Drag reduction for viscous laminar flow on spray-coated non-wetting surfaces

• Main Authors: Srinivasan, Siddarth (Contributor), Choi, Wonjae (Author), Park, Kyoo-Chul (Author), Chhatre, Shreerang S. (Contributor), Cohen, Robert E. (Contributor), McKinley, Gareth H. (Contributor), Park, Kyoo Chul (Contributor)
• Other Authors: Massachusetts Institute of Technology. Department of Chemical Engineering (Contributor), Massachusetts Institute of Technology. Department of Mechanical Engineering (Contributor)
• Format: Article
• Language: English
• Published: Royal Society of Chemistry, 2013-11-20T20:27:30Z.
• Subjects: Article
• Online Access: Get fulltext

We estimate the effective Navier-slip length for flow over a spray-fabricated liquid-repellent surface which supports a composite solid-air-liquid interface or 'Cassie-Baxter' state. The morphology of the coated substrate consists of randomly distributed corpuscular microstructures which encapsulate a film of trapped air (or 'plastron') upon contact with liquid. The reduction in viscous skin friction due to the plastron is evaluated using torque measurements in a parallel plate rheometer resulting in a measured slip length of bslip z 39 mm, comparable to the mean periodicity of the microstructure evaluated from confocal fluorescence microscopy. The introduction of a large primary length-scale using dual-textured spray-coated meshes increases the magnitude of the effective slip length to values in the range 94 mm # b[subscript slip] # 213 mm depending on the geometric features of the mesh. The wetted solid fractions on each mesh are calculated from free surface simulations on model sinusoidal mesh geometries. The trend in measured values of b[subscript slip] with the mesh periodicity L and the computed wetted solid-fraction ro[subscript s] are found to be consistent with existing analytic predictions.
United States. Army Research Office (Contract W911NF-07-D-0004)
United States. Office of Naval Research (Contract 3002452814)
Air Force Research Laboratory (Wright-Patterson Air Force Base, Ohio). Propulsion Directorate
United States. Air Force Office of Scientific Research