Hiroki Ura

Designing of Slat Cove Filler as a Noise Reduction Device for Leading-edge Slat

The purpose of this study is to design noise reduction devices for leading-edge slat which is called as a slat cove filler (SCF), from both aerodynamic and acoustic points of view. From the previous studies, a SCF seems to have an effect on reducing broadband noise by forming substantially continuous shape instead of a slat cusp configuration. However, there are some studies which indicate the decrease of aerodynamic performance when the SCF is attached. Since the primary feature of high-lift-devices is to increase aerodynamic performance, reduction of maximum lift coefficient or stall angle etc. is not acceptable even if the device is effective in reducing noise. In order understand both features, two kinds of flow solver, UPACS and UPACS-LES codes, are used to simulate steady and unsteady flows around slats. The UPACS code is used mainly for aerodynamic force prediction, and UPACS-LES is used to understand the noise generation and reduction mechanism. Based on the simulations, it became apparent that if the SCF is designed while maintaining the geometry around the slat trailing edge and the main element leading edge, the aerodynamic performance will be the same as that of the baseline. Also, to suppress the noise as much as possible, it is important to reduce small separation along the lower surface of a SCF, which seems to be caused by adverse pressure gradient. Additionally, wind tunnel experiments are performed for verification purpose. The SCF designed in this study satisfies both aerodynamic and acoustic performance successfully.

High-Lift Device Testing in JAXA 6.5M X 5.5M Low-Speed Wind Tunnel

To obtain detailed validation data for a complicated high-lift system including aerodynamics, aeroacoustics, flow visualization, and so on, half-span large-scale high lift device model was tested in JAXA 6.5m x 5.5m Low-speed Wind Tunnel. Five-component aerodynamic force and aeroacoustic noise with phased array microphones were measured simultaneously, and surface pressure with pressure taps and Pressure Sensitive Paint (PSP), unsteady pressure using surface mounted pressure sensors, and velocity distribution around the model using Particle Image Velocimetry (PIV) were obtained. Surface flow visualization with oil flow and china clay method were also carried out. Here, overview of the testing and verification data for CFD which were successfully obtained is reported. Moreover, those various measurements were able to reveal important aspects of flow field around nacellepylon which dramatically affected to aerodynamic force, surface pressure, and also aeroacoustic noise.

Experimental Study of Slat Noise from 30P30N Three-Element High-Lift Airfoil in JAXA Hard-Wall Low-Speed Wind Tunnel

Aeroacoustic measurements associated with noise radiation from the leading edge slat of the canonical, unswept 30P30N three-element high-lift airfoil configuration have been obtained in a 2 m x 2 m hard-wall wind tunnel at the Japan Aerospace Exploration Agency (JAXA). Performed as part of a collaborative effort on airframe noise between JAXA and the National Aeronautics and Space Administration (NASA), the model geometry and majority of instrumentation details are identical to a NASA model with the exception of a larger span. For an angle of attack up to 10 degrees, the mean surface Cp distributions agree well with free-air computational fluid dynamics predictions corresponding to a corrected angle of attack. After employing suitable acoustic treatment for the brackets and end-wall effects, an approximately 2D noise source map is obtained from microphone array measurements, thus supporting the feasibility of generating a measurement database that can be used for comparison with free-air numerical simulations. Both surface pressure spectra obtained via KuliteTM transducers and the acoustic spectra derived from microphone array measurements display a mixture of a broad band component and narrow-band peaks (NBPs), both of which are most intense at the lower angles of attack and become progressively weaker as the angle of attack is increased. The NBPs exhibit a substantially higher spanwise coherence in comparison to the broadband portion of the spectrum and, hence, confirm the trends observed in previous numerical simulations. Somewhat surprisingly, measurements show that the presence of trip dots between the stagnation point and slat cusp enhances the NBP levels rather than mitigating them as found in a previous experiment.

Experimental study on Noise Generation of a Two-Wheel Main Landing Gear

This paper deals with results of noise measurements for a 40% of two-wheel type aircraft main landing gear in lowspeed wind tunnel experiments. In order to accurately assess a noise source location and far-field characteristics during the approach phase, scale model with complex geometry which was equipped with small components such as link mechanism, hydraulic tubes and electrical wiring as well as a tire, a cylinder, a piston, doors, and a sidebrace was used. Model geometry was based on LEG (Landing gear noise Evaluation Geometry) which was designed by a gear manufacturer assuming 100-PAX class regional jet airliner. Experimental results obtained in two kinds of wind tunnels, which were 2m by 2m lowspeed wind tunnel in JAXA and large scale anechoic facility of Railway Technical Research Institute of Japan, showed dominant noise sources around a tire, a sidebrace, some parts of the door and also the junction between the cylinder and the sidebrace. Among these prominent noise sources, the tire and the sidebrace were large contributor to the total of noise level. It was found that noise characteristics around 1kHz was important not only in the amplitude but also in directivity for an actual aircraft scale. Representation of small components and geometry of an actual landing gear even in a scale model seemed to be effective of several decibels in noise level.

