Latest Discussions - COMSOL Forums https://www.comsol.com/forum/ Most recent forum discussions Tue, 19 Mar 2019 06:30:45 +0000 COMSOL Forum: Latest Discussions https://www.comsol.com/shared/images/logos/comsol_logo.gif https://www.comsol.com/forum/ About Pulse voltage https://www.comsol.com/forum/thread/230143/about-pulse-voltage?last=2019-03-19T06:30:45Z <p>hello I want to apply a pulse voltage in anode, so i I defined an analytic function as follows:flc1hs(sin(2<em>pi</em>t/0.0002),0.0001)<em>E_cell. But when i compute, the follow problem has occurred: 变量未定义。 - 变量: c - 几何: geom1 - 边界: 12-13 计算变量失败。 - 变量: comp1.siec.phisext - 定义为: unit_V_cf</em>voltage(c/unit_s_cf) 计算变量失败。 - 变量: comp1.siec.Ect - 定义为: comp1.siec.phisext-comp1.phil 计算变量失败。 - 变量: comp1.siec.eta_er1 - 定义为: comp1.siec.Ect-comp1.siec.Eeq_er1 计算变量失败。 - 变量: comp1.siec.iloc_er1 - 定义为: comp1.siec.i0_er1<em>(10^(comp1.siec.eta_er1/comp1.siec.Aa_er1)) 计算表达式失败。 - 表达式: (comp1.siec.iloc_er1</em>comp1.siec.d)<em>dvol 计算表达式的 Jacobian 矩阵失败。 - 表达式: (comp1.siec.iloc_er1</em>comp1.siec.d<em>test(comp1.phil))</em>(dvol)</p> <p>Anyone who has experience about this filed, please help me. Looking forward to hearing from you, thank you so much.</p> Tue, 19 Mar 2019 06:30:45 +0000 4.2019-03-19 06:30:45.230143 How to add geometry between studies in Comsol Multiphysics? https://www.comsol.com/forum/thread/230141/how-to-add-geometry-between-studies-in-comsol-multiphysics?last=2019-03-19T04:23:08Z <p>Hi Is it possible to add geometry between the studies and use the result of a previous study to solve the next one? I am going to simulate this situation (simple heat transfer in solids 2D): 1. One block of steel cooling from 1000 K by natural convection for 1000 s from the top surface (the other three sides are isolated). 2. After this time, another block of steel is placed on its top, and they cool for another 1000 s together from the top surface of the top block (so the heat flux BC is transferred from the top of the lower block to the top surface of the top block). I really appreciate if you guys do the simulation and send me the file, or at least guide me here please.</p> Tue, 19 Mar 2019 04:23:08 +0000 4.2019-03-19 04:23:08.230141 The Reflections of Ultrasound of an Obstacle https://www.comsol.com/forum/thread/230121/the-reflections-of-ultrasound-of-an-obstacle?last=2019-03-18T22:43:49Z <p>Hello!</p> <p>I built a model of acoustic interface which consists of a water domain and there is an obstacle(acrylic) inside. The transducer (PZT-5H) will transmitted a wave and will received it back after it hit an obstacle. I already received back the signal and represented it using point graph. However, there is something that I am unsure about. Can someone tell me whether there will be a reflection from inside of the obstacle? I mean is it supposed to be 2 signals from the obstacle, one from the wall and one from inside?</p> <p>Thank you.</p> Mon, 18 Mar 2019 22:43:49 +0000 4.2019-03-18 22:43:49.230121 Conditional boundary condition https://www.comsol.com/forum/thread/230102/conditional-boundary-condition?last=2019-03-18T17:15:27Z <p>Hello all I am simulating a peristaltic wave in a tube. I want to apply the inlet boundary condition as following: inlet is open and when the pressure at the inlet drops to some certain amount it closes (velocity=0, wall) and for the outlet: the oulet is closed (velocity=0, wall) when the pressure reaches to a cerain amount, it opens the outlet. Can you please help me to solve this problem?</p> <p>Thank you</p> Mon, 18 Mar 2019 17:15:27 +0000 4.2019-03-18 17:15:27.230102 Grille boundary condition https://www.comsol.com/forum/thread/230101/grille-boundary-condition?last=2019-03-18T17:07:48Z <p>I am having difficulties implementing the Grille boundary condition in Laminar flow (spf) in COMSOL 5.2a.