stationary solver comsol

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) = 10[W/m/K]*exp(-(T-293[K])/100[K]) For example, if there is a temperature-dependent material property such as: COMSOL makes every reasonable effort to verify the information you view on this page. Using this technique systematically, along with the techniques described previously, will usually identify the nonlinearities in the model that are leading to issues. 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. Consult your product manuals for complete trademark details. 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. 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. When you use an iterative solver, COMSOL Multiphysics estimates the error of the solution while solving. The difference between the phonemes /p/ and /b/ in Japanese. This involves a systematic reduction in the model complexity. Check the solver log to see if the continuation method is backtracking. if I want to do an adaptive mesh refinement, I get this error. 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Posh Paper, Morning Glory, Velvet Fox Designs, Barnes & Noble, Michaels, Select Graphics & Printing This consent may be withdrawn. The exceptions are the Heat Transfer interfaces, which have a default Initial Value of 293.15K, or 20C, for the temperature fields. Have you taken a look at this [blog post](https://www.comsol.com/blogs/modeling-fluid-structure-interaction-in-multibody-mechanisms/)? Here we introduce the two classes of algorithms used to solve multiphysics finite element problems in COMSOL Multiphysics. 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. This case is generally difficult, or impossible, to solve since this material property is non-smooth. Wish you all the best. k(T) = 10[W/m/K]*exp(-(T-293[K])/100[K]) COMSOL makes every reasonable effort to verify the information you view on this page. The coupling terms between the different groups are thus neglected. What is the purpose of non-series Shimano components? Stationary (time-invariant) models with nonlinearities may converge very slowly. 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. Consult your product manuals for complete trademark details. You can fix this by pressing 'F12' on your keyboard, Selecting 'Document Mode' and choosing 'standards' (or the latest version Consult your product manuals for complete trademark details. 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. Using the first order optimality. 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. They are usually called comp1.u, comp1.v, and comp1.w though. What are people saying about cards & stationery in Brea, CA? Find centralized, trusted content and collaborate around the technologies you use most. Once the error estimate is small enough, as determined by the convergence criterion (20-16) the software terminates the computations and returns a solution. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. In such cases, use the same continuation method, but instead ramp the nonlinearities in the model. Your internet explorer is in compatibility mode and may not be displaying the website correctly. 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. In the COMSOL Multiphysics software, this step of the modeling workflow is made. The default Initial Values for the unknowns in most physics interfaces are zero. It can be useful while solving sequences of linear systems arising from, for example, nonlinear problems. Your Discussion has gone 30 days without a reply. 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. Therefore, an initial value of zero is almost always reasonable if a very small load is applied. Solving such models in a stationary sense should simply require solving a single (large) system of linear equations and should always be solvable, but there are cases when the software will fail to find a solution. $131,100.00, Simplified Vehicle Operations Project Engineer, $115,000.00 The issue here has do with the iterative algorithm used to solve nonlinear stationary models. One of the key concepts there was the idea of mesh convergence as you refine the mesh, the solution will become more accurate. The algorithm is, generally speaking, a Newton's method approach. This approach is used by default for most 1D, 2D, and 2D-axisymmetric models. 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. This is useful since the software will then return an estimation of the maximum possible loadcase for which the solver can converge. Then I stored the resulting solution, and used it to to solve the stationary solver again by using the solver manager. This case is generally difficult, or impossible, to solve since this material property is non-smooth. comp1.u2, comp1.v2, and comp1.w2 are usually variables associated with the x,y, and z component of deformation in COMSOL. 3 Replies, Please login with a confirmed email address before reporting spam. Hi Alexis, 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. thanks for reply It is thus always advised to start this procedure with a simplified 2D, or 2D-axisymmetric model. Dr.S.Ravindran Cite 1 Recommendation Popular answers (1). 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. That is, when solving, the software starts with the user-specified initial values to evaluate all solution-dependent terms. To start a new discussion with a link back to this one, click here. If you do not hold an on-subscription license, you may find an answer in another Discussion or in the Knowledge Base. However, it is usually not possible to know this ahead of time. 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. k(T) = 10[W/m/K]+10[W/m/K]*(T>400[K]) The former approach solves for all unknowns in the problem at once, and considers all coupling terms between all unknowns within a single iteration. Feature: Stationary Solver 1 (sol1/s1) Attempt to evaluate nonintegral power of negative number. Discussion Closed This discussion was created more than 6 months ago and has been closed. If you see this, right-click on the Solution feature and select Reset Solver to Default. k(T,P) = 10[W/m/K]*((1-P)+P*exp(-(T-293[K])/100[K])) 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 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. Not meshing all the domains. This guide applies solely to nonlinear stationary models. - Variable: B1 - Defined as: 1/ ( ( (comp1.cH2 (unit_m_cf^3))/unit_mol_cf)^2.5) Failed to evaluate variable. See also: Knowledge Base 1254: Controlling the Time Dependent solver timesteps. 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. The default Initial Values for the unknowns in most physics interfaces are zero. This is useful since the software will then return an estimation of the maximum possible loadcase for which the solver can converge. 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. Communication over the phone, in person, and through email was very easy. Nonlinearity ramping is an especially useful technique if any of the nonlinear terms in the model are very abrupt. Any trademarks referenced in this document are the property of their respective owners. That is, the material property changes instantaneously from 10W/m/K to 20W/m/K at 400K. Consult your product manuals for complete trademark details. Specify Material Properties in COMSOL Multiphysics (3/8) There are two approaches that can be used when iteratively solving the nonlinear system of equations: a Fully Coupled or a Segregated approach. 