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1
Content available Numerical analysis of sound propagation in selected acoustical system with helicoidal resonator placed in cylindrical duct with 90 degree elbow
Łapka W.
Vibrations in Physical Systems
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2018
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Vol. 29
art. no. 2018018
EN
This paper concerns to the numerical analysis of transmission loss of selected acoustical helicoidal resonator placed in cylindrical duct close to the elbow. The change of acoustic attenuation performance of helicoidal resonator is observed with the change of the degree of rotation of cylindrical duct elbow. The finite element method was used to calculate the acoustical system in the COMSOL Multiphysics computational environment. The results show that the change of rotation of elbow or rotation of helicoidal profile can change the resonance frequency, and thus the tuning options are extended when applying helicoidal resonators in ducted systems.
2
Content available Numerical Study of Acoustic-Structure Interaction of Selected Helicoidal Resonator with Flexible Helicoidal Profile
Łapka W.
Archives of Acoustics
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2018
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Vol. 43, No. 1
83--92
EN
The paper presents the results of numerical studies of acoustic-structure interaction of selected helicoidal resonator with helicoidal profile made of an elastic material. Considered a well-recognized acoustic system for one representative type of acoustic helicoidal resonator with two resonant frequencies that correspond to previous studies of the author. Due to the large range of flexible materials to study, this work focuses on the change of material density, Poisson’s ratio and Young’s modulus as the basic parameters describing the properties of elastic materials. The results indicate a significant interaction between the acoustic attenuation performance of helicoidal resonator and elasticity of the helicoidal profile. These interactions are most evident in the frequency range in which the helicoidal resonator is revealed to be effective acoustic damper.
3
Content available Numerical analysis of pressure drop and acoustic attenuation performance of two helicoidal resonators arranged in parallel ducts with different rotation angles
Łapka W.
Vibrations in Physical Systems
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2016
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Vol. 27
237--244
EN
The paper presents a numerical analysis of pressure drop and acoustic attenuation performance (transmission loss) of two identical acoustic helicoidal resonators arranged in parallel ducts with different rotation angles. The air stream is divided from one cylindrical duct of a diameter D=140mm to a two parallel cylindrical ducts of diameter d=125mm with two helicoidal resonators inside – one per one duct. The ratio of helicoidal pitch s of helicoidal resonators to a cylindrical duct diameter d equals s/d=1,976. Other geometrical relationships of helicoidal resonators, as a mandrel diameter dm to duct diameter ratio dm/d=0.024, thickness g of helicoidal profile g/d=0.0024, and the number of helicoidal turn n=0,695 for both resonators. The investigated range of rotation angles covered the three characteristic positions of helicoidal resonators gaps, when considering the air stream distribution from central large duct with diameter D. The value of normal inflow velocity v[m/s] equaled 1 for all investigated cases.
4
Content available Transmission loss and pressure drop of selected range of helicoidal resonators
Łapka W.
Vibrations in Physical Systems
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2014
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Vol. 26
121--128
EN
The paper presents the numerical analysis of transmission loss and pressure drop of acoustic helicoidal resonators with constant pitch to cylindrical duct diameter ratio and different number of helicoidal turns n. The ducted system consists of a straight cylindrical duct of constant diameter d=0.125m. The ratio of helicoidal pitch s to cylindrical duct diameter d equals s/d=1,976. Other geometrical relationships of helicoidal resonator, as a mandrel diameter dm to duct diameter ratio dm/d=0.024 and thickness g of helicoidal profile g/d=0.0024, were constant as well. The investigated range of numbers of helicoidal turns n was analyzed in the range from 0 to 2.0 for transmission loss parameter and from 0 to 1.0 for pressure drop. The values of normal inflow velocity v [m/s] equals 1, 5, 10, 15 and 20.
5
Content available remote Numerical aeroacoustic research of transmission loss characteristics change of selected helicoidal resonators due to different air flow velocities
Łapka W.
Vibrations in Physical Systems
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2012
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Vol. 25
267--272
EN
This paper presents the results of aeroacoustic numerical simulations for three types of helicoidal resonators placed inside straight cylindrical duct. The same ratio s/d = 1.976 is considered for three numbers of helicoidal turns n = 0.671, n = 0.695 and n = 1.0. Also three types of transmission loss characteristics are represented. Three-dimensional models were calculated by the use of a finite element method in Comsol Multiphysics Acoustics Module – Aeroacoustics with flow, Frequency Domain. The change of transmission loss characteristics of helicoidal resonators is presented for different air flow velocities in the range from 1 m/s to 20 m/s for cylindrical duct of diameter d = 0.125m.
6
Content available remote Substitutional transmittance function of helicoidal resonator
Łapka W.
Vibrations in Physical Systems
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2010
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Vol. 24
265--270
EN
An analytical and computational characteristics of transmission losses of the helicoidal resonator are compared in this paper. The substitutional transmittance function of helicoidal resonator was proposed based on amplitude characteristic of electrical band-stopfilter. At first approach the analytical model can be considered as valid for practical silencing systems design calculations in ducted systems.