</p> <p>Whether I set the quadratic loss coefficient (qlc) under the Grille Boundary node to zero or any non-zero value, I get the same result.</p> <p>As an example, I tested it for a simple pipe flow with an inlet (which is treated as a grille boundary with pressure boundary condition) and an outlet (also with a pressure boundary condition). Please see the attached .mph file. You can see by running the file for various values of qlc or 'static pressure curve data' that the pressure profile along the length of the pipe does not vary, nor does the flow rate.</p> <p>It looks like the Grille boundary condition is not working; that is, it is not implementing a pressure drop due to the presence of the 'grille'.</p> <p>Could somebody please help me figure out the solution to the problem. Thanks.</p> Mon, 18 Mar 2019 17:07:48 +0000 4.2019-03-18 17:07:48.230101 Interpolation file for heat source https://www.comsol.com/forum/thread/230091/interpolation-file-for-heat-source?last=2019-03-18T20:20:53Z <p>Good afternoon, colleagues! Help me please! I work in Somsol 5.3. I use the file with coordinates and power of heat source for the 2D model. x y power -0.5 0.5 0.033745233 -0.5 0.3 0.008032953 -0.5 0.1 0.02030695 -0.5 -0.1 0.027188813 -0.5 -0.3 0.022877194 -0.5 -0.5 0.022100812 -0.3 0.5 0.055818094 -0.3 0.3 0.181697745 -0.3 0.1 0.092770224 -0.3 -0.1 0.10023076 -0.3 -0.3 0.086700972 -0.3 -0.5 0.059760525 -0.1 0.5 1.49589704 -0.1 0.3 1.606590584 -0.1 0.1 0.295410478 -0.1 -0.1 0.194631072 -0.1 -0.3 0.107746763 -0.1 -0.5 0.066735532 The plot looks good, but does not affect the temperature. If I change the power - the temperature does not change. Tell me, please, what can I change in the model?</p> Mon, 18 Mar 2019 15:19:40 +0000 4.2019-03-18 15:19:40.230091 Comparing Two Files (resolved) https://www.comsol.com/forum/thread/230081/comparing-two-files-resolved?last=2019-03-18T14:03:01Z <p>Hi,</p> <p>I've created a file according to a turorial, but I got some errors when I have it try computing the results. I can't see why the error occurs (it says a variable is <em>undefined</em> but it is set up jsut like in the tutorial form what I can judge).</p> <p>Is ther a way to compare two files? Either by having them open side by side, or even better, exporting them in a way where I then can write something in Excel (or similar) that marks the differences?</p> <p>Thanks in advance for any help</p> Mon, 18 Mar 2019 10:59:22 +0000 4.2019-03-18 10:59:22.230081 Drawing a group of https://www.comsol.com/forum/thread/230071/drawing-a-group-of?last=2019-03-18T10:54:22Z <p>Dear all, Hoping all of you is well. I need to draw a group of nanowire doping by N &amp; P concentrartion. How can I choose this doping? which module? Please advice.</p> Mon, 18 Mar 2019 10:54:22 +0000 4.2019-03-18 10:54:22.230071 Apply physics to each object (Application builder) https://www.comsol.com/forum/thread/230011/apply-physics-to-each-object-application-builder?last=2019-03-18T07:10:28Z <p>Hello, I'm generating a vector of circle objects programmatically (2D), this works well, but I want to apply an acceleration to each generated circle (different in each one).</p> <p>To apply the acceleration must indicate the indices of the segments of the circle, but when generating it programmatically I do not have them and they are not constant because in each execution the number of circles is changed, how can I obtain those indexes? Is there another solution?