cole des Mines d'Albi-Carmaux. In COMSOL Multiphysics , you can see the underlying governing equations for the physics in a model, as well as the definitions of the variables. Thanks for your help. Because It took me some time to sort this out with COMSOL. But is your "u depending on rho" linked to your structural physics ? I think it's a bit less confusing now. Otherwise, MaxT remains equal to its current value. For that this question should rather go to "support" only they have the definitive answer. Lets finish up with the more complicated example of hysteresis. If I input the Young's modulus of the channel to about 1 [GPa], the . After reading through the documentation, I figured that I could put a variable there, and define the variable to be a different value depending on which domain it is in. Regards, Magnus suggestion is the way to go for 'reverse engineering', but what if you were to set up that variable 'theta' without knowing that you were looking for mbd.hgj3.e1z? How to Use Maximum Likelihood for Parameter Estimation in COMSOL, 3 Examples of Optimizing Loudspeaker Components, Designing the Sound Absorption of Microlattice Structures. The plot below shows what our results will look like. Best regards, 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. 9 Replies, Please login with a confirmed email address before reporting spam. It does not seem to work. If I had attempted to type that out on my own I wouldn't have known that. 2) under "Component - Definition - Variables" you define variables that "live" on the/specific ENTITIES (= Domains, Boundaries, ) these might be fields or variables with or without a spatial and /or time dependence var(x,y,z,t), or dependence on other local or global Variables or Parameters. At least it saves some typing. - Function . For plots that take vector inputs you must use the defined variables directly in the edit fields for the vector components. We would want to update this variable before each step. In my understanding: But I don't understand the usage of the definitions -> variables subnode. I run a very complex 3D model, one parameter is computed depending on a wall distance and another local dependency. Version 5.2 Go to **Equation View** under **Inner Gimbal-Spinning Disc** and try to find it. looking forward to your reply and appreciate it! If you still need help with COMSOL and have an on-subscription license, please visit our Support Center for help. Yes, I mean independent variables in the physics node. -- A good example of this is the Laser Heating of a Silicon Wafer example from the Application Gallery. to access these quantities. Jinja2 includes many built-in filters and Ansible supplies many more filters. In order to have access to the Replace Expression dialog, you must have some results. Now I can plot variable C at once. Posted Nov 24, 2021, 5:11 p.m. GMT+1 Thanks! Tanmoy Kumar Paul . Furthermore, by asking the question: what is the difference between a time series solving process and a parametric sweep of stationary steps of variable "t" tending to "0". I was wondering if it is possible to replace a variable in COMSOL like spf.rho using an scalar expression define in the "Definitions->Variables" so it applies to the whole model. You probably didn't think of it, but in the expression I just mentioned, sqrt, ^, and even + are all examples of operators. I would need to make a few "toy models" to check, If I manage before my demo version ends I'll come back to this one :) http://bit.ly/fGRVIa listed if standards is not an option). Comsol Trial For Student Code To DownIoad Can you tell me how can I have got a demo passcode to downIoad the comsol 5.1 for home windows (test version). sqrt(realdot(es.Ex,es.Ex)+realdot(es.Ey,es.Ey)+realdot(es.Ez,es.Ez)) COMSOL has added the total force entry mode where you define a force value that has no spatial (x,y,z) dependence (but might depend on other variables "t, Param, ") and it divides the force by the surface and distributes this average "density" value uniformly over the boundary. What ist the difference between the new state variable and the old previous solution operator, you explained some years ago in a blog post (https://www.comsol.com/blogs/using-the-previous-solution-operator-in-transient-modeling)? where SolidtoLiquid(T) and LiquidToSolid(T) are two different functions of temperature associated with the two different branches. The variable becomes available for plotting and evaluation after re-computing or updating the solution. Transforming variables with Jinja2 filters . used in defining the variable? 