# Comsol convergence plot error

** polyfit(x, y, 1) returns the slope and intercept. The default value is 0. For more information about. . 8 speeds the rate of convergence. Judging the convergence behavior of a simulation based on this would be a poor approach. Pioneer of Success 6,262 views 1 - Relative Tolerance is the convergence criteria value in COMSOL. So q(x,y) = (1 2ǫ Note: This discussion is about an older version of the COMSOL Multiphysics ® software. 3 to 4. 01 in COMSOL. 2a. ) Verify that the blow-up rate 1 is correct. Kind Regards Achyut Error convergence plot using nonlinear adaptive solver. To figure out the slope we can do linear regression. Giving the moving wall a velocity equal to how fast its moving throws a "nonlinear solver did not converge" error on the first timestep. See the screenshot below: Kind regards, Prasad Bhonsule For pressure and velocity under k-ε or k-ω it is typically 0. Apr 27, 2016 · The convergence plot confirms that the initially sluggish convergence changes to a quick convergence in just a few iterations once the large residual has disappeared. 3a, Version 4. You can solve a least square problem as in HW4&5, but here we use a shortcut as described in this example. 0 radius) corners, at a contact, or on geometry where at a constraint. Thus, COMSOL Multiphysics has calculated the stationary solution. If this occurs in your stress analysis, you may consider changing the "Results to Converge" setting in the Convergence Settings. e, Xn vs n. 4 • Convergence Speed • Examples –Secant Method 2. To save the plot, choose the camera and follow the The solution is to employ an iterative computational technique in Inventor Stress Analysis called convergence. You can fix this by pressing 'F12' on your keyboard, Selecting 'Document Mode' and choosing 'standards' (or the latest version listed if standards is not an option). 17-7 The default plot generated is the following velocity magnitude contour. (For example: 4. Based on your location, we recommend that you select: . To help combat this problem, COMSOL Multiphysics has nine built-in size parameter sets when meshing. comsol. Load a model made in a later version of Comsol into an earlier version. Mar 27, 2017 · Convergence: Mesh convergence determines how many elements are required in a model to ensure that the results of an analysis are not affected by changing the size of the mesh. To enable software rendering on Windows: 1. × Warning Your internet explorer is in compatibility mode and may not be displaying the website correctly. It is important to note that in the limit ∆t → 0, the last Numerical Analysis Math 465/565 Order and Rates of Convergence 1 Saturday, September 14, 13 One can look at the convergence plot of the solver and see the relative error. Use a solution with high accuracy and plot jrVjalong a line shooting out from the corner. The concept of norm is used here to have a scalar measure of the relative size of the entries of a matrix, usually for the comparison of convergence errors after different numbers of steps of a particular algorithm. Given Xn = x, the proposal distribution is the uniform distribution on [x−ǫ,x+ǫ], where ǫ is a parameter. It worked well when there is only bioheat physics, but when i use bioheat+moving mesh physics i reach this error. Note that while COMSOL employees may participate in the discussion forum, COMSOL ® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team. R Dr. In this case your convergence plot in comsol should show a decreasing curve at the end of your calculation. Jan 15, 2017 · important for those who are new in using COMSOL Sep 13, 2012 · A number of peop le are getting similar issues relating to COMSOL not converging. What I'm seeing is that the goal never converges but oscillates within a reasonable range. e Fl1/1000 or even 1000 times less ;)-- Convergence plots Posted 13 dic 2013, 07:28 GMT-8 Interfacing, LiveLink for MATLAB, Results & Visualization, Studies & Solvers Version 4. 2020 г. Effects of Solvers on Finite Element Analysis in COMSOL MULTIPHYSICS® Chethan Ravi B. Hi I have noticed sometimes when you have done many changes and tests, COMSOL does no longer update the solver settings accordingly, this happens particularly when you change many things in the solver sequence, which COMSOL does not understand, and decides that you want to control the solver in detail, so it does no longer update everything. This can be a difficult subject to discuss because it isn’t formally possible to guarantee convergence for any but the simplest models, and therefore any argument that you make will be The COMSOL discussion forum covers a wide variety of simulation topics. Of these series, Oct 18, 2012 · In part I if this series, we saw how to use Newton-Raphson residual plots as an aid to vanquishing convergence difficulties in ANSYS Workbench Mechanical. gif https://www. theoretical convergence than smoothing. 