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Plotting volume fraction, dynamic viscosity of the dispersed phase for EE model, lam flow

July 10, 2016, 10:38 am
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Greetings
Am analyzing a sedimentation problem in a horizontal pipe using the euler-euler model, laminar flow interface. Am a new user to Comsol
I want to obtain the volume fraction of the dispersed phase in a specified direction i.e. x-direction (e.g. 0 - 3.65m), y-direction (0 - 0.0508m). [I can obtain the volume fraction of the dispersed phase for the whole simulation time though by derived values>maximum>surface maximum; but this is not enough]
I also want to obtain other plots such as, dynamic viscosity for the dispersed phase, slip velocity in x-direction but I don't know how!
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Tracing of particles on solid surface

July 10, 2016, 2:10 pm
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Hi all,

I wanted to know is possible model the fluidized particles and their interaction with the surrounding solid surface. Please suggest how to go about it.

Thank you,
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symmetry boundary in flow model, symmetry plane not in flow domain

July 11, 2016, 3:58 am
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Hi there,

I'm buidling a model of a heat exchanger which is symmetric along the flow direction (heat transfer+laminar flow). Unfortunetly I got two pipes which aren't part of the symmetry plane but have the same distance from it.

Is there a way to take the computational advantages of the symmetry nevertheless? I only found the possibility to declare the symmetry boundary for the heat transfer, where the symmetry plane is inside the relevant domain. I would need something to mirror the pipe to the other side..

Thanks,
Björn
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How to simulate Marangoni effect of mixed solvents?

July 11, 2016, 6:17 am
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Hi, I would like to simulate the Marangoni effect of a mixed solvents with different surface tensions, but I can hardly find any example about this kind of simulation. In my case, I use 2 solvents, the solvent with lower boiling point will evaporate first which will cause surface tension gradient and form Marangoni flow. The temperature gradient doesn't need to be considered. I'm wondering if there is any examples similar to me or if anyone know how to build a model in COMSOL?

Thanks
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Hii everyone

July 12, 2016, 10:29 pm
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I am working on comsol 5.0 and am facing problem on passing two fluids (air, liquid solution) through single domain.Even i have tried 2 different inlets and outlets for 2 different fluids but after selecting 1 material in domain the other automatically overidden itself and in results it is not showing mass tranfer or diffusion .
please help me guys in physics selection.
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Failed to find Consistent Initial Values

July 13, 2016, 3:00 pm
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I am solving a turbulent flow problem in Comsol; and I've been having non-convergence issues. I have used small initial values; and I have also used a ramp function with steady state value of the inlet flow parameters, but the error still persists. The mesh is not coarse, the boundary conditions were well specified. Please, I will appreciate suggestions on how I can tackle the problem.

Regards

Femi
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Thermal Wall functions

July 15, 2016, 4:04 am
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Can somebody elaborate on this from the reference manual pg (794) :

"Wall boundary conditions for turbulent fluid flow. For the k-ε turbulence model, this condition is of the type k − r( ε ), −n · ∇ε, where r is a given function. Bidirectional constraints for the first relation imply that the second relation cannot hold."

It appears in the section of symmetric and non-symmetric constraints.

Further i have the following message printed on my log screen :

“Inconsistent point-wise unidirectional constraints found.
78 constraints are merged/removed.
More inconsistent point-wise unidirectional constraints found...”

I think, since I'm solving heat transfer with turbulent flow, the constraint by nature bidirectional.


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New to COMSOL : Modeling a water droplet impingement on steel

July 15, 2016, 5:12 am
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Hi,
I want to model a water droplet impinging on Steel.I don't know where to begin.So if anyone has done anything in comsol regarding this it would be of great help to me if anyone could guide me through the process they have used in comsol
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CONSULTATION

July 15, 2016, 5:37 pm
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Hi everyone,

I'm a low designer seeking and asking for your suggestions regarding my project.
it happen that im looking for a formula and computation of how can i prove that
the steel at about 200 degrees celius wil cool at about 20 degrees celcius after being conveyed in a special enclosed conveyor, with blower and exhaust fan,, inside an airconditioned room.

Please help me guys,
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Water droplet falling through air on a structured surface

June 30, 2011, 6:14 am
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Hi,
Im new to comsol. I was trying to model a water droplet falling onto a solid substrate. The droplet should fall through air and then i should be able to calculate contact angles at various instances after the droplet has made contact with the surface . However the main problem im facing is tht the droplet just doesnt fall. What i dont realise is tht when ive defined all constants and boundary conditions, why is this happening? I havent given Volume forces during defining of subdomain variables as you will see in my model which im attaching.
Btw im using free mesh....shud i use ALE?
Any help wud be appreciated.
Thanks.

