Newsletter  2026.3  Index

Theme : "The Eleventh JSME-KSME Thermal and Fluids Engineering Conference (TFEC11) " Preface Hyun Jin PARK, Shoichi MATSUDA, Chungpyo HONG Post-Lecture Summary: Engine Knock Prediction – Building on Combustion Fundamentals Kaoru MARUTA, Youhi MORII (Tohoku University) Electrical Tomography × Flow Visualization × Startups  – Chiba University Spin-off Startups and the Future of Fluid Engineering – Songshi LI, Masahiro TAKEI (Chiba University) Turbulent drag reduction effects by streamwise traveling waves with spanwise phase shifts Kyohei OISHI (Keio University), Senri MIURA (Keio University), Yusuke NABAE (Tokyo University of Science), Koji FUKAGATA (Keio University) Effect of a sidewall height on the instability of an inclined falling liquid film in a minichannel Shogo Matsui(Yokohama National University), Georg F. Dietze(CNRS, FAST, Université Paris-Saclay, Orsay), Koichi Nishino(Yokohama National University), Misa Ishimura(Yokohama National University) Development of a ReaxFF Force Field for CO2 Separation in PVAm/PVA Composite Membranes: Molecular-Level Insights into Aqueous Transport Mechanism Yukiko TOMITA, Kohei SATO, Ikuya KINEFUCHI (Tokyo University) Flow characteristics of multiple jets and their flow in a chamber Asuka KONDO, Masaki FUCHIWAKI (Kyushu Institute of Technology) Experimental investigation of combined blowing-suction control on a Clark-Y airfoil Senri MIURA, Koji FUKAGATA (Keio University)

 

Experimental investigation of combined blowing-suction control on a Clark-Y airfoil

Senri MIURA Keio University	Koji FUKAGATA Keio University

Abstract

Improving energy efficiency in aviation is a critical challenge that requires effective drag reduction techniques. Uniform Blowing (UB) and Uniform Suction (US) are promising methods where air is minimally injected or removed from airfoil surfaces to manipulate the boundary layer, as illustrated in Fig. 1. While UB reduces friction drag, it often leads to an unintended increase in pressure drag. To address this, the present study proposes a combined control strategy to enhance the lift-to-drag ratio of a Clark-Y airfoil by simultaneously applying UB near the leading edge of the lower surface and US near the trailing edge of the upper surface.

Figure 2 shows the schematic of the experimental setup used in a low-turbulence wind tunnel with a Clark-Y airfoil model. Experiments were performed at a Reynolds number of  and a zero-degree angle of attack, with blowing and suction velocities maintained at 0.39% of the freestream velocity. Wake velocity profiles were measured using hot-wire anemometry at a downstream position of . As can be seen in the close-up view in Fig. 3, the velocity deficit region for the combined control case shifted downward relative to the no-control case. This downward shift indicates flow deflection, qualitatively suggesting an increase in lift.

To quantify the aerodynamic impact, the total drag was calculated based on the momentum flux through the control volume depicted in Fig. 4. The experimental analysis revealed that the total drag decreased by 5.2% under the combined control. This result indicates that the adverse effect on drag is minimal compared to the potential lift enhancement. These findings suggest that the combined UB/US control strategy is a practical and effective approach for improving the lift-to-drag ratio of airfoils in cruise conditions.

Key words

Airfoil, Wind-tunnel Experiment, Friction Drag Reduction, Blowing, Suction

Figures

Fig. 1  Uniform blowing on an airfoil surface.

Fig. 2  Schematic of experimental setup.

Fig. 3  Wake velocity profile.

Fig. 4  Schematic of the control volume.