stationary solver comsol

Wrong ordering of study steps. Studysteps might be listed in wrong order: Not assigning materials to all the domains. This algorithm was also useful for understanding what happens near a failure load. replace it with the expression: If you see this, right-click on the Solution feature and select Reset Solver to Default. This will use the initial conditions you specified in your physics setting (usually 0 is used in the physics settings). Making statements based on opinion; back them up with references or personal experience. Understanding the Fully Coupled vs. You can fix this by pressing 'F12' on your keyboard, Selecting 'Document Mode' and choosing 'standards' (or the latest version Using the first order optimality. 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. $125,000.00, Project Engineer (In-person/Hybrid/Remote), $100,000.00 This is useful since the software will then return an estimation of the maximum possible loadcase for which the solver can converge. COMSOL does not assume any legal liability for the accuracy of the data disclosed. Sign in to create your job alert for Stationary Engineer jobs in Brea, California, United States. 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, Galleria dei Modelli e delle App di Simulazione, 2023 da COMSOL. 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. Consult your product manuals for complete trademark details. Hello, This is relatively expensive to do, but will lead to the most robust convergence. listed if standards is not an option). 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. In many physics areas there exist alternative physics formulations specifically meant for solving cases where the geometry has an extreme aspect ratio. 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. Despite this, the segregated approach can often converge very robustly, unless there are very strong couplings between the physics in the model. "After the incident", I started to be more careful not to trip over things. listed if standards is not an option). In a previous blog entry, we introduced meshing considerations for linear static problems. The segregated approach, on the other hand, solves sets of unknowns separately. Convergence can be poor when the initial values do not provide a good starting point for this iterative approach. 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. The stationary solver is used both for Stationary (time-invariant) and Frequency Domain (time-harmonic) study types. Solver . The algorithm is, generally speaking, a Newton's method approach. Acidity of alcohols and basicity of amines. Instead, use a nonlinear material property expression that ramps from a very smooth function to a very nearly discontinuous one. Numerically ill-conditioned means that the system matrix is nearly singular and that it will be difficult to solve on a finite-precision computer. That is, within each outer Newton-type iteration, the segregated approach solves for each segregated group sequentially. You can unsubscribe from these emails at any time. The objective here is to simplify the model to a state where the model will solve, with linear approximations. Repeat this for every nonlinearity of the model. Reviews on Stationary Stores in Brea, CA - Typo, Mievic, Posh Paper, Morning Glory, Select Graphics & Printing, Daiso Japan, Urban Outfitters, Office Depot, Barnes & Noble This case is generally difficult, or impossible, to solve since this material property is non-smooth. Again, introduce a Global Parameter that gets ramped from exactly zero to one. Right-click on the Stationary Solver node and add either the Segregated or Fully Coupled feature. Right-click on the Stationary Solver node and add either the Segregated or Fully Coupled feature. Alternatively, delete and re-create the study. Posted 26 set 2019, 11:57 GMT-4 This parameter is used within the physics interfaces to multiply one, some, or all of the applied loads. 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. Thanks, Andres. 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. See if these can be used instead of explicitly modeling parts with high-aspect ratio geometries. However, it is usually not possible to know this ahead of time. -Detail: NaN or Inf found when solving linear system using SOR. 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. Such problems must solved in the time domain. See also: Knowledge Base 1254: Controlling the Time Dependent solver timesteps. What is \newluafunction? The other low-level default settings within the Stationary Solver are chosen for robustness. The conditions on the geometric aspect ratio are relatively more strict. Resources and documents are provided for your information only, and COMSOL makes no explicit or implied claims to their validity. if I want to do an adaptive mesh refinement, I get this error. Does ZnSO4 + H2 at high pressure reverses to Zn + H2SO4? These are some cards & stationery with a large number of reviews in Brea, CA. You can fix this by pressing 'F12' on your keyboard, Selecting 'Document Mode' and choosing 'standards' (or the latest version Then I stored the resulting solution, and used it to to solve the stationary solver again by using the solver manager. 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. It is thus always advised to start this procedure with a simplified 2D, or 2D-axisymmetric model. This is for COMSOL 5.2, but should be similar for 4.2: Create the stationary study. As we saw in Load Ramping of Nonlinear Problems, we can use the continuation method to ramp the loads on a problem up from an unloaded case where we know the solution. Such a case would be better to address instead with the Shell physics interface, which is specially formulated for handling thin-walled structural parts. See also: Knowledge Base 1254: Controlling the Time Dependent solver timesteps. 