Learning Forum

[zhangdongjie]

Recently, I was simulating the nozzle with high kn number. Originally, I wanted to write UDF, but I see that some people say that the effect of low pressure boundary slip is very good.

But low pressure boundary slip is like only works in 3D. How can I open this button in 2D?

[Amine Ben Hadj Ali]

You extend your 2D case in the depth and use there one cell or more and then apply symmetry BC on the sides. Or you implement the whole things using UDF.n

[Amine Ben Hadj Ali]

Moreover the option is available for 2D cases too.n

[zhangdongjie]

Moreover the option is available for 2D cases too./forum/discussion/comment/102608#Comment_102608

Thank you very much for your reply, which has helped me a lot. But how to open the 'low - pressure boundary slip' button in 2D?n

[Amine Ben Hadj Ali]

In the same panel as for 3D under Viscous Models Panel.n

[zhangdongjie]

In the same panel as for 3D under Viscous Models Panel./forum/discussion/comment/102747#Comment_102747

Thank you for taking the trouble to answer my questions. However, I can't find the 'low pressure boundary slip' button in the 2D modelnn

[zhangdongjie]

In the same panel as for 3D under Viscous Models Panel./forum/discussion/comment/102747#Comment_102747

I think I may have made a mistake. In the case of 2D and 3D, 'low pressure boundary slip' is available. but when I chose 'density based' instead of 'pressure based'. 'Low pressure boundary slip' disappeared again.n

[Rob]

/forum/discussion/9339/lpbs-conditions#latestn

[Amine Ben Hadj Ali]

Not available with density based solver.n

[zhangdongjie]

Not available with density based solver./forum/discussion/comment/102830#Comment_102830

I read the guidance document of fluent and benefited a lot. But I still wonder, is low pressure boundary slip not applicable under 'density based'? Is it because the compressible flow velocity is too high?n

[Rob]

It's not available. That means it's not coded to work, whether it is applicable is a different question. n

[Amine Ben Hadj Ali]

Is not implemented but you can code it on your own.n

[zhangdongjie]

It's not available. That means it's not coded to work, whether it is applicable is a different question./forum/discussion/comment/102898#Comment_102898

It seems that we can only use UDF to solve this problem, but I have a question. I can load the UDF of Velocity slip on the specific shear. Where is the UDF of temperature jump  loaded?nn

[zhangdongjie]

Is not implemented but you can code it on your own./forum/discussion/comment/102901#Comment_102901

It seems that we can only use UDF to solve this problem, but I have a question. I can load the UDF of Velocity slip on the specific shear. Where is the UDF of temperature jump loaded?nn

[Rob]

Thermal tab, you should be able to attach it where it says constant in the above. n

[zhangdongjie]

Thermal tab, you should be able to attach it where it says constant in the above./forum/discussion/comment/102922#Comment_102922

Hello, excuse me, is the UDF of temperature jump loaded here?n

[Amine Ben Hadj Ali]

I guess for that you require a DEFINE_HEAT_FLUX Macro or just use Pressure Based Solver and not using Density Based Solver. Is there any reason why you want to use DBS?n

[zhangdongjie]

I guess for that you require a DEFINE_HEAT_FLUX Macro or just use Pressure Based Solver and not using Density Based Solver. Is there any reason why you want to use DBS?/forum/discussion/comment/103412#Comment_103412

 My simulated Mach number is more than 3，the velocity of air is 400 m / s. If i use 'pressure based', it may not be accuraten

[Amine Ben Hadj Ali]

I do no think so. Pressure based solver are used for supersonic flows too.n

[zhangdongjie]

I do no think so. Pressure based solver are used for supersonic flows too./forum/discussion/comment/103453#Comment_103453

Thank you. Can pressure based solver simulate compressible flow? Is the result accurate?n

[Amine Ben Hadj Ali]

Yes and accurate. Our other Flagship CFD Product, Ansys CFX, does only have Pressure Based Solver and it is serving all purposes.n

[Jie Wei Yee]

Hi, I'm a undergraduate student. I want to simulate a thermal transpiration flow in a microchannel but I don't know the udf for velocity slip and temperature jump. Anyone can share to me? Thank you.