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Why do Boundary Probe Point Coordinates change in Results

May 3, 2019, 7:24 am
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Hello to all,

I have encountered an issue with Boundary Point Probes:

I have a code that creates Boundary Point probes (around 100) on a surface at evenly idstributed inervals on the Y direction (X and Z are constant) - I also specify the Expression and which Boundary it should belong. This works very well and if I clock on each probe I see the red dot moving on the surface boundary. I have also grouped the probes fo better handling.

The problem is that in the Definitons part of the model the coordinates are maintained (i.e. are what they suppose to be) for all probes, but in the Results part half of the probes have their X Y Z coordinates set to 0, 0, 0.

Now this is a big problem because I get NaNs for those probes.

Does anybody have an explination for this? Can it be a software bug?

Kidn regards, Ion

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Solid Domain treated as Fluid Domain [CATIA IMPORT]

May 3, 2019, 11:04 am
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The below post is related to an archived discussion

[start here]

HI, I'm having the same issue as the post above. I imported a geometry from CATIA into comsol, and the solid domain is being treated as a fluid domain by both turbulent and laminar flow regimes. I am unable to deselect it. Does anyone know how this can be fixed and why this is happening?

Cheers

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Scattering from anisotropic slab

May 3, 2019, 11:41 am
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I am trying to simulate the far-field scattering from a perfectly conducting sphere over a anisotropic dielectric block. I was initially using the impedance boundary condition but realized hte necessary approximation was not being met. How should I set up this system to accurately model the far-field scattering? I have attached my current model below.

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2D Beam Study -- Involving a moment at a point.

May 3, 2019, 4:48 pm
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I need help with representing a 1000 N*m bending moment at the end of beam.

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Wellbore

May 4, 2019, 4:07 am
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How wellbore is drilling at the same speed in comsol？I addopted the parametric sweep to research the drilling, but the results of the parametric sweep are independent of the drilling time. If you give me some advice, I would be grateful.

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CAP FACES error - "Operation not supported on virtual geometry"

May 4, 2019, 7:00 am
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I am trying use an imported STL file of blood vessels to perform some fluid dynamics simulation. To close off the ends to create the fluid domain inside the vessels, I think the best way is to use the Cap Faces feature in CAD import module.

When I try to use this feature (choosing the loop defining the perimeter of the vessel cross section) - it just gives me an error "Operation not supported on virtual geometry".

Not sure what this means - please let me know if you know a solution.

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The domains of overriden in comsol

May 4, 2019, 9:44 pm
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While I define the materials of domains, I selected the magnet domains and air domains. I look through material>>air, the air domain was covered the magnets. Is it associated with the CAD file that I imported? I tried drawing the circle(air domain) in comsol, but it still cannot work, the air domain is covered the magnet. How can I solve this problem.

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Problem:Loop variable correlation was detected

May 5, 2019, 12:39 am
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Hello!I am a beginner,and I meet a problem:Loop variable correlation was detected.So how to solve it,please................. help me the problem like this: Loop variable correlation was detected. - Variable: comp1.taue - Geometry: geom1 - Border: 6

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Externally vibrating Channel

May 5, 2019, 1:11 pm
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Hi; I am a new user of COMSOL and I need a little help. I want to create a vibrating microchannel but I couldn't figure out how to give external vibration to whole channel. Moreover, I want to examine how the vibration will effect the velocity in channel. Can anyone help me ?

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fluid flow through a membrane with many pores

May 5, 2019, 7:35 pm
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Hi, I want to simulate the fluid flow through a membrane (~ 1 um thickness) with 20 um dimatere pores. When I want to do 3D simulation and choosing the membrane area of 1*1 cm with high density of pores, the meshing and simulation take long time.

Can enyone guid me?

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Modelling a chemical reaction reactor

May 6, 2019, 12:23 am
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Does anyone know why the results are Wavy lines? I think the correct results should be Smooth curve.

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How to apply temperature continuity condition between the wall of a reactor and the Heat Transfer Fluid?

May 6, 2019, 12:34 am
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Hi ,does anyone can help me? I want to konw how to apply temperature continuity condition between the wall of a reactor and the Heat Transfer Fluid? I am currently try to simulate a reactor , heat transfer fluid flow move heat through the heat exchanger wall ,asume the temperatures of inner side (the reator side) and the outer side( HTF side) are the same. How to apply this in COMSOL? The heat transfer fluid modules I use are heat transfer in fluids and laminar flow. The reactor is heat transfer in porous media.

