Fluid dynamics is an extremely broad area of study where the motion of fluids is investigated and characterized across a wide range of length and time scales. In a majority of practical applications, fluid flow is turbulent in nature, a condition where the fluid motion is highly three-dimensional and stochastic. While the Navier-Stokes equations (governing equations in fluid mechanics) are applicable to all fluid flows, determining a general solution for these equations for turbulent flows is computationally challenging and mathematically impossible.
Hence, experimental research is a leading contributor to the advancement of knowledge on fluid dynamics. Experimental research is heavily reliant on the tools and techniques of performing measurements of fluid phenomena. Fluid velocity is one of the fundamental variables and a parameter of interest in fluid mechanics. Hence, knowing the fluid velocity field in