Hmm, let's see. I think it's more like this, (ML^-1T^-2 * L^-1) * � ML^-3 * (ML^-1T^-2 * L^-1)^-1 = L^-1T^-2, Pressure Gradient divided by Fluid (or Mass) Density.<br><br>�I think I follow; doing my home work, one bar being a kilopascal (kPa), or (10e3 * NL^-2), or (10e3 * MLT^-2), so we have (10e3 * MLT^-2 * L^-1).<br>
<br>Okay, then yes we divide by mass density of ML^-3, or multiply by (ML^-3)^-1 if you prefer.<br><br>So we have (10e3 * MLT^-2 * L^-1) * (ML^-3)^-1.<br><br>Hope my rusty dimensional analysis skills are showing... :-)<br>
<br>Okay, so we can do some reductions I think, (10e3 * L^3 * T^-2). Am I reading this correctly? Is this the rate at which a volume transfers? Something along these lines. Really not up on my dimensional analysis like I should be; but I WILL be.<br>
<br>However it reduced, please verify I am reducing correctly, I don't think the units are supposed to make sense; we're arriving at an intermediate conversion factor I believe. At least that's how it is explained to me.<br>
<br><div class="gmail_quote">On Thu, Jul 21, 2011 at 5:23 PM, Noah Roberts <span dir="ltr"><<a href="mailto:roberts.noah@gmail.com">roberts.noah@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<div class="im">On 7/21/2011 3:16 PM, Michael Powell wrote:<br>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
Okay, here's what we need to get at, for starters. And maybe an<br>
illustration or three and a little exchange will go a long way towards<br>
helping my better comprehend units.<br>
<br>
I'm starting with a set of SI calculations for oil and gas constants<br>
calculations. Eventually we will need to accommodate US units as well.<br>
But not quite yet.<br>
<br>
We need to get at a calculation involving Pressure Gradient, which ends<br>
up being metric::bar/si::meter (bars over meters) in specific units, or<br>
I suppose si::pressure/si::length might also work.<br>
<br>
Then we need to get after Fluid Density, which ends up being<br>
si::kilogram/si:meter^3 (kilograms over cubic meters) in specific units,<br>
or I suppose si::mass/si::meter^3 (I don't know what this looks like in<br>
terms of boost::units, maybe one of the volumes?), or perhaps make use<br>
of mass_density?<br>
</blockquote>
<br></div>
Yes, it's mass_density.<div class="im"><br>
<br>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<br>
We take all that and divide Pressure Gradient by Fluid Density to arrive<br>
at what we hope will be the the conversion factor: 0.0000981. Which we<br>
could specify that as a constant, but I like proving it through the<br>
software first (plausibly once) when we ask for it.<br>
</blockquote>
<br></div>
So, by your description:<br>
<br>
ML^-3 * (ML^-1T^-2 * L^-1)^-1 = L^-1T^-2.<br>
<br>
This latter part is the dimension your factor is in.<br>
<br>
using namespace boost::units;<br>
<br>
typedef derived_dimension<length_base_<u></u>dimension, -1, time_base_dimension, -2>::type funky_factor_dimension<br>
<br>
typedef unit<funky_factor_dimension, si::system> funky_factor;<br>
<br>
quantity<funky_factor> factor(quantity<si::pressure> p, quantity<si::length> l, quantity<si::mass_density> d)<br>
{<br>
�return (p / l) / d;<br>
}<br>
<br>
Alternatively:<br>
<br>
template < typename System ><br>
quantity<unit<funky_factor_<u></u>dimension, System>><br>
�factor( quantity<unit<pressure_<u></u>dimension,System>> p<br>
� � � �, quantity<unit<length_<u></u>dimension,System>> l<br>
� � � �, quantity<unit<mass_density_<u></u>dimension,System>> d )<br>
{<br>
�return (p / l) / d;<div class="im"><br>
}<br>
<br>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<br>
Similar type calculations would follow for US units involving gallons,<br>
cubic inches, inches, and inches per foot, along these lines.<br>
</blockquote>
<br></div>
As long as you use a coherent system, the template version above should work (assuming I got all the types correct).<br>
<br>
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</blockquote></div><br>