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Topic: Critical Mach number

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	High speed Aerodynamics
		It is shown the cruise speed of some notable aircraft in the year of entry into service (some data are not labelled for clarity).
		The critical Mach number is the free stream Mach number at which sonic flow first appears on the airfoil/wing.
		Critical Mach numbers can be estimated in several ways, including the methods of Relf-Jacobs, Von Karman, Prandtl-Glauert, and Temple-Yarwood.
	www.aerodyn.org /HighSpeed/highspeed.html (843 words)

	Critical mach: Dictionary definition
		Critical mach is a aeronautics term that refers to the speed at which some of the airflow on a wing becomes supersonic.
		This effect led to a number of accidents in the 1930s and 1940s, when aircraft in a dive would hit critical mach and continue to push over into a steeper and steeper dive.
		For instance, the fairly thick wing on the P-38 Lightning led to a critical mach of about.69 Mach, a speed it could reach with some ease in dives, which lead to a number of crashes.
	www.encyclopedian.com /cr/Critical-mach.html (462 words)

	Critical Mach number - Wikipedia, the free encyclopedia
		The Critical Mach number (Mcr) is the maximum Mach number (airspeed in relation to the speed of sound - Mach 1.0) which a subsonic aircraft can attain whilst still remaining controllable by the pilot.
		Although unknown at the time, the Critical Mach number was the cause of the effect known as the 'sound barrier' which was being observed in the late 1930's/early 1940's.
		Transonic aircraft, e.g., Hawker Hunter, F-86 Sabre are designed to have no Critical Mach number and while not possessing sufficient engine power to do so in level flight, can be dived to above the speed of sound and remain controllable.
	en.wikipedia.org /wiki/Critical_Mach_number (202 words)

	High speed Aerodynamics
		From an applied point of view flows with a free stream Mach number below 0.6 are treated as low subsonic flows (provided no shock waves occur) and compressibility corrections to speeds and pressure are performed using some well known theories: Prandlt-Glauert-Gothert and Karman-Tzien for external flows; Lieblein-Stockmann for internal flows.
		The critical Mach number is the free stream Mach number at which sonic flow first appears on the airfoil/wing.
		Critical Mach numbers can be estimated in several ways, including the methods of Relf-Jacobs, Von Karman, Prandtl-Glauert, and Temple-Yarwood.
	aerodyn.org /HighSpeed/highspeed.html (854 words)

	ch10-4
		The critical Mach number of a wing is the flight Mach number of the aircraft at which the local Mach number at some point of the wing becomes 1.0.
		The effect of sweepback on the critical Mach number of finite wings is usually analyzed in terms of a wing of given aspect ratio and airfoil thickness ratio in the free-stream direction.
		The dramatic reduction in drag coefficient at Mach numbers in excess of 1.0 as the airfoil thickness ratio is reduced from 9 to 4 percent is obvious.
	www.hq.nasa.gov /office/pao/History/SP-468/ch10-4.htm (5875 words)

	Mach_Number.htm
		Mach number has been tossed around so often in the popular press since the 1950's that the word has seeped in to the public argot.
		The Mach number, named after the Austrian scientist Ernst Mach (1836-1916), is the ratio of a velocity of an object in a fluid medium to the speed of sound in the medium.
		At Mach numbers beyond 0.7 or so the fact that the air is compressible has an increasing influence on the flow around a body.
	www.geocities.com /CapeCanaveral/Galaxy/4707/Aeronotes/Mach_Number.htm (808 words)

	Aerospaceweb.org \| Ask Us - Supercritical Airfoils
		Thus, an aircraft flying at half the speed of sound is said to be flying at Mach 0.5 while an aircraft flying at the speed of sound is said to be flying sonic, or at Mach 1.
		Although the exact range of transonic Mach numbers will vary for different aircraft configurations and operating conditions, the transonic regime is generally said to be between Mach 0.7 or 0.8 and Mach 1.2 or 1.3.
		These airfoils have critical Mach numbers very close to one (hence the term supercritical) thereby delaying and reducing the large increase in drag due to wave drag.
	www.aerospaceweb.org /question/airfoils/q0003.shtml (843 words)

