<div>Bladeless fans are well known for their unique shape and efficient performance, which have a great impact on the fan industry. At present, there are few studies on the bladeless fan and the research on the improvement of fan design is a lack. Therefore, the study on the performance of the bladeless fan with different design is the main purpose of this thesis. </div><div>In the present study, a bladeless fan prototype is created and studied by numerical simulations. When characterizing the aerodynamic and aeroacoustic performances of the bladeless fan, the entire fan prototype, including wind channel, base, rotor and stator, is adopted; when investigating the influence of the wind channel's geometric parameters, only wind channel is considered in simulations. The influence of the slit width, the height of the cross-section, the slit location and the profile of the cross-section are studied. </div><div><br></div><div>It is found that the flow outside the bladeless fan consists of the air blown out from the wind channel and entrained from the back and side of the fan. The air entrained from the side is the main source of flow rate increase. As for the aeroacoustic performance, the rotor and stator inside the base are the predominated source of the noise generated by the bladeless fan. </div><div>The performances of the bladeless fan are very sensitive to the geometric details of the wind channel. The generated noise always increases as the wind strength improves. The slit width of the wind channel has the greatest impact. With the slit moves away from the leading edge, the wind produced by the bladeless fan becomes more powerful and the noise becomes louder. The cross-sectional height of 4cm has the best aerodynamic performance but the generated noise is a little larger than other designs. The profile of the cross-section shows insignificant influence on the performances. </div>

Near-field Acoustical Holography is a tool that is conventionally used to visualize sound fields through an inverse process in a three-dimensional space so that either sound field projections or sound source localization can be performed. The visualization is conducted by using sound pressure measurements taken in the near-field region close to the surface of the unknown sound source. Traditional Fourier-based Near-field Acoustical Holography requires a large number of measurement inputs to avoid spatial truncation effects. However, the use of a large number of measurements is usually not feasible since having a large number of microphones is costly, and usually the array is limited in size by the physical environment, thus limiting the practicality of this method. In the present work, because of the desire to reduce the number of microphones required to conduct acoustical holography, a method known as Statistically Optimized Near-field Acoustical Holography initially proposed by Steiner and Hald was analyzed. The main difference between the present work and the concept mentioned by Steiner and Hald is the cylindrical coordinate system employed here for the purpose of experimenting on a bladeless fan, which resembles a cylindrical structure and which could be assumed to be a cylindrical source. The algorithm was first verified <i>via</i> simulations and measurements, and was then applied to experimental data obtained <i>via</i> pressure measurements made with a cylindrical microphone array. Finally, suggestions for noise control strategies for the bladeless fan are described, based on the measurement results.<br>