[Yoshiki]

Hello,

I am using OpenFOAM v2112 to calculate wall shear stress (WSS) in a straight circular pipe model and compare it with theoretical values. For the analysis, I am using the wallshearstress utility under postProcess.

When I compare the computational WSS values with the theoretical ones, the computed value is approximately 0.3 Pa, which is about 50% lower than the theoretical value of approximately 0.6 Pa. I am struggling to resolve this issue.

I have tried varying the mesh size (0.1 mm, 0.3 mm, 0.5 mm) and boundary layer settings, but the computational result remains around 0.3 Pa in all cases.

Model specifications:
Straight circular pipe:
Diameter: 0.005 m
Length: 0.05 m
Mesh:
Generated using cfMesh [cartesianMesh (hexahedral mesh)]
Mesh size: 0.3 mm
Boundary layer: 10 layers, each 0.01 mm thick
Boundary conditions:
Inlet: Average velocity of 0.21 m/s applied
Outlet: patch (pressure condition)
Walls: No-slip condition
Other settings:
Solver: simpleFoam (steady-state)
Laminar flow
Newtonian fluid with a kinematic viscosity of
𝜈=3.301×10−6m^2/s

For post-processing, I used ParaView to calculate WSS by multiplying the output of the wallshearstress utility with the fluid density.

I also tried running the same analysis with pisoFoam (unsteady simulation), but the WSS still remained around 0.3 Pa, which is lower than expected.

If anyone could provide suggestions on how to accurately calculate WSS, I would greatly appreciate it.

velocity.xlsx