Single Liquid Jet Research Articles

Numerical simulation of single/double liquid jets in supersonic crossflows

This study investigates the mixing processes of liquid jets in supersonic crossflows at a Mach number of 2.1 by using numerical simulations that employ the Coupled Level-Set/Volume-of-Fluid (CLSVOF) method, which is based on the Delayed Detached Eddy Simulation (DDES). The instantaneous spray morphology from the simulations agreed well with the experimental data. The spray presents the ‘Ω’ shape when viewed from the front, and the maximum error in the penetration depth was 15% from a side perspective. The direction of the air movement determined the shape of the liquid column shearing and breaking. In turn, the breaking process of the liquid jet significantly affects the structure of the air flow. Three-dimensional flow around the liquid column occurred when the supersonic incoming flow impinged on the liquid column, ultimately forming counter-rotating vortex pairs (CVP) in the inner region of the spray. Evolution of the reverse vortex pair accelerated the mixing process of the spray. Single liquid jet was used as a basis to further study double jets in Mach 2.1 airflow. The results show that the breaking length and penetration depth of the downstream jet are significantly improved.

Compound jet generated from an impacted concave dual-layer liquid surface

By impacting a concave dual-layer liquid (with the oil and the dyed water) surface in a test tube, a compound jet with a water core and an oil shell is generated. The velocities of the jet’s head (Vj) and the oil-water interface ( $${V'_j}$$ ) are experimentally determined against the initial thickness and the viscosity of the upper layer liquid. The results show that the oil-water interface can be roughly regarded as a pure material surface, whose velocity can be determined from the jet velocity and the initial location (or the film thickness). Furthermore, the effective density, viscosity and surface tension of the compound jet are used to evaluate the jetting velocity. The previous scaling relation for a single liquid jet can be used to give a good prediction with the effective quantities. The results of this paper can be used for the compound jet/droplet preparation.

A review on multiple liquid jet impingement onto flat plate

Multiple jet impingement has been an important industrial application for a long time. Processes like quenching of hot steel surfaces in steel industry utilize the high heat-carrying capacity of liquid multiple impinging jets in order to achieve the uniform temperature of the metallic surface. The objective of this paper is to summarise the state of the art of the process of multiple jet impingement onto flat plate and highlight the future scope of research space in this field. This study focuses on the arrays of impinging liquid jets and to summarize relevant experimental and numerical results on multiple liquid jet impingement heat transfer and hydrodynamic behavior together with the latest developments published in the literature. The present work is limited to the normal impingement of multiple liquid jets on flat surfaces and the physics behind the single and multiple liquid jet configurations are discussed in the paper followed by the experimental studies. The effect of various paprameters like the jet diameter, jet velocity, velocity-profile, jet to target distances, jet to jet distances, and surface boundary conditions. The numerical studies discuss the studies conducted on multiple jet impingement and compare the accuracy of the different numerical methods utilized in the studies. The extrapolation of the results obtained from single liquid jet impingement have been discussed to suggest efficient methodologies for multiple jet impingement studies. It has been found that the study of hydrodynamic characteristics of multiple jet impingement is an important aspect that affects the heat transfer rate due to the jet impingement and needs to be explored further to find a better correlation between heat transfer rate and different hydrodynamic parameters of the flow.

Experimental study on spray break-up and atomization processes from GDI injector using high injection pressure up to 30 MPa

