1. Aerodynamic
aerodynamic aerodynamic help edit Wikipedia card book of the same name is a branch of mechanics, the force which main characteristics of the object in the same relative movement of the gas as the gas flow pattern and accompanying physical and chemical changes. It is based on fluid mechanics, with the aviation industry and the development of jet propulsion technology and grew up in a discipline. A brief history of the various
development
mode of action of the first study of aerodynamics, can be traced back to human bird or projectile by the force and the force at the time of the flight guess. The late 17th century, the Dutch physicist Christiaan Huygens first estimate the resistance movement of objects in the air; in 1726, Newton applied mechanics principles and deductive methods drawn: the movement of the air force suffered object, the object is proportional to the movement and wherein the area density of the air and the square of the speed of the object. This work can be seen as the beginning of the classical theory of aerodynamics.
In 1755 the mathematician Euler come to describe inviscid fluid differential equations of motion, i.e. Euler equation. These differential form of kinetic equations can be integral under certain conditions, the results of very practical value. Half of the 19th century, Navier-Stokes and the United Kingdom, France proposed describing incompressible viscous fluid motion equations of conservation of momentum, later known as the Navier – Stokes equations. To the late 19th century, based on the classical hydrodynamics has been formed. Since the 20th century, with the rapid development of the aviation industry, aerodynamics begins in fluid mechanics developed and formed a new branch of mechanics.
the primary problem to be solved is how aviation give the power to get the aircraft needed to reduce aircraft drag and increase its flight speed. This study generates its laws when the aircraft and the air force on the relative motion from theory and practice. In 1894, British Lanchester first proposed the theory of infinite circulation wingspan wing or airfoil to generate lift force, and finite wing lift force generated vortex theory and so on.But Lanchester idea did not receive much attention at the time.
is about between 1901 and 1910, and Ru Khodorkovsky Kuta independently proposed airfoil and lifting force circulation theory, the mathematical theory of the form of lifting force, established a two-dimensional wing theory. In 1904, Germany’s Prandtl boundary layer theory published the famous low speed flows. The theory suggests that different flow equations in different regions may be in a simplified form.
boundary layer theory greatly promoted the development of aerodynamics. Prandtl also limited wing span of the three-dimensional theory of systematic, given its mathematical results, which created the lifting force line theory of finite wing. But it does not apply to stall, swept-back, and the case of small aspect ratio. 1946 Joan of America presented a small aspect ratio wing theory, the use of this theory and boundary layer theory, can be determined with sufficient accuracy the pressure distribution on the wing and surface friction.
the rapid development of modern aviation and jet technology makes flight speed rapidly increased. In the case of high-speed movement, fluid mechanics and thermodynamics must combine these two disciplines, in order to correctly understand and solve the problem of high-speed aerodynamics. Between 1887 ~ 1896, Austrian scientist Mach studying propagation projectile motion disturbances noted: in different flow greater than or less than the speed of sound, the disturbance caused by the propagation characteristics of the projectile is fundamentally different.
In the high-speed flow, the ratio of the flow velocity and the local speed of sound is an important dimensionless parameter. In 1929, the German aerodynamics home Arkwright first of this dimensionless parameter linked to Mach’s name, years later, this characteristic parameters Mach widely cited in gas dynamics.
Small perturbations in the propagation of supersonic flow are superimposed to form a limited amount of jump mdash; mdash; shock. In many practical flow supersonic shock wave also exist. Shock gas flow through the flow field, parameter jump occurs, and the entropy increase in the total energy remains constant.
British scientists Rankin in 1870, French scientists in 1887, Xi Gong twist independently establish a relationship of air flow through the shock wave to be fulfilled, provided the correct boundary for the mathematical processing supersonic flow field condition. For thin Ji small disturbance problem, Arkwright in 1925 proposed a two-dimensional line of aircraft wing theory,Accordingly, then to a line of a wing theory. Line theory these supersonic flow of a complete solution to the problem affecting the flow of small perturbations.
When the flow velocity near the flying velocity or speed of sound, the aerodynamic performance of the aircraft abrupt change, the sudden increase in resistance, lift dips. Handling and stability of the aircraft worsen, which is famous sound barrier in aviation history. The emergence of high-thrust engine crossed the sound barrier, but there is no good solution to the complex problem of transonic flow. Until after the 1960s, due to the requirements of transonic cruise flight, maneuvering, and the development of high-efficiency jet engines, research transonic flow more attention, and there is a great development.
develop long-range missiles and satellites to promote the development of hypersonic aerodynamics. In the early 50’s to 60’s, established the engineering calculation method hypersonic inviscid flow theory and aerodynamic forces. Early 1960s, hypersonic flow numerical calculation has also been rapid development. By studying these phenomena and laws, the development of high temperature gas dynamics, high-speed boundary layer flow theory and non-equilibrium theory.
Because at high temperatures can cause ablation and ejector aircraft surface material quality, need to study the high-temperature gas multiphase flow. The development of aerodynamics and the emergence of multi-disciplinary combination of features.
Another important aspect of the development of experimental aerodynamic research, including the development of various experimental development and test equipment wind tunnel theory, experimental methods, testing techniques. The world’s first wind tunnel was built in the UK Wenham 1871. Today for a variety of simulated conditions, wind tunnel purposes, uses and various measurement methods have been many dozens, content is extremely broad wind tunnel experiments.
Since the 70s of the 20th century, the rapid development of laser technology, electronics and computer technology, which greatly improved the level of experimental and computational aerodynamics level, and promote the flow of highly nonlinear and complex structure of the problem Research.
In addition to the aerodynamic development by promoting the development of aerospace industry outside, since the 1960s, due to various development traffic, transportation, construction, meteorology, environmental protection and energy utilization, there has been industry aerodynamics and other branches.