Efficiency of Air Microblowing Through Microperforated Wall for Flat Plate Drag Reduction

Efficiency of air microblowing through a permeable (microperforated) wall to reduce the turbulent skin-friction drag of a flat plate in a nominally gradientless incompressible flowwas studied experimentally. Themass flow rate of the air blowing per unit area ranged from 0 to 0:0739 kg=s=m that corresponded to the maximum blowing coefficient equal to 0.00287. Unlike the pioneering work of Hwang (Hwang, D. P., “A Proof of Concept Experiment for Reducing Skin Friction by Using a Micro-Blowing Technique,” AIAA Paper 1997-0546, 1997.), the main emphasis was directed to investigate detailed boundary-layer characteristics over the permeable surface. This knowledge was necessary to make real-time decisions for the experiment setup refinement to achieve the maximum efficiency of the control method under study. A consistent reduction of the local skin-friction coefficient over the permeable insert at various values of the blowing coefficient was shown, reaching a maximum reduction of 70%. It was also established that the microblowing can provide reduction of the plate total drag of about 4.5–5%. Applicability of simple physical models to describe some characteristics of the turbulent boundary layer formed above the permeable wall was considered.