Variability of focused sonic booms from accelerating supersonic aircraft in consideration of meteorological effects

Abstract

Statistics of the meteorologically induced variability of focused sonic boom characteristics due to unsteady, accelerated supersonic flights were derived. The simulations were performed with an advanced sonic boom software including a numerical solver of the Nonlinear Tricomi Equation modeling the focused sound pressure field around caustics. A one-year set of daily meteorological data along the Northern Atlantic flight corridor was used as input. The statistics comprise the location, strength and geometrical extension of caustics at ground level for assumed flights of a supersonic commercial transport from Paris to New York and back. Caustics only occurred during the acceleration phase above the English Channel for flights from Paris to New York, never during the deceleration phase of return flights. The mean value of the maximum focused overpressure is found to be about 4 times the maximum overpressure for cruise flight at Mach 2 in similar conditions, but shows a large variability. The caustics intersection with the ground varies between 3 and 8 km in width and between 30 and 180 km in length. A linear correlation analysis showed the relationship between meteorological profile shape parameters and the focused sonic boom characteristics.

Nonlinear and diffraction effects in propagation of N-waves in randomly inhomogeneous moving media

“…However, peak pressures more than 600 Pa have been measured associated with focusing of sonic boom waveforms. 19,26 Therefore, in these simulations, three values of N are considered: N ¼ 0 which results in linear propagation, N ¼ 0.025 corresponding to p 0 ' 450 Pa, and N ¼ 0.05 corresponding to p 0 ' 900 Pa in order to evaluate nonlinearity beyond the range observed in sonic booms. The wind velocity in the turbulent atmosphere during sonic boom experiments was up to 15 m/s (Ref.…”

“…This suggests that sonic boom propagation through TBL could be considered as linear. However, atmospheric conditions or aircraft maneuvers can result in focal regions in which overpressures more than 600 Pa have been reported 19,26 ; in this case nonlinear effects during propagation through the TBL may become important. a) Author to whom correspondence should be addressed.…”

Focusing of ground vibrations generated by high-speed trains travelling at trans-Rayleigh speeds

“…Some preliminary results on this topic have been reported earlier [19]. The two specific cases to be considered are focusing due to track curvature and focusing due to train acceleration, which are of the same physical nature as similar cases of focusing of a sonic boom from supersonic aircraft, sometimes called 'superbooms' [20][21][22]. It will be demonstrated that in both these cases the effect of focusing can result in noticeable increase in generated ground vibrations.…”

Focusing of Shear Shock Waves

“…Shock waves, such as those that generate outdoor noise, can also be undesirable. For instance the sonic boom from supersonic flight, is focused during transonic acceleration [6] thus severely limiting flight at supersonic speed over land. In linear wave theory focusing is described by catastrophe theory [7,8].…”