stationary solver comsol

This segregated approach is used by default for most 3D multiphysics models, and the software will automatically segregate the problem into appropriate groups. 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. How can I check before my flight that the cloud separation requirements in VFR flight rules are met? Contact COMSOL at Bangalore on their telephone: +9180 25323003. See also: Knowledge Base 1254: Controlling the Time Dependent solver timesteps. Your internet explorer is in compatibility mode and may not be displaying the website correctly. 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. It is also possible to manually refine the mesh. The problem is that when I run my model this message appear: Undefined value found. This parameter is used within the physics interfaces to multiply one, some, or all of the applied loads. It is sometimes necessary to manually scale the dependent variables. Any trademarks referenced in this document are the property of their respective owners. The issue here has do with the iterative algorithm used to solve nonlinear stationary models. Stationary Engineer Jobs in Brea, California, United States, $87,400.00 COMSOL 22.9K subscribers Adding a study to your simulation is necessary in order to solve your problem. First, it is physically intuitive, often matching how one would perform an experiment. Not entering required material parameters. Some models are numerically ill-conditioned due to the setup. A linear finite element model is one in which all of the material properties, loads, boundary conditions, etc are constant with respect to the solution, and the governing partial differential equations are themselves linear. 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. Today's top 351 Stationary Engineer jobs in Brea, California, United States. if I want to do an adaptive mesh refinement, I get this error. However, if a lower-level change has been manually made to the solver settings, the software will not automatically use the correct default solver. The coupling terms between the different groups are thus neglected. 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. With the exception of some thermal problems however, it is often difficult to estimate the solution, so alternative approaches are needed. The default Initial Values for the unknowns in most physics interfaces are zero. Instead, use a nonlinear material property expression that ramps from a very smooth function to a very nearly discontinuous one. They deal with COMSOL package and train users. The Continuation method is enabled by default when using the Auxiliary sweep study extension, as shown below. k(T) = 10[W/m/K]*exp(-(T-293[K])/100[K]) Get notified about new Stationary Engineer jobs in Brea, California, United States. 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. 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. Stationary (time-invariant) models with nonlinearities may converge very slowly. (Frequency Domain should be the last step) 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. We are planning to continuously update this page throughout the semester and hopefully, this will become a reference during your projects as well. 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. In such cases, use the same continuation method, but instead ramp the nonlinearities in the model. Linear solvers. She opened prepackaged 6-packs of Seegars to make ", All "stationary stores" results in Brea, CA, Search stationary stores in popular locations. I highly recommend this flower shop. Resources and documents are provided for your information only, and COMSOL makes no explicit or implied claims to their validity. We use COMSOL Multiphysics for solving distributed optimal control of un-steady Burgers equation without constraints and with pointwise control constraints. The technique of load ramping is not always reasonable for all problems. If you see this, right-click on the Solution feature and select Reset Solver to Default. k(T) = 10[W/m/K]+10[W/m/K]*(T>400[K]) 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. Each physics is thus solved as a standalone problem, using the solution from any previously computed steps as initial values and linearization points. What is the purpose of non-series Shimano components? You can unsubscribe from these emails at any time. 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. 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. Near the top of the Stationary Solver log, the software will report if a linear or nonlinear solver is being used. One of the key concepts there was the idea of mesh convergence as you refine the mesh, the solution will become more accurate. 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. Examine the model and identify all terms that introduce nonlinearities, such as multiphysics couplings, nonlinear materials relationships, and nonlinear boundary conditions. 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. The coupling terms between the different groups are thus neglected. Segregated approach and Direct vs. Multiphysics problems are often nonlinear. What did people search for similar to stationary stores in Brea, CA? The unknowns are segregated into groups, usually according the physics that they represent, and these groups are solved one after another. 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. Once a simplified solvable version of the model has been found, gradually increase the model complexity again, re-introducing nonlinearities and multiphysics couplings. 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. Such problems must solved in the time domain. - The Fully Coupled solution approach, with the Plot While Solving enabled. The former approach solves for all unknowns in the problem at once, and considers all coupling terms between all unknowns within a single iteration. Therefore, an initial value of zero is almost always reasonable if a very small load is applied. 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. If both load ramping and nonlinearity ramping are still leading to slow convergence, refine the mesh. Why is there a voltage on my HDMI and coaxial cables? This is a review for cards & stationery in Brea, CA: "Love this store!!! The memory requirements will always be lower than with the fully coupled approach, and the overall solution time can often be lower as well. - Feature: Stationary Solver 1 (sol1/s1)Failed to find a solution. What sort of strategies would a medieval military use against a fantasy giant? A Global Parameter has to be introduced (in the above screenshot, P) and is ramped from a value nearly zero up to one. That is, when solving, the software starts with the user-specified initial values to evaluate all solution-dependent terms. Mesh . If a good estimate to the solution field is known, this can be entered as an an expression in the Initial Value field. k(T,P) = 10[W/m/K]*((1-P)+P*exp(-(T-293[K])/100[K])) 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. Check the solver log to see if the continuation method is backtracking. Right-click on the Stationary Solver node and add either the Segregated or Fully Coupled feature. 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. November 11, 2013. - Feature: Stationary Solver 1 (sol1/s1) 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. If the model is nonlinear, see: Improving Convergence of Nonlinear Stationary Models. An example would be a linear static structural model of an aluminum beverage can. In such cases, use the same continuation method, but instead ramp the nonlinearities in the model. $130,000.00. 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. This guide applies solely to nonlinear stationary models. Sign in to create your job alert for Stationary Engineer jobs in Brea, California, United States. Right-click on the Stationary Solver node and add either the Segregated or Fully Coupled feature. Consult your product manuals for complete trademark details. Leverage your professional network, and get hired. 