Latest Discussions - COMSOL Forums Most recent forum discussions Mon, 20 Jan 2020 20:56:53 +0000 COMSOL Forum: Latest Discussions additional boundary condition of normal component of electric field on metal boundàry <p>The below post is related to an <a href="//">archived discussion</a></p> <hr /> <p>[May be an older post, but i also have the same question, how to impose addtional boundary condition of continuity of normal components of electric field on the surface of the metal while doing the mode analysis ]</p> Mon, 20 Jan 2020 20:56:53 +0000 4.2020-01-20 20:56:53.250171 Topology optimization of conjugate heat transfer problem <p>Need information regarind Topology optimization application to natural convection problem in COMSOL. Required some documents or .mph files to implement</p> Mon, 20 Jan 2020 18:17:37 +0000 4.2020-01-20 18:17:37.250161 ICPF boundary condition <p>Hello,</p> <p>Using transport of diluted species,</p> <p>I am trying to model the acutation of an impc (ionic polymer metal composite) and as a first step i am trying to solve PNP equations for the conecntartion &amp; charge distribution inside membrane.</p> <p>the problem i am having is with the boundary conditions, i cant find a way to specify a negative fixed charge inside the membrane.</p> <p>i specified an input voltage and a ground, the initial concentrations but the fixed charge i am having trouble with</p> <p>**the impc is a nafion or flemion membrane with electrodes deposited on it's surafce under a potential difference the cation concentartion inside the membrane changes reulting in actuation</p> Mon, 20 Jan 2020 17:04:57 +0000 4.2020-01-20 17:04:57.250151 Couple a 3D with a 1D model <p>Hello,</p> <p>I would like to calculate the heat conduction in a metal plate, which is cooled with cooling water that flows through a borehole in the plate. The conduction in the plate should be modeled in 3D. For the cooling water only the temperature should be modeled in 1D (in flow direction) using heat transfer coefficients for the heat transfer from the plate to the water. How could this be done ?</p> Mon, 20 Jan 2020 15:23:14 +0000 4.2020-01-20 15:23:14.250141 TableFeature addColumn does not modify Table <p>Hi,</p> <p>I am trying to create a Result Table in the App Builder using this code:</p> <pre><code>String tableTag = model.result().table().uniquetag("dott"); TableFeature table = model.result().table().create(tableTag, "Table"); </code></pre> <p>Later, when I got the results I try to add them column by column using this method:</p> <pre><code>table.addColumns(new String[]{"time"}, extraArray); table.addColumns(new String[]{""+thickness}, realdata); </code></pre> <p>Both <code>extraArray</code> and <code>realdata</code> are <code>double[][]</code> according to the reference. But when I display the Table in a resultstable view, the Table is empty (also when I try to get the data with e.g <code>getColumnHeaders</code> the added Columns do not show up)</p> <p>Is there any reason for this. Where did I make a mistake?</p> Mon, 20 Jan 2020 10:58:44 +0000 4.2020-01-20 10:58:44.250131 Comsol Crashes due to a fail in writing core dump <p>Hello everyone I am using Comsol 5.5 on windows 7, with 32 GB ram. Every time I run my model, after a couple of time steps, the comsol window closes and a new error file (*.log) apears in the installation folder containing the following content:</p> <p>a fatal error has been detected by the java runtime environment: exception access violation Failed to write core dump. Minidumps are not enabled by default on client versions of Windows . . please note that the same model runs perfectly on my laptop ( win 7, 8 GB Ram).</p> Mon, 20 Jan 2020 10:06:50 +0000 4.2020-01-20 10:06:50.250122 Need help, after optimized, there is only a 2D flat left <p>The model is a 3D plate, loading on the top. When optimize the structure (the objective is to maximize compliance), there is only a 2D flat left. I already set a constrain of volume which using the Integration, but the result have not changed. Somebody help me, what should I do to optimize the structure while keep part of the volume.Thanks a lot!!</p> Mon, 20 Jan 2020 05:39:23 +0000 4.2020-01-20 05:39:23.250113 Velocity input: surface waves <p>Hi,</p> <p>I am designing a numerical wave tank using COMSOL to study FSI problem (Fluid structure Interaction, Two phase flow, Phase field) . At present I am using mesh displacement for a moving paddle to generate waves.</p> <p>I would like to generate waves based on inlet velocity, the inlet velocity need to be defined as a User Defined Function based on orbital velocity of particles in the fluid.</p> <p>A C++ code is available to determine the inlet velocity, may I know how this can be incorporated in the COMSOL model? Or is there any similar solved problems available for COMSOl?</p> <p>Dharma</p> Mon, 20 Jan 2020 04:50:06 +0000 4.2020-01-20 04:50:06.250103 How to export parametric sweep results with different domain among different runs? <p>I am using the Mathematics PDE general form module to solve some PDE. When I export the results (say the solution at the final time step) to .txt format, the resulting file has two columns. The first column is the spatial coordinate, and the second column is the data I want.</p> <p>Now suppose I do a parametric sweep, and each sweep has a different spatial domain (it is still a 1D interval, with the same number of uniformly-spaced points, just that the coordinates are scaled differently). If I want to export all results in the same .txt file, then we it fails because the solution is defined at different coordinartes for different runs. Are there any ways to export them all in one (rather than exporting each result separately and manually)?