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Mixing two different fluids in fluid flow

July 12, 2012, 2:46 am
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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 do not react with each other. I have to inject them separately to two inlets at different velocities. There is only one domain for the whole device.
I used laminar flow and transport of dilute species physics but my problem is that I cannot use two distinct liquids to inject. I made two different material but one of them always overrides the other and finally either one of them is only used in the process and the density plot of the device show that the density is uniform throughout. How can this be solved in comsol ?
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Solution not computed error message

July 18, 2016, 11:03 pm
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Please, what can cause this error "Solution 1 is not computed"?.
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Zero external Pressure

July 19, 2016, 8:17 am
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Hi all,
I have a FSI project in which I simulate a fluid flow in a pipe and i want 0 external pressure. I used fixed constrained for the outside boundaries of the cylinder and the results differ significantly from the expected-article ones ONLY at mechanics such as displacements,stresses whereas flow results are correct. So i suspect fixed constrained causes the differences and its not appropriate for zero external pressure.

How can i achieve zero external pressure condition at the pipe?
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Who can help me to explain in detail each of the parameters in the Laminar flow equation of COMSOL

July 21, 2016, 12:37 am
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In the software, in the Laminar flow mould, the equation is shown below:
ρ(u∙∇)u=∇∙[-pI+μ(∇u+(∇u)^T )]+F
ρ∇∙(u)=0
who can help me to explain in detail each of the parameters in this Laminar flow equation, and does it has relationship with Navier Stokes or other equations?
Thank a lot!
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pair flow continuity in form assembly mode

July 21, 2016, 8:47 am
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Hi,
I'm trying to model blood flow and cholesterol concentration in an artery. because of high aspect ratio between the free blood flow region(lumen) and the arterial wall layers, and high velocity and concentration gradients in the porous wall, It would be more efficient to use incompatible mesh and prevent memory allocation errors.
I've tried to mesh the free and porous parts individually, but seems COMSOL doesn't implement flow continuity and uses wall boundary condition instead even when using pair flow continuity.
actually I don't know which branch of the pair flow continuity to use and how to do that.
simplified geometry is attached.
Thanks.
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Contact Angle of a sessile droplet

October 2, 2013, 7:45 pm
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Hi,
I'm a beginner in using comsol.I would like to measure the static contact angle of a water droplet. The purpose of this measurement is to determine whether a surface is hydrophobic or not. I've the image. Is it possible to measure the angle by comsol? Please help.
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droplet modelling

February 27, 2015, 1:42 am
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can anyone tell me the correct procedure for modelling a water drop on wetted surface.... i used 2 phase flow level set and phase field... but its not working.. i jst want to make dat drop on the horizontal wetted wall. plz reply....
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Convergence on a Rotating Machinery Mixture Module (multi-phase flow)

July 24, 2016, 12:01 pm
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Hello everyone,

Quick question, I'm trying to simulate fluid flow (water and air) in a reactor. It is essentially a mixer with an impeller to induce the flow of water while air is introduced via two nozzles. It has some internal baffles as well.
When I run the analysis I only get good convergence up to 0.2s then the error increases rapidly and the time steps slow down.
I've defined the slip velocity and applied boundary layers to all surfaces in the mixer, the impeller rpm is ramped but I just don't seem to get past 0.2s.
Can anyone suggest what might be the problem associated with my analysis?

Any assistance will be greatly appreciated.

Kind Regards,
David Flemming
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User define interaction force

March 9, 2016, 9:06 am
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Hello

Now I am using charged particle tracing module and ,as you know, the defult interaction among particle set by comsol is Coulomb force.

I want to change Coulomb interaction to other types of interaction, for example, the force inversely proporitonal to particle distance.

I know that I can put the desired expression in "user define force", however, I have no idea to write it down. That is, I dont know the syntax. Whenever I tried, it appeared that the syntax was wrong but I couldn't find any information regarding syntax.

I really look forwad to your helping me. Thanks.
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FSI of solid movement in fluid

July 26, 2016, 1:01 am
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Dear all,

I try to model the deformation of a rectangular beam due to the harmonic oscillation in a fluid.
I tried to implement the model by using the FSI physics.
The harmonic oscillation was defined by a predescibed displacement, but I could not solve the model.
If I define the harmonic oscillation as inlet criteria, then I get a solution and a deformation of the beam.
Can I use the FSI physics for the influence of the fluid on the solid?
Or should I use laminar flow, solid mechanics, ALE separately.
I attached the model file.
I would be very thankful for an advice.
Regards
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