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The axially symmetric, swirl-free gas dynamics and interlinked motion of a cork stopper provoked by the opening of a champagne bottle are modelled rigorously and studied numerically. The experimental study by Liger-Belair et al. (Science Advances, 5(9), 2019) animated the present investigation. Inspection analysis justifies the inviscid treatment of the expanding jet of air enriched with dissolved carbonic acid gas initially pressurised in the bottle. Solving of the resulting Euler equations is facilitated by the open-source software Clawpack. Specific enhancements allow for resolving of the emerging supersonic pockets, associated with surprisingly complex shock structures, as well as the gas-stopper interaction with due accuracy. Our experimental effort provided modelling of the frictional behaviour, constitutive law and reversible (de-)compression of the cork material. Initially, the gas expands inside the bottleneck yet sealed by the stopper, and is hence accelerated by the gas but decelerated by dry sliding friction. Once the stopper has passed the bottle opening, the jet rapidly assumes locally supersonic speed, where a complex shock pattern is detected. Special attention is paid to the formation and dissolution of one or even two Mach discs between the opening and the released stopper. This simulated dynamics is found to be in fairly good agreement with recent experimental findings. It also provides a first insight into the generation of the typical popping sound. [ABSTRACT FROM AUTHOR]

Supercritical CO2 pipelines usually are used to link the CO2 capture system to the geological storage. There are severe hazards once the asphyxiating gas leaks from the long-distance pipeline. The uncertainty of near-field jet characteristics results in imprecise consequences assessment of accidental release of supercritical CO2. To improve the prediction of consequences of accidental release accuracy, the near-field mechanisms of flashing-spray jet was investigated. In this work, an experimental setup with multiple measurement instruments was developed to impose controllable CO2 release from a high-pressure vessel. The flashing-spray jet structures of supercritical CO2 from circular and rectangular orifices were recorded by a high-speed camera. Results indicate that the near-field structures of supercritical CO2 jet from circular and rectangular orifices are totally different, which causes the different dispersion consequences. The jet angle and shock waves were analyzed quantitatively. Lastly, the models of flashing-spray based on the two different phenomena from rectangular and circular orifices were discussed. The combination of macroscopic and microscopic data in the jet can help to understand the complex physics and improve discharge and dispersion model. This work provides a fundamental data to consequences assessment of accidental release of supercritical CO2.

[Display omitted] • A novel two-stage nanoparticle (NP) disperser system was proposed. • The dispersed NP could approach close to the primary diameter in this way. • The aerosols obtained through this method distributed approximately log-normally. • The larger nozzle enlarged the Mach disc and the high shear-stress areas. • The combined effect of NP inertia and fluid shear enhanced the deagglomeration. The size and the agglomeration state of nanoparticles (NPs) play a very important role in nanoparticle applications due to the effect of the dispersion level of NPs on their toxicity, pharmaceutical activity, and catalytic activity. In this study, a novel two-stage nanoparticle disperser system was proposed. We focused on the effects of the aspect ratio (L / D , length (L) and diameter (D)) of the round jet (a straight pipe) on the nanoparticle size distribution (PSD) and we attempted to explain how the jet wakes induced the NP deagglomeration based on the numerical results. The median diameters, mode diameters, and geometric mean diameters (GMD) of the PSDs that were obtained using the second-stage were significantly smaller than those achieved using the first-stage disperser alone. Overall, the GMD, mode diameters, and median diameters could all reach sub-70 nm, which was approaching close to the NP primary diameter (30–40 nm). The particle sizes decreased with the increasing dimensionless nozzle diameter (D * = D / D p × 10−3, D p represents the particle diameter). The increase in L/D for a constant D hardly affected the PSDs but led them to be closer to a standard lognormal distribution. Regarding the NP traveling path and its considerable inertia as it penetrated the Mach disc, these particular field distributions of the jet-wake might explain why the suspended sub-micro NP agglomerates could be highly deagglomerated. Namely, the nano NP agglomerates would suffer the severe shear stress around the Mach disc. [ABSTRACT FROM AUTHOR]

Abstract: Reliable methods are needed to predict ignition boundaries that result from compressed hydrogen bulk storage leaks without complex modeling. To support the development of these methods, a new high-pressure stagnation chamber has been integrated into Sandia National Laboratories’ Turbulent Combustion Laboratory so that relevant compressed gas release scenarios can be replicated. For the present study, a jet with a 10:1 pressure ratio issuing from a small 0.75mm radius nozzle has been examined. Jet exit shock structure was imaged by Schlieren photography, while quantitative Planar Laser Rayleigh Scatter imaging was used to measure instantaneous hydrogen mole fractions downstream of the Mach disk. Measured concentration statistics and ignitable boundary predictions compared favorably to analytic reconstructions of downstream jet dispersion behavior. Model results were produced from subsonic jet dispersion models and by invoking self-similarity jet scaling arguments with length scaling by experimentally measured effective source radii. Similar far field reconstructions that relied on various notional nozzle models to account for complex jet exit shock phenomena failed to satisfactorily predict the experimental findings. These results indicate further notional nozzle refinement is needed to improve the prediction fidelity. Moreover, further investigation is required to understand the effect of different pressure ratios on measured virtual origins used in the jet dispersion model. [Copyright &y& Elsevier]

