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Plamsa module simulation error "Division by Zero"

September 14, 2019, 10:20 pm
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I downloaded the capcitively coupled plasma simulation file from the following web: https://www.comsol.com/model/gec-ccp-reactor-55011

The only change I did was changing the geometry and mesh to suit it. But I get the following error, Could someone help me with this, please The simulation file is here: https://drive.google.com/file/d/1Odik5nPlgyy7xPLaWrcYifVTMhcFiD8F/view?usp=sharing

The error,

Division by zero. - Function: / Failed to evaluate temporary symbolic derivative variable. - Variable: comp1.ptp.Te@VDN$comp1.Ne_per - Defined as: (3(exp(comp1.Ne_per)(1/(unit_m_cf^3))))((-(2comp1.ptp.en))/((3comp1.ptp.ne)^2)) Failed to evaluate temporary symbolic derivative variable. - Variable: comp1.ptp.nue_th@VDN$comp1.Ne_per - Defined as: (0.5((((8e_const)comp1.ptp.Te)/(pime_const))^(-0.5)))(((8e_const)((3(exp(comp1.Ne_per)(1/(unit_m_cf^3))))((-(2comp1.ptp.en))/((3comp1.ptp.ne)^2))))(1/(pime_const))) Failed to evaluate temporary symbolic derivative variable. - Variable: comp1.ptp.ne_bnd@VDN$comp1.Ne_per - Defined as: ((comp1.ptp.ne(((-0.5)(1-comp1.ptp.re))((0.5((((8e_const)comp1.ptp.Te)/(pime_const))^(-0.5)))(((8e_const)((3(exp(comp1.Ne_per)(1/(unit_m_cf^3))))((-(2comp1.ptp.en))/((3comp1.ptp.ne)^2))))(1/(pime_const))))))+((((-0.5)(1-comp1.ptp.re))comp1.ptp.nue_th)(exp(comp1.Ne_per)(1/(unit_m_cf^3)))))(1/(1+comp1.ptp.re)) Failed to evaluate expression. - Expression: d(d(((2(comp1.ptp.ne_bnd+comp1.ptp.tne_bnd)test(comp1.Ne_per)pir)(ptp_xdim.atonly(dvol)))(dvol_spatial),{test@7}),comp1.Ne_per) Failed to evaluate Jacobian of expression. - Expression: d(((2(comp1.ptp.ne_bnd+comp1.ptp.tne_bnd)test(comp1.Ne_per)pir)(ptp_xdim.atonly(dvol)))(dvol_spatial),{test@7}) Failed to evaluate Jacobian of expression. - Expression: ((2(comp1.ptp.ne_bnd+comp1.ptp.tne_bnd)test(comp1.Ne_per)pir)(ptp_xdim.atonly(dvol)))*(dvol_spatial)

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Open 3D matrix from MATLAB in COMSOL

September 15, 2019, 9:49 am
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Hello!

I have 3D matrix in MATLAB (temperature field). I can save it in . mat format. Can i open this matrix in COMSOL?

URL at matrix: https://yadi.sk/d/20vvHulLFtyVCw

Best regards, Alexey

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How to calculate heat dissipation in each layer by COMSOL?

September 15, 2019, 2:43 pm
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I have a 2D stucture of a laser and I can see the temperature profile with respect to heat sink. The structure consists of multiple different layer. I need to know how much/ what percentage heat is dissipated in each layer? Thanks.

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Poisson Ratio Of Water

September 16, 2019, 11:26 am
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The below post is related to an [archived discussion](/forum/thread/135133/poissons-ratio-of-water)

Hi, I'm trying to run the Poroelasticty module (Single-Phase Darcy's Law coupled with Solid Mechanics) to run a reservoir simulation. This module has not caused me any trouble in the past, but some of my models are requiring that I enter a Young's Modulus and Poisson ratio for the pore fluid (liquid water in this case). This hasn't happened to me before and is only happening for select models. Can someone help me prevent this from happening? I've included a link to a previous discussion that addressed this, but I believe it is no longer valid, as the recently incorporated Poroelasticity module is designed to include a pore fluid.

