Calculating fluid recirculation at an outlet in transient analysis

HeatK · November 4, 2020, 11:21

I'm currently modelling a pipe, which has a sinusoidal input velocity and a 0Pa outlet. In the pipe, there is inserted a two way tube which has both an inlet and outlet at its tip.

Both the pipe and tube use the same fluid. The fluid input from both the pipe and tube mix together inside the pipe, before some exits through the pipe, and the rest exits through the tube.

The pipe and tube are both set up as one domain.

I want to be able to determine what percentage of the fluid exiting through the tube's outlet has also come from its inlet.

I have looked at using particle tracking, using tutorial 29 however this doesn't seem to be quite the right application for that. I may of course have missed something.

If anyone could be of any help, it would be greatly appreciated, thanks

AtoHM · November 4, 2020, 13:07

You can create a new scalar variable (passive scalar) for each inlet and insert it with the flow. Then you can monitor how much of it leaves at the respective outlet. You need to add it in the domain settings and specify the transport equation to be solved.

HeatK · November 4, 2020, 13:17

How do i go about creating a passive scalar? or is there a tutorial which details this? Been looking through and can't see anything

AtoHM · November 4, 2020, 15:33

I have no time to look up all the steps right now, but I found this, which seems to describe the steps quite well:
Tracer Analysis in CFX

November 4, 2020, 11:21	Calculating fluid recirculation at an outlet in transient analysis	#1
HeatK New Member Charlie Heaton Join Date: Nov 2020 Posts: 5 Rep Power: 6	I'm currently modelling a pipe, which has a sinusoidal input velocity and a 0Pa outlet. In the pipe, there is inserted a two way tube which has both an inlet and outlet at its tip. Both the pipe and tube use the same fluid. The fluid input from both the pipe and tube mix together inside the pipe, before some exits through the pipe, and the rest exits through the tube. The pipe and tube are both set up as one domain. I want to be able to determine what percentage of the fluid exiting through the tube's outlet has also come from its inlet. I have looked at using particle tracking, using tutorial 29 however this doesn't seem to be quite the right application for that. I may of course have missed something. If anyone could be of any help, it would be greatly appreciated, thanks

November 4, 2020, 13:07		#2
AtoHM Senior Member M Join Date: Dec 2017 Posts: 701 Rep Power: 12	You can create a new scalar variable (passive scalar) for each inlet and insert it with the flow. Then you can monitor how much of it leaves at the respective outlet. You need to add it in the domain settings and specify the transport equation to be solved. HeatK likes this.

November 4, 2020, 15:33		#4
AtoHM Senior Member M Join Date: Dec 2017 Posts: 701 Rep Power: 12	I have no time to look up all the steps right now, but I found this, which seems to describe the steps quite well: Tracer Analysis in CFX HeatK likes this.

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November 4, 2020, 13:17		#3
HeatK New Member Charlie Heaton Join Date: Nov 2020 Posts: 5 Rep Power: 6	How do i go about creating a passive scalar? or is there a tutorial which details this? Been looking through and can't see anything