Solve Flow Over Topography with FEMLAB-COMSOL Multiphysics and PDE Weak Forms

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Discussion Overview

The discussion revolves around the use of FEMLAB (COMSOL Multiphysics) to solve flow over topography using the lubrication equation, specifically focusing on the implementation of PDE weak forms and boundary conditions. Participants are seeking assistance with issues related to obtaining correct results in their simulations.

Discussion Character

  • Technical explanation
  • Homework-related
  • Debate/contested

Main Points Raised

  • One participant, Catherine, reports difficulties in obtaining correct results when implementing the lubrication equations in FEMLAB and seeks suggestions.
  • Another participant, Vanechka, asks for clarification on what is meant by "wrong results" to better understand the issue.
  • Catherine explains her expectations for the results based on the theory of gravity-driven flow of thin liquid films and describes her specific setup, including initial conditions for film thickness and pressure.
  • A different participant expresses interest in whether Catherine was able to successfully implement the lubrication equation in FEMLAB.

Areas of Agreement / Disagreement

The discussion remains unresolved, with participants sharing their experiences and seeking clarification without reaching a consensus on the issues faced by Catherine.

Contextual Notes

There are limitations regarding the specific details of the boundary conditions and the exact nature of the "wrong results" that Catherine is encountering, which may depend on the definitions and assumptions used in her model.

Catherine
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I have just started to work on FEMLAB.I am using at the moment the PDE modes-Weak forms to solve flow over topography using the lubrication equation. I have implemented the lubrication equations into the subsomain settings and set the boundary conditions but i do get wrong results. Does anyone knows FEMLAB?

Any suggestions will be really appreciated.
 
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Hi Catherine, haven't used the lubrication equations that much myself but perhaps can come up with something. What do you mean by getting the wrong results, what actually is wrong?
 
Hi Vanechka, I know the results that I should be expecting from "Gravity driven flow of continuous thin liquid films on non-porous substrated with topography" I am trying to solve the flow over a step down with the lubrication equation in FEMLAB. I have implemented the lubrication equation into the subdomain settings in terms of weak forms for the film thickness and pressure equation. the initial condition were: the film thickness is h=1 and at the outlet the first derivative dh/dx=0.Could you please advice me.
Thanks
 
Hi Catherine,

I have some experience working with thin film flows. I would like to know if you finally made FEMLAB work with the lubrication equation.
 

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