stationary solver comsol

By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Your internet explorer is in compatibility mode and may not be displaying the website correctly. Tutti i diritti sono riservati. 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. Therefore, an initial value of zero is almost always reasonable if a very small load is applied. The software then computes an initial solution and from there it iteratively re-computes the solution, taking into account how these intermediate solutions affect the nonlinearities. -Detail: NaN or Inf found when solving linear system using SOR. Troubleshooting for 3D trusses, if anyone's out there. : r/COMSOL - reddit Hi Jason, The objective here is to simplify the model to a state where the model will solve, with linear approximations. How can I check before my flight that the cloud separation requirements in VFR flight rules are met? (Frequency Domain should be the last step) However, it is usually not possible to know this ahead of time. A classic example of this is fluid flow around a cylinder with high, but constant, flow rates. Within either of these features, it can also be helpful to enable the Results While Solving option, as shown in the screenshot below, to visualize the iterations being taken during the solution. Multiphysics problems are often nonlinear. If you define this nonlinearity ramping such that the first case (P=0) is a purely linear problem, then you are guaranteed to get a solution for this first step in the ramping. The technique of load ramping is not always reasonable for all problems. The former approach solves for all unknowns in the problem at once, and considers all coupling terms between all unknowns within a single iteration. So far, weve learned how to mesh and solve linear and nonlinear single-physics finite element problems, but have not yet considered what happens when there are multiple different interdependent physics being solved within the same domain. For example, in Solid Mechanics, if the Poisson Ratio set to 0.5, then the model will not solve, as this value in incompatible with the theory of linear elasticity. Hi ! Stationary (time-invariant) models with nonlinearities may converge very slowly. 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. For example, if there is a temperature-dependent material property such as: Each physics is thus solved as a standalone problem, using the solution from any previously computed steps as initial values and linearization points. Such a large difference in the materials properties can be challenging. 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. From there, if an additional small load increment is applied, the previously computed solution is a reasonable initial condition. About the Stationary Solver - COMSOL Multiphysics The Fully Coupled solution approach, with the Plot While Solving enabled. Convergence can be poor when the initial values do not provide a good starting point for this iterative approach. if I want to do an adaptive mesh refinement, I get this error. If the material properties entered are incorrect for the governing equation, the model will generate an error at runtime, usually a Singular Matrix error. You can fix this by pressing 'F12' on your keyboard, Selecting 'Document Mode' and choosing 'standards' (or the latest version Different physics have different default solvers. How to Add a Study to Your Simulation in COMSOL Multiphysics Convergence can be poor when the initial values do not provide a good starting point for this iterative approach. Iterative - COMSOL Multiphysics How can I use it? This involves a systematic reduction in the model complexity. COMSOL makes every reasonable effort to verify the information you view on this page. See if these can be used instead of explicitly modeling parts with high-aspect ratio geometries. At a value of P=0 the above expression is linear, and at a value of P=1 the expression is equal to the original nonlinear expression. Not entering required material parameters. - Variable: B1 - Defined as: 1/ ( ( (comp1.cH2 (unit_m_cf^3))/unit_mol_cf)^2.5) Failed to evaluate variable. ", "Absolutely the best place to shop for flowers and greenery, I spent an hour just looking around for fun prior to purchasing a bouquet, they have the best customer service people all over the place and it's a huge place", "Recently came in here to pick up 45 chocolate Seegars (cigars) for a dinner banquet in honor of my baby nephew. P&S: COMSOL Design Tool for Photonic Devices - ETH Z GCRO-DR is a method for Krylov subspace recycling. Wrong ordering of study steps. Your internet explorer is in compatibility mode and may not be displaying the website correctly. Can someone help me fix the COMSOL error below? | ResearchGate For example, if ramping P over values of: 0.2,0.4,0.6,0.8,1.0 the nonlinear solver may fail to converge for a value of 0.8. Note the star symbol on the Solution feature. - Feature: Stationary Solver 1 (sol1/s1)Failed to find a solution. Changes to these low-level settings from the defaults will usually be quite model- and case-specific. Reviews on Stationary Stores in Brea, CA - Typo, Mievic, Posh Paper, Morning Glory, Select Graphics & Printing, Daiso Japan, Urban Outfitters, Office Depot, Barnes & Noble In such cases, use the same continuation method, but instead ramp the nonlinearities in the model. Starting from zero initial conditions, the nonlinear solver will most likely converge if a sufficiently small load is applied. Repeat this for every nonlinearity of the model. Your internet explorer is in compatibility mode and may not be displaying the website correctly. In many physics areas there exist alternative physics formulations specifically meant for solving cases where the geometry has an extreme aspect ratio. How to solve "Feature: Stationary Solver 1 (sol1/s1) Attempt - COMSOL For example, in a Solid Mechanics (wherein the software is solving for the displacement field within the solid) applying two opposite and equal Boundary Load conditions on a part is not sufficient to define the displacement. Near the top of the Stationary Solver log, the software will report if a linear or nonlinear solver is being used. 