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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 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.
3
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.
4
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.
5
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.
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