But after I added moving mesh, the initial condition changed to the value of surface concentration across the simulation … Please login with a confirmed email address before reporting spam. Initial condition provided do not match solvers initial solution. This means that the initial conditions and boundary condition should be defined using relative pressure values. Concentric Tube Thin Resistive Layer Interface Question read 0 Replies 83 Views. Send Private Message Flag post as spam. Tan Chun Wei . CONTENTS| 5 Interfaces 102 The Rotating Machinery, Laminar Flow Interface . . Send Private Message Flag post as spam. Circulation generated from fan blades. 102 The Rotating Machinery, Turbulent Flow, Algebraic yPlus Interface . The number of increments may need to quite large, and you will want to monitor at what values of the ramping factor there is slow convergence of the solver. Send Private Message Flag post as spam. . 4. Über die COMSOL-Produktpalette. . Unless there are some mechanical properties … 2012 г., 10:14 GMT-8 Geometry, Modeling Tools, Parameters, Variables, & Functions Version 4.0a 1 Reply Raju Purohit Assume that you want the traveling spot to prescribe the temperature as exactly 450 K. This may be a bit artificial, but it displays an important difference between the Neumann condition and the Dirichlet condition… Posted 24 мар. Posted 24 июл. 2.3 Setting up Initial Conditions from Data Files The initial condition profiles for the excitation variable, C 0(x,y), and recovery variable, v 0(x,y), are provided in two separate txt files. Using dirac delta function as an initial condition. Boundary conditions in fluid dynamics are the set of constraints to boundary value problems in computational fluid dynamics.These boundary conditions include inlet boundary conditions, outlet boundary conditions, wall boundary conditions, constant pressure boundary conditions, axisymmetric boundary conditions, symmetric boundary conditions, and periodic or cyclic boundary conditions. Aaron Shifman . Subhra Paul . Initial condition drift when sequencing COMSOL through Matlab. 6. Initial stress and strain are there to have non zero values at first solver step, but you can also "build" them up by a first static analysis, and then restart from there for further processing. 2016 г., 14:19 GMT-4 Fluid, Computational Fluid Dynamics (CFD), Modeling Tools, Parameters, Variables, & Functions, Studies & Solvers Version 5.1 4 Replies Please help. Posted 29-Jun-2010, 2:41 pm GMT-7 4 Replies . Die COMSOL Multiphysics ® Software bietet eine Benutzeroberfläche und eine User-Experience, die unabhängig vom Anwendungsbereich und physikalischen Phänomenen immer gleich ist.. Zusatzmodule bieten spezialisierte Funktionalität für Elektromagnetik, Strukturmechanik, Akustik, Strömung, Wärmetransport und chemische Verfahrenstechnik. The "Values for dependent values" in study step settings should be set to the default ("Physics-controlled" in 5.2). Posted 6 okt. Set the time series 2 Dependent variables to use the stored solution as initial conditions. However, the solution starts at P=0 for t=0. . Technically the volume is increased without force and the pressure in that reservoir is zero. . Mauricio Pedroza . If you need to specify more than one set of initial values, you can add additional . Dmitri Hennion . Send Private Message Flag post as spam. This is for COMSOL 5.2, but should be similar for 4.2: Create the stationary study. Equations for such degrees of freedom can thus be eliminated from the problem. Problem in assigning boundary and initial conditions Posted 11 февр. Across the interface, there is a smooth transition from zero to one. of blod is usually 37°C, no need to start at 0°K, otherwise you need some extra time to get to the equilibrium first. Comsol will then run for another period of time and will once again transfer its results back to matlab for modification and so on and so forth. This usually involves evaluating a number of derivatives. . Please login with a confirmed email address before reporting spam Hi, I have a time-dependent study. In the past decade, computer software has become very powerful, and this allows chemical engineers to solve very complicatedproblems.Thisposesaproblemthough:youmaybetemptedtoposeaproblem that is way more … When utilizing the gravity option, an important concern is the need for consistent boundary conditions and initial values, particularly when dealing with natural convection simulations. Note: This discussion is about an older version of the COMSOL Multiphysics ... And, I am trying to define inital condition of one box by previous solution, the other box by defining from initial values node. . Send Private Message Flag post as spam. This will use the initial conditions