8910 Both bisection and the ﬁxed point method are linear methods Again, we can write log(e k+1)=↵ log(e k)+log(µ) Saturday, September 14, 13 The following new products are introduced with COMSOL Multiphysics version 4. Eagerly waiting for your solution. It is important to remember that your solution is the numerical solution to the problem that you posed by defining your mesh and boundary conditions. I am currently experimenting on optimizing its rate of convergence. Since the value of 'n' represents the stage within Newton's method, it may make more sense to plot it as the x-value. 4 Since it is now possible to measure the error, a simple numerical example will be considered to show the FEM‘s convergence. ) it needs. Our ndings suggest that it saves time to use more than one thread, with the most improvement from one to two threads, which is expected on a cluster node with two dual-core processors (as opposed to one quad-core processor, 1 Excerpt from the Proceedings of the COMSOL Conference 2009 Boston As for plotting the convergence, using plot is typically the function to use when plotting a 2D line (which will show your convergence). Since the starting capillary for all the simulations is One of my goals is measuring the force on the face of a valve after the first restriction. Ideally, the error should go down monotonically if it does converge, then start investigating ramping the loads, the nonlinearities, or the multiphysics couplings. For an example problem: unable to plot centerline velocity × Warning Your internet explorer is in compatibility mode and may not be displaying the website correctly. Error Estimates in the Convergence Plot for Nonlinear Solvers You can now get a log and plot of error estimates per field and state during the solution for applicable multiphysics models if you select Detailed from the Solver log list in the Advanced node’s Settings window. 4 . Sep 11, 2018 · In the plot above, step 1 needed the substeps to converge, but step 2 has a Minimum Substeps that is larger than required. ME 582 – Handout 17 –COMSOL Tutorial 4. Monitoring integrated quantities such as force, drag, or average temperature can help the user judge when his or her analysis has reached this point. As it is After the analysis is finished, display the convergence information by clicking the Convergence Plot tab on the Output Bar. 4 –Heron’s formula –Stop criteria –General method 2. The purpose is to check the convergence of the algorithm. br@siemens. 3, Version 4. com Excerpt from the Proceedings of the 2014 COMSOL Conference in Bangalore Select a Web Site. Click on the Title to change it to Velocity for Newtonian Fluid and click the plot icon to redo the plot. However, it does seem to make the iterator a bit less stable: the convergence plot begins to exhibit a bit more jagged appearance. 1 Introduction the appearance of the solution plot and computing the FEM error by domain integration. LAB script le for numerical convergence studies are available in [1]. To change the axis labels and title, select the 1D Plot Group Node and click the x-axis and y-axis labels and change them to radius (m) and velocity (m/s). This behavior is consistent with the fact that perturbations and errors evolve according to the approximated equation — in this case, an approximation of time-dependent, convection-dominated flow equations. Mesh Convergence problem in modelling × Warning Your internet explorer is in compatibility mode and may not be displaying the website correctly. ? Question. It would be really great if someone helps me to find out the right solution. I tried to replicate your results, but I found that higher order finite differences were actually more accurate (based on RMS error) even in this example. This post provides an overview of a phenomenon called “Super Convergence” where we can train a deep neural network in order of magnitude faster compared to conventional training methods. It follows that the current density blows up as jJj= SjrVj˘r 1; when we approach the corner. In addition, I have modified the marker from '. velocity at wall is zero even though wall is moving), the solver eventually throws the same error, though later in the simulation. e. Meshing with COMSOL Multiphysics 4. 2). When I use the direct solver, it It seems that the problem of loss of convergence is caused by a too large displacement of the mesh. To summarize, our convergence statement says that in the limit ∆t → 0, the numerical solution collapses onto the exact solution and the error goes to zero at all time indices. (5) may either require large N, leading to considerable round-off errors, or may not converge at all, [11-13]. Convergence plots Posted Dec 13, 2013, 7:28 AM PST Interfacing, LiveLink for MATLAB, Results & Visualization, Studies & Solvers Version 4. 