Dynamic behavior of liquid sheets

An experiment was conducted to study the aerodynamic instability of liquid sheets issuing from a two-dimensional air-assisted nozzle. Detailed measurements of the frequency of oscillation of the liquid sheet have been made. The measured vibrational frequencies were then correlated with the resulting spray angle. It was shown that the liquid sheet oscillations are dynamically similar to that of hard spring systems. For each air pressure, three distinct modes of breakup are distinguished. At low liquid flow rates, both the sinusoidal and the dilational modes are superimposed on the liquid sheet. With a further increase in liquid flow rate, the liquid sheet oscillations mainly become of the dilational type. It was also shown that the effect of introducing air in the nozzle is similar to the effect of inducing forced vibrations on the nozzle jaws. Thus, for each air flow rate, there is a specific vibration frequency for the nozzle. The frequency of these vibrations is proportional to the air velocity. As the liquid sheet natural frequency approaches that of the nozzle, resonance is established. At resonance, the maximum spray angle is achieved.