I need to know how to set the boundary layer thickness of an inlet flow boundary condition in FLUENT. The simulated flow has an inlet Mach number of 0.7 which could not be treated as an in compressible flow. Thus, using pressure inlet condition will be more convenient to use in such case. I can not figure out how to set the boundary layer thickness with inlet pressure boundary.
With my regards,
Ahmed
I am not sure I understand your question. You are talking about setting the boundary layer IN the inlet patch?
If that is the case, I am not sure you can do it: a boundary layer can be inserted only in a wall patch. I guess that the only think you could do is to introduce an inlet velocity profile which takes into account the existence of the boundary layers.
I am not sure I understand your question. You are talking about setting the boundary layer IN the inlet patch?
If that is the case, I am not sure you can do it: a boundary layer can be inserted only in a wall patch. I guess that the only think you could do is to introduce an inlet velocity profile which takes into account the existence of the boundary layers.
Dears,
Indeed the option b proposed by Prof. Jaafar is a very common and valid option.
But a word of caution is needed: indeed a boundary layer will develop in the CFD simulation if you leave it enough 'space' in your extension. However, how long this extension has to be is a difficult evaluation. For channel flow-like situation a good rule of thumb comes from the following equation for the entry length:
Extension > 0.05 Re D_h
where D_h is your hydraulic diameter. It is easy to notice that for high Reynolds number this extension is generally very long. This is to say that if you have even a rough estimation of the shape of the velocity profile at your inlet... use it!
Thanks Dr.Mendez and Dr.Jaafar for your answers. But I need to know if it is possible to set a value for boundary layer thickness at inlet by using a UDF which gives a distribution of inlet stagnation pressure. And this will be instead of using inlet velocity boundary ??
Sorry Ahmed, I missunderstood your question. You do not want to know how to put the boundary layer 'technically', in the software, but you want to know what boundary layer thiskness you should introduce in your simulation. Right? in this case I guess we need more information on your simulation. Could you provide a sketch?
In any case, I do not see how to introduce this from a pressure inlet condition. I guess you will have to introduce a velocity profile, which shape features the presence of a boundary layer.
Hi. I know that the first question was for inlet B.C in fluent but If you please can any one help me here?
I'm new in openfoam and I'm trying to simulate the air flow inside a rectangular duct using LES in which WALE model as a SGS model to study the bypass transition inside the duct. So, Do any one know how to generate homogeneous turbulent flow at the inlet with specific turbulent intensity?
By the way, I'm using pimpleFoam
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