Satellite Drops Research Articles

Theoretical prediction of the sizes of drops formed in the breakup of capillary jets

The breaking up of a liquid jet subject to small disturbances was studied experimentally and theoretically. A non-linear theory was used to calculate the profile of the waves on the surface of the jet at breakup, and also to predict the volume of the main and satellite drops. It was found that the theoretical and experimental drop volumes were in good agreement. However, satellites were observed in all experiments whereas the theory predicts that satellites should not form for dimensionless wavenumbers greater than 0·7. In the experiments it was not possible to make the jets break up into single main drops of uniform size. The results suggest that it may be possible to produce uniformly sized drops if the main and satellite drops have the same volume.

Droplet production by the disintegration of rotating liquid jets

The linearized equations of motion for an axially rotating jet of liquid, subjected to an axi-symmetric sinusoidal perturbation, have been solved to give the growth rate of the disturbance as a function of the dimensionless wavenumber with the kinematic viscosity, surface tension and rotational frequency appearing in two dimensionless parameters. The results show that the effect of rotation on the instability is to increase the range of unstable wavelengths, to increase the growth rate and to move the point of maximum instability to a shorter wavelength than would occur in a stationary jet of the same viscosity. The theory is tested by measuring the growth rates of controlled disturbances on the surface of axially rotating jets of viscous liquid. It is found that the predicted growth rates are in reasonable agreement except at large wavenumbers. The sizes of the main and satellite drops formed by jet breakup were also measured. The rotation, by increasing the growth rates, markedly reduces the length to breakup. However the centrifugal pressure gradient causes an increase in the rate of growth of the wave crests, resulting in smaller main drops and larger satellite drops than with the non-rotating jet. The sizes of the main and satellite drops have been correlated by simple expressions, being dependent simply on the dimensionless wavenumber.

Molten drop formation from metal wires

A study of the detachment of a drop from a metal wire by induction melting of the tip has been made using a Fastax high speed cine camera. The process occurs by progressive elongation of the drop until a `waist' is formed which finally draws down until detachment occurs, the `waist' forming a satellite drop. Drop oscillation to form a spherical shape occurs immediately after detachment. Observations on a satellite drop during fall in an oxidizing medium are reported.

On the Generation of Uniform Drops with Rotating Nozzles

As we found that the dripping of liquid from the end of a tube with small diameter accompanied no satellite drop, we tried to produce a plenty of uniform drops by means of rotating nozzles, checking the results with theoretical considerations. The chief results obtained are as follows : (1) If the coefficient of the outer diameter CD2, defined by [numerical formula] (D2=the outer diameter of the tube, σ=the surface tension and γ=the specific weight of the liquid), is less than 0.4, uniform drops can be produced. (2) When the flow rate q is small, the diameter of drop attains the maximum value dmax which is given by the simultaneous equations [numerical formula] where R1=the radius from the center to the tip of rotating nozzle, n rpm=the rotational speed and Cw=the coefficient of the drop weight. The functional form of f in (2) is given in the previous paper(1). (3) The diameter of drop decreases with the flow rate from dmax to its minimum value dmin, until the critical rauge is reached, where the mode of flow changes from the dripping to the smooth laminar flow. The value of dmin can be determined from equations (1)∼(3), if we only substitute the value of internal diameter D1 of the tube to the outer diameter D2. (1) Tech.Reb.Tohoku Univ.19, 2 (1955), 135.

The Production of Sprays and Mists of Uniform Drop Size by Means of Spinning Disc Type Sprayers

Spray of almost uniform drop size is formed when liquid is fed under suitable conditions on to the centre of a rotating disc and centrifuged off the edge. This method of spraying has been studied over a wide range of variables and homogeneous clouds have been produced in the drop-size range from 3 mm. to 15 μ diameter. The size of the spray drops is given approximately by the equation d=3.8 (T/Dρ)½/ω where d=drop diameter, D=disc diameter, ω=angular velocity of disc, T=surface tension of liquid, ρ=density of liquid. The spray thus formed also contains a proportion of fine satellite drops, but their smaller distance of projection from the disc enables them to be removed from the cloud when their presence is undesirable. Relatively coarse sprays are easily produced by means of a simple electric motor-driven disc. The finer spray sizes require rotor speeds up to several thousands of revolutions per second and high speed air driven "tops" have been used for this purpose. Suitable designs of apparatus are described.