Blunt-Body Entry Vehicle Aerotherodynamics: Transition and Turbulent Heating

Abstract

Recent, current, and planned NASA missions that employ blunt-body entry vehicles pose aerothermodyamic problems that challenge state-of-the-art experimental and computational methods. The issues of boundary-layer transition and turbulent heating on the heat shield have become important in the designs of both the Mars Science Laboratory and Crew Exploration Vehicle. While considerable experience in these general areas exists, that experience is mainly derived from simple geometries; e.g., sharp-cones and flat-plates, or from lifting bodies such as the Space Shuttle Orbiter. For blunt-body vehicles, application of existing data, correlations, and comparisons is questionable because an all, or mostly, subsonic flowfield is produced behind the bow shock, as compared with the supersonic (or even hypersonic) flow of other configurations. Because of the need for design and validation data for projects such as Mars Science Laboratory and Crew Exploration Vehicle, many new experimental studies have been conducted in the last decade to obtain detailed boundary-layer transition and turbulent heating data on this class of vehicle. In this paper, details of several of the test programs are reviewed. The laminar and turbulent data from these various test are shown to correlate in terms of edge-based Stanton and Reynolds number functions. Correlations are developed from the data for transition onset and turbulent heating augmentation as functions of momentum thickness Reynolds number. These correlations can be employed as engineering-level design and analysis tools.adiabatic wall enthalpy H 0 = total freestream enthalpy H w = wall static enthalpy H 300 K = wall static enthalpy at 300 K M 1 = freestream Mach number M e = boundary-layer edge Mach number P 1 = freestream pressure Pr = Prandtl number _ q w = heat transfer rate R N = hemispherical nose radius Re 1 = freestream unit Reynolds number 1 U 1 = 1 Re e = boundary-layer edge unit Reynolds number e U e = e Re = boundary-layer momentum thickness Reynolds number e U e = e St = Stanton number based on freestream conditions _ q w = 1 U 1 H 0 H w St e = Stanton number based on boundary-layer edge conditions _ q w = e U e H aw H w T 1 = freestream temperature U 1 = freestream velocity U e = boundary-layer edge velocity x=R = normalized distance along model centerline for Mars Science Laboratory local coordinate system z=R = normalized distance along model centerline for Crew Exploration Vehicle local coordinate system = angle of attack L = factor in laminar heating correlation 1 1 = e e 1=2 e = 1 1=4 T = factor in turbulent heating correlation 1 1 = e e 1=3 e = 1 1=4 = boundary-layer momentum thickness 1 = freestream viscosity e = boundary-layer edge viscosity = turbulent heating augmentation factor St measured =St predicted;laminar I. BackgroundT HIS work deals with the correlation of blunt-body boundarylayer transition and turbulent heating data obtained from recent NASA entry vehicle development programs. Blunt-body configurations are the most common geometries employed for ent...

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