</p> Mon, 20 Jan 2020 01:17:12 +0000 4.2020-01-20 01:17:12.250102 solving wave equation on composite domain <p>I have the most simplest composite domain with two 1x1 subdomains connected by an interface at y=1.</p> <p>Now, this interface satifies continuity condition for the displacement and flux as they do. And also,. I have two different wave velocity (i.e., young's modulus and density) for the two subdomains. I can't seem to find how to create this interface and define the wave velocities correctly.</p> <p>Can anyone help me to find appropriate options?</p> Sun, 19 Jan 2020 19:52:28 +0000 4.2020-01-19 19:52:28.250092 Hydrogen Peroxide decomposition modeling <p>Dear Proffessionals,</p> <p>I am new to Comsol and looking for a possibility to model the decomposition of concentrated hydrogen peroxide on silver catalyst under the pressure. can you please advise me the steps I should take and if its possible to do with Comsol software. I will highly appreciate your help. Liquid flow is 70 m cub per second under the pressure of 76 bars. The parameters required to study are: - Pressure rise - Expanssion ratio In order to equalize the crossection of inlet and outlet.</p> Sun, 19 Jan 2020 15:39:37 +0000 4.2020-01-19 15:39:37.250091 Unable to get Error vs iteration number plot for convergence plot <p>Hi,</p> <p>I couldn't get the error vs iteration number plot in comsol 5.3a. Every time reciprocal step size vs time step is coming as default convergence plot. Which is not really helpful for error plot representation. Can anyone suggest how to enable error vs iteration number plot in comsol 5.3a? i used get that in 4.3 version.</p> Sun, 19 Jan 2020 14:05:55 +0000 4.2020-01-19 14:05:55.250081 Errors in External material model <p>Dear All:</p> <p>I developed an inelastic model by using external material model. However, I always got errors like:</p> <p>Recoverable error in residual, but solver could not recover. Time: 4.5 s. Last time step is not converged.</p> <p>It works well in elastic stage, but cannot run even one step when failure occurs. I doubted this issue may result from Jacobian matrix. In my model, the model is developed with respect to the incremental strain and stress, rather than the total strain as given in the BLOG. I am wondering what reasons could induce such issues for such model. Could you please give me some help about that?</p> <p>Thanks a lot.</p> Sun, 19 Jan 2020 02:38:37 +0000 4.2020-01-19 02:38:37.250072 i want to compare the analytic solution with the solution obtained with comsol <p>Hi , i calculate the analytic solution of the distribution of temperature in a hollow cylinder . I did the simulation in comsol , and i draw the temperature in comsol see figure 1</p> <p>my problem now i want to calculate the error between the analytic solution and the simulation when i tried to define a function analytic in comsol and use it after , the comsol don't reconize it in the result section see figure 2</p> <p>please help</p> <p>thanks</p> Sat, 18 Jan 2020 14:25:31 +0000 4.2020-01-18 14:25:31.250071 Solving steady-state two-phase creeping flow <p>Hi,</p> <p>I am trying to simulate steady-state two-phase flow of air and water in a conduit which has an air water interface. The flow is pressure gradient driven and is steady and uniform. At the air water interface, the velocity as well as shear stress should be continuous but the pressure should be discontinuous. I tried simulating the flow giving two creep flow in air as well as water domain. But the obtained velocity profile was not uniform throughout. And the pressure at the interface was continuous. I also tried simulating the flow by giving a single creep flow with different fluid properties at the air and water domain. Still the result was same. Requesting you to please help me in giving the above boundary conditions at the air-water interface so as to get the correct result. Thanks.</p> Sat, 18 Jan 2020 11:55:44 +0000 4.2020-01-18 11:55:44.250061 Magnetic fields : Coil error - solve in Coil Geometry Analysis step <p>Hei.</p> <p>Im building a gradient coil for MRI. The model consists of many square coils. When im building it im getting an error " Numeric coil Coil 1 (coil1) not solved for. Solve it in a Coil Geometry Analysis step. "</p> <p>any idea whats wrong.</p> Sat, 18 Jan 2020 11:39:21 +0000 4.2020-01-18 11:39:21.250051 Solve Errors <p>Hello what capacitance (self or mutual) does electrostatics(es) provides?</p> Sat, 18 Jan 2020 11:27:28 +0000 4.2020-01-18 11:27:28.250041 Optical property <p>I would like to add a light factor (absorbing factor, scattering factor) for each layer of skin. Can you tell me how to do it?</p> Sat, 18 Jan 2020 09:29:00 +0000 4.2020-01-18 09:29:00.250033 temperature distribution by depth <p>I'd like to see temperature distribution by depth. Please</p> Sat, 18 Jan 2020 09:24:45 +0000 4.2020-01-18 09:24:45.250023 How to define a variable for a range of values? <p>Hi,</p> <p>I am trying to simulate a spontaneous fluid uptake process in a rock where capillary pressure is the driving force. I am using Coefficient Form PDE physics. In such a case, only damping coefficient and source term are non-zero. The source term (f) is -d(d(Pc,x),x). Here, I would like to define Pc as a variable under Global Definitions wherein for its expression I want to write 2*sigma/r.</p> <p>However, Pc is different for different values of r. My question is how can I incorporate this in COMSOL? How do I define Pc as something that varies for a range of 'r' values. At different Pc values, subsequent variables are also calculated such as Se, krw, etc.</p> <p>I would appreciate your help in setting up this problem in COMSOL.</p> <p>Thanks</p> Sat, 18 Jan 2020 06:00:18 +0000 4.2020-01-18 06:00:18.250012