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1

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.

2

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.

3

Perturbation methods applied to the helical flow of a Casson fluid

Chiera C., Connell H. J., Shepherd J. J.

International Journal of Applied Mechanics and Engineering

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2005

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Vol. 10, no 1

39-51

EN

The helical flow of a Casson fluid between infinitely long coaxial cylinders is analyzed, when the inner cylinder has a given constant angular velocity, and a constant axial flow rate is imposed. Perturbation methods are applied in two circumstances of physical interest - that of low axial flow rates; and that of small intercylindrical gap width - to yield approximate expressions describing the fluid velocity field; and the Reiner-Riwlin equation, the fundamental relationship linking the angular velocity of the inner cylinder, the torque experienced there, and the given axial flow rate. The accuracy of these expressions is tested by comparison with solutions generated using numerical computation.

4

Investigation of a laminar flow of a non-Netonian fluid in a helical pipe

Cheng L., Kuznetsov A. V.

International Journal of Applied Mechanics and Engineering

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2005

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Vol. 10, no 1

21-37

EN

This paper presents a numerical study of a fully developed laminar flow of a non-Newtonian fluid in a helical pipe. An orthogonal helical coordinate system is utilized and the Navier-Stokes equations for the non-Newtonian fluid in this coordinate system are derived. The SIMPLE algorithm with a staggered grid is adopted to solve the governing equations. The effects of the pressure gradient, the curvature, and the torsion on the fully developed laminar flow in helical pipes are investigated. The comparison of flow dynamics between Newtonian and non-Newtonian fluids is presented.