424 平板境界層における乱流・層流スパン方向界面の構造解明とその制御(S35-2 乱流渦構造(2),S35 乱流渦構造)  [in Japanese] 424 Structure investigation and suppression control of the spanwise interface between laminar and turbulent regions in a flat plate boundary layer  [in Japanese]

The spanwise interface between laminar and turbulent regions is experimentally investigated. The interface is detected by a rake of single hotwire probes and then its structure is measured in detail using a X-type probe. Output signals of these probes are analyzed by a conditional sampling technique together with an ensemble-averaged method. As a result, it is found that the turbulent region always starts to stick out into the laminar region at the middle height of the boundary layer, where a pair of longitudinal vortices aligned in the wall-normal direction induces the flow from turbulent to laminar regions. The expansion of the turbulent region is successfully suppressed by destroying these vortical structures using a thin plate.