Direct numerical simulations of the flow around wings with spanwise waviness at a very low Reynolds number

- We use DNS to study the effect of spanwise waviness on the flow around wings.
- A vast parameter space was considered for infinite wings with Re=1000.
- The waviness leads to reductions of lift-to-drag ratio and lift fluctuations.
- We propose a physical mechanism to explain the results.

Inspired by the pectoral flippers of the humpback whale, the use of spanwise waviness in the leading edge has been considered in the literature as a possible way of improving the aerodynamic performance of wings. In this paper, we present an investigation based on direct numerical simulations of the flow around infinite wavy wings with a NACA0012 profile, at a Reynolds number Re=1000. The simulations were carried out using the Spectral/hp Element Method, with a coordinate system transformation employed to treat the waviness of the wing. Several combinations of wavelength and amplitude were considered, showing that for this value of Re the waviness leads to a reduction in the lift-to-drag ratio (L/D), associated with a suppression of the fluctuating lift coefficient. These changes are associated with a regime where the flow remains attached behind the peaks of the leading edge while there are distinct regions of flow separation behind the troughs, and a physical mechanism explaining this behaviour is proposed.