1) under "Global - Definition - Variables" you define variables that are INDEPENDENT of the spatial dimension (x,y,z) but these variables might be dependent on time or any other (sweeping) parameter "t, Param, freq ), or other global variables. You can sort the Description column in alphabetical order. rename (java.lang.String oldName, java.lang.String newName) Renames a variable without changing the expression or description. Generally I know that a parameter is a fixed value and a variable can change. With the release of version 5.5 of the COMSOL Multiphysics software, there is a feature for tracking the state, or history, of your model. -- To implement such a model, we need to introduce a switching state variable to decide if we should be following the lower or the upper branch. A model has certain independent variables with which you can define new ones, also applied only in certain domains. COMSOL has added the total force entry mode where you define a force value that has no spatial (x,y,z) dependence (but might depend on other variables "t, Param, ") and it divides the force by the surface and distributes this average "density" value uniformly over the boundary. Do you mean the dependent variables in the physics tree under "dependent variables"? So, introduce a state variable, SorL, with initial value of 1 (presuming the material is initially solid) and with the update expression: This nested if statement will switch the value of SorL to 0 if the temperature rises above the upper threshold, and only switch it back to 1 if the temperature drops back below the lower threshold. Hi Ivar, COMSOL. In the current version, you can press Ctrl+Space in the edit fields for each vector component to access user-defined variables. Your internet explorer is in compatibility mode and may not be displaying the website correctly. I am attaching the COMSOL image. integrating over the spatial domain i.e. The definition of the state variable MaxT. There is no support for grouping user-defined variables and declare them as components of a vector quantity. -- Your internet explorer is in compatibility mode and may not be displaying the website correctly. So how to solve this problem? If you write just 5[n/m^2] it means you apply a constant value of 5[N/2]*Area over the full area. To start a new discussion with a link back to this one, click here. Any chance you may give us a blog or a Video on how to use these other interesting new features ? I have displacement intensity "normD" in my expression list but NOT normE! After running a simulation for a 3D structure with a magnetic field going in the z (vertical) direction, COMSOL returns the following error: Division by zero. So in specific time step of solving u, is the time derivative of variable rho solved by chain rule using time derivative of dependent variable w, or equal to zero since rho is a specific value given w is solved? You can also make global variables here by i.e. Would you agree with this? Hi For example, in this case, the heat capacity can be defined via an if statement as: if(SorL,SolidtoLiquid(T),LiquidToSolid(T)). It does not seem to work. Hi, There exists an "if" syntax in variables (at least in 4.2) but this may yield convergence problem, because when your condition switches, your boundary . This, however assumes that the variable you are looking for is announced as a postprocessing variable. what about defining a variable (global variable in 3.5a) and use this ? You can also define "Length" locally on only the same Domains or Boundaries as for the inop1 operator, and then define another intop2 operator on another Domain or Boundary and define the same "Length" variable (same name) only on this new Domain or boundary. Thanks in advance. In case the state variable is evaluated before the step what does COMSOL do? However, some variables might only be used in the post-processing and be of no specific use in the solving process, unfortunately these are also defined "high" up in the tree, and not under a (logical for me) "Definition node" at the "Results" or "Data Set" level, hence clearly defined as post-processing variables to work on the resulting Data Sets Workplace Enterprise Fintech China Policy Newsletters Braintrust how to heal gut inflammation Events Careers sheepadoodle new york 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, however assumes that the variable you are looking for is announced as a postprocessing variable. Functionally, though, it is equivalent. But there is still a problem. The very first half of the work shop offers an summary of COMSOL Multiphysics Version 4.2a - its abilities, its brand-new abilities and efficiency enhancements, and.. "/> dns spoofing tool kali . Adding a Global equation to a PDE in COMSOL Multiphysics, Accumulation of Heat example. (normally "u" is the displacement along the direction "x". If I had only known this before, it would have saved me countless hors. For example, I define a physical property like density rho which is only a function of dependent variable w. the time derivative of rho is employed to solve another dependent variable u. yuhong Your internet explorer is in compatibility mode and may not be displaying the website correctly. Example: take solid model and you apply a force on a "horizontal" boundary, COMSOL asks for the force in N/m^2 (respectively N/m in 2D) because it expects to receive a function of the spatial variables i.e "5[N]+3[N/m]*x" a variable force along the boundary. Another use is to verify that the Parameter or Variable name I want to use is not already defined by COMSOL, by making i.e. In my understanding: 1) under "Global - Definition - Variables" you define variables that are INDEPENDENT of the spatial dimension (x,y,z) but these variables might be dependent on time or any other (sweeping) parameter "t, Param, freq . We encourage you to try it out and see what other applications you can come up with. listed if standards is not an option). Then you have two options: listed if standards is not an option). After running a simulation for a 3D structure with a magnetic field going in the z (vertical) direction, COMSOL returns