Factors Affecting the Vertical Motion of a Zero-Pressure, Polyethylene, Free Balloon
Scientific interim rept. 31 Dec 1983-31 Dec 1984
AIR FORCE GEOPHYSICS LAB HANSCOM AFB MA
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This paper critiques existing aerodynamic-thermodynamic models for predicting the vertical motion of free balloon systems. It demonstrates that a the aerodynamic drag coefficient model should be based on Froude number and fractional volume as well as Reynolds number b there has been a widespread error in definition of the instantaneous mass of the balloon film involved in the heat transfer process c the gas bubble cannot be modelled as a sphere d the gas bubble is asymmetrical except when near or at its natural ceiling altitude and e the actual gas bubble shape, and most probably the added mass, is directly related to the type of gore pattern. Finally, a procedure is proposed for the analysis of actual flight data to enable the development of a practical, but also theoretically sound, model of the aerodynamic drag coefficient of a zero-pressure, free balloon- and subsequent refinement of the heat transfer models for direct and reflected solar energy.
- Fluid Mechanics