</p> <p>The example code of the loop that generates the circles and tries to apply the acceleration is the following:</p> <pre><code>// LOOP (N = input value) for (int i = 0; i &lt; N; ++i) { // BUILD CIRCLE i String tag = "cloop"+(i+1); String pos = "aCol-d/2-d*"+i; // VERTICAL POSITION model.component("comp1").geom("geom1").create(tag, "Circle"); model.component("comp1").geom("geom1").feature(tag).set("pos", new String[]{"0", pos}); model.component("comp1").geom("geom1").feature(tag).set("r", "a/2"); // ADD TO ACUMMULATIVE SELECTION FOR DIFFERENCE AFTER THE LOOP model.component("comp1").geom("geom1").feature(tag).set("contributeto", "csel1"); // GET INDEX int[] idx = Unknown(tag); // ?????? // ACCELERATION String atag = "naccloop"+(i+1); model.component("comp1").physics("acpr").create(atag, "NormalAcceleration", 1); model.component("comp1").physics("acpr").feature(atag).set("nacc", "exp(iniDist*"+i+"/c0 * j*2*pi*frecMax)"); // ACCELERATION VALUE i model.component("comp1").physics("acpr").feature(atag).selection().set(idx); // APPLY ACCEL } </code></pre> <p>Thanks!</p> Sun, 17 Mar 2019 01:28:19 +0000 4.2019-03-17 01:28:19.230011 2D Axisymmetric particle tracing https://www.comsol.com/forum/thread/230002/2d-axisymmetric-particle-tracing?last=2019-03-16T21:53:59Z <p>Hello friends,</p> <p>I'm doing 2D Axisymmetric particle tracing. I could visualize the velocity of the base fluid in 3D. But, I could not do the same for the particles. I need to see them in 3D. Anyone can help in visualizing the particles in 3D?</p> <p>Thank you</p> Sat, 16 Mar 2019 21:53:59 +0000 4.2019-03-16 21:53:59.230002 How i can design this geometry https://www.comsol.com/forum/thread/230001/how-i-can-design-this-geometry?last=2019-03-16T16:43:29Z <p>hello guys,I'm student in second year of master, option Physics and Radiations Techologies, My final project about Heating Transport and Thermomechanic of Triga Mark II Nuclear Recator, i want a method to design its geometry please help me.!! this is the fuel rod <img src="https://photos.app.goo.gl/6gXaEpxkENjeoXY56" alt="Fuel Rod of TRIGA" /> and thanks for Comsol equip.</p> Sat, 16 Mar 2019 16:43:29 +0000 4.2019-03-16 16:43:29.230001 SAW based acoustic streaming https://www.comsol.com/forum/thread/229991/saw-based-acoustic-streaming?last=2019-03-16T16:03:16Z <p>Dear all,</p> <p>I would like to model acoustic streaming in a microfluidic channel without having the need for modeling the IDT generating the SAW. Is this possible? And how can these running SAW waves be introduced in COMSOL without the IDT? And with which modules can the link with the fluidics be achieved so that part of the energy of the SAW is coupled to the liquid with acoustic streaming as a result?</p> <p>Kind regards, Jorik</p> Sat, 16 Mar 2019 16:02:53 +0000 4.2019-03-16 16:02:53.229991 How to use moving mesh? https://www.comsol.com/forum/thread/229983/how-to-use-moving-mesh?last=2019-03-16T13:16:12Z <p>Hi there i am using comsol 5.2. I have a geometry in which two ring magnets are used. I want to find the force on upper ring magnet. i also want to move the magnet at a distance of 1m, for which i want to use moving mesh. can someone help me in that.</p> Sat, 16 Mar 2019 13:16:12 +0000 4.2019-03-16 13:16:12.229983 Submarine cable model https://www.comsol.com/forum/thread/229973/submarine-cable-model?last=2019-03-16T10:22:05Z <p>Hello! Cable losses in official submarine cables follow the law of conservation of energy, that is, the sum of core loss plus metal sheath loss plus armor loss is equal to three times the square of core current multiplied by core AC resistance. In IEC standard, cable core loss is the square of core current multiplied by core AC resistance. These two are contradictory. How do you understand them? Thank you</p> Sat, 16 Mar 2019 10:21:37 +0000 4.2019-03-16 10:21:37.229973 There is no domains in my model when I delete some undesirable surface.Thanks for any help! https://www.comsol.com/forum/thread/229963/there-is-no-domains-in-my-model-when-i-delete-some-undesirable-surface-thanks-fo?last=2019-03-16T07:26:40Z <p>I want to delete a circle in a cylinder.So I do a boolean operation between two cylinders,and deletes some face between them.But after that,there is no domains in my model.