Aerodynamic/Aeroacoustic testing in Anechoic Closed Test Sections of Low-speed Wind Tunnels

This paper describes new anechoic closed test sections in Japan Aerospace Exploration Agency (JAXA) and Virginia Tech (VT) not only for an aeroacoustic but also for an aerodynamic testing ability in Low-speed wind tunnels. The anechoic closed test section with Kevlar wall is an innovative concept and had been originally developed at VT. It was later applied to JAXA’s 2m x 2m wind tunnel. By using a high-lift device model, the JAXAs new test section was evaluated and validated acoustically by comparing to VT anechoic test results. Moreover, the aerodynamic characteristics in the new test section were also evaluated by comparing to results of the same model in JAXAs closed hard-wall test section. New wall interference correction procedure is proposed for the Kevlar wall test section, and it showed very good agreement with well-known corrected hard-wall results. This anechoic test section is useful and a promising tool for both aerodynamic and aeroacoustic testing.

A Far-field Noise and Near-field Unsteadiness of a Simplified High-lift-configuration Model (Slat)

Airframe noise generation at the flap-edge is investigated on a simplified three elements high-lift configuration wing model. Lowspeed wind tunnel experiments for aerodynamics measurements in JAXA-LWT2 and noise measurements in Large scale anechoic facility of Railway Technical Research Institute as well as steady-state Reynolds-Average NavierStokes computation (RANS) has been implemented. Cross spectrum analysis and computational results connect the far-field noise and the near-field unsteadiness, and then show the noise generation mechanism around a flap-edge. Flap-edge noise component around 2.5kHz is caused by the oscillation of the merged longitudinal vortex, which is formed by the top-side vortex and the side-edge vortex, in downstream area. The vortex is excited by shear layer instability at a lower corner of the flap-edge. In addition, three kinds of the flap-edge shape modification are tested. As a result, reduction of the far-field noise is achieved with specific shapes. Most effective modification is LowerRound flap-edge which has rounded corner at the lower side and a sharp-edge at upper side. Furthermore, variations in the vortical structures at the flap-edge with/without low noise shape are discussed using the data provided by PIV measurement and computation.

Phased Array Measurement of High Lift Devices in Low Speed Wind Tunnel

The aeroacoustic measurement using a half-span aircraft model equipped with high lift devices was carried out for the first time in JAXA 6.5m x 5.5m low speed wind tunnel. As the result of this test, the noise sources located at main wing tip, slat tracks, slat tip, flap tip, the slat-pylon region and so on are observed. The noise generated from wing tip and outboard flap tip had a strong dependence on Reynolds number and angle of attack. However, the noise generated from slat tracks and the slat-pylon region didn’t have a dependence on neither Reynolds number nor angle of attack. In this paper, a phased array system in JAXA is introduced, then the results of noise measurements for high lift devices are presented.

Numerical Investigation on Change of Airframe Noise by Flap Side-edge Shape

This paper presents computational and experimental studies on the flap side-edge noise using a three-element rectangular high-lift wing model with a full-span slat and a part-span flap for high-lift device noise research in JAXA. The main purpose of this paper is focused on the numerical investigation of change of the flowfield and far-field noise by the flap sideedge shapes. Several flap side-edge configurations with rounded flap side-edges, a cavity side-edge, and a protruding-type device on the lower surface of flap are investigated in this paper. By the computations and wind tunnel tests, mechanisms of the noise generation and reduction of flap side-edge noise are discussed.

Noise Generation Characteristics of a High-lift Swept and Tapered Wing Model

In this paper, noise generation from high-lift devices (HLDs) of a sweptand taperedwing model OTOMO2 measured in low speed wind tunnel experiments are discussed. OTOMO2 has a wing section of simplified high-lift configuration rectangular model OTOMO, and also has a planform of a realistic high-lift configuration aircraft model JSM. Main purpose of the experiment was to answer the questions about the influence of model geometry on HLD noise, which remained in our previous research using the rectangular model OTOMO. Results of the far-field noise measurement in RTRI-Maibara low noise wind tunnel and noise source maps obtained in JAXA-LWT2 low speed wind tunnel are mainly used. Comparison of narrow band spectra of the far-field SPL and noise source maps for the approach, the flap-only-deployed and the slat-only-deployed configurations showed characteristics of the noise generation of the flap-edge and the slat. One of the most remarkable finding was the existence of the multiple tonal component (MTP) in the slat noise spectrum in sweptand tapered-model geometry. The movement of the MTP noise sources along the spanwise location was observed, which was similar phenomenon to the rectangular model geometry. However, for the sweptand tapered-wing model, it is considered that the flow field which is suitable for the MTP generation is produced more locally and it changes continuously along spanwise direction with the variation of the angle of attack. The noise generation of the flap-edge in the sweptand tapered-model geometry was also different from that of the rectangular model geometry because there was the angle of attack dependency. Then it is suggested that there probably existed three different noise sources around the flap-edge.

Numerical and Experimental Research of Low-Noise Slat Using Simplified High-lift Model

This paper focuses on numerical and experimental research for designing low-noise slat on a simplified high-lift configuration model (OTOMO). Two types of noise reduction devices are considered. First device is a slat cove filler (SCF). From the previous studies, SCF seems to have an effect on reducing broadband noise by forming substantially continuous shape instead of a slat cusp configuration. Several different geometries are designed and tested experimentally as well as numerically. The second device is called thin slat (TS). This device maintains the leading edge radius of the baseline slat and cusp region is shaved off to avoid separation from the cusp. Interestingly, the aerodynamic performance, such as maximum lift coefficient and stall angle, will be maintained while noise reduction is achieved. These results indicates that lower surface slat could be designed for the low noise configuration without aerodynamic penalties.