This paper focuses on the influence of injection pressures up to 30MPa on single liquid jet break-up and atomization processes. For this purpose, a single jet from a multi-hole GDI injector has been characterized performing visualization and PDPA (phase Doppler particle analyzer) experiments. Using a thin sheet of light generated by a Nd:Yag laser and capturing a sequence of jet development images with a CCD camera, the internal structure was visualized. In order to quantify the droplet diameter and velocity, a 2-D PDPA system were carried out in addition to the spray visualization. Analyzing the images of the internal structure of jet and the result of PDPA, including droplet diameter and velocity distribution with increasing injection pressure up to 30MPa, the elevated injection pressure on a jet break-up and atomization was characterized.Our experimental results show the existence of a leading edge of the jet observed at the initial stage of injection. This phenomenon revealed relatively large droplets ahead of the main jet then disappeared quickly as lose the droplets momentum. Furthermore, for all injection pressures, unique ‘branch-like structure’ was observed when the jet was fully developed. This structure had many counter rotating branches related to the effect of air-entrainment and rapidly broken down into droplet clusters and droplets. Especially, as increased injection pressure, the time to exhibit the structure and distance between two branches were decreased. In addition, based on the results of droplet diameter and velocity distribution at various injection pressures, we confirmed that the injection pressure plays a key role in droplet break-up, but a limit in injection pressure to enhance droplet break-up also occurred. That is, increasing injection pressure from 5 to 10 to 20MPa led to a decrease in SMD (Sauter mean diameter) linearly by approximately 10μm. However, an injection pressure above 20MPa, did not result in any significant reduction in SMD.

Triphasic Nanocolloids

Triphasic nanocolloids, that is, nanocolloids with three distinct compartments, were successfully produced by use of electrified co-jetting. Simultaneous manipulation of the three parallel liquid with laminar flows yielded a liquid droplet with three interfaces between the jetting liquids. Under a high electric potential, a single liquid jet was produced from the triple point of the droplet. Separation between the phases was maintained throughout the jetting process and resulted in triphasic nanocolloids. Poly(ethylene oxide), poly(acrylic acid), and poly(acrylamide-co-acrylic acid) solutions were used and verified to be compatible with the process. Fluorescent-labeled biomolecules were selectively incorporated in each phase of the nanocolloids, and confocal laser scanning microscopy was employed for the characterization. Scanning electron microscopy results verified that the sizes of the colloids are in the range of nanocolloids. This simple and versatile technique to fabricate multicompartment nanocolloids is expected to have great impact on drug delivery, molecular imaging, and smart displays.

Liquid jets, accelerated thrombolysis: a study for revascularization of cerebral embolism

A prior study has reported that a rapid recanalization therapy of cerebral embolism, using liquid jet impacts generated by the interaction of gas bubbles with shock waves, can potentially penetrate through thrombi in as little as a few μs with very efficient ablation (Kodama et al. 1997). The present study was undertaken to examine the liquid jet impact effect on fibrinolysis in a tube model of an internal carotid artery. First, the conditions for generating the maximum penetration depth of liquid jets in the tube were investigated. Gelatin was used to mimic thrombi. The shock wave was generated by detonating a silver azide pellet weighing about a few μg located in a balloon catheter. The collapse of the inserted gas bubbles and the subsequent liquid jet formation were recorded with high-speed photography. Second, thrombi were formed using fresh human blood from healthy volunteers. The fibrinolysis induced by the liquid jet impact with urokinase was explored. This was conducted under selected conditions based on the experiment using the gelatin. Fibrinolysis was calculated as the percentage of the weight loss of the thrombus. Fibrinolysis with urokinase alone and with a single liquid jet impact with urokinase was 1.9 ± 3.7% (n = 16) and 20.0 ± 9.0% (n = 35), respectively, for an incubation time of 60 min. Statistical differences were obtained between all groups (ANOVA). These results suggest that liquid jet impact thrombolysis has the potential to be a rapid and effective therapeutic modality in recanalization therapy for patients with cerebral embolism and other clinical conditions of intra-arterial thrombosis.

Liquid Jet Impingement Cooling of a Rotating Disk

Results are presented from an experimental study conducted to determine the average convective heat transfer coefficient for the side of a rotating disk, with an approximately uniform surface temperature, cooled by a single liquid jet of oil impinging normal to the surface. Tests were conducted over a range of jet flow rates, jet temperatures, jet radial positions, and disk angular velocities with various combinations of three jet nozzle and disk diameters. Correlations are presented that relate the average Nusselt number to rotational Reynolds number, jet Reynolds number, jet Prandtl number, and dimensionless jet radial position.

Breakup of liquid jets by transverse shocks

Multiple shock waves impinging on a single liquid jet and on two parallel jets in a direction perpendicular to their flow axes