Droplet Formation in Atomization of Normal Liquids

Atomization of normal liquids has a wide range of applications, as discussed previously. In many applications, the fundamental phenomena and principles during atomization are common or similar. According to the geometry feature of bulk liquids, droplet formation may be loosely classified into the following primary idealized modes  

For a liquid (for example, water), the size of a drop formed at a sharp-edged tube opening can be reduced from 3.6 mm to 784 pm if the opening diameter decreases from 1 mm to 10 pm. Apparently, the dripping mechanism is concerned with large drops and low liquid flow rates. Therefore, it is a functional mechanism in drop formation processes common in nature. 

Various equilibrium forms of suspended drops can be obtained for different values of the radius of curvature at the drop tip and for different values of surface tension and gravitational forces, as calculated by Tanasawa and Toyoda.[41] These researchers also 

Recently, the size and shape of a liquid droplet at the molten tip of an arc electrode have been studied,12151 and an iterative method for the shape of static drops has been proposed. 216 Shapes, stabilities and oscillations of pendant droplets in an electric field have also been addressed in some investigations. 217 218 The pendant drop process has found applications in determining surface tensions of molten substances. 152 However, the liquid dripping process is not an effective means for those practical applications that necessitate high liquid flow rates and fine droplets (typically 1-300 pm). For such fine droplets, gravitational forces become negligible in the droplet formation mechanism. 

Another notable example of the dripping mechanism is the slow formation of a drop by breakaway from a liquid film on the bottom surface of a flat, horizontal plate under the action of gravity. The size of the drop formed can be estimated using the following expression derived on the basis of a force balance between gravity and surface tension)1  

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