	AIR FORCE
		At approximately.90 Mach number trim change previously mentioned reversed and the tendency was for the nose to rise and in the range of approximately.92 Mach number the buffeting became quite severe.
		The maximum Mach number of 1.35 was attained in a flight on 6 November 1947 at an altitude of 48,000 feet.
		As the Mach number is increased further, the static pressure is affected by the bow wave at the nose of the head.
	www.hq.nasa.gov /office/pao/History/x1/afsrax.html (13668 words)

	Research Gallery (Site not responding. Last check: 2007-11-03)
		The free-stream Mach number (the ratio of the free-stream velocity to its speed of sound) at critical is the critical Mach number of the airfoil.
		A critical airfoil is considered to be optimal if it has the highest critical Mach number for a given thickness (and possibly other geometric constraints) and lift.
		A method of construction of optimal critical airfoils, within the mathematical framework of steady, inviscid, potential flow, uses the hodograph transformation in which the equations of motion of the flow are changed from the physical (x,y) plane to the hodograph (u,v) plane, where (u,v) are the components of the flow velocity.
	www.math.rpi.edu:16080 /faculty/Schwendeman/Research/hodograph.html (408 words)

	wiki/Critical mach Definition / wiki/Critical mach Research (Site not responding. Last check: 2007-11-03)
		Critical mach is a aeronauticsAeronautics includes: (The AGARD and BS185 definition) All activities relating to aerial locomotion, e.i.
		This problem is often lumped in with the catch-all phrase compressibilityCompressibility (physics) is a measure of the relative volume change of fluid or solid as a response to a pressure (or mean stress) change:....
		It is defined as the range of speeds between critical mach, when some parts of the airflow over an aircraft become supersonic, and a higher speed, typically near Mach 1.2, when all of the airflow is supersonic.
	www.elresearch.com /wiki/Critical_mach (695 words)

	[No title]
		Mach kritiek is the free stream mach number at which: A somewhere about the airframe mach 1 is reached locally B shockstall occurs C the critical AOA is reached D mach buffet occurs 21.
		The mach trim system will: A pump the fuel from tank to tank, depending on the mach number B adjust the elevator trim tab, depending on the mach number C adjust the stabilizer, depending on the mach number D keep the mach number automatically constant 33.
		When the air has passed through a normal shock wave the mach number is: A lower than before but still greater than 1 B less than 1 C higher than before D equal to 1 37.
	members.home.nl /cboer/pof1.txt (1225 words)

	Assignment #2 (Site not responding. Last check: 2007-11-03)
		is the coefficient of friction due to a laminar boundary layer and Re is the Reynold’s number of the flow in the x-direction.
		Critical Mach number versus angle of attack for the biconvex airfoil.
		is the critical Mach number for the wing.
	www.prism.gatech.edu /~gte230w/Assignment2.htm (1922 words)

	NACA0012 Airfoil Drag Rise - Mach 0.50
		Red represents regions of high Mach number (mostly on the upper surface where the flow is being accelerated) and blue represents regions of low Mach number (mostly at the stagnation point regions in the leading and trailing edge areas).
		The sonic line (countour line where the Mach number is exactly 1.0) is shown as a faint white line when sonic flow exists.
		Drag divergence occurs somewhere between Mach 0.65 and 0.70 for this airfoil.
	adg.stanford.edu /aa241/drag/dragrise.html (375 words)

