Tagged: ansysfluent, shearstress, strainrate, wallshearstress


October 22, 2020 at 6:02 pmclabrSubscriberHi everyone nI have got a fluid flowing inside a cylindrical pipe and I want to compute shear stresses in the entire fluid domain (not only at the wall). I've tried calculating them using this formula: viscosity*shear rate and I've used the shear rate computed by Fluent.nIf I consider the walls, as a result I get a value of WSS equal to the one computed by Fluent at the outlet but different at the inlet. It seems that at the inlet the values that I've calculated are halved with respect to the WSS computed by Fluent.nDoes anybody know why this happens?nThanks in advance!n

October 23, 2020 at 12:28 amKarthik RAdministratorHi, nShear stress at the wall generally gives you an indication of the overall viscous losses in the pipe. As I'm trying to understand your question, could you please elaborate on why you are estimating shear stress at the inlet and outlet boundary? Also, are you estimating this value at the edge where the inlet boundary meets the wall? nThank you.nKarthikn

October 23, 2020 at 9:52 amclabrSubscriberHi Karthik,nThank you for your help. I have blood flowing and I want to estimate shear stress inside the blood, not only at the wall. So I made a UDF to calculate them by using C_STRAIN_RATE_MAG(c,t), then what I do is check that the values that I've obtained at the wall are equal to the ones computed by Fluent, in order to do this I make a xy plot of these quantities along a line at the inlet and one at the outlet. Then I compare the values I have at the wall (when the line meets the wall) with the one I've computed. nI just use the line at the inlet and the one at the outlet to check if my calculation is ok but I'm interested in the shear stress in the all domain.nn

October 23, 2020 at 10:34 amRobAnsys EmployeeCheck a little into the domain, computed values on the boundaries can be misleading: especially on inlets where the flow is sorting itself out from the boundary condition to the developed flow field. n

October 23, 2020 at 2:28 pmclabrSubscriberI checked inside the domain and this is the result: nwhile if I make the contour, values are quite different in the first part:nnIn the xy plot of the inlet the difference is even more evident. I know that the fluid is still developing but shouldn't I get the same results since I am using the same formula that Ansys is using?nThis is the udf I used to compute the SS:nThank you in advance.n

October 23, 2020 at 2:35 pmRobAnsys EmployeeWhy would the wall shear stress give a meaningful result away from the wall? n

October 23, 2020 at 3:10 pmclabrSubscriberI want to check the shear stress profile on the bloodn

October 23, 2020 at 3:57 pmRobAnsys EmployeeWall shear stress isn't the same as bulk flow shear stress. Strain Rate and other derivatives are available via the Derivatives section of the post processing. n

 You must be logged in to reply to this topic.
Simulation World 2022
Check out more than 70 different sessions now available on demand. Get inspired as you hear from visionary companies, leading researchers and educators from around the globe on a variety of topics from lifesaving improvements in healthcare, to bold new realities of space travel. Take a leap of certainty and check out a session today here.
Earth Rescue – An Ansys Online Series
The climate crisis is here. But so is the human ingenuity to fight it. Earth Rescue reveals what visionary companies are doing today to engineer radical new ideas in the fight against climate change. Click here to watch the first episode.
Ansys Blog
Subscribe to the Ansys Blog to get great new content about the power of simulation delivered right to your email on a weekly basis. With content from Ansys experts, partners and customers you will learn about product development advances, thought leadership and trends and tips to better use Ansys tools. Sign up here.
 Suppress Fluent to open with GUI while performing in journal file
 Heat transfer coefficient
 What are the differences between CFX and Fluent?
 Floating point exception in Fluent
 The solver failed with a nonzero exit code of : 2
 Getting graph and tabular data from result in workbench mechanical
 Difference between Kepsilon and Komega Turbulence Model
 Time Step Size and Courant Number
 Mesh Interfaces in ANSYS FLUENT
 error in cfd post

2092

1744

977

762

423
© 2022 Copyright ANSYS, Inc. All rights reserved.