In this presentation I will highlight recent developments on the use of nanoparticles based superhydrophobic coating for the reduction of drag and related energy saving on solid objects moving in water. Superhydrophobic textured coating are deposited on metallic spheres using a commercially available product containing organic molecules modified silica nanoparticle. The coating is robust and stable to temperature as high as 400 °C, giving the opportunity to sustain not only a natural air layer on surface in contact with water but a thick vapor layer on the heated sphere surface. Experiment comparing the fall velocity of the original spheres and superhydrophobic spheres in a large water tank are used to evaluate the drag reduction effect of the gas layers. A very significant drag reduction up to 80% is demonstrated for heated superhydrophobic sphere sustaining a thick vapor layer and the same effect is replicated for the thin air layer naturally sustained on the superhydrophobic coating, although for a narrower range of sphere velocities. Finally we show an intriguing phenomenon of air entrapment during the impact of superhydrophobic coating sphere on water resulting in a neat zero drag sphere-cavity object .
Audience take away:
• Water repellent coating based on commercially available nanoparticle suspensions
• Naturally sustained and thermally activated gas layers on superhydrophobic interfaces
• Energy saving potential of gas layers on nanoparticle coatings based lubrication