난류채널유동에서의 준최적제어 평가

Abstract

A systematic analysis is made of suboptimal control for drag reduction. The influence of the amplitude of actuation (A) and the time scale of actuation (Δt(sub)a(sup)+) is evaluated. Two wall sensing variables are employed (∂w/∂y│(sub)w and ∂p/∂z│(sub)w) with two wall actuations (Φ2and Φ3). To test the suboptimal control, direct numerical simulations of turbulent channel flow at Re(sub)τ=100 are performed in a spectral domain. It is found that the effect of A and Δt(sub)a(sup)+∼1. The near-wall behaviors of flow structure are analyzed to characterize the drag reduction. The size effect of the sensor/actuator is examined.