Hi! I have a surface with an inclination of 9 degrees in an axisymmetric system of coordinates. I know that using -Vr and -Vz I get the electric field according to r and z. However, I want to get the electric field that is normal to my surface. How can I calculate this? Thank you very much!
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Electric Field normal to a Surface
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Trouble modelling fluid flow (air) between two roofs of a biogas plant
Hello!
I am currently modelling heat loss in a biogas plant (manure digester) placed on a farm. The digester is cyllindrical in shape, with a double domed roof. Between the two roofs, air is pumped through to assure an outflow of potentially dangerous gases leaking through the lower roof, where the inflowing air has the outside temperature, much lower than the temperatures inside the digester (10 degC for the inflow, 42 degC for the manure). I included a snapshot of the geometry under this post, as well as the model's MPH file. I use a combination of the CFD module (turbulent flow) and the possibilities for Heat Flow (Heat transfer in solids and fluids) in the basic licence (I do not have the Heat Flux module to my disposal). The following are the problems I encounter:
- I am having trouble modelling (or possibly, understanding the result of) the air flow between the roofs. As can be seen in the snapshots included (one in the plane of the inlet and outlet and one perpendicular to that), the airflow directly at the inlet and outlet is correct, but somehow the flow between the two roofs is in the direction of the inlet (negative x-components of velocity field), rather than the outlet, which seems odd.
- Also, it seems like the airflow from the inlet somehow penetrates the inner roof, which is a closed surface of a PVC foil, which by no means is permeable to such an extent.
- Thirdly, it seems like the velocity of the airflow between the roofs has the highest magnitude directly under the upper roof, where due to the no-slip condition imposed, I would expect the highest magnitude in the middle of the distance between the two roofs.
- On top of that, the result does not display a correct circulation of the biogas below the inner roof, or at least one would expect. The result shows a cold 'bubble' forming behind the lower roof near the inlet. This can be seen in the Temperature snapshot.
- Lastly, when integrating the Velocity magnitude over the surface of the inlet and doing the same for the outlet, shows a different value for the two. This should not be correct, because there is no other way for the inflowing air to exit the roof than the outlet on the other side.
Can anyone elaborate on what I might be doing incorrectly, or if the model is correct, where my thinking and expectations are off?
Any help would be greatly appreciated. Thank you in advance!
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Static Loading and Voltage generation curve on PZT material
Hi,
I need to model a Direct Piezoelectric effect, with a ramp load followed by static load and get the electric potential generated.
Practically, Under such load PZT material must decay its potential generated under milliseconds during static loading due to atomic reorientation. But thats not happening in case of this, instead it keeps on generating the potential directly proportional to the load curve.
I have attached the inputs for Solid Mechanics and Electrostatics Physics in INPUTS.jpg file. And also the output electric potential generated at the top circular surface in OUTPUT.jpg .
Please suggest some solution.
Regards Rahul Aggarwal
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How can we make an animation with 3D plot in 1-D environment
I'm new to COMSOL and watched the animation videos tutorials, but to work they aways have the options "Time" in "Loop over", over "Animation Editing".
I've realized that for this to be possible, it is necessary that in 3D Plot Grup appears the dataset (for the solution) but in 1D envoirment you dont have the option to choose the solutions, and get limited to "Data Set: None". So i think the question it is, how to generate 3D Plot Group that recognize the dataset in 1-D environment?
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design of gas sensor in comsol
sir, I want to model and simulate gas sensor for detection of some harmful gas.
How to made sensor with given width and distance between electrodes on substrate? And it's state of art like physics modules to be choosen,parameters etc...,. how to draw impedance curve in COMSOL? how to draw Time -resistance curve at different ppm of harmful gas? how to place sensor in bottom in Exposure model ? how to simulate response -concentration curve in COMSOL? how to write and used Navier-stoke eqn, poission eqn and write boundary condition for exposure , heat transfer, electrical condition? thanks in advance
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PROBLEM WITH INDUCING CURRENT IN A MOVING CONDUCTOR PLACE IN CONSTANT MAGNETIC FIELD
I have placed a moving aluminium conductor in a constant magentic field produced by a coil excied with constant voltage. I am unable to get any induced currents in the conductor. I am using magnetic fields physics and continuity is employed. displacement current density are ignored as i am using magnetic fields physics. And air medium is provided.
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heat source
Hello,
with modesty, I am trying to model the a pulsating heat source at the nanoscale .
the heat source in a spherical form is inside another sphere . IN pi / 2 the heat released is 20mK in a very short duration nanosecand (trigger). this is the first time I use comsol and I still can not find the method for controlling the source .
Thanks,
Dib
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Partition coefficient and slope of liquidus line
Hello, everyone. Recently, I have been doing the macrosegregation during solidification process of binary alloy. At present, I have opened three modules: laminar flow, heat transfer and dilute matter transfer, but I still don't find where the partition coefficient and slope of liquidus line are given. I hope someone can help me. Thank you very much!
