Sonic booms

Some wave phenomena, familiar to many people from the human senses, include the easy undulation of water waves from a dropped stone or the sharp shock of the sonic boom from high-speed aircraft. The great power and energy of shock events is apparent to the human observer as he stands on the rim of the Meteor Crater of Arizona. Human senses provide little insight into the transition from these directly sensed phenomena to the high-pressure, shock-compression effects in solids. This transition must come from development of the science of shock compression, based on the usual methods of scientific experimentation, theoretical modeling, and numerical simulation. 

Loud noise (143 dB), sonic boom glass failure... 

I was soon trapped in the world of imaginary numbers and gradually acquired a startle response whenever 1 heard a sonic boom. 1 recalled how Mark... 

The potential consequences of sonic booms are direct initiation of expls, unfavorable instrument reaction, window breakage, startle reaction in personnel, and bric-a-brac movement. Of these, the latter two fall within the range of the ordinary reaction to sonic booms window breakage would occur with heavy to intense sonic booms Refs 1) R.W. Van Dolah, AmSocSafetyEngJ 13, No 9 (1969), 12-14 2) G. Cohn, Ed,... 

Occasional breaking of large windows already under stress Loud noise (143 dB), sonic boom glass failure Breakage of small windows under strain Typical pressure for glass failure... 

A six-inch carbon steel elbow in a Los Angeles refinery ruptured releasing a hydrocar-bon/hydrogen mixture at 9 43 P.M. on October 8, 1992. The vapor cloud ignited within seconds. The explosion damaged nearby buildings and shattered windows several miles away and was recorded as a sonic boom at the California Institute of Technology about 20 miles away. [21]... 

This produces gradual pressure and density differences around the object which result in a certain kind of fluid flow behavior. However, when the Mach number is greater than 1, the object is moving faster than the speed of sound. When this happens the pressure disturbances cannot move out of the way fast enough, and very abrupt density and pressure changes, known as shock waves, appear. This results in a very different fluid flow behavior. These shock waves are the cause of the sonic boom sometimes heard when an airplane exceeds the speed of sound. 

Sounds produced by humans can also interfere with the ability of animals to communicate. Such interference can inhibit an animaPs ability to protect itself, to find food, and to live a normal life. For example, ships emit low-frequency sounds that interfere with whale communications. Other human noises can frighten whales away from their normal migration routes. In the desert, kangaroo rats Dipodomys spp.) exposed to the roar of a dune buggy lose their ability to hear snakes approaching. Japanese quail (Coturnix Coturnix Japonicd) have to call much louder than usual when they live in a noisy environment. Sooty terns (Sterna fuse at a) have been observed to abandon their nests when jets create sonic booms. Intense bursts of noise have also caused condors (Gymnogyps californianus) to abandon their nests. 

The environmental aspects that made the hydrogen-fueled subsonic transport plane attractive also applied to the LH2-fueled supersonic plane. Both sideline and flyover noise were expected to be lower, because, again, the plane would be considerably lighter. Sonic boom pressures would likely be lower, because of the LH2 plane s reduced weight and smaller wing area. Further pressure reductions were believed to be possible with advanced designs. 

Shock waves occur in nature in the air surrounding explosions (the shock wave causes much of the destruction of buildings, etc., in an atomic bomb blast) and in the sudden closing of a valve in a duct with high-velocity flow. Sonic booms are shock waves. Shock waves can be produced in the laboratory in a duct or nozzle with supersonic flow. In such cases the shock wave will stand still in one place while the fluid flows through it. The latter is the easier to analyze mathematically, so we use it as a basis for calculations. The nomenclature for a shock wave is shown in Fig 8.13. 

Our discussion has been restricted to shock waves in which the flow is perpendicular to the wave that is the only kind which can occur in onedimensional flow. Such waves are called normal shock waves or normal shocks because of the perpendicular relationship. In two-dimensional flow, another kind, called an oblique shock., occurs, in which the flow is not perpendicular to the shock wave. Oblique shock waves form at the leading edge of the wings of supersonic aircraft and cause sonic booms for a discussion of them see Shapiro [5]. 

A noise of short duration (typically less than one second), especially of high intensity, abrupt onset, and rapid decay, and often rapidly changing spectral composition. Impulse noises are characteristically associated with such sources as explosions, impacts, firearm discharges, sonic booms, and many industrial processes. 

The sonic boom generated on the ground by an aircraft flying at supersonic speeds produces a pressure change shaped like the letter N a sharp increase, a more gradual decrease and a sharp recovery at the end. 

Aircraft traveling faster than the speed of sound create a sonic boom, a large pressure wave experienced as an explosion. This stardes people, breaks windows, and damages structures. Commercial aircraft are therefore prohibited from flying at supersonic speeds over land areas. 

A child tosses a stone into a lake. He delights in watching capillary waves propagate by forming circular ripples on the water s surface. All of us have heard the sonic boom produced by an aircraft crossing the sound barrier. But how many of us are aware that we can also observe shock waves of capillary origin every day when we turn our kitchen faucet on on the bottom of the sink water flows outward as a thin film. But a few centimeters away from the center, we see a hydraulic jump—very similar to a shock ... 

The characteristic blue glow in the water surrounding the core is called Cerenkov radiation. It results when charged particles pass through a transparent medium faster than does light in the same medium. The charged particles are produced by nuclear fission. The radiation is analogous to the shock wave produced in a sonic boom. 

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