Re: [sparta-users] Boundary condition, pressure drops drasticaly around the outlet

[Vahid J. <ja...@hs...>]

Hey Georgii,

thank you so much for your answer. That was also my first thought, but 
as you can see from the pictures below, if I extend the half body and 
the computational dmoain correspondingly, the pressure drop will be 
postponed furthire doenstream near the outlet boundary again.

And even if there is an effect of boundary layer (or even boundary layer 
separation) don't you think the pressure should remain constant and not 
fall drastically? And How should I define in SPARTA the outflow at xhi?

Thank you very much and

Beste Grüße,
Vahid Jafari

Am 2023-06-13 13:12, schrieb geo...@dl...:

> Dear Vahid,
> 
> On first thought, it seems to have to do with the boundary layer and
> outflow condition: you have a supersonic outflow at xhi, but the
> boundary layer is not necessarily supersonic.
> 
> For smaller values of the accommodation coefficient you have (mostly)
> specular reflection, which given the relatively small angle of the
> body still retains enough velocity in the x direction to provide a
> supersonic flow in the slip layer.
> 
> Mit freundlichen Grüßen
> Dr. Georgii Oblapenko
> Postdoctoral Researcher
> Alexander von Humboldt Stiftung Fellow
> Institut für Aerodynamik und Strömungstechnik
> 
> Deutsches Zentrum für Luft- und Raumfahrt (DLR)
> -------------------------
> 
> From: Vahid Jafari <ja...@hs...>
> Sent: 12 June 2023 12:57:47
> To: spa...@li...
> Subject: [sparta-users] Boundary condition, pressure drops drasticaly
> around the outlet
> 
> Deal all,
> 
> I am a Ph.D. student researcher at  Helmut-Schmidt university in
> Hamburg, working with SPARTA for hypersonic flow purposes. However, I
> am having some issues with the boundary condition at outlet. I have a
> 2d axisymmetric flow filed around a half body like in the picture
> below. We evaluate the data along the white line in the picture below.
> 
> The problem is that the pressure drops drastically (which is
> unrealistic) around the outlet as seen in the picture below.
> 
> It happens for an accommodation coefficient of 1. By decreasing the
> accommodation coefficient, this vanishes such that for an
> accommodation coefficient smaller than 0.2 it completely disappears.
> 
> Do you have an explanation for that or do I configure something wrong
> here. Enclosed you can also find the input files
> 
> Thank you for your help in advance.
> 
> Kind Regards,
> 
> Vahid Jafari
> 
> --
> 
> -- M.Sc. Vahid Jafari
> 
> -- Chair for High Performance Computing
> 
> -- Helmut-Schmidt-Universität Hamburg
> 
> -- Holstenhofweg 85/ Postfach 70 08 22
> 
> -- 22043 Hamburg/Germany
> 
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> 
> --       Phone:  +49 40 6541-3382
> 
> --       E-mail: ja...@hs...
> 
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> 
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