![]() ![]() Therefore, it is not possible to obtain the flow field in the gas phase with the current implementation. With this approach, the liquid is modeled while the flow field in the gas domain above the free surface is not treated other than through surface tension and pressure effects. The Navier-Stokes equations are in turn formulated on a moving coordinate system where the movement is obtained from the moving mesh equations that are solved simultaneously. The solution of the moving mesh equations smoothly displaces the mesh nodes inside the bulk of the fluid. Using the Free-Surface feature, the displacement velocity of the free surface is obtained as the fluid’s velocity at the surface at any given time. Surface tension and other surface forces are directly applied as boundary conditions at the free surface. With the moving mesh approach, the free surface is modeled as a geometrical surface separating two domains. The moving mesh free surface modeling feature in the COMSOL Multiphysics® software is a completely different approach for the same problem, compared to the level set and phase field methods discussed previously. The slip length is equal to the size of the element length. ![]() In order to compare the results from the moving mesh method with the phase field and level set methods, we use Navier slip conditions for the walls. We account for gravity in the model by adding a source in the momentum equations. The moving mesh method for the free surface prescribes the displacement of the rectangular bar and keeps track of the displacement of the water surface. Geometry and definition of the example problem. Note that the moving mesh functionality is actually also used to prescribe the movement of the little rectangular bar back and forth on the surface in the level set and phase field methods, as well as the moving mesh method. The model is of a solid bar that is partially immersed in water in a small channel. To demonstrate the moving mesh functionality, we will use the same problem as we did in the previous blog post on the phase field and level set methods. In this blog post, we will demonstrate how to use the moving mesh method for modeling free surfaces and compare the results with field-based methods. Another option, moving mesh, can handle free liquid surfaces that do not undergo topology changes. Please help and let me know, thanks.In a previous blog post, we discussed using field-based methods (level set and phase field) for modeling free surfaces. Does anyone know what's wrong with my setting? How to do multiple static analysis steps use the remesh to update the mesh at each step while inherit the stress and strain in previous step as initial conditioins. This doesn't happen in the time dependent analysis when I play with the heat transfer problem. One of the point I found is that for static problem, when I disable the BC's by modifying the physical model tree, COMSOL always just report error, " - Feature: Stationary Solver 2 (sol1/s2)". Could anyone give me some advise about how to do that? I don't want a time dependent physical problems. I've found a stress free nodal update here, but what I want is to inherit stress and strain from the original configuration and keep each analysis in a static sense. The figure after manually adjust the range of value is like this,Īnother critical problem is I don't know how to do multiple static steps that inherit the stress and strain from the previous remeshed step so far. I'm wondering if it's possible to have several criterions for remesh like the maximum and minimum element size of the remesh? However, I have very limited control of the remesh configuration, only the maximum element number. I've tried axisymetric model in COMSOL using the remesh of a single static step in the adaptation and error estimate as the following. I'm trying to reconstruct a model of cytokinesis in this paper It would be great if someone could help me to figure out these observations. However, cxx+cyy is not close to zero everywhere. Why?Ĥ.) Lastly, if I use quads as my meshing elements I can define cxx at every point. Now I am able to get cxx all over the domain. Why? I am unable to explain.ģ.) If I use triangles plus second-order discretization. But inspite of this fact I am not getting cxx+cyy=0 or close to 0. ![]() Then cxx is evaluated only at the boundary layer. So, if that's true how it can solve the Laplacian term in the model.Ģ.) If I use triangular plus boundary layer. It's like it's not even calculating the derivative. Then I get double derivative say cxx equal to absolute zero everywhere which is weird. I have made the following observations which I cannot figure out.ġ.) If I use only triangular mesh without any boundary layers. It's like I am solving transport-diffusion model for a 2D domain. ![]()
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