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The definition of material overriden in pm_motor

May 6, 2019, 2:38 am
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Dear all, I am simulating a motor. While I defined the materials of different domains. In material>>air, I found the domains of magnet are covered by the air domain. The pic I uploaded is the correct definition of materials. You can see the pic in purple color that are domains of air. But in my model, I scanned the definition of the air domains, I found the purple color was covered the magnets. How can I avoid this poblem?

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Propagation of blast waves in the air

May 2, 2019, 5:04 am
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At present, I already know the maximum overpressure and maximum shock wave generated by the explosion. With regard to the explosion overpressure (pressure field) in the air and the free propagation of the shock wave (velocity field), what model analysis is appropriate?

Looking forward to your answers! thank you very much!

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Shape factor

May 2, 2019, 7:53 am
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Hello, I need help calculating the shape factor of an orthogonal corner between two walls. I've created the geometry and applied concrete as material as well as internal&external temperatures. Do anyone know how to determine the shape factor in this situation (what's the next step)?

  • Anna
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Total reflection in a 2D double bent waveguide

May 6, 2019, 8:11 am
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Hi, I'm trying to simulate total light reflection in a SU-8 waveguide (refractive index 1.6, exterior domain: air) structured by a first straight section split into two symmetrical S-shaped bends followed by a second straight section. The rays are released from a point source with a cone angle of π/6.

First step I've modeled the straight section and one bend. I've studied the bend radius of curvature with Parametric Sweep and found the optimal value in order to have total reflection.

Second step I've added the second bend to design a S-shaped bend followed by the second straight section.I've studied the bend radius of curvature with Parametric Sweep as before.

Once I've found the two optimal radius of curvature values, I've copied it and used "Mirror" to have a structure with double thickness in the first straight section from the rest and with two symmetrical S-haped bends.

?? If I compute the final structure, rays undergo refraction since the beginning, even if the incident angle is the same. Why there's reflection anymore?

Thank you, Marta

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How to extract displacement distribution line profiles from plots of resonant frequency ?

May 6, 2019, 8:27 am
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I am using the acoustic module to simulate vibration modes of a cylindrical rod. Now I would like to draw a line parallel to the cylinder axis to indicate displacement distribution on the surface when the rod is vibrating at its resonant frequency.

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Differential (multielement) lumped ports in RF module

May 6, 2019, 9:13 am
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Hello,

I am using the differential (multielement Lumped ports) ports of the RF module to run an S-parameter analysis on a couple of differentiaol traces on a PCB.

Under Settings the reference characteristic impedance is set as Zref = 50 Ohm. Is that a differential or single-ended reference impedance?

I am doing a port and frequency sweep to save the S-parameters over frequency. Are saved S-parameters differential?

Thank You

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Fix the 4 corners of a beam to use shape optimization

May 6, 2019, 9:27 am
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Hello,

I need to fix the 4 cornes of a beam and optimize just de top and bottom edges. Can someone help me?!!

Thankss!

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Division by zero error

May 6, 2019, 10:14 am
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Hello. I try to model He-Ne plasma. And during the calculation I received the following error:

Division by zero. - Function: / Failed to evaluate temporary symbolic derivative variable. - Variable: comp1.plas.R_wNe_1p@VDN${real@7} - Defined as: (((comp1.plas.c_wecomp1.plas.kf_4)((1/comp1.plas.M_wNe)((comp1.plas.wNe((1/(R_constcomp1.plas.pes1.minput_temperature))(comp1.plas.pes1.minput_pressure(((-1)/(((((((comp1.plas.wNe/comp1.plas.M_wNe)+(comp1.plas.wNes/comp1.plas.M_wNes))+(comp1.plas.wNe_1p/comp1.plas.M_wNe_1p))+(comp1.plas.wHe/comp1.plas.M_wHe))+(comp1.plas.wHes/comp1.plas.M_wHes))+(comp1.plas.wHe_1p/comp1.plas.M_wHe_1p))^2))(((1/comp1.plas.M_wNe)(-exp(real(comp1.WHe_1p))))+((1/comp1.plas.M_wHe_1p)exp(real(comp1.WHe_1p))))))))+(comp1.plas.rho(-exp(real(comp1.WHe_1p)))))))+(((comp1.plas.c_wNecomp1.plas.kf_14)((1/comp1.plas.M_wHe_1p)((comp1.plas.rhoexp(real(comp1.WHe_1p)))+(comp1.plas.wHe_1p((1/(R_constcomp1.plas.pes1.minput_temperature))(comp1.plas.pes1.minput_pressure(((-1)/(((((((comp1.plas.wNe/comp1.plas.M_wNe)+(comp1.plas.wNes/comp1.plas.M_wNes))+(comp1.plas.wNe_1p/comp1.plas.M_wNe_1p))+(comp1.plas.wHe/comp1.plas.M_wHe))+(comp1.plas.wHes/comp1.plas.M_wHes))+(comp1.plas.wHe_1p/comp1.plas.M_wHe_1p))^2))(((1/comp1.plas.M_wNe)(-exp(real(comp1.WHe_1p))))+((1/comp1.plas.M_wHe_1p)exp(real(comp1.WHe_1p)))))))))))+(comp1.plas.c_wHe_1p(comp1.plas.kf_14((1/comp1.plas.M_wNe)((comp1.plas.wNe((1/(R_constcomp1.plas.pes1.minput_temperature))(comp1.plas.pes1.minput_pressure(((-1)/(((((((comp1.plas.wNe/comp1.plas.M_wNe)+(comp1.plas.wNes/comp1.plas.M_wNes))+(comp1.plas.wNe_1p/comp1.plas.M_wNe_1p))+(comp1.plas.wHe/comp1.plas.M_wHe))+(comp1.plas.wHes/comp1.plas.M_wHes))+(comp1.plas.wHe_1p/comp1.plas.M_wHe_1p))^2))(((1/comp1.plas.M_wNe)(-exp(real(comp1.WHe_1p))))+((1/comp1.plas.M_wHe_1p)exp(real(comp1.WHe_1p))))))))+(comp1.plas.rho(-exp(real(comp1.WHe_1p))))))))))+(exp((-comp1.plas.iota)log(comp1.plas.n_wNe_1p))((-comp1.plas.iota)((1/comp1.plas.n_wNe_1p)((1/comp1.plas.M_wNe_1p)((comp1.plas.wNe_1pN_A_const)((1/(R_constcomp1.plas.pes1.minput_temperature))(comp1.plas.pes1.minput_pressure(((-1)/(((((((comp1.plas.wNe/comp1.plas.M_wNe)+(comp1.plas.wNes/comp1.plas.M_wNes))+(comp1.plas.wNe_1p/comp1.plas.M_wNe_1p))+(comp1.plas.wHe/comp1.plas.M_wHe))+(comp1.plas.wHes/comp1.plas.M_wHes))+(comp1.plas.wHe_1p/comp1.plas.M_wHe_1p))^2))(((1/comp1.plas.M_wNe)(-exp(real(comp1.WHe_1p))))+((1/comp1.plas.M_wHe_1p)exp(real(comp1.WHe_1p)))))))))))) Failed to evaluate expression. - Expression: dvol_spatial(r(pi((-2)((d(comp1.WNe_1p,t)(comp1.plas.wNe_1p((1/(R_constcomp1.plas.pes1.minput_temperature))(comp1.plas.pes1.minput_pressure(((-1)/(((((((comp1.plas.wNe/comp1.plas.M_wNe)+(comp1.plas.wNes/comp1.plas.M_wNes))+(comp1.plas.wNe_1p/comp1.plas.M_wNe_1p))+(comp1.plas.wHe/comp1.plas.M_wHe))+(comp1.plas.wHes/comp1.plas.M_wHes))+(comp1.plas.wHe_1p/comp1.plas.M_wHe_1p))^2))(((1/comp1.plas.M_wNe)(-exp(real(comp1.WHe_1p))))+((1/comp1.plas.M_wHe_1p)exp(real(comp1.WHe_1p)))))))))-(comp1.plas.M_wNe_1p((((comp1.plas.c_wecomp1.plas.kf_4)((1/comp1.plas