Wyniki wyszukiwania - BazTech

1

Implementation of Ffowcs Williams and Hawkings aeroacoustic analogy in OpenFOAM

Jarosz K., Czajka I., Gołaś A.

Vibrations in Physical Systems

|

2016

|

Vol. 27

161--168

EN

This paper presents the development of post-processing aeroacoustics utility for OpenFOAM, based on Ffowcs Williams-Hawkings aeroacoustic analogy. Although the FH-W analogy is well known for almost 50 years, there is a lack of open-source software which is using it, hence decision to perform this implementation. This is the veryfirst version of utility, so only one formulation of FH-W were implemented. Presented application allows to compute far-field acoustic pressure from near field CFD solution. Validation is based on NASA Tandem Cylinder Case. Comparison of the results from simulation show fairly good agreement with experimental data.

2

Badania numeryczne wpływu wybranych parametrów konstrukcyjnych na hałas aerodynamiczny wentylatora promieniowego

Romik D., Czajka I., Gołaś A.

Prace Instytutu Mechaniki Górotworu PAN

|

2016

|

T. 18, nr 2

43--52

PL

W artykule zamieszczono częściowe wyniki prac których celem jest modyfikacja konstrukcji wentylatora promieniowego w celu minimalizacji generowanego hałasu aerodynamicznego przy założonej wydajności i spiętrzeniu. Analiza dotyczy zmian kształtu obudowy spiralnej wentylatora promieniowego w okolicy języczka. Zbadano zmiany odległości promieniowej języczka obudowy od wirnika. Zmodyfikowano geometrię obudowy w celu osiągnięcia lepszej wydajności wentylatora. Przedstawiono wpływ zmian geometrii na wydajność wentylatora. Symulacje komputerowe oraz analiza wyników modelu 2D przeprowadzone zostały w programie Ansys Fluent.

EN

The article describes partial research results of the radial fan structure influence on generated aerodynamic noise. The analysis deals with changes of the shape of the volute casing and also distance between rotor and tongue of the volute. After partial model validation authors present estimated pressure fluctuations for 4 different rotor-stator distances. Authors also shows a change in radial fan performance due to changes in rotor-stator geometry. Analysis was performed based on developed 2D radial fan models. The flow analysis was carried out using Ansys Fluent software.

3

Sensitivity Analysis of Acoustic Field Parameters on a Change of Boundary Conditions in a Room

Suder-Dębska K., Czajka I., Czechowski M.

Archives of Acoustics

|

2014

|

Vol. 39, No. 3

343--350

EN

The area of environmental protection concern minimises the impact that technical objects have on the environment. Usually the most effective way of protecting the environment is to influence the source of the problem. For this reason studies are conducted to modify the construction of machines, power machines in particular, so as to minimise their impact on the environment. In the case of environmental protection from noise it is most convenient to carry out measurements in an anechoic chamber. Unfortunately, this is possible only in very limited circumstances. In all other cases measurements are performed using an engineering method or the survey method, both of which are described in the standards and by taking into account the so-called environmental corrections. The obtained results are burdened with greater error than those of measurements in an anechoic chamber. Therefore, it would seem advantageous to develop a method of obtaining similar and reliable results as those in an anechoic chamber, but in a reverberant field. The authors decided to use numerical modelling for this purpose. The main objective of this work is a comprehensive analysis of the numerical model of a laboratory designed for acoustic tests of selected power machines. The geometry of a room comprising an area of analysis is easy to design. The main difficulty in modelling the phenomena occurring in the analysed area can be the lack of knowing the boundary conditions. Therefore, the authors made an attempt to analyse the sensitivity of various acoustic parameters in a room in order to change these boundary conditions depending on the sound absorption coefficient.

4

Estimation of Acoustic Impedance for Surfaces Delimiting the Volume of an Enclosed Space

Piechowicz J., Czajka I.

Archives of Acoustics

|

2012

|

Vol. 37, No. 1

97-102

EN

Several methods can be applied for analyses of the acoustic field in enclosed rooms namely: wave propagation, geometrical or statistical analysis. The paper presents problems related to application of the boundary elements method to modelling of acoustic field parameters. Experimental and numerical studies have been combined for evaluation of acoustic impedance of the material used for the walls of a model room. The experimental studies have been carried out by implementing a multichannel measuring system inside the constructed model of an industrial room. The measuring system allowed simultaneous measurements of the source parameters – the loudspeaker membrane vibration speed, the acoustic pressure values in reception points located inside the model space as well as phase shifts between signals registered in various reception points. The numerical modelling making use of the acoustic pressure values measured inside the analyzed space allowed determination of requested parameters of the surface at the space boundary.

5

Eksperymentalna weryfikacja wybranych zależności opisujących moc akustyczną wentylatorów

Fortuna S., Czajka I.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

|

2010

|

nr 138

21-32

PL

Artykuł zawiera weryfikację wybranych zależności określających moc akustyczną generowaną przez wentylatory w oparciu o wyniki pomiarów poziomów ciśnienia akustycznego wokół wentylatora zrealizowanych zgodnie z normą PN-72/M-43120. Autorzy dokonują estymacji mocy akustycznej wentylatora promieniowego z wykorzystaniem symulacji komputerowej oraz pseudoodwrotności Moore’a-Penrose’a. Określono niepewność pomiaru poziomu ciśnienia akustycznego oraz estymacji poziomu mocy akustycznej źródła.

EN

This paper describes experimental verification of selected equations describing sound power level in fans. Measurement were based on PN-72/M-43120 norm. There is presented method of estimation Sound Power Level of source with computer simulation and Moore-Penrose pseudoinversion. Uncertainty of sound pressure level and sound power level of source was determined.