Acceleration of a sphere behind planar shock waves

Britan, A. B.; Elperin, T.; Igra, O.; Jiang, Junping

doi:10.1007/bf00189297

Cited by 17 publications

(9 citation statements)

References 6 publications

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“…Dealing with the transient evolution of the shock wave reflection Shock wave reflection over a coupled convex-concave cylindrical surface 221 and related physical phenomena, one must employ very fast high-resolution imaging systems (Skews 2008). Over recent decades, studies in this field have dealt with a variety of problems such as: shock wave reflections from blunt objects including cylinders (Sun et al 2003;Skews & Kleine 2010;Glazer et al 2011;Kleine et al 2014), spheres (Britan et al 1995;Tanno et al 2003) and porous plates (Skews 2005); shock focusing (Johansson, Apazidis & Lesser 1999;Bond et al 2009;Skews & Kleine 2010) and the RR → MR and MR → RR transitions (Skews & Kleine 2007;Geva et al 2013;Gruber & Skews 2013). Some of these studies utilized high-speed photography with capturing rates ranging from a few thousand up to one million of frames per second (f.p.s.).…”

Section: Methodsmentioning

confidence: 99%

High spatial and temporal resolution study of shock wave reflection over a coupled convex–concave cylindrical surface

2015

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Studying the nature of transient reflections of shock waves from surfaces is important in many engineering fields, e.g. blast protection, supersonic flights, shock focusing, medical and industrial applications and more. The recent advancements in this field reveal that the major obstacle in better understanding this phenomenon by means of experimental investigations is the limited temporal and spatial resolution. An alternative approach to commonly used high-speed photography is based on the use of a single-lens reflex (SLR) camera that captures only one image per experiment. Using this method to study a transient reflection process necessitates repeating each experiment many times while retaining extremely high repeatability. In the present study, we present a solution to this obstacle by means of a fully automated shock tube facility, which has been developed in the course of this study. A typical experiment can be executed a few hundred times with a repeatability of less than 0.01 in the incident-shock-wave Mach number at moderate shock strengths (M = 1.2-1.4). The system offers a very high spatial and temporal resolution description of the transient reflection process of a shock wave over a coupled convex-concave surface. The study of this complex configuration using a fully automated shock tube enables one to observe, in greater detail than ever before, both the transient transition from regular reflection, RR, to Mach reflection, MR, and the reverse transient transition from MR to RR. The geometry studied can also be found in blunt leading-edge reflectors in which higher pressures were recorded, and the results presented also describe in detail the shock reflection process inside such a reflector. The results highlight and strengthen the recent understanding of the importance of high spatial and temporal resolution in determining the transition process from RR to MR over a coupled concave-convex surface. However, despite achieving very high statistical certainty in the experimental measurements, the question of the difference between the pseudo-steady transition criterion and the experimental results remains unresolved.

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Section: Methodsmentioning

confidence: 99%

High spatial and temporal resolution study of shock wave reflection over a coupled convex–concave cylindrical surface

2015

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“…Because of the importance of problems of shockwave propagation in dust-gas mixtures, a large number of publications on the aerodynamic drag C x of spherical particles in flows behind shock waves have appeared during the last decade [9][10][11][12]. It was found that the value of C x under these conditions is significantly (severalfold) higher than in the case of a steady flow, though the global tendency of a slight decrease in C x with increasing Reynolds number Re is the same as in steady events (at least, in the range 10 3 < Re < 10 5 ).…”

Section: Introductionmentioning

confidence: 99%

Drag of nonspherical particles in a flow behind a shock wave

Boiko

Poplavskii

2005

Combust Explos Shock Waves

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The early stage of velocity relaxation of nonspherical particles in a flow behind an incident shock wave is considered by the method of multiframe shadowgraphy. A procedure of processing the data on the motion of a free body for determining its acceleration is proposed; in combination with the diagnostic method used, the procedure forms something like a noncontact aerodynamic balance. Novel data on the drag of bodies of irregular shape in a flow behind a shock wave with Mach numbers of 0.5-1.5 and Reynolds numbers of ≈10 5 typical of dust explosions are obtained. It is found that the values of drag of a nonspherical bluff body and a sphere under these conditions are similar and exceed the drag of a sphere in a steady flow by a factor of 2 to 3.

