Latest Discussions - COMSOL Forums https://www.comsol.com/forum/ Most recent forum discussions Sat, 18 Nov 2017 23:41:31 +0000 COMSOL Forum: Latest Discussions https://www.comsol.com/shared/images/logos/comsol_logo.gif https://www.comsol.com/forum/ Comsol export to Techplot https://www.comsol.com/forum/thread/160242/comsol-export-to-techplot?last=2017-11-18T23:41:55Z <p>Is it possible to export comsol results to techplot?</p> Sat, 18 Nov 2017 23:41:31 +0000 4.2017-11-18 23:41:31.160242 Convergence Issues caused by highly nonlinear equations https://www.comsol.com/forum/thread/160232/convergence-issues-caused-by-highly-nonlinear-equations?last=2017-11-18T22:39:38Z <p>Dear all,</p> <p>I am running a coupled HM model for porous media. In this model, the water retention curve is given Van Genuchten model, which is a highly nonlinear function, shown as:<img class="latexImg" src="data:image/png;base64,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" />. In this equation, Se is the effective degree of saturation, alpha is related to the gas entry value, Hc is the capillary height, N,M are the parameters determined from experiment. I coupled, alpha, with the volumetric strain of the porous media. However, I found the convergence issues always occur when the volumetric strain experience a fast change. As this coupling is very important to the whole model, I cannot neglect it.I think this issue should be caused by highly nonlinear property of the Van Genuchten. But I still cannot find a good way to solve it. Does anyone have experiences to treat such a convergence issue? Thank you so much for your help.</p> <p>Yu</p> Sat, 18 Nov 2017 22:39:38 +0000 4.2017-11-18 22:39:38.160232 Reference error in meshes https://www.comsol.com/forum/thread/160222/reference-error-in-meshes?last=2017-11-18T18:28:18Z <p>Can someone please explain what this error message means?</p> <p>A problem occurred when building mesh feature 'Reference 1' in 'Mesh 2'. Failed to build feature 'Copy Face 1' in sequence 'Mesh 1'. Geometry object and mesh object are not compatible.</p> <p>Thanks, Dennis</p> Sat, 18 Nov 2017 18:27:20 +0000 4.2017-11-18 18:27:20.160222 Turek's benchmark https://www.comsol.com/forum/thread/160211/turek-s-benchmark?last=2017-11-18T10:45:04Z <p>Hello everybody, I have a question for you, hoping somebody can help. I'm using Comsol 5.3 to analyze Turek's benchmark (following the instructions found here: https://www.comsol.it/model/vibrating-beam-in-fluid-flow-9408), and it works fine. But I'm interested in change the velocity profile by assuming an average velocity U=10m/s instead of 2m/s, and what I get is that the solution doesn't converge.</p> <p>"Nonlinear solver did not converge. Time : 0.7432944384400323 Maximum number of Newton iterations reached. There was an error message from the linear solver. The relative residual (2.1) is greater than the relative tolerance. Last time step is not converged." And some warnings about inverted mesh in some points.</p> <p>Can you please help in some way? I tried to use a finer mesh, or the generalized alpha solver insted of the BDF, and I don't use any limits about minimum and maximum step (so that the program itself can choose), but nothing works.</p> <p>I attach the deformed beam in the last time-step, it also seems that the condition about velocity doesn't work, as the blue color corresponds to 0m/s.</p> <p>I hope you can help, and I thank you for any suggestions.</p> Sat, 18 Nov 2017 10:45:04 +0000 4.2017-11-18 10:45:04.160211 Simulation of Pure Shear to find shear modulus https://www.comsol.com/forum/thread/160202/simulation-of-pure-shear-to-find-shear-modulus?last=2017-11-17T23:10:03Z <p>I am in the process of finding shear modulus of a solid cube when it is loaded under the action of pure shear.