28) is greater than the relative tolerance. Can someone explain to me what exactly the COMSOL convergence plots are showing me? How do I interpret that information? I am working with COMSOL 5. You may also want to include drawnow (and perhaps a suitable pause) after each plot so that the figure is immediately updated. 3a • Use for convergence studies or to verify whether • Mesh plot to aid in creating good quality meshes Sep 16, 2010 · I am running a frequency study on an assembly and the frequency study is taking a much longer time than usual. Step 10b. Autocorrelation analysis & convergence¶ In this tutorial, we will discuss a method for convincing yourself that your chains are sufficiently converged. >> ab = polyfit(log(e(1:end-1)),log(e(2:end)),1) ab = 0. You can use the residual operator, new with COMSOL Multiphysics version 5. This leads to an error message that might look like: Failed to find a solution. Dec 23, 2013 · When solving such a problem, you will get a Convergence Plot, which shows the error estimate decreasing between Newton-Raphson iterations. I'm not sure about the validity of this trend, I mean is it normal that the force convergence starts already below the force convergence criterion? Re: Inventor 2018 FEA Convergence plot not working Please feel free to share your model or some screenshots so that we can have a better idea of what you're experiencing. Convergence is something that all CFD Engineers talk about, but we must remember that the way we generally define convergence (by looking at Residual values) is only a small part of ensuring that we have a valid solution. System response (stress, deformation) will converge to a repeatable solution with decreasing element size. Browse the threads and share your ideas with the COMSOL community. How to draw mesh convergence plot in COMSOL so that I can check at what element size my result converges? Can anyone help with this comsol error?: Undefined variable. The convergence for the higher capillary number is smoother than the lower capillary number all solutions converge to maximum normal velocities less than 10-3. I want to set up a parameter estimation study comparing normed values (my experimental data is all set) but to get the set of normed values in Comsol I need to divide the data set over the time by the maximum value of the set, to only obtain values between 0 and 1 l, if that makes sense so far. The telltale is the information on Response Frequency and Period (the example shown is a static structural solution). Since it is now possible to measure the error, a simple numerical example will be considered to show the FEM‘s convergence. 4 • Convergence and efficiency • Examples –Multiple roots 2. The information provided may be out of date. I am not able to infer from this graph whether my solution has converged or not. Venkateswaran P Corporate Technology - Research and Technology Center Siemens Technology and Services Private Limited Bangalore-560100 Chethanravi. But even with this the convergence plots are swinging greatly between 2 values as if there is a BC missing (no unique solution), it converges though if I use the new "Double Dogleg" solver but the results are not satisfactory, there is no force from the ES To figure out the slope we can do linear regression. Here, we will examine techniques for accelerating the convergence of these two methods. Ways to improve convergence in Comsol Multiphysics? I would greatly appreciate some advice on improving the convergence of my fluid dynamics Heat transfer model of a pipe which I have developed in Read 12 answers by scientists with 15 recommendations from their colleagues to the question asked by Md Badriadib Aldrin Suhaini on Mar 17, 2016 For example, I needed to generate a hexagonal network of hundreds of edges, and there was no easy way to accomplish this from within Comsol. 7. Help with Comsol NACA project Please I'm in need of some help with trying to run a NACA simulation for a class project. Set the start and end coordinates of the line as follows. Hello CFD Community, I am experience some convergence problems and that's why want to observe user variables in my simulation. At first In this case your convergence plot in comsol should show a decreasing curve at the end of your calculation. Ensure that the x axis of this plot shows some indication of mesh density in the area of interest - number of elements on a The plot appears automatically. In class we did the Comsol tutorial "Flow Around an Inclined NACA 0012 Airfoil" where we made a whole model and generated plots. ments are needed to obtain 1% error? 