stationary solver comsol
Comsol help video number 2: Solving a laminar flow problem in a slit.. "I chose this print shop based off yelp reviews and was very happy with the outcome! For example, if there is a temperature-dependent material property such as: This involves a systematic reduction in the model complexity. Resources and documents are provided for your information only, and COMSOL makes no explicit or implied claims to their validity. At low flow speeds the flow solution will be time invariant, but at higher flow rates there will be vortex shedding, a time-varying change in the flow field behind the cylinder. Again, introduce a Global Parameter that gets ramped from exactly zero to one. It is thus always advised to start this procedure with a simplified 2D, or 2D-axisymmetric model. GCRO-DR is a method for Krylov subspace recycling. The algorithm is, generally speaking, a Newton's method approach. That is, when solving, the software starts with the user-specified initial values to evaluate all solution-dependent terms. Improving Convergence of Nonlinear Stationary Models - COMSOL When the difference in the computed solutions between successive iterations is sufficiently small, or when the residual is sufficiently small, the problem is considered converged to within the specified tolerance. Stationary in the COMSOL Multiphysics Programming Reference Manual Damped Newton Methods The nonlinear solver uses an affine invariant form of the damped Newton method as described in Ref. If all of the above approaches have been tried and you are certain that the problem itself is well-posed, consider that the nonlinear problem may not, in fact, have a stationary (time-invariant) solution. To switch between these solver types, go to the Stationary Solver node within the Study sequence. k(T,P) = 10[W/m/K]*((1-P)+P*exp(-(T-293[K])/100[K])) COMSOL makes every reasonable effort to verify the information you view on this page. Use a manually defined mesh to avoid elements with extreme aspect ratios and perform a mesh refinement study, as described here: Performing a Mesh Refinement Study, For problems that are ill-conditioned, using a direct solver is often called for. A Global Parameter has to be introduced (in the above screenshot, P) and is ramped from a value nearly zero up to one. Posted 26 set 2019, 17:57 CEST Mesh Version 5.3 0 Replies. numeric (each ports needs their ownboundary mode analysis in the study if they are numerically defined)Wave excitation: on/off(input/output), - Feature: Stationary Solver 1 (sol1/s1) Division by zero. Right-click on the Stationary Solver node and add either the Segregated or Fully Coupled feature. The former approach solves for all unknowns in the problem at once, and considers all coupling terms between all unknowns within a single iteration. As we saw previously in the blog entry on Solving Nonlinear Static Finite Element Problems, not all nonlinear problems will be solvable via the damped Newton-Raphson method. In many physics areas there exist alternative physics formulations specifically meant for solving cases where the geometry has an extreme aspect ratio. In such cases, see if one material (or the other) can be omitted from the analysis completely. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Such a large difference in the materials properties can be challenging. Sometimes, reducing the model complexity can be quite challenging and it can be better to start from as simple a case as possible and gradually increase the complexity. It may also reveal that the model itself is ill-posed in some way. Cecilia M. came from the backroom to help me and went out of her way to help me even though I had not called before going into the store. The latter method is known as the Continuation Method with a Linear predictor, and is controlled within the Study Configurations as shown in the screenshot below. If your matrix is singular than no solver in the world can solve Ax=B. Right-click on the Stationary Solver node and add either the Segregated or Fully Coupled feature. With respect to multiphysics couplings, rather than solving the problem using a fully coupled approach (the default) solve the problem sequentially, with one physics being solved after another. Perhaps this approach could be adapted to represent your model. This parameter is used within the physics interfaces to multiply one, some, or all of the applied loads. Tutti i diritti sono riservati. If this was solved using the Solid Mechanics physics interface the thin walls of the container would need to be explicitly modeled, but the wall thickness is much smaller than the overall can dimensions. In that case, the continuation method will automatically backtrack and try to solve for intermediate values in the range of 0.6 through 0.8. Then I stored the resulting solution, and used it to to solve the stationary solver again by using the solver manager. However, load ramping will not work in all cases, or may be inefficient. In this post, we will delve deeper into how to choose an appropriate mesh to start your mesh convergence studies for linear static finite element problems. Hi Jason, The finite element mesh must be fine enough to resolve the spatial variations in the solution fields. Sign in to create your job alert for Stationary Engineer jobs in Brea, California, United States. Your internet explorer is in compatibility mode and may not be displaying the website correctly. Instead, use a nonlinear material property expression that ramps from a very smooth function to a very nearly discontinuous one. Segregated approach and Direct vs. Wrong ordering of study steps. The exceptions are the Heat Transfer interfaces, which have a default Initial Value of 293.15K, or 20C, for the temperature