you specified in your physics setting (usually 0 is used in the physics settings). Hi, I am a new user with COMSOL. In the mathematical treatment of partial differential equations, you will encounter boundary property of their respective owners, and COMSOL AB and its subsidiaries and products are not affiliated with, endorsed by, sponsored by, or supported by those trademark owners. . COMSOL Moderator. For a list of such trademark Posted 14-Aug-2014, 4:29 pm GMT-4 Studies & Solvers Version 4.4 5 Replies . Please login with a confirmed email address before reporting spam . Posted 14 мар. Coupled PDEs with Initial Solution from Data in COMSOL 4 X. Huang, ... the initial condition is in the form of 2 × 1 vector with C 0(x,y) and v 0(x,y) as the elements. –Initial conditions ,0= ... • Most of COMSOL (and other tools’) physics use such a formulation since most versatile • It is the base of finite element (but also used within other schemes) • Understanding how it works is the way to master what COMSOL does under the hood + F dV³ F dV: : Q + Q. The "Values for dependent values" in study step settings should be set to the default ("Physics-controlled" in 5.2). Initial Values . COMSOL Multiphysics solves CFD problems using relative pressure to improve the numerical accuracy of the pressure field. These conditions will be modified inside of matlab and will then be sent back to comsol as the new initial conditions. I checked it with "Compute to Selected" under "Solver/Variables". . property of their respective owners, and COMSOL AB and its subsidiaries and products are not affiliated with, endorsed by, sponsored by, or supported by those trademark owners. Greg Fleischman . In many cases we need to break a simulation into smaller parts. . Thanks. Send Private Message Flag post as spam. Note: This discussion is about an older version of the COMSOL Multiphysics ... To start a new discussion with a link back to this one, click here. Initial Values. property of their respective owners, and COMSOL AB and its subsidiaries and products are not affiliated with, endorsed by, sponsored by, or supported by those trademark owners. Automatize the ''initial conditions from previous solution'' process. feature adds an initial value for the level set function that can serve as an initial condition for a transient simulation. R. White, Comsol Acoustics Introduction, © 2012 So, this is always the sequence for any FEA problem: 1. Decide on the representative physics (choose the PDE). 2. Define the geometry on which to solve the problem. 3. Set the “material properties”… that is, all the constants that appear in the PDE. 4. In rectangular coordinates, the initial condition can be the initial temperature field specified in the general form as: where the function f(x, y, z) represents the temperature field inside the material at … But I found that the initial value of whole geomtry is defined by the previous solution. In COMSOL Multiphysics, is a smooth step function that equals zero in a domain and one in the other. The COMSOL discussion forum covers a wide variety of simulation topics. 4. Post-process the results to find the information you want. If you know the initial values, i.e. Add a store solution to position in between. A fan with airflow around it. COMSOL Multiphysics ® designed to assist you to solve and model low-frequency electromagnetics. This could be a nontrivial task since a domain force, the buoyancy force, is working inside the system, and we need to account for its presence. Fernando Diego Engels Crespo . Posted Sep 7, 2011, 6:45 AM PDT Heat Transfer & Phase Change 2 Replies . Figure 7-4 shows the level set representation of the interface in Figure 7-3. Note: This discussion is about an older version of the COMSOL Multiphysics ... click here. As we can see from the plot below, if we choose any initial condition u_0\le-1 , the Newton-Raphson method cannot find a solution since the derivatives of f(u) do not point towards the solution. features. Decide on the representative physics (choose the PDE). 2. Define the geometry on which to solve the problem. 3. Set the “material properties”… that is, all the constants that appear in the PDE. 4. Set the boundary conditions (for static or steady state problems) and initial conditions (for transient problems). 