5. What we want is to produce three plots, each dof versus l2_err, in a loglog plot. Discussion Closed This discussion was created more than 6 months ago and has been closed. comsol -3drend ogl (start with OpenGL rendering) comsol -3drend dx9 (start with DirectX rendering) comsol -3drend sw (start with software rendering) Note that DirectX is only available on Windows. In our previous blog entry, we introduced the Fully Coupled and the Segregated algorithms used for solving steady-state multiphysics problems in COMSOL. Kind regards, Prasad Bhonsule By default, the Continuation Method will be used, which uses the solution from the previously solved step as the initial condition for the next step, thereby easing convergence. nonlinear control outputs include the force convergence 0,5%tolerance and 1e-2 N minimum reference. Here, we’ll discuss size parameters for free tetrahedral meshing. I know there are many posts about residuals and convergence, sorry to bring up another one I am using a k-omega model and this is what my residual plot looks like: I am not very experienced with Fluent, I just finished the Cornell series "A hands-on introduction to engineering simulations" and I guess I still need more practice. ) describe the conservation of fundamental fluid-quantities and the discretization method is the Finite Volume Method, the residuals are a measure for the imbalance of a fluid-quantity in a finite volume Mar 06, 2016 · Hi Willem, the convergence plot when you are using the FFEPlus solver is actually of no use to typical users, it plots the convergence of some parameters that are internal to the solver. All of the solution methods mentioned in the plot are available in COMSOL Multiphysics. This implies that the solution has reached steady-state. In order to determine the convergence order from numerical runs, the errors of runs with different refinement level have to be related. Increasing this to 0. 1. Ideally, the error should go down monotonically if it does converge, then start 15 Jan 2017 Your browser does not currently recognize any of the video formats available. convergence error for obtaining the solution of implemented model is compared Error convergence plot using geometric multigrid linear solver. Type of error shown in convergence plots × Warning Your internet explorer is in compatibility mode and may not be displaying the website correctly. 3b, Version 4. 3 Solving a Real Use Case: Scientific Data Analysis”. hello, I keep getting convergence problems when doing a simulation using comsol multiphysics. Posted 9 мар. domain plot in 4. Lastly in Section 3. The numerical solvers within COMSOL Multiphysics expect some degree of smoothness to the solution, so solving such models is inherently challenging. The code is from the PGFPlots 1. Best regards, But even with this the convergence plots are swinging greatly between 2 values as if there is a BC missing (no unique solution), it converges though if I use the new "Double Dogleg" solver but the results are not satisfactory, there is no force from the ES the convergence of our MCMC is a plot of the evolution of the chain, i. Sarah - as the bisection method is a root finding algorithm, I suspect that what you want to plot (from each iteration of the while loop) is either c or f(c) as you would want to show convergence to either the the root, c, or zero. The simulation is running very well for a single wavelength (convergence plot shows a proper graph). But surprisingly when I use a parametric range of wavelength, it is not running (does not show proper convergence graph). The figure above shows a bar of length 2l with Young‘s Modulus E = 10 4 Nm ‐2 and cross‐ The NDN Hub is the online community center for Canada's National Design Network I've played around with my mesh size and timestep (which comsol should also automatically adapt) but I always run into this weird pattern and non-convergence. By default each new plot replaces the previous one. System response (stress, deformation) will converge to a repeatable solution with decreasing element size . Using Results as Material Parameters - Convergence. In addition, a convergence indicator gives the estimation for -2 x log-likelihood along the iterations. I am using a pressure driven flow and I am using "parametric solver" which increases the input pressure by 10,000 Pa (10kPa) at each step. If our study involves solving multiple equations, the value given here will be taken as default for all the equations. Below is an example of Divergent results for a Von Mises Stress Convergence Plot. However, the solid was not truly