This seems like a common errorfailure when running simulations for long time ranges. The most popular versions among comsol multiphysics users are 4. If you are primarily observing that the tfail column in the solver log is being incremented often, enable the nonlinear controller within the time stepping settings as shown in the screenshot below. Most electromagnetic components, devices, and products are affected by another branch of physics, whether it be heat transfer, structural mechanics, or acoustics, to name a few. Alternativeto is a free service that helps you find better alternatives to the products you love and hate. This operator allows you to evaluate quantities at the previous time step when using the default implicit time stepping algorithm. Initial step size and maximal step size influence the behavior of. Use the time discrete solver feature to find the solution to timedependent problems which have already been discretized in time using for example the prev operator or the bdf operator. The comsol software automatically formulates the energy equation coupled to the momentum and mass balance equations for ideal gases. Apr 28, 2011 hi the time stepper often starts with small steps, as often we are lazy and leave 0 as initial conditions, but true current, or heat flux starting far away from 0 so the system believes its facing a large derivative at the beginning of the transient solver sequence, hence small steps. The times specified in the times field in the general section are not considered when a time step is chosen. Improving convergence of transient models comsol multiphysics. Comparison of six simulation codes for positive streamers in air.
But it says that the file is either corrupt or not valid. It allows conventional physicsbased user interfaces and coupled systems of partial differential equations pdes. Automatic time step and order selection in timedependent. Asynchronous machine time dependent startup, singularity error. Comsol multiphysics 3 new additional timedependent solutions operators that you can use for results evaluation, for example. If you are stopping often, say for event handling, this will heavily impair the efficiency of the codes. Does anyone have a solution for a singularity error in. I am looking for a free not only as in freedom alternative to comsol multiphysics. Nonlinear solver did not converge in comsol multiphysics.
For the time stepping, we used the backward difference formula bdf, configuring it to allow orders 25 and flexible time step sizes. To request a demonstration, simply fill out the form on this page. The implicit backward differentiation formula bdf, generalized alpha methods, and the explicit rungekutta family of. You need the license manager to run the comsol multiphysics software using the fnl, ckl, or comsol server license types. This research aims to achieving the effective cooling parameter on the runout table rot of strip steel in hot rolling process. Trial licenses are automatically associated with your account. Im stepping at 100 steps per cycle and am using a strict bdf time stepping method. This will enable more efficient time step control in the bdf method, especially for highly nonlinear models. Bdf, generalized alpha, and rungekutta methods comsol.
To modify how the timestepping methods select the time steps, choose an option from the steps taken by solver list. All of the features listed below are implemented through associated physics interfaces. This stepbystep instructional video will guide you through the modeling workflow, with an emphasis on structural mechanics modeling. Thats why the algorithm crashes in cases of automatic time stepping. With comsol multiphysics, you will be able to account for coupled or multiphysics phenomena. Explicit methods directly compute the solution at future states based upon the solution at the current.
Bdf methods which are autostarting have a high starting cost. Numerical integration of ordinary differential equations. For some reason the solver freaked out on the 21st cycle. For solving the unsteady navier stokes equation in a microfluidic channel on a rotating platform, i. This operator allows you to evaluate quantities at the previous time step when using the default implicit timestepping algorithm. Both 2day intensive trainings and 1day specialized classes are available. Browse solutions to common modeling questions, check for software updates, and log into comsol access to manage your active technical support cases. If you do not yet have a comsol access account, please create one now. Most time dependent problems in comsol multiphysics are by default solved with an adaptive timestepping scheme. Based on my experience on solving timedependent problems using my laptop, 1. Comsol software users who are onsubscription should submit their questions via the support center for a more comprehensive response from the technical support team. Bdf method provided by comsol for time integration was used.
We also enforced a fixed maximum time step size for all the simulations. The software will automatically determine a set of solver settings that are reasonable. Comsol provides an ide and unified workflow for electrical, mechanical, fluid, acoustics, and chemical applications. While solving the set of pf model equations, the comsol solver required extensive computational memory.
