COMSOL provides "acpr.efc1.Lp_pext" for exterior-field (far-field) polar pattern plotting. How can I generate a near/close field SPL polar plot?
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Acoustic Radiation Pattern for near/close-field
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Multiphase fluid output with capacitor
Hi Everyone,
I hope everyone are doing good, I was trying to integrate the droplet generator and a simple capacitor together. But when I run (6 secs) for both of them coupled together only in solution droplet generator is working but not the capacitor. When I check results for the capacitance charge in all 6 sec time period it is same. Whereas it shouldn't be same as the dielectric material keeps on changing.
My main idea is to have a varying dielectric material ( in the droplet generator the output is always changing between water droplet and oil phase) in between the capacitor. But the comsol model is not taking this.
Does anyone know how to integrate the constantly varying multiphase liquid in place of dielectric material inbetween the capacitor electrodes?
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with operator
Hi,
I am using comsol 5.4 and I am trying to simulate the pulse plating electrodeposition. I need to draw the coating thickness on a cut line. I used the "with" operator as below to draw the thickness.
(with(1,-siec.iloc_er1)*5.8[s]+with(2,-siec.iloc_er1)*1.2[s])/7.0[s]/rate_factor*plating_time
unfortunately, it did not work.
I also tried the other way. So I made two different studies and join them in results and then in 1D plot group I usewd the below expresion to draw them
((data1(-cd.iloc_er1)*0.005+data2(-cd.iloc_er1)*0.005)/0.01)/rate_factor*plating_time
which send an error of unknwon function or operator.
Could you please guide me?
Best regards,
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Supersonic flow not converging
Hello Comsol users I'm trying to simulate a geometry in which is involved High Mah Number flow module. I have trying this literally from more than a month and probably I've tried everything in my meagre knowledge. I have tried laminar, spalart-allamaras, and k-epsilon. I have also tried all examples of the Comsol model library and even there if I add my model and try to run it it doesnt run at all. Please help me. I'm attaching the model here if anyone can please check what the problem is.
Update: Once I just randomly tried laminar and it gave the expected results, and now when I have again setted it up it doesn't run. I tried with the previous one as well. Please see if anyone can help.
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Integration in a custom coordinate system.
I have a pipe geometry aligned with the z axis shifted in x and y. I want to calculate the men fluid temperature through the pipe. I use the integration operator with the spatial at expression (through a variable). The syntaxis i try is like: integrate(integrate(comp1.at3(sys2.r,sys2.phi,sys2.a,Tw),sys2.r,0,ra),sys2.phi,-pi,pi). The frame of the sys2 cylindrical coordinate system is spatial. The axis directions are checked and are correct. I can integrate if the pipe is made as an axisymmetric study but is the study is a 3D component, the integral fails. If i build a square geometry and evaluate it in the same way - using the integral syntax, i get the right result (using the default coordinate system).
It must be something of the coordinate system interpretation.
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Apply outward radial pressure of same magnitude on a inner 2D ring
I would like to investigate the relation between the pressure and the diameter of a 2D ring configuration. As shown in this picture, I would like to apply the radial pressure with the same magnitude to the inner surface of the 2D ring structure, but there seems to be only loading in x or y direction that can be applied to the structure. My question is that how to apply the radial pressure to the inner surface of a 2D ring structure?
I will very appreciate anyone could help that! Best wishes Ricky
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quality factor of optical resonator in eigenfrequency study
Hi all,
I am working on an eigenfrequency study on a 3D optical disk resontor. My resonator is a 3-layer structure with refractive index of 3.4/3.5/3.4 from top to bottom. What I found is that when I change the surrounding environment refractive index from 1 to 1.1, the quality factor for the same mode drops a lot, like from 23000 to 6800. I was surprised at the result and suspect this is caused by some numerical defects.
I searched eigenfrequecy around 286** THz. I set the mesh size in all of the region smaller than freespace wavelength/((refractive index)5) and I think the mesh is OK. I tried both scattering boundary condition and PML, and they gave me similar results. Could any one comment on this problem or give me some advice on how to get reliable quality factor?
I will really appreciate your help. Thanks!
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Problems using mphinterp for extracting Solid.Tn data.
Hi.I'm modeling a contact problem between two surfaces in a 2d problem as shown in the attached figure. I cannot get the data because i got this error: "Wrong dimension of points searched for in postinterp." i use mph inter as shown below:
mphinterp(model,'solid.Tn','coord',nuevoxy,'edim','boundary','selection',4)
where nuevoxy is an array with the coordinates x and y of the points in the boundary where i wanna get this data.!
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Stress criterion for brittle material
Hello everyone
I am going to simulate the thermal expansion of a mirror. Could you tell me what is the suggested criterion to evaluate the stress in the mirror?
As far as I know, von Mises is widely used for ductile materials.
Best regards.
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WEDM Simulation
I am working on metal removal process simulation. Can anyone help?
Specifically speaking, Wire electro discharge machining, creation of plasma channel in dielectric fluid between two electrodes and removing material from positive electrode through generated spark.
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Apply outward radial pressure of same magnitude on a inner 2D ring (new)
Hi I just would like to ask you a question in Comsol simulation, as I tried many times, but still get the same problem over this weekend. The objective was to obtain the relation between the pressure and the diameter of a 2D ring structure.
Firstly, I create the 2D ring as attached. There are two circles (inner and outer) and each circle is made up of four curves which can be generated by selecting 'circle' under geometry.
Then, I select 'pressure' under the boundary load and apply the pressure of the same magnitude of 5Pa to each inner curve. Then, I always get the same simulation issues as attached.
