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Adding temperature varying with time

Posted Feb 5, 2013, 11:30 p.m. EST Fluid & Heat, Interfacing, Heat Transfer & Phase Change, Computational Fluid Dynamics (CFD), Geometry, Mesh, Modeling Tools & Definitions, Parameters, Variables, & Functions, Studies & Solvers Version 4.3a 9 Replies

Nithin
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I want to enter temperature for calculating heat flux (temperature varies with time). Is there any method of entering the values?

How can I use functions like interpolation, Rectangular etc,,,

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9 Replies Last Post Feb 6, 2013, 9:07 a.m. EST
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Feb 6, 2013, 1:02 a.m. EST
Hi

you can replace your XXX with something like T0[K]+DT[K/s]*t where T0 is a constant scalar representing the initial temperature in Kelvin, and DT is the temperature increase with time (the numbers and units are typically defined in the Parameter section with the Parameters T0 and DT)

--
Good luck
Ivar
Hi you can replace your XXX with something like T0[K]+DT[K/s]*t where T0 is a constant scalar representing the initial temperature in Kelvin, and DT is the temperature increase with time (the numbers and units are typically defined in the Parameter section with the Parameters T0 and DT) -- Good luck Ivar
Nithin
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Posted: 1 decade ago Feb 6, 2013, 1:58 a.m. EST

Hi

you can replace your XXX with something like T0[K]+DT[K/s]*t where T0 is a constant scalar representing the initial temperature in Kelvin, and DT is the temperature increase with time (the numbers and units are typically defined in the Parameter section with the Parameters T0 and DT)

--
Good luck
Ivar


But sir, I have created an interpolation as in the image for ambient temperature. where t is time and f(t) is temperature at that time. I wish to use this interpolation in inputting the T(ext) at heat flux as the outer walls of my model will be affected by ambient temperature. Can you let me know how to solve the above problem??

Please help sir...
[QUOTE] Hi you can replace your XXX with something like T0[K]+DT[K/s]*t where T0 is a constant scalar representing the initial temperature in Kelvin, and DT is the temperature increase with time (the numbers and units are typically defined in the Parameter section with the Parameters T0 and DT) -- Good luck Ivar [/QUOTE] But sir, I have created an interpolation as in the image for ambient temperature. where t is time and f(t) is temperature at that time. I wish to use this interpolation in inputting the T(ext) at heat flux as the outer walls of my model will be affected by ambient temperature. Can you let me know how to solve the above problem?? Please help sir...
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Feb 6, 2013, 3:18 a.m. EST
Hi
have you tried with Text(t[1/s]) the [1/s] is to transform the variable t with units into a "pure" number expressed in seconds

--
Good luck
Ivar
Hi have you tried with Text(t[1/s]) the [1/s] is to transform the variable t with units into a "pure" number expressed in seconds -- Good luck Ivar
Nithin
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Posted: 1 decade ago Feb 6, 2013, 3:35 a.m. EST

Hi
have you tried with Text(t[1/s]) the [1/s] is to transform the variable t with units into a "pure" number expressed in seconds

--
Good luck
Ivar


But sir, what value will it take if I give like that?? Will it take the same value of Text given beside that particular time or will any algebraic process take place??

And, Is it okay if I give the external temperature values like the given interpolation or do I need any special heat flux definition to incorporate variations in temperature as the heat transfer takes place??
[QUOTE] Hi have you tried with Text(t[1/s]) the [1/s] is to transform the variable t with units into a "pure" number expressed in seconds -- Good luck Ivar [/QUOTE] But sir, what value will it take if I give like that?? Will it take the same value of Text given beside that particular time or will any algebraic process take place?? And, Is it okay if I give the external temperature values like the given interpolation or do I need any special heat flux definition to incorporate variations in temperature as the heat transfer takes place??
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Feb 6, 2013, 4:44 a.m. EST
Hi

while the solver steps through the transient study, going from your first to the last value, it will, for each new time step, calculate the value of Text(t) you have given, it will interpolate between the values

--
Good luck
Ivar
Hi while the solver steps through the transient study, going from your first to the last value, it will, for each new time step, calculate the value of Text(t) you have given, it will interpolate between the values -- Good luck Ivar
Nithin
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Posted: 1 decade ago Feb 6, 2013, 4:55 a.m. EST

Hi

while the solver steps through the transient study, going from your first to the last value, it will, for each new time step, calculate the value of Text(t) you have given, it will interpolate between the values

--
Good luck
Ivar


Thank you sir... that's a great guidance. Can I take it that I have given the input in a correct way and the results aimed in terms of temperature variation through the elements of my model can be obtained with these inputs?
[QUOTE] Hi while the solver steps through the transient study, going from your first to the last value, it will, for each new time step, calculate the value of Text(t) you have given, it will interpolate between the values -- Good luck Ivar [/QUOTE] Thank you sir... that's a great guidance. Can I take it that I have given the input in a correct way and the results aimed in terms of temperature variation through the elements of my model can be obtained with these inputs?
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Feb 6, 2013, 5:38 a.m. EST
Hi

A good rule is always to check, so use the Results, Derived variables and plot options to follow also your input over time.
Often the Definition Probes are nice to follow a long simulation over time

--
Good luck
Ivar
Hi A good rule is always to check, so use the Results, Derived variables and plot options to follow also your input over time. Often the Definition Probes are nice to follow a long simulation over time -- Good luck Ivar
Nithin
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Posted: 1 decade ago Feb 6, 2013, 6:23 a.m. EST

Hi

A good rule is always to check, so use the Results, Derived variables and plot options to follow also your input over time.
Often the Definition Probes are nice to follow a long simulation over time

--
Good luck
Ivar


And sir, Can you let me know what would be the RAM requirement for my model? It has 1,35,45,900 DoF.
[QUOTE] Hi A good rule is always to check, so use the Results, Derived variables and plot options to follow also your input over time. Often the Definition Probes are nice to follow a long simulation over time -- Good luck Ivar [/QUOTE] And sir, Can you let me know what would be the RAM requirement for my model? It has 1,35,45,900 DoF.
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Feb 6, 2013, 9:07 a.m. EST
Hi
check the KB, there should be somewhere a document about Elements, discretization DOF and RAM,

But basically you need 4 bytes per DoF per matrix, minus what the sparsity treatment can gain, its not straightforward, but >1MDoF needs a biiig workstation

--
Good luck
Ivar
Hi check the KB, there should be somewhere a document about Elements, discretization DOF and RAM, But basically you need 4 bytes per DoF per matrix, minus what the sparsity treatment can gain, its not straightforward, but >1MDoF needs a biiig workstation -- Good luck Ivar

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