PL
W niniejszym artykule dokonano porównania charakterystyk tłumienia przenoszenia rezonatora helikoidalnego uzyskanych na drodze obliczeń analitycznych i numerycznych. Zaproponowana została zastępcza funkcja transmitancji rezonatora helikoidalnego na podstawie charakterystyki amplitudowej elektrycznego filtru pasmowo-zaporowego. Tak wykonany analityczny model transmitancji w pierwszym przybliżeniu może być uznany za poprawny dla celów obliczeniowych praktycznego projektowania systemów wyciszeniowych w instalacjach kanałowych.
7
Content available remote Insertion Loss of Spiral Ducts - Measurements and Computations
Łapka W.
Archives of Acoustics
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2009
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Vol. 34, No. 4
537-545
EN
This work presents measured and computed characteristics of insertion loss (IL) of spiral ducts. Numerical and experimental models of spiral ducts have been investigated. For the numerical modeling, a three dimensional model computed by the use of a finite element method in a COMSOL Multiphysics computer application has been used. For the experimental modeling, there has been made a spiral duct model by using a three dimensional rapid prototyping technique. An acoustic system with a round silencer has been ivestigated, and the spiral duct has been inserted at the inlet. IL is considered in this paper as the difference between the sound pressure level (SPL) [dB] probed at only one outlet point of the acoustic system without and with an acoustical filter (spiral duct), respectively. The results of measured and computed IL of spiral ducts presented in this paper confirm the fact that this newly discovered technical solution for attenuating sound in ducted systems has an applicable potential. There are visible small discrepancies between the measurements and computations. The results can differ due to the non ideal dimensions of the experimental model and the non ideal inlet and outlet surroundings of the experimental acoustic system. However, the IL characteristics of the computed model is almost wholly covered by the IL characteristics of the measured model.
8
Content available remote Acoustic attenuation performance of Helmholtz resonator and spiral duct
Łapka W., Cempel C.
Vibrations in Physical Systems
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2008
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Vol. 23
247--252
EN
This work examines a comparison of acoustic attenuation performance of well known Helmholtz resonator and spiral element inserted into circular duct, which creates spiral duct. The paper consists results of numerical computations by the use of Finite Element Method. Here the spiral is a kind of resonant element, which can be applied in circular ducts, mainly for low speed velocity ducts e.g. ventilation, air-conditioning and heat systems. Results are presented as a transmission loss. The sound attenuation performances of Helmholtz resonator and spiral duct depend on their geometrical relationships. The most important observation is that the sound attenuation in both solutions are based on similar phisical phenomenon – resonance.
9
Content available Noise Reduction of Spiral Ducts
Łapka W., Cempel C.
International Journal of Occupational Safety and Ergonomics
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2007
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Vol. 13, No. 4
419--426
EN
The paper presents noise reduction (NR) of spiral ducts as a result of computational modeling of acoustic wave propagation. Three-dimensional models were created with the finite element method in COMSOL Multiphysics version 3.3. Nine models of spiral ducts with 1–9 spiral leads were considered. Time-harmonic analysis was used to predict NR, which was shown in spectral and interval frequency bands. Spiral duct performance can be seen as a comparison of NR before and after a change from a circular to a spiral duct.
10
Content available remote Principle of approximate superposition in designing acoustic mufflers
Łapka W., Parnasow W., Cempel C.
Vibrations in Physical Systems
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2006
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Vol. 22
237--242
11
Content available Diagnoza hałasu środowiska gminy Murowana Goślina
Golec Z., Golec M., Łapka W.
Diagnostyka
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2004
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Vol. 30, T. 1
191--195
PL
Praca zawiera ocenę klimatu akustycznego regionu Murowana Goślina. Ocenie podlegał hałas przy drodze wojewódzkiej nr196 i przy ulicy Tadeusza Kutrzeby oraz hałas przemysłowy na gra-nicy Wielkopolskich Zakładów Farmaceutycznych BIOWIN i zakładu hodowli drobiu w Przebę-dowie. Wyniki badań hałasu odniesiono do obowiązujących dopuszczalnych i progowych wartości poz.iomów hałasu w środowisku dla pory dziennej i nocnej. Pokazano, że najbardziej uciążliwym źródłem hałasu w analizowanym obszarze jest hałas przy drodze wojewódzkiej nr 196, która prze-biega przez centrum miasta. Wyniki przeprowadzonej analizy hałasu wskazują na potrzebę podję-cia działań w zakresie ochrony środowiska Murowana Goślina przed hałasem drogowym.
EN
The work includes assessment of an acoustic climate in the Murowana Goślina region. The road noise level was assessed at the Provincial Road No 196 and in Tadeusz Kutrzeba Street, while industrial noise was estimated at the border between BIOWIN Pharmaceutical Plant of Wielkopol-ska and the Poultry Farming Plant in Przebędowo. Results of the noise survey were compared with binding admissible and threshold values of the noise levels in the environment at day and night time. It was shown that the most burdensome noise in the area subject to the study is generated in the Provincial Road No 196 crossing the centre of the town. The results of the noise analysis indi-cate the need for protecting the Murowana Goślina environment from the road noise.
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