Oil spills in the ocean resulting from accidents can cause significant water pollution across large areas. When a dispersed oil film on the water surface comes into contact with an ignition source, it may ignite and lead to a severe marine fire. Currently, research on the microscopic mechanisms through which oil properties and substrate environments influence the dynamic diffusion behavior of oil is relatively limited.

In this study, a multiphase flow model was developed using the ANSYS FLUENT software to investigate the dynamic evolution and diffusion mechanisms of oil on the substrate under various influencing factors. Using numerical simulation, diffusion kinetics of oil films on substrates with different properties were studied under various environmental conditions, focusing mainly on three variables: (1) substrate salinity (deionized water, 20 g/kg, 30 g/kg, and 40 g/kg), (2) water content of the oil (crude oil, 20%, 40%, and 60%), and (3) substrate temperature (20 ℃, 30 ℃, and 40 ℃). This study mainly emphasizes the effects and regulatory roles of these three influencing factors on the dynamic diffusion behavior of oil films.

The results indicate a direct correlation between the salinity of the substrate and the diffusion rate of the oil film. Increased salinity elevates the density and surface tension of the substrate, promoting the diffusion of the oil film. The water content of oil affects its physical properties, such as density, viscosity, and surface tension. Higher water content leads to higher viscosity, which inhibits the diffusive movement of the oil on the substrate and ultimately reduces the diameter of the diffused oil film. Analysis of the oil film diffusion rate contour map revealed that during the initial diffusion stage, gravity acts as the primary driving force, causing rapid diffusion in a radial direction. Over time, surface tension dominates and slows down the diffusion process at the oil film edges. With an increase in substrate temperature, the viscosity and surface tension of the oil decrease, thus promoting the diffusion of the oil film. The ratio of the diameter to the thickness of the oil film also affects the diffusion trend. At higher temperatures, this ratio varies significantly, indicating vigorous movement of the oil film in the initial stages. Formulas for predicting the diameter of the diffused oil film under varying conditions of salinity, water content, and temperature were derived based on power-law functions and showed good agreement with simulation results.

Oil spills in marine environments spread at a faster rate with an increase in salinity. The water content in oil films also affects the diffusion rate: oil films with high water content spread at a slower rate compared with those with low water content. Furthermore, water temperature has a significant effect on oil spilling; high water temperature makes the diffusion behavior of the oil film more intense. Numerical simulation characterizes the dynamic diffusion features of oil under diverse environmental conditions, laying a theoretical foundation for the prediction of slick diffusion of oil during spill incidents.

The phenomenon of a droplet impacting a heated surface is widely used in a number of important fields, such as spray cooling, desalination, agricultural irrigation, and fire-fighting. However, the phenomenon of a droplet impacting a heated surface is very complex and involves the combined knowledge of several disciplines, such as engineering thermodynamics, heat transfer, and fluid mechanics. In addition, the phenomenon of a droplet impacting a heated surface is affected by a variety of factors, such as surface characteristics, droplet properties, and environmental conditions. Therefore, studying the impact pattern and dynamic characteristics of a droplet on a heated surface is of great importance.

To strengthen the understanding and mastery of students on the phenomenon of a droplet impacting a heated surface, an innovative teaching model combining experimental operations and course design is proposed. First, an experimental platform for the droplet impacting on the heated surface is constructed by arranging and adjusting the following: a high-speed camera, an automatic injection system, an intelligent constant temperature heating platform, a digital recorder, a computer, and light-emitting diode background light. Subsequently, deionized water is selected as the experimental droplet, and a 310S stainless steel plate is used as the experimental surface. Furthermore, by adjusting the experimental conditions, such as the droplet falling height and the surface temperature, the experiments of the droplet impacting on the surface are sequentially completed, and the dynamic process and real-time data of the droplet impact on the surface are recorded. Finally, an in-depth discussion about the application of integrating laboratory operations with course design in teaching practice is conducted.

The pattern phase map of the droplet impact on the surface is plotted in detail for the experimental conditions. The pattern of a droplet impacting a surface depends on the surface temperature and the dimensionless Weber number. The impact patterns are classified into four types at different heights and surface temperatures, which are adhesion, rebound, rebound-breakup, and breakup patterns. The dynamic parameters of the droplet were intensively investigated with different heights and temperatures. When the surface temperature is constant, the spreading diameter of the droplet considerably increases with the increase in the impact height. When the impact height is constant, the spreading diameter of the droplet increases and then decreases with the increase in surface temperature.

By carrying out the experimental research on a droplet impact on a heated surface, the students deepened their understanding of the theoretical knowledge, the experimental impact phenomenon, and the variation rule of the dynamic parameters of a droplet impact on a heated surface. In addition, a laboratory lesson was developed and designed based on eight aspects: course objectives, course essentials, experimental process for students, experimental techniques, teaching methods, experimental risks, protective measures, and assessment and feedback, which improved the participation and problem-solving ability of students. The satisfaction of the students with the course was surveyed based on five dimensions: completion of experimental techniques, advanced experimental equipment, interactive course design, diversity of teaching methods, and feedback on teaching quality. The survey results found that the satisfaction levels among students with the experimental courses were all more than 90%. Positive feedback from students not only validates the effectiveness of the experimental teaching methodology but also provides guidance for the continued optimization of teaching methods and course content.