Latest Discussions - COMSOL Forums Most recent forum discussions Fri, 20 Sep 2019 10:38:27 +0000 COMSOL Forum: Latest Discussions Partition coefficient and slope of liquidus line <p>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!</p> Fri, 20 Sep 2019 10:38:27 +0000 4.2019-09-20 10:38:27.242913 Problem With Inducing Current In A Moving Conductor Place In Constant Magnetic Field <p>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.</p> Fri, 20 Sep 2019 06:22:45 +0000 4.2019-09-20 06:22:45.242901 design of gas sensor in comsol <p>sir, I want to model and simulate gas sensor for detection of some harmful gas.</p> <p>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</p> Thu, 19 Sep 2019 21:46:16 +0000 4.2019-09-19 21:46:16.242891 How can we make an animation with 3D plot in 1-D environment <p>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".</p> <p>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?</p> Thu, 19 Sep 2019 20:51:09 +0000 4.2019-09-19 20:51:09.242882 heat source <p>Hello,</p> <p>with modesty, I am trying to model the a pulsating heat source at the nanoscale .<br /> 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 .</p> <p>Thanks,</p> <p>Dib</p> Thu, 19 Sep 2019 14:31:07 +0000 4.2019-09-19 14:31:07.242841 Static Loading and Voltage generation curve on PZT material <p>Hi,</p> <p>I need to model a Direct Piezoelectric effect, with a ramp load followed by static load and get the electric potential generated.</p> <p>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.</p> <p>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 .</p> <p>Please suggest some solution.</p> <p>Regards Rahul Aggarwal</p> Thu, 19 Sep 2019 11:07:03 +0000 4.2019-09-19 11:07:03.242821 Trouble modelling fluid flow (air) between two roofs of a biogas plant <p>Hello!</p> <p>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:</p> <ol> <li>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. </li> <li>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.</li> <li>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.</li> <li>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.</li> <li>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.</li> </ol> <p>Can anyone elaborate on what I might be doing incorrectly, or if the model is correct, where my thinking and expectations are off?</p> <p>Any help would be greatly appreciated. Thank you in advance!</p> Thu, 19 Sep 2019 08:41:46 +0000 4.2019-09-19 08:41:46.242801 Electric Field normal to a Surface <p>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!</p> Thu, 19 Sep 2019 04:42:45 +0000 4.2019-09-19 04:42:45.242782 Check orthogonality of fiber modes <p>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)?</p> <p>I have also tried to use adaptive refinement but the dot product didn't improve as in fig2.</p> Wed, 18 Sep 2019 19:12:30 +0000 4.2019-09-18 19:12:30.242772 Comsol Beam Displacement Solution Very Off <p>To verify my comsol results, I evaluated a round solid aluminum beam with the following specifications and load case:</p> <p>beam diameter: 28mm beam length: 300mm</p> <p>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</p> <p>Running a Stationary Study, I receive the following outputs: Volume Maximum Total Displacement (mm): 0.2741</p> <p>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</p> <p>Am I overlooking something or is COMSOL outputting very wrong values?</p> Wed, 18 Sep 2019 17:30:07 +0000 4.2019-09-18 17:30:07.242762 Undefined material property 'E' required by Linear Elastic Material 1 <p>This should be really easy but its driving me nuts. This is the error I get when I hit compute:</p> <p>Undefined material property 'E' required by Linear Elastic Material 1 - Plot: surf1 (Surface)</p> <p>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.</p> <p>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.</p> Wed, 18 Sep 2019 17:27:30 +0000 4.2019-09-18 17:27:30.242761 How to calculate the change in temperature of a point in the surface of the structure? <p>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.</p> <p>Now my question is, how can I calculate <strong>temperature</strong> and <strong>change in temperature</strong> in the core (waveguide) area?</p> <p>Thank you! The version is Comsol 5.4.</p> <p>With best regards Om Raj Sapkota</p> Wed, 18 Sep 2019 15:09:42 +0000 4.2019-09-18 15:09:42.242753 Anisotropic Viscosity <p>I might be missing something obvious but how do I specify anisotropic viscosity in laminar Flow(spf) module? Any help is appreciated.</p> Wed, 18 Sep 2019 10:27:35 +0000 4.2019-09-18 10:27:35.242751 Problem with Extremly Thin Object <p>Hello everyone,</p> <p>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 <img class="latexImg" src="data:image/png;base64,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" />. 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.</p> <p>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!</p> <p>Best regards</p> Wed, 18 Sep 2019 09:11:31 +0000 4.2019-09-18 09:11:31.242731 Discretization toggle cannot be found under show? <p>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.</p> Tue, 17 Sep 2019 20:12:49 +0000 4.2019-09-17 20:12:49.242681 Heat Transfer with PCM (phase change material) <p>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.</p> <p>Sebastiano</p> Tue, 17 Sep 2019 14:20:34 +0000 4.2019-09-17 14:20:34.242671 how to take variable(curvature)into comsol 5.4 <p>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.</p> Tue, 17 Sep 2019 12:10:23 +0000 4.2019-09-17 12:10:23.242653 COMSOL with MATLAB <p>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.</p> <p>Thank you</p> Tue, 17 Sep 2019 11:23:59 +0000 4.2019-09-17 11:23:59.242651 SAW Delay Line Gas Sensor <p>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</p> Tue, 17 Sep 2019 11:06:39 +0000 4.2019-09-17 11:06:39.242641 Ptype semiconductor material <p>how we can run simulation without semiconductor module licence in comsole 5.4 for simulation of ptype and ntype material</p> Tue, 17 Sep 2019 07:24:03 +0000 4.2019-09-17 07:24:03.242601