.M_wNe)((comp1.plas.wNe((1/(R_constcomp1.plas.pes1.minput_temperature))(comp1.plas.pes1.minput_pressure(((-1)/(((((((comp1.plas.wNe/comp1.plas.M_wNe)+(comp1.plas.wNes/comp1.plas.M_wNes))+(comp1.plas.wNe_1p/comp1.plas.M_wNe_1p))+(comp1.plas.wHe/comp1.plas.M_wHe))+(comp1.plas.wHes/comp1.plas.M_wHes))+(comp1.plas.wHe_1p/comp1.plas.M_wHe_1p))^2))(((1/comp1.plas.M_wNe)(-exp(real(comp1.WHe_1p))))+((1/comp1.plas.M_wHe_1p)exp(real(comp1.WHe_1p))))))))+(comp1.plas.rho(-exp(real(comp1.WHe_1p)))))))+(((comp1.plas.c_wNecomp1.plas.kf_14)((1/comp1.plas.M_wHe_1p)((comp1.plas.rhoexp(real(comp1.WHe_1p)))+(comp1.plas.wHe_1p((1/(R_constcomp1.plas.pes1.minput_temperature))(comp1.plas.pes1.minput_pressure(((-1)/(((((((comp1.plas.wNe/comp1.plas.M_wNe)+(comp1.plas.wNes/comp1.plas.M_wNes))+(comp1.plas.wNe_1p/comp1.plas.M_wNe_1p))+(comp1.plas.wHe/comp1.plas.M_wHe))+(comp1.plas.wHes/comp1.plas.M_wHes))+(comp1.plas.wHe_1p/comp1.plas.M_wHe_1p))^2))(((1/comp1.plas.M_wNe)(-exp(real(comp1.WHe_1p))))+((1/comp1.plas.M_wHe_1p)exp(real(comp1.WHe_1p)))))))))))+(comp1.plas.c_wHe_1p(comp1.plas.kf_14((1/comp1.plas.M_wNe)((comp1.plas.wNe((1/(R_constcomp1.plas.pes1.minput_temperature))(comp1.plas.pes1.minput_pressure(((-1)/(((((((comp1.plas.wNe/comp1.plas.M_wNe)+(comp1.plas.wNes/comp1.plas.M_wNes))+(comp1.plas.wNe_1p/comp1.plas.M_wNe_1p))+(comp1.plas.wHe/comp1.plas.M_wHe))+(comp1.plas.wHes/comp1.plas.M_wHes))+(comp1.plas.wHe_1p/comp1.plas.M_wHe_1p))^2))(((1/comp1.plas.M_wNe)(-exp(real(comp1.WHe_1p))))+((1/comp1.plas.M_wHe_1p)exp(real(comp1.WHe_1p))))))))+(comp1.plas.rho(-exp(real(comp1.WHe_1p))))))))))+(exp((-comp1.plas.iota)log(comp1.plas.n_wNe_1p))((-comp1.plas.iota)((1/comp1.plas.n_wNe_1p)((1/comp1.plas.M_wNe_1p)((comp1.plas.wNe_1pN_A_const)((1/(R_constcomp1.plas.pes1.minput_temperature))(comp1.plas.pes1.minput_pressure(((-1)/(((((((comp1.plas.wNe/comp1.plas.M_wNe)+(comp1.plas.wNes/comp1.plas.M_wNes))+(comp1.plas.wNe_1p/comp1.plas.M_wNe_1p))+(comp1.plas.wHe/comp1.plas.M_wHe))+(comp1.plas.wHes/comp1.plas.M_wHes))+(comp1.plas.wHe_1p/comp1.plas.M_wHe_1p))^2))(((1/comp1.plas.M_wNe)(-exp(real(comp1.WHe_1p))))+((1/comp1.plas.M_wHe_1p)exp(real(comp1.WHe_1p)))))))))))))))))) Failed to evaluate Jacobian of expression. - Expression: dvol_spatial(r(pi((-2)(((comp1.plas.rhocomp1.plas.wNe_1p)d(comp1.WNe_1p,t))-(comp1.plas.M_wNe_1pcomp1.plas.R_wNe_1p))))) Failed to evaluate Jacobian of expression. - Expression: (-2(comp1.plas.rhocomp1.plas.wNe_1pd(comp1.WNe_1p,t)test(comp1.WNe_1p)-comp1.plas.jr_wNe_1ptest(d(comp1.WNe_1p,r))-comp1.plas.jz_wNe_1ptest(d(comp1.WNe_1p,z))-comp1.plas.R_wNe_1pcomp1.plas.M_wNe_1ptest(comp1.WNe_1p))pir)*(dvol_spatial)

I tried to solve it, but i don't understand, which Ne+ parameter is equal zero. Can you help me? How can understand this expression: comp1.plas.R_wNe_1p@VDN${real@7} I understand, that comp1 - component 1, plas - plasma module. But what is R_wNe_1p@VDN${real@7}?

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