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. Hi Alexis, Nonlinearity ramping is an especially useful technique if any of the nonlinear terms in the model are very abrupt. You can fix this by pressing 'F12' on your keyboard, Selecting 'Document Mode' and choosing 'standards' (or the latest version There will always already be either a Segregated or Fully Coupled feature beneath this. It may also reveal that the model itself is ill-posed in some way. The unknowns are segregated into groups, usually according the physics that they represent, and these groups are solved one after another. With sufficient simplification, a model can be reduced to a linear problem, and if this simplified model does not converge, see: What to do when a linear stationary model is not solving. k(T) = 10[W/m/K]+10[W/m/K]*(T>400[K]) The default Initial Values for the unknowns in most physics interfaces are zero. As P is ramped up, the continuation method uses the previous solutions to compute initial conditions for the more nonlinear cases. Understanding the Fully Coupled vs. ", "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. 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. Stationary (time-invariant) models with nonlinearities may converge very slowly. There are also cases when an extremely poor quality mesh leads to an ill-conditioned problem, This issue often arises in combination with, and as a consequence of, geometries that have extreme aspect ratios. 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. Feature: Stationary Solver 1 (sol1/s1)" . An example model that combines the techniques of nonlinearity ramping and adaptive mesh refinement with multiple study steps is: 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. k(T,P) = 10[W/m/K]*((1-P)+P*exp(-(T-293[K])/100[K])) This solver is automatically used when a Stationary or Frequency Domain study is added to the model. COMSOL does not assume any legal liability for the accuracy of the data disclosed. 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. This approach is known as a Continuation Method with a Constant predictor. Nonlinearity ramping is an especially useful technique if any of the nonlinear terms in the model are very abrupt. Function: / Failed to evaluate expression. COMSOL makes every reasonable effort to verify the information you view on this page. The objective here is to simplify the model to a state where the model will solve, with linear approximations. 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. As P is ramped up, the continuation method uses the previous solutions to compute initial conditions for the more nonlinear cases. Multiscale Modeling in High-Frequency Electromagnetics. 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. Use either a very fine mesh throughout the simulation domain or use adaptive mesh refinement. replace it with the expression: Starting from zero initial conditions, the nonlinear solver will most likely converge if a sufficiently small load is applied. I want to conduct a simulation to find a solution (u) and its first derivative (ux) using a 3D stationary model. (Frequency Domain should be the last step). If you are unsure if your problem is linear and stationary, look at the Log. About the Stationary Solver The following background information about the Stationary Solver discusses these topics: Damped Newton Methods, Termination Criterion for the Fully Coupled and Segregated Attribute Nodes, Linear Solvers versus Nonlinear Solvers, and Pseudo Time Stepping. However, if a lower-level change has been manually made to the solver settings, the software will not automatically use the correct default solver. Such a large difference in the materials properties can be challenging. The finite element mesh must be fine enough to resolve the spatial variations in the solution fields. 3 Replies, Please login with a confirmed email address before reporting spam. Communication over the phone, in person, and through email was very easy. Any trademarks referenced in this document are the property of their respective owners. Second, the continuation method will automatically take smaller load increments if a solution cannot be found. With sufficient simplification, a model can be reduced to a linear problem, and if this simplified model does not converge, see: What to do when a linear stationary model is not solving. In such cases, see if one material (or the other) can be omitted from the analysis completely. Once the error estimate is small enough, as determined by the convergence criterion (20-16) the software terminates the computations and returns a solution. Resources and documents are provided for your information only, and COMSOL makes no explicit or implied claims to their validity. P&S: COMSOL Design Tool for Photonic Devices. If it does so, use a finer increment in that range. 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. For example, if there is a temperature-dependent material property such as: If your matrix is singular than no solver in the world can solve Ax=B. The finite element mesh must be fine enough to resolve the spatial variations in the solution fields. The issue here has do with the iterative algorithm used to solve nonlinear stationary models. If both load ramping and nonlinearity ramping are still leading to slow convergence, refine the mesh. Each physics is thus solved as a standalone problem, using the solution from any previously computed steps as initial values and linearization points. Right-click on the Stationary Solver node and add either the Segregated or Fully Coupled feature. Segregated approach and Direct vs. First, it is physically intuitive, often matching how one would perform an experiment. Under Initial values of variables solved for, the default value of the Settingslist is Physics controlled. The "Values for dependent values" in study step settings should be set to the default ("Physics-controlled" in 5.2). Today's top 351 Stationary Engineer jobs in Brea, California, United States. This segregated approach is used by default for most 3D multiphysics models, and the software will automatically segregate the problem into appropriate groups. 