Question about Unit convertion in Diana

posted by lizheng619 on Thu, 01/09/2011 - 17:05

Hi, all friends,
Can anyone explain me the Unit system in Diana, I got a little bit confused.
 
To translate from SI to mm-kg-N system DIANA uses
[m] = 1 kg
[l] = 10^3 mm
[t] = sqrt(10^3) s 
 
Why the time should be sqrt(10^3)s, in DIANA system?
 
Can anybody help me? Thanks a lot.
 

Forums: 
DIANA

On Thu, 01/09/2011 - 19:30

Hello,
Take a look at this previous topic on the discussion board, this should help you.
http://tnodiana.com/content/Thermal-conductivity
What are you trying to convert?
Tom

By tscullion

On Fri, 02/09/2011 - 14:59

I dont understant where does the  "sqrt(10^3) s" come from, what is the theory behind this value.
 
Why during converting Time (s) in SI system to mm-kg-N system, there should be a '' sqrt(10^3) s "?
 
Thanks in advance.
 

By lizheng619

On Thu, 08/09/2011 - 13:32

The theory behind the "strange" time unit is that you always need to have a consistent set of units to perform calculations, because all derived units come from a few standard units.
In case you want to use kilogram for mass unit [M], mm for length unit [L] and N for force unit[F], you need to consider that the force unit can be written as a combination of the mass, length and time unit [T]:
[F] = [ML/T^2] 
[F] =  N
[M] = kg
[L] = mm
1 N = 1 kg m / s^2 = 1000 kg mm / s^2 = 1000 [M][L]/s^2 = [F] = [M][L]/[T]^2
Rewriting yields that [T^2] =  s^2 / 1000 , so T = 1 / sqrt(1000) s
In case you don't want "strange" units, you best use the standard SI units: kg, m, s, N for mass, length, time and force respectively. For more information on units check Table 1.1 of paragraph 1.1 of the Analysis Procedures!

By Jonna Manie