Newsletter  2019.3  Index

Theme : "The Conference of Fluid Engineering Division" Preface (T. HASHIMOTO，S. MATSUDA，H.J. PARK) Development and launch of sounding rockets and development status of small launch vehicle by Japanese startup company Takahiro INAGAWA (Interstellar Technologies Inc.) Experimental quantification of friction drag reduction effects on an airfoil using uniform blowing Kaoruko ETO, Yusuke KONDO, Koji FUKAGATA (Keio University)and Naoko TOKUGAWA (Japan Aerospace Exploration Agency) Wind-tunnel experiments of friction drag reduction on an airfoil using passive blowing Shiho HIROKAWA, Kaoruko ETO, Yusuke KONDO, Koji FUKAGATA (Keio University)and Naoko  TOKUGAWA (Japan Aerospace Exploration Agency) A Study on Airfoil Flow and Aerodynamic Noise with Wake-boundary layer Interaction Noriaki KOBAYASHI　(The University of Tokyo) LES Analysis of Stator Cascade Flow in a Transonic Axial Compressor Seishiro SAITO (Kyushu University) Influence of grid resolution in large-eddy simulation of a turbulent pipe flow using the WALE model Daiki IWASA, Yusuke NABAE, Koji FUKAGATA (Keio University) The Dreams of Flow Contest Tomomi TERADA (Hokkaido University)   Separation of floating waste by "Water Surface Control Device" Toshiki HOMMA　 (Meisei University)

 

A Study on Airfoil Flow and Aerodynamic Noise with Wake-boundary layer Interaction

Noriaki KOBAYASHI The University of Tokyo

Abstract

The purpose of this study is to clarify dominant sources of aerodynamic noise generated from an airfoil flow with turbulent inflow. This abstract presents the results of wind tunnel experiments and decoupled simulations of computational fluid dynamics (CFD) and computational aeroacoustics (CAA) based on large eddy simulation (LES) and Lighthill’s acoustic analogy. Figure 1 and 2 show the experimental set-up and flow field around the airfoil, respectively. A circular cylinder is installed upstream of the airfoil in order to generate turbulent inflow condition. Figure 3 shows computational grids respectively used for CFD (left) and CAA (right). In our CAA simulations, sound-pressures spectra and acoustical fields are predicted, respectively, by Curle's equation and by solving wave equation with Lighthill's tensor computed by incompressible LES. Figures 4 and 5 show the results of experiments and simulations: surface pressure distributions and aerodynamic sound spectra. The simulated results are in good agreement with the experiments. Figures 4 and 6 show that the pressure fluctuation near the leading edge is remarkably high with turbulent inflow condition, and that the vortices collide with the airfoil surface and they are stretched from the stagnation point to suction surface where the mean flow is accelerated. From figure 7, the dominant source of the aerodynamic noise radiated from the airfoil flow under turbulent inflow condition has been identified to be this stretch of the vortices by the acceleration of the mean flow near the leading edge of the airfoil.

Key words

Airfoil noise, Inflow turbulence, Wake-boundary layer interaction, Wind-tunnel experiment, Large Eddy Simulation, Acoustical computation

Figures

Fig. 1 Experimental set-up of test section

Fig. 2 Time-averaged streamlines and main velocity around airfoil computed by LES

Fig. 3 Computational grids for CFD (left) and CAA (right)

Fig. 4 Mean (left) and fluctuating (right) pressure distributions on airfoil surface

Fig. 5 Frequency spectra of sound radiated from airfoil and/or cylinder

Fig. 6 Static pressure and vertical structures with (right) and without (left) cylinder

Fig. 7 Sound-pressure level with (right) and without (left) cylinder