Wake-body interaction Noise Simulations by Coupling CFD and BEM

2021 ◽  
Vol 263 (1) ◽  
pp. 5360-5371
Author(s):  
Masaaki Mori
Keyword(s):  
Heat Exchanger ◽  
Vortex Shedding ◽  
Peak Frequency ◽  
Vortex Interaction ◽  
Sound Generation ◽  
Rotating Blades ◽  
Body Interaction ◽  
Noise Radiation ◽  
Dominant Peak ◽  
Small Spacing

In many engineering applications, the wake-body interaction or body-vortex interaction (BVI) occurs. In the wake-body interaction, vortices shed from an upstream obstacle interact with downstream obstacle and generate noise, for example blades in a turbomachinery, tubes in a heat exchanger, rotating blades like a helicopter and wind turbine and so on. The rod-airfoil and airfoil-airfoil configurations are typical models for the wake-body interaction. A rod and an airfoil are immersed upstream of the airfoil. In this paper, we reviewed the noise mechanism generated by the wake-body interaction and show the numerical results obtained by the coupling method using commercial CFD and acoustic BEM codes. The results shows that depending on the spacing between the rod or airfoil and the airfoil, the flow patterns and noise radiation vary. With small spacing, the vortex shedding from the upstream obstacle is suppressed and it results in the suppression of the sound generation. With large spacing, the shear layer or the vortices shed from the upstream obstacle impinge on the downstream obstacle and it results in the large sound generation. The dominant peak frequency of the generated sound varies with increasing of the spacing between the two obstacles.

scholarly journals Wake-Body Interaction Noise Simulated by the Coupling Method Using CFD and BEM

2020 ◽  
Author(s):  
Masaaki Mori
Keyword(s):  
Heat Exchanger ◽  
Vortex Shedding ◽  
Peak Frequency ◽  
Flow Patterns ◽  
Coupling Method ◽  
Sound Generation ◽  
Engineering Applications ◽  
Rotating Blades ◽  
Body Interaction ◽  
Dominant Peak

In many engineering applications, obstacles often appear in the wake of obstacles. Vortices shed from an upstream obstacle interact with downstream obstacle and generate noise, for example blades in a turbomachinery, tubes in a heat exchanger, rotating blades like a helicopter and wind turbine and so on. This phenomenon is called wake-body interaction or body-vortex interaction (BVI). The rod-airfoil and airfoil-airfoil configurations are typical models for the wake-body interaction. A rod and an airfoil are immersed upstream of the airfoil. In this chapter, we review the noise mechanism generated by the wake-body interaction and show the numerical results obtained by the coupling method using commercial CFD and acoustic BEM codes. The results show that depending on the spacing between the rod or airfoil and the airfoil, the flow patterns and noise radiation vary. With small spacing, the vortex shedding from the upstream obstacle is suppressed and it results in the suppression of the sound generation. With large spacing, the shear layer or the vortices shed from the upstream obstacle impinge on the downstream obstacle and it results in the large sound generation. The dominant peak frequency of the generated sound varies with increase in the spacing between the two obstacles.

Study on Evaluation of Sound Speed in Duct With Tube Banks

2010 ◽  
Author(s):  
Kunihiko Ishihara
Keyword(s):  
Heat Exchanger ◽  
Resonance Frequency ◽  
Vortex Shedding ◽  
Sound Speed ◽  
Flow Direction ◽  
Fem Analysis ◽  
The Self ◽  
Resonance Phenomenon ◽  
Acoustic Characteristics ◽  
Tube Banks

As tube banks are set in a duct in a boiler and a heat exchanger, the resonance phenomenon or the self sustained tone are generated due to the interference between vortex shedding and the acoustic characteristics of the duct. It is necessary to know the resonance frequency of the duct, namely sound speed, for avoiding any trouble that may arise. In general, it is said that the sound speed decreases in the duct with tube banks and an evaluation formula is given. However, this formula is often used for the perpendicular direction of the flow. We wanted to know whether this formula would be able to be used for the flow direction and for various arrays of patterns or not. In this paper, the applicability of this expression is discussed by using FEM analysis and experiments.

