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Global variables to evaluate in Parametric Sweep

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Does anyone know the syntax to evaluate the velocity at a specific point? I'm running a parametric sweep of my model and in my output for the "Globar variables to evaluate" portion I want to store the velocity of a specific point. I can't figure out how to tell comsol to evaluate the velocity at this point. Actually, I can't seem to get it to store any of the velocity values. Any insight? Thanks in advance.

7 Replies Last Post 2013年6月30日 GMT-4 08:40
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 2011年12月22日 GMT-5 03:44
Hi

have you checked the (ut,vt,wt) variables? see the doc

--
Good luck
Ivar
Hi have you checked the (ut,vt,wt) variables? see the doc -- Good luck Ivar

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Posted: 1 decade ago 2011年12月22日 GMT-5 08:48
yes, i've used these variables, but what syntax would you use to evaluate them at a specific point? For instance, if I want the y-velocity at point 7 in my model, I'm thinking I should be able to write something like: vt(pt(7)) or vt('pt7') or vt(point7) or something like that? That way, I could track the velocity at a specific point and report this value during my parametric sweep.

And if I run a parametric sweep and put the expression "vt" in the "Global variables to evaluate" box then my output file will just report a bunch of zero values. Which doesn't make sense because my model is transient and moving with time (as I can see from postprocessing). So maybe the vt variable isn't available as a global variable during the parametric sweep?

I've even tried writing a global expression in the form of: vt*(x==x_1)*(y==y_1)*(z==z_1), where x_1, y_1, and z_1 are the coordinates of my point at which I want to evaluate the velocity. Maybe I need to call this point by is node number and not the point number in my model?
yes, i've used these variables, but what syntax would you use to evaluate them at a specific point? For instance, if I want the y-velocity at point 7 in my model, I'm thinking I should be able to write something like: vt(pt(7)) or vt('pt7') or vt(point7) or something like that? That way, I could track the velocity at a specific point and report this value during my parametric sweep. And if I run a parametric sweep and put the expression "vt" in the "Global variables to evaluate" box then my output file will just report a bunch of zero values. Which doesn't make sense because my model is transient and moving with time (as I can see from postprocessing). So maybe the vt variable isn't available as a global variable during the parametric sweep? I've even tried writing a global expression in the form of: vt*(x==x_1)*(y==y_1)*(z==z_1), where x_1, y_1, and z_1 are the coordinates of my point at which I want to evaluate the velocity. Maybe I need to call this point by is node number and not the point number in my model?

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Posted: 1 decade ago 2011年12月22日 GMT-5 09:39
Ok, I figured out what to do. I figured I would post this here in case anyone else runs into a similar situation. You can use an integration coupling variable applied to the point at which you want to evaluate the position, velocity, etc. (and I'm assuming any other variable) and just make sure the "Global Destination" checkbox is marked. That way it is available as a global variable to plot in your output file from the parametric sweep.
Ok, I figured out what to do. I figured I would post this here in case anyone else runs into a similar situation. You can use an integration coupling variable applied to the point at which you want to evaluate the position, velocity, etc. (and I'm assuming any other variable) and just make sure the "Global Destination" checkbox is marked. That way it is available as a global variable to plot in your output file from the parametric sweep.

Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 2011年12月23日 GMT-5 04:03
Hi

indeed, the "pt(#)" operator you refer to is simply the "integration" = sum over a single point, slightly complex perhaps ? but perfectly mathematically understandable, no ?

--
Good luck
Ivar
Hi indeed, the "pt(#)" operator you refer to is simply the "integration" = sum over a single point, slightly complex perhaps ? but perfectly mathematically understandable, no ? -- Good luck Ivar

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Posted: 1 decade ago 2012年3月15日 GMT-4 14:02
I'm trying to solve an electro-thermal problem with a parametric sweep on the boundary conditions. Could you help me with the syntax for subdomain integration in the "global variables to evaluate" box of the parametric sweep?

I want to integrate the temperature over subdomains #7 through #17 at each value of the parameter.

Thanks
I'm trying to solve an electro-thermal problem with a parametric sweep on the boundary conditions. Could you help me with the syntax for subdomain integration in the "global variables to evaluate" box of the parametric sweep? I want to integrate the temperature over subdomains #7 through #17 at each value of the parameter. Thanks

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Posted: 1 decade ago 2013年6月5日 GMT-4 19:57

Ok, I figured out what to do. I figured I would post this here in case anyone else runs into a similar situation. You can use an integration coupling variable applied to the point at which you want to evaluate the position, velocity, etc. (and I'm assuming any other variable) and just make sure the "Global Destination" checkbox is marked. That way it is available as a global variable to plot in your output file from the parametric sweep.


Hi

where is the global destination checkbox?

I have always this error :\

Unknown function or operator.
- Name: aveop1


I am trying to make a simulation where I need to change boundary conditions according to the domain average temperature.

Many thanks :)
[QUOTE] Ok, I figured out what to do. I figured I would post this here in case anyone else runs into a similar situation. You can use an integration coupling variable applied to the point at which you want to evaluate the position, velocity, etc. (and I'm assuming any other variable) and just make sure the "Global Destination" checkbox is marked. That way it is available as a global variable to plot in your output file from the parametric sweep. [/QUOTE] Hi where is the global destination checkbox? I have always this error :\ Unknown function or operator. - Name: aveop1 I am trying to make a simulation where I need to change boundary conditions according to the domain average temperature. Many thanks :)

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Posted: 1 decade ago 2013年6月30日 GMT-4 08:40
Another way to problem, you may use the "Probe" and Probe plot to store the velocity of one special point.
You can find probe in the model definition in 4.3a Version.
Another way to problem, you may use the "Probe" and Probe plot to store the velocity of one special point. You can find probe in the model definition in 4.3a Version.

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