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Influence of the elastic cavity walls on cavity flow noise

Łojek Paweł, Czajka Ireneusz, Gołaś Andrzej, Suder-Dębska Katarzyna

Vibrations in Physical Systems

2021

Vol. 32, nr 1

art. no. 2021109

In this study, computational fluid dynamics and computational aeroacoustics methods were used to investigate the influence of the elastic cavity walls on the noise generated by the flow over rectangular cavity. Two cases were considered and compared, one with rigid cavity walls, and one with elastic walls. In the latter case, the movement of the walls were solved by finite element modelling and coupled with CFD simulations. The noise generated by the flow over cavity was computed using Ffowcs Williams & Hawkings acoustic analogy. The increase of the sound pressure level for elastic walls case at frequency range of 1 kHz to 10 kHz is observed, compared to the rigid walls case.

Finite Element Modelling of a Flow-Acoustic Coupling in Unbounded Domains

Łojek Paweł, Czajka Ireneusz, Gołaś Andrzej

Archives of Acoustics

2020

Vol. 45, No. 4

633--645

One of the main issues of design process of HVAC systems and ventilation ducts in particular is correct modelling of coupling of the flow field and acoustic field of the air flowing in such systems. Such a coupling can be modelled in many ways, one of them is using linearised Euler equations (LEE). In this paper, the method of solving these equations using finite element method and open source tools is decribed. Equations were transformed into functional and solved using Python language and FEniCS software. The non-reflective boundary condition called buffer layer was also implemented into equations, which allowed modelling of unbounded domains. The issue, influence of flow on wave propagation, could be adressed using LEE equations, as they take non-uniform mean flow into account. The developed tool was verified and results of simulations were compared with analytical solutions, both in one- and two-dimensional cases. The obtained numerical results are very consistent with analytical ones. Furthermore, this paper describes the use of the developed tool for analysing a more complex model. Acoustic wave propagation for the backward-facing step in the presence of flow calculated using Navier-Stokes equations was studied.

Analysis of the possibilities to improve the reliability of a 15 kV overhead line exposed to catastrophic icing in Poland

Gołaś Andrzej, Ciesielka Wojciech, Szopa Krystian, Zydroń Paweł, Bąchorek Wojciech, Benesz Mariusz, Kot Aleksander, Moskwa Szczepan

Eksploatacja i Niezawodność

2019

Vol. 21, no. 2

282--288

The paper is a result of a synergic cooperation of two academic teams, i.e. power engineering and mechanical teams, and a distribution system operator. A real 15 kV overhead line exposed to a catastrophic load of ice and rime was analyzed and three solutions to improve the reliability of the tested object in such conditions were examined. Authors considered: shortening the length of the line spans, heating the main line with increased current and rebuilding the overhead line to a cable line. The researches worked out a FEM model taking into account the newest normatives, simulated the model, experimentally increased the load on the real line with measured wire temperature, and performed multi-variant calculations to determine indicators of reliability, i.e. SAIDI and SAIFI. The analyses were followed by conclusions thanks to which the reliability of power lines exposed to catastrophic icing could be increased. These inferences should be considered and applied by all distribution system operators in Poland.

Praca jest efektem synergicznej współpracy dwóch zespołów akademickich: elektroenergetycznego i mechanicznego oraz operatora systemu dystrybucyjnego. Analizie poddano rzeczywistą, napowietrzną linię średniego napięcia 15 kV narażoną na katastrofalne obciążenia lodem i szadzią. Zbadano możliwość zastosowania trzech rozwiązań mogących poprawić niezawodność badanego obiektu w takich warunkach. Rozważono: skrócenie długości przęseł linii, podgrzewanie magistrali zwiększonym prądem roboczym oraz przebudowę linii do linii kablowej. W celu realizacji pracy wykonano badania modelowo-symulacyjne MES z uwzględnieniem najnowszych wytycznych normatywnych, zrealizowano eksperyment dociążenia linii wraz z pomiarem temperatury przewodów oraz przeprowadzono wielowariantowe obliczenia niezawodnościowe prowadzące do wyznaczenia wskaźników SAIDI i SAIFI. W wyniku szczegółowych analiz sprecyzowano wnioski końcowe pozwalające na zwiększenie niezawodności linii elektroenergetycznych narażonych na katastrofalne oblodzenie, które powinny być rozważone i stosowane przez wszystkich operatorów systemów dystrybucyjnych w Polsce.