The software will automatically determine a set of solver settings that are reasonable for the combinations of physics in the model, but these can be modified. As a result, bdf in the timedependent solver controlled the. It means that i dont have any perturbation in the initial values. There is an urgent need to try and develop and implement a dualtime stepping algorithm due to the large domain sizes i work with and a vast range of different cell sizes. When inspecting the solver log of a timedependent simulation using the bdf timestepping scheme, the. The 2dimensional transient heat conduction is developed including the external force convection and heat source due to translational motion. In the time stepping node i can only set initial and maximum time steps but not the minimum time step. For problems involving diffusion, convection, and reactions which are by default solved using the bdf method with free time. On the other side, if i do the same procedure on openfoam with the icofoam solver, the results are much more better and i have unsteady flow for high reynolds number. What is numerical damping in the context of timedependent fem.
The default values are suitable for problems with time constants of order of magnitude of 0. Improving convergence of transient models knowledge base. The timedependent solver offers three different time stepping methods. The timedependent solver in the comsol multiphysics software offers three different timestepping methods. Since the explicit multistage rungekutta methods rely on the global timestep, the timestep sizes are impractically short and this leads to unfeasible computational wall.
Another way to make the solving process simpler was to be selective where the mesh was refined. This will enable more efficient timestep control in the bdf method, especially for highly nonlinear models. In comsol, how to choose time step and mesh size for the. Thats right, all the lists of alternatives are crowdsourced, and thats what makes the data. Implementation of two multiphase flow methods in modeling. Let us take a look at how this operator is implemented and then examine how it can be used for various modeling needs. Comsol requires that every type of simulation included in the package has the ability to be combined with any other. For the timestepping, we used the backward difference formula bdf, configuring it to allow orders 25 and flexible time step sizes. I want to plot the reaction force for all the stored output times, but the interpolation only takes 7 steps of the solution, although the times in my time stepping are 001. It provides a quick overview of the comsol environment with examples that show you how to use the comsol desktop user interface and the model builder. These cases are solved using an adaptive, or free time stepping scheme where the solver will adjust the time step size automatically. Hi everybody, ive got a problem with the global variables plot in a 3d thermostructural problem.
I use as initial values in the comsol time dependent solver the solution of the stationary solver. The backward differentiation formula bdf solver is an implicit solver that. As this seems like a quick fix, i wouldnt be surprised to see it fixed by the time comsol 5. Use the time discrete solver feature to find the solution to time dependent problems which have already been discretized in time using for example the prev operator or the bdf operator. For shorter time integrations, this has a very nonnegligible effect.
With more than 30 addon products to choose from, you can further expand the simulation platform with dedicated physics interfaces and tools for. You will need an onsubscription comsol license attached to your comsol access account or a software trial provided by your sales representative. The material property, boundary, and initial condition are defined and bounded to model geometry. Method steps taken by solver initial step maximum step maximum bdf order minimum bdf order event tolerance. Controlling the time dependent solver timesteps comsol. Please indicate what you would like to simulate so we may better assist you. There are three classes of methods available within comsol for solving daes. Comsol multiphysics is a crossplatform finite element analysis, solver and multiphysics simulation software. For that simulation, the time stepping was set to the order of 106 seconds. I can set a manual time step and the solver calculates the time correctly, but the timestep is always 0, too. This software was originally produced by comsol ab. List of finite element software packages wikipedia.
The process for starting the license manager is the same for both startcomsollicensemanager and comsol server. How to model structural mechanics in comsol multiphysics. Time dependent solver of unsteady navier stokes cfd online. Jun 20, 2019 let us take a look at some timestepping schemes used by the comsol software. Learn how to use comsol multiphysics and the structural mechanics module by conducting a static analysis of a mechanical structure. Using the previous solution operator in transient modeling. The bdf is a variable timestepping algorithm that allows savings in the computational time. Discussion closed this discussion was created more than 6 months ago and has been closed. In both cases, when meshing these models, automatic mesh refinement resolves the shock pattern by refining around the regions with very high velocity and pressure gradients. The bdf scheme can be selected in the time stepping section of the. Does anyone have a solution for a singularity error in comsol.
To specify the initial time step size, go to the time dependent solver settings, time stepping section, enable the initial step. Bdf vs implicit runge kutta time stepping computational. Charged particle tracing in 2d comsol multiphysics. To download the mphfiles, log in or create a comsol access account that is associated with a valid comsol license. When inspecting the solver log of a timedependent simulation using the bdf timestepping scheme, the order of the bdf scheme and time step varies. Transient modeling of an electrochemical printer using. Method steps taken by solver initial step maximum step maximum bdf order minimum bdf order event tolerance am i missing something. This might be a question better suited for the software recommendations side of s. Comsols timedependent solvers generalized alpha and bdf force smaller time excerpt from the proceedings of the 2014 comsol conference in cambridge steps than 1 s, particularly at the start time of the model when the excitation force has a noncontinuous firstderivative in time.
