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Showing papers on "Rarefaction published in 1969"


Journal ArticleDOI
TL;DR: In this paper, the propagation and modification of the forward-reverse shock pair in the region between the sun and 1 AU were studied and it was concluded that a flare-associated forward reverse shock pair at 1 AU is unlikely unless the time duration of the solar disturbance is greater than about 5 hours.
Abstract: Numerical solutions of the time-dependent equations of motion for spherically symmetric flow are obtained to study the propagation and modification of the forward-reverse shock pair in the region between the sun and 1 AU. For cases where the duration of the disturbance is long compared to T, the shock transit time to 1 AU, a double shock pair that resembles those predicted by similarity theory occurs at 1 AU. In cases where the duration of the solar disturbance is less than about 0.45T, the shock pair structure is appreciably altered by a rarefaction, initiated at the end of the solar disturbance, which has caught up with the shock pair. In cases where the duration is less than about 0.1T, the rarefaction completely destroys the reverse shock, leaving a single shock. This analysis indicates that a forward-reverse shock pair will not be observed at 1 AU unless the time duration of the solar disturbance is greater than about 5 hours. Since solar flares that last this long are quite rare, it is concluded that observation of a flare-associated forward-reverse shock pair at 1 AU is unlikely.

42 citations


Journal ArticleDOI
TL;DR: In this article, the existence of compressive shocks is investigated for a mixture of a gas and small solid particles, which, far upstream, is in a constant equilibrium state, and moves with a constant velocity.
Abstract: A mixture of a gas and small solid particles is considered which, far upstream, is in a constant equilibrium state, and moves with a constant velocity. The existence of shock waves is investigated in the four possible cases, namely for frozen flow, for two kinds of partly frozen flow, and for equilibrium flow. It is shown that, in all these cases, compressive shocks may exist, if the upstream velocity exceeds the velocity of sound appropriate to the type of flow. Rarefaction shocks are impossible in each case. Moreover, it is shown that the downstream values of the flow parameters are determined uniquely, and the direction of their change is given. Only rather general assumptions concerning the behaviour of the gas are needed. The paper takes into account the influence of the finite particle volume fraction unlike most previous papers on the topic.

31 citations



Journal ArticleDOI
TL;DR: In this article, it is shown that the wave speed is between 6 and 9% higher than the steady case and is gradually approaching the speed of the steady wave as the rarefaction interacts with the wave front, reducing its speed.
Abstract: traces Al and A2 show the speed of overdriven waves such as shown in Fig. 2a (A2 is the speed record for Fig. 2a). It can be seen that the wave speed is between 6 and 9% higher than the steady case and is gradually approaching the speed of the steady wave as the rarefaction interacts with the wave front, reducing its speed. The traces Bl and B2 show the speed of a wave, as in Fig. 2b, where the shock has not overtaken the detonation when it passes the transducer. It is apparent that the shock does overtake the detonation soon after passing the transducer, as evidenced by the increase of up to 7% in wave-front speed. (B2 is the speed record for Fig. 2b.)

5 citations



Proceedings ArticleDOI
16 Jun 1969
TL;DR: In this paper, the rarefaction of a free jet expanding into a region of finite background pressure is considered and a simple scattering formulation of the complex physical problem is proposed, and a consistent physical description of a plume's approach to the limit of expansion into a perfect vacuum is discussed.
Abstract: In this paper the rarefaction of a free jet expanding into a region of finite background pressure is considered. It is found that the rarefaction process can be described by a simple rarefaction parameter D(P SP B^1^ / T . Here D is the sonic orifice diameter, P8 is the reservoir pressure, PBW is the background pressure and T is the background and reservoir temperatures which are considered to be the same. A simple scattering formulation of the complex physical problem is proposed. Comparison of the scattering prediction and previous molecular beam flux measurements by Fenn and Anderson are presented. A consistent physical description of a plume's approach to the limit of expansion into a perfect vacuum is discussed.

1 citations



Patent
13 Oct 1969
TL;DR: In this article, the free surface of the liquid to be distilled is subjected to cyclic pressure fluctuations occurring at an acoustic frequency to cause the pressure at the liquid surface to proceed through alternate rarefaction and compression modes.
Abstract: An acoustic distillation method and apparatus are provided wherein the free surface of the liquid to be distilled is subjected to cyclic pressure fluctuations occurring at an acoustic frequency to cause the pressure at the liquid surface to proceed through alternate rarefaction and compression modes. During the rarefaction modes, the vapor pressure at the free surface of the liquid is lowered to induce vaporization of liquid from the surface and conversion of liquid enthalpy into kinetic energy of the liquid vapor. The vapor is super heated during the compression modes and is thereafter passed in heat transfer relation to the incoming liquid to preheat the latter. In one disclosed embodiment, the acoustic pressure fluctuations are produced by a mechanically powered oscillating diaphragm. In a second disclosed embodiment, the acoustic pressure fluctuations are produced by an acoustical vapor engine.

1 citations