	AE3021 Test 2 (Site not responding. Last check: 2007-11-03)
		The airfoil of a wing is set at an angle of attack where the suction peak pressure coefficient in incompressible flow is –0.3.
		A supersonic 2-D configuration resembles the bottom portion of a diamond-section airfoil, i.e, the upper surface is flat, and the lower surface consists of two inclined flat surfaces.
		At a freestream Mach number of 2, and an angle of attack of 2 degrees, find the lift and drag coefficients and the pitching moment coefficient about the leading edge.
	www.adl.gatech.edu /classes/ae3021/f03_qns_031101.html (507 words)

	mach number
		If an object travels through a medium, then its Mach number is the ratio of the object's speed to the speed of sound in that medium.
		It is a dimensionless number, typically used to describe the speed of aircraft.
		Mach 1 is equal to the speed of sound, Mach 2 is twice that speed, etc. Since the speed of sound increases as the temperature increases, the actual speed of an object traveling at Mach 1 will depend on its altitude and the atmospheric conditions.
	www.fact-library.com /mach_number.html (236 words)

	AllRefer.com - Ernst Mach (Physics, Biography) - Encyclopedia
		Mach, one of the leaders of modern positivism, did his major work in the philosophy of science.
		This view challenged science's traditional claim of yielding absolute knowledge and was greatly influential in the development of logical positivism.
		Mach also did research in the field of ballistics; the Mach number is named for him.
	reference.allrefer.com /encyclopedia/M/Mach-Ern.html (255 words)

	Wing-Fuselage Configuration
		In the Mach number range (0.9-0.95), there exists a critical Mach number for which the flow returns to a steady state.
		Furthermore, the flow is found to be governed by two instability processes in the Mach number range (0.75-0.8), where, apart from the von Kàrmàn mode (mode~I), a lower frequency mode~II appears, due to the formation of weakly supersonic alternating zones in the region upstream of the aerofoil, related to the buffeting phenomenon.
		When the Mach number is increased, the shock wave is pushed further downstream, interact with the wake vortices and the upstream flow becomes steady.
	www.aqflow.com /PROJECTS/transonic.html (344 words)

	Logical Positivism [Internet Encyclopedia of Philosophy] (Site not responding. Last check: 2007-11-03)
		Ernst Mach (1838-1916) -- physicist and philosopher, he taught physics at the University of Prague and theory of inductive science at Vienna -- is often regarded as a great source of inspiration to logical positivism (the official name of the Vienna Circle was Verein Ernst Mach, ie Ernst Mach Association).
		He was a radical empiricist, critized the absolute theory of space and time, published a philosophical and historical analysis of classical mechanics, and formulated the principle of economy of thought, according to which scientific theories are useful tools to make predictions, but they do not reflect an objective and independent reality.
		Mach was an anti-realist: there is nothing but our sensations; on these grounds, he never accepted the reality of atoms.
	www.iep.utm.edu /l/logpos.htm (9274 words)

	AERADE subject listing for AEROFOILS AND WINGS - Aerofoils at supersonic speeds. Critical Mach number and pressure ... (Site not responding. Last check: 2007-11-03)
		The variation of wave drag at zero lift for a symmetric double-wedge section and the variation with Mach number of aerodynamic centre position for a diamond section are illustrated in sketches.
		Critical pressure coefficient and component of local Mach number normal to the surface isobar for a swept wing.
		An equation (also given graphically) is derived for the Mach number of the flow component normal to an isobar by assuming that simple sweep theory can be applied locally; then the required Mach number is that normal to an infinite yawed wing of sweep equal to that of the isobar.
	aerade.cranfield.ac.uk /subject-listing/esdu/ES56.html (2471 words)