fields. The memory requirements will always be lower than with the fully coupled approach, and the overall solution time can often be lower as well. $140,000.00, $120,000.00 The Iterative Solvers - COMSOL Multiphysics Convergence can be poor when the initial values do not provide a good starting point for this iterative approach. Resources and documents are provided for your information only, and COMSOL makes no explicit or implied claims to their validity. The technique of load ramping is not always reasonable for all problems. (I am begginer in comsol) Thank you. Use either a very fine mesh throughout the simulation domain or use adaptive mesh refinement. In particular, choosing an improper initial condition or setting up a problem without a solution will simply cause the nonlinear solver to continue iterating without converging. k(T) = 10[W/m/K]*exp(-(T-293[K])/100[K]) To switch between these solver types, go to the Stationary Solver node within the Study sequence. listed if standards is not an option). Segregated approach and Direct vs. Iterative linear solvers, About the time step setting of the solver, Introducing Goal Seeking into the Segregated Solver. This is relatively expensive to do, but will lead to the most robust convergence. Hence Comsol solved for the stationary solution at different points of time. k(T) = 10[W/m/K]*exp(-(T-293[K])/100[K]) Right-click on the Stationary Solver node and add either the Segregated or Fully Coupled feature. In a previous blog entry, we introduced meshing considerations for linear static problems. We have also introduced meshing considerations for linear static problems, as well as how to identify singularities and what to do about them when meshing. Once a simplified solvable version of the model has been found, gradually increase the model complexity again, re-introducing nonlinearities and multiphysics couplings. The Fully Coupled solution approach, with the Plot While Solving enabled. I highly recommend this flower shop. A nonlinearity can be introduced into the model either in the governing equation, or by making any of the material properties, loads, or boundary conditions dependent upon the solution. What is the purpose of non-series Shimano components? Near the top of the Stationary Solver log, the software will report if a linear or nonlinear solver is being used. Hi Alexis, Using this technique systematically, along with the techniques described previously, will usually identify the nonlinearities in the model that are leading to issues. Posted 26 set 2019, 11:57 GMT-4 Does anyone know how to solve error in stationary solver in COMSOL Despite this, the segregated approach can often converge very robustly, unless there are very strong couplings between the physics in the model. comp1.u2, comp1.v2, and comp1.w2 are usually variables associated with the x,y, and z component of deformation in COMSOL. It is sometimes necessary to manually scale the dependent variables. It is also possible to manually refine the mesh. P&S: COMSOL Design Tool for Photonic Devices - ETH Z Asking for help, clarification, or responding to other answers. Few days back i was also facing this problem in . Feature: Stationary Solver 1 (sol1/s1)" . As P is ramped up, the continuation method uses the previous solutions to compute initial conditions for the more nonlinear cases. Not meshing all the domains. COMSOL does not assume any legal liability for the accuracy of the data disclosed. The exceptions are the Heat Transfer interfaces, which have a default Initial Value of 293.15K, or 20C, for the temperature fields. It is thus always advised to start this procedure with a simplified 2D, or 2D-axisymmetric model. This information is presented in the context of a very simple 1D finite element problem, and builds upon our previous entry on Solving Linear Static Finite Element Models. The Automatic predictor setting will use the constant predictor when a segregated solution approach is being used, and use the linear predictor when the fully coupled approach is used. The stationary solver is used both for Stationary (time-invariant) and Frequency Domain (time-harmonic) study types. The difference between the phonemes /p/ and /b/ in Japanese. It is quite rare that changing these settings is superior to using a combination of the other techniques in this Knowledgebase, although it is possible to tune these settings to reduce solution time and memory requirements, once a model is already converging. However, if a lower-level change has been manually made to the solver settings, the software will not automatically use the correct default solver. For more details, see: Performing a Mesh Refinement Study, Mesh refinement may often need to be combined with load or nonlinearity ramping and may require a set of studies, first starting with a relatively coarse mesh for nonlinearity ramping, refining the mesh, and the ramping further on the refined mesh. The coupling terms between the different groups are thus neglected. Assuming a well-posed problem, the solver may converge slowly (or not at all) if the initial values are poor, if the nonlinear solver is not able to approach the solution via repeated iterations, or if the mesh is not fine enough to resolve the spatial variations in the solution. Please dont hesitate to post comments below or send emails to us if you experience any other problems. This segregated approach is used by default for most 3D multiphysics models, and the software will automatically segregate the problem into appropriate groups. Using a predictor of type Constant will take the solution from the iteration and use it as the initial value for the iteration. Your internet explorer is in compatibility mode and may not be displaying the website correctly. Repeat