rigid as the FSI module does not offer the Structural Mechanics choice of making the solid a rigid domain. Right-click on the COMSOL Multiphysics shortcut and select Properties. But somehow after passing a certain limit it gives this convergence Convergence plots use graphics to show how an error estimate or time step evolves during the solution process for nonlinear, time-dependent, and parametric solvers. Changing the Solution Output to the Solver Output will show the explicit scheme being used in that case. e Fl1/1000 or even 1000 times less ;) Apr 27, 2016 · The convergence plot confirms that the initially sluggish convergence changes to a quick convergence in just a few iterations once the large residual has disappeared. 5 and 0. The COMSOL discussion forum covers a wide variety of simulation topics. So q(x,y) = (1 2ǫ Convergence plots use graphics to show how an error estimate or time step evolves during the solution process for nonlinear, time-dependent, and parametric solvers. Achieving convergence for multiphysics problems • Set up the coupled problem and try solving it with a direct solver • If it is not converging: – Check initial conditions – Ramp the loads up – Ramp up the non-linear effects – Make sure that the problem is well posed (this can be very difficult!) In order to view the plot, either provide a line specification to draw point markers or use the 'sqrtaminus1' value to draw a line from the previous value to the newly calculated value of 'sqrta'. This is useful if Mar 06, 2016 · However, the particular convergence plot that Willem is inquiring about (when using the FFEPlus solver) is actually of no use to users, and that's not coming from me, that's coming directly from the SolidWorks Knowledge Base. I have already essentially solved this problem using COMSOL's FSI module. By making the problem time dependent, you usually get a smoother convergence. The software provides a powerful integrated desktop environment with a Model Builder where you get full overview of the model and access to all functionality. 005. INTRODUCTION. Please suggest a solution. Sep 26, 2011 · When you have convergence issues, try to get COMSOL to plot a useful value during its solving, this helps to see what is going wrong and might give a clue how to handle it you seem to get a convergence issue when the flow has fully stopped in the inlet2 if you keep a very small flow it seems to work better i. 800, Minhang, Shanghai, China, shs3701001@sjtu. edu. The COMSOL software produces reduced errors with good estimation for the linear system of equations however for nonlinear problems the accuracy of results 2. 27 Apr 2016 Troubleshoot convergence issues by plotting and evaluating your model's algebraic residual via the residual operator in COMSOL Multiphysics. For adaptive mesh refinement, it is now possible to choose on which geometric level the mesh adaptation will be TABLE OF CONTENTS. 3 • Convergence • Examples –Newton-Raphson’sMethod 2. The algorithm stops when these sequences remain in an interval of a given amplitude for … Dec 02, 2018 · Super-Convergence: Very Fast Training of Neural Networks Using Large Learning Rates. Structural contact modeling is a highly non-linear problem. Click here to visit our frequently asked questions about HTML5 video. 1 × Warning Your internet explorer is in compatibility mode and may not be displaying the website correctly. com Excerpt from the Proceedings of the 2014 COMSOL Conference in Bangalore 2 ( ) l x AE c dx du. We want to generate samples of a standard normal. The following picture represents the force convergence plot after hours of simulation. You should perhaps add that the convergence "efficiency" (or time to converge) of segregated solver cases will often depend of the order of the variables in the different segregated steps, and that COMSOL uses (from my understanding) a rule also based on the order of appearance of the different physics. 2. Estimating order of convergence 12 and use a best-ﬁt-line approach to ﬁnding ↵, given a sequence of errors e k. Make sure to solve the problem for large enough times, such that the solution does not vary any longer. Stress Singularities are typically found in re-entrant or sharp (0. Press Plot to see the line. Example: We return to an example we considered when we looked at Metropolis-Hasting. Since the governing equations (NS, continuity etc. If you haven't learned this function in class, then you may want to consult with your professor to find out an alternative way to plot data and to confirm which data you should be plotting. 9885 -0. 