Effects of Periodic Holes on the Suppression of Aeroacoustic Noise From a Pantograph Horn

2003 ◽  
Author(s):  
Takehisa Takaishi ◽  
Mitsuru Ikeda ◽  
Chisachi Kato
Keyword(s):  
Wind Tunnel ◽  
Acoustic Resonance ◽  
Flow Fields ◽  
Low Noise ◽  
Aerodynamic Noise ◽  
Spanwise Direction ◽  
Large Structure ◽  
Unstable Flow ◽  
Aeroacoustic Noise ◽  
Flow Through

Three types of pantograph horn model; simple cylinder, a cylinder with periodic holes and a cylinder with a continuous slit, are tested in a low noise wind tunnel to compare their characteristics of aerodynamic noise and flow fields in the wake. Formation of strong vortices of alternate sign that have large structure in the spanwise direction is suppressed due to the flow through holes or the slit. The cylinder with the continuos slit is proved to reduce the noise sufficiently, but an unstable flow through the slit seems to produce distinct noise. Since formation of strong vortices is mainly suppressed due to momentum injection through holes or the slit, periodic holes have little effect on collapsing the spanwise structure of vortices, but they contribute to making the flow around the horn stable. The shape of holes should be optimized to avoid strong acoustic resonance.

scholarly journals Measurement of Mutual Interference Sound of Columnar Objects in Air Flow

2018 ◽  
Vol 151 ◽  
pp. 03004
Author(s):  
Shohji Hamada ◽  
Yoshifumi Yokoi
Keyword(s):  
Wind Tunnel ◽  
Flow Field ◽  
Flow Visualization ◽  
Mutual Interference ◽  
Low Noise ◽  
Aerodynamic Noise ◽  
Flow State ◽  
Visualization Experiment ◽  
Experimental Apparatus ◽  
Karman Vortex

When a columnar object is put in a flow, Karman vortex is formed, and aerodynamic noise is generated. It is known that when multiple columnar objects are put in a flow, the flow state becomes complex. This can be known by flow visualization experiment. On other hands, there are few researches on flow sound in the case of mutual interference, that it is not as far as the authors know. Measurement of flow sound is performed using a microphone. Therefore, it is necessary to confirm the sound of the interference flow field reaches the microphone outside the flow field without changing. In this research, experiments were measured to confirm flow sound transmits to a microphone placed outside the flow field without changing. Based on the results, the aerodynamic noise measurement from the columnar object was performed using a low noise wind tunnel experimental apparatus. As a result, it was obtained that some findings on the sound of flow in mutual interference flow field

scholarly journals 3D Acoustic Mapping in Automotive Wind Tunnel: Algorithm and Problem Analysis on Simulated Data

2021 ◽  
Vol 11 (7) ◽  
pp. 3241
Author(s):  
Gianmarco Battista ◽  
Paolo Chiariotti ◽  
Milena Martarelli ◽  
Paolo Castellini ◽  
Claudio Colangeli ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Problem Definition ◽  
Aerodynamic Noise ◽  
Accurate Information ◽  
Problem Analysis ◽  
Wind Tunnel Testing ◽  
Experimental Conditions ◽  
Automotive Manufacturing ◽  
Acoustic Mapping ◽  
Tunnel Testing

Localization and quantification of noise sources are important to fulfill customer and regulation requirements in a such competitive sector like automotive manufacturing. Wind tunnel testing and acoustic mapping techniques based on microphone arrays can provide accurate information on these aspects. However, it is not straightforward to get source positions and strengths in these testing conditions. In fact, the car is a 3D object that radiates noise from different parts simultaneously, involving different noise generation mechanisms such as tire noise and aerodynamic noise. Commonly, acoustic maps are produced on a 3D surface that envelopes the objects. However, this practice produces misleading and/or incomplete results, as acoustic sources can be generated outside the surface. When the hypothesis of sources on the model surface is removed, additional issues arise. In this paper, we propose exploiting an inverse method tailored to a volumetric approach. The aim of this paper is to investigate the issues to face when the method is applied to automotive wind tunnel testing. Two different kinds of problem must be considered: On the one hand, the results of inverse methods are strongly influenced by the problem definition, while, on the other hand, experimental conditions must be taken into account to get accurate results. These aspects have been studied making use of simulated experiments. Such a controlled simulation environment, by contrast to a purely experimental case, enables accurate assessment of both the localization and quantification performance of the proposed method. Finally, a set of scores is defined to evaluate the resulting maps with objective metrics.

Two-Dimensional Flow With Standing Vortexes in Ducts and Diffusers

1960 ◽  
Vol 82 (4) ◽  
pp. 921-927 ◽  
Author(s):  
Friedrich O. Ringleb
Keyword(s):  
Wind Tunnel ◽  
Potential Flow ◽  
Separation Control ◽  
Two Dimensional ◽  
Dimensional Flow ◽  
Princeton University ◽  
Two Dimensional Flow ◽  
Flow Through ◽  
Trapping Devices

The conditions for the equilibrium of two vortexes in a two-dimensional flow through a duct or diffuser are derived. Potential-flow considerations and a few basic results from viscous-flow theory are used for the discussion of the role of cusps as separation control and trapping devices for standing vortexes. The investigations are applied to cusp diffusers especially with regard to the wind tunnel of the James Forrestal Research Center of Princeton University.

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