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    Wyświetlanie 1-5 z 5
    Tytuł:
    Airfoil Tonal Noise Prediction Using Urans
    Autorzy:
    Klimczyk, Witold
    Sieradzki, Adam
    Powiązania:
    https://bibliotekanauki.pl/articles/36829323.pdf
    Data publikacji:
    2023
    Wydawca:
    Sieć Badawcza Łukasiewicz - Instytut Lotnictwa
    Tematy:
    airfoil tonal noise
    aeroacoustics
    CFD
    Opis:
    To examine the feasibility of the laminar boundary layer (LBL), vortex shedding (VS) tonal noise modelling using unsteady Reynolds-averaged Navier-Stokes (URANS) was investigated for the non-symmetric S834 airfoil. A transition SST turbulence model was used to model the laminar-turbulent transition and its vital influence on the laminar bubble and hydrodynamic instabilities generation. The influence of turbulence on the unsteady vortex patterns was investigated. Hence, the hybrid aeroacoustic analysis with Lighthill analogy was conducted to obtain the acoustic pressure field. The approach allowed us to model hydrodynamic instabilities and the resulting VS tonal noise. The frequency of VS matched the experimental data, giving the same 1/3 octave tonal peak only for a limited freestream turbulence regime. The simplification of the present method did not allow us to model the aeroacoustic feedback loop, and resulted in lack of instabilities for higher freestream turbulence.
    Źródło:
    Transactions on Aerospace Research; 2023, 4 (273); 1-17
    0509-6669
    2545-2835
    Pojawia się w:
    Transactions on Aerospace Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Evaluating an 80 Hz tonal noise from a hydropower plant
    Autorzy:
    Wallner, Peter
    Hutter, Hans-Peter
    Moshammer, Hanns
    Powiązania:
    https://bibliotekanauki.pl/articles/2161973.pdf
    Data publikacji:
    2019-06-14
    Wydawca:
    Instytut Medycyny Pracy im. prof. dra Jerzego Nofera w Łodzi
    Tematy:
    tonal noise
    hydropower plant
    noise annoyance
    public health evaluation
    community-based prevention
    low frequency noise
    Opis:
    A pumped storage power plant produces significant noise such that adjacent areas were deemed uninhabitable for the local population. In recent years, the population in the area has increased, and the noise levels are now causing significant distress to the local population. The company operating the power plant and a citizens’ initiative have both commissioned noise measurements. The measurements showed that the continuous pump noise was audible over many kilometers. The A-weighted sound-pressure level of 50 dBA at the next residential area underestimates the perceived noise, given the clear tonal nature in the low frequency range. Interviews of the exposed population, together with detailed “annoyance diaries” by a sample of the residents, proved their high level of annoyance. Their reported observations on distress and sleep disturbances coincide with the time course of the pumping operation. The pumping noise leads to annoyance in a large area, and to considerable nuisance in a smaller one. For the most exposed homes, long-term exposure might be considered a health hazard due to stress and disturbances in sleep quality. Therefore, the operator committed to developing a technical noise control plan. This case shows that a scientific approach within a complex environmental noise problem can foster an agreement about noise protection measures. However, this can only be successful if all involved parties participate in the process. Pilot studies are underway to test the impact of damping material layers on the pipes, the housing of the pipes, and the kind of air vessel solutions between the pumps and the pipes. Int J Occup Med Environ Health. 2019;32(3):401–11
    Źródło:
    International Journal of Occupational Medicine and Environmental Health; 2019, 32, 3; 401-411
    1232-1087
    1896-494X
    Pojawia się w:
    International Journal of Occupational Medicine and Environmental Health
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical Prediction of the Tonal Airborne Noise for a NACA 0012 Aerofoil at Moderate Reynolds Number Using a Transitional URANS Approach
    Autorzy:
    De Gennaro, M.
    Küehnelt, H.