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. This approach is used by default for most 1D, 2D, and 2D-axisymmetric models. If so, see: Knowledgebase 1030: Error: "Out of memory". What is the purpose of this D-shaped ring at the base of the tongue on my hiking boots? That is, when solving, the software starts with the user-specified initial values to evaluate all solution-dependent terms. 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. The conditions on the geometric aspect ratio are relatively more strict. 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. Feature: Stationary Solver 1 (sol1/s1) Adaptation gives the same mesh: adaptmesh1. A classic example of this is fluid flow around a cylinder with high, but constant, flow rates. See Knowledge Base 1240: Manually Setting the Scaling of Variables. If your matrix is singular than no solver in the world can solve Ax=B. Minimising the environmental effects of my dyson brain. It is sometimes necessary to manually scale the dependent variables. 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. 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. Such problems must solved in the time domain. Reviews on Stationary Stores in Brea, CA - Typo, Mievic, Posh Paper, Morning Glory, Select Graphics & Printing, Daiso Japan, Urban Outfitters, Office Depot, Barnes & Noble Stationary Solver - COMSOL Multiphysics Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Building on these topics, we will now address how to prepare your mesh for efficiently solving nonlinear finite element problems. Ideally, one would use small elements in regions where the solution varies quickly in space, and larger elements elsewhere. Nonlinearities arise as a consequence of the governing equation, as a material nonlinear expression, or as a coupling term between physics. 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. Stationary Engineer Jobs in Brea, California, United States, $87,400.00 If both load ramping and nonlinearity ramping are still leading to slow convergence, refine the mesh. We are planning to continuously update this page throughout the semester and hopefully, this will become a reference during your projects as well. Stationary (time-invariant) models with nonlinearities may converge very slowly. Screenshot showing a Solver Configuration that has been altered. 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. Instead, use a nonlinear material property expression that ramps from a very smooth function to a very nearly discontinuous one. Discussion Closed This discussion was created more than 6 months ago and has been closed. 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. Linear solvers. What version of COMSOL are you using? Does ZnSO4 + H2 at high pressure reverses to Zn + H2SO4? Nonlinearities arise as a consequence of the governing equation, as a material nonlinear expression, or as a coupling term between physics. This can arise as a consequence of extreme variations in the material properties, or high aspect ratio geometry. COMSOL does not assume any legal liability for the accuracy of the data disclosed. 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. 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. Use a manually defined mesh to avoid elements with extreme aspect ratios and perform a mesh refinement study, as described here: Performing a Mesh Refinement Study, For problems that are ill-conditioned, using a direct solver is often called for. 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. The Fully Coupled solution approach, with the Plot While Solving enabled. Tutti i diritti sono riservati. Trying to understand how to get this basic Fourier Series. Nonlinearity ramping is an especially useful technique if any of the nonlinear terms in the model are very abrupt. A Global Parameter has to be introduced (in the above screenshot, P) and is ramped from a value nearly zero up to one. k(T,P) = 10[W/m/K]*((1-P)+P*exp(-(T-293[K])/100[K])) 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. Any trademarks referenced in this document are the property of their respective owners. Posted 26 set 2019, 17:57 CEST Mesh Version 5.3 0 Replies. 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. 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. 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. 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 P is ramped up, the continuation method uses the previous solutions to compute initial conditions for the more nonlinear cases. Despite this, the segregated approach can often converge very robustly, unless there are very strong couplings between the physics in the 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. Solving for laminar flow using Comsol - YouTube 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. Not assigning proper boundary conditions: Especially if you have ports. Each physics is thus solved as a standalone problem, using the solution from any previously computed steps as initial values and linearization points. Does anyone know what should cause this problem? The default Initial Values for the unknowns in most physics interfaces are zero. Get email updates for new Stationary Engineer jobs in Brea, California, United States. 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. 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. We use COMSOL Multiphysics for solving distributed optimal control of un-steady Burgers equation without constraints and with pointwise control constraints. Not entering required material parameters. Use either a very fine mesh throughout the simulation domain or use adaptive mesh refinement. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. An example model that combines the techniques of nonlinearity ramping and adaptive mesh refinement with multiple study steps is: To switch between these solver types, go to the Stationary Solver node within the Study sequence. The Auxiliary Sweep can be used to implement ramping of any Global Parameter. Ramping the nonlinearities over time is not as strongly motivated, but step changes in nonlinearities should be smoothed out throughout the simulation. 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 instead the model is linear, see: Knowledgebase 1260: What to do when a linear stationary model is not solving. 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. 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. See Knowledge Base 1240: Manually Setting the Scaling of Variables. To learn more, see our tips on writing great answers. First, it is physically intuitive, often matching how one would perform an experiment. The Continuation method is enabled by default when using the Auxiliary sweep study extension, as shown below. 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. How do/should administrators estimate the cost of producing an online introductory mathematics class?