Hello,
I am a new user of the COMSOL software, and I was wondering if you guys can orientate me on how to best simulate the heat transfer of air in a closed incubator, which also has a fan located inside to help disperse the heat.
I want to compare analyze different materials and compare their insulating properties (for the incubator), as well as, study the impact of the incubator geometry on the fluid flow/transfer.
Any help that you can provide would be amazing.
Thanks in advance
hi would I like to know if there is an example simulated a Rotating-Wave Electromagnetic?
Thank you.
Hi all!
COMSOL newbie here haha. I am trying to model the flow of compressed hydrogen through a cold pipe, and essentially, I want to see how much the temperature of the hydrogen will cool down as it flows through the pipe in steady state conditions.
The pipe is Copper and is at 77 K, whilst the hydrogen (700 bar so density is at 42 kg) is at 233 K and entering at a flow rate of 0.06 kg/s. I am using the turbulent k-eps conjugate heat transfer flow module but I am not sure why it is not working. When I run the model, tThe temperature of the entire system (fluid and solid domain) just stay constant at 233 K....
I have defined an inflow, outflow and initial values 2 (233 K for fluid, whilst Initial values 1 is 77 K for Copper pipe). have also defined inlet and outlet. My boundary conditions are shown in the image attached.
Does anyone know what could be wrong? :(
Cheers, James
Hi, I am trying to model the shape of a charged fluid-fluid interface in presence of an external electric field. It a 2d model, where the electric field is generated by a parallel plate capacitor type arrangement. in the space enclosed by the plates there are two fluids. The fluid-fluid interface is charged. The balance of surface tension at the interface with Maxwell stress due to charges and electric field should determine the shape of the interface. I am using Two-phase fluid flow Level set function to track the interface and Electrostatics module to model the Electric field. However, Comsol does not provide any multiphysics coupling between these two modules, and hence is not able to solve for the interface shape. Any suggestions on how to couple two-phase fluid flow module (level-set function) and electrostatics module is most welcome. Thanks
I have interpreted power system in the 2D axis coordinates and used max/min without doubt about this function.
In this analysis, the field was focused on the triple point when visually checked But maxpoint indicates elsewhere. I checked the triple point separately, and could confirm that it also greater than max point. Also, the value of the maximum data set was less than the value confirmed by a separate point.
I checked the electric field with ec.normE Am I mistaken about the max or field function?
Issue: I am calculating the eigenmodes of some electromagnetic structure. Afterwards, I want to evaluate an overlap integral between the fields of two different eigenmodes over some domain within the structure. How can I do that?
Approach so far:
This works perfectly; however, it is not what I actually want. Instead of calculating the olverlap of an eigenmode with itself (as currently defined in step 3.) , I want to calculate an overlap intop1( conj(emw.Ex1)*emw.Ex2 ), where emw.Ex1 is the electric field of mode 1 and emw.Ex2 is the electric field of mode 2. Is this possible?
Hi,
I am simulating a bubble rising problem using Moving mesh method. I have a problem and I do appreciate your help. The problem is here that the bubble rises in water normally due to gravity, but the bubble radius decreases over time, which I think is not physical. I refined the mesh several times, but the problem did not disappeared. I think something should be done with the settings of moving mesh. By default the water tank and the bubble are deforming domain and no more settings. Does anyone know what the problem is?
Thank you Hamid
Hello,
i had some weird results when simulating the transmission and reflection of metal nanostructures on glas, using and in and out port. For testing purposes i created a simple 2d file with a single air/glas junction, to verify if i get the proper transmission and reflection spectra of the used glas, but it just returned a very strong noise around levels that aren't even close to the expected values. Any help would be very appreciated.
Dear Sir/Madame,
I am new to Comsol Multiphysics and I am having difficulties with the lumped port/element boundaries from the Electromagnetic Waves, Frequency Domain physics section. I recreated the Log-Periodic Antenna from the RF module. I got this to work just fine using the manual from comsol. Now I wanted to play around with this and change the antenna material to aluminum instead of the PEC boundaries (similar to real life antenna's).
To do this I got rid of the last difference operation as specified in the step by step guide (which I attached for convenience). Now instead of having only 2 domain elements we have multiple. In the original file all domains had the material selected as air and the antenna had PEC boundaries. Instead I now chose aluminum and selected all antenna domain elements.
In my head the lumped parts are now in between two conductive boundaries (aluminum instead of PEC), yet when trying to solve the study step Comsol gives the error: "Uniform lumped port should be placed between two conductive boundaries. - Feature: Type: Lumped Element Tag: lelement1 Operation: LumpedElement (lelement1) - Feature: Type: Lumped Port Tag: lport1 Operation: LumpedPort (lport1)".
So I am probably missing something. In an attempt to solve the problem I tried to reapply the PEC BCs at all boundaries (just for the sake of checking), yet this gives the same error. Perhaps i am making a rookie mistake or there is an easier way to create an aluminum antenna. All help is sincerely appreciated
Thanks in advance, Gijs Mast
Ps. I included: 1. The comsol manual to a log-periodic antenna 2. a figure which shows the location of an lumped element in between the aluminum domain elements of the antenna. 3. A comsol mph file which contains my attempt to solving this problem
Dear all, I have a question about a model I am creating (attached): I have a pump connected to a large oven. In this oven there is a cylindrical chamber containing water that dries. This chamber is closed and has a hole in its lid. My purpose is to determine the evolution of the relative humidity in the gas mixture inside the chamber and in the oven. In addition, the drying process is maintained at an absolute pressure of 200 mbar: when water vapour is created due to evaporation, this pressure rises, the pump starts to suck it up until it falls back to 200 mbar. I use a Laminar flow+ moist transport module; My question is how can I add this condition to the Vacuum pump module present in Laminar flow?