this for every nonlinearity of the model. $125,000.00, Project Engineer (In-person/Hybrid/Remote), $100,000.00 Thanks, Andres. If you still need help with COMSOL and have an on-subscription license, please visit our Support Center for help. Your internet explorer is in compatibility mode and may not be displaying the website correctly. Sometimes, reducing the model complexity can be quite challenging and it can be better to start from as simple a case as possible and gradually increase the complexity. Building on these topics, we will now address how to prepare your mesh for efficiently solving nonlinear finite element problems. k(T) = 10[W/m/K]+10[W/m/K]*(T>400[K]) 351 Stationary Engineer jobs in Brea, California, United States (15 new) Stationary Solver - COMSOL Multiphysics thanks for reply Have you taken a look at this blog post? Do you also know how to solve this problem: using stationary solution as the initial conditions in time dependent model, How Intuit democratizes AI development across teams through reusability. One can say that, in general, if the loads on a nonlinear system are zero, the system will be at rest; that is, the solution will be zero. As a second example, when solving for Electric Currents, do not model perfect electrical insulators as materials with zero conductivity, instead, omit the domain from the model and use the Electric Insulation boundary condition. However, it is usually not possible to know this ahead of time. At low flow speeds the flow solution will be time invariant, but at higher flow rates there will be vortex shedding, a time-varying change in the flow field behind the cylinder. The former approach solves for all unknowns in the problem at once, and considers all coupling terms between all unknowns within a single iteration. - the incident has nothing to do with me; can I use this this way? k(T) = 10[W/m/K]+10[W/m/K]*(T>400[K]) Repeat this for every nonlinearity of the model. With respect to any nonlinearities, replace them by a reasonable linearized term. If the default iterative solver is not converging, try switching to a direct solver, as described here: Understanding the Fully Coupled vs. The fully coupled and segregated approaches are discussed below. Tutti i diritti sono riservati. If both load ramping and nonlinearity ramping are still leading to slow convergence, refine the mesh. 140K views 8 years ago COMSOL Multiphysics Tutorial for Beginners Please note that an updated version of the content in this video can be found in the Modeling Workflow video in the COMSOL. In this posting, we introduce the idea of ramping the nonlinearities in the problem to improve convergence. This is useful since the software will then return an estimation of the maximum possible loadcase for which the solver can converge. Here, we will examine techniques for accelerating the convergence of these two methods. Also, keep in mind that a linear stationary model should solve regardless of how coarse the mesh is (albeit to a low accuracy) so you can always start with as coarse a mesh as possible, and refine the mesh (See also: Knowledgebase 1030: Performing a Mesh Refinement Study. I am solving a linear stationary finite element model but the software is not solving. To learn more, see our tips on writing great answers. You can fix this by pressing 'F12' on your keyboard, Selecting 'Document Mode' and choosing 'standards' (or the latest version Consult your product manuals for complete trademark details. The following are possible reasons why a linear stationary model will fail to solve, along with resolutions: The combination of the constraints and boundary conditions must be sufficient to define a unique solution to the problem, in terms of the field variables being solved. Each physics is thus solved as a standalone problem, using the solution from any previously computed steps as initial values and linearization points. The prices are good, and when I needed something delivered, same day, they were able to do it, and it looked beautiful!! It is also possible to manually refine the mesh. This approach is known as a Continuation Method with a Constant predictor. Solving for laminar flow using Comsol - YouTube Solving such models in a stationary sense should simply require solving a single (large) system of linear equations and should always be solvable, but there are cases when the software will fail to find a solution. Get notified about new Stationary Engineer jobs in Brea, California, United States. How to solve "Undefined material property 'sigma - ResearchGate Common Mistakes: Not assigning materials to all the domains. It is sometimes necessary to manually scale the dependent variables. If so, see: Knowledgebase 1030: Error: "Out of memory". See also: Knowledge Base 1254: Controlling the Time Dependent solver timesteps. Therefore, it is recommended to use Adaptive Mesh Refinement which will automatically refine the mesh only in regions where it is needed, and coarsen the mesh elsewhere. I use comsol multiphysics 5.2a and . Knowledgebase 1260: What to do when a linear stationary model is not solving, Knowledge Base 1240: Manually Setting the Scaling of Variables, What to do when a linear stationary model is not solving, Knowledge Base 1254: Controlling the Time Dependent solver timesteps, 2023 by COMSOL. My comment is perhaps a bit nave but it seems to me that you could simply deactivate the term of the background field equation but keep its connexion to the solid to get what you want. If instead the model is linear, see: Knowledgebase 1260: What to do when a linear stationary model is not solving. Top 10 Best Stationary in Brea, CA - October 2022 - Yelp In the COMSOL Multiphysics software, this step of the modeling workflow is made. Hello guys. Using