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Mach number. The Mach number ( M or Ma ), often only Mach, ( / mɑːk /; German: [max]) is a dimensionless quantity in fluid dynamics representing the ratio of flow velocity past a boundary to the local speed of sound. [ 1][ 2] It is named after the Czech physicist and philosopher Ernst Mach . where: M is the local Mach number, u is the local ...
Air density, like air pressure, decreases with increasing altitude. It also changes with variations in atmospheric pressure, temperature and humidity . At 101.325 kPa (abs) and 20 °C (68 °F), air has a density of approximately 1.204 kg/m 3 (0.0752 lb/cu ft), according to the International Standard Atmosphere (ISA).
also called the magnetic field density or magnetic induction tesla (T), or equivalently, weber per square meter (Wb/m 2) capacitance: farad (F) heat capacity: joule per kelvin (J⋅K −1) constant of integration: varied depending on context speed of light (in vacuum) 299,792,458 meters per second (m/s) speed of sound
Dynamic pressure. In fluid dynamics, dynamic pressure (denoted by q or Q and sometimes called velocity pressure) is the quantity defined by: [1] where (in SI units): u is the flow speed in m/s. It can be thought of as the fluid's kinetic energy per unit volume . For incompressible flow, the dynamic pressure of a fluid is the difference between ...
Torricelli's law, also known as Torricelli's theorem, is a theorem in fluid dynamics relating the speed of fluid flowing from an orifice to the height of fluid above the opening. The law states that the speed of efflux of a fluid through a sharp-edged hole at the bottom of the tank filled to a depth is the same as the speed that a body would ...
Dimensionless numbers (or characteristic numbers) have an important role in analyzing the behavior of fluids and their flow as well as in other transport phenomena. [1] They include the Reynolds and the Mach numbers, which describe as ratios the relative magnitude of fluid and physical system characteristics, such as density, viscosity, speed of sound, and flow speed.
The speed of sound is the distance travelled per unit of time by a sound wave as it propagates through an elastic medium. More simply, the speed of sound is how fast vibrations travel. At 20 °C (68 °F), the speed of sound in air is about 343 m/s (1,125 ft/s; 1,235 km/h; 767 mph; 667 kn ), or 1 km in 2.91 s or one mile in 4.69 s.
Derived quantities can be expressed in terms of the base quantities. Note that neither the names nor the symbols used for the physical quantities are international standards. Some quantities are known as several different names such as the magnetic B-field which is known as the magnetic flux density , the magnetic induction or simply as the ...