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. Your email address will not be published. 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. It is sometimes necessary to manually scale the dependent variables. In the extreme case, suppose one wants to model an instantaneous change in properties, such as: 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. Feature: Stationary Solver 1 (sol1/s1) Attempt to evaluate nonintegral power of negative number. listed if standards is not an option). 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. In such cases, use the same continuation method, but instead ramp the nonlinearities in the model. That is: It is also possible to compute the derivative of the solution with respect to the continuation parameter and use that derivative (evaluated at the iteration) to compute a new initial value: where is the stepsize of the continuation parameter. The finite element mesh must be fine enough to resolve the spatial variations in the solution fields. With sufficient simplification, a model can be reduced to a linear problem, and if this simplified model does not converge, see: What to do when a linear stationary model is not solving. The Auxiliary Sweep can be used to implement ramping of any Global Parameter. With the exception of some thermal problems however, it is often difficult to estimate the solution, so alternative approaches are needed. Perhaps this approach could be adapted to represent your model. 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. 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. The exceptions are the Heat Transfer interfaces, which have a default Initial Value of 293.15K, or 20C, for the temperature fields. 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. If it does so, use a finer increment in that range. 3. Your internet explorer is in compatibility mode and may not be displaying the website correctly. That is, the material property changes instantaneously from 10W/m/K to 20W/m/K at 400K. The solver settings are stored at Study > Solver Configurations > Solution. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. That is, within each outer Newton-type iteration, the segregated approach solves for each segregated group sequentially. Therefore, an initial value of zero is almost always reasonable if a very small load is applied. If both load ramping and nonlinearity ramping are still leading to slow convergence, refine the mesh. The default solver for most 3D models is an iterative solver, which is more sensitive to ill-conditioned problems. Ramping the nonlinearities over time is not as strongly motivated, but step changes in nonlinearities should be smoothed out throughout the simulation. 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. Note the star symbol on the Solution feature. listed if standards is not an option). Resources and documents are provided for your information only, and COMSOL makes no explicit or implied claims to their validity. In such cases it will be particularly helpful to ramp the load gradually in time, from consistent initial values. Multiphysics problems are often nonlinear. The former approach solves for all unknowns in the problem at once, and considers all coupling terms between all unknowns within a single iteration. Not meshing all the domains. A classic example of this is fluid flow around a cylinder with high, but constant, flow rates. To switch between these solver types, go to the Stationary Solver node within the Study sequence. I'm trying to model a solid that's moving through a steady background field in a background flow, I want to take into account the effect of movement of the solid after each time step so I have to use stationary solver after each time step in order to see how field has changed after solid moved. Tutti i diritti sono riservati. This information is relevant both for understanding the inner workings of the solver and for understanding how memory requirements grow with problem size. Required fields are marked *. This will use the initial conditions you specified in your physics setting (usually 0 is used in the physics settings). 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. My comment is perhaps a bit nave but it seems to me that you could simply deactivate the \frac{\partial \cdot}{\partial t} term of the background field equation but keep its connexion to the solid to get what you want. This guide applies solely to nonlinear stationary models. How do/should administrators estimate the cost of producing an online introductory mathematics class? Set initial conditions in the physics to the appropriate dependent model variable names rather than the default 0. Segregated approach and Direct vs. Iterative linear solvers, About the time step setting of the solver, Introducing Goal Seeking into the Segregated Solver. If instead the model is linear, see: Knowledgebase 1260: What to do when a linear stationary model is not solving. k(T) = 10[W/m/K]+10[W/m/K]*(T>400[K]) 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. A classic example of this is fluid flow around a cylinder with high, but constant, flow rates. 