Turbomachinery Domain Interfacing

exm5360 · July 2, 2020, 16:53

Hello,

I'm relatively new to CFD (I've been working with ANSYS for six months) and I'm working on a new project to model a propeller. I have three domains: two stationary for pipe inlet and pipe outlet and a rotating domain for the propeller. I keep running into an issue where my domain interfaces do not merge smoothly (from pipe inlet into the propeller and exiting at the pipe outlet). Would anyone who has a few more years experience be able to help a newcomer out to smoothly interface a stationary domain to a rotating domain?

ghorrocks · July 2, 2020, 20:08

What do you mean by "do not merge smoothly"? Please show what you mean on an image.

Gert-Jan · July 3, 2020, 04:25

Indeed we don't know what varaibles you are showing, so it is difficult to give advice. But can't it be that you are looking ar Velocity and Total Pressure? If so, then look at Velocity and Total Pressure in Stationary Frame.

exm5360 · July 6, 2020, 09:03

Apology for the ambiguity; let me rephrase the question: What is the most appropriate method to connect a stationary reference frame and a rotating reference frame? The pictures above shown is a pressure contour and a velocity streamline plot. There are three domains, two stationary reference frames (acting as pipe inlets and outlet) and the rotating reference frame in the middle. The pressure contour and velocity streamline do not have a smooth connectivity from one reference frame to another and was questioning how to appropriately connect a moving and stationary reference frame.

Gert-Jan · July 6, 2020, 09:49

As mentioned: you are looking at Velocity and Total Pressure. You should look at Velocity and Total Pressure in Stationary Frame.

Stel · July 15, 2020, 13:26

It is not clear what you mean by "smooth connectivity". If you mean the behavior of the streamlines and pressure contours, please have in mind that when transitioning from stationary to rotating domains CFD Post will assume by default that the Velocity from which it will calculate the streamlines assume the local frame of reference, which means that in the rotating frame it will "redraw" the streamlines orientation to the velocity in a rotating frame of reference. If you want to see a smooth transition in this sense, plot the streamlines using "Velocity in Stn Frame" as suggested above. Also, it is not clear in the image if the rotating domain was assumed as a 360 or only one passage. If you connect a 360 domain with a single-passage rotating domain CFX will employ pitch scale, which may cause some streamlines and contours to look disconnected since CFX will have to interpolate data across the interface.

July 2, 2020, 20:08		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	What do you mean by "do not merge smoothly"? Please show what you mean on an image. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

July 6, 2020, 09:03	Apology for ambiguity	#4
exm5360 New Member Evan Join Date: Jul 2020 Posts: 4 Rep Power: 6	Apology for the ambiguity; let me rephrase the question: What is the most appropriate method to connect a stationary reference frame and a rotating reference frame? The pictures above shown is a pressure contour and a velocity streamline plot. There are three domains, two stationary reference frames (acting as pipe inlets and outlet) and the rotating reference frame in the middle. The pressure contour and velocity streamline do not have a smooth connectivity from one reference frame to another and was questioning how to appropriately connect a moving and stationary reference frame.

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July 3, 2020, 04:25		#3
Gert-Jan Senior Member Gert-Jan Join Date: Oct 2012 Location: Europe Posts: 1,928 Rep Power: 28	Indeed we don't know what varaibles you are showing, so it is difficult to give advice. But can't it be that you are looking ar Velocity and Total Pressure? If so, then look at Velocity and Total Pressure in Stationary Frame.

July 6, 2020, 09:49		#5
Gert-Jan Senior Member Gert-Jan Join Date: Oct 2012 Location: Europe Posts: 1,928 Rep Power: 28	As mentioned: you are looking at Velocity and Total Pressure. You should look at Velocity and Total Pressure in Stationary Frame.

July 15, 2020, 13:26		#6
Stel Member Henrique Stel Join Date: Apr 2009 Location: Curitiba, Brazil Posts: 93 Rep Power: 17	It is not clear what you mean by "smooth connectivity". If you mean the behavior of the streamlines and pressure contours, please have in mind that when transitioning from stationary to rotating domains CFD Post will assume by default that the Velocity from which it will calculate the streamlines assume the local frame of reference, which means that in the rotating frame it will "redraw" the streamlines orientation to the velocity in a rotating frame of reference. If you want to see a smooth transition in this sense, plot the streamlines using "Velocity in Stn Frame" as suggested above. Also, it is not clear in the image if the rotating domain was assumed as a 360 or only one passage. If you connect a 360 domain with a single-passage rotating domain CFX will employ pitch scale, which may cause some streamlines and contours to look disconnected since CFX will have to interpolate data across the interface.