The surface pressure distributions and flow patterns developed on and around a NACA 0012 airfoil undergoing heaving and pitching were investigated at Re = 3.6 × 104. Despite extensive investigations conducted by researchers elsewhere, the surface pressure measurements are, however, not readily available in the open archives, which are of importance not only in understanding the unsteady-airfoil boundary-layer flow but also for computational fluid dynamics (CFD) validation. Nevertheless, the results show that the behavior of the surface pressure distribution and the flow pattern of pure heaving closely resembled those of pure pitching. For combined heaving and pitching, the critical aerodynamic values (such as dynamic Cl,max, peak negative Cm, Cl-hysteresis and torsional damping) always exhibited a maximum value at phase shift ϕ = 0 deg. More interestingly, the ϕ = 180 deg phase shift produced a virtually unchanged surface pressure distribution over an entire combined motion cycle.

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