The most basic ones are related to the mesh resolution i. They start with a small euler step, then a small bdf 2 step, etc. Free to let the timestepping method choose time steps freely. Time dependent solver of unsteady navier stokes cfd. Yes, bdf, rungekutta rk34, cashkarp 5, dormandprince 5, and generalized alpha time stepping any user implemented andor from a set of predifined. You will need to update your comsol multiphysics license file when either the host id of a license manager or the license type changes, when transferring a license manager to a new computer, updating a trial to a paid license, or when modules change within a license. Comsol multiphysics a popular fem package includes two timestepping algorithms ida aka bdf, and generalizedalpha, described in their. The site is made by ola and markus in sweden, with a lot of help from our friends and colleagues in italy, finland, usa, colombia, philippines, france and contributors from all over the world. Eventually i figured out that one way to get the time depedent solver up and running is to set the generalizedalpha time stepping to manual. Script for clearing comsol solution data in all your mph files hint 1. For a comprehensive analysis, use the comsol multiphysics software and the acdc module to see how multiple physics affect your design.
This is the full list of what i see under time stepping node. In my problem, i want to apply pulse train as a boundary condition but i dont know how i solve my problem in transient analysis please help me in detailed steps please. Comsol multiphysics is a generalpurpose software platform, based on advanced numerical methods, for modeling and simulating physicsbased problems. Another is britz and strutwolf 38, who simulate a liquid. Dualtime stepping in 3d compressible solver cfd online. I tried downloading the file and opening it in comsol multiphysics 4. Most timedependent problems in comsol multiphysics are by default solved with an adaptive timestepping scheme. Comsol multiphysics alternatives and similar software. Certain characteristics of comsol become apparent with use. Bdf and generalized alpha are implicit methods while the rungekutta methods are explicit.
I tried doing it with bdf solver default one for weeks before blindly yes, i dont know technicalities there switching to generalizedalpha and it seemed to do the trick. The implicit backward differentiation formula bdf, generalized alpha methods, and the explicit rungekutta family of methods. When defining and solving these problems, the fluid is modeled as incompressible by default but can. Paid classes for new and current users featuring live demonstrations, handson activities, and lectures. How to update your comsol software license file for cpu. This discussion is about an older version of the comsol multiphysics software. This video tutorial explains how to set up and start the license manager. Comsol multiphysics is compatible with windows xp7810 environment, 32 and 64bit versions.
The timedependent solver in the comsol multiphysics software. Aug 31, 2016 now the last but most important thing to do is to select generalized alpha in the time stepping tab of solver settings. Generalized alpha time dependent solver comsol multiphysics. A recent work where the timedependent pnp equations are solved is soestbergen, biesheuvel and bazant 23 with fbv who used the commercial nite element software comsol, which uses bdf and the generalized method 37.
So if you had added a rectangle and then deleted it, both of these commands will. The implicit bdf and generalized alpha methods and the explicit rungekutta family of methods the backward differentiation formula bdf solver is an implicit solver that uses backward differentiation formulas with order of accuracy varying from one also know as the backward euler method to five. Comsol software users who are onsubscription should submit. Modelling of ultrasonic transducers and ultrasonic wave. Would you like to see a demonstration of the comsol software in real time.
Jun 12, 2012 it seems that the particle tracing module is quite picky about the time stepping algorithm. An adaptive timestepping algorithm in weakly coupled. It is these cases that are the focus of this knowledgebase article. Improving convergence in nonlinear time dependent models. Thank you very much for taking the time to try solving my problem. The comsol software package was used for the pf model. Cfd software for simulating fluid flow applications. Popular alternatives to comsol multiphysics for windows, linux, mac, web, gnu octave and more. In comsol, how to choose time step and mesh size for the results to be correct and accurate. The bdf method is generally the default for fem models involving diffusion, convection, and reactions and such cases represent the majority of cases that benefit from tuning of solver settings.
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