基于二元液滴碰撞模型的喷雾计算研究

Study on Spray Simulation Based on Binary-droplet Collision Model

两股互射喷雾内存在大量液滴碰撞现象。通过建立二元液滴碰撞模型模拟喷雾形状,以弥补广泛采用的O’Rourke模型的不足。本文建立了喷雾中二元液滴碰撞出现聚合、反弹、拉伸分离和反溅分离等机制的判别标准,推导了每种机制下碰撞后新生成液滴的数目、大小和速度的计算公式,并应用本文建立的二元液滴碰撞新型模型模拟了两股互射喷雾形状,并与实验数据进行了比较。模拟结果发现:新模型得到的喷雾总体形态与实验数据符合;O’Rourke模型得到的结果不能正确反映喷雾碰撞区域形状,而新模型得到的喷雾碰撞区域形状与实验数据一致;新模型得出的喷雾区域外几乎无液滴产生,这与实验图形相符,而O’Rourke模型会得到处于喷雾区域外的液滴。结果表明:与O’Rourke模型相比,二元液滴碰撞新型模型可正确模拟喷雾形态。这为更加真实地模拟喷雾形状,进而为定量研究喷雾特征提供了较为可靠的液滴碰撞模型。

The collision phenomenon of numerous droplets exists in two mutualimpingement sprays. A binary-droplet collision model was established to simulate the shape of sprays, in order to make up the widely used O＇Rourke model. The criteria relations were founded to distinguish the regimes of coalescence, bounce, stretching separation and reflexive separation of binary-droplet collision occurring in sprays. The calculation equations were derived to obtain the number, size and velocity of newly generated droplets after collision under each regime. This new binary-droplet collision model established in this paper was used to simulate the shape of two mutual-impingement sprays and compared with experimental data. The simulation outcomes show that the general shape of sprays simulated by the new model is in agreement with experimental data. The shape of spray collision zone can not be reflected by O＇Rourke correctly. Instead, this zone obtained by new model is in accord with experimental data. Furthermore, nearly none of droplets are generated in the outside of sprays by new model, which is as same as that in experimental photograph. However, some droplets are obtained in this outside zone O＇ Rourke model, the new sprays correctly. This new by O＇Rourke model. The result shows that comparing with binary-droplet collision model can simulate the shape of model is able to simulate the spray shapes more reality, which supplies a reliable droplet collision model to study the characteristics of sprays in a quantitative way.