Study about boundary-layer suction at a juncture for sustained laminar flow

Abstract

Two-dimensional direct numerical simulations (DNS) are used to study the influence of active and passive suction at the juncture between two wing elements on laminar-turbulent transition. Suction is applied through the juncture’s gap in front of a forward-facing step. For first, fundamental investigations, the juncture is located in a compressible flat-plate boundary-layer flow without streamwise pressure gradient. To quantify the impact of suction on laminar-turbulent transition, N-factors are calculated. For this, the growth of introduced Tollmien-Schlichting (TS) waves is evaluated according to the eN method. Depending on the perilousness of juncture shapes, suction is capable or incapable to compensate their negative impact on laminar-turbulent transition. In addition to active suction, a method allowing passive suction is presented. The work concludes with a discussion about possible integrations of suction at aerodynamic elements, in particular at wings.