A great number of scientific publications have been dedicated to the study of this problem, which stemmed from the second half of the 18th century. Such waves arise in consequence of disturbance of these surfaces and depending on the volume of disturbance, they may be either linear (when disturbances of parameters of liquids are much less than their equilibrium value) or nonlinear (when disturbances of parameters of liquids are bigger or of the order of their equilibrium value). Surface gravity waves are generated and propagated on the interface of two liquids therefore, while studying them, the methods of theory of hydrodynamic tangential gap are applied. The paper considers the applied problems of hydrodynamics and based on the new results, published by the author in recent years, shows that main assumptions used in the course of their solution, namely, incompressibility of liquids and potentiality of their movement, are not applicable to liquids in the gravitational field of the Earth. The results are used to generalize the counterpart adiabatic-system findings for the amount of boundary heat flux required for the silencing of vibroacoustic sound at nonadiabatic reference conditions. Considering the entire range of inverse power law (repulsion point center) interactions, it is also found that wave attenuation is affected by the kinetic model of gas collisions, yielding stronger decay rates in gases with softer molecular interactions. Primarily, reference wall heating results in an extension of the acoustic layer and consequent sound-wave radiation over larger distances from the wall source. The results of the approximate analysis, supported by continuum-model finite differences and direct simulation Monte Carlo calculations, clarify the impacts of system nonadiabaticity and the gas kinetic model of interaction on sound propagation. The application of thermoacoustic wall excitation necessitates the formation of an ever thinner "thermal layer" that governs the transmission of the wall's unsteady heat flux into sound waves. Focusing on continuum-limit conditions of small Knudsen numbers and high actuation frequencies (yet small compared with the mean collision frequency), the gas domain affected by wall excitation is confined to a thin layer (termed "acoustic layer") in the vicinity of the excited boundary, and an approximate solution is derived based on asymptotic expansion of the acoustic fields. Acoustic excitation is then enforced via small-amplitude harmonic wall oscillations and normal heat-flux perturbations. Considering a planar slab configuration, constant wall heating is applied at the confining walls to maintain the nonuniform reference thermodynamic distributions. To extend these studies, we analyze the propagation of acoustic waves in a slightly rarefied gas at nonadiabatic conditions, where arbitrarily large reference temperature and density gradients are imposed. Also bad.Existing works on sound propagation in rarefied gases have focused on wave transmission at adiabatic conditions, where a reference uniform equilibrium state prevails. The air over your wings will go supersonic, you'll pitch down, the aircraft will accelerate, and your wings will fall off. Get too fast, and you'll exceed your critical mach number. Get too slow, and you'll stall the jet at high altitude (not something you want to do). So, "Q Corner" is the techie name, but coffin corner sounds more dramatic. Coffin corner occurs from the interaction between stall speed and critical mach speed, which are both caused by pressure over your wing. The coffin corner's real name is the "Q Corner", because "Q" is the abbreviation for dynamic pressure. And that region of flight is called the "Coffin Corner" At a jet's operating ceiling, its Maximum Mach Number (MMO) is often extremely close to its stall speed. And in a piston airplane, V NE is about as far away from stall speed as you can get.īut, the same isn't true in a jet. Most of us have never had to worry about exceeding V NE - especially in level flight.
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