Robert Reger

An Experimental Study of the Rudimentary Landing Gear

Fluid dynamic and aeroacoustic wind tunnel experiments are performed on a rudimentary landing gear model. The primary objective of these tests is to provide a set of acoustic data for verification of computational fluid dynamic and aeroacoustic simulations. Data acquired include mean and fluctuating surface pressures and acoustic measurements obtained by a linear array of 10 free-field microphones. Two primary configurations are tested, the first with one side bounded by a large aluminum baffle plate on the wing side of the model and the second with the plate removed. Mean surface pressure and acoustic measurements are obtained at speeds from Mach 0.09 up to Mach 0.18 and fluctuating surface pressures are obtained up to Mach 0.12. Surface pressure measurements are compared to data acquired by the National Aerospace Laboratories in a closed-jet wind tunnel. Similar trends are obtained with noticeable differences occurring due to the differences between the openand closed-jet configurations. Analysis of the acoustic data show that the bounding plate acts as a significant reflection source. The far-field sound pressure levels for either case do not scale with Mach number to the 6 th power or Strouhal number alone, but do collapse well when both scaling parameters are applied together.

Experimental Study of the Rudimentary Landing Gear Acoustics

C OMPUTATIONAL fluid dynamics (CFD) has long been a tool capable of mapping flows around complex geometries, providing answers to intricate problems that are either prohibitively expensive or time consuming to perform experimentally. However, without experimental testing, there would be no way to validate the numerical results provided. The rudimentary landing gear (RLG)was designed by Dr. Phillipe R. Spalart of The Boeing Company and presented in Stockholm in June 2010 as part of the First AIAA Benchmark Problems for Airframe Noise Computations workshop [1]. Its primary purpose is to provide a standard model for noiseoriented CFD validation. Therefore, the geometry needed to be complex enough to create an interesting flowfield but simple enough for reliable physical experiments and computational simulations. The National Aerospace Laboratories (NALs) in India have completed an aerodynamic investigation on aRLGmodel in a closedwall wind tunnel [2]. During these tests, steady and unsteady pressure datawere taken and surface oilflow visualizationwas performed. The purpose of this Note is to document corresponding aeroacoustic measurements of a scaled RLG model that was used as the benchmark data for the Second AIAA Benchmark Problems for Airframe Noise Computations workshop (BANC-2).

Design-optimization of a broadband phased microphone array for aeroacoustic applications

Phased microphone arrays are commonly used in acoustic beamforming applications. While numerous beamforming algorithms have been proposed to alleviate deficiencies of the delay-and-sum approach, few studies have focused on the array design itself. In aeroacoustic applications, the most common designs are based on circularly symmetric spiral arrays devised by Underbrink (1995). The design of an array using such a method is complex and tedious due to the numerous design variables and corresponding trade-offs between resolution, sidelobe suppression, size, and cost. In this paper, a systematic design-optimization approach is described that offers several objective functions and constraints. Candidate arrays for use in the University of Florida Aeroacoustic Flow Facility (UFAFF) are designed for a broadband frequency range of 1 to 80 kHz. The results of these different cases will be compared to those of an existing array design currently used in the UFAFF. An optimized design is selected and fabricated for ch...

A Method for Estimating Surface Pressure Forces and Far-Field Acoustics

The field of aeroacoustics is one of growing importance in the modern world, from noise pollution by commercial airplanes to quieter automobiles on the highway. With an apparent gap between theoretical predictions of acoustic sources and those measured in practice, the need arises for a method to estimate the acoustics while incorporating experimentally measurable quantities to bridge the two. The present study describes a method for calculating the surface pressure forces from global velocity measurements and discrete surface pressure measurements by solving Poisson’s equation for fluctuating pressure. The integrated fluctuating surface pressure force is then used as a source in Curle’s acoustic analogy to obtain an estimate of the far-field acoustics. These analysis tools are first studied using data obtained from DNS of flow over a cylinder with ReD = 150 to verify their accuracy and highlight the effects of experimental error in each stage of analysis. A turbulent wall jet with ReH = 25,500 is then examined with the analysis tools, using synchronized particle image velocimetry and surface mounted pressure transducers. The results show the tool’s ability to predict far-field acoustics but highlight that care must be taken to limit the effects of measurement noise.