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Which modules should I choose
hi,
What modules are needed to simulate droplet impact on a rotating disk with oil film
Thank you in advance for your answer!
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Which modules I need to select?
A droplet with a certain initial velocity is simulated to move with the rotating disk from the inlet.The interaction between the droplet and the pipe needs to be considered.Which modules should I choose? hank you in advance for your answer!
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Air levitation
I am trying to achiveve an air levitation and hopefully try and monitor the oscillations and vibrations caused on the body during the levitation. I need some ideas on how to create this in the simulation.
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Moisture Transport, Thin Moisture Barrier, Comsol Version 5.3
Is there any known way to link the inputs like vapor permeability or vapor resistance factor to material properties like diffusion coefficient (m^2/s) of water in a certain material or gas permeability (Barrer, cm^3/s/cm/cmHg) of water in a certain material. I have this values for water and PDMS but no idea how to link them to the model inputs.
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In a 2D axisymmetric model Is it possible to make thermal conductivity only in z plane?
In a 2D axisymmetric model for pulsed laser ablation, Is it possible to make thermal conductivity only along z plane, while using the heat transfer module?
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Is there any benefit to nondimensionalize the comsol model ?
Recently, i find that some scholars make all the parameter in their simulation model non-dimensional. What are the benefits of doing this ? Maybe, improving the calculation speed ?
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Problem with partition
Hi everyone! I have created an stl file from a voronoi tesselation with 10 nodes. I have two problems with it.
The first one is that, as you can see when importing the geometry in comsol, most of the lines are curves when they should be straight. I guess that this a resolution issue, because when I plot it in Matlab is correct.
The second one, which is the really important, is with partition. I need to create a block 1x1x1 and delete everything which is outside of it. I've tried with partition objects but it doesn't work. Anybody knows something about this?
Regards, Alfonso
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cylindrical ionization chamber
Hello,
I am designing cylindrical ionization chamber for muon detection. Cylindrical ionization chamber is like a cylindrical capacitor. In that, as a dielectric medium we use combination of 90 % argon and 10% co2. It has applied high voltage. inner cylinder work as a anode wire and outer as a cathode in this ionization chamber. Now, muon particle interacts with this gas molecules and produces ion electron combination from the gas. Produced electron from the interaction goes towards anode wire and produce signal and thats how I can detect particles.
Now my quation is here I have to apply multiple physics like elecric current, electrical circuit for current measurement and particle tracing module. But I am not able to find out proper tutorial regarding particle tracing.
could anyone help me?
Thanks and regards, Dhruv
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Error in multiphysics compilation.
Hi,
I'm trying to run a frug release from a Biomaterial Matrix. When I try to compute for study 2, it said there was an error but I do not know why.
Error in multiphysics compilation. Duplicate parameter/variable name. - Variable: comp2.c_drug - Variable: comp2.c_enzyme - Variable: comp2.c_peptide - Variable: comp2.c_peptidedrug
I've checked the busbar example in the tutorials and I can't find any differences between the example and my simulation.
Thanks
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Exotherm reaction in PFR
Hi everyone,
I am really new to Comsol and I am trying to model an exotherm reaction in a plug flow reactor: Species A reacts irreversible (first reaction order), the rate reaction is defined as rA=-krcA* where kr=Aexp(-E/(RT)) Since it is a exotherm reaction, the temperature is going to increase as species A reacts, which changes the value of kr. T is described as a differential function vCpdT/dz=(-HkrcA) - ah(T-Tw) So, these two are coupled since cA depends on kr that depends on T and T depends on cA. The wall of the reactor is held constant (adiabatic).
I assume steady state (time independent), cA & T depend just on Z-axis (along the reactor).
I have used "Transport of Diluted Species" to model the change in concentration since I have diffusivity. I have tried to use Global ODEs & DAEs to solve the differential form of the temperature without success.
Does anybody know how to proceed in order to get concentration and temperature profile along the reactor?
Thank you!
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Free Bar Modal Participation Factor
Hello,
I am just trying to model a simple free-free bar with an analytically calculated longitudinal resonance of 509.18 Hz. The size of the bar leads to a mass of 27,000 kg and an effective mass for the fundamental mode of 1/2 that. However, when I try to pull values from the "Effective Modal Mass" or "Participation Factors" tabs the numbers are so small (on the order of 10^-5).
How do I pull this effective mass value?
Thanks
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The two models are exactly the same, it ran well for the first time, but the second time it had an error
hello,everynoe I did a 3D model for solute transport a few days ago ,and it ran well. However I ran it again today and found that I was getting an error:
No consistent initial value found Unable to read or write to extra nuclear files The last time step does not converge
It is clear that there is no problem when running for the first time. The two models are set exactly the same. I don’t know where the problem is. Can someone help me?
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