Does radial velocity exist in pipe flow? What is its magnitude?

mengyue1 · July 14, 2024, 12:22

Dear all,
I have been using Fluent software recently to simulate air flow in a circular pipe with a diameter of 0.0127 centimeters and a length of 1.02 meters. The air is treated as an incompressible fluid, and the inlet velocity is set to 12m/s, resulting in a flow Reynolds number of approximately 10,000.
This is a classic flow problem where, if the fluid flow direction is designated along the x-axis, the ux (velocity in the x-direction) exhibits a parabolic distribution radially.
However, I'm puzzled about the uy (velocity in the y-direction) values. I compared the ux, uy, turbulent kinetic energy (tke), and dissipation rate (eps) at the mid-section of the pipe with a reference paper (see Figures 1-4), where OSU represents the results from the literature. It can be observed that the comparison for ux, tke, and eps is excellent, showing good agreement. Nevertheless, the uy values I obtained are significantly smaller than those in the literature.
I have confirmed that the literature uses a two-equation turbulence model and enhanced wall treatment, which I have also adopted in my settings. However, there is a substantial discrepancy in uy.
May I inquire about the possible reasons for this and what parameters I should adjust to achieve results closer to those in the literature?

mengyue1 · July 14, 2024, 12:34

I am very sorry that there is something wrong with the figure. And the detailed information is that (just for uy);
The uy in my case is about 10^-6 m/s, while the corresponding value in the reference is about -0.002m/s-0.0015m/s. Would you please tell my why and how can i get the same values as the reference paper?
Thank you in advance!

July 14, 2024, 12:22	Does radial velocity exist in pipe flow? What is its magnitude?	#1
mengyue1 New Member mengyue Join Date: Sep 2009 Posts: 20 Rep Power: 17	Dear all, I have been using Fluent software recently to simulate air flow in a circular pipe with a diameter of 0.0127 centimeters and a length of 1.02 meters. The air is treated as an incompressible fluid, and the inlet velocity is set to 12m/s, resulting in a flow Reynolds number of approximately 10,000. This is a classic flow problem where, if the fluid flow direction is designated along the x-axis, the ux (velocity in the x-direction) exhibits a parabolic distribution radially. However, I'm puzzled about the uy (velocity in the y-direction) values. I compared the ux, uy, turbulent kinetic energy (tke), and dissipation rate (eps) at the mid-section of the pipe with a reference paper (see Figures 1-4), where OSU represents the results from the literature. It can be observed that the comparison for ux, tke, and eps is excellent, showing good agreement. Nevertheless, the uy values I obtained are significantly smaller than those in the literature. I have confirmed that the literature uses a two-equation turbulence model and enhanced wall treatment, which I have also adopted in my settings. However, there is a substantial discrepancy in uy. May I inquire about the possible reasons for this and what parameters I should adjust to achieve results closer to those in the literature?

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July 14, 2024, 12:34		#2
mengyue1 New Member mengyue Join Date: Sep 2009 Posts: 20 Rep Power: 17	I am very sorry that there is something wrong with the figure. And the detailed information is that (just for uy); The uy in my case is about 10^-6 m/s, while the corresponding value in the reference is about -0.002m/s-0.0015m/s. Would you please tell my why and how can i get the same values as the reference paper? Thank you in advance!