ESDU AERO A.08.01.09 uses a criterion of similarity for conditions of uniform velocity and temperature distributions within and outside the jet to extend data for a cold jet to apply to a heated jet. To estimate inflow angle in the external flow two graphs are provided@ one applying to the region of the jet surrounding a core region in which no mixing takes place and one applying downstream of that region. A curve on those graphs allows the core length to be determined for a cold jet and the worked examples show how that length may be corrected to apply to a heated jet. A third graph plots the boundaries defining the edge of the turbulent mixing region of the jet and the core of the cold jet for ratios of freestream to jet velocities of 0 to 0.5.