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“…Nonetheless, Fig. 3b shows that for most of the time the particle Reynolds number may be greater than one suggesting that (equations (7, 9)) are a safer representation for the viscous force than the simple Stokes analysis [34]. Fig.…”

Section: Resultsmentioning

confidence: 99%

“…For particle Reynolds numbers ( Re p )

{Re}_{p} = \frac{ρ ∣ v_{f} (r, t) - v_{p} (r, t) ∣ D}{μ}

greater than one (a typical maximum value of Re p in our experiment is ~30), the radial component of the viscous force F vis_r acting on a completely immersed particle in a uniform liquid velocity field is [34]

F_{v i s_r} = \frac{π}{4} D^{2} ρ C_{d} \frac{1}{2} ∣ v_{f} (r, t) - v_{p} (r, t) ∣ (v_{f} (r, t) - v_{p} (r, t))

where the fluid velocity v f depends on radial position, r , time, t, and the particle velocity, v p is also a function of r and t . Equation (7) does not include unsteady forces acting on the particle.…”

Section: Forces Acting On a Partially Wetted Particle At An Interfacementioning

confidence: 99%

Transport of a partially wetted particle at the liquid/vapor interface under the influence of an externally imposed surfactant generated Marangoni stress

Sharma

Corcoran

Garoff

et al. 2017

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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Marangoni flows offer an interesting and useful means to transport particles at fluid interfaces with potential applications such as dry powder pulmonary drug delivery. In this article, we investigate the transport of partially wetted particles at a liquid/vapor interface under the influence of Marangoni flows driven by gradients in the surface excess concentration of surfactants. We deposit a microliter drop of soluble (sodium dodecyl sulfate aqueous solution) surfactant solution or pure insoluble liquid (oleic acid) surfactant on a water subphase and observe the transport of a pre-deposited particle. Following the previous observation by Wang et al. [1] that a surfactant front rapidly advances ahead of the deposited drop contact line initiates particle motion but then moves beyond the particle, we now characterize the two dominant, time- and position-dependent forces acting on the moving particle: 1) a surface tension force acting on the three-phase contact line around the particle periphery due to the surface tension gradient at the liquid/vapor interface which always accelerates the particle and 2) a viscous force acting on the immersed surface area of the particle which accelerates or decelerates the particle depending on the difference in the velocities of the liquid and particle. We find that the particle velocity evolves over time in two regimes. In the acceleration regime, the net force on the particle acts in the direction of particle motion, and the particle quickly accelerates and reaches a maximum velocity. In the deceleration regime, the net force on the particle reverses and the particle decelerates gradually and stops. We identify the parameters that affect the two forces acting on the particle, including the initial particle position relative to the surfactant drop, particle diameter, particle wettability, subphase thickness, and surfactant solubility. We systematically vary these parameters and probe the spatial and temporal evolution of the two forces acting on the particle as it moves along its trajectory in both regimes. We find that a larger particle always lags behind the smaller particle when placed at an equal initial distance from the drop. Similarly, particles more deeply engulfed in the subphase lag behind those less deeply engulfed. Further, the extent of particle transport is reduced as the subphase thickness decreases, due to the larger velocity gradients in the subphase recirculation flows.

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Acceleration of a sphere behind planar shock waves

Cited by 17 publications

References 6 publications

High spatial and temporal resolution study of shock wave reflection over a coupled convex–concave cylindrical surface

High spatial and temporal resolution study of shock wave reflection over a coupled convex–concave cylindrical surface

Drag of nonspherical particles in a flow behind a shock wave

Transport of a partially wetted particle at the liquid/vapor interface under the influence of an externally imposed surfactant generated Marangoni stress

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