An incoming ocean wave has a slightly higher wave speed near the crest of each wave than near the troughs between waves, because the wave height is not infinitesimal compared to the depth of the water. The crests overtake the troughs until the leading edge of the wave forms a vertical face and spills over to form a turbulent shock a breaker that dissipates the wave's energy as sound and heat. Similar phenomena affect strong sound waves in gas or plasma, due to the dependence of the sound speed on temperature and pressure.
Strong waves heat the medium near each pressure front, due to adiabatic compression of the air itself, so that high pressure fronts outrun the corresponding pressure troughs. There is a theory that the sound pressure levels in brass instruments such as the trombone become high enough for steepening to occur, forming an essential part of the bright timbre of the instruments.
A shock wave may be described as the furthest point upstream of a moving object which "knows" about the approach of the object. In this description, the shock wave position is defined as the boundary between the zone having no information about the shock-driving event and the zone aware of the shock-driving event, analogous with the light cone described in the theory of special relativity.
To produce a shock wave, an object in a given medium such as air or water must travel faster than the local speed of sound. In the case of an aircraft travelling at high subsonic speed, regions of air around the aircraft may be travelling at exactly the speed of sound, so that the sound waves leaving the aircraft pile up on one another, similar to a traffic jam on a motorway.
When a shock wave forms, the local air pressure increases and then spreads out sideways. Because of this amplification effect, a shock wave can be very intense, more like an explosion when heard at a distance not coincidentally, since explosions create shock waves.
Analogous phenomena are known outside fluid mechanics. For example, particles accelerated beyond the speed of light in a refractive medium where the speed of light is less than that in a vacuum , such as water create visible shock effects, a phenomenon known as Cherenkov radiation.
Shock waves can also occur in rapid flows of dense granular materials down inclined channels or slopes. Strong shocks in rapid dense granular flows can be studied theoretically and analyzed to compare with experimental data. Consider a configuration in which the rapidly moving material down the chute impinges on an obstruction wall erected perpendicular at the end of a long and steep channel.
Impact leads to a sudden change in the flow regime from a fast moving supercritical thin layer to a stagnant thick heap. This flow configuration is particularly interesting because it is analogous to some hydraulic and aerodynamic situations associated with flow regime changes from supercritical to subcritical flows.
Astrophysical environments feature many different types of shock waves. Some common examples are supernovae shock waves or blast waves travelling through the interstellar medium, the bow shock caused by the Earth's magnetic field colliding with the solar wind and shock waves caused by galaxies colliding with each other. Another interesting type of shock in astrophysics is the quasi-steady reverse shock or termination shock that terminates the ultra relativistic wind from young pulsars. The Tunguska event and the Russian meteor event are the best documented evidence of the shock wave produced by a massive meteoroid.
Shock wave - Wikipedia
In the examples below, the shock wave is controlled, produced by ex. The wave disk engine also named "Radial Internal Combustion Wave Rotor" is a kind of pistonless rotary engine that utilizes shock waves to transfer energy between a high-energy fluid to a low-energy fluid, thereby increasing both temperature and pressure of the low-energy fluid. In memristors , under externally-applied electric field, shock waves can be launched across the transition-metal oxides, creating fast and non-volatile resistivity changes.
Advanced techniques are needed to capture shock waves and to detect shock waves in both numerical computations and experimental observations. Computational fluid dynamics is commonly used to obtain the flow field with shock waves. Though shock waves are sharp discontinuities, in numerical solutions of fluid flow with discontinuities shock wave, contact discontinuity or slip line , the shock wave can be smoothed out by low-order numerical method due to numerical dissipation or there are spurious oscillations near shock surface by high-order numerical method due to Gibbs phenomena.
There exist some other discontinuities in fluid flow than the shock wave.
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The slip surface 3D or slip line 2D is a plane across which the tangent velocity is discontinuous, while pressure and normal velocity are continuous. Across the contact discontinuity, the pressure and velocity are continuous and the density is discontinuous. A strong expansion wave or shear layer may also contain high gradient regions which appear to be a discontinuity. Some common features of these flow structures and shock waves and the insufficient aspects of numerical and experimental tools lead to two important problems in practices: In fact, correct capturing and detection of shock waves are important since shock waves have the following influences: From Wikipedia, the free encyclopedia.
For other uses, see Shockwave disambiguation. For the Transformers character, see Micromasters. This article includes a list of references , but its sources remain unclear because it has insufficient inline citations. Please help to improve this article by introducing more precise citations. September Learn how and when to remove this template message. Shock waves in astrophysics. January , Fundamentals of Aerodynamics 3rd ed. Physics of shock waves and high-temperature hydrodynamic phenomena. Fluid Mechanics, Volume 6 of course of theoretical physics.
Supersonic flow and shock waves Vol. The dynamics and thermodynamics of compressible fluid flow, vol. Ronald Press, New York. Elements of gas dynamics. Pergamon Press, Oxford, England: Surfing the Quantum World Frank S. Theory and Molecular Simulation Mark Tuckerman. Middle World Mark Haw.
Solid-State Physics Harald Ibach. Phase Transitions Ricard V. Atomic Force Microscopy Paul West. The Nature of Solids Alan Holden. Test Methods for Explosives Muhamed Suceska. Physics of Continuous Matter B. A Truly Complex Fluid S. Scanning Probe Microscopy Bert Voigtlander. Statistical Physics and Thermodynamics Jochen Rau.
Statistical Field Theory Giuseppe Mussardo. Group Theory Ado Jorio.
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Other books in this series. Explosive Effects and Applications William Walters. Shock Focusing Phenomena Nicholas Apazidis. Blast Waves Charles E. Fragmentation of Rings and Shells Dennis Grady. Blast Effects Isabelle Sochet. Back cover copy Research in the field of shock physics and ballistic impact has always been intimately tied to progress in development of facilities for accelerating projectiles to high velocity and instrumentation for recording impact phenomena.
Among the more technologically-oriented applications treated is the testing of the flight characteristics of aeroballistic models and the assessment of impacts in the aerospace industry. Table of contents Light-Gas Gun Technology: