NEGATIVELY BUOYANT FLOW ALONG VERTICAL CYLINDERS AT HIGH RAYLEIGH NUMBERS

Conditions that must be satisfied before the launch of a Space Transportation System (STS) include combinations of ambient temperature and wind speed that are intended to prevent ice formation on the External Tank (ET) and a local air temperature around the STS of 33-degrees-F (0.56-degrees-C) or less. Nineteen effluent gases are purged or vented from the STS into the launch pad environment, the most significant of these being the cold and negatively buoyant boil-off gaseous oxygen (GOX) from the oxygen tank. Vented into the ambient, this GOX can be wind-carried toward the STS, where it will cool the launch pad environment. This article described a combined three-dimensional (3D) and two-dimensional (2D) computational fluid dynamics (CFD) analysis that investigated this cooling effect. The results of this analysis for a 6-knot (3.09 m/s) west wind and an ambient temperature of 38-degrees-F (3.33-degrees-C) indicate that the GOX could cool, relative to the ambient, the local air in the vicinity of the STS and the surface of the east Redesigned Solid Rocket Motor (RSRM) by as much as 28-degrees-F (15.56-degrees-C) and 5 to 6-degrees-F (2.78 to 3.33-degrees-C), respectively. The large lengths associated with the ET and the east RSRM resulted in Rayleigh numbers that were one to three orders of magnitude larger than those found in literature.