2. ) You don't need to know Java in order to work with a Comsol-generated Java file. Convergence plot × Warning Your internet explorer is in compatibility mode and may not be displaying the website correctly. You only need hold on so that each plot is added to the previous ones. εex x. I need results for this simulation by the beginning of next week. Tips & Tricks: Convergence and Mesh Independence Study The previous posts have discussed the meshing requirements that we need to pay attention to for a valid result. 0909 Can COMSOL Multiphysics be used for TEM mode analysis 1001 Running COMSOL in parallel on clusters 0913 Computing Time and Space Integrals 0103 Convergence problems at high reaction rates (large source terms) 0107 Command line associative geometry 0114 Plot of contour lines on different surface plots in 2D and 3D 0120 Meshing a thin geometry. The interpretation is qualitatively correct. COMSOL Multiphysics is a powerful interactive environment for modeling and solving all kinds of scientific and engineering problems. About COMSOL Multiphysics. ' to 'o' for better visibility. To solve the model problem, start the GUI of COMSOL Multiphysics, by typing comsol at the Linux prompt, which is shorthand for comsol multiphysics. Several Plot windows can be used to show multiple results simultaneously. Sep 13, 2012 · Use the time dependent solver. See Particle Aug 12, 2009 · Hello, I'm a 2nd year student, and I'm trying to get to know COMSOL. The velocity plot makes it look like the flow after the first restriction is turbulent and dancing on the valve face. It is the one that converges faster. 3, we comparing the performance of iterative solvers used in COMSOL Multiphysics software. I am attaching a picture of the same. com/shared/images/logos/comsol_logo. pdf In addition to the Graphics window, Plot windows are used for visualizing results. a norm, and h the typical element size. The COMSOL software produces reduced errors with good estimation for the linear system of equations however for nonlinear problems the accuracy of results Re-solving with a tighter relative tolerance will lead the solver to take smaller time steps initially, but there will be less accumulated error, so the solver may not need to reduce the time step to overcome accumulated errors at later time steps. At first I just plotted pressure loss, which worked fine, but now additionally I want to plot average inlet velocity and mass flow. the flow accelerates as it goes over the cylinder, as expected. Tishreen university,Lattakia, Syria,COMSOL, photonic crystal fiber PML calculate confinement loss - Duration: 3:04. Thanks, in principle there are many reasons why a computation does not converge. 4 3 Replies Tony Peyton Nov 08, 2013 · It is a simple 2D Heat transfer problem. I haven't used COMSOL, but there is no reason that a simulation will use more memory than it needs to just store a few timesteps worth of DOFs and whatever intermediate working sets (sparse linear equation matrices, Krylov space vectors, etc. Oct 09, 2019 · The most obvious is probably that the force convergence plot will stop updating. If you plot the mesh (right-click a surface plot on the model tree and then choose mesh) you'll see that you have mesh elements in the central part of your domain that are streched to the point of being inverted Type of error shown in convergence plots × Warning Your internet explorer is in compatibility mode and may not be displaying the website correctly. † Select Help>Documentation ( ) or Help>Dynamic Help ()from the main menu and then either enter a search term or look under a specific module in the documentation tree. PLOT EXPRESSIONS AND RESULTS INTERPRETATION analyzes errors in the solution and refines the mesh accordingly. Basically, I simply want to take a solution from COMSOL, import it into MATLAB and plot the solution on the mesh within MATLAB. Close to the corner (3) is a good approximation of the solution. Weak Form & LiveLink for MATLAB Based Modified Uzawa Method for Solving Steady Navier-Stokes Equation . I'm starting off by solving simple problems with the incompressible Navier-Stokes model, but I keep having trouble with the convegence of the solution. It is about water flowing through an orifice. The primary criteria for determining convergence is that the change of each degree of freedom is minimized over a large range of iterations. Example In the following example, the parameters of a one-compartment model with first-order Purpose This plot displays the sequence of estimates for the conditional means and the conditional standard deviations along the iterations of the MH algorithm during individual parameters estimation by MCMC. Note that linear and quadratic convergence are with respect to the worst case, the situation in a particular algorithm can be better than what you get from the worst case analysis given by Wolfgang Bangerth, though the qualitative situation usually corresponds to this analysis. Press J to jump to the feed. A plot highlighting the increasing performance rate of solution methods (solid) and hardware (dashed) as compared to time. com/contact to submit general inquiries, contact Technical Support, or search for an address and phone Hi, I am still fairly new to Comsol and have a question I could not find answered anywhere else. The relative residual (0. 