Comsol-Shear stress with velocity profile

[baranii2000]

Dear all,

I was trying to calculate the shear stress due to fluid flow inbetween two parallel plates from the velocity profile taken from the middle of the flow channel (along vertical axis 'y') using comsol. The solution i got is two times the analytical solution i have calculated. The analytical equation i have used here is
Tou=viscosity*(Umax/h)

where tou is shear stress, umax is the max velocity
h is half of the distance between plates.

The calculation with velocity profile from comsol is done by

Tou= viscosity*(du/dy)
du/dy, i calculated with excel from the u,y values in the velocity profile.

the velocity profile is parabolic and looks laminar.
is that i am doing something wrong?


Thanks

Arun

 

[Brian_C]

I think your analytical expression is wrong. For pressure driven flow, there should be a dimensionless parameter which depends on the pressure gradient. Look up Couette flow in any fluid dynamics textbook.

 

[oswaler]

Hello Arun,

Thank you for sharing your findings and question. It is important to carefully evaluate any differences between analytical and numerical solutions, as they can provide valuable insights into the accuracy and limitations of both methods.

In this case, the two times difference between your analytical solution and the solution from comsol may be due to a number of factors. One possibility is the use of different assumptions or boundary conditions in the two methods. It may also be related to the precision and convergence of the numerical solution in comsol.

I would recommend taking a closer look at the specific settings and inputs used in both methods to see if there are any discrepancies. It may also be helpful to compare your results with other published studies using comsol for similar problems.

Overall, it is important to carefully validate and compare results from different methods in order to gain a better understanding of the underlying physics and to ensure the accuracy of your calculations.

Best of luck with your research.

Sincerely,