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. See Knowledge Base 1240: Manually Setting the Scaling of Variables. What is \newluafunction? Second, the continuation method will automatically take smaller load increments if a solution cannot be found. 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. Alle Rechte vorbehalten. Convergence can be poor when the initial values do not provide a good starting point for this iterative approach. 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. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. COMSOL does not assume any legal liability for the accuracy of the data disclosed. Multiphysics problems are often nonlinear. You can fix this by pressing 'F12' on your keyboard, Selecting 'Document Mode' and choosing 'standards' (or the latest version Hello guys. Find detailed information on Office Supplies, Stationery, and Gift Retailers companies in Brea, California, United States of America, including financial statements, sales and marketing contacts, top competitors, and firmographic insights. 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. Set initial conditions in the physics to the appropriate dependent model variable names rather than the default 0. If so, see: Knowledgebase 1030: Error: "Out of memory". 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. Perhaps this approach could be adapted to represent your model. Not assigning proper boundary conditions: Especially if you have ports. 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 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. That is, they are tuned to achieve convergence in as many cases as possible. If these settings have been manually changed, you will see a small star symbol on the Solution feature, as shown in the screenshot below. 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. 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. 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. 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. The nature of simulating nature: A Q&A with IBM Quantum researcher Dr. Jamie We've added a "Necessary cookies only" option to the cookie consent popup. The fully coupled and segregated approaches are discussed below. Not entering required material parameters. thanks for reply SGP handled 7 different prints for me at once and they all came out perfectly, in a timely manner. In the extreme case, suppose one wants to model an instantaneous change in properties, such as: The memory requirements will always be lower than with the fully coupled approach, and the overall solution time can often be lower as well. Using this technique systematically, along with the techniques described previously, will usually identify the nonlinearities in the model that are leading to issues. They worked with me. The Auxiliary Sweep can be used to implement ramping of any Global Parameter. listed if standards is not an option). Once the error estimate is small enough, as determined by the convergence criterion (20-16) the software terminates the computations and returns a solution. Can I tell police to wait and call a lawyer when served with a search warrant? Resources and documents are provided for your information only, and COMSOL makes no explicit or implied claims to their validity. Right-click on the Stationary Solver node and add either the Segregated or Fully Coupled feature. 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. 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. A Global Parameter has to be introduced (in the above screenshot, P) and is ramped from a value nearly zero up to one. (Frequency Domain should be the last step) Solve the stationary study then the time dependent study. 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. Tutti i diritti sono riservati. 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. The coupling terms between the different groups are thus neglected. Multiscale Modeling in High-Frequency Electromagnetics. 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. This segregated approach is used by default for most 3D multiphysics models, and the software will automatically segregate the problem into appropriate groups. 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. This case is generally difficult, or impossible, to solve since this material property is non-smooth. 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. 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. P&S Comsol Team: Manuel Kohli, Raphael Schwanninger, Feature: Stationary Solver 1 (sol1/s1) Screenshot showing a Solver Configuration that has been altered. Dun & Bradstreet gathers Office Supplies, Stationery, and Gift Retailers business information from trusted . k(T,P) = 10[W/m/K]*((1-P)+P*exp(-(T-293[K])/100[K])) Consult your product manuals for complete trademark details. 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. I have searched all over comsol forum to fix this stationary solver configuration and still doesn't work because I don't know the logic behind the solver system. Use this parameter to modify the nonlinearity expressions in the model. Changes to these low-level settings from the defaults will usually be quite model- and case-specific. Asking for help, clarification, or responding to other answers. Most multiphysics problems are nonlinear. For example, if there is a temperature-dependent material property such as: Convergence can be poor when the initial values do not provide a good starting point for this iterative approach. replace it with the expression: In such cases it will be particularly helpful to ramp the load gradually in time, from consistent initial values. The default solver for most 3D models is an iterative solver, which is more sensitive to ill-conditioned 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. If it does so, use a finer increment in that range. In this page, we will be sharing some common errors that might occur in Comsol and their solutions. Cooling and Solidification of Metal. Not meshing all the domains. GCRO-DR is a method for Krylov subspace recycling. 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. Your internet explorer is in compatibility mode and may not be displaying the website correctly. Check the solver log to see if the continuation method is backtracking. This approach is used by default for most 1D, 2D, and 2D-axisymmetric models. What are people saying about cards & stationery in Brea, CA? 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. What is the purpose of this D-shaped ring at the base of the tongue on my hiking boots? Segregated approach and Direct vs. The issue here has do with the iterative algorithm used to solve nonlinear stationary models. How can I use it? Nonlinearity ramping is an especially useful technique if any of the nonlinear terms in the model are very abrupt. 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. 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. Such problems must solved in the time domain. Discussion Closed This discussion was created more than 6 months ago and has been closed. k(T) = 10[W/m/K]*exp(-(T-293[K])/100[K]) Examine the model and identify all terms that introduce nonlinearities, such as multiphysics couplings, nonlinear materials relationships, and nonlinear boundary conditions. However, load ramping will not work in all cases, or may be inefficient. Here, we will examine techniques for accelerating the convergence of these two methods. 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. Wrong ordering of study steps. 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. Examine the model and identify all terms that introduce nonlinearities, such as multiphysics couplings, nonlinear materials relationships, and nonlinear boundary conditions. Feature: Stationary Solver 1 (sol1/s1) Adaptation gives the same mesh: adaptmesh1.