Assigning pressure to closed fluid domains

Torque_Converter · August 26, 2012, 16:25

Ahh, makes alot more sense now why that would be of interest. That does have an impact on performance since the centrifugal force means fluid is only going to act on a smaller percentage on the blade (near the hub). Also, it might not be a bad idea to turn on bouyancy in that case as gravity may or may not have a significant impact at certain RPM's.
Generally the inlet/outlet is near the shaft for the turbine, with the inlet being generally on the pump side between stator and pump passage, and outlet being between turbine and stator passage. Periodic, so that helps alot, and you could use a "reasonable" set of boundary conditions to generate something like a matrix of solutions. 70-80 liters/min is a reasonable volume flow thru the TC, outlet pressure, hmmm, not 100% certain of that, but I guess you can take reasonable numbers like 50-90 psi and see what happens when paired with different inlet conditions.

Aladdin · August 26, 2012, 16:33

In your opening, Do I make pump inlet as an Inlet boundary condition with mass flow rate and stator exit as Outlet boundary condition with pressure or what do you think?

Torque_Converter · August 27, 2012, 07:15

The entrance and exit of the TC occurs at the hub (outer portion of the torus), but not towards the core/shell. Placing an inlet domain just on the hub in a small slit between stator/pump and outlet just on the hub between turbine/stator will work. This will be roughly perpendicular to the flow path within the TC.

Aladdin · August 28, 2012, 15:42

Your suggestion is a slit between the pump and stator as an inlet and an outlet on turbine hub. Why on hub? and how this is will be created in mesh?

Torque_Converter · August 28, 2012, 18:15

This image may help:
http://www.google.com/imgres?hl=en&s...,r:6,s:0,i:160

The fluid enters between transmission case and the pump (near where they meet). Fluid exits down from turbine/stator intersection between the transmission input shaft and transmission case. The basic device is called a ground sleeve. This allows fluid to come in and out at via the same central area, but in different channels. This is important for cooling.

As for meshing. If you are using bladegen/blade editor and turbogrid you can create inlet and outlet blocks by moving the pyramid shaped delimiters.
If you are not using turbogrid with bladegen/blade editor I HIGHLY reccomend using it. But if you aren't, then I assume you have an extracted fluid domain from a cad program. This will work fine, although not as efficiently. You will have to slice off a bit of a chunk at the stator to pump and turbine interfaces, make sure they are periodic and rotating with their respective turbine/stator/pump domain, but make the hub side of these blocks and inlet and then outlet condition as appropriate. How you do this depends on the CAD program, i.e. using perhaps planes or a sketch/extrude like in NX. You will have to play with this. Unfortunatly, getting good at manipulating CAD seems to be an important part of being a CFD analyst.

Aladdin · August 30, 2012, 14:06

I am actually using bladegen and turbogrid. Do blocks can be created in bladegen? I have no experience with doing this. I think I'll go with creating a CAD part and insert it between torque converter parts.

Torque_Converter · August 30, 2012, 14:36

It's actually fairly easy in turbogrid. I'll do my best to explain how to create these blocks so that you can have faces to apply inlet/outlet without disrupting the flow. If I fail to clarify anything there are a few turbogrid experts at CFX who can help you.

Basically once you export your points to turbogrid and open it up you will see at the inlet/outlet boundaries (really the interfaces between the TC components) that there are white pyramid shaped objects. If you drag these they will follow the hub/shroud lines and make a cut in the domain. These will be your inlet/outlet blocks.

These will need to be meshed, so when you go into your mesh definition control panel (or whatever its called) you will have to click on inlet/outlet domain. The last tab on that menu box will allow you to change the mesh conditions in these domains if you so wish.

Aladdin · August 30, 2012, 16:40

I think I got it. I'll try it and keep you updated. thanks for your comments. They are very helpful.

jsm · October 22, 2015, 09:51

This might be late reply. Can you please post the image of torque converter modeling with inlet and outlet. I am using bladegen and turbogrid and I cannot make inlet/outlet in turbogrid.

Vaaj · May 5, 2017, 18:53

Quote:

Originally Posted by ghorrocks

If the flow is incompressible in a closed domain the reference pressure is irrelevant. You can add any amount you like to it to get the reference pressure you want.

What if the closed domain consists of air at reduced pressure initially say 0.4 bar and I am charging it with air at 21 bar ? In that case how do I fill the closed domain with air at the specified pressure (do i just patch the values of pressure and temperature in that domain and that does the job?)

ghorrocks · May 6, 2017, 06:33

Over that pressure range I do not think you will be using the incompressible fluid assumption. So my comments from the previous post do not apply.

You would have to have to explain what you are trying to do before I can answer your question on how to model it. But please start a new thread to ask this question, it is a different question to this thread.

