Analysing the Motions of Spray Droplets on a Cow’s Surface to Relieve Heat Stress

Exploring the behaviour of sprayed water droplets on dairy cow hair during the spraying process is of great significance to improve the effects of this process on cooling a dairy cow’s body. In this paper, we use a high-speed camera to examine the sprayed droplets of different diameters and then analyse the experimental results. The results show that the movements of sprayed droplets on the simulated dairy cow (SDC) surface can be divided into four categories: random scattering, aggregation, multiple deformations and flow slipping. Sprayed droplets with diameters of 0.56 mm and 0.8 mm exhibit more frequent random scattering than do other droplets. However, this behaviour is unfavourable for cooling the dairy cow body. By analysing the dimensionless parameter B, we find that sprayed droplets with a diameter of 1.1 mm, which have a higher frequency of aggregation, is not conducive for cooling the dairy cow body. However, multiple deformations can contribute to the cooling process of a SDC. By analysing the relationship between We and γ, we can find the range of We and γ in which the behaviour of random scattering and multiple deformations may appear more frequently. The results show that sprayed droplets with diameters of 0.8 mm–1.0 mm exhibit multiple deformations more frequently, which is beneficial for the cooling process of a SDC.