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. COMSOL does not assume any legal liability for the accuracy of the data disclosed. In such cases, use the same continuation method, but instead ramp the nonlinearities in the model. That is, they are tuned to achieve convergence in as many cases as possible. Version 5.3 Segregated approach and Direct vs. Iterative linear solvers, Time dependent function and stationary study, Combining Adaptive Mesh Refinement with Data Filtering, What to do when a linear stationary model is not solving, Galleria dei Modelli e delle App di Simulazione, 2023 da COMSOL. The stationary solver is used both for Stationary (time-invariant) and Frequency Domain (time-harmonic) study types. SGP handled 7 different prints for me at once and they all came out perfectly, in a timely manner. Posted 26 set 2019, 17:57 CEST Mesh Version 5.3 0 Replies. Cooling and Solidification of Metal. $125,000.00, Project Engineer (In-person/Hybrid/Remote), $100,000.00 Thanks for contributing an answer to Stack Overflow! 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. With respect to any nonlinearities, replace them by a reasonable linearized term. 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. What is \newluafunction? k(T,P) = 10[W/m/K]*((1-P)+P*exp(-(T-293[K])/100[K])) As P is ramped up, the continuation method uses the previous solutions to compute initial conditions for the more nonlinear cases. Examine the model and identify all terms that introduce nonlinearities, such as multiphysics couplings, nonlinear materials relationships, and nonlinear boundary conditions. With the exception of some thermal problems however, it is often difficult to estimate the solution, so alternative approaches are needed. What is the purpose of non-series Shimano components? She opened prepackaged 6-packs of Seegars to make ", All "stationary stores" results in Brea, CA, Search stationary stores in popular locations. Then use this file to provide the initial conditions in time dependent model. Dun & Bradstreet gathers Office Supplies, Stationery, and Gift Retailers business information from trusted . Can I tell police to wait and call a lawyer when served with a search warrant? Right-click on the Stationary Solver node and add either the Segregated or Fully Coupled feature. Direct PARDISO Solver , PARDISO . This can arise as a consequence of extreme variations in the material properties, or high aspect ratio geometry. I am solving a linear stationary finite element model but the software is not solving. You can fix this by pressing 'F12' on your keyboard, Selecting 'Document Mode' and choosing 'standards' (or the latest version Computational Fluid Dynamics (CFD), API This approach is known as a Continuation Method with a Constant predictor. Iterative , Direct . Consult your product manuals for complete trademark details. Sign in to create your job alert for Stationary Engineer jobs in Brea, California, United States. For example, if ramping P over values of: 0.2,0.4,0.6,0.8,1.0 the nonlinear solver may fail to converge for a value of 0.8. The settings controlling the predictor type. Tutti i diritti sono riservati. What are people saying about cards & stationery in Brea, CA? Nonlinearity ramping is an especially useful technique if any of the nonlinear terms in the model are very abrupt. Wrong ordering of study steps. Find centralized, trusted content and collaborate around the technologies you use most. This segregated approach is used by default for most 3D multiphysics models, and the software will automatically segregate the problem into appropriate groups. The former approach solves for all unknowns in the problem at once, and considers all coupling terms between all unknowns within a single iteration. See also: Knowledge Base 1254: Controlling the Time Dependent solver timesteps. At a value of P=0 the above expression is linear, and at a value of P=1 the expression is equal to the original nonlinear expression. 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. For example, if ramping P over values of: 0.2,0.4,0.6,0.8,1.0 the nonlinear solver may fail to converge for a value of 0.8. View the Settings window for the Materials branch to get a list of all domains with undefined materials and add a material to those domains. Using a predictor of type Constant will take the solution from the iteration and use it as the initial value for the iteration. Here we introduce the two classes of algorithms used to solve multiphysics finite element problems in COMSOL Multiphysics. This guide applies solely to nonlinear stationary models. If the model is very large, and if you do not have very much memory in your computer, you may get an error message regarding memory. 