Abstract:
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It is well known that hydrodynamic drag reduction can be obtained by locally surround-ing an immersed solid boundary with another low viscosity-fluid resulting in a lubricating effect. In aerodynamics propulsion, this principle has been used in the so called super-cavitation, in which the viscous drag resistance acting on a, say, torpedo or submarine is substantially reduced by enclosing the body in a low-viscosity gas bubble. In this paper we are exploring the same idea but in an opposite direction, namely: we want to know if creating a high-viscosity fluid layer or film can result in an anti-lubricating effect in which the viscous drag resistance is substantially increased, i.e., a drag enhancement technique. The main motivation behind this idea is in application to the Red planet for landing large payloads as for example in future human missions with payloads several factors larger than an unmanned spacecraft and where the thin atmosphere of Mars sharply reduce the aerobraking capabilities. Utilizing a simplified turbulent layer model the theoretical justification of this rather intuitive idea is outlined. Some preliminary computational fluid dynamics calculations were performed which encourage further research. |