摘要 :
Heat-transfer data from supersonic wind-tunnel tests of a heated 20 degree cone are compared with theoretical results obtained by the method for determining the convective heat transfer in laminar boundary layers in a compressible...
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Heat-transfer data from supersonic wind-tunnel tests of a heated 20 degree cone are compared with theoretical results obtained by the method for determining the convective heat transfer in laminar boundary layers in a compressible fluid developed by Hantzche and Wendt and with the method presented in NACA TN No. 1300. The experimental data are also compared with the results obtained by Eber at the Kochel Laboratory in Germany and it is found that Eber's results correspond to those obtained with a turbulent boundary layer on the cone. The results provide a qualitative verification of the effect of heat transfer on laminar boundary-layer stability that has been predicted theoretically by Lees in NACA TN No. 1360.
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摘要 :
Design and simulation of hypersonic vehicles require simultaneous consideration of a variety of disciplines due to the highly coupled nature of the flight regime. In order to capture all of the potential effects on vehicle dynamic...
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Design and simulation of hypersonic vehicles require simultaneous consideration of a variety of disciplines due to the highly coupled nature of the flight regime. In order to capture all of the potential effects on vehicle dynamics, one must consider the aerodynamics, aerodynamic heating, heat transfer, and structural dynamics as well as the interactions between these disciplines. While high-fidelity modeling techniques exist for each of these disciplines, the use of such techniques is computationally infeasible in a vehicle design and control system simulation setting for such a highly coupled problem. Many iterations of analyses may need to be carried out as the vehicle design matures, thus requiring quick analysis turn-around time. Additionally, the number of states used in the analyses must be small enough to allow for efficient control simulation and design. As a result, alternative approaches must be considered for vehicle simulations. This dissertation presents a fully coupled, reduced-order aerothermoelastic framework for the modeling and analysis of hypersonic vehicle structures. The reduced-order transient thermal solution used to obtain the instantaneous temperature distribution is based on the projection of the governing equations onto a modal subspace which is obtained via the proper orthogonal decomposition (POD). The proper orthogonal decomposition is used for the thermal problem due to its optimality properties which are described in the dissertation. The reduced-order structural dynamic solution is also based on projection of the governing equations onto a modal subspace. However, for the structural dynamics, the modal subspace is composed of a set of Ritz modes which include both free vibration modes and load- dependent Ritz vectors. In order to avoid the need to reassemble the temperature dependent stiffness matrix and thermal load vector at each time step, a technique is developed for directly updating these quantities as a function of the POD modal coordinates.
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摘要 :
Turbulence was generated by using screens, and the turbulence percentage was measured by a hot-wire anemometer both in the boundary layer and the free stream. The local heat-transfer coefficient was measured at 12 locations along ...
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Turbulence was generated by using screens, and the turbulence percentage was measured by a hot-wire anemometer both in the boundary layer and the free stream. The local heat-transfer coefficient was measured at 12 locations along the plate for the cases of various turbulence levels. The transition Reynolds number from laminar to turbulent flow decreases as the main-stream turbulence level increases. In the range of laminar heat transfer the effect of turbulence in the main flow was not great, but in the range of turbulent heat transfer the heat-transfer coefficient increases according to the increase of turbulence.
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摘要 :
An experimental investigation into the aerodynamic heating on a Mars entry vehicle shape with several types of local surface distortion is presented. The configurations tested were 0.033-scale models of a spherically blunted 70° ...
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An experimental investigation into the aerodynamic heating on a Mars entry vehicle shape with several types of local surface distortion is presented. The configurations tested were 0.033-scale models of a spherically blunted 70° half-angle cone with two protuberances of different length, representing the tube leading to the gas chromograph mass spectrometer, and two aeroshell-bioshield attachment points of different size. These models were tested at free-stream Reynolds numbers per meter of 3.7 x 106 and 17 x 106 over an angle-of-attack range from 0° to 18° in the Langley Mach 8 variable-density hypersonic tunnel. The phase-change-coating technique was used to measure heat-transfer coefficient.
The long protuberance caused more severe interference heating than the short protuber¬ance for the same conditions. When the short projection was located close to the edge of the aeroshell, the interference heating was greater than that on the same projection when located near the vertex. A significant increase in heat-transfer coefficient was measured only on the larger aeroshell-bioshield attachment point.
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