October 22, 2015, 09:51		#29
jsm Senior Member JSM Join Date: Mar 2009 Location: India Posts: 192 Rep Power: 20	This might be late reply. Can you please post the image of torque converter modeling with inlet and outlet. I am using bladegen and turbogrid and I cannot make inlet/outlet in turbogrid. __________________ With regards, JSM

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August 26, 2012, 16:25		#21
Torque_Converter Member Join Date: Jan 2012 Location: Edmonton, CA Posts: 87 Rep Power: 14	Ahh, makes alot more sense now why that would be of interest. That does have an impact on performance since the centrifugal force means fluid is only going to act on a smaller percentage on the blade (near the hub). Also, it might not be a bad idea to turn on bouyancy in that case as gravity may or may not have a significant impact at certain RPM's. Generally the inlet/outlet is near the shaft for the turbine, with the inlet being generally on the pump side between stator and pump passage, and outlet being between turbine and stator passage. Periodic, so that helps alot, and you could use a "reasonable" set of boundary conditions to generate something like a matrix of solutions. 70-80 liters/min is a reasonable volume flow thru the TC, outlet pressure, hmmm, not 100% certain of that, but I guess you can take reasonable numbers like 50-90 psi and see what happens when paired with different inlet conditions.

August 26, 2012, 16:33		#22
Aladdin New Member Aladdin Join Date: Jul 2012 Posts: 10 Rep Power: 13	In your opening, Do I make pump inlet as an Inlet boundary condition with mass flow rate and stator exit as Outlet boundary condition with pressure or what do you think?

August 27, 2012, 07:15		#23
Torque_Converter Member Join Date: Jan 2012 Location: Edmonton, CA Posts: 87 Rep Power: 14	The entrance and exit of the TC occurs at the hub (outer portion of the torus), but not towards the core/shell. Placing an inlet domain just on the hub in a small slit between stator/pump and outlet just on the hub between turbine/stator will work. This will be roughly perpendicular to the flow path within the TC.

August 28, 2012, 15:42		#24
Aladdin New Member Aladdin Join Date: Jul 2012 Posts: 10 Rep Power: 13	Your suggestion is a slit between the pump and stator as an inlet and an outlet on turbine hub. Why on hub? and how this is will be created in mesh?

August 28, 2012, 18:15		#25
Torque_Converter Member Join Date: Jan 2012 Location: Edmonton, CA Posts: 87 Rep Power: 14	This image may help: http://www.google.com/imgres?hl=en&s...,r:6,s:0,i:160 The fluid enters between transmission case and the pump (near where they meet). Fluid exits down from turbine/stator intersection between the transmission input shaft and transmission case. The basic device is called a ground sleeve. This allows fluid to come in and out at via the same central area, but in different channels. This is important for cooling. As for meshing. If you are using bladegen/blade editor and turbogrid you can create inlet and outlet blocks by moving the pyramid shaped delimiters. If you are not using turbogrid with bladegen/blade editor I HIGHLY reccomend using it. But if you aren't, then I assume you have an extracted fluid domain from a cad program. This will work fine, although not as efficiently. You will have to slice off a bit of a chunk at the stator to pump and turbine interfaces, make sure they are periodic and rotating with their respective turbine/stator/pump domain, but make the hub side of these blocks and inlet and then outlet condition as appropriate. How you do this depends on the CAD program, i.e. using perhaps planes or a sketch/extrude like in NX. You will have to play with this. Unfortunatly, getting good at manipulating CAD seems to be an important part of being a CFD analyst.

August 30, 2012, 14:06		#26
Aladdin New Member Aladdin Join Date: Jul 2012 Posts: 10 Rep Power: 13	I am actually using bladegen and turbogrid. Do blocks can be created in bladegen? I have no experience with doing this. I think I'll go with creating a CAD part and insert it between torque converter parts.

August 30, 2012, 14:36		#27
Torque_Converter Member Join Date: Jan 2012 Location: Edmonton, CA Posts: 87 Rep Power: 14	It's actually fairly easy in turbogrid. I'll do my best to explain how to create these blocks so that you can have faces to apply inlet/outlet without disrupting the flow. If I fail to clarify anything there are a few turbogrid experts at CFX who can help you. Basically once you export your points to turbogrid and open it up you will see at the inlet/outlet boundaries (really the interfaces between the TC components) that there are white pyramid shaped objects. If you drag these they will follow the hub/shroud lines and make a cut in the domain. These will be your inlet/outlet blocks. These will need to be meshed, so when you go into your mesh definition control panel (or whatever its called) you will have to click on inlet/outlet domain. The last tab on that menu box will allow you to change the mesh conditions in these domains if you so wish.

August 30, 2012, 16:40		#28
Aladdin New Member Aladdin Join Date: Jul 2012 Posts: 10 Rep Power: 13	I think I got it. I'll try it and keep you updated. thanks for your comments. They are very helpful.

May 6, 2017, 06:33		#31
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,692 Rep Power: 143	Over that pressure range I do not think you will be using the incompressible fluid assumption. So my comments from the previous post do not apply. You would have to have to explain what you are trying to do before I can answer your question on how to model it. But please start a new thread to ask this question, it is a different question to this thread.