</p> <p>As a part of pure shear, I want the vertical faces to rotate about vertical axis and at the same time I want horizontal faces to get contracted but they should always remain parallel. I am able to simulate simple shear, which obviously not giving me correct shear modlus, so is there any way I can simulate above conditionsor is there any other way to get shear modulus of a cube?</p> Fri, 17 Nov 2017 23:10:03 +0000 4.2017-11-17 23:10:03.160202 Perfectly Matched Layer (PML) issue https://www.comsol.com/forum/thread/160193/perfectly-matched-layer-pml-issue?last=2017-11-17T14:20:46Z <p>Dear COMSOL Users, I have applied PML on top of unit cell to produce surface waves, and according to correct solution, waves should be absorbed in PML and mode shapes with red, yellow, blue color must be produced on unit cell at top. But in my case I am not getting so, Please check the mode shape picture attached with this message.</p> <p>Please help me in this problem, why my mode shape after simulation is giving eigenfrequency real and imagnary values and PML is not absorbing the waves.</p> <p>Thank you for your support.</p> Fri, 17 Nov 2017 14:20:46 +0000 4.2017-11-17 14:20:46.160193 No shell interface in the structural mechanics module https://www.comsol.com/forum/thread/160161/no-shell-interface-in-the-structural-mechanics-module?last=2017-11-17T23:16:14Z <p>Hi, I don't have shell interface in the structural mechanics module. How can I add it?</p> <p>Thanks</p> Fri, 17 Nov 2017 13:39:52 +0000 4.2017-11-17 13:39:52.160161 Meshing Thin Dialectric in Air https://www.comsol.com/forum/thread/160072/meshing-thin-dialectric-in-air?last=2017-11-17T14:36:53Z <p>Hi All,</p> <p>New Comsol user here. I want to model the electric field in and around a thin dialectric (0.3um) sandwhiched between two conductive plates (3x60um) of thickness ~30um each in an air box. To get good resolution in the dialectric I swept it, dividing it into 5 layers. The air box cannot be swept and it gives an error when I apply a tetrahedral mesh because of the rectangular mesh on the sides of the dialectric (in contact with the air) created by the sweep. Meshing the entire model using the "Extremely Fine" mesh produces a mesh two tetrahedrals tall in the oxide which is not fine enough.</p> <p>Is there a way I can sweep the dialectric while applying a tetrahedral mesh to the air, get finer resolution in the dialectric with a tetrahedral mesh or is there something I haven't considdered.</p> <p>Thanks</p> Fri, 17 Nov 2017 01:13:58 +0000 4.2017-11-17 01:13:58.160072 Coulombic interactions in Plasma module https://www.comsol.com/forum/thread/160052/coulombic-interactions-in-plasma-module?last=2017-11-18T02:46:34Z <p>Hi, Does the plasma module considers coulomic interactions between the particles? And can we control it (for example its cut-off length, etc.)? Thanks.</p> Thu, 16 Nov 2017 18:28:28 +0000 4.2017-11-16 18:28:28.160052 Simple Tensile Test https://www.comsol.com/forum/thread/160042/simple-tensile-test?last=2017-11-16T21:06:13Z <p>Hopefully the fix can easily be managed. I am working with a 1mm^3 cube and want to back out a poisson ratio after applying a known displacement.</p> <p>Property values include Young Modulus (3000 MPa), density 1380 (kg/m^3), and poisson ratio (.4).</p> <p>I am applying a displacement of 1% (to one side, the other opposite side cannot move in the x direction). In the Y directions, the faces can only move in the Y and X direction while in the Z direction it can only move in the X and Z directions.</p> <p>The most dense mesh I have used is on the order of 100000 elements with element qualities of 1 (I am using cubes).</p> <p>My issue is that the displacments in the Y and Z directions provide maximum displacements that would back out a poisson ratio with error on the order of 10-15%. As this is a simple unit problem it should be closer to 1%. What common issues might be responsible for the skew?