cfd post chart undef??

VincentWille · April 9, 2013, 15:52

Hello

I designed an axial pump: stator, rotor, diffusor. Now i want to plot the average static pressure distribution along the axial direction (in my case z axis).

I've created a turbo line at 0.5 span.

location = turbo line 1
x axis = Z
y axis = pressure

but when i plot the chart it seems incomplete. It only plots values in certain intervals...
When i export the .csv file to excel it says "undef" at thoses intervals...

Does anyone knows what the problem is?

ghorrocks · April 9, 2013, 20:03

Are those regions in cavities in the mesh? Maybe the line goes through a blade or the central spinner or something like that.

VincentWille · April 11, 2013, 08:03

Indeed the turbo line goes trough the blades of the rotor. How do I plot the pressure rise across the rotor then?

ghorrocks · April 11, 2013, 08:11

You need to have a careful think about exactly what you want. The pressure along a line which passes straight through a rotor is not very useful as flow cannot take that path.

Do you want the average pressure over the front versus back faces of the rotor? Or the pressure along a streamline through the device? Or average pressures across the flow at different cross sections in the pipes leading into and out of the device?

VincentWille · April 11, 2013, 08:52

I want to plot the pressure along a streamline across the device.

I think i found something that works. I used a polyline in the rotor to plot de pressure values.

Or can you create a streamline as a locations for the chart?

ghorrocks · April 11, 2013, 19:43

You can use any scalar as the X or Y variable in a chart. Scalar variables include length along a streamline.

So yes, you can draw pressure along the length of a streamline as an XY chart.

April 9, 2013, 15:52	cfd post chart undef??	#1
VincentWille New Member Vincent Wille Join Date: Nov 2012 Posts: 3 Rep Power: 13	Hello I designed an axial pump: stator, rotor, diffusor. Now i want to plot the average static pressure distribution along the axial direction (in my case z axis). I've created a turbo line at 0.5 span. location = turbo line 1 x axis = Z y axis = pressure but when i plot the chart it seems incomplete. It only plots values in certain intervals... When i export the .csv file to excel it says "undef" at thoses intervals... Does anyone knows what the problem is? Last edited by VincentWille; April 9, 2013 at 17:27.

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April 9, 2013, 20:03		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,852 Rep Power: 144	Are those regions in cavities in the mesh? Maybe the line goes through a blade or the central spinner or something like that.

April 11, 2013, 08:03		#3
VincentWille New Member Vincent Wille Join Date: Nov 2012 Posts: 3 Rep Power: 13	Indeed the turbo line goes trough the blades of the rotor. How do I plot the pressure rise across the rotor then?

April 11, 2013, 08:11		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,852 Rep Power: 144	You need to have a careful think about exactly what you want. The pressure along a line which passes straight through a rotor is not very useful as flow cannot take that path. Do you want the average pressure over the front versus back faces of the rotor? Or the pressure along a streamline through the device? Or average pressures across the flow at different cross sections in the pipes leading into and out of the device?

April 11, 2013, 08:52		#5
VincentWille New Member Vincent Wille Join Date: Nov 2012 Posts: 3 Rep Power: 13	I want to plot the pressure along a streamline across the device. I think i found something that works. I used a polyline in the rotor to plot de pressure values. Or can you create a streamline as a locations for the chart?

April 11, 2013, 19:43		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,852 Rep Power: 144	You can use any scalar as the X or Y variable in a chart. Scalar variables include length along a streamline. So yes, you can draw pressure along the length of a streamline as an XY chart.