A Numerical Investigation of the Flow Field Developed Behind (A) An Oblique Shock Wave Propagating into a Dusty Gas (B) A Normal Shock Wave Propagating into a Dusty Gas Having Dust Particles of Various Size

1988 ◽  
Author(s):  
G. Ben-Dor ◽  
O. Igra

Supersonic flows of a dusty gas past a wedge are studied theoretically. An oblique shock wave emanates from the apex of the wedge at the same angle as in the case of a pure gas, but bends back because of the presence of the particles. It is shown from an equilibrium-gas analysis that the extent of decrease in the shock-wave angle is larger for smaller velocity of the uniform stream. When the flow-deflection angle is small enough, the oblique shock wave developing fully at large distances from the apex has a fully dispersed transition structure. On the other hand, it is partly dispersed when the flow-deflection angle is large. Details of the development of the oblique shock wave as the distance from the apex increases are clarified by solving the equations of motion numerically. The particles colliding with the wedge are assumed to stick to or reflect elastically from its surface. It is shown that the reflected particles affect the flow significantly in the neighbourhood of the wedge.


1988 ◽  
Vol 41 (11) ◽  
pp. 379-437 ◽  
Author(s):  
O. Igra ◽  
G. Ben-Dor

The flow field developed behind shock waves in a pure gaseous medium is well known and documented in all gasdynamics textbooks. This is not the case when the gaseous medium is seeded with small solid particles. The present review treats various cases of shock waves propagation into a gas-dust suspension (dusty shock waves). It starts (chapter 1) with basic definitions of two-phase (gas-dust) suspensions and presents a general form of the conservation equations which govern dusty shock wave flows. In chapter two, the simple case of a steady flow of a suspension consisting of an inert dust and a perfect gas through a normal shock wave is studied. The effect of the dust presence, and of changes in its physical parameters, on the post-shock wave flow are discussed. Obviously, these discussions are limited to relatively weak shock waves (perfect gas). For stronger normal shock waves, the assumption of a perfect gas no longer holds. Therefore, in chapter three, real gas effects (ionization or dissociation) are taken into account when calculating the post-shock flow field. In chapter four, the dust chemistry is included and its effects on the post-shock flow is studied. In order to emphasize the role played by the dust chemistry, a comparison between a reactive and a similar inert suspension is presented. The case of an oblique shock wave in a dusty gas is discussed in chapter five. In all cases treated in chapters two to five the flow is steady; however, in many engineering applications this is not the case. In reality, even for the simplest case of a one-dimensional flow (normal shock wave propagation into quiescent suspension—the dusty shock tube) the shock wave attenuates and the flow field behind it is not steady. This case is treated in chapter six. The cases treated in chapters two to six deal with planar shock waves. However, all explosion generated shock waves in the atmosphere are spherical. Due to the engineering importance of this case, the post-shock flow for spherical shock waves in a dusty gas is studied, in detail, in chapter seven. It is shown in the present review that the dust presence has significant effects on the post-shock flow field. In all cases studied, a relaxation zone is developed behind the shock wave front. Throughout this zone momentum and energy exchange between the two phases of the suspension takes place. Through these interactions a new state of equilibrium is reached. The extent of the relaxation zone depends upon the dust loading ratio, the dust particle diameter, its specific heat capacity, and the dust spatial density. Due to the complexity of conducting experimental investigations with dusty shock waves, the number of published experimental results is very limited. As a result most of the present review contains numerical studies. However, in the few cases where experimental data are available, (e.g. dusty shock tube flow; see chapter six) a comparison between the numerical and experimental results is given.


Author(s):  
Yuming Yang ◽  
Li Zhou ◽  
Jingwei Shi

Abstract TBCC ejector nozzle is the key component of the propulsion system of hypersonic vehicle to increase the thrust characteristic of the whole envelope. Aiming at the exhaust system of TBCC engine with the first stage of Ma 0 ∼ 3, the complex internal and external flow interference characteristics of TBCC ejector nozzle are analyzed and the influence of key aerodynamic and geometric parameters are studied. 1) The secondary throat produces a strong oblique shock wave in the primary flow, that reflects with the oblique shock wave at the exit of the nozzle and forms the complex flow field characteristics of the ejector nozzle. 2) The introduction of the secondary flow will not change the flow field structure of the nozzle, but can significantly reduce the intensity of shock system in the sleeve and improve the thrust performance of the nozzle; the aerodynamic throat of the primary flow appears separation because of the high pressure secondary flow, which resulting in the flow mismatching and choking of the primary nozzle. 3) Under the severe over expansion state, the thrust performance is higher when the expansion angle is reduced; The increase of the secondary throat diameter ratio can improve the over expansion state of the primary flow and increase the thrust performance; the increase of the spacing ratio causes the increase of the secondary mass rate and the decrease of the primary mass rate, but the thrust performance is less affected.


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