Predicting boundary layer thickness in swirling pipe flow

velkon · April 11, 2022, 09:17

Dear all,
I am struggling with estimating the boundary layer thickness in a pipe of a turbulent swirling flow.

Does anybody know a relationship for describing the boundary layer thickness in a pipe flow for turbulent flows?

aero_head · April 11, 2022, 14:44

Are you interested in the boundary layer development in the duct entrance region or the fully developed region inside the pipe?

In turbulent flow there is no boundary layer; near the walls there is a laminar sub-layer. The pipe roughness will impact the thickness of this layer.

You can use the 1/7th power law, the log law, or the turbulent boundary layer thickness formula. The last one assumes 1) the flow is turbulent right from the start of the boundary layer and 2) the turbulent boundary layer behaves in a geometrically similar manner (i.e. the velocity profiles are geometrically similar along with the flow in the x-direction, differing only by scaling parameters Neither one of these assumptions is true for the general turbulent boundary layer case so care must be exercised in applying this formula.

April 11, 2022, 09:17	Predicting boundary layer thickness in swirling pipe flow	#1
velkon New Member velkon123 Join Date: Jan 2020 Posts: 14 Rep Power: 6	Dear all, I am struggling with estimating the boundary layer thickness in a pipe of a turbulent swirling flow. Does anybody know a relationship for describing the boundary layer thickness in a pipe flow for turbulent flows?

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April 11, 2022, 14:44		#2
aero_head Senior Member Kira Join Date: Nov 2020 Location: Canada Posts: 435 Rep Power: 8	Are you interested in the boundary layer development in the duct entrance region or the fully developed region inside the pipe? In turbulent flow there is no boundary layer; near the walls there is a laminar sub-layer. The pipe roughness will impact the thickness of this layer. You can use the 1/7th power law, the log law, or the turbulent boundary layer thickness formula. The last one assumes 1) the flow is turbulent right from the start of the boundary layer and 2) the turbulent boundary layer behaves in a geometrically similar manner (i.e. the velocity profiles are geometrically similar along with the flow in the x-direction, differing only by scaling parameters Neither one of these assumptions is true for the general turbulent boundary layer case so care must be exercised in applying this formula.