Mach number in the context of "Ramjet"

Compressible flow (or gas dynamics) is the branch of fluid mechanics that deals with flows having significant changes in fluid density. While all flows are compressible, flows are usually treated as being incompressible when the Mach number (the ratio of the speed of the flow to the speed of sound) is smaller than 0.3 (since the density change due to velocity is about 5% in that case). The study of compressible flow is relevant to high-speed aircraft, jet engines, rocket motors, high-speed entry into a planetary atmosphere, gas pipelines, commercial applications such as abrasive blasting, and many other fields.

The McDonnell Douglas F-4 Phantom II is an American tandem two-seat, twin-engine, all-weather, long-range supersonic jet interceptor and fighter-bomber that was developed by McDonnell Aircraft for the United States Navy. It entered service with the Navy in 1961, then was adopted by the United States Marine Corps, and the United States Air Force, and within a few years became a major part of their air arms. A total of 5,195 Phantoms were built from 1958 to 1981, making it the most-produced American supersonic military aircraft in history and a signature combat aircraft of the Cold War.

The Phantom is a large fighter with a top speed of over Mach 2.2. It can carry more than 18,000 pounds (8,400 kg) of weapons on nine external hardpoints, including air-to-air missiles, air-to-ground missiles, and various bombs. Like other interceptors of its time, the F-4 was initially designed without an internal cannon, but some later models incorporated an internal M61 Vulcan rotary cannon. Beginning in 1959, it set 15 world records for in-flight performance, including an absolute speed record and an absolute altitude record.

Ernst Waldfried Josef Wenzel Mach (/mɑːx/ MAHK; Austrian German: [ˈɛrnst ˈmax] ; 18 February 1838 – 19 February 1916) was an Austrian physicist and philosopher, who contributed to the understanding of the physics of shock waves. The ratio of the speed of a flow or object to that of sound is named the Mach number in his honor. As a philosopher of science, he was a major influence on logical positivism and American pragmatism. Through his criticism of Isaac Newton's theories of space and time, he foreshadowed Albert Einstein's theory of relativity.

Supersonic speed is the speed of an object that exceeds the speed of sound (Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately 343.2 m/s (1,126 ft/s; 768 mph; 667.1 kn; 1,236 km/h). Speeds greater than five times the speed of sound (Mach 5) are often referred to as hypersonic. Flights during which only some parts of the air surrounding an object, such as the ends of rotor blades, reach supersonic speeds are called transonic. This occurs typically somewhere between Mach 0.8 and Mach 1.2.

Sounds are traveling vibrations in the form of pressure waves in an elastic medium. Objects move at supersonic speed when the objects move faster than the speed at which sound propagates through the medium. In gases, sound travels longitudinally at different speeds, mostly depending on the molecular mass and temperature of the gas, and pressure has little effect. Since air temperature and composition varies significantly with altitude, the speed of sound, and Mach numbers for a steadily moving object may change. In water at room temperature, supersonic speed means any speed greater than 1,440 m/s (4,724 ft/s). In solids, sound waves can be polarized longitudinally or transversely and have higher velocities.

A test pilot is an aircraft pilot with additional training to fly and evaluate experimental, newly produced and modified aircraft with specific maneuvers, known as flight test techniques.

An air knife is a tool used to blow off liquid or debris from products as they travel on conveyors. Air knives are normally used in manufacturing or as the first step in a recursive recycling process to separate lighter or smaller particles from other components for use in later or subsequent steps, post manufacturing parts drying and conveyor cleaning, part of component cleaning. The knife consists of a high-intensity, uniform sheet of laminar airflow sometimes known as streamline flow.

An industrial air knife is a pressurized air plenum containing a series of holes or continuous slots through which pressurized air exits in a laminar flow pattern. The exit air velocity then creates an impact air velocity onto the surface of whatever object the air is directed. This impact air velocity can range from a gentle breeze to greater than Mach 0.6 (40,000 ft/min) to alter the surface of a product without mechanical contact.

This is a list of the fastest animals in the world, by types of animal. The peregrine falcon is the fastest bird, and the fastest member of the animal kingdom, with a diving speed of over 300 km/h (190 mph). The fastest land animal is the cheetah. Among the fastest animals in the sea is the black marlin, with uncertain and conflicting reports of recorded speeds.

When drawing comparisons between different classes of animals, an alternative unit is sometimes used for organisms: body length per second. The average body length per second in the world is just around 67. On this basis the 'fastest' organism on earth, relative to its body length, is the Southern Californian mite, Paratarsotomus macropalpis, which has a speed of 322 body lengths per second. The equivalent speed for a human, running as fast as this mite, would be 1,300 mph (2,092 km/h), or approximately Mach 1.7. The speed of the P. macropalpis is far in excess of the previous record holder, the Australian tiger beetle Rivacindela eburneola, which is the fastest insect in the world relative to body size, with a recorded speed of 1.86 metres per second (6.7 km/h; 4.2 mph), or 171 body lengths per second. The cheetah, the fastest land mammal, scores at only 16 body lengths per second. Body mass can also be used to compare speed between species on a relative basis. Under this parameter the fastest animal for its body mass is the cheetah, followed by the pronghorn.

A diffuser is "a device for reducing the velocity and increasing the static pressure of a fluid passing through a system”. The fluid's static pressure rise as it passes through a duct is commonly referred to as pressure recovery. In contrast, a nozzle is used to increase the discharge velocity and lower the pressure of a fluid passing through it.

Frictional effects during analysis can sometimes be important, but usually they are neglected. Ducts containing fluids flowing at low velocity can usually be analyzed using Bernoulli's principle. Analyzing ducts flowing at higher velocities with Mach numbers in excess of 0.3 usually require compressible flow relations.

The Rockwell B-1 Lancer is a supersonic variable-sweep wing, heavy bomber used by the United States Air Force. It has been nicknamed the "Bone" (from "B-One"). As of 2024, it is one of the U.S. Air Force's three strategic bomber types, along with the B-2 Spirit and the B-52 Stratofortress. It carries up to a 75,000-pound (34,000 kg) payload.

The B-1 was first envisioned in the 1960s as a bomber that would combine the Mach 2 speed of the B-58 Hustler with the range and payload of the B-52, ultimately replacing both. After a long series of studies, North American Rockwell (subsequently renamed Rockwell International, B-1 division later acquired by Boeing) won the design contest for what emerged as the B-1A. Prototypes of this version could fly Mach 2.2 at high altitude and long distances and at Mach 0.85 at very low altitudes. The program was canceled in 1977 due to its high cost, the introduction of the AGM-86 cruise missile that flew the same basic speed and distance, and early work on the B-2 stealth bomber.