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how to non-dimensionlize time in 5.1
Posted 12 août 2015, 02:35 UTC−4 2 Replies
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Hi,
Please, i will be very grateful if some one can help me with this. I am working with dimensionless parameters using comsol 5.1 trial version, but could not have the time in dimensionless form. I clicked at none in general unit system as I use to do in other versions and every thing will be in dimensionless form but that does not seem to work here in 5.1 and the time is showing its unit (s). there is a menu under study1 where i put in the time range, even in that place there is provision for none but all other time units are there. I will be happy if some one can help me with this before the license expire.
Thanks George
Please, i will be very grateful if some one can help me with this. I am working with dimensionless parameters using comsol 5.1 trial version, but could not have the time in dimensionless form. I clicked at none in general unit system as I use to do in other versions and every thing will be in dimensionless form but that does not seem to work here in 5.1 and the time is showing its unit (s). there is a menu under study1 where i put in the time range, even in that place there is provision for none but all other time units are there. I will be happy if some one can help me with this before the license expire.
Thanks George
2 Replies Last Post 12 août 2015, 03:32 UTC−4
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Posted:
9 years ago
Hi
My experience is opposite, there is no time unit. See my attached very simple 1D-model. When you think of non-dimensional problem, you have to convert the equations dimensionless. In the diffusion equation
X = x/L where L is the length of the domain
T = Dt/L² = dimensionless time
C = c/c0 = dimensionmless concentration
Inserting these to Fick's second law we have
partial C over partial T = partial² C over partial X²
Note that you have to give the value 1 to the diffusion coefficient as it disappears from the equation.
BR
Lasse
My experience is opposite, there is no time unit. See my attached very simple 1D-model. When you think of non-dimensional problem, you have to convert the equations dimensionless. In the diffusion equation
X = x/L where L is the length of the domain
T = Dt/L² = dimensionless time
C = c/c0 = dimensionmless concentration
Inserting these to Fick's second law we have
partial C over partial T = partial² C over partial X²
Note that you have to give the value 1 to the diffusion coefficient as it disappears from the equation.
BR
Lasse
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Posted:
9 years ago
That works in 5.1. On the top node in the model builder tree, set Unit System: none.
Don't forget that you are entitled to technical support from support@comsol.com during your trial period.
Niklas
Don't forget that you are entitled to technical support from support@comsol.com during your trial period.
Niklas
Hi,
Please, i will be very grateful if some one can help me with this. I am working with dimensionless parameters using comsol 5.1 trial version, but could not have the time in dimensionless form. I clicked at none in general unit system as I use to do in other versions and every thing will be in dimensionless form but that does not seem to work here in 5.1 and the time is showing its unit (s). there is a menu under study1 where i put in the time range, even in that place there is provision for none but all other time units are there. I will be happy if some one can help me with this before the license expire.
Thanks George