Mechanical breakup mode

The mechanical breakup mode occurs around the rims of the sheet where the air-liquid relative velocity is low, forming relatively large droplets. At low relative velocities, aerodynamic forces are much smaller than surface tension and inertia forces. Thus, the breakup of the liquid rims is purely mechanical and follows the Rayleigh mechanism for liquid column/jet breakup. For the same air pressure, the droplets detached from the rims become smaller as the liquid flow rate is increased. 

From a liquid film such as a water film, the diameter of a drop formed under the action of gravity is calculated to be 9 mm with the above equation. Similarly to the liquid dripping mode, the liquid film breakup mode governed by the dripping mechanism is also typified by large droplets and low liquid flow rates. 

B) Flat Liquid Sheets into Air Streams Mechanical and Aerodynamic Disintegration. In air streams (with an air flow), a liquid sheet issuing from the 2-D nozzle will form a quasi-2-D expanding spray. The breakup modes are divided into two groups (1) mechanical mode due to the action of liquid injection pressure, and (2) aerodynamic mode due to the action of air friction. 

Abstract This chapter deals with capillary instability of straight free liquid jets moving in air. It begins with linear stability theory for small perturbations of Newtonian liquid jets and discusses the unstable modes, characteristic growth rates, temporal and spatial instabilities and their underlying physical mechanisms. The linear theory also provides an estimate of the main droplet size emerging from capillary breakup. Formation of satellite modes is treated in the framework of either asymptotic methods or direct numerical simulations. Then, such additional effects like thermocapiUarity, or swirl are taken into account. In addition, quasi-one-dimensional approach for description of capillary breakup is introduced and illustrated in detail for Newtonian and rheologically complex liquid jets (pseudoplastic, dilatant, and viscoelastic polymeric liquids). 

The paucity of non-Newtonian secondary breakup studies means there is not enough data to provide a clear consensus as to either common characteristics (modes) or processes (mechanisms). As a result, the morphology of non-Newtonian liquid drops undergoing secondary breakup is still uncertain. 

For K > 2 the drops deform into stable filaments, which only upon reduction of k disintegrate by the capillarity forces into mini-droplets. The deformation and breakup processes require time - in shear flows the reduced time to break is tb > 100- When values of the capillarity number and the reduced time are within the region of drop breakup, the mechanism of breakup depends on the viscosity ratio, A, - in shear flow, when X > 3.8, the drops may deform, but they cannot break. Dispersing in extensional flow field is not subjected to this limitation. Furthermore, for this deformation mode Kcr (being proportional to drop diameter) is significantly smaller than that in shear (Grace 1982). 

It is believed that gravitational radiation from the r-modes in nascent neutron stars is the mechanism by which newborn neutron stars, which could be rotating at near their breakup speed ( 1 kHz), lose most of their angular momentum. The result is the slowly spinning neutron stars that are observed. R-modes could produce nearly monochromatic gravitational radiation with a characteristic strain as large as /tchar 10 at frequencies of kHz and distances of 10 Mpc, lasting for several tens of seconds. 

Drop deformation and breakup plays a decisive role in the evolution of polymer blend morphology. The breakup mechanism during polymer blending is very complex and is influenced by many variables, such as shear stress, viscosity ratio, stress ratio, Deborah numbo-and first normal force difference [1-3]. Visualization was used to get realtime information during the drop deformation and breakup process [1-5]. It is shown that drops can break up in simple shear flow via different modes such as breakup in the flow axis, erosion, parallel breakup, tip streaming and breakup along the vorticity axis [1-7]. 

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