Export Wall Shear Stress Data

trooken · February 5, 2019, 05:39

I have an axisymmetric 2D simulation in Ansys Fluent, and am trying to export wall shear stress at a particular wall. If I draw a contour plot of wall shear stress for just that wall boundary, then I can successfully plot the contour and see how wall shear stress varies. However, if I try to create an XY plot of wall shear stress at that same wall, it says "Cannot plot along curve length of "wall"".

EDIT: I think I have found out that it cannot plot the XY plot if the line gets "too close" to the axis of rotation. Is there any way to obtain the wall shear stress data near the axis of rotation?

LuckyTran · February 5, 2019, 09:46

What are you trying to do? There is no wall and hence no wall shear stress on the axis, it's an axis... Are you trying to plot some other shear stress an arbitrary line or trying to plot the wall shear stress on a wall?

trooken · February 5, 2019, 09:50

Sorry, I was not clear
I essentially have a cylinder, and want to find the wall shear stress on the bottom face on the cylinder. My simulation is axisymmetric. However, FLUENT will not allow me to produce an XY Plot of this face unless you start sufficiently far away from the centre of the bottom face (where the axis of symmetry is)
I am essentially trying to plot the wall shear stress on the surface perpendicular to the axis

LuckyTran · February 5, 2019, 10:10

Yeah I don't follow... You have a cylinder.... The walls of the cylinder aren't near the axis. So what is your problem? Are you trying to plot the interior shear stress and not the wall shear stress?

trooken · February 5, 2019, 10:12

I would like to find the wall shear stress on the surface on the base of the cylinder. This surface is perpendicular to the axis of symmetry. For an XY plot, FLUENT is not able to give you the wall shear stress if your desired line where you want the stresses to be evaluated begins too close to the axis of symmetry of the cylinder.

LuckyTran · February 5, 2019, 10:48

Picture please.

RaiderDoctor · February 5, 2019, 15:09

Okay, so you want to plot wall shear stress at the axis of rotation? If this is essentially a cylinder, and there is no wall in the center of the domain, then how exactly can you get wall shear stress?

I think I understand what you want to do, however. You are trying to produce a graph of the viscous shear stress, much like this figure, right?

Well, according to the Fluent manual, WSS can only be plotted on the cells adjacent to the wall. I think, for what you want to do, you might need to specify a field function (Plotting Shear Stress). If that's the case, you would have to re-run your simulation, though. You could post-process using another software, like Tecplot, but I don't have much experience with that.

February 5, 2019, 05:39	Export Wall Shear Stress Data	#1
trooken New Member Join Date: Feb 2019 Posts: 4 Rep Power: 7	I have an axisymmetric 2D simulation in Ansys Fluent, and am trying to export wall shear stress at a particular wall. If I draw a contour plot of wall shear stress for just that wall boundary, then I can successfully plot the contour and see how wall shear stress varies. However, if I try to create an XY plot of wall shear stress at that same wall, it says "Cannot plot along curve length of "wall"". EDIT: I think I have found out that it cannot plot the XY plot if the line gets "too close" to the axis of rotation. Is there any way to obtain the wall shear stress data near the axis of rotation?

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February 5, 2019, 09:46		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,665 Rep Power: 65	What are you trying to do? There is no wall and hence no wall shear stress on the axis, it's an axis... Are you trying to plot some other shear stress an arbitrary line or trying to plot the wall shear stress on a wall?

February 5, 2019, 09:50		#3
trooken New Member Join Date: Feb 2019 Posts: 4 Rep Power: 7	Sorry, I was not clear I essentially have a cylinder, and want to find the wall shear stress on the bottom face on the cylinder. My simulation is axisymmetric. However, FLUENT will not allow me to produce an XY Plot of this face unless you start sufficiently far away from the centre of the bottom face (where the axis of symmetry is) I am essentially trying to plot the wall shear stress on the surface perpendicular to the axis

February 5, 2019, 10:10		#4
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,665 Rep Power: 65	Yeah I don't follow... You have a cylinder.... The walls of the cylinder aren't near the axis. So what is your problem? Are you trying to plot the interior shear stress and not the wall shear stress?

February 5, 2019, 10:12		#5
trooken New Member Join Date: Feb 2019 Posts: 4 Rep Power: 7	I would like to find the wall shear stress on the surface on the base of the cylinder. This surface is perpendicular to the axis of symmetry. For an XY plot, FLUENT is not able to give you the wall shear stress if your desired line where you want the stresses to be evaluated begins too close to the axis of symmetry of the cylinder.

February 5, 2019, 10:48		#6
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,665 Rep Power: 65	Picture please.

February 5, 2019, 15:09		#7
RaiderDoctor Senior Member Join Date: Dec 2016 Posts: 152 Rep Power: 10	Okay, so you want to plot wall shear stress at the axis of rotation? If this is essentially a cylinder, and there is no wall in the center of the domain, then how exactly can you get wall shear stress? I think I understand what you want to do, however. You are trying to produce a graph of the viscous shear stress, much like this figure, right? Well, according to the Fluent manual, WSS can only be plotted on the cells adjacent to the wall. I think, for what you want to do, you might need to specify a field function (Plotting Shear Stress). If that's the case, you would have to re-run your simulation, though. You could post-process using another software, like Tecplot, but I don't have much experience with that.