Splash wave and crown breakup after disc impact on a liquid surface

In this paper we analyze the impact of a circular disc on a free surface using experiments, potential flow numerical simulations and theory. We focus our attention both on the study of the generation and possible breakup of the splash wave created after the impact and on the calculation of the force on the disc. We have experimentally found that drops are only ejected from the rim located at the top part of the splash --giving rise to what is known as the crown splash-- if the impact Weber number exceeds a threshold value \Weber_{crit}\simeq 140. We explain this threshold by defining a local Bond number $Bo_{tip}$ based on the rim deceleration and its radius of curvature, with which we show using both numerical simulations and experiments that a crown splash only occurs when $Bo_{tip}\gtrsim 1$, revealing that the rim disrupts due to a Rayleigh-Taylor instability. Neglecting the effect of air, we show that the flow in the region close to the disc edge possesses a Weber-number-dependent self-similar structure for every Weber number. From this we demonstrate that \Bond_{tip}\propto\Weber, explaining both why the transition to crown splash can be characterized in terms of the impact Weber number and why this transition occurs for $We_{crit}\simeq 140$. Next, including the effect of air, we have developed a theory which predicts the time-varying thickness of the very thin air cushion that is entrapped between the impacting solid and the liquid. Our analysis reveals that gas critically affect the velocity of propagation of the splash wave as well as the time-varying force on the disc, $F_D$. The existence of the air layer also limits the range of times in which the self-similar solution is valid and, accordingly, the maximum deceleration experienced by the liquid rim, what sets the length scale of the splash drops ejected when We>\Weber_{crit}

Exploring droplet impact near a millimetre-sized hole: comparing a closed pit with an open-ended pore

We investigate drop impact dynamics near both closed pits and open- ended pores experimentally. The resulting impact phenomena differ greatly for a pit or a pore. For the first, we observe three phenomena: a splash, a jet and an air bubble, whose appearance depends on the distance between impact location and pit. Furthermore, we found that splash velocities can reach up to seven times the impact velocity. Drop impact near a pore, however, results solely in splashing. Surprisingly, two distinct and disconnected splashing regimes occur, with a region of plain spreading in-between. For pores, splashes are less pronounced than in the pit case. We state that, for the pit case, the presence of air inside the pit plays a crucial role: it promotes splashing and allows for air bubbles to appear.Comment: 17 pages, 11 figures, 1 supplementary movie, submitted to JF

Air Pollution In India – Causes, Effects And Solutions

Air is the necessary for the very existence of human beings, animals and plants that appeared on the earth. However, due to the rapid growth of population and technology the air was polluted day by day. In 2011, India’s Central Pollution Control Board had presented the report according to which 180 cities in India had particulate matter six times more than the permissible limit set by the World Health Organization in the air. Vehicles, biomass burning, fuel tarnishing are few of the major causes of air pollution in India. The problem of air pollution is so big that we cannot manage to pay for overlook it. As such it has to be handled with a high degree of care. This paper focuses on causes, effects of air pollutions in India and steps to solve the problems and policy measures to ensure reduce air pollution to the entire resident of earth. This study mainly descriptive in nature and secondary data are used for the purpose of the study. The data was collected from books, various articles, journals and websites

Temperature dependence of pure quadrupole resonance of 35Cl in α-CH2ClCOOH

Measurements of the pure quadrupole resonance frequency of 35Cl in CH2ClCOOH have been made over a wide range of temperature (77K to 300K). Two resonance lines due to chemically inequivalent sites have been observed throughout the above temperature range

Technoeconomic assessment of marine fish production, marketing and capacity utilization of processing plants in Gujarat

Among the major maritime states of India, Gujarat has the longest coastline (1,600 km) and the largest continental shelf area (1,65,00 sq.km). The current annual catch of marine fish in this state is 6,45,261 tonnes (1994-'95). landed in about 221 coastal fish landing centres by 21,018 fishing units, manned by about 0.75 lakh fishermen