Editing Shock wave (section)

== Phenomenon types ==
Below are a number of examples of shock waves, broadly grouped with similar shock phenomena:

[[Image:Trinity explosion film strip.jpg|thumb|right| Shock wave propagating into a stationary medium, ahead of the fireball of an explosion. The shock is made visible by the [[shadowgraph|shadow effect]] (Trinity explosion).]]

=== Moving shock ===
* Usually consists of a shock wave propagating into a stationary medium
* In this case, the gas ahead of the shock is stationary (in the laboratory frame) and the gas behind the shock can be supersonic in the laboratory frame. The shock propagates with a wavefront which is normal (at right angles) to the direction of flow. The speed of the shock is a function of the original pressure ratio between the two bodies of gas.
* [[Moving shock]]s are usually generated by the interaction of two bodies of gas at different pressure, with a shock wave propagating into the lower pressure gas and an expansion wave propagating into the higher pressure gas.
* Examples: Balloon bursting, [[shock tube]], [[blast wave|shock wave from explosion]].

=== Detonation wave ===
{{Main|Detonation}}
* A [[detonation]] wave is essentially a shock supported by a trailing [[exothermic reaction]]. It involves a wave travelling through a highly combustible or chemically unstable medium, such as an oxygen-methane mixture or a [[high explosive]]. The chemical reaction of the medium occurs following the shock wave, and the chemical energy of the reaction drives the wave forward.
* A detonation wave follows slightly different rules from an ordinary shock since it is driven by the chemical reaction occurring behind the shock wavefront. In the simplest theory for detonations, an unsupported, self-propagating detonation wave proceeds at the [[Chapman–Jouguet condition|Chapman–Jouguet]] flow velocity. A detonation will also cause a shock to propagate into the surrounding air due to the overpressure induced by the explosion.
* When a shock wave is created by [[high explosive]]s such as [[trinitrotoluene|TNT]] (which has a [[detonation velocity]] of 6,900&nbsp;m/s), it will always travel at high, supersonic velocity from its point of origin.

[[Image:Photography of bow shock waves around a brass bullet, 1888.jpg|thumb|right|[[Schlieren photography|Schlieren photograph]] of the detached shock on a bullet in supersonic flight, published by Ernst Mach and Peter Salcher in 1887]]
[[File:Supersonic-bullet-shadowgram-Settles.tif|thumb|Shadowgram of shock waves from a supersonic bullet fired from a rifle. The shadowgraph optical technique reveals that the bullet is moving at about a Mach number of 1.9. Left- and right-running bow waves and tail waves stream back from the bullet and its turbulent wake is also visible. Patterns at the far right are from unburned gunpowder particles ejected by the rifle.]]

=== Bow shock (detached shock) ===
{{Main|Bow shock (aerodynamics)}}
* These shocks are curved and form a small distance in front of the body. Directly in front of the body, they stand at 90 degrees to the oncoming flow and then curve around the body. Detached shocks allow the same type of analytic calculations as for the attached shock, for the flow near the shock. They are a topic of continuing interest, because the rules governing the shock's distance ahead of the blunt body are complicated and are a function of the body's shape. Additionally, the shock standoff distance varies drastically with the temperature for a non-ideal gas, causing large differences in the heat transfer to the thermal protection system of the vehicle. See the extended discussion on this topic at [[atmospheric reentry]]. These follow the "strong-shock" solutions of the analytic equations, meaning that for some oblique shocks very close to the deflection angle limit, the downstream Mach number is subsonic. See also [[Bow shock (aerodynamics)|bow shock]] or [[oblique shock]].
* Such a shock occurs when the maximum deflection angle is exceeded. A detached shock is commonly seen on blunt bodies, but may also be seen on sharp bodies at low Mach numbers.
* Examples: Space return vehicles (Apollo, Space shuttle), bullets, the boundary ([[bow shock]]) of a [[magnetosphere]]. The name "bow shock" comes from the example of a [[bow wave]], the detached shock formed at the bow (front) of a ship or boat moving through water, whose slow surface wave speed is easily exceeded (see [[ocean surface wave]]).

=== Attached shock ===
* These shocks appear as ''attached'' to the tip of sharp bodies moving at supersonic speeds.
* Examples: Supersonic wedges and cones with small apex angles.
* The attached shock wave is a classic structure in aerodynamics because, for a perfect gas and inviscid flow field, an analytic solution is available, such that the pressure ratio, temperature ratio, angle of the wedge and the downstream Mach number can all be calculated knowing the upstream Mach number and the shock angle. Smaller shock angles are associated with higher upstream Mach numbers, and the special case where the shock wave is at 90° to the oncoming flow (Normal shock), is associated with a Mach number of one. These follow the "weak-shock" solutions of the analytic equations.

=== In rapid granular flows ===
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 flow|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.

=== In astrophysics ===
{{Main|Shock waves in astrophysics}}
Astrophysical environments feature many different types of shock waves. Some common examples are [[supernova]]e shock waves or [[blast wave]]s 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 [[galaxy|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 [[pulsar]]s.

==== Meteor entering events ====
[[File:Chelyabinsk meteor event consequences in Drama Theatre.jpg|thumb|Damage caused by [[Chelyabinsk meteor|a meteor shock wave]] ]]

Shock waves are generated by meteoroids when they enter the Earth's atmosphere.<ref>Silber E.A., Boslough M., Hocking W.K., Gritsevich M., Whitaker R.W. (2018). Physics of Meteor Generated Shock Waves in the Earth's Atmosphere – A Review. Advances in Space Research, 62(3), 489-532  https://doi.org/10.1016/j.asr.2018.05.010</ref> The [[Tunguska event]] and the [[2013 Russian meteor event]] are the best documented evidence of the shock wave produced by a [[Meteoroid#Notable meteors|massive meteoroid]].

When the 2013 meteor entered into the Earth's atmosphere with an energy release equivalent to 100 or more kilotons of TNT, dozens of times more powerful than the [[Little Boy|atomic bomb dropped on Hiroshima]], the meteor's shock wave produced damage as in a [[supersonic speed|supersonic]] jet's flyby (directly underneath the meteor's path) and as a [[detonation wave]], with the circular shock wave centred at the meteor explosion, causing multiple instances of broken glass in the city of [[Chelyabinsk]] and neighbouring areas (pictured).