The multifractal nature of drop breakup in the air-blast nozzle atomization process has been studied. We apply the multiplier method to extract the negative and the positive parts of the $f\left(\alpha \right)$ curve with the data of drop-size distribution measured using dual particle dynamic analyzer. A random multifractal model with the multiplier triangularly distributed is proposed to characterize the breakup of drops. The agreement of the left part of the multifractal spectra between the experimental result and the model is remarkable. The cause of the distinction of the right part of the $f\left(\alpha \right)$ curve is argued. The fact that negative dimensions arise in the current system means that the spatial distribution of the drops yielded by the high-speed jet fluctuates from sample to sample. In other words, the spatial concentration distribution of the disperse phase in the spray zone fluctuates momentarily, showing intrinsic randomness.

• Received 1 June 2000

DOI:https://doi.org/10.1103/PhysRevE.63.016302