PRACTICAL METHODS OF ACOUSTIC MATERIALS PATTERNING FOR INCREASE OF THEIR EFFECTIVENESS

Akustika ◽  
2021 ◽  
pp. 107-111
Author(s):  
Aleksandr Krasnov ◽  
Igor Deryabin
Keyword(s):  
Noise Reduction ◽  
Laboratory Scale ◽  
Experimental Investigations ◽  
Passenger Cars

This article includes the results of experimental investigations of patterned noise-reducing materials and components, carried out using special-purpose laboratory-scale bench plants (Alpha Cabin, Torre di Pisa, RTC-3, Oberst). Illustrative examples of constructive-technological structurization of the components (gaskets, panels and upholstery) providing noise reduction of passenger cars are given.

Application of compact silencers as a noise barrier to a naturally ventilated double-skin façade

2021 ◽  
Vol 69 (3) ◽  
pp. 220-228
Author(s):  
Jeehwan Lee ◽  
Jae D. Chang ◽  
Robert Coffeen
Keyword(s):  
Noise Reduction ◽  
Surface Area ◽  
Natural Ventilation ◽  
Experimental Investigations ◽  
Test Case ◽  
Open Surface ◽  
Low Frequencies ◽  
Noise Barrier ◽  
Double Skin ◽  
Air Vent

A prior study of the acoustical performance of a double-skin facade (DSF) as a noise barrier was carried out based on the percentage of the air vent open surface area, shading louver configurations, and shading louver surface materials. Earlier research findings led to experimental investigations of the acoustical performance capabilities of compact silencers to replace DSF air vents as both noise barriers and air channels because DSF air cavities, which contribute to natural ventilation performance (e.g., wind-driven or buoyancy-driven performance), are acoustically vulnerable to noise transmitted through the air vents. This experimental investigation aims to explore noise reduction (NR) through compact silencers applied to DSF air vents. Double-skin facade mock-up test cases were designed based on three test scenarios of a ventilation open surface area: (1) a 100%air vent open surface area (open mode), (2) a 0% air vent open surface area (closed mode), and (3) a compact silencer. From a data analysis of DSF mock-up test results, the overall NR values of a DSFmock-up ranged from20 to 37 dB(A) depending on the number of compact silencers and the shading louver orientation used. Configurations of compact silencers and shading louvers helped the DSF mock-up achieve additionalNR values of 5 to 10 dB(A) depending on the test case. Moreover, applying compact silencers to a naturally ventilated DSF mock-up led to significant noise reduction at low frequencies (125Hz).

scholarly journals Numerical Assessment of Similitude Parameters and Dimensional Analysis for Water Entry Problems

2015 ◽  
Vol 2015 ◽  
pp. 1-15 ◽  
Author(s):  
Andrea L. Facci ◽  
Stefano Ubertini
Keyword(s):  
Numerical Study ◽  
Computational Study ◽  
Water Entry ◽  
Laboratory Scale ◽  
Analytical Models ◽  
Experimental Investigations ◽  
Two Dimensional ◽  
Wide Range ◽  
Entry Velocity ◽  
Real Size

The prediction of impulsive loads deriving from the sudden impact of a solid body on the water surface is of fundamental importance for a wide range of engineering applications. The study of hull-slamming phenomena largely relies on laboratory scale experimental investigations and on simplified analytical models. The aim of this paper is to quantitatively assess the interplay between the relevant nondimensional parameters for the water entry of a two-dimensional body, evidencing the similitude conditions that allow the transition from scaled experiments to real size applications. This assessment is performed through the numerical study of the hydrodynamics induced by the water impact of a two-dimensional wedge. The fluid flow is considered incompressible. First of all numerical simulations are validated by comparison with experimental data from the literature and with the Wagner seminal theory. Afterwards, a thorough computational study is performed by systematically varying all the relevant parameters, such as the nondimensional entry velocity and acceleration. We conclude by evidencing some design prescriptions that should be adopted in order to facilitate the transition of laboratory scale experiments to real scale applications.

Investigation of the Cooling and Underbody Flow Field on a Detailed Scale Model Passenger Car: Part 2—Effect of Ground Simulation

2009 ◽  
Author(s):  
Christoffer Landstro¨m ◽  
Lasse Christoffersen ◽  
Lennart Lo¨fdahl
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Aerodynamic Drag ◽  
Scale Model ◽  
Experimental Investigations ◽  
Passenger Cars ◽  
Local Flow ◽  
Passenger Car ◽  
Reynolds Number Effects ◽  
Cooling Air

Future demands on passenger cars consist to a large extend of making them more energy efficient. Reducing the driving resistance by reducing the aerodynamic drag will be one important part in reducing fuel consumption. In most cases during passenger car development, early experimental investigations are performed in scale model wind tunnels. Considering that such models inevitably suffer from Reynolds number effects it is important to understand how this affects the test results. Investigations of the aerodynamics of a detailed scale model Volvo S60 have been performed in the aerodynamic wind tunnel at Chalmers University of Technology. The investigation aimed at increasing the understanding of how the flow field in scale model testing is affected by ground simulation and different cooling air flow configurations at different Reynolds numbers. A full width moving ground system was used in the experiments. Pressure taps were distributed between the cooling air inlets, the underbody and the vehicle base. An internal six component balance was used to measure global forces and moments. By combining the results from the measurements it was possible to increase the understanding of some of the local flow features. Results showed significant Reynolds number effects both with stationary ground as well as moving ground and rotating wheels. Global aerodynamic drag as well as front and rear axle lift was found to be affected.

