High Fidelity Measurement Methodology of Turbulent Wall-bounded Flow Structures

Turbulent wall-bounded flows are dominated by the structure and dynamics of coherent motions. Therefore, in order to understand the mechanics of turbulence, it is essential to understand how coherent structures are generated, evolve and dissipate. This thesis has two parts: firstly a digital holography-based three-component - three-dimensional velocimetry method is developed and assessed to enable the measurement of turbulent flows; secondly, since due to COVID-19 restrictions this methodology could not be employed to study wall-bounded flows, high-resolution 2-component - 2-dimensional velocity measurements of a high Reynolds number turbulent boundary layer flow is used to analyse and reveal how coherent structures affect the viscous drag exerted by the fluid on the wall.