Learning Forum

[gloria.nulchis]

Hello ANSYS community,

I am investigating the Hagen-Poiseuilles Law using ANSYS Discovery for now. I wondered how accurate Discovery would resemble the mathematical solution and created two tubes for testing: lenght (both): 100mm, radius(1) = 10mm, radius (2) = 5mm. As fluent I used water (viscosity= 0,00089 pas, density= (1000 kg/m^3). I definded the inlet with a mass flow of 1kg/s (0,001m^3/s), the outlet with a pressure of 0 Pa. In Discovery the results are as follows: Pressure loss (tube1) = 636 pa, pressure loss (tube2) = 14800Pa. When solving it mathematically with the Hagen Poiseuilles Law the results differ greatly: Pressure loss (tube1) = 23 pa, pressure loss (tube2) = 363 Pa. Has anybody any idea, why this is? I have been stuck on this for several hours now and could not find any help on the internet.

 

Any idea or help is much appreciated.

[Rob]

Check convergence, and also how you're taking the inlet pressure for the comparison. How well refined is the near wall mesh, what turbulence model did you use and how does the H-P Law account for roughness?