross-stream dimension which will suffice for your orthotropic resistance.

July 17, 2014, 02:55	hi	#3
chaudhry_hashim Member hashim chaudhry Join Date: Jun 2014 Location: turkey Posts: 46 Rep Power: 11	Thanks for your guidance how can I find these values is there any specific formulas for that, the value I have to give as a axial component is the pressure drop with respect to the volume flow rate or velocity in the fan curve that I have. Thankyou so much for your precious time

July 17, 2014, 23:35		#4
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 24	Pressure drop on a fan curve? That doesn't make any sense. Fans put energy into flows. The pressure should rise.

July 18, 2014, 01:57	hi	#5
chaudhry_hashim Member hashim chaudhry Join Date: Jun 2014 Location: turkey Posts: 46 Rep Power: 11	I am sorry I mean I have curve pressure rise vs flow rate so should I put Pressure rise value in the axial component value with respect to mass flow rate I am giving at the inlet ? and I put this resistance at the end of the downstream duct in the z-direction because my duct is along z-direction just before the pressure outlet is it ok ?

July 20, 2014, 22:23		#6
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 24	I'm still confused. What does a porous media have to do with a fan? They do different things.

July 21, 2014, 02:50	hi	#7
chaudhry_hashim Member hashim chaudhry Join Date: Jun 2014 Location: turkey Posts: 46 Rep Power: 11	actually i am trying to create a fan curve at different flow rates so for that reason i put some resistance at the end of downstream duct but its not really work i think and now i am just focusing on what you told me i made exruded duct on both side of the fan and boundary condition i am using is pressure outlet as inlet and same for outlet. I just fixed the pressure specification to total pressure (0.0 Pa) at inlet and outlet to static but i am confused what value should I give at outlet I just have fan curve from the manufacturer. I am measuring the massflowrate total and static pressures at 10 times of fan dia.