Možnosti modelování akustických jevů

Abstract

The dissertation thesis is focused on the identification of the aeroacoustic phenomena generated by the flow around the body by air and creating the methodology for using experimental and mathematical methods. In the introduction of thesis, the theory of acoustic phenomena and their perception by the human ear are presented. In the next section, the theory of the modelling of the aerodynamic field, which serves as input data for the acoustic part of the task, is described. For the acoustic field modelling acoustic analogies are used. In the experimental part of the task the measurements for aerodynamic and acoustic field on the wind tunnel are realized. The aerodynamic field measurement is performed by the hot-wire anemometer probe. The acoustic field measurement in the experimental mechanism is done by the microphone with conical cone. In conclusion of this part of the thesis an analysis and assessment of uncertainties of experimental measurements are executed. The numerical modelling of the aeroacoustic task consists in the creation of the mathematical model in Ansys Fluent using by Ffowcs-Williams and Hawkings acoustic analogy (FW-H) which is currently the standard for the modelling of such a complex task. In addition, the methodology for modelling the problem in freely distributed software OpenFOAM 3.0.x using Curle acoustic analogy was created. As the basic task for the complex solution of the aeroacoustic task the flow around the cylinder is selected. The selected task is solved as a two dimensional (2D) and three-dimensional (3D) task. As a complementary task in the appendix, the methodology of solution 3D task flow around the sphere is elaborated. At the conclusion of this chapter the comparison of the numerical results with experimentally obtained data and comparison between computational programs are performed. In the last section of the dissertation thesis the brief summary of the optimization options is performed for the flow around obstacle in order to decrease the noise. At the end of this thesis, the summary of the thesis, the evaluation of the achieved results, the possibilities of industrial applicability of the results and some recommendations for further solution development in the numerical modelling and experimental measurement fields are listed.