Hello all,
I am trying to model a semiconductor device that has a bottom ground contact and a doped active area with a contact, surrounded by an isolated doped region. The model converges nicely at zero bias and small applied biases, but when the bias is such that the depletion region extends into the isolated doped region, I run into convergence issues. Any advice would be appreciated.
Hello!
I am new to comsol and am still learning a lot of new things, I know my question has probably been asked many times, but I still can't figure a way to solve my problem:
I want to simulate a voltage with two frequencies, such as 50 Hz and 350 Hz to test the influence of the third harmonic on the capacitance/permittivity of my dielectric. I am using the time dependent study and have entered Asin(wt) + A/2sin(3wt) for my voltage electrode, my model looks a little like the AC/DC example of capacitor_ac, except with an additional guard ring. My model works so far, I can see my field lines and have my current values, but I somehow can't simulate the capacitance/permittivity of my dielectric? I have read on this forum that people recommend the frequency domain study to simulate capacitance/permittivity, but I think this study wouldn't be relevant to my problem, since I will be defining my two frequencies. Should I be tackling this problem another way instead? Does somehow maybe have a better idea? Would appreciate help!
Jun
I’m doing simulation of airflow through porous media. According to the charactheristics of the flow and the geometry, the flow is turbulent, so after doing some simulations, the physics chosen was k-epsilon Low-Re, because of the wall treatment (Low Re). Geometry is a 2D rectangle representing a long tube with the porous bed in the middle of it.
I included a volume force in order to simulation porous media. At flow conditions, the equation that represent it is Ergun Equation ( that could be expressed as Forchheimer eq). My implementation was as simple as :
So, when I defined a horizontal cut plane in the middle of the bed to see velocity profile, I found a problem because, a velocity peak is shown at each side, near to the wall (fig 2 and fig 3). Since properties are isotropic, there no reason for this, so, it's simply wrong.
I think it is not a boundary layer problem because I simulated it when having a fully developped flow and with 12 boundary layers (as default), shown at fig 1. Minimum mesh quality is 0.45, which I think is not so bad. I tried also using laminar flow conditions and Fluid and Matrix Properties as default which uses Darcy's Law, but the profile was similar.
Has anyone had this kind of problem? Am I missing something? How could I overcome this problem??
thanks in advance, Jhoan G.
Hi all. I'm very new to COMSOL, and tried to model this file off of one of the included COMSOL modules. I'm trying to solve a double pipe heat exchanger problem, which worked fine with the module until I used steam as the fluid in the inner pipe, then I began to get a lot of errors.
After that, I made my own file, copying the module but only including what seemed absolutely necessary for a temperature vs length study, yet I receive the same errors when I try to use steam in the inner pipe.
Can anyone help?
Here are the errors:
I am using Comsol 5.4. I am working on the physical model of Resistive RAM. I have to connect bottom terminal of model to the drain of n-channel MOSFET which I am taking from Electrical circuit module. My present approach is to make bottom terminal into voltage type and inputing the voltage from drain end of MOSFET. How do I do that? What variable should I use??
Hello, I am simulating piezoelectric stack of AlN that is sandwiched between two electrodes and the sandwich sits on a Si substrate. I remember doing this in version 4 and now I am using v5.5 but for some reason, when I select the solid model to be anisotropic uunder linear elastic material tab, Young's modulus (E) and Poisson's ratio (nu) seems like they are still required as well as relative permittivity. In isotropic material case these are already there and epsilon is not so I understand the requirement for the relative permittivity. However D matrix is there and the solver wats to know E. Why is that?
Thanks,
I want to model a nanosphere with positively charged core and negatively charged shell. How can i do it?
I have a model of a beam in the form of a sandwich structure with a certain thicnkess of center region and outer layers I want to perform a simple optimization study where I model the beam as a cantilever and apply a point load at a free end. Based on the deflection and stress results, I want to find out the minimum weight of the beam for best design and the optimum thickness of the beam layers. This tutorial gives an idea of my beam model, but it is simpler without the piezeolectric object.
https://www.comsol.com/model/piezoelectric-shear-actuated-beam-24
The problem is that I don't have access to the Optimization module. Is there a way I can perform a simple design optimization of finding minimum weight (objective function) as des by using simple parameter relations (beam thickness) in COMSOL without the optimization module? I also tried looking at some tutorials available at the COMSOL application gallery but all of them use the optimization toolbox. Ideally this would be my setup.
Design Variables: Beam middle layer thickness and outer thickness Constraints: Max. Deflection, Max. equivalent stress and perhaps stiffness Objective Function: Weight of the beam (mass)
I also have two equations that relate each thickness (middle and outer) to the weight (objective function). Is it possible to write a simple script (possibly in MATLAB) to model these equations and import it into COMSOL and find the minimum mass without the optimization module?
Thank you.
Hi, I'm new to COMSOL and I'm trying to model a piezoelectric energy harvester, in which I use Copper for my electrodes. To which I need to fill in the coupling values for it.
I tried to simulate a piezoelectric energy harvester using frequency modal analysis. If I disabled the electric circuit physics, I can calculate the average of electrical potential at the boundary of the electrode which I considered to be the EMF of the piezoelectric device. The value seems reasonable. After I enable the electrical circuit with a resistor and voltage from terminal from electricstatics physics, the voltage across the resistor I get is 0, and when I calculate the average of the electrical potential at the same electrode boundary, werid value is seen. Can someone help me understand this?