Yoshinori Ooba

Experimental and Computational Approach for Jet Noise Mitigation by Mixing Control Devices

The notched nozzle as a new concept has been investigated for conventional nozzle design together with the Chevron nozzle and Micro-jets, through feasibility studies. The notched nozzle has a plurality of triangular pyramid-shaped dent positioned in a circumferential direction along the nozzle exit. These studies include acoustic experiments that utilize a lab-scale simple model in an anechoic chamber and numerical approaches. The results of the Large Eddy Simulation are compared with the results of either acoustic or aerodynamic experiments. The objective of these investigations is to verify the effects of noise mitigation and to gain understanding of the physics of fluid dynamics around the nozzle exit, especially within the shear layer between high velocity jet flow and external flow/or ambient air. One concept of conventional noise mitigation devices involves mixing enhancements in the shear layer, but this sometimes produces high frequency self noise. Moreover it will result in a penalty in terms of thrust loss, additional weight and extra manufacturing cost due to the complicated shapes around the nozzle exit. It is difficult to produce a nozzle design without affecting high frequency self-noise and decreasing low-frequency noise towards to down stream of the jet engines even though there is no thrust loss. Most of this study, the experimental data were physically validated by three kinds of nozzle concepts designed to be equal to the conventional model in terms of size of nozzle exit diameter and Mach number. Essentially far-fields noise measurements and pressure measurements are conducted by polar angle microphones and arch-shaped pitot tubes are located downstream of the jet. The noise benefit which is produced by the notched nozzle as a lab-scale in far-fields noise measurements is up to 1.3dB at the side of the jet and 0.5dB at downstream, in terms of size of small-engine. Furthermore this provided an advantage over the chevron nozzle due to the decreasing self-noise production when the Mach number of the jet was lower than 0.9. Moreover, numerical predictions which are provided by the Large Eddy Simulation were used to estimate the noise mitigation by performing turbulence statistical analysis. Numerical results which refer to the turbulent statistics are discussed in order to define how they can be affected to the acoustic results at the side of the jet. This shows how each device can deform the shear layer without producing additional streamwise and small scale vortices.Copyright

Large Eddy Simulation Analysis of Lobed Mixer Nozzle

Large Eddy Simulation (LES) was applied to predict the mixing characteristics of a lobed mixer nozzle analysis. LES was first validated by using experimental data of a convergent-divergent nozzle (CD nozzle) flow. Then, the LES results of the lobed mixer nozzle with a ejector duct were evaluated by comparing with measured data. LES analysis provided more reasonable agreement than Reynolds-averaged Navier Stokes (RANS) analysis.

Experimental and Numerical Research of Fan Bypass Duct Flows in Japanese Environmentally Compatible Engine for Small Aircraft Project

This research aims at developing fan integration technologies to improve the installation loss due to the fan/OGV/strut/pylon interaction of gas-turbine engines for small aircraft on Small Aircraft Project in Japan (the ECO Engine Project). Researches on experimental measurement using fan rig testing and numerical prediction using unsteady CFD analysis are conducted. The UPACS code which is developed by JAXA is used in order to accurately simulate the phenomena which occur in the interaction between a rotating fan and its downstream obstacles like strut/pylon in the fan duct. The accuracy of the CFD simulation is also validated by the measured data acquired in the rig testing. Through the investigations, its interaction mechanisms are clarified and the reducing technologies of such interaction for small aircraft engines are created. In the paper, the achievement of the improved aerodynamic performance by introducing the new concept of the long nose shaped fat pylon L/E are demonstrated.Copyright

Unsteady Three-dimensional Simulation Research of Fan- OGV-Str ut-Pylon Inter action in J apanese ECO Engine Project

This r esear ch aims at developing fan integr ation technologies to impr ove the installation loss due to the fan/OGV/str ut/pylon inter action of gas-tur bine engines for small air cr afts on the ECO Engine Pr oject in J apan. Resear ches on numer ical simulation using unsteady CFD analyses ar e conduced to pr edict the potential field distur bance which occur s due to such inter action in the fan duct and to under stand its influences on the flowfield of the fan and the fan duct. UPACS code which is developed by J AXA is used in or der to accur ately simulate the phenomena which occur in the inter action between the r otating fan and its downstr eam obstacles. The accur acy of the pr edicted r esults is evaluated by compar ing with the measur ed data acquir ed in the fan r ig testing by IHI. In this paper , the mechanisms of its inter action and the total pr essur e loss which occur s in the fan duct ar e descr ibed.

Large Eddy Simulation of a Lobed Mixer Nozzle using a Multi-Block Method

Abstract Large Eddy Simulation (LES) using a multi-block method with a parallel computational algorithm was applied to predict the mixing characteristics of a lobed mixer nozzle flow. In the LES, the Favre filtered compressible Navier-Stokes equations were used for the governing equations and the Smagorinsky subgrid scale turbulence model with Smagorinsky constant 0.15 was introduced in order to determine the SGS turbulence viscosity. First, the LES of a computational model with 7.5 million grid points for a 18-lobe convoluted mixer nozzle was conducted. In the LES calculation, only one-lobe domain of the mixer nozzle was simulated using circumferential periodic boundary conditions at circumferential boundary ends of the computational domain. The computational domain was divided into 9 sub-domains. The LES results were evaluated by comparing with measured data acquired by using particle image velocimetry (PIV) technique, and the good agreement between the LES results and the experimental data was obtained. Next, the LES application was extended to a three-lobe domain of the mixer nozzle. The computational domain was divided into 19 sub-domains and the total number of the computational mesh was about 15.6 millions. The LES calculation was performed by increasing sub-domains without so many modifications of the computational program. From these results, it was demonstrated that the LES using the multi-block method with the parallel computational algorithm had the capability to predict the flowfield of a large computational domain with a huge number of grid points.