Engineering topics
Publications and source records attributed to George, A. R..
Means of reducing or eliminating the sonic boom through aerodynamic design or aircraft operation are discussed. These include designing aircraft to minimize or eliminate certain features of the overpressure signature, operating aircraft at slightly supersonic speeds so that the sonic boom does not reach the ground, and seeking reductions through the high altitude-high speed flight conditions of hypersonic transports.
The effect of turbulence on the structure of weak shock waves is investigated. The equilibrium structure is shown to be governed by a balance between nonlinear steepening and the turbulent scattering of acoustic energy out of the main wave direction. The scattered energy appears as perturbations behind the shock front. For conditions typical of sonic booms in atmospheric turbulence the wave structure is governed by a Burgers equation similar to that describing viscous shocks, except that parameters related to the turbulence appear instead of the viscosity coefficient. The magnitude of the perturbations following a shock is estimated from first-order scattering applied to a thickened shock. Predictions of shock thicknesses and perturbations compare favourably with available experimental data.
There have been many attempts to reduce or eliminate the sonic boom. Such attempts fall into two categories: (1) aerodynamic minimization and (2) exotic configurations. In the first category changes in the entropy and the Bernoulli constant are neglected and equivalent body shapes required to minimize the overpressure, the shock pressure rise and the impulse are deduced. These results include the beneficial effects of atmospheric stratification. In the second category, the effective length of the aircraft is increased or its base area decreased by modifying the Bernoulli constant a significant fraction of the flow past the aircraft. A figure of merit is introduced which makes it possible to judge the effectiveness of the latter schemes.
Sonic boom minimization including front and rear shocks, exemplified by SST aircraft
Sonic boom and explosion shock wave propagation over long distances through turbulence modeled by sound speed fluctuation, including acoustic scattering effect
Atmospheric turbulence effects on sonic boom shock wave thickness
Accuracy of shock pressure attenuation in near field sonic boom profiles
Weak shock thicknesses with turbulent scattering as dissipative mechanism compared with magnitude in sonic boom flight tests and explosions
Sonic boom wave shapes and amplitudes determination in still stratified atmosphere, comparing U.S. standard atmosphere results to various atmospheric models
Sonic boom lower bounds determination in midfield based on modification of Jones results by minimizing overpressure or shock strength of boom wave positive component
Sonic boom reduction by azimuthal redistribution of supersonic aircraft pressure field variation
Multipoles, waveforms, and atmospheric effects on pressure field distribution and sonic boom reduction
Sonic boom reduction by azimuthal redistribution of supersonic aircraft pressure field variation