Droplet generation during liquid jet impingement onto a horizontal plate

Zhan, Yongzhong; Oya, Naoki; Enoki, Koji; Okawa, Tomio; Aoyagi, Mitsuhiro; Takata, Takashi

doi:10.1016/j.expthermflusci.2018.05.022

Cited by 19 publications

(9 citation statements)

References 8 publications

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“…Herein, C 1 = 9.1×10 -4 C D / D p for water jet, with C D being the dimensionless drag coefficient. Zhan et al [44] experimentally had C D = 0.58 for Re 0 from 2,000 to 10,000. U b represents the jet velocity where jet breakup occurs and can be calculated by substituting l = L b into Eq.…”

Section: Resultsmentioning

confidence: 97%

“…After the jet breakup when l > L b , the air friction acting on the primary drops cannot be neglected due to the much larger surface area of the drops [31] . Zhan et al [44] developed an equation for predicting the velocity U p of the primary drops

…”

Section: Resultsmentioning

confidence: 99%

“…Compared with the (minimum) breakup length L b , the maximum breakup length L max represents the point where the jet is consistently observed to break into the primary drops. In this consideration, Zhan et al [44] established a correlation for the dimensionless impact frequency f / f max with the dimensionless falling height ( l - L b )/( L max - L b ) as

…”

Section: Resultsmentioning

confidence: 99%

“…As the splashing droplets are small and fast-moving, the determination of their amount, size and velocity is challenging, and no comparison has been made for these splashing characteristics during continuous jet and primary drop impingement. For the impingement of primary drop trains, Zhan et al (2018 and 2021) correlated the amount of splashing droplets with the impact Weber number and impact frequency of the primary drops. They also reported that the size distribution of the splashing droplets obeys the log-normal law with the maximum value reaching approximately 25% of the impact drop diameter.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Splashing generation by water jet impinging on a horizontal plate

Qian

Zhu

2022

Experimental Thermal and Fluid Science

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The report of COVID-19 virus in municipal wastewater raises the question of whether viruses can become airborne during wastewater transport in sewer systems. The present work experimentally investigates a water jet impinging vertically onto a horizontal plate and the behaviours of the generated tiny droplets. Depending on whether the jet breaks into primary drops before the impingement, three regimes can be defined: non-splashing, jet-splashing and drop-splashing regimes. The splashing ratio, i.e., the portion of jet flow rate becoming splashing droplets, ranges from 1% – 70% in the drop-splashing regime, while it remains less than 2% in the jet-splashing regime. For the splashing droplets, their size and velocity distributions follow log-normal laws. Their diameters are mainly in the range from 0 to 0.3 of the impact jet or drop diameter with the median less than 0.1. Their velocities mostly range from 0 to 3.0 times of the impact velocity with the median around 1.0. The medians of both the dimensionless diameter and velocity of splashing droplets decrease with the impact Weber number. The ejection angles of splashing droplets obey a bell-shaped distribution with the maximum around 70° and the median ranging from 16° to 30°.

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Section: Resultsmentioning

confidence: 97%

…”

Section: Resultsmentioning

confidence: 99%

…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Splashing generation by water jet impinging on a horizontal plate

Qian

Zhu

2022

Experimental Thermal and Fluid Science

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“…Based on the velocity measurement of the splattered droplets, it has been assumed that the splattering takes place downstream the radial position (also known as the radius of splattering) r s = 5.71 d N [6], where d N denotes the nozzle diameter. Splattering is often quantified by the splattered mass fraction ξ, which is the ratio between the mass flow rates of the splattered liquid and impinging liquid [7][8][9][10][11][12]. Correlations describing the splattered mass fraction can be found in [9] for coherent jets (L/d N < 50) and pipe nozzles, as well as in [11] for disintegrated jets (L/d N ≥ 250).…”

Section: Introductionmentioning

confidence: 99%

Heat transfer during pulsating liquid jet impingement onto a vertical wall

2020

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Liquid jet impingement is used for cooling and cleaning in various industrial branches. The advantages of jet impingement include high heat and mass transport rates in the vicinity of the impingement point. Pulsating liquid jets impinging on horizontal substrates with a pulsation frequency around 100 Hz have been shown to increase the cooling efficiency in comparison to jets with continuous mass flow rates. The influence of jet pulsation on cooling efficiency for impingement of horizontal jets onto vertical walls has not yet been investigated. In the case of a vertical heated wall, gravity contributes to the liquid flow pattern. In particular, if the time span between two pulses is sufficiently long, the liquid drainage from the region above the impingement point can contribute to heat transport without increasing the average flow rate of the cooling medium. In this work, the influence of pulsations on heat transfer during impingement of a horizontal liquid jet onto a vertical wall is investigated experimentally for the pulsation frequency range 1–5 Hz. The results regarding increase of heat transfer efficiency are related to flow patterns developing by impingement of successive pulses, as well as to the liquid splattering.

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Size and velocity correlation for splashing droplets generated by jet impingement

Zeng,

Zhu,

Qian

et al. 2024

Exp Fluids

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Municipal drainage systems can transmit harmful microorganisms such as COVID-19 virus through wastewater as well as drain air ow with suspended tiny bio-droplets. The generation of tiny droplets in drainage systems can be simpli ed as the phenomenon of jet impingement and splashing, which is also common in industries, but the size and velocity correlation and the kinetic energy of splashing droplets remain unclear. This paper uses high-speed photography to study splashing from a jet impinging on a horizontal plate. Since the jet can break into successive drops before impingement, successive drops impingement and continuous jet impingement are de ned and their splashing modes are revealed. Successive drops impingement and continuous jet impingement respectively produce splashing droplets with sizes smaller than 0.25 and 0.3 times the size of the impact drops and jet, and with the velocities up to 3.0 and 1.5 times the impact velocity. Correlations between size and velocity of splashing droplets are established: the range and maximum of velocity increase as diameter decreases, and the high velocity splashing droplets have ejection angles within 10° to 20°. For successive drops impingement, the percentage of total kinetic energy of splashing droplets relative to impact kinetic energy increases with impact Weber number and can reach nearly 50%, however, it varies little with impact Weber number for continuous jet impingement, reaching only 10%. Successive drops impingement produces more splashing droplets characterized by a combination of smaller size, higher velocity and larger ejection angle, resulting in a greater risk of producing airborne microorganisms.

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Droplet generation during liquid jet impingement onto a horizontal plate

Cited by 19 publications

References 8 publications

Splashing generation by water jet impinging on a horizontal plate

Splashing generation by water jet impinging on a horizontal plate

Heat transfer during pulsating liquid jet impingement onto a vertical wall

Size and velocity correlation for splashing droplets generated by jet impingement

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