5 ms·
Damn, got my hopes up. That's close, but not quite the same thing. The nondimensionalization article is talking about reducing free dimensions in a model by va
by schiffern 8y ago
Damn, got my hopes up. That's close, but not quite the same thing.
The nondimensionalization article is talking about reducing free dimensions in a model by variable substitution (while following all the rules of dimensional analysis), but I'm talking about re-writing a single equation so it can be used by "unit-phobic" people by simply dropping (not substituting!) all units (breaking all the rules of dimensional analysis), and assuming a certain set of units for input and output values.
Compare this (incorrect) formula, which gives no hint as to which units are being used for pressure or height:
h_alt = ( 1 - ( P_sta / 1013.25 )^0.190284 ) · 145366.45
with this (correct) equation, which always works regardless of what units are chosen (just follow the unit conversion rules):
h_alt = (1 - (P_sta / (101.325 kPa))^0.190284 · 44307.69396 meter
There are even unit-preserving calculators like Frink, which allow you to specify any units (for instance, giving barometric pressure in light-nanoseconds of mercury[1]).
[1] http://frinklang.org/fsp/frink.fsp?fromVal=%281+-+%282.5+light+nanosecond+Hg+gravity%29+%2F+%28101.325+kPa%29%29%5E0.190284+%C2%B7+44307.69396+meter&toVal=#calc http://frinklang.org/fsp/frink.fsp?fromVal=%281+-+%282.5+lig...