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. I use comsol multiphysics 5.2a and . COMSOL makes every reasonable effort to verify the information you view on this page. Cooling and Solidification of Metal. Any trademarks referenced in this document are the property of their respective owners. The advantages of the continuation method are two-fold. The Continuation method is enabled by default when using the Auxiliary sweep study extension, as shown below. Create the time-dependent step or study. First, it is physically intuitive, often matching how one would perform an experiment. Instead, use a nonlinear material property expression that ramps from a very smooth function to a very nearly discontinuous one. Alle Rechte vorbehalten. Wrong ordering of study steps. 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. New Stationary Engineer jobs added daily. They worked with me. 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. 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. This involves a systematic reduction in the model complexity. Set "Values for dependent variables" in study step settings to User ControlledSolutionYour Stationary Study. To learn more, see our tips on writing great answers. From there, if an additional small load increment is applied, the previously computed solution is a reasonable initial condition. COMSOL does not assume any legal liability for the accuracy of the data disclosed. Wrong ordering of study steps. In this posting, we introduce the idea of ramping the nonlinearities in the problem to improve convergence. The Fully Coupled solution approach, with the Plot While Solving enabled. If the material properties entered are incorrect for the governing equation, the model will generate an error at runtime, usually a Singular Matrix error. It is sometimes necessary to manually scale the dependent variables. k(T) = 10[W/m/K]*exp(-(T-293[K])/100[K]) First, it is physically intuitive, often matching how one would perform an experiment. The memory requirements will always be lower than with the fully coupled approach, and the overall solution time can often be lower as well. A Global Parameter has to be introduced (in the above screenshot, P) and is ramped from a value nearly zero up to one. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Therefore, an initial value of zero is almost always reasonable if a very small load is applied. listed if standards is not an option). Repeat this for every nonlinearity of the model. Using a predictor of type Constant will take the solution from the iteration and use it as the initial value for the iteration. In the extreme case, suppose one wants to model an instantaneous change in properties, such as: Hence Comsol solved for the stationary solution at different points of time. There will also be a red cross over the Materials branch icon. thanks for reply 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. You can fix this by pressing 'F12' on your keyboard, Selecting 'Document Mode' and choosing 'standards' (or the latest version That is: It is also possible to compute the derivative of the solution with respect to the continuation parameter and use that derivative (evaluated at the iteration) to compute a new initial value: where is the stepsize of the continuation parameter. - Feature: Stationary Solver 1 (sol1/s1)Failed to find a solution. This is useful since the software will then return an estimation of the maximum possible loadcase for which the solver can converge. Despite this, the segregated approach can often converge very robustly, unless there are very strong couplings between the physics in the model. Your internet explorer is in compatibility mode and may not be displaying the website correctly. 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. Linear solvers. Most multiphysics problems are nonlinear. An example model that combines the techniques of nonlinearity ramping and adaptive mesh refinement with multiple study steps is: Connect and share knowledge within a single location that is structured and easy to search. What is the purpose of non-series Shimano components? Once a simplified solvable version of the model has been found, gradually increase the model complexity again, re-introducing nonlinearities and multiphysics couplings. Learn how your comment data is processed. Get notified about new Stationary Engineer jobs in Brea, California, United States. 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. The difference between the phonemes /p/ and /b/ in Japanese. This approach is known as a Continuation Method with a Constant predictor. The settings controlling the predictor type. (Frequency Domain should be the last step) This doesn't seem to me the most elegant of methods, since I am essentially solving a stationary solution using a time dependent 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 memory requirements will always be lower than with the fully coupled approach, and the overall solution time can often be lower as well. 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 There are two approaches that can be used when iteratively solving the nonlinear system of equations: a Fully Coupled or a Segregated approach. . Click the link in the email we sent to to verify your email address and activate your job alert. P&S Comsol Team: Yannik Horst, Manuel Kohli, Xinzhi Zhang. That is, start by first solving a model with a small, but non-zero, load. That is, the material property changes instantaneously from 10W/m/K to 20W/m/K at 400K. Right-click on the Stationary Solver node and add either the Segregated or Fully Coupled feature. She opened prepackaged 6-packs of Seegars to make ", All "stationary stores" results in Brea, CA, Search stationary stores in popular locations. 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.)

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