  The multifractal nature of drop breakup in air-blast nozzle atomization
process has been studied. We apply the multiplier method to extract the
negative and the positive parts of the f(alpha) curve with the data of drop
size distribution measured using Dual PDA. 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(alpha) 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. On
other words, the spatial concentration distribution of the disperse phase in
the spray zone fluctuates momentarily showing intrinsic randomness.