1-2. 2, to evaluate and plot your model's algebraic residual in The quadrature error made by using numerical methods to approximate the finite element integrals. I also did this simulation in a little larger scale (in mm's) and it worked fine, now I reduced my dimensions into the micro scale but this problem started occurring. Kind Error convergence plot using nonlinear adaptive solver. 23 Sep 2010 Key words: Poisson equation, a priori error estimate, convergence study, mesh refinement. Choose a web site to get translated content where available and see local events and offers. Each iteration modifies the mesh, re-runs the simulation, and compares the results to the previous results. To plot something along this line right click Results and select 1D Plot Group. Jun 26, 2012 · OK I didnt cat it then, in 2D COMSOL is by default in the cartesian coordinates (x,y) but you can easily set up a cylindrical coordinate (r, theta) with coresponds to r=sqrt((x-x0)^2+(y-Y0)^2) and theta = atan2(y,x). That is, a tighter relative tolerance can lead to faster overall convergence. Abstract: COMSOL Multiphysics can solve a truncated version of Eq. It has been like this for several hours, and the progress value is at 2% without increasing. Even when run with no velocity disturbances anywhere (i. Troubleshoot convergence issues by plotting and evaluating your model's algebraic residual via the residual operator in COMSOL Multiphysics. The values associated with each refinement. Were you using one sided differences? Here's my matlab script if you want to mess with it. Mar 09, 2014 · multiphysics coupling,step size, convergence plot etc in COMSOL - Duration: 13:26. The number of increments may need to quite large, and you will want to monitor at what values of the ramping factor there is slow convergence of the solver. Purpose This plot displays the sequence of estimates for population parameters computed after each iteration of the SAEM algorithm. elements in COMSOL. 4 0 Replies Let’s create a line along the =5 line and plot the variation of pressure and velocity component along it. We expect that the result is a line in a loglog plot, and we are interested in its slope log e(N) = -a log(N) because that characterizes our experiment. A special case is the Convergence Plot window, an automatically generated Plot window that displays a graphical indication of the convergence of the solution process while a model is running. Plot the results to graphically verify convergence. Share. Convergence problem in time dependent solver × Warning Your internet explorer is in compatibility mode and may not be displaying the website correctly. Right click Data Sets under Results and select Cut Line 2D. Mesh Adaptation Improvements. Introduction to Numerical Analysis for Engineers • Roots of Non-linear Equations 2. Inlet speed is set as 40 and above and below the cylinder we see values higher than this, i. (With Line plot under Cross-section Plot Parameters. Note: This discussion is about an older version of the COMSOL Multiphysics ® software. By clicking on the convergence plot, I found that it is taking approximately 2000 iterations before reaching a stopping threshold. When I look at the Convergence Plot 2, which is "Reciprocal of step size" vs "Time step", I can see the reciprocal of step size is between 10^5 and 10^6. , 1:28 GMT-7 General, Electrochemical Engineering, Parameters, Variables, & Functions Version 5. The issue I am facing is that my convergence plot is a semi-log plot showing reciprocal of time-step v/s time step, even though I have fixed the time step. Fig. Apr 03, 2016 · how can plot the region of convergence?. You can Use the Generalized Alpha rather than BDF with strict or intermediate time stepping ~ this improves the convergence in many cases for me; Play with the tolerances (relative and absolute both) ~ sometimes if I change from factor to manual 23 Dec 2013 When solving such a problem, you will get a Convergence Plot, which shows the error estimate decreasing between Newton-Raphson iterations. You can just increase the number of steps and see if convergence improves. Huashan Sheng*1，Shuai Zhu1. cn. Learn more about plot, region of convergence, circle Order of Convergence Richardson Extrapolation Log-Log charts January 19, 2006 1 Order of convergence The following two series can be used to calculate π: π2 6 = X∞ n=1 1 n2 (1) π2 −8 16 = X∞ n=1 1 (2n+1)2 (2n−1)2 (2) but which series is better. I often set Minimum Substeps to a large number to get a smooth curve of the history from step 1 to step 2, but if all you were interested in was the result at step 2, the plot shows you to try a larger Initial and larger Minimum number of substeps in step 2 to get to the final result. To locate and search all the documentation, in COMSOL Multiphysics: † Press F1 for Dynamic Help, † Click the buttons on the toolbar, or. The Convergence Plot command displays the plot within a dialog box. but for some reason COMSOL only uses about 3GB of RAM when running the analysis. Include playlist. I keep getting the following error: "Failed to find a solution: The Apr 11, 2019 · I was expecting a convergence error, but was surprised, that I didn't get one. Performing a convergence study in Inventor Stress Analysis refines the mesh and reduces the size of the elements, Effects of Solvers on Finite Element Analysis in COMSOL MULTIPHYSICS® Chethan Ravi B. The plot shows: The number of refinements required for the solution to converge, if convergence is achieved, or the number of solution steps requested for the required refinements. The question is, why didn't I get an error? Can I trust the results? Or should I get sceptical about my results, when seeing this plot? And - maybe a bit general - What is the reason for oscillation in the force convergence plot? the convergence of our MCMC is a plot of the evolution of the chain, i. In order to get rid of the error message one can reduce the relative tolerance in the Solver Settings. If the data is confidential, you can also direct message me to share. Basel Haji 11,028 views When solving such a problem, you will get a Convergence Plot, which shows the error estimate decreasing between Newton-Raphson iterations. Determination of Convergence Order The convergence order ϑ is defined by the relationship e O h= (ϑ) (1) where e denotes the error, . No. com/forum/ CFD Convergence using Quantities of Interest In a steady state analysis, the solution field should not change iteration to iteration for an analysis to be deemed converged. 4 3 Replies Tony Peyton When solving such a problem, you will get a Convergence Plot, which shows the error estimate decreasing between Newton-Raphson iterations. I have not found any discussion on this topic yet and I am having difficulty finding anyone in COMSOL support in North America that can help with this problem today. 1 Department of Mathematics Shanghai Jiao Tong University * Dongchuan Rd. One possibility is, that you solver just needs some more steps. Press question mark to learn the rest of the keyboard shortcuts Sep 26, 2011 · When you have convergence issues, try to get COMSOL to plot a useful value during its solving, this helps to see what is going wrong and might give a clue how to handle it you seem to get a convergence issue when the flow has fully stopped in the inlet2 if you keep a very small flow it seems to work better i. https://www. The figure above shows a bar of length 2l with Young‘s Modulus E = 104 Nm‐2 and cross‐ sectional area A = 1 m². An error occurred while retrieving sharing information type The new convergence plot type displaying error estimates for each dependent (field) variable. 10 manual: “3. 2: • Particle Tracing Module: A new module for simulation of particle trajectories with specialized interfaces and plot types for particle tracing of charged particles in electric fields, mass particles in fluid flow, optical rays, and more. Why doesn't iterative solver converge in COMSOL? I have a multiphysics problem in COMSOL involving the laplace equation, navier stokes equations and heat transfer. As surfaces come in and out of contact, load paths and stress states will abruptly change. Jan 30, 2014 · However, no one wants to be bogged down figuring out the exact specifications for their mesh. Convergence problem in modelling × Warning Your internet explorer is in compatibility mode and may not be displaying the website correctly. I want to simulate a rigid body in a creeping flow liquid using COMSOL (5. In the Model Navigator for the problem dimension select 2D, then select COMSOL Multiphysics !PDE Modes !PDE, Contact Information Visit the Contact COMSOL page at www. In part II, we will see how to quickly launch the ANSYS Mechanical APDL user interface to plot elements that have undergone too much distortion, thereby resulting in a convergence failure. normal velocity convergence plots for capillary numbers of 0. comsol convergence plot error
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