Drag reduction by superhydrophobic surfaces has become a researchfocus in recent years. However, in some cases, the use ofsuperhydrophobic surfaces has led to increased drag. Whethersuperhydrophobic surfaces on macroscopic objects reduce drag needsfurther research. The surface adhesion force is a metric to judge thedrag reduction effect of superhydrophobic surfaces. The latticeBoltzmann method (LBM) is an efficient numerical method with theadvantages of simple algorithm formulation, natural parallelism, andsimple boundary treatment. Based on the LBM, we propose a newboundary condition with switchable adhesive force to specify theadhesion-regulated superhydrophobic surfaces. The proposed method isvalidated by the numerical simulation of the Couette flow withsuperhydrophobic coatings. Numerical results show good agreementswith the theoretical analysis and the experimental results. Then themethod is adopted for the simulation of the flow around a squarecylinder with superhydrophobic coatings. The influence of theReynolds number and the surface adhesive force on drag reduction isdeeply studied.
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