Shallow channel Approximation
Hello, I'm using COMSO 4.4 (Classkit version) and under laminar flow "use shallow channel approximation" option is missing. Actually it should be under Laminar flow------>turbulent model...
View ArticleDiscontinuity issue
Hi Ivar, As I know you are very active in helping the COMSOL users to solve their problems, your help is kindly appreciated if you could help me fix the discontinuity issue presented as follows (I know...
View ArticleFluid-Piezoelectric coupling problem (microchannel of an inkjet printhead)
I was tasked with creating a model of 1 microchannel of a piezoelectric printhead. I've modelled it but the solution doesn't converge (max no. of iterations reached). The physics I've used are...
View ArticleAutomated remeshing fails
I'm runing a axi-symmetric model and solving laminar flow with moving mesh. In the process, a few inverted mesh elements are created. To avoid this problem, I tried to use autometed remeshimg when the...
View ArticleAccsess value of variable solved for one domain from another domain
Hello, could you please help me: I'm solving a 2-D desorption of hydrogen in a metal-hydride. I created a cross-section view of metal tube 75% full of metal-hydride and have specified a hydrogen mass...
View ArticleNegative concentration values in Transport of Diluted Species Study
Hello all, I am analyzing a fluid flow and concentration gradient in microfluidic device. Device has a main horizontal channel and 256 vertical side channels to on both sides (up and down). I have two...
View ArticleTracer particles not following the mainstream floe
Hi I am modeling CO2 as a tracer gas particles in air. I have been trying to simulate CO2 by Particle Tracing module, after I found the diameter size and density of CO2 particles. I have noticed that...
View ArticleDeformation of liquid droplet
I am new to COMSOL, so I am referencing a work on deformation of liquid droplet impacting a solid surface. I tried to recreate the same model as that work. But I ran into several problems. As I tracked...
View ArticleBoundary Condition: Open Boundary
Hello, I have a confusion with a Boundary Condition (BC), the "open boundary" under Laminar Flow module. If I give "No Viscous Stress" BC, the solver fails to find a solution whereas setting value of...
View Articlefluid flux with dilute species model
Hey all, I'm sure this has been beaten to death, but I cannot seem to make a simple fluid flux across an arbitrary boundary work. My model consists of a container with a fixed amount of solute, and a...
View ArticleModel design from 2D axysimetric
Hello, how are you doing? I´m facing a problem and would like to ask you if you have some hints about how to solve it. Recently i did a Comsol tutorial for a pipe flow simulation. In this tutorial it...
View ArticleCOMSOL handling of variables in different scales
A general question: We're using COMSOL to solve a system of PDE's and comparing them to our in-house code. The variables in said PDE's are inherently in different scales (i.e. three variables are O(1)...
View ArticleHow to apply Neumann and Dirichlet's BC
Hello, I am trying to simulate flow across a cylinder in General PDE form. The governing equations are Euler's equation for Mach No. = 1. I have converted these equations in the COMSOL form to be...
View ArticleWhich Volume Force is correct?
Hi all, So far I have seen two different definitions for Volume Force for free air flow. First one is g_const*(rho_ref-nitf.rho) and second is g_const*(comp1.mat1.def.rho(p_atm,T0)-nitf.rho). where,...
View ArticleCalculation of the Bubble Size in gas liquid flow
Hi I am Simulating an air-water turbulent flow using COMSOL multiphysics 4.4. i am using two fluid turbulent flow, level set method for this purpose. I want to know how COMSOL calculates the bubble...
View Article2D Rotating electrical machine, calculating torque
Hello all I'm studying a machine with permanent magnets in the stator and a solid iron rotor(no coils). i already have the magnetic field, is there a way to extract the torque felt by the rotor? Best...
View ArticleFunction: log Failed to evaluate variable
Hi,Sergei I am getting the following error: Log of negative Function: log Failed to evaluate variable Variable: mod1.St, Defined as:...
View Articlehow to model two particles of different sizes
Hi, Am new to the Particle Tracing Module, so I have a few basic questions I need to represent two particles of sizes 5 micron and 10 micron and study their velocity profile Next, I have designed...
View Article"Internal error in boundary respecting." and "Out of memory during assembly."
Dear All I have two errors in my microfluidic models about "Internal error in boundary respecting." and "Out of memory during assembly.". At first I tried to simulate the flow of the overall 3D...
View Article(Two phase)Bubble shrink in a two phase flow
I want to simulate a bubble dynamics in the water. I initialize a bubble in the water, and use phase-field model. I give the water a velocity in a channel, the bubble moves with the water. After a few...
View Article