Experimental investigations on complex vortex flows using advanced flow diagnostic techniques

Using advanced diagnostic techniques, two complex vortex flow topics were addressed in the present thesis. First, the characteristics of flow structures around building models in a tornado-like vortex were studied by using a high-resolution Particle Image Velocimetry (PIV) system. Second, the 3D vortical structures of the film cooling flows in the trailing edge of a turbine blade were studied by using a stereoscopic PIV system. The flow measurement results were correlated to the film cooling effectiveness measured by the application of a relatively new technique, pressure sensitive paint (PSP). In the study of tornado-like vortex, by using the world-largest tornado simulator of Iowa State University, a comprehensive PIV study on the flow structures around a high-rise building model and a gable-roofed building model, as well as the surface pressure measurements and force measurements, was conducted to elucidate the underlying physics. The ultimate objective of the present study is to quantify the surface winds generated by tornadoes and flow-structure interactions between tornadoes and built environments to assess wind-induced damage with the purpose of mitigating damage and improving public safety. The characteristics of tornado like flow will be demonstrated and discussed in Chapter 2. The flow features around a building model and flow-structure interactions will be discussed in Chapter 3. In the study of vortex flow in the trailing edge of a turbine blade, detailed distributions of film cooling effectiveness measurements were obtained in the cutback region of trailing edge by using the PSP technique. Before the application of PSP, a self-designed calibration facility was developed to study the characteristics and to complete the calibration of the PSP. Corresponding to the film cooling effectiveness measurements, an experimental study was conducted to quantify the characteristics of coolant flows in the cutback region at the trailing edge of a turbine blade. A high-resolution stereoscopic PIV system were used to conduct detailed flow measurements to quantitatively visualize the evolution of the unsteady vortex and turbulent flow structures in coolant jet streams, and to quantify the mixing process between the wall jet cooling streams and main streams. The film cooling effectiveness and flow characteristics in the cutback region at the trailing edge of a turbine blade will be discussed in Chapter 4