ISA Calculation Question

[merronys]

I know it's Boyle's law and all that, but I can't find the factors I need for this one.... .. .What volume would a cubic metre of air at sea-level in ISA occupy if temperature is raised by 1 degree celcius?

[bluskis]

Volume would be [273+16]/[273+15]cu m, ignoring any change in pressure.That is the volume ratio is proportional to the absolute T ratio.

[Chris2]

Is this a question which appears in JAA atpl exams ??????

[Genghis the Engineer]

Anybody noticed that there are people with other interests than passing ATPL exams? Some of them are even aviation professionals and members of Pprune.. .. .G

[merronys]

Thanks bluskis.. .. .No - it's not an exam question, I am just trying to knock up a simplistic atmospheric simulation to help drum in some met. into my addled brain <img border="0" title="" alt="[Roll Eyes]" src="rolleyes.gif" /> . (I suppose that's what you get when us IT-types try to become flying types...)

[Genghis the Engineer]

For a computer model, you'd be best off using the basic ISA derivative equations for density, pressure and temperature. The relationships are exponential up to the tropopause, then - well - otherwise.. .. .If you want basic proofs, any undergraduate aerodynamics textbook will give you that. "Aerodynamics for Engineering Students" by Houghton+1 is the best known, although I prefer "Aerodynamics" by Clancy. It's pretty straightforward to model the lower atmosphere from first principles.. .. .If you are looking for small changes, then relative density = relative pressure divided by relative temperature - always working in absolute (Kelvin or Rankine) temperature, not relative (Celcius or Farenheit).. .. .G