The with operator lets you postprocess more than one parametric or eigensolution in a similar fashion. Magnus. They live on boundaries and help you evaluate anything with discontinuities. I also studied the logical expressions list in the users manual, without success. - Variable: mod1.p Unterschleiheim ( Central Bavarian: Untaschleiheim) is a town in Bavaria, Germany. Say that you have invented your own measure of structural stress. If you provide a description, COMSOL uses that and it appears among the other expressions in alphabetical order; otherwise the variable name appears within parentheses. However I wish to assign the variable xi to the value of x when T=300 and y=0. I tried the following expression with no success: S. I am using the d operator but it isnt working for me. I have a simple bi-metal assembly. Setting reference pressure does not affect my results at all, Operators not allowed in user-defined functions, Including Operators and Expressions in a Multiphysics Simulation Is Easier Than You Think. After I would created another one with a conditional statement: 1 Reply, Please login with a confirmed email address before reporting spam. an expression V = V0+V1*(x>1) works well for many cases meaning V=V0 for X1) 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 Is that a bug or it this meant to be? Now all you need to do is enter sqrt(0.5*(tresca_smld^2+mises_smld^2)) in any of the Expression fields and click OK to see your new stress distribution. listed if standards is not an option). i) your BC is oscillating, but you should be able to plot that function (or define it as a function first and then plot it from the user function menu) matlab returns a 1 to indicate true and 0 to indicate false. Posted: 7 years ago. You can fix this by pressing 'F12' on your keyboard, Selecting 'Document Mode' and choosing 'standards' (or the latest version Simply type, for example, 5* (t>6), which evaluates to 0 for simulation times up to 6 seconds and to 5 after 6 seconds. This is handy if you want to see changes over a time interval. I hope this helps. if(T==300 && y == 0,xi == x) / 48.28333N 11.56667E / 48.28333; 11.56667. Discontinuous functions like the step function above might cause numerical difficulties. As most skilled COMSOL users, I am sure you know that you are not limited to just selecting what is in our drop-down lists. COMSOL Multiphysics provides smoothing functions that you can use to make, for example, smooth step functions that are continuous. 293-10*flc2hs(t,0)*(600, Hi I didn't tested it, but it seems that it would work. Duplicate variable name. [/QUOTE] Ivar, <1) works well for many cases meaning V=V0 for X<= 1 and V=V0+V1 above>>, Regarding the above statement, I don't see how this syntax communicates that V=V0 for X 100, then i = -1, if not i = 0, Hi Please, could you tell me how to access (for instance with the WITH() operator, or by means of the JOIN node for data) to any value of two different parameterized solutions (say in one solution the parameter goes from 0 to 1 and in the other the parameters goes form 1 to 2)? In my case, I'm trying to type a cosine function to simulate solar radiation throghout a year, with daily and annual variation. Hello Jesus, For a simple rule of 2 variables x and y: if x<a then y=c1 else y=c2 In Comsol: y= if (x<a,c1,c2) Furthermore, i don't know how to link 2 rules with 3 variables x,y,z: if x<a then y=c1 else if z<b then y=c2 else y=c3 I will appreciate if anyone know the solution. For plots that take vector inputs you must use the defined variables directly in the edit fields for the vector components. You can fix this by pressing 'F12' on your keyboard, Selecting 'Document Mode' and choosing 'standards' (or the latest version I would create an analytic equation with the expression: Go to Plot Parameters to find out what these predefined stresses are called (tresca_smsld and mises_smsld if you are modeling in 3D with the Structural Mechanics Module). But I want that the function to be true only to values above 0. For a given temperature, it is either bend upward or not at all. After I would created another one with a conditional statement: Version 5.2a -- Results-Derived Values-Surface Integration, set Expression equal to 1 to get the full area, and Expression equal to (u>1.5) to find the area where u is larger than 1.5. Magnus Ringh, COMSOL. Yes you can. listed if standards is not an option). f(t) = a+b*cos(2*pi*t/8760)+c*cos(2*pi*t/24) Thank you for your answer. The purpose is to use the final time-step Temperature T1 of comp1 as the initial value T0 of comp2. - Variable: mod1.p Error in multiphysics compilation. you need to separate each condition and multiply them, i.e. Hello my freinds, -- In 1D, the filter is applied to the points on the curves plotted using the plot node to which you add a Filter subnode. What I did . The numbers 24 and 8760 in your expression suggest to me that perhaps you think t is in hours (8760 is the number of hours in a year, 24 the number of hours in a day), when it's in seconds, the SI unit for time. I took the minimum temperature of a domain and i want to imply