Then, I attempted to address the problem. Initially, I was thinking there could be an error in the direction of pressure and hence I tried to apply a fixed boundary condition to one edge of curve and apply 5 Pa to another edge as attached. Then, from the simulation result as attached, I realized the positive pressure direction is directing radially outward, so there is no problem in the direction of pressure that I have chosen previously. However, I also realized that the reason that the simulation issue occurred is there was no fixing boundary condition as I discussed with you last meeting.
I will very appreciate if you can give me the correct solution for that
Thanks for your time Best wishes Junwei
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Pipe erosion caused by pollutant particles
According to the teaching case , I can not click on properties in the physics toolbar and select washout，because the properties button in the toolbar is gray. What should I do ?
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the problem about moving mesh method and free surface problem
Hi.I tried to simulate a thinnest bar(or a line) rotated in a rectangular box and .The left,right,and bottom of box are no slip condition.But the top of box are free surface.I want to observe the situation about free surface. I want slove it by using moving mesh methods.Also,I want the bar rotate by the circle center on (0,0) point and it is also the endpoint of the bar.There are lots of ways Iike "rotate boundary" or'otating domain",and I tried for long time but I can't understand how it work .! (the modle is like the the problem but the bar is rotating not move horizontallyhttps://www.comsol.com/blogs/modeling-free-surfaces-in-comsol-multiphysics-with-moving-mesh/)
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Cell periodicity
Hi, I am using the Cell periodicity model in Solid mechanics module, and selected Average strain periodicity. I noticed that I need to provide the expression of strain in each direction, but I only want to prescirbe strain in x direction. I wonder how to operate this? And also if a current field is coupled, do I need to plug a Cell periodicity in ec module as well? Thank you in advance.:) Yongyi.
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A problem with Comsol’s Axial Magnetic Bearing example
Hello all, I have downloaded the example “Axial Magnetic Bearing Using Permanent Magnets” (Application ID: 14367) to learn how to calculate the force between two permanent magnets. Without making any changes (except removing the parametric sweep and setting dz=0), I tried to verify that the force acting upon each magnet is the of same value and opposite direction. The modeling instructions do not specify a certain mesh resolution. Since electromagnetic force calculations require high resolution, it was no wonder that force equality was not obtained for the default element size.
I started to increase the mesh density, and allegedly reached force equality for the predefined “Extremely Fine” element-size, but with a maximal element size of 0.16mm (which is 10 times smaller than its nominal value). When increasing the resolution even further to 0.05mm, the equality held, but the value dropped by two orders of magnitude(!). I Increased the resolution to 0.01mm and left the simulation to run during night, but by morning it progressed only by ~5%.
I must emphasize that I this is a 2D simulation, so it’s hard to imagine what kind of computational resources are required to calculate forces for my 3D simulations. So am I missing something or is there a problem with this example? Should this relatively simple 2D simulation be so computationally expensive or is there still hope for 3D cases?
Thank you for your attention and best regards, Nadav Goulinski
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unit normal vector
Dear everyone
I'm confused about how to write the unit normal vector of a PDE in comsol? I have upload the picture of this form. Thanks in advance!
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Theory behind the evaluation of normal vectors in COMSOL Multiphysics
Hi COMSOL users,
I am studying the effect of semi-elliptical surface cracks on the fatigue life of pipeline welds using the COMSOL single-edge crack tutorial (in version 5.3a or older) based on the J-integral as a benchmark.
I was wondering if anyone knows the theory behind the definition of the unit normal vectors applied in this tutorial. My model is defined by a crack depth and length, a and c, respectively. In my model (please see attached images) it is relatively straightforward to define the unit normal vectors on the edges bounding the crack depth 'a' as -1 or 1 depending on the direction. However, it gets complicated when I move to the weld region and try to define the unit normal vectors on the edges bounding the crack length 'c'. I have tried to define them by using an estimated angle of 30 degrees but this angle is inconsistent as I increase the size of the crack particularly 'c' along the weld region.
Does anyone know the theory behind the definition of these normal vectors as used in COMSOL or have a sophisticated way of defining them. I would really appreciate any suggestions.
Kind regards, Ayo
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Moving an electrode surface as time flow (electroanalysis module)
Dear Everyone
I use electroanalysis physics for electrochemistry study. I want to move an electrode surface as time flow but geometry can use only parameter, not time function.
Does anyone know study or methode to solve this problem? I would really appreciate all suggestions of this problem.
Thank you.
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Contacts during Thermal expansion of trapped rubber
Hi,
I'm trying to model the thermal pressure exerted by a silicone block trapped into a mold after heating but the model do not converge.
I'm working in 2D axial symetry and stationnary, the mold is considered fixed.
I think it's linked with the way I set tup the contact, I tried different configurations : multi contacts (line by line) vs one single enveloppe contact (such as in the picture enclosed), lagrangian vs penalty, friction or not.
Anny suggestions would be appreciated.
Thanks
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Conductive heat transfer in a via/cylinder
Hello,
I am trying to learn COMSOL modelling and simulation. As my final objective is to simulate PCBs heat transfer, I am starting with a simple via. The idea is then to set the convection and radiation from my cylinder to be non-existant. I would like to then set a temperature and a heat flux to further find a thermal resistance of this via by using:
It seems that I don't understand how to set the boundaries for this. My idea was to set actually a "room temperature" of 25[degC] as initial condition and add a heat flux of Q at one of the edges of the cylinder. However, it returns the following error:
Failed to find a solution. The relative residual (4.1) is greater than the relative tolerance. There was a warning message from the linear solver. Iterative refinement triggered. Returned solution is not converged. Not all parameter steps returned.
I've set both my via radius and my heat flux to be parametric (from 0.05 mm to 0.15mm and 1 to 10W, respectively). You have my COMSOL file attached to this.
Thank you in advance.
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