</p> Thu, 16 Nov 2017 18:16:49 +0000 4.2017-11-16 18:16:49.160042 Undefined value found in the equation residual vector https://www.comsol.com/forum/thread/160031/undefined-value-found-in-the-equation-residual-vector?last=2017-11-16T16:50:06Z <p>The below post is related to an <a href="//www.comsol.com//forum/thread/32904/undefined-value-found-in-the-stiffness-matrix">archived discussion</a></p> <hr /> <p>Feature: Stationary Solver 1 (sol2/s1) Undefined value found. - Detail: Undefined value found in the equation residual vector. There are 11000 degrees of freedom giving NaN/Inf in the vector for the variable comp1.u_solid. at coordinates: (745.454,-285.843), (745.429,-285.848), (745.405,-285.853), (745.378,-285.859), (745.351,-285.864), ... There are 11000 degrees of freedom giving NaN/Inf in the vector for the variable comp1.v_solid. at coordinates: (745.454,-285.843), (745.429,-285.848), (745.405,-285.853), (745.378,-285.859), (745.351,-285.864), ...</p> <p>I've been facing this issue of late. My geometry is a bit abnormal since I'm modelling the heart, I'm drawing the outline from a confocal microscopy image using illustrator, exporting as dxf and then importing it through the geometry import tool. I've given all the necessary properties, but I'm unable to understand this error regarding my geometry. Any help is much appreciated.</p> Thu, 16 Nov 2017 16:50:06 +0000 4.2017-11-16 16:50:06.160031 Geometry with no domains applicable https://www.comsol.com/forum/thread/160021/geometry-with-no-domains-applicable?last=2017-11-16T15:09:36Z <p>Hi,</p> <p>I have built a 3D model for multi-layers geometry. The surfaces of the layers were import with interpolation function from excel sheets and built with parametric surfaces, then I built a work plane and extrude to make a block, and convert the block and parametric surfaces into solids to make the multi-layer geology. Also I added some line segments in the block which will be set as edge sources. The trouble comes after forming union, no domains are applicable now, in the bottom messages window it says 'Finalized geometry has 16 boundaries, 34 edges, and 28 vertices.', no domains mentioned. I change the relative repair tolerance value to 1E-7 and it worked well with all expected domains available, but only once, I changed to another values and then changed back to 1E-7 but never worked well again. Anyone knows why domains cannot be defined and how to get rid of this problem</p> <p>Best regards, Shuhan</p> Thu, 16 Nov 2017 15:09:36 +0000 4.2017-11-16 15:09:36.160021 how to export a deformed shell https://www.comsol.com/forum/thread/160011/how-to-export-a-deformed-shell?last=2017-11-16T14:12:03Z <p>Hi</p> <p>I have a model which consists of a shell and a solid. When I want to remesh my deformed model, I receive an error 'deformed configuration can only be created for solid geometries'. So what should I do? How can I remesh the shell part? I want to export the whole model (shell and solid ) for further study . Any suggestion?</p> <p>Kindregards</p> Thu, 16 Nov 2017 14:12:03 +0000 4.2017-11-16 14:12:03.160011 Multiple study steps : Stationary and Time dependent https://www.comsol.com/forum/thread/160002/multiple-study-steps-stationary-and-time-dependent?last=2017-11-16T11:50:40Z <p>Hello, I am simulating a vibrating mechanical structure. I need to apply a sinusoidal exictation force (Fex=F0.sin(2.pi.freq.t)). My structure is pre-stressed by a stationary compression force P0. Using only the Time Dependent study results in big oscillations of the structure at the beginning due to the sudden application of P0. I added a stationary study in the computation sequence in order to calm the initial oscillations but I keep receiving error messages about the variable 't' that is apprently not defined in the stationary study. How to solve this? Thanks Khaled</p> Thu, 16 Nov 2017 11:02:36 +0000 4.2017-11-16 11:02:36.160002 COMSOL module and functionality for acoustic simulation of large room https://www.comsol.com/forum/thread/159951/comsol-module-and-functionality-for-acoustic-simulation-of-large-room?last=2017-11-15T16:00:43Z <p>I would like to use comsol for my project which deals with time domain acoustic simulation (in ultrasound domain) of a large room. Of Special interest are following:</p> <p>1). Placing of multiple source at various location in a room. 2). For each source I want to specify what kind of signal it should emit. (could be a chirp, a sine burst or an Impulse). 