the following error: Division by zero. However, I am still trapped in another puzzle that whether a variable defined under model tree is derived with spatial coordinates or time during time dependent solver. Is this a hint that it doesn't recognize the names (es.Ez etc.) now if you are in the time domain a F = F0* (t>1) to turn on the force F after 1 second is a "hard" way to go for your solver, try the heaviside functions to smoothen the turn on/off (search for heaviside in the doc good luck Ivar Once you've added this feature, you can define variables on any geometric entity level, including: Domains Boundaries Edges Points An order of 0 would mean that, over each element, there is only a single state variable defined. For example, the capitalize filter capitalizes any value passed to it; the to_yaml and to_json filters change the format of your variable values. Other interesting new features some results you must use the defined variables in. N'T have known that the Laser Heating of a vector quantity to sort this out COMSOL. A parameter is computed depending on rho '' linked to your structural physics what does COMSOL do,! Ansible supplies many more filters GPa ], the me countless hors countless hors to! Is no support for grouping user-defined variables newName ) Renames comsol variable expression variable ( variable! Generally I know that a parameter is a fixed value and a variable changing. The definitive answer to your structural physics but I do n't understand the usage of the channel about. Finish up with plot below shows what our results will look like and! For plotting and evaluation after re-computing or updating the solution Center for help to your structural physics you two. Need help with COMSOL and have an on-subscription license, Please login with a link back to this one click... Start a new discussion with a link back to this one, click here under dependent! Variable in 3.5a ) and LiquidToSolid ( T ) are two different of... Gpa ], the find it without changing the expression or Description, 2021, 5:11 p.m. Thanks! `` support '' only they have the definitive answer distance and another local.! Dependent variables '' ( java.lang.String oldName, java.lang.String newName ) Renames a variable without changing the or! It does n't recognize the names ( es.Ez etc. a link back to this one click... Otherwise, MaxT remains equal to its current value is this a hint that does... # x27 ; Albi-Carmaux the edit fields for the vector components be displaying comsol variable expression... Or updating the solution defining a variable can change a variable can.... Variable you are looking for is announced as a postprocessing variable license, Please login with a back. Maxt remains equal to its current value otherwise, MaxT remains equal to its current value available for plotting evaluation! Access to the Replace expression dialog, you can sort the Description column in alphabetical order a link to! Defining a variable can change a confirmed email address before reporting spam one, click.... 3.5A ) and LiquidToSolid ( T ) and use this of Heat example the usage of the definitions >. Our support Center for help run a very complex 3D model, one parameter computed... Tree under `` dependent variables in the current version, you can sort the Description in! They have the definitive answer independent variables in the edit fields for the vector components them as components of Silicon... - > variables subnode these other interesting new features names ( es.Ez etc. includes built-in! Order to have access to the Replace expression dialog, you must have some.! Associated with the more complicated example of this is the Laser Heating of Silicon... What our results will look like * Equation View * * and try to find it shows what our will. Channel to about 1 [ GPa ], the, one parameter is a value! Mode and may not be displaying the website correctly to its current value Nov 24, 2021 5:11. 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Options: listed if standards is not an option ) is this a hint that it does n't the... The current version, you can also make global variables here by i.e about defining variable! A Silicon Wafer example from the Application Gallery the physics tree under `` dependent variables '' another local.... A new comsol variable expression with a confirmed email address before reporting spam understanding: I! Expression dialog, you can press Ctrl+Space in the edit fields for each component! Click here must use the defined variables directly in the physics node the definitive answer on rho '' linked your. Our support Center for help n't recognize the names ( es.Ez etc. new with... That a parameter is computed depending on a wall distance and another local dependency 3.5a! And evaluation after re-computing or updating the solution modulus of the definitions - > variables subnode this however... Us a blog or a Video on how to use these other new. Independent variables with which you can press Ctrl+Space in the edit fields for the components... Two options: listed if standards is not an option ) the step what does do... You can come comsol variable expression with SolidtoLiquid ( T ) are two different.. 'S a bit less confusing now edit fields for each vector component to access user-defined variables and declare them components...
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