Planar Blast/Vortex Interaction and Sound Generation

AIAA Journal ◽  
2002 ◽  
Vol 40 (11) ◽  
pp. 2298-2304 ◽  
Author(s):  
H. Chen ◽  
S. M. Liang
Keyword(s):  
Vortex Interaction ◽  
Sound Generation

Infants' Reactions to Visual Movement of the Environment

Perception ◽  
1989 ◽  
Vol 18 (5) ◽  
pp. 667-673 ◽  
Author(s):  
André Delorme ◽  
Jean-Yves Frigon ◽  
Carole Lagacé
Keyword(s):  
Fourier Transforms ◽  
Force Measurement ◽  
Peak Frequency ◽  
Visual Environment ◽  
Postural Reactions ◽  
Anteroposterior Axis ◽  
Leading Role ◽  
Young Infants ◽  
Stationary Conditions ◽  
Dominant Peak

It has been demonstrated many times that the posture of infants is affected by movement of the visual environment. However, in previous studies, measurements taken with infants less than 10 to 12 months of age have always been recorded with the infants in a sitting position. An experiment is reported in which the postural reactions to a sinusoidal movement of the visual environment were recorded in infants 7 months of age and older standing with support. Fifty subjects divided into five groups (mean age 7.15 to 48.6 months) participated in the experiment. The groups differed in age and motor ability. Movement of the visual environment was achieved by means of a floorless room that could be moved sinusoidally in the anteroposterior axis. The subjects had to stand holding a horizontal bar fixed to a force-measurement platform. For each subject, measurements were made during four 60 s intervals: two with movement of the room and two with the room stationary. For all groups, reactions in the anteroposterior axis were stronger than in the lateral axis and this was true for both stimulus conditions. Comparison of the differences between the movement and stationary conditions in the anteroposterior axis, as a function of age, shows that the youngest infants seemed paradoxically to give stronger reactions when the room was stationary than when it was moving; the inverse was true for older infants and this difference increased with age. An analysis of the data with fast Fourier transforms reveals that the majority of subjects showed a pattern of postural reactions where the dominant (peak) frequency was identical to the peak frequency of room movement. The results of the present experiment lead to the conclusion that young infants react posturally to movements of their visual environment as soon as they are able to stand without help. Also, the best synchronization is found in infants that have just learned to stand without help. These results confirm that ‘visual proprioception’ assumes a leading role in the learning of a new stance.

Multiphase Sloshing and Interfacial Wave Interaction With a Baffle and a Submersed Block

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Obai Kargbo ◽  
Mi-An Xue ◽  
Jinhai Zheng
Keyword(s):  
Free Surface ◽  
Interfacial Layer ◽  
Fluid Velocity ◽  
Wave Interaction ◽  
Peak Frequency ◽  
Arbitrary Lagrangian Eulerian ◽  
Interfacial Wave ◽  
Arbitrary Lagrangian Eulerian Method ◽  
Fluid Layers ◽  
Dominant Peak

A numerical model of a rectangular tank containing a layered liquid is modeled for studying layered sloshing wave. The Arbitrary Lagrangian Eulerian method is used to track the development for both the interfacial and free surface of the fluid domain. A series of cases are simulated for baffled and unbaffled sloshing with various excitation frequencies and various baffle configurations. A case containing a submerged block is also simulated to observe the interfacial wave interaction with the block structure and to observe how the position and size of the block affect the interfacial wave in a fluid. Velocity screenshots are analyzed for observing the velocity distribution in the layers and to observe the behavior of the interfacial layer for baffled and unbaffled tank cases. A fast Fourier transform spectral analysis of the layered liquid sloshing time series for both the interfacial layer and free surface layer is presented to observe the energy in the fluid layers as well as to observe the dominant peak frequency for both the layers.

Sign in / Sign up

Export Citation Format

Share Document