Köşeleri yuvarlanmış açık kavitelerin aeroakustik analizleri

The main goal of this thesis is to understand the effect of rounding the edges of a cavity on sound generated by the cavity flow. To achieve this goal, the first step is to understand the physics of the flow. Then understand the aeroacoustic analogies and select the appropriate one for the specific case. Then conduct an effective CFD analysis and with the obtained data calculate the noise generated by the cavity flow using aeroacoustic analogies. A wide literature review of on cavity flow physics has been conducted and it is seen that the most important feature of the cavity flow is the self-sustained oscillations. There are 3 main types of oscillations: fluid dynamic, fluid resonant and fluid elastic oscillations. These have different characteristics and it is important to know it is possible to see several of them in the same flow. The first step to understand the noise generated by the cavity and control it is to understand these mechanism in detail. Aeroacoustics is the main focus of this thesis. Aeroacoustics can be explained briefly as the sound generated aerodynamically, which is also the name of Sir Michael James Lighthill's important paper. This topic became an important area of research nowadays, as the outcomes can cause distinguishable effects on many applications. In aircrafts sound generation can cause discomfort to passengers and humans nearby the airfields. Reducing the sound emissions from these sources is the most important way to effective noise control. To achieve this important goal aeroacoustic analogies are used. In this thesis a Modified Curle's Analogy used, as it deals with static compact bodies. To use this analogy, unsteady pressure data obtained from the walls of the cavity is required. To obtain this data, a CFD analysis by using a commercial tool should be conducted. In this tool, an unsteady analysis with the time step of $10^{-7}$ is conducted. The solver was an implicit unsteady solver with the turbulence model of RANS and realizable $k-\epsilon$ model with two layer all $y+$ wall treatment. As the solution domain, a cavity with the aspect ratio of 2 is selected. The length of the cavity is 0.3 m and the depth of it is 0.015 m. This is selected as a validation case and it is compared with a thesis that conducted a PIV analysis on a cavity with the same geometry. After the validation is confirmed, analyses with 3 different geometries are conducted. First of the geometry has a rounded leading edge with the radius of 3 mm. Second geometry has a rounded trailing edge with the same radius and the last geometry has both of its edges rounded with the same radius. Pressure data obtained from the CFD analyses and fed in to our source code that uses the Modified Curle's Equation to calculate the sound generated by the cavity. This source code give sound pressures as output and they are fed into an FFT code to get sound pressure level (SPL) values. After that OASPL datas are calculated and the first case is validated with the validation thesis. The next step is to conduct analyses with different geometries and investigate the effects of the rounded edges.