stationary solver comsol

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. 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. 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. P&S Comsol Team: Arif Gngr , Yannik Horst , Stefano Valente. The finite element mesh must be fine enough to resolve the spatial variations in the solution fields. I highly recommend this flower shop. This information is relevant both for understanding the inner workings of the solver and for understanding how memory requirements grow with problem size. The former approach solves for all unknowns in the problem at once, and considers all coupling terms between all unknowns within a single iteration. I personally liked emailing them the file, ", "This flower shop is the best! Not entering required material parameters. If these settings have been manually changed, you will see a small star symbol on the Solution feature, as shown in the screenshot below. 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. ", "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. Examine the model and identify all terms that introduce nonlinearities, such as multiphysics couplings, nonlinear materials relationships, and nonlinear boundary conditions. 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. - Function: ^ Failed to evaluate variable. 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. Resources and documents are provided for your information only, and COMSOL makes no explicit or implied claims to their validity. The issue here has do with the iterative algorithm used to solve nonlinear stationary models. The memory requirements will always be lower than with the fully coupled approach, and the overall solution time can often be lower as well. Minimising the environmental effects of my dyson brain. 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. That is, within each outer Newton-type iteration, the segregated approach solves for each segregated group sequentially. In such cases it will be particularly helpful to ramp the load gradually in time, from consistent initial values. Here we introduce a more robust approach to solving nonlinear problems. If it does so, use a finer increment in that range. This is useful since the software will then return an estimation of the maximum possible loadcase for which the solver can converge. Communication over the phone, in person, and through email was very easy. This case is generally difficult, or impossible, to solve since this material property is non-smooth. Second, the continuation method will automatically take smaller load increments if a solution cannot be found. k(T,P) = 10[W/m/K]*((1-P)+P*exp(-(T-293[K])/100[K])) There will always already be either a Segregated or Fully Coupled feature beneath this. The issue here has do with the iterative algorithm used to solve nonlinear stationary models. Right-click on the Stationary Solver node and add either the Segregated or Fully Coupled feature. That is, the material property changes instantaneously from 10W/m/K to 20W/m/K at 400K. 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. Your Discussion has gone 30 days without a reply. One of the key concepts there was the idea of mesh convergence as you refine the mesh, the solution will become more accurate. Get notified about new Stationary Engineer jobs in Brea, California, United States. The conditions on the geometric aspect ratio are relatively more strict. Not meshing all the domains. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. What is \newluafunction? 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 Fully Coupled solution approach, with the Plot While Solving enabled. This segregated approach is used by default for most 3D multiphysics models, and the software will automatically segregate the problem into appropriate groups. The algorithm is, generally speaking, a Newton's method approach. Singular matrix., Make sure you defined your ports correctly:Boundary selectionType of port: e.g. 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. Using this technique systematically, along with the techniques described previously, will usually identify the nonlinearities in the model that are leading to issues. November 11, 2013. Changes to these low-level settings from the defaults will usually be quite model- and case-specific. COMSOL does not assume any legal liability for the accuracy of the data disclosed. Starting from zero initial conditions, the nonlinear solver will most likely converge if a sufficiently small load is applied. 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. Hello guys. In this blog post we introduce the two classes of algorithms that are used in COMSOL to solve systems of linear equations that arise when solving any finite element problem. Here, we will examine techniques for accelerating the convergence of these two methods. If you try to solve such a model, there will be an error at runtime that will provide information about the variable name and where it is being called. Multiphysics problems are often nonlinear. This case is generally difficult, or impossible, to solve since this material property is non-smooth. Full text of the 'Sri Mahalakshmi Dhyanam & Stotram'. Examine the model and identify all terms that introduce nonlinearities, such as multiphysics couplings, nonlinear materials relationships, and nonlinear boundary conditions. Set initial conditions in the physics to the appropriate dependent model variable names rather than the default 0. Once a simplified solvable version of the model has been found, gradually increase the model complexity again, re-introducing nonlinearities and multiphysics couplings. k(T) = 10[W/m/K]*exp(-(T-293[K])/100[K]) Each physics is thus solved as a standalone problem, using the solution from any previously computed steps as initial values and linearization points. Common Mistakes: Not assigning materials to all the domains. In many physics areas there exist alternative physics formulations specifically meant for solving cases where the geometry has an extreme aspect ratio. You can fix this by pressing 'F12' on your keyboard, Selecting 'Document Mode' and choosing 'standards' (or the latest version There will also be a red cross over the Materials branch icon. With respect to any nonlinearities, replace them by a reasonable linearized term. A classic example of this is fluid flow around a cylinder with high, but constant, flow rates. Not the answer you're looking for? If both load ramping and nonlinearity ramping are still leading to slow convergence, refine the mesh. Iterative , Direct . The technique of load ramping is not always reasonable for all problems. Use this parameter to modify the nonlinearity expressions in the model. Posted 26 set 2019, 17:57 CEST Mesh Version 5.3 0 Replies. Does ZnSO4 + H2 at high pressure reverses to Zn + H2SO4? Such problems must solved in the time domain. This algorithm was also useful for understanding what happens near a failure load. The problem is that when I run my model this message appear: Undefined value found. 