Experimental investigation on the effect of preprocessing in fabrication of superhydrphobic surfaces on laminar drag reduction

In this paper the effect of roughness on hydrodynamical friction reduction of superhydrophobic surfaces were studied. For this purpose, different non-wettable microchannel with various processing method was fabricated and then the amount of drag reduction in laminar flow was investigated on them. The surfaces were from Aluminum and the four different methods were used to fabricate superhydrophobic surfaces. According to the results, whereas superhydropobic surfaces with hierarchical roughness could lead to a significant skin friction reduction (about 20 %), non-wettable smooth surface did not show a tangible reduction in drag force. Beside this for study the effect of preprocessing method the boiling process was added to the fabrication method. the results indicated that boiling process alongside roughening the substrates as a part of preparation of superhydrophobic surfaces intensified durability of the coated layer and drag reduction (up to 45 %). In addition surfaces which was prepared by adding boiling process were more stable in flow field.