stationary solver comsol

Cooling and Solidification of Metal. Perhaps this approach could be adapted to represent your model. 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. What is the purpose of this D-shaped ring at the base of the tongue on my hiking boots? listed if standards is not an option). For example, if there is a temperature-dependent material property such as: Get notified about new Stationary Engineer jobs in Brea, California, United States. 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. They are usually called comp1.u, comp1.v, and comp1.w though. I personally liked emailing them the file, ", "This flower shop is the best! Tutti i diritti sono riservati. 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. -Detail: NaN or Inf found when solving linear system using SOR. Why is there a voltage on my HDMI and coaxial cables? Any trademarks referenced in this document are the property of their respective owners. Convergence can be poor when the initial values do not provide a good starting point for this iterative approach. 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. It is thus always advised to start this procedure with a simplified 2D, or 2D-axisymmetric model. In the extreme case, suppose one wants to model an instantaneous change in properties, such as: She opened prepackaged 6-packs of Seegars to make ", All "stationary stores" results in Brea, CA, Search stationary stores in popular locations. A Global Parameter has to be introduced (in the above screenshot, P) and is ramped from a value nearly zero up to one. GCRO-DR is a method for Krylov subspace recycling. Changes to these low-level settings from the defaults will usually be quite model- and case-specific. 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. (I am begginer in comsol) Thank you. Any trademarks referenced in this document are the property of their respective owners. There are two approaches that can be used when iteratively solving the nonlinear system of equations: a Fully Coupled or a Segregated approach. Dun & Bradstreet gathers Office Supplies, Stationery, and Gift Retailers business information from trusted . The settings controlling the predictor type. 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. This algorithm was also useful for understanding what happens near a failure load. Function: / Failed to evaluate expression. - Variable: B1 - Defined as: 1/ ( ( (comp1.cH2 (unit_m_cf^3))/unit_mol_cf)^2.5) Failed to evaluate variable. The solver settings are stored at Study > Solver Configurations > Solution. If a good estimate to the solution field is known, this can be entered as an an expression in the Initial Value field. 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 fully coupled and segregated approaches are discussed below. However, load ramping will not work in all cases, or may be inefficient. 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. If you are unsure if your problem is linear and stationary, look at the Log. If a good estimate to the solution field is known, this can be entered as an an expression in the Initial Value field. Does ZnSO4 + H2 at high pressure reverses to Zn + H2SO4? To start a new discussion with a link back to this one, click here. With the exception of some thermal problems however, it is often difficult to estimate the solution, so alternative approaches are needed. 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. Hi ! Such problems must solved in the time domain. First, it is physically intuitive, often matching how one would perform an experiment. This guide applies solely to nonlinear stationary models. Each physics is thus solved as a standalone problem, using the solution from any previously computed steps as initial values and linearization points. 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. 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. P&S Comsol Team: Yannik Horst, Manuel Kohli, Xinzhi Zhang. 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. Such a large difference in the materials properties can be challenging. Note the star symbol on the Solution feature. Ideally, one would use small elements in regions where the solution varies quickly in space, and larger elements elsewhere. 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. 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. 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. Use this parameter to modify the nonlinearity expressions in the model. Check the solver log to see if the continuation method is backtracking. That is, when solving, the software starts with the user-specified initial values to evaluate all solution-dependent terms. Communication over the phone, in person, and through email was very easy. - Feature: Stationary Solver 1 (sol1/s1)Failed to find a solution. Your email address will not be published. This involves a systematic reduction in the model complexity. Not the answer you're looking for? Your internet explorer is in compatibility mode and may not be displaying the website correctly. Under Initial values of variables solved for, the default value of the Settingslist is Physics controlled. The default solver for most 3D models is an iterative solver, which is more sensitive to ill-conditioned problems. If instead the model is linear, see: Knowledgebase 1260: What to do when a linear stationary model is not solving. Understanding the Fully Coupled vs. Not meshing all the domains. I highly recommend this flower shop. Right-click on the Stationary Solver node and add either the Segregated or Fully Coupled feature. k(T) = 10[W/m/K]+10[W/m/K]*(T>400[K]) Near the top of the Stationary Solver log, the software will report if a linear or nonlinear solver is being used. 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. . Reply . Full text of the 'Sri Mahalakshmi Dhyanam & Stotram'. In such cases, see if one material (or the other) can be omitted from the analysis completely. To switch between these solver types, go to the Stationary Solver node within the Study sequence. k(T,P) = 10[W/m/K]*((1-P)+P*exp(-(T-293[K])/100[K])) Resources and documents are provided for your information only, and COMSOL makes no explicit or implied claims to their validity. 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. Perhaps this approach could be adapted to represent your model. See if these can be used instead of explicitly modeling parts with high-aspect ratio geometries. We use COMSOL Multiphysics for solving distributed optimal control of un-steady Burgers equation without constraints and with pointwise control constraints. Stationary (time-invariant) models with nonlinearities may converge very slowly. The objective here is to simplify the model to a state where the model will solve, with linear approximations. Check the solver log to see if the continuation method is backtracking. 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. Your internet explorer is in compatibility mode and may not be displaying the website correctly. replace it with the expression: The Auxiliary Sweep can be used to implement ramping of any Global Parameter. Here, we begin an overview of the algorithms used for solving nonlinear static finite element problems. Click the link in the email we sent to to verify your email address and activate your job alert. "After the incident", I started to be more careful not to trip over things. New Stationary Engineer jobs added daily. Segregated approach and Direct vs. See also: Knowledge Base 1254: Controlling the Time Dependent solver timesteps. This case is generally difficult, or impossible, to solve since this material property is non-smooth. For example, if there is a temperature-dependent material property such as: In such cases it will be particularly helpful to ramp the load gradually in time, from consistent initial values. The default Initial Values for the unknowns in most physics interfaces are zero. From there, if an additional small load increment is applied, the previously computed solution is a reasonable initial condition. As a rough rule of thumb, once the aspect ratio between the largest characteristic dimension to the smallest approaches 100:1, you might start to run into issues and should look to alternative ways of posing the problem, especially in a 3D model. COMSOL does not assume any legal liability for the accuracy of the data disclosed. This case is generally difficult, or impossible, to solve since this material property is non-smooth. 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 Fully Coupled solution approach, with the Plot While Solving enabled. Could you expand a little bit more why the coupling is impossible? 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.