	Komet Me163 - Chief test pilot Rudy Opitz tells it like it was - Flight Journal.com Page 6 (Site not responding. Last check: 2007-11-03)
		The primary reason for the wing sweep was to improve the pitch moment arm of the elevons rather than to increase the critical Mach number of the airplane.
		The “critical Mach number” of the airplane is the flight Mach number at which the local flow first goes supersonic on the wing.
		As the Mach number increases, a shock wave forms at the aft boundary of the supersonic-flow bubble.
	www.flightjournal.com /articles/me163/me163_6.asp (1274 words)

	ch11-3
		At subsonic speeds, increasing sweepback angle increases the wing critical Mach number, that is, the Mach number at which the adverse effects of compressibility first begin to appear.
		The effect of sweepback on the critical Mach number was first pointed out in the United States by Robert T. Jones of NACA in 1945.
		A number are still in use as target drones and for various flight-test purposes, and at least one manufacturer uses an F-86 as a chase plane.
	www.hq.nasa.gov /office/pao/History/SP-468/ch11-3.htm (2381 words)

	Elliptic Particles (Site not responding. Last check: 2007-11-03)
		When the elasticity number is smaller than critical the fluid is essentially Newtonian with broadside-on falling at the centerline of the channel.
		For larger elasticity numbers the settling turns the longside of the particle along the stream in the channel center for all velocities below a critical one, identified with a critical Mach number of order one.
		The critical numbers are functions of the channel blockage ratio, the particle aspect ratio and the retardation/relaxation time ratio of the fluid.
	www.aem.umn.edu /Solid-Liquid_Flows/huang/papers/ellipse.html (247 words)

	Aerodynamics Example #1
		In the field of aerodynamics, airspeeds are usually stated in terms of Mach number, which is the local airspeed divided by the local speed of sound.
		, is the freestream Mach number at which sonic flow is first achieved on the airfoil.
		Assume you are trying to determine the critical Mach number of the NACA 0012 airfoil.
	www.akiti.ca /Mcrit.html (453 words)

	Research in Supersonic Flight and the Breaking of the Sound Barrier
		The Mach number is the ratio of the speed of a gas to the speed of sound in that gas.
		Mach, while a professor of physics at the University of Prague, took the first photographs of shock waves on a body moving at supersonic speeds.
		The critical Mach number is precisely defined as that freestream Mach number at which sonic flow is first encountered on the surface of a body.
	history.nasa.gov /SP-4219/Chapter3.html (12913 words)

	Hyper-X ED97-43968-1: Computational Fluid Dynamics (CFD) Image of Hyper-X Research Vehicle at Mach 7 with Engine ...
		The image illustrates surface heat transfer on the vehicle surface (red is highest heating) and flowfield contours at local Mach number.
		When the first of three aircraft flies, it will be the first time a non-rocket engine has powered a vehicle in flight at hypersonic speeds--speeds above Mach 5, equivalent to about one mile per second or approximately 3,600 miles per hour at sea level.
		The body of the vehicle itself forms critical elements of the engine.
	www.dfrc.nasa.gov /Gallery/Photo/X-43A/HTML/ED97-43968-1.html (545 words)

	AE 3021 Semester Project - 3.2 (Site not responding. Last check: 2007-11-03)
		A freestream Mach number of 0.6578 (that is, 0.7 cos 20) was used.
		Clearly, at a given Mach number, the critical Mach decreases rapidly as the angle of attack is increased.
		According to this plot, the critical Mach number at this angle is barely above 0.7, meaning that the plane is flying extremely close to the transonic region.
	www.prism.gatech.edu /~gte985m/ae3021/3-2.html (306 words)

	IHS ESDU: Data Item AERO W.00.03.01
		ESDU Aero W.00.03.01 gives theoretically-derived curves of critical Mach number plotted against thickness/chord ratio for a range of lift coefficients from zero to 0.5, and for an elliptic cylinder at zero lift.
		The curve for an elliptic cylinder at zero lift is given to provide an upper bound because such an aerofoil for a given thickness/chord ratio would have the lowest suction peak and hence the highest critical Mach number but it is not a practical section shape.
		The relationship between the critical Mach number and the Mach number for shock-induced separation is discussed.
	www.esdu.com /graphics/dataitem/aw31b.htm (159 words)

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