The climb rate of a glider when circling within an isolated thermal vortex ring

Abstract

One model for the motion of thermals...is the vortex ring: How does this phenomenon influence soaring?....  The most important findings are: 1. Horizontal inflow contributes significantly to the glider's rate of climb, 2. The circle radius is not important, 3. The climb performance of gliders is determined mostly by their minimum polar sink rates, 4. The water carrying glider should bank a bit more steeply than and empty one, 5. The optimum circling speed is close to that of minimum sink.