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Master1022
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- How does a boundary layer grow in a convergent duct in subsonic flow? How does this compare to the growth of a boundary layer in a divergent duct in subsonic flow?
Hi,
I was recently reading about convergent-divergent nozzles and was wondering about how boundary layers grow in them.
Question: How does a boundary layer grow in a convergent duct in subsonic flow? How does this compare to the growth of a boundary layer in a divergent duct in subsonic flow?
Given that we are in subsonic flow, ## M < 1 ## and therefore we know from the area-velocity relations that subsonic flow increases speed in the convergent section and decreases speed in the divergent section. I am not really sure what the next steps would be...
Do I need to make arguments about the pressure gradients in the two sections? For example, in the diverging section, there is a positive (unfavorable). This then decreases the free-stream velocity, increases the boundary layer thickness, and decreases the wall shear stress (source: here). Then we could make the opposite argument for the convergent section where there is an adverse pressure gradient which would decrease the boundary layer thickness.
Is this correct?
Any guidance would be greatly appreciated.
I was recently reading about convergent-divergent nozzles and was wondering about how boundary layers grow in them.
Question: How does a boundary layer grow in a convergent duct in subsonic flow? How does this compare to the growth of a boundary layer in a divergent duct in subsonic flow?
Given that we are in subsonic flow, ## M < 1 ## and therefore we know from the area-velocity relations that subsonic flow increases speed in the convergent section and decreases speed in the divergent section. I am not really sure what the next steps would be...
Do I need to make arguments about the pressure gradients in the two sections? For example, in the diverging section, there is a positive (unfavorable). This then decreases the free-stream velocity, increases the boundary layer thickness, and decreases the wall shear stress (source: here). Then we could make the opposite argument for the convergent section where there is an adverse pressure gradient which would decrease the boundary layer thickness.
Is this correct?
Any guidance would be greatly appreciated.
