Strange scaling of EPM output with number of engines

[sdeastham]

APCEMM/Code.v05-00/src/Core/LAGRIDPlumeModel.cpp

Lines 219 to 225 in 67f9541

	epmOutput.area *= 2.0;
	if ( aircraft_.EngNumber() != 2 ) {
	epmOutput.iceDensity *= aircraft_.EngNumber() / 2.0; //Scale densities by this factor to account for the plume size already doubling.
	epmOutput.sootDensity *= aircraft_.EngNumber() / 2.0;
	epmOutput.SO4Aer.scalePdf( aircraft_.EngNumber()); //EPM only runs for one engine, so scale aerosol pdfs by engine number.
	epmOutput.IceAer.scalePdf( aircraft_.EngNumber());
	}

This behavior does not seem quite right - putting this issue here mostly to highlight it. It should be revisited with EPM 2.0.

[sdeastham]

Quoting from the information written in the original plume model:

/* Compute initial plume area and scale initial ice aerosol properties based on number engines.
     * Note that EPM results are for ONLY ONE ENGINE.
     * If 2 engines, we assume that after 3 mins, the two plumes haven't fully mixed yet and result in a total
     * area of 2 * the area computed for one engine
     * If 3 or more engines, we assume that the plumes originating from the same wing have mixed. */