scholarly journals Prediction of noise from serrated trailing edges

2016 ◽  
Vol 793 ◽  
pp. 556-588 ◽  
Author(s):  
B. Lyu ◽  
M. Azarpeyvand ◽  
S. Sinayoko
Keyword(s):  
Noise Reduction ◽  
Analytical Model ◽  
Leading Edge ◽  
Experimental Investigations ◽  
Destructive Interference ◽  
Trailing Edge ◽  
Trailing Edges ◽  
Mach Numbers ◽  
Trailing Edge Serrations ◽  
High Mach

A new analytical model is developed for the prediction of noise from serrated trailing edges. The model generalizes Amiet’s trailing-edge noise theory to sawtooth trailing edges, resulting in a complicated partial differential equation. The equation is then solved by means of a Fourier expansion technique combined with an iterative procedure. The solution is validated through comparison with the finite element method for a variety of serrations at different Mach numbers. The results obtained using the new model predict noise reduction of up to 10 dB at 90$^{\circ }$ above the trailing edge, which is more realistic than predictions based on Howe’s model and also more consistent with experimental observations. A thorough analytical and numerical analysis of the physical mechanism is carried out and suggests that the noise reduction due to serration originates primarily from interference effects near the trailing edge. A closer inspection of the proposed mathematical model has led to the development of two criteria for the effectiveness of the trailing-edge serrations, consistent but more general than those proposed by Howe. While experimental investigations often focus on noise reduction at 90$^{\circ }$ above the trailing edge, the new analytical model shows that the destructive interference scattering effects due to the serrations cause significant noise reduction at large polar angles, near the leading edge. It has also been observed that serrations can significantly change the directivity characteristics of the aerofoil at high frequencies and even lead to noise increase at high Mach numbers.

A Hooped Pelton Runner: FE Analysis and Experimentation

2011 ◽  
Author(s):  
Gaurangkumar C. Chaudhari ◽  
Samip P. Shah ◽  
S. A. Channiwala
Keyword(s):  
Stress Analysis ◽  
Work Stress ◽  
Fe Analysis ◽  
Design Concept ◽  
Laboratory Scale ◽  
Experimental Investigations ◽  
Analysis And Design ◽  
Mechanical Aspect

In the present work, stress analysis of traditional Pelton runner and hooped Pelton runner using FEA software ANSYS has been carried out. These results confirm the reduction of stresses in the Hooped Pelton Runner compared to Traditional Pelton Runner and the mechanical aspect as well as the results of the hydraulic comparison between traditional runners and hooped runners is made. An actual laboratory scale hoop runner based on this analysis and design is developed and the detailed experimental investigations are also carried out to prove the worthiness of this new design concept.

Influence of Microjet Condition on Characteristics of Supersonic Jet Noise and Flow Field

2012 ◽  
Author(s):  
Ryuichi Okada ◽  
Toshinori Watanabe ◽  
Seiji Uzawa ◽  
Takehiro Himeno ◽  
Tsutomu Oishi
Keyword(s):  
Flow Field ◽  
Noise Reduction ◽  
High Speed ◽  
Supersonic Jet ◽  
Jet Noise ◽  
Experimental Investigations ◽  
Acoustic Measurements ◽  
Supersonic Transport ◽  
Supersonic Jet Noise ◽  
Supersonic Aircraft

Jet noise reduction is essential for environmentally-friendly civil transport. Since jet noise becomes very intense in the case of supersonic aircraft, noise reduction is crucial topic for the realization of next-generation supersonic transport. In the present study, experimental investigations were performed to clarify the effect of microjet injection on supersonic jet noise and flow field. The experiments were focused on supersonic jet with Mach number up to 1.47, which was generated from a rectangular nozzle with high aspect ratio. Far-field acoustic measurements were conducted for widely ranged microjet conditions to understand the influence of the condition on characteristics of supersonic jet noise and flow field. For understanding the unsteady behavior of the flow field and the relation with noise reduction, flow field visualization was performed with schlieren technique using a high-speed camera.

Experimental investigation of porous materials for trailing-edge noise reduction

2020 ◽  
Vol 19 (6-8) ◽  
pp. 365-384
Author(s):  
K-S Rossignol ◽  
A Suryadi ◽  
M Herr ◽  
J Schmidt ◽  
J Tychsen
Keyword(s):  
Wind Tunnel ◽  
Noise Reduction ◽  
Porous Materials ◽  
Active Flow Control ◽  
Acoustic Emissions ◽  
Experimental Investigations ◽  
Trailing Edge ◽  
Trailing Edge Noise ◽  
Tunnel Model ◽  
Close Proximity

The introduction of quiet short take-off and landing for civil aircraft operations in close proximity to the population poses important technological challenges. One critical aspect is the realization of extreme lift augmentation at low acoustic emissions. The aircraft concept selected to achieve this goal is a high-lift system equipped with an active flow-control non-slotted flap and a droop nose. For this specific configuration, trailing edge noise becomes a dominant noise source. Porous materials as a passive means for trailing-edge noise reduction are selected and characterized. Results of extensive experimental investigations in the acoustic wind tunnel Braunschweig are presented and discussed to point out the potential and limitations of the selected porous devices. Practical issues related to material manufacturing and integration into the wind tunnel model are addressed. The noise reduction potential of passive porous trailing-edge devices is found to strongly depend on both these aspects. Issues related to the characterization of the porous materials properties are described. Although porous materials are found to be successful at reducing trailing-edge noise emissions, the results indicate that there is still a need for more generic investigations to further clarify the parametric dependencies between noise reduction and material properties.

Experimental investigations of coaxial injectors in a laboratory-scale rocket combustor

2016 ◽  
Vol 59 ◽  
pp. 41-51 ◽  
Author(s):  
Jian Dai ◽  
GuoBiao Cai ◽  
Yang Zhang ◽  
NanJia Yu
Keyword(s):  
Laboratory Scale ◽  
Experimental Investigations
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