Originally Posted by TianC (Post 376011)

Hi guys,

To my understanding, the wallShearStress utility calculates the wall shear stress at the latest timestep. It is a post-processing utility.

wallShearStress can be a good way to monitor if a simulation has settled down to a steady state. Ideally you don't want to be saving all your data for many timesteps until the simulation has settled (since this consumes vast amounts of data as you may have noticed!)

So my question is:

Is there any way of outputting wallShearStress at every timestep (i.e. not having to use the utility for just the last timestep every time)?

Ideally, is it possible of outputting JUST the wallShearStress at more frequent intervals than you output your other data?

Also, is it possible to do some kind of average magnitude to see how the wall shear stress behaves?

Originally Posted by Shahr (Post 519995)

You can use utilityFunctionObjects for this purpose. Google/grep it for usage guide. There you can adjust the output frequency as well.

I want to add that although judging by the magnitude of WSS might be a good way of judging about the statistical convergence of the simulation, I have found it only a necessary conditions, not sufficient. You have to compare probes' values of higher order statistics, time-averaged profiles, etc.

Originally Posted by huangxianbei (Post 515027)

Hi,Bruno
My case is a 90 bend duct with an aspect ratio of 6. Smagorinsky model is used with mean y+ <4, it's incompressible.
The inlet condition is obtain by interpolate the experimental velocity, and then mapped to the grid points.
The mesh's max aspect ratio is <700, which is OK when doing the checkMesh
Here is the comparison of the two results at inletAttachment 34454
The first 7 rows of data are obtained using sample line, the 1st is distance, and following are the wallGradU vector and wallShearStress vector, each has 3 components. The x direction is the studied direction
Xianbei

Originally Posted by killsecond (Post 520079)

Hi Shahr,

Thank you very much for your advice, I will try. In fact, I want to show the skin friction coefficient distribution around the cylinder, however the flow around the cylinder is unsteady, so I need to show the time-averaged profiles.