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Gas kinetics is a science in the branch of fluid dynamics, concerned with the study of motion of gases and its effects on physical systems. Based on the principles of fluid mechanics and thermodynamics, gas dynamics arises from the studies of gas flows in transonic and supersonic flights. To distinguish itself from other sciences in fluid dynamics, the studies in gas dynamics are often defined with gases flowing around or within physical objects at speeds comparable to or exceed the speed of sound and causing a significant change in temperature and pressure. Some examples of these studies include but are not limited to: choked flows in nozzles and valves, shock waves around jets, aerodynamic heating on atmospheric reentry vehicles and flows of gas fuel within a jet engine. At the molecular level, gas dynamics is a study of the kinetic theory of gases, often leading to the study of gas diffusion, statistical mechanics, chemical thermodynamics and non-equilibrium thermodynamics. Gas dynamics is synonymous with aerodynamics when the gas field is air and the subject of study is flight. It is highly relevant in the design of aircraft and spacecraft and their respective propulsion systems. ==History== Progress in gas dynamics coincides with the developments of transonic and supersonic flights. As aircraft began to travel faster, the density of air began to change, considerably increasing the air resistance as the air speed approached the speed of sound. The phenomenon was later identified in wind tunnel experiments as an effect caused by the formation of shock waves around the aircraft. Major advances were made to describe the behavior during and after World War II, and the new understandings on compressible and high speed flows became theories of gas dynamics. As the construct that gases are small particles in Brownian motion became widely accepted and numerous quantitative studies verifying that the macroscopic properties of gases, such as temperature, pressure and density, are the results of collisions of moving particles, the study of kinetic theory of gases became increasingly an integrated part of gas dynamics. Modern books and classes on gas dynamics often began with an introduction to kinetic theory.〔 The advent of the molecular modeling in computer simulation further made kinetic theory a highly relevant subject in today's research on gas dynamics.〔 〕〔 〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Gas kinetics」の詳細全文を読む スポンサード リンク
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