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Grossly overexpanded nozzles have improved efficiency, but the exhaust jet is unstable. Conventional nozzles become progressively more underexpanded as they gain altitude. [1] The basic concept of any engine bell is to efficiently direct the flow of exhaust gases from the rocket engine into one direction.
The gas flow rate is constant (i.e., steady) during the period of the propellant burn. The gas flow is non-turbulent and axisymmetric from gas inlet to exhaust gas exit (i.e., along the nozzle's axis of symmetry). The flow is compressible as the fluid is a gas. As the combustion gas enters the rocket nozzle, it is traveling at subsonic velocities.
Choked flow is a limiting condition where the mass flow cannot increase with a further decrease in the downstream pressure environment for a fixed upstream pressure and temperature. For homogeneous fluids, the physical point at which the choking occurs for adiabatic conditions is when the exit plane velocity is at sonic conditions; i.e., at a ...
A supersonic flow that is turned while there is an increase in flow area is also isentropic. Since there is an increase in area, therefore we call this an isentropic expansion. If a supersonic flow is turned abruptly and the flow area decreases, the flow is irreversible due to the generation of shock waves.
A Reynolds number of less than 2300 is laminar fluid flow, which is characterized by constant flow motion, whereas a value of over 4000, is represented as turbulent flow. [16] Due to its smaller radius and lowest velocity compared to other vessels, the Reynolds number at the capillaries is very low, resulting in laminar instead of turbulent flow.
The flow profiles was first derived by John R. Womersley (1907–1958) in his work with blood flow in arteries. [1] The cardiovascular system of chordate animals is a very good example where pulsatile flow is found, but pulsatile flow is also observed in engines and hydraulic systems, as a result of rotating mechanisms pumping the fluid.
Shock is the state of insufficient blood flow to the tissues of the body as a result of problems with the circulatory system. Initial symptoms of shock may include weakness, tachycardia, hyperventilation, sweating, anxiety, and increased thirst. [1] This may be followed by confusion, unconsciousness, or cardiac arrest, as complications worsen. [1]
Pronunciation follows convention outside the medical field, in which acronyms are generally pronounced as if they were a word (JAMA, SIDS), initialisms are generally pronounced as individual letters (DNA, SSRI), and abbreviations generally use the expansion (soln. = "solution", sup. = "superior").