</p> Sat, 16 Mar 2019 07:26:40 +0000 4.2019-03-16 07:26:40.229963 Error with multi turn coil https://www.comsol.com/forum/thread/229961/error-with-multi-turn-coil?last=2019-03-16T05:45:21Z <p>Could not determine the center of the circular coil.</p> <p>Getting this error when i try to build 3d multi turn coil with ferrite bar</p> <p>Please help me to resolve this https://ibb.co/r381CtY</p> Sat, 16 Mar 2019 05:44:31 +0000 4.2019-03-16 05:44:31.229961 How can I avoid electromagnetic waves entering from the sides? https://www.comsol.com/forum/thread/229951/how-can-i-avoid-electromagnetic-waves-entering-from-the-sides?last=2019-03-15T21:39:03Z <p>Hello to all</p> <p>I'm failing in simulating the fresnel equations in 2D as a small exercise with Comsol.</p> <p>As you can see in the model added to this post, the reflectance and transmission in the global plots both for TE-waves ("Port, senkrecht polarisiert", Plot "Reflektion und Transimission, senkrecht") and TM-waves ("Port, paralell poralisiert", Plot "Reflektion und Transmission, paralell") seems to be correct for small angles of alpha. But for bigger angles of alpha, the simulated values differ strongly from the analytical solutions. I suspect that the wave from the upper port is also entering from the sides of the dielectica (side 1 and 6), since we have also an electrical field in the dielectrica for alpha equals 90 degrees. How can I avoid the electromagnetic wave entering from the sides 1 and 6?</p> <p>I would be very happy about every help in this problem! Best wishes M.Stucki</p> Fri, 15 Mar 2019 21:39:03 +0000 4.2019-03-15 21:39:03.229951 Thermal Expansion https://www.comsol.com/forum/thread/229943/thermal-expansion?last=2019-03-15T21:10:38Z <pre><code>The below post is related to an [archived discussion](/forum/thread/39909/adding-thermal-expansion) </code></pre> <hr /> <p>[start here]I have COMSOL 5.2 and am using the Structural Mechanics Module for the Physics. There is no Thermal Expansion options under the Linear Elastic Material as described in the Thermal Loaded Beam example. Has this been removed form 5.2?</p> <p>Any ideas?</p> <p>Thanks Alan</p> Fri, 15 Mar 2019 21:10:38 +0000 4.2019-03-15 21:10:38.229943 Error while plotting a Cut point 3D https://www.comsol.com/forum/thread/229931/error-while-plotting-a-cut-point-3d?last=2019-03-15T14:34:34Z <p>Dear Collegues,</p> <p>I am new user of Comsol. I try to plot the temperature of a specific point (Cut point 3D in 1D plot) but an error shows up.</p> <p>"Operation cannot be performed on data set cpt2 (Cut point 3D). - Plot group: pg1 (3D plot group)</p> Fri, 15 Mar 2019 14:26:44 +0000 4.2019-03-15 14:26:44.229931 Cooling after a certain time of heating https://www.comsol.com/forum/thread/229921/cooling-after-a-certain-time-of-heating?last=2019-03-15T14:21:10Z <p>Dear Collegues,</p> <p>I have a simple model with three objects. I set up a heat source to one of those and i am interested to plot the cooling process (temperature plot) after certain time in all objects.</p> <p>I would highly appreciate if someone could help me with this.</p> Fri, 15 Mar 2019 14:13:24 +0000 4.2019-03-15 14:13:24.229921