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need a 3D modeling of heat and mass transfer comsol example

September 16, 2019, 12:36 pm
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Comsol has an example of heating chicken patties in convetion oven. inspecting the moisture and temperature distribution of the patties. Now, I am trying to make a 3D spherical chicken patties. at last, I can get a good moisture distribution, but we I cut the sphere in to a plate, there is no temperature gradient. Could some one share me a 3D heat and mass transfer Comsol example? thank you !

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magnetorheological fluid simulation

September 16, 2019, 3:31 pm
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Dear All, I currently trying to simulate the effect of magnetorheological fluid on a vibrating cantilever beam. A tip magnet is attached to the beam and the magnetic field generated is used to activate the fluid. As the the tip of the magnet impacts the fluid, the vibration of the beam is damped. Specifically, the magnetic field is used to change the yield stress of the fluid and also generate the damping force. My difficulty currently is how to simulate the magnetorheological fluid effects in COMSOL since there is no material type of the fluid in the material database. I would be highly grateful if someone could help me figure it out. I don't know if COMSOL support could also help. I have a subscription license through CMC, Canada ( I don't know if that's accepted). Thanks in advance. Hayford.

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Ptype semiconductor material

September 17, 2019, 12:24 am
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how we can run simulation without semiconductor module licence in comsole 5.4 for simulation of ptype and ntype material

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SAW Delay Line Gas Sensor

September 17, 2019, 4:06 am
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What is the reason for getting complex eigen value for SAW delay line gas sensor?What actually a complex eigen value signifies ?please let me know

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COMSOL with MATLAB

September 17, 2019, 4:23 am
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Hi, I am working with a LiveLink MATLAB. After importing the model from COMSOL to LiveLink MATLAB. This is two transient simulations results from COMSOL to MATLAB.I want to apply a condition to cool the flow channel from the higher temperature. In the inlet gas are Air (Oxygen, Nitrogen and Water Vapor) due to reaction in the channel temperature increasing with the time. After 5 seconds the temperature of the channel is about more than 353K.To restrict the channel temperature, i.e., below 353K.I want to feed only a Nitrogen gas in the gas channel. Please help me in this regards.Where I have to make a change in the code?Please find the attachment of the MATLAB program.

Thank you

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how to take variable（curvature）into comsol 5.4

September 17, 2019, 5:10 am
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I want to calculate the curvature of the raised droplets in the graph. I don't know how to introduce this parameter.（Oval represents droplet）Thank you，every bro.

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Heat Transfer with PCM (phase change material)

September 17, 2019, 7:20 am
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Hello, I have been implemented some 2D simulations of Heat Transfer in Solid with PCM. In my case I have the PCM (solid-liquid) inside a rectangular container which is subjected to a time-varying heat flux. How can I see the phase transition in a plot result? There is some kind of Probe (domain probe ?) that I have to specify in order to have in output on a temperature-time graph a trace representing the temperature trend, and therefore the phase change of my PCM? Thanks for your help.

Sebastiano

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Discretization toggle cannot be found under show?

September 17, 2019, 1:12 pm
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Can anyone tell me where to find the discretization toggle? I read it's supposed to be under "show" in the model builder and even saw a screenshot but it is just not there in my drop down menu.

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Question for Error:Size of time list 0 must equal the number of solution vectors 1

September 17, 2019, 11:58 pm
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Hi all,

I am trying to do some research about acoustic-structure coulping, now I want to change the value of Control variables fileds: grho, but there shows an Error. Java exception occurred: Exception:com.comsol.util.exceptions.FlException: The number of parameter values 0 must equal the number of solution vectors 1 Messages:The number of parameter values 0 must equal the number of solution vectors 1 How can I fix it? Attachment is my calculation file. Thanking you in advance.

Best Regards,

Jiehu

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Basic mechanics of the segregated solver

September 18, 2019, 12:52 am
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Hi all, I'm running a coupled non-isothermal flow, tim edependent and stationary. I'd like to understand how the solver proceeds, so far I understand this: Stationary: segregated solver begins (e.g. GMERS for temperature and velocity and pressure) iterations are alculated untill the error drops below threshold, solution found, END.