    Zanon, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/178116.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    tonal airborne noise
    NACA 0012
    Laminar Boundary Layer-Vortex Shedding noise
    Ladder-like tonal structure of the acoustic spectrum
    multi-tonal structure of the acoustic spectrum
    Opis:
    Tonal airborne noise of aerofoils appears in a limited range of moderate Reynolds numbers and angles of attack. In these specific conditions, the aerofoil is characterised by a large region of laminar flow over the aerodynamic surface, typically resulting in two-dimensional laminar instabilities in the boundary layer, generating one or more acoustic tones. The numerical simulation of such phenomenon requires, beside an accurate prediction of the unsteady flow field, a proper modelling of the laminar to turbulent transition of the boundary layer, which generally imposes the use of highly CPU demanding approaches such as large eddy simulation (LES) or direct numerical simulation (DNS). This paper aims at presenting the results of numerical experiments for evaluating the capability of capturing the tonal airborne noise by using an advanced, yet low computationally demanding, unsteady Reynolds-averaged Navier-Stokes (URANS) turbulence model augmented with a transitional model to account for the laminar to turbulent transition. This approach, coupled with the Ffowcs Williams and Hawkings (FW-H) acoustic analogy, is adopted for predicting the far-field acoustic sound pressure of a NACA 0012 aerofoil with Reynolds number ranging from 0.39 · 106 to 1.09 · 106. The results show a main tone located approximately at 1.6–1.8 kHz for a Reynolds number equal to 0.62 · 106, increasing to 2.4 kHz at Reynolds number equal to 0.85 · 106 and 3.4 kHz at 1.09 · 106, while no main tones are observed at 0.39 · 106. The computed spectra confirm that the acoustic emission of the aerofoil is dominated by tonal structures and that the frequency of the main tone depends on the Reynolds number consistently with the ladder-like tonal structure suggested by Paterson et al. Moreover, in specific conditions, the acoustic spectra exhibit a multi-tonal structure visible in narrowband spectra, in line with the findings of Arbey and Bataille. The presented results demonstrate the capability of the numerical model of predicting the physics of the tonal airborne noise generation.
    Źródło:
    Archives of Acoustics; 2017, 42, 4; 653-675
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical simulation of tonal and broadband hydrodynamic noises of noncavitating underwater propeller
    Autorzy:
    Kheradmand, S.
    Rahrovi, A.
    Mousavi, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/259022.pdf
    Data publikacji:
    2014
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    Numerical Simulation
    tonal
    broadband
    Hydrodynamic Noise
    Propeller
    Opis:
    The objective of the study was to carry out numerical simulation of the hydrodynamic noise generated by the flow around a non-cavitating underwater propeller. To achieve this goal, hydrodynamic simulation of flow around the propeller was initially done. The unsteady 3-D flow was modelled numerically along with the LES turbulence model. The hydrodynamic parameters calculated for different advance coefficients are visibly in line with the previous experimental works. The turbulent quantities of the hydrodynamic study and the FWH model were used to find spectral distributions of flow noise for different advance coefficients. The results of the acoustic investigation were compared against other numerical results. An array of 100 hydrophones was used to find the directional distribution of the noise around the propeller. The obtained results indicate that, for different advance coefficients, the highest intensity of the noise recorded by different receivers around the propeller occurs in BPF. Furthermore, it has been found that the noise is directionally as well as intensively distributed around the propeller. Noise distributions of noise are presented and discussed for different regimes of propeller rotation. The analysis of the expanded spectrum (broadband analysis) of noise on the propellers has also been done and the contribution of all parts of the propeller to hydrodynamic noise generation are presented.
    Źródło:
    Polish Maritime Research; 2014, 3; 46-53
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Active Cancellation of the Tonal Component of Sound Using a Discrete Fourier Transform of Variable Length
    Autorzy:
    Łuczyński, Michał
    Dobrucki, Andrzej
    Brachmański, Stefan
    Powiązania:
    https://bibliotekanauki.pl/articles/2097702.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    active noise control
    tonal signal
    Discrete Fourier Transform
    Opis:
    The paper presents a method of eliminating the tonal component of an acoustic signal. The tonal component is approximated by a sinusoidal signal of a given amplitude and frequency. As the parameters of this component: amplitude, frequency and initial phase may be variable, it is important to detect these parameters in subsequent analysis time intervals (frames). If the detection of the parameters is correct, the elimination consists in adding a sinusoidal component with the detected amplitude and frequency to the signal, but the phase shifted by 180 degrees. The accuracy of the reduction depends on the accuracy of parameters detection and their changes. Detection takes place using the Discrete Fourier Transform, whose length is changed to match the spectrum resolution to the signal frequency. The operation for various methods of synthesis of the compensating signal as well as various window functions were checked. An elimination simulation was performed to analyze the effectiveness of the reduction. The result of the paper is the assessment of the method in narrowband active noise control systems. The method was tested by simulation and then experimentally with real acoustic signals. The level of reduction was from 6.9 to 31.5 dB.
    Źródło:
    Archives of Acoustics; 2021, 46, 4; 579-589
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-5 z 5

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