3). Setting the reflection coefficient walls. 4). placing of multiple receivers in the room. 5). sound pressure level at each receiver. 6). Visualization of reflections from the wall.</p> <p>I would like to request , if anyone knows weather simulation with these functionalities is possible or not in COMSOl, and if yes, what all modules do I need, then please let me know. As per my research I would need Multiphysics and Acoustics.</p> Wed, 15 Nov 2017 16:00:43 +0000 4.2017-11-15 16:00:43.159951 get material property https://www.comsol.com/forum/thread/159941/get-material-property?last=2017-11-15T14:32:41Z <p>Hello,</p> <p>I have a very simple question.</p> <p>I am using water in my model. Now I want to create a parameter with the desnity of water with temperature=273.15 K</p> <p>-> rho_0 = rho(material water, T=273.15 K)</p> <p>What is the syntax for such an expression?</p> <p>Thanks</p> <p>Alessandro</p> Wed, 15 Nov 2017 14:32:41 +0000 4.2017-11-15 14:32:41.159941 Plot values from a parametric sweep variable. https://www.comsol.com/forum/thread/159931/plot-values-from-a-parametric-sweep-variable?last=2017-11-15T13:55:15Z <p>Hi. My problem is really simple. I plotted 2 variables (velocity, pressure) from a model of a flow inside the eye. Then I created a parametric variable for the size of the eye. Now I want to do a plot Size/Pressure and Size/Velocity calculated in a precise point, to show how this variables are changing due to the size. Thank you very much. Jacopo Bevilacqua.</p> Wed, 15 Nov 2017 13:54:21 +0000 4.2017-11-15 13:54:21.159931 How to import stresses of a deformed object https://www.comsol.com/forum/thread/159921/how-to-import-stresses-of-a-deformed-object?last=2017-11-15T12:09:20Z <p>Hi all,</p> <p>I have loaded a plate in order to stretch it. Next, I have imported the deformed structure for further study. Now, my problem is how can I import its stress and strain tensors too?</p> <p>Thanks,</p> Wed, 15 Nov 2017 12:09:20 +0000 4.2017-11-15 12:09:20.159921 Nonlinear boundary condition https://www.comsol.com/forum/thread/159912/nonlinear-boundary-condition?last=2017-11-15T15:59:50Z <p>Hello, Supposing that we have a given structure in 2D Solid Mechanics simulation. We need to apply a boudary condition 'A' on a boundary named 'x' (a boudary force on face number 20 for example). The boundary condition 'A' is related to the vertical displacement 'v' of the boundary 'y' different than 'x'. How I can express this? For example, can I write A=A0v{y}?? I have already notice that we can write A=fct(v) which means that the boudary condition 'A' of the boudary 'x' is related to the vertical displacement of the same boundary 'x'. It seems to me that it is possible to do the same thing but with the displacement of another boundary 'y' but I dont know how to do it!! Thanks in advance for your responses Khaled</p> Wed, 15 Nov 2017 10:56:18 +0000 4.2017-11-15 10:56:18.159912 Perfectly Matched Layer https://www.comsol.com/forum/thread/159903/perfectly-matched-layer?last=2017-11-15T10:19:10Z <p>I want to apply perfectly matched layer at bottom layer of my unit cell, but I cannot find any option by using which I can select only bottom layer. Total domain of unit cell is being selected. Please help me in this regard, How I can apply Perfectly matched layer specifically at particular top or bottom layer of my unit cell. As if i selected all domain, other boundary and periodicity condition will get disturb.</p> <p>Thank You</p> Wed, 15 Nov 2017 10:19:10 +0000 4.2017-11-15 10:19:10.159903