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Anyone shed light on why this strange shock is forming?

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Old   May 1, 2020, 17:13
Default Anyone shed light on why this strange shock is forming?
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Matt
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Making an air intake, and I've got a shock forming where I certainly don't think it should be, resulting in my simulation being... bad to say the least.

This is what my simulation looks like currently: https://imgur.com/a/AtmtGIj

I'm planning for the three ramps to give oblique shocks, normal shock in the central bit, and diffuse out to the outlet at the end. This is pretty much exactly what I'm going for: https://imgur.com/a/5te0trA

I've deduced that it is the proximity of that top part of intake to the bottom part that causes this big normal shock to occur where its not supposed to. When I moved it twice as far away, the oblique shocks formed normally. The weird part is, in the 'target' image above, based on their dimensions, their two parts were closer together than mine were?

Can anyone see a reason why this proximity would result in this? Its also pretty strange that whilst the shock is formed by the top part I'd assume since its movement affects whether it forms or not, it forms considerably ahead of it. I'm pretty desperate. Could it be something to do with the constriction of area? I've done some thinking and have no idea.

The thing is I don't know where to go from here, since the residuals aren't bad so this does seem to be the result of the setup I have: I just have no idea why its happening

Thanks for any help,

Matt
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Old   May 1, 2020, 22:33
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Lucky
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Inlet BC? Outlet BC?

And it looks like you are using a slip wall for the top BC. Why is it not a freestream?


Just check the BC's.
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Old   May 2, 2020, 04:00
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Quote:
Originally Posted by Mattobox View Post
Making an air intake, and I've got a shock forming where I certainly don't think it should be, resulting in my simulation being... bad to say the least.

This is what my simulation looks like currently: https://imgur.com/a/AtmtGIj

I'm planning for the three ramps to give oblique shocks, normal shock in the central bit, and diffuse out to the outlet at the end. This is pretty much exactly what I'm going for: https://imgur.com/a/5te0trA

I've deduced that it is the proximity of that top part of intake to the bottom part that causes this big normal shock to occur where its not supposed to. When I moved it twice as far away, the oblique shocks formed normally. The weird part is, in the 'target' image above, based on their dimensions, their two parts were closer together than mine were?

Can anyone see a reason why this proximity would result in this? Its also pretty strange that whilst the shock is formed by the top part I'd assume since its movement affects whether it forms or not, it forms considerably ahead of it. I'm pretty desperate. Could it be something to do with the constriction of area? I've done some thinking and have no idea.

The thing is I don't know where to go from here, since the residuals aren't bad so this does seem to be the result of the setup I have: I just have no idea why its happening

Thanks for any help,

Matt

Back pressure at the exit of inlet is too high.
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Old   January 4, 2021, 07:26
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Or there is bleeding outflow involed just behind the throat
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