How to solve the problem of negative concentration
I am a totally new user on comsol. Now I try to simulate the mixing in the microchannel without reactions. I use the laminar flow and Transport of dilluted species. There is a similar example from...
View ArticleERROR: Complex number encountered in real expression(when calculate the DEP...
Hello everyone: I use Particle tracing module for fluid to calculate the DEP force exerted on the nano-sized particles. When calculate the DEP I encountered a problem as follows: Complex number...
View ArticleSimple Question for Flow Rate
Hello, I already done a few simulations with "laminar flow" using time dependent with rectangular input. Input was "pressure, no viscous stress". Is there any ways of getting the flow rate from...
View ArticleNavier-Stokes Simulation using Coefficient Form PDE
Hi: I need to simulate fluid flow in a triangular duct, but I need to run it on a high reynold number. The problem is that when I run the model using the default "Laminar Flow" physics tab, I need a...
View ArticlePiezoelectric transducer for liquids
Hi all, I am using COMSOL to model a piezoelectric transducer directly coupled with liquid (oil or water) and using the tutorial provided in COMSOL website in this aspect. I am just defining one...
View ArticleMHD
I am working with magnetohydrodynamics. I have to simulate a conductive fluid which is stationary at first. There are 4 magnets under the fluid. AC Electric current of 0.1Hz frequency is passed through...
View Articlerigid particle carried by a channel flow
Hi I have to simulate the displacement and rotation of a rigid prticule in a fluid flow and I am not a professional on comsol. So, is there anyone who could help me? or if you have any examples of this...
View ArticleUnable to evaluate an expression
Excuse me, I am getting an error as Attempt to evaluate real square root of negative number. Function: sqrt Failed to evaluate expression. Expression:...
View ArticleSimple heat exchanger model error
Hi everyone, I'm working on a heat transfer problem and could use some help. It concerns a large horizontal pipe containing an elongated u-shaped pipe (the 'loop'). The pipe contains air and the loop...
View ArticleCouple two transient studies: Using transient flow field in transport simulation
Dear Comsol users, it would be very kind if someone could help me (I spent several hours trying to find a solution). I want to use the results of study 1 (time-dependent flow field) in study 2...
View Articlecircular variable dependency detected
Hi, The author of one paper has defined the conductivity as a function of current density and current density as a function of conductivity. In comsol, it gives a circular dependency error. How to get...
View Articlefreeze-drying; convective heat transfer with Sublimation/Resublimation
Hi guys, I’m writing my bachelor thesis and want to do a simulation of freeze-drying of coffee with comsol 4.4, but I have not much experience with it. I made some tutorials and simulated examples...
View ArticleTurbulent pipe flow
Hello, Can i simulate the pipe flow with inlet and outlet pressure boundary condition ? I want pressure drop of 0.05-0.02 bar. I have used pref as 0 Pa. I am simulating a pipe with dimension 6 mm...
View Articleshear stress in microchannel
Hello, I am clueless as to how to start the post-process data analysis to get the spatial distribution of shear stress of a micro channel. I have read the few discussion threads but it involves...
View ArticleSpecifying a rotating boundary condition
I would like to simulate a rotating wall condition. For simplicity, imagine a square box. On the top surface of that box there is a circle. Inside of the box is a viscous fluid. I would like to impose...
View ArticleProblem: Oil Droplets Seem To Dissolve In Water (Two-Phase Flow, Level Set)
I have a problem with my "Two-Phase Flow, Level Set" simulation in COMSOL 4.2. I am trying to simulate the formation of oil droplets in water by hydrodynamic flow focusing. The water and oil are...
View ArticleMixing two different fluids in fluid flow
Hi I have been working on a flow analyzer that has two inlet and an outlet. I have two fluids, one is very dense and the other is a very dilute substance, both of them are completely different and they...
View ArticleHello~~ I encounter some problems when modeling corona wind
Hello~ I was modeling ionic wind, and I had some problems on it. I selected AC/DC, and PDE module for simulation. My model is a rectangle 2D domain which represents inner section of pipe. There are two...
View ArticleAbout the stokes drag on a sphere (mph attached)
Dear All, I am trying to find the drag coefficient of a sphere in a stokes flow. Since this 3D problem can be simplified into a 2D problem, I use the creeping flow module in 2D to simulate this case....
View ArticlePeriodic flow condition
Hi, I am confused about how to use the periodic flow condition. I have a long and repeated geometry, and I want to model just one section of it (since it is repeated anyway). Geometry is very simple...
View Article