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how can make normal shock in the nozzle at inlet B.C : Pressure Far field

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Old   August 18, 2015, 09:54
Question how can make normal shock in the nozzle at inlet B.C : Pressure Far field
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Hongseok Yoo
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hi, everyone. i have some questions.

first, im using B.C Pressure inlet/outlet, i can make normal shock in the nozzle.

its unsteady flow. so normal shock is keep moving forward.

but, im using B.C Pressure Far field / Pressure outlet, i cant make normal shock in the nozzle.

it's just supersonic flow in the nozzle and oblique shock is appear

i wanna make inlet flow mach number 3.0 and outlet flow mach number 0.4.
so, changing the supersonic flow to subsonic flow.
but i cant do it.

i founded some Sentence from the fluent help mannual.

Pressure outlet boundary conditions require the specification of a static (gauge) pressure at the outlet boundary. The value of the specified static pressure is used only while the flow is subsonic. Should the flow become locally supersonic, the specified pressure will no longer be used; pressure will be extrapolated from the flow in the interior.

so, i understand, pressure outlet's gauge pressure is ignored at supersonic flow.

how can make normal shock in the nozzle at inlet B.C : Pressure Far field??

Perhaps... Pressure Far field is not acceptable??

any suggestion. please help me.
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Old   March 3, 2016, 08:26
Default same problem
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Quote:
Originally Posted by SonicGhoul View Post
hi, everyone. i have some questions.

first, im using B.C Pressure inlet/outlet, i can make normal shock in the nozzle.

its unsteady flow. so normal shock is keep moving forward.

but, im using B.C Pressure Far field / Pressure outlet, i cant make normal shock in the nozzle.

it's just supersonic flow in the nozzle and oblique shock is appear

i wanna make inlet flow mach number 3.0 and outlet flow mach number 0.4.
so, changing the supersonic flow to subsonic flow.
but i cant do it.

i founded some Sentence from the fluent help mannual.

Pressure outlet boundary conditions require the specification of a static (gauge) pressure at the outlet boundary. The value of the specified static pressure is used only while the flow is subsonic. Should the flow become locally supersonic, the specified pressure will no longer be used; pressure will be extrapolated from the flow in the interior.

so, i understand, pressure outlet's gauge pressure is ignored at supersonic flow.

how can make normal shock in the nozzle at inlet B.C : Pressure Far field??

Perhaps... Pressure Far field is not acceptable??

any suggestion. please help me.
Pleaaaase
I have the same problem
have you solved yours
can you help me

can someone pleaaase help me
saeed144 is offline   Reply With Quote

Old   May 8, 2016, 05:16
Default Help please
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No one has any suggestions?
it became an annoying problem
I am trying to fix inlet and outlet mach numbers in a converging-diverging diffuser, the parameters are set by the mean of pressure inlet/outlet boundaries. the values at these boundaries are pre-calculated by the inviscid quasi 2dimensional relations and normal and oblique shock relations.
the problem is that after some iterations, mach number at the inlet decreases to subsonic and the supersonic diffuser acts like a nuzzle
so the flow enters subsonic and leaves the channel supersonic, which exactly the opposite of what i want to simulate

please, help me
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normal shock, pressure outlet, supersonic flow, terminal shock

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