Experimental investigation of wake-induced aeroelastic limit cycle oscillations in tandem wings

Abstract

This paper aims to experimentally investigate multi-body aeroelastic wing–wake interactions to quantify how structural properties dictate vortex energy transfer. The paper examines three different components needed to study this phenomenon; first, single wing aeroelastic response and wake characteristics; second, flutter boundary characteristics of tandem aeroelastic wings with wing–wake interactions; third, limit cycle behavior and wake frequency content in tandem oscillating wings. Single wing and tandem wing–wake studies conducted through hot-wire anemometer sweeps downstream of the trailing edge find dominant frequency content and wake velocity profiles. Pitch stiffness on the downstream wing is varied to be less than or equal to that of the upstream wing. It is hypothesized that pitch stiffness modulates the sensitivity of the wing to incoming vortex disturbances thus changing vortex energy transfer to the wing. The experimental results showed that the limit cycle and transient response of the downstream wing in tandem configuration are dependent on its pitch stiffness, while the aeroelastic stability and flutter point of the downstream wing is dictated by the upstream wing. In addition, the wake frequency content in tandem configuration demonstrates strong dependence on downstream wing pitch stiffness. The results show that highest wake energy transfer occurs when the downstream wing pitch stiffness is less than pitch stiffness of the upstream wing.