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#1 |
Guest
Posts: n/a
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The solution I am trying to get is the buoyant flow with 90 degree deflection. I chose k-e turbulence model for this. Someone told me to choose 'SST' model instead, while, according to CFX manual, I think that 'SSG' model might be suitable than 'SST'. Do anyone have any idea?
Anyway, I have the problem with 'y plus' in CFX-Post. I read from some book that y plus is the important parameter to determine if your grid system is OK. However I am not sure which position along the flow path should I use to get y plus, at the inlet? or at the outlet? or at any position that we're sure it is fully developed. I create the line perpendicular to the wall at many points along the flow path, and then set them to display in variable mode. Y plus is the chosen variable. I don't understand the results. At all points, y plus are constant along the line and aren't defined in the far wall region. Do anyone have any idea for this? |
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#2 |
Guest
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Y plus is the distance of the first node away from the wall,so it must be constant for a perticular wall.
It is the criterion to check your mesh quality. Every turbulance model solves wall functions,as described in helps and uses Y+ to solve,so it is important to have its values within limits for the model. |
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#3 |
Guest
Posts: n/a
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Try to plot a contour plot for Y+ at your walls. That would give you an idea about your Y+ , and not a line through your domain.Looks like you have no idea about what Y+, try to read through the posts here, they are plenty of them and and they are very helpful.
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#4 |
New Member
Manpreet
Join Date: Jan 2014
Posts: 14
Rep Power: 12 ![]() |
Hi guys,
I am working on project Flow analysis through Rotor 37. I have done meshing in turbogrid by following tutorials. Could anyone let me know how to calculate Y plus or how to plot values of Y plus at the wall in CFD post. What should I read for this any book or tutorials?? Thanks Manpreet Singh manpreet_singh_er@yahoo.co.in |
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#5 |
Senior Member
Bruno
Join Date: Mar 2009
Location: Brazil
Posts: 277
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The CFX documentation has lots of tutorials that show how to calculate variables and plot them on charts. Take a look at them. Seriously.
---- To see the the values of a variable on the wall, just enable the wall and color it by such variable. For charts, you'll need to create a line over the wall. This can be done by creating a polyline of the intersection between a plane and a wall. Take a look at the tutorials. |
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#6 |
New Member
Manpreet
Join Date: Jan 2014
Posts: 14
Rep Power: 12 ![]() |
Thanks Brunoc,
Could you please lt me know specific tutorial to follow for plotting y plus and also plz let me now which turbulence model do I need to use for my model .My model is NASA rotor 37 having transonic flow in it and I am working with CFX solver, do u know how solver solve variables I mean its along nodes on boundaries of control volume or at center. Kindly consider my request. I really appreciate help being provided by you. Thanks |
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#7 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,816
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Have a look at the contents of the tutorials to determine which is best. Even better, do them all.
Control volumes - this is all discussed in the CFX documentation theory manual. If you have no idea about turbulence models then use the SST model. Only consider a different model if you have good reason to do so. |
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