that the time when the minimum temperature in a system reaches 50 degC ? if ( (x, [QUOTE] regards My Email: athenaserra@gmail.com. Cite 15th Feb, 2018. Plotting the expression at (20,p)-at (10,p) overrides the Solution at time setting and shows you the pressure increase between 10 and 20 seconds. An example: I want to apply following step function in my temperature boundary condition: Best regards, Learn Conditional Statements Within An Expression in COMSOL Multiphysics. Discontinuous functions like the step function above might cause numerical difficulties. It must be there, but where?? This is handy if you want to see changes over a time interval. Alexandre. In fact, I'm not having problems with units of time, since I can define that the argument t is in hours, then COMSOL makes the convertion automaticaly I believe. Problem solved! huseyin. Ivar. Your internet explorer is in compatibility mode and may not be displaying the website correctly. If I use the expression you suggested then xi comes back with a value of 0. I get an error message when trying to open my glTF-file in an external viewer, Using the Previous Solution Operator in Transient Modeling. Thanks for the quick reply. The at operator lets you access the solution at any time in postprocessing. Your internet explorer is in compatibility mode and may not be displaying the website correctly. Online Support Center: https://www.comsol.com/support Discussion Closed This discussion was created more than 6 months ago and has been closed. Ivar. To add a Logical Expression node, right-click a 2D or 3D Mesh node (that has an imported mesh) and select Logical Expression from the Partition Entities menu. To express an integral, just create and use an integration operator. Am I right? Suppose you have an integration operator intop1 and an expression u that you want to integrate over the rectangle x10) or simply, ((f(t))>0) With up(gradT_ht) and down(gradT_ht) however, you can decide which side you are interested in. Thanks! Hi Can anyone give an advice on how to implement a conditional statement with two arguments? It does not work. Good luck Hi Jing, glad you found it useful. Hi 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. ii) you have some numerical or strange model issues going on, ad one coul expect that to happen also if you sart with just one step I tried to implement as a prescribed displacement : V0*(v, Hi (x==0)*(T==300)*YourValue What worked for me is V0(v. Hi, (^2) can change negetive sign to positive but why we should use abs before for example; abs(ewfd.s11)^2 to calculate norm of S11? if(f(t)>0, f(t), 0) Something like: if (y ==0 and T == 300, xi == x) Would the AND logical operator (&&) work instead of the and in my above statement? Please: How to calculate this in Comsol 5.4:-8*Al*Al*integralof(dT/dz(r,0))*r*dr) from(0 to 1/2/Al). have you tried the filter and (x2) condition, or whatever Boolena condition you need ? Ivar, Are there any way to make a 2D function? -- Hi Randhir, I would really appreciate some help! / 48.28333N 11.56667E / 48.28333; 11.56667. I found the solution and I'm going to share it with you. of 2 [mm] * 3 [mm], but not along the two edges at x=2 and y=3. I was working on a similar problem and had similar issues. listed if standards is not an option). Then use the sections below to specify the geometric entities to split, the expression, and the split condition. See the Global and Local Definitions chapter, under Operators, Functions, and Constants>Built-In Operators. Posted Apr 23, 2015, 1:54 a.m. GMT+2 where the last two expressions both evaluate to the number of seconds in an astronomical year (31557600 s). Operators, including the up and down operators, are documented in the COMSOL Multiphysics Reference Manual. Bavaria Schweisstechnik is an important producer of submerged arc welding consumables for the hydropower industry. I understand what you are saying. 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. So I would advice to use a step function or a heaviside function with a smooth (but short) transition width 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. 7 Replies, Please login with a confirmed email address before reporting spam. an expression V = V0+V1* (x>1) works well for many cases meaning V=V0 for X<= 1 and V=V0+V1 above. Ivar, Hi, then what about: This consent may be withdrawn. matlab has several types of relational operators; some of the most common are listed below: Good luck If you work with electromagnetics, you might have plotted the magnetic field in an eigenmode analysis only to find that it appears to be identically zero. I really like the new COMSOL capability to join two separate solutions into one dataset using the Join functionality. Ivar, Hi Ivar, Ivar, Hi, http://www.comsol.com/support/knowledgebase/905/ Your internet explorer is in compatibility mode and may not be displaying the website correctly. then what about: So that if both T=300 and y=0 are true (then equal to one) then whatever the x coordinate at the point is gets assigned to xi. Posted Feb 1, 2010, 12:54 p.m. EST
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