Abstract: When a high-speed water jet impacts the surface of downstream water, a large number of moving water droplets are generated in the downstream space. How to determine the size distribution of these water droplets has become an important scientific issue. In meteorology, various types of rainfall droplet spectra are often fitted using the Gamma distribution. Such a distribution is also frequently adopted in the modeling of droplet sizes in flood discharge atomization. However, this method lacks physical significance and its computational accuracy is limited. To overcome the shortcomings, this paper develops a joint information entropy distribution model of water droplets in a non-equilibrium open system based on the maximum entropy increase method, and formulates an error function method to solve the model parameters. The results show that in calculation of the droplet size probability density in jet flow discharge, this model has the best agreement with experimental data, compared with the Gamma distribution method or the traditional maximum entropy distributions. Under different operating conditions, the determination coefficient of its calculations is 3.5% and 25.3% higher than the other two methods respectively, and the root mean square error is 72.4% and 79.0% lower respectively; Under different operating conditions, there exists an equal proportional relationship between the average droplet diameters. This shows our new method would lay a theoretical basis for predicting the particle size distribution of flood discharge atomization.

Key words: flood discharge atomization, drop spectrum, macroscopic information entropy, microscopic information entropy, maximum entropy increase