The present study addresses experimental results to investigate the effect of nozzle inlet configuration on under-expanded swirling jets, which is generated by a convergent nozzle with four tangential inlets at the supply chamber. Several different types of plugs and needles, which can be regarded as a means to measure the nozzle inlet pressure or temperature, are employed to change the nozzle supply chamber. The jet supply pressure at the tangential inlets is varied to obtain the swirling jets ranging from a moderately under-expanded to a strongly under-expanded flow at the exit of nozzle. The under-expanded swirling jet flows are specified by the impact pressure measurements and visualized using the shadowgraph optical method. The results show that the major features of the under-expanded swirling jet are considerably influenced by the detailed configuration of the nozzle inlet chamber. [ABSTRACT FROM AUTHOR]

The near-field structure of an underexpanded sonic dual coaxial jet issuing from the coaxial nozzles of four different geometries is visualized by using a shadowgraph optical method. Experiments are conducted to investigate the effects of the nozzle geometry, such as nozzle-lip thickness, secondary stream thickness, the nozzle pressure ratio, and swirling of the secondary stream on the characteristics of the primary underexpanded jet. The results show that the presence of secondary annular swirling stream causes the Mach disc to move more downstream and increases us diameter, while the diameter of the Mach disc decreases with the decrease in the nozzle-lip thickness. The secondary stream thickness has an influence on the location of an annular shock wave. However, the effect of the secondary stream on the characteristics of the underexpanded coaxial jet is strongly dependent on the pressure ratio of the inner primary jet. [ABSTRACT FROM AUTHOR]

The present study addresses experimental investigations of the near-field flow structures of an underexpanded sonic, dual, coaxial, swirl jet. The swirl stream is discharged from the secondary annular nozzle and the primary inner nozzle provides the underexpanded free jets. The interactions between the secondary swirl and primary underexpanded jets are quantified by a fine pitot impact and static pressure measurements and are visualized using a shadowgraph optical method. The pressure ratios of the secondary swirl and primary underexpanded jets are varied below 7.0. Experiments are conducted to investigate the effects of the secondary swirl stream on the primary underexpanded jets, compared with the secondary stream of no swirl. The results show that the presence of an annular swirl stream causes the Mach disc to move further downstream, with an increased diameter, and remarkably reduces the fluctuations of the impact pressures in the underexpanded sonic dual coaxial jet, compared with the case of the secondary annular stream with no swirl. [ABSTRACT FROM AUTHOR]

The present study addresses an experimental investigation of the near field flow structures of supersonic, dual, coaxial, free, jet, which is discharged from the coaxial annular nozzle. The secondary stream is made from the annular nozzle of a design Mach number of 1.0 and the primary inner stream from a convergent-divergent nozzle. The objective of the present study is to investigate the interactions between the secondary stream and inner supersonic jets. The resulting flow fields are quantified by pitot impact and static pressure measurements and are visualized by using a shadowgraph optical method. The pressure ratios of the primary jet are varied to obtain over-expanded flows and moderately under-expanded flows at the exit of the coaxial nozzle. The pressure ratio of the secondary annular stream is varied between 1.0 and 4.0. The results show that the secondary annular stream significantly changes the Mach disc diameter and location, and the impact pressure distributions. The effects of the secondary annular stream on the primary supersonic jet flow are strongly dependent on whether the primary jet is underexpanded or over-expanded at the exit of the coaxial nozzle. [ABSTRACT FROM AUTHOR]

Experimental results on the shock structure of dual co-axial jets are presented. The effects of the geometric parameters of the inner nozzle, jet static pressure ratio (ratio of the exit plane static pressures of the inner and outer nozzles) and the ratio of outer to inner nozzle throat area on the shock structure were studied. A superimposed outer and inner jet structure was observed in the schlieren photographs. The inner flow is compressed by the outer flow resulting in the formation of a Mach disc and an exit shock. A parameter incorporating the effect of Mach number of the inner nozzle and jet static pressure ratio was found to correlate the observations regarding the Mach disc location. [ABSTRACT FROM AUTHOR]

The paper presents an investigation of micro rocket engine exhaust plume. Primary analysis of supersonic flow and Mach discs appearance is being carried out. Zone of silence is being identified from experimental material and compared with analytical calculations, expansion characteristic is being found. [ABSTRACT FROM AUTHOR]