Fluent manipulation of 3rd axis(in paper) for 2D cases

mqasimali · June 25, 2013, 00:37

hi there,
i am currently modeling a flown channel where flow is in vertical direction i.e top to bottom.
i have given BC's of pressure at inlet and outlet.
what i have required to find out is the velocity.
i have came to know that Fluent by default takes the depth in paper for 2D geometries as 1 m, while the actual depth in paper is around 79mm, it is greatly affecting my velocity profiles in channels,
kindly suggest me any possible solution, can i adjust this depth to the actual one or have to try something else.
Regards

DonQuijote · June 25, 2013, 06:17

Hi!

I think there is a missunderstanding in what Fluent gives as 1 m depth. If you are modeling a 2D flow, you are assuming that flow conditions are constant/not relevant along the third edge. So, Fluent uses 1 m depth to give you some magnitudes that need of this component to be sense. For example, pressure along an area with 1 m depth reference.

To summarize, you can not be pretend to model a 3D flow in a 2D model if the third component is not constant, it has no sense. If your flow is approaxing to a 2D flow, then you can easily convert the required magnitudes to your real depth.

Hope it helps!
Regards

mqasimali · June 28, 2013, 02:10

thank you for your kind reply
so what you what meant is a 3D problem can be modeled as 2D when its properties are as such not dependent on the third axis that fluent consider as unit to give some sense.
now what do i think is in my case it is being dependent on the third axis.
im using pressure inlet condition and applying it on the line of a face but this pressure is actually dependent on the area into the paper
P=F/A, my actual area is 0.005 m^2 (length =0.079m, width=0.066m and this width is into the paper or you can say the third axis)
and if i consider what area fluent is considering it becomes length =0.079m and width=1m since fluent takes depth of one and thus increasing the area
so should i go for scaling of pressure????

June 25, 2013, 00:37	Fluent manipulation of 3rd axis(in paper) for 2D cases	#1
mqasimali New Member Qasim Ali Join Date: Mar 2013 Location: Islamabad, Pakistan Posts: 18 Rep Power: 13	hi there, i am currently modeling a flown channel where flow is in vertical direction i.e top to bottom. i have given BC's of pressure at inlet and outlet. what i have required to find out is the velocity. i have came to know that Fluent by default takes the depth in paper for 2D geometries as 1 m, while the actual depth in paper is around 79mm, it is greatly affecting my velocity profiles in channels, kindly suggest me any possible solution, can i adjust this depth to the actual one or have to try something else. Regards

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June 25, 2013, 06:17		#2
DonQuijote Member Join Date: Jun 2012 Posts: 32 Rep Power: 13	Hi! I think there is a missunderstanding in what Fluent gives as 1 m depth. If you are modeling a 2D flow, you are assuming that flow conditions are constant/not relevant along the third edge. So, Fluent uses 1 m depth to give you some magnitudes that need of this component to be sense. For example, pressure along an area with 1 m depth reference. To summarize, you can not be pretend to model a 3D flow in a 2D model if the third component is not constant, it has no sense. If your flow is approaxing to a 2D flow, then you can easily convert the required magnitudes to your real depth. Hope it helps! Regards

June 28, 2013, 02:10		#3
mqasimali New Member Qasim Ali Join Date: Mar 2013 Location: Islamabad, Pakistan Posts: 18 Rep Power: 13	thank you for your kind reply so what you what meant is a 3D problem can be modeled as 2D when its properties are as such not dependent on the third axis that fluent consider as unit to give some sense. now what do i think is in my case it is being dependent on the third axis. im using pressure inlet condition and applying it on the line of a face but this pressure is actually dependent on the area into the paper P=F/A, my actual area is 0.005 m^2 (length =0.079m, width=0.066m and this width is into the paper or you can say the third axis) and if i consider what area fluent is considering it becomes length =0.079m and width=1m since fluent takes depth of one and thus increasing the area so should i go for scaling of pressure????