Meeting Abstract

51.2  Monday, Jan. 5  A Mathematical Model of the Detection of Unsteady Flow Separation by Hairs on a Bat Wing DICKINSON, B. T.*; SWARTZ, S. M.; BATTEN, B. A.; Oregon State University dickinsb@onid.orst.edu

Many animals use hair-like structures to detect flow fields. Bats fly at Reynolds numbers where flow is unsteady, so they must be able to detect and react to changes in flow across the wings to maintain control. Studies have shown that bats have arrays of small (0.1 to 4.0 mm) hairs distributed across the dorsal and ventral wing membrane surfaces. These are hypothesized to detect flow fields, enabling the bat to adjust its wing shape and kinematics to control flight stability. In this work, we created a mathematical model of hairs in a fluid to test their sensitivities to different flow regimes. We sought to determine whether hairs would be able to detect separation of flow, which should occur in unsteady flow regimes, and would have important aerodynamic consequences for flight. Our simulations show that hair sensor arrays are sensitive to characteristic features of unsteady flow separation, including the formation, presence and span of reversed flow on the wing. These results are consistent with the hypothesis that bats use hair cell arrays to detect and control unsteady air flows over the wing during flight.