Learning Forum

[lisa555]

Hi everyone,nI use VoF 3D model to simulate water coating on the rotating surface.nI would like to know the thickness over the coating surface. nHow can I solve the problem?nIs that define the product of liquid volume fraction and radial coordinate as custom field function a way to solve it? Can someone provide suggestion?.Thanks, nLisan

[Rob]

I tend to create an iso-surface of water volume fraction and then report the x, y or z position on the surface. Assuming the wall has a constant position you can then subtract that from the free surface to get a depth. I use CFFs for that, and Expressions will allow this if they don't already (I've lost track of what is current, in testing and in development with Expressions as functionality is being added in the test builds almost weekly). n

[Keyur Kanade]

In cartesian coordinate, we can define a CFF and then plot vof=0.5 along that CFF. Please check if you can do the same with cylindrical coordinate. nAlso in cartesian we can create two isosurfaces - one which will create a line by intersecting a plane with free surface and then second which will create a point by intersecting that line with free surface. This way you get a point to monitor. nPlease go through help manual for more details nRegards,nKeyurnHow to access Ansys Online Help DocumentnHow to show full resolution imagenGuidelines on the Student CommunitynHow to use Google to search within Ansys Student Communityn

[lisa555]

Hi Rob, nThanks for responese, I would like to know for more detail.nls that you mean to create iso-surface which volume fraction of water larger than 0.00001.nWaht did you mean Expression will allow this if they don't already?nThanks, nLisann

[lisa555]

nThanks for your suggestion.nCould you provide more information about what CFF should I define and why choose vof=0.5 to plot?nThanks,nLisan

[Rob]

VOF of 0.5 is generally a good measure of the free surface. If you pick 0.0001 there's a good chance you'll pick up random bits of liquid if your free surface isn't well resolved (ie not enough mesh or too great a time step). nExpressions in Fluent have been seeing a lot of development work. Traditionally we'd use custom field functions for this task, but the newer versions do/will support post processing with expressions: I've been working with development builds so have lost track of what's released. nRe the CFF function, you can display x, y, or z position on the iso surface. Or use a custom field function to subtract the position of the wall to give a depth as opposed to just a position. Much the same information, the latter is easier to read. n

[lisa555]

Hi Rob,nThanks for promptly response and suggestions.nnI would like to check that Cell Wall Distance in the mesh field whether one way to get the thickness over the rotating wall.nnThanks,nLisan

[Rob]

Check the definition, I'd be wary of using that metric. Think about why: which wall will the solver choose? n