Time dependent: segregated solver begins, but I don't understand when the timesteps begin to be taken, as some simulations I run don't appear to reach this stage.

I'd like to understand what the steps are in as much relevant detail as possible, and how to read the progress from the log and convergence graphs, and also what effect the adaptive mesh feature has on the solution stages. when is the mesh refined? after which steps?

Thank you!

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Problem with Extremly Thin Object

September 18, 2019, 2:11 am
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Hello everyone,

I'm a beginner with COMSOL and recently got a problem with my simulation. The modell is a thin copper coil, with the section of . The material is copper and the domain physics is defined as coil/single conductor. I ran the simulation at low frequency(70-100kHz), but the solver cannot converge, no matter how I tried to change or refine the mesh. At higher frequence (from about 2MHz) it worked well.

I guess the reason of it is the skin effect, beacause the skin depth at e.g. 90kHz is 0.22mm, which is bigger than the coil section depth(70um) but smaller than its length(1mm). Is it the reason why the simulation do not converge? And if so, how could I fix it to get the simulation result in low frequence domain? Thanks for your help!

Best regards

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Anisotropic Viscosity

September 18, 2019, 3:27 am
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I might be missing something obvious but how do I specify anisotropic viscosity in laminar Flow(spf) module? Any help is appreciated.

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How to calculate the change in temperature of a point in the surface of the structure?

September 18, 2019, 8:09 am
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Dear All, I am a beginner in COMSOL thermo-optic field. I want to calculate the change in temperature in a waveguide. I created a waveguide structure having a rectangular core and cladding with heater as a heat source just above the cladding surface. After the simulation, I found some temperature gradient over the structure.

Now my question is, how can I calculate temperature and change in temperature in the core (waveguide) area?

Thank you! The version is Comsol 5.4.

With best regards Om Raj Sapkota

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Undefined material property 'E' required by Linear Elastic Material 1

September 18, 2019, 10:27 am
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This should be really easy but its driving me nuts. This is the error I get when I hit compute:

Undefined material property 'E' required by Linear Elastic Material 1 - Plot: surf1 (Surface)

I'm sure I have E set as a parameter and used in my material with the right variable and value. I've given this value multiple different names or just typed in the number and still it cannot seem to be used by comsol. Other variables are not giving me any troubles.

I've also tried to set the E at Linear Elastic Material 1 to user defined instead of material and gave the right value but to no avail.

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Comsol Beam Displacement Solution Very Off

September 18, 2019, 10:30 am
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To verify my comsol results, I evaluated a round solid aluminum beam with the following specifications and load case:

beam diameter: 28mm beam length: 300mm

Physics: The beam is extruded in the z-direction Fixed Constraint: on the bottom face (3) Boundary Load: on the top face (4) of 1000N

Running a Stationary Study, I receive the following outputs: Volume Maximum Total Displacement (mm): 0.2741

I have verified this result against Fusion 360's NASTRAN solver and the analytical solution, both of which give me the following result: Total Deflection: 4.32mm

Am I overlooking something or is COMSOL outputting very wrong values?

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Check orthogonality of fiber modes

September 18, 2019, 12:12 pm
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I simulated a few mode fiber in COMSOL and use maximum mesh size of 0.15 um to all domains to ensure accuracy of mode profile. I exported the electric field of the modes in x and y directions with grid step of 0.1 um and calculate the dot product between two mode pair to check the orthogonality (Ex1.conj(Ex2))+(Ey1.conj(Ey2)) but the resulted modes are not orthogonal enough as you can see in the attached fig1, there is a cross-coupling of around -40db below the maximum value. Is this normal or what I have to adjust to optimize the accuracy of the solution? and in general how to improve COMSOL accuracy when fiber has a large number of modes (e.g. 50 modes)?

I have also tried to use adaptive refinement but the dot product didn't improve as in fig2.

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