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Problem with units
Posted Nov 8, 2011, 10:45 a.m. EST Version 4.0a 2 Replies
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Hi,
I want to use a density variation with concentration of the form:
rho=A*sqrt(C)+B*C^2
where C is in mol/m^3.
To supply the value of A i need to put units of m^1.5/mol^0.5
However, I am unable to do so as it gives errors.
Please help.
Thanks
I want to use a density variation with concentration of the form:
rho=A*sqrt(C)+B*C^2
where C is in mol/m^3.
To supply the value of A i need to put units of m^1.5/mol^0.5
However, I am unable to do so as it gives errors.
Please help.
Thanks
2 Replies Last Post Nov 9, 2011, 4:02 a.m. EST
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Posted:
1 decade ago
Hi
there is a few threads about that, there was an issue with fractional units in v4.0 (I belive its solved in later releases)
But the orange unit waring is only a warning, so long you put consistent values it will calculate and if you respect values correctly the results would even be correct. you do just not get the COMSOL verification of your units
--
Good luck
Ivar
there is a few threads about that, there was an issue with fractional units in v4.0 (I belive its solved in later releases)
But the orange unit waring is only a warning, so long you put consistent values it will calculate and if you respect values correctly the results would even be correct. you do just not get the COMSOL verification of your units
--
Good luck
Ivar
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Posted:
1 decade ago
Hi,
COMSOL does not yet support non-integer unit exponents, so attempting an operation or declaration that results in such unit exponents gives a unit syntax error. One way to work around this in this case would be to define A^2 rather than A.
A_squared = <value of A>^2[m^3/mol]
then the expression A*sqrt(C) = sqrt(A_squared*C) gets a valid unit (dimensionless in this case).
But if you want A*sqrt(C) to be a density with the unit of kg/m^3, use
A_squared = <value of A>^2[kg^2/(mol*m^3)]
instead.
Best regards,
Magnus Ringh, COMSOL
COMSOL does not yet support non-integer unit exponents, so attempting an operation or declaration that results in such unit exponents gives a unit syntax error. One way to work around this in this case would be to define A^2 rather than A.
A_squared = <value of A>^2[m^3/mol]
then the expression A*sqrt(C) = sqrt(A_squared*C) gets a valid unit (dimensionless in this case).
But if you want A*sqrt(C) to be a density with the unit of kg/m^3, use
A_squared = <value of A>^2[kg^2/(mol*m^3)]
instead.
Best regards,
Magnus Ringh, COMSOL