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. See also: Knowledge Base 1254: Controlling the Time Dependent solver timesteps. Using this technique systematically, along with the techniques described previously, will usually identify the nonlinearities in the model that are leading to issues. This parameter is used within the physics interfaces to multiply one, some, or all of the applied loads. Your internet explorer is in compatibility mode and may not be displaying the website correctly. Is there a way to use the stationary solution obtained in Comsol 4.2 as the initial conditions in a time dependent model? 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. Ramping the nonlinearities over time is not as strongly motivated, but step changes in nonlinearities should be smoothed out throughout the simulation. 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. This approach is used by default for most 1D, 2D, and 2D-axisymmetric models. An example model that combines the techniques of nonlinearity ramping and adaptive mesh refinement with multiple study steps is: listed if standards is not an option). If you still need help with COMSOL and have an on-subscription license, please visit our Support Center for help. k(T) = 10[W/m/K]+10[W/m/K]*(T>400[K]) Under Initial values of variables solved for, the default value of the Settingslist is Physics controlled. 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. You can fix this by pressing 'F12' on your keyboard, Selecting 'Document Mode' and choosing 'standards' (or the latest version Check the solver log to see if the continuation method is backtracking. The default Initial Values for the unknowns in most physics interfaces are zero. It is thus always advised to start this procedure with a simplified 2D, or 2D-axisymmetric model. Check the solver log to see if the continuation method is backtracking. First, it is physically intuitive, often matching how one would perform an experiment. Name: actdep_int1, Your email address will not be published. What is the purpose of non-series Shimano components? The memory requirements will always be lower than with the fully coupled approach, and the overall solution time can often be lower as well. Note: there is no way to couple this field with the time dependent nature of this physics. (Frequency Domain should be the last step). 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. Each physics is thus solved as a standalone problem, using the solution from any previously computed steps as initial values and linearization points. That is, start by first solving a model with a small, but non-zero, load. Understanding the Fully Coupled vs. The stationary solver is used both for Stationary (time-invariant) and Frequency Domain (time-harmonic) study types. See Knowledge Base 1240: Manually Setting the Scaling of Variables. The idea behind the GCRO-DR method is to retain the subspace determined while solving previous systems and use it to reduce the cost of solving the next system. 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. 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. 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. That is, when solving, the software starts with the user-specified initial values to evaluate all solution-dependent terms. Different physics have different default solvers. 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. Despite this, the segregated approach can often converge very robustly, unless there are very strong couplings between the physics in the model. That is, within each outer Newton-type iteration, the segregated approach solves for each segregated group sequentially. If you are unsure if your problem is linear and stationary, look at the Log. Each physics is thus solved as a standalone problem, using the solution from any previously computed steps as initial values and linearization points. 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. Studysteps might be listed in wrong order: Not assigning materials to all the domains. Right-click on the Stationary Solver node and add either the Segregated or Fully Coupled feature. Hi Jason, Segregated approach and Direct vs. Iterative linear solvers, About the time step setting of the solver, Introducing Goal Seeking into the Segregated Solver. Again, introduce a Global Parameter that gets ramped from exactly zero to one. In such cases, use the same continuation method, but instead ramp the nonlinearities in the model. Reviews on Stationary in Brea, CA - Mievic, Typo, Tokyo Japanese Lifestyle, Fancy, Posh Paper, Morning Glory, Velvet Fox Designs, Barnes & Noble, Michaels, Select Graphics & Printing Could you expand a little bit more why the coupling is impossible? Stationary (time-invariant) models with nonlinearities may converge very slowly. The Auxiliary Sweep can be used to implement ramping of any Global Parameter. The fully coupled and segregated approaches are discussed below. Could you expand a little bit more why the coupling is impossible? With the exception of some thermal problems however, it is often difficult to estimate the solution, so alternative approaches are needed. Second, the continuation method will automatically take smaller load increments if a solution cannot be found. Unknown function or operator. Multiscale Modeling in High-Frequency Electromagnetics. Today's top 351 Stationary Engineer jobs in Brea, California, United States. From there, if an additional small load increment is applied, the previously computed solution is a reasonable initial condition. Most multiphysics problems are nonlinear. With the exception of some thermal problems however, it is often difficult to estimate the solution, so alternative approaches are needed. there is no defined multiphysics for it as I know, I have a standing accoustic wave and a flow in the background but I don't see their connection. Posted Sep 9, 2020, 1:44 p.m. EDT Instead, use a nonlinear material property expression that ramps from a very smooth function to a very nearly discontinuous one. 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. 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 unknowns are segregated into groups, usually according the physics that they represent, and these groups are solved one after another. In such cases it will be particularly helpful to ramp the load gradually in time, from consistent initial values. 