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. - COMSOL Blog Series on COMSOL Multiphysics Solvers Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, Simulation of effect of heated resistance on temperature distribution in laminar flow, COMSOL: Diffusion in Transport of Diluted Species Produces Unphysical Results. The issue here has do with the iterative algorithm used to solve nonlinear stationary models. These are some highly rated cards & stationery in Brea, CA: What are some cards & stationery with a large number of reviews in Brea, CA? As P is ramped up, the continuation method uses the previous solutions to compute initial conditions for the more nonlinear cases. This is for COMSOL 5.2, but should be similar for 4.2: Create the stationary study. It may also reveal that the model itself is ill-posed in some way. If one particular material is missing one property, that material will also be highlighted with a red cross over that material icon in the Model Builder. Near the top of the Stationary Solver log, the software will report if a linear or nonlinear solver is being used. In this case, it would likely be reasonable to treat the insulative material as a perfect insulator, omit it from the analysis, and use the Electric Insulation boundary condition instead of modeling those domains. Ideally, one would use small elements in regions where the solution varies quickly in space, and larger elements elsewhere. One of the key concepts there was the idea of mesh convergence as you refine the mesh, the solution will become more accurate. 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. Despite this, the segregated approach can often converge very robustly, unless there are very strong couplings between the physics in the model. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Instead, use a nonlinear material property expression that ramps from a very smooth function to a very nearly discontinuous one. 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. Changes to these low-level settings from the defaults will usually be quite model- and case-specific. The "Values for dependent values" in study step settings should be set to the default ("Physics-controlled" in 5.2). If you try to enter a variable that is undefined, the automatic syntax highlighting will identify this as you enter it, and it is best practice to resolve this immediately. Resources and documents are provided for your information only, and COMSOL makes no explicit or implied claims to their validity. listed if standards is not an option). The difference between the phonemes /p/ and /b/ in Japanese. 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. Second, the continuation method will automatically take smaller load increments if a solution cannot be found. A Global Parameter has to be introduced (in the above screenshot, P) and is ramped from a value nearly zero up to one. It can be useful while solving sequences of linear systems arising from, for example, nonlinear problems. COMSOL makes every reasonable effort to verify the information you view on this page. Any trademarks referenced in this document are the property of their respective owners. How do/should administrators estimate the cost of producing an online introductory mathematics class? Today's top 351 Stationary Engineer jobs in Brea, California, United States. Improving Convergence of Nonlinear Stationary Models - COMSOL Alternatively, delete and re-create the study. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Name: actdep_int1, Your email address will not be published. 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. The fully coupled and segregated approaches are discussed below. However, it is usually not possible to know this ahead of time. 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 exceptions are the Heat Transfer interfaces, which have a default Initial Value of 293.15K, or 20C, for the temperature fields. Use either a very fine mesh throughout the simulation domain or use adaptive mesh refinement. Any trademarks referenced in this document are the property of their respective owners. Starting from zero initial conditions, the nonlinear solver will most likely converge if a sufficiently small load is applied. Please dont hesitate to post comments below or send emails to us if you experience any other problems. If instead the model is linear, see: Knowledgebase 1260: What to do when a linear stationary model is not solving. It is thus always advised to start this procedure with a simplified 2D, or 2D-axisymmetric model. By default, the COMSOL Multiphysics software determines these values heuristically depending on the physics as, for example, the specified initial values or a solution from an earlier study step. k(T) = 10[W/m/K]+10[W/m/K]*(T>400[K]) Alle Rechte vorbehalten. The Iterative Solvers - COMSOL Multiphysics If the default iterative solver is not converging, try switching to a direct solver, as described here: Understanding the Fully Coupled vs. It is sometimes necessary to manually scale the dependent variables. 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. That is, within each outer Newton-type iteration, the segregated approach solves for each segregated group sequentially. The finite element mesh must be fine enough to resolve the spatial variations in the solution fields. This involves a systematic reduction in the model complexity. Solve the stationary study then the time dependent study. In the extreme case, suppose one wants to model an instantaneous change in properties, such as: This is relatively expensive to do, but will lead to the most robust convergence. 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. Your Discussion has gone 30 days without a reply. The default solver for most 3D models is an iterative solver, which is more sensitive to ill-conditioned problems. 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. COMSOL Error for Initial Values(RF Module) That is, start by first solving a model with a small, but non-zero, load. For the Nozomi from Shinagawa to Osaka, say on a Saturday afternoon, would tickets/seats typically be available - or would you need to book?