Fabrication of durable superhydrophobic surfaces using PDMS and beeswax for drag reduction of internal turbulent flow

Nowadays, one of the biggest concerns in the world is increasing the CO2 emissions and global warming due to the over-consumption of fossil fuels. In addition, under the intense market competition, the demand for more efficient systems with higher performance and lower energy consumption has escalated. Since the drag force contributes to a considerable percentage of the energy loss and reducing the performance, a large number of studies have been conducted to improve the surface characteristics and, subsequently, declining the drag force. Making the surface superhydrophobic is one of the most effective ways for this purpose. In this work, two different superhydrophobic surfaces using SiO2 nanoparticles modified by PDMS and beeswax were prepared, which were named PS and BWS, respectively. The results indicate that the coated substrates display excellent water repellency with contact angles of 154.6 degrees and 153.3 degrees for PS and BWS coatings, respectively. Also, the drag reduction tests reveal that the obtained surfaces can result in up to 24% reduction in drag force for internal turbulent flow at Re = 20,000. Furthermore, it is shown that the resultant surfaces possess high durability against various destructive conditions such as immersing in distilled water, seawater, acidic and alkaline solutions.