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.) Solve the stationary study then the time dependent study. If so, see: Knowledgebase 1030: Error: "Out of memory". Posted 26 set 2019, 11:57 GMT-4 Your email address will not be published. A classic example of this is fluid flow around a cylinder with high, but constant, flow rates. Stationary Solver Iterative Direct . Examine the model and identify all terms that introduce nonlinearities, such as multiphysics couplings, nonlinear materials relationships, and nonlinear boundary conditions. What sort of strategies would a medieval military use against a fantasy giant? Wish you all the best. 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. Consult your product manuals for complete trademark details. 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. The continuation method will again backtrack and try intermediate values of the ramping parameter, thus giving you the nearest approximation to the abrupt transition that is solvable. In this posting, we introduce the idea of ramping the nonlinearities in the problem to improve convergence. Segregated approach and Direct vs. 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. COMSOL makes every reasonable effort to verify the information you view on this page. Consult your product manuals for complete trademark details. Right-click on the Stationary Solver node and add either the Segregated or Fully Coupled feature. 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. $140,000.00, $120,000.00 The exceptions are the Heat Transfer interfaces, which have a default Initial Value of 293.15K, or 20C, for the temperature fields. This approach is known as a Continuation Method with a Constant predictor. Segregated approach and Direct vs. COMSOL makes every reasonable effort to verify the information you view on this page. Improving Convergence of Nonlinear Stationary Models, Knowledgebase 1030: Error: "Out of memory", Knowledgebase 1030: Performing a Mesh Refinement Study, Understanding the Fully Coupled vs. This involves a systematic reduction in the model complexity. Numerically ill-conditioned means that the system matrix is nearly singular and that it will be difficult to solve on a finite-precision computer. listed if standards is not an option). If both load ramping and nonlinearity ramping are still leading to slow convergence, refine the mesh. Then I stored the resulting solution, and used it to to solve the stationary solver again by using the solver manager. Resources and documents are provided for your information only, and COMSOL makes no explicit or implied claims to their validity. Is it possible to rotate a window 90 degrees if it has the same length and width? 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. $125,000.00, Project Engineer (In-person/Hybrid/Remote), $100,000.00 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. Understanding the Fully Coupled vs. For example, if there is a temperature-dependent material property such as: Ideally, one would use small elements in regions where the solution varies quickly in space, and larger elements elsewhere. That is, they are tuned to achieve convergence in as many cases as possible. To learn more, see our tips on writing great answers. - Save my name, email, and website in this browser for the next time I comment. If instead the model is linear, see: Knowledgebase 1260: What to do when a linear stationary model is not solving. . Consult your product manuals for complete trademark details. Click the link in the email we sent to to verify your email address and activate your job alert. 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. As P is ramped up, the continuation method uses the previous solutions to compute initial conditions for the more nonlinear cases. See also: Knowledge Base 1254: Controlling the Time Dependent solver timesteps. Why do many companies reject expired SSL certificates as bugs in bug bounties? The Auxiliary Sweep can be used to implement ramping of any Global Parameter. Why? Resources and documents are provided for your information only, and COMSOL makes no explicit or implied claims to their validity. In the extreme case, suppose one wants to model an instantaneous change in properties, such as: Dr.S.Ravindran Cite 1 Recommendation Popular answers (1). A Global Parameter has to be introduced (in the above screenshot, P) and is ramped from a value nearly zero up to one. This segregated approach is used by default for most 3D multiphysics models, and the software will automatically segregate the problem into appropriate groups. "I chose this print shop based off yelp reviews and was very happy with the outcome! 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. As part of our solver blog series we have discussed solving nonlinear static finite element problems, load ramping for improving convergence of nonlinear problems, and nonlinearity ramping for improving convergence of nonlinear problems. Wrong ordering of study steps. 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. Perhaps this approach could be adapted to represent your model. L'objectif de notre prsent travail se repose sur l'tude par simulation numrique du comportement de bton au jeune ge sous des conditions svres de temprature pendant les premires 24h aprs. 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. 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. This information is relevant both for understanding the inner workings of the solver and for understanding how memory requirements grow with problem size. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. replace it with the expression: Does anyone know what should cause this problem? This involves a systematic reduction in the model complexity. I am solving a linear stationary finite element model but the software is not solving. Convergence can be poor when the initial values do not provide a good starting point for this iterative approach. That is: Even if the forces on a part are opposite and equal, this is not sufficient information to say where the part is, so you must add some other condition, such as as Fixed Constraint to constrain displacement. Any trademarks referenced in this document are the property of their respective owners. In such cases, use the same continuation method, but instead ramp the nonlinearities in the model. That is, start by first solving a model with a small, but non-zero, load. This is relatively expensive to do, but will lead to the most robust convergence. However, load ramping will not work in all cases, or may be inefficient. 0 Replies, Please login with a confirmed email address before reporting spam. This guide applies solely to nonlinear stationary models. It is also possible to manually refine the mesh. Reviews on Stationary Stores in Brea, CA - Typo, Mievic, Posh Paper, Morning Glory, Select Graphics & Printing, Daiso Japan, Urban Outfitters, Office Depot, Barnes & Noble