this technique systematically, along with the techniques described previously, will usually identify the nonlinearities in the model that are leading to issues. -Detail: NaN or Inf found when solving linear system using SOR. Thanks for contributing an answer to Stack Overflow! If it is not clear that any of the above strategies are working, it is useful to take a more general approach to verifying the general validity of the model. . Learn how your comment data is processed. Create the time-dependent step or study. Feature: Stationary Solver 1 (sol1/s1) Adaptation gives the same mesh: adaptmesh1. This case is generally difficult, or impossible, to solve since this material property is non-smooth. Examine the model and identify all terms that introduce nonlinearities, such as multiphysics couplings, nonlinear materials relationships, and nonlinear boundary conditions. Iterative , Direct . SGP handled 7 different prints for me at once and they all came out perfectly, in a timely manner. The objective here is to simplify the model to a state where the model will solve, with linear approximations. Linear solvers. "After the incident", I started to be more careful not to trip over things. Perhaps this approach could be adapted to represent your model. What to do when a linear stationary model is not solving - COMSOL If you have both as steps in the same study, then solve that study. When you use an iterative solver, COMSOL Multiphysics estimates the error of the solution while solving. Hi Jason, Specify Material Properties in COMSOL Multiphysics (3/8) For example, in an Electric Currents problem, you may want to consider a system of materials including a good conductor such as copper (with an electric conductivity of ~6e7 S/m) and an insulative material such as glass (which can have electric conductivity of ~1e-14 S/m.) The Continuation method is enabled by default when using the Auxiliary sweep study extension, as shown below. Instead, use a nonlinear material property expression that ramps from a very smooth function to a very nearly discontinuous one. For more details, see: Performing a Mesh Refinement Study, Mesh refinement may often need to be combined with load or nonlinearity ramping and may require a set of studies, first starting with a relatively coarse mesh for nonlinearity ramping, refining the mesh, and the ramping further on the refined mesh. Each physics is thus solved as a standalone problem, using the solution from any previously computed steps as initial values and linearization points. Your Discussion has gone 30 days without a reply. Popular answers (1) This problem generally occurs when there is some mistake in the physics or study section or wrong selection of the mesh size. Examine the model and identify all terms that introduce nonlinearities, such as multiphysics couplings, nonlinear materials relationships, and nonlinear boundary conditions. Name: actdep_int1, Your email address will not be published. P&S Comsol Team: Manuel Kohli, Raphael Schwanninger, Feature: Stationary Solver 1 (sol1/s1) Have you taken a look at this [blog post](https://www.comsol.com/blogs/modeling-fluid-structure-interaction-in-multibody-mechanisms/)? Therefore, an initial value of zero is almost always reasonable if a very small load is applied. Is there a way to use the stationary solution obtained in Comsol 4.2 as the initial conditions in a time dependent model? COMSOL does not assume any legal liability for the accuracy of the data disclosed. Most multiphysics problems are nonlinear. However, it is usually not possible to know this ahead of time. Reply . The solver settings are stored at Study > Solver Configurations > Solution. If the model is nonlinear, see: Improving Convergence of Nonlinear Stationary Models. - Feature: Stationary Solver 1 (sol1/s1)Failed to find a solution. Nonlinearity ramping is an especially useful technique if any of the nonlinear terms in the model are very abrupt. The segregated approach, on the other hand, solves sets of unknowns separately. Load ramping and nonlinearity ramping can be used in combination, but start with only one or a few of the loads or nonlinearities being ramped. Contact COMSOL at Bangalore on their telephone: +9180 25323003. The exceptions are the Heat Transfer interfaces, which have a default Initial Value of 293.15K, or 20C, for the temperature fields. replace it with the expression: The Fully Coupled solution approach, with the Plot While Solving enabled. Extending this logic, if one wants to solve for any arbitrary load on a nonlinear system, it makes sense to solve a sequence of intermediate problems with gradually increasing load values and using the solutions from each previous step as the initial condition for the next step. In that case, the continuation method will automatically backtrack and try to solve for intermediate values in the range of 0.6 through 0.8. You can fix this by pressing 'F12' on your keyboard, Selecting 'Document Mode' and choosing 'standards' (or the latest version First, it is physically intuitive, often matching how one would perform an experiment. Common Study Step Settings - COMSOL Multiphysics Therefore, an initial value of zero is almost always reasonable if a very small load is applied. The objective here is to simplify the model to a state where the model will solve, with linear approximations. COMSOL makes every reasonable effort to verify the information you view on this page. 3. That is, within each outer Newton-type iteration, the segregated approach solves for each segregated group sequentially. See Knowledge Base 1240: Manually Setting the Scaling of Variables. In such cases it will be particularly helpful to ramp the load gradually in time, from consistent initial values.
stationary solver comsol