5. initial condition for heat transfer simulation. In the past decade, computer . Choose an element type and mesh the geometry. In fact, there is really nothing to add to these techniques — they … Initial conditions (steady state) to time dependent model. Dirichlet conditions therefore change the structure of the stiffness matrix. This is for COMSOL 5.2, but should be similar for 4.2: Create the stationary study. . I have provided an initial condition of 1 atm and boundary condition of 1 atm on the outer boundaries. I think you just have to define another wall as an open boundary, or as an outlet and set the pressure there to be 0. The . How do I take advantage of the symmetries in my COMSOL model? –Initial conditions ,0= ... • Most of COMSOL (and other tools’) physics use such a formulation since most versatile • It is the base of finite element (but also used within other schemes) • Understanding how it works is the way to master what COMSOL does under the hood + F dV³ F dV: : Q + Q. Hi, I'm new with Comsol and I have a question about the initial conditions in a time dependent study. Initial Values. property of their respective owners, and COMSOL AB and its subsidiaries and products are not affiliated with, endorsed by, sponsored by, or supported by those trademark owners. I am using Darcy's law for solving for pressure. Averaged total pressure conditions are imposed on the inlet and outlet boundaries. in V4 you add a stationary study-solving node before your time dependent node, and COMSOL will link them and use the stationary case as initial conditions (if you have tweaked your solver sequence, you should regenerate a new "default" one to get the solver sequence correctly updated by COMSOL. Setting temperature initial condition at specific location. Time-Dependent initial solution violates specified initial conditions. 2012 г., 07:25 GMT-4 0 Replies . . Although this algorithm does converge well for many cases, it can fail or converge very slowly if the choice of initial conditions are poor. Please login with a confirmed email address before reporting spam. . For a list of such trademark 1 Reply Last Post 2012年3月21日 GMT-4 上午2:45. How to recover the initial and boundary conditions from a result in comsol? About the Various Turbulence … Note that while COMSOL employees may participate in the discussion forum, ... Failed to find consistent initial values. This will use the initial conditions you specified in your physics setting (usually 0 is used in the physics settings). 2011 02:05 GMT−7 Fluid, Heat Transfer & Phase Change, Studies & Solvers Version 4.2 0 Replies . CONTENTS| 5 Interfaces 102 The Rotating Machinery, Laminar Flow Interface . Moreover, such equations may be coupled in an almost arbitrary way. Harmke van der Velde . User’s Guide Contact Information Visit the Contact COMSOL page at www.comsol.com/contact to submit general inquiries, contact Technical Support, or search for an address and phone number. You can also visit the Worldwide Sales Offices page at www.comsol.com/contact/offices for address and contact information. The interface is defined by the 0.5 isocontour, or the level set, of . Send Private Message Flag post as spam. Start Time Dependent Study With Initial Conditions From A Time Dependent Solution. Post-process the results to find the information you want. COMSOL Multiphysics ® version 5.6 includes options for imposing either pointwise values or average values of the total pressure on inlets and outlets for incompressible flow. window contains the following sections: DOMAINS 2.3 Setting up Initial Conditions from Data Files The initial condition profiles for the excitation variable, C 0(x,y), and recovery variable, v 0(x,y), are provided in two separate txt files. All turbulence models in COMSOL Multiphysics, except the k-ε model, support automatic wall treatment. Last time step is not converged read 0 Replies 838 Views. Posted 1 juil. . Set the boundary conditions (for static or steady state problems) and initial conditions (for transient problems). 5. Reg Initial Condition in Transient solver. This means that the low Reynolds number models can be used for industrial applications and that their low Reynolds number modeling capability is only invoked when the mesh is fine enough. Initial Values. Version 5.0 AC/DC & Electromagnetics General Shreyam Natani posted 4 years ago. Before answering the above question, let’s first consider the definition of a boundary By default, the Continuation Method will be used, which uses the solution from the previously solved step as the initial condition for the next step, thereby easing convergence. Case 1: The Initial Condition is Too Far Away from the Solution First, consider the same nonlinear problem as before, but with a different starting point, for example, u_0=-2 . Please login with a confirmed email address before reporting spam. It should come as no surprise then that the techniques we have already looked at, such as Load Ramping and Nonlinearity Ramping, are just as valid when applied to a multiphysics problem. Thanks. Choose a solver and solve for the unknowns. COMSOL, the COMSOL logo, COMSOL Multiphysics, COMSOL Desktop, COMSOL Server, and LiveLink are either registered trademarks or trademarks of COMSOL AB. For a list of such trademark 0 Replies Last Post Mar 20, 2012, 4:39 AM EDT. Version 4.2a Fluid Heat Transfer & Phase Change … Posted 6 feb. 2013 08:53 GMT−8 Fluid, Heat Transfer & Phase Change, Computational Fluid Dynamics (CFD), Subsurface Flow, Studies & Solvers Version 4.3 0 Replies Figure 7-3: Example of two domains divided by an interface. Browse the threads and share your ideas with the COMSOL community. u = f{\text{ initial condition}} \hfill \\ Bu = g{\text{ boundary condition}} \hfill \\ \end{gathered} $ Here, P denotes a differential operator, u the dependent variable (the solution variable), F a source, f a function that describes the initial condition, B an operator, and g a function at the boundary. The whole initial condition was defined from just previous value. In HT2 I have 2 initial conditions, one for T from first "ht" and the second for the "steak". The . For a list of such trademark We will soon see how the symbolic algebra routines in COMSOL Multiphysics can help with this process. When looking in the Equation View of COMSOL Multiphysics, these conditions will appear as constraints. Choose an element type and mesh the geometry. The default Initial Valuesfor the unknowns in most physics interfaces are 2020 10:43 GMT−4 RF & Microwave Engineering, General, Introduction 1 Reply . A common mistake when setting up transient models is to have initial conditions that are inconsistent with the loads and boundary conditions. Using symmetries in COMSOL Multiphysics Solution Number: 1038 Versions: All versions. 2019 г., 03:59 GMT-7 Fluid, Microfluidics Version 5.4 0 Replies Fluid, Microfluidics Version 5.4 0 Replies COMSOL MULTIPHYSICS® This appendix gives an introduction to the use of Comsol Multiphysics. Posted 20 nov 2013, 01:40 GMT-5 MEMS & Nanotechnology, MEMS & Nanotechnology, Microfluidics, Studies & Solvers Version 4.3a 0 Replies . 7. 7. The program Comsol Multiphysics,1 uses the finite element method to solve fluid flow, heat transfer, and mass transfer problems, as well as many other equations. The combined formulations are then used for the boundary conditions. Initial conditions (problem) - Fluid Structure Interaction. 2015 à 16:57 UTC−4 RF & Microwave Engineering, Interfacing, Heat Transfer & Phase Change, Studies & Solvers Version 5.1 0 Replies . Set the boundary conditions (for static or steady state problems) and initial conditions (for transient problems). Comsol 4: using simulation results as an initial condition to next simulation. . . 1) set two time series, one for "ht" only, one for "ht2" alone. Please login with a confirmed email address before reporting spam. When the moving mesh (ALE) was not added, I can set up a very narrow Gaussian initial profile at the lower boundary. Please login with a confirmed email address before reporting spam. initial conditions for time dependent study. Then, we substitute the solution to the differential equations and obtain a consistent set of source terms, initial conditions, and boundary conditions. Send Private Message Flag post as spam. The boundary conditions are Dirichlet type, 500mol/m^3 at surface and zero at the right boundary. Choose a solver and solve for the unknowns. Use more increments when the convergence is slow. Shimon Cohen . Comsol Multiphysics,1 uses the finite element method to solve fluid flow, heat transfer, and mass transfer problems, as well as many other equations. 5. Posted 6 июн. Initial condition in transient simulation for electromagnetic problem Posted 18 set 2011, 19:15 GMT-7 Studies & Solvers Version 3.5a 0 Replies Subhra Paul Posted 20.9.2010 klo 10.48 UTC-7 0 Replies . . I am trying to emulate a situation where a PCB with some chips on it are working for a long time under … 1 Introduction to COMSOL Multiphysics 1.1 Basic Information Comsol Multiphysics is an integrated software environment designed to solve systems of time-dependent or stationary second order in space partial differential equations (PDEs) in one, two, and three dimensions. 6. Coupled PDEs with Initial Solution from Data in COMSOL 4 X. Huang, ... the initial condition is in the form of 2 × 1 vector with C 0(x,y) and v 0(x,y) as the elements. Posted 7 okt. This chapter introduces you to the capabilities of the module including an Boundary conditions in fluid dynamics are the set of constraints to boundary value problems in computational fluid dynamics.These boundary conditions include inlet boundary conditions, outlet boundary conditions, wall boundary conditions, constant pressure boundary conditions, axisymmetric boundary conditions, symmetric boundary conditions, and periodic or cyclic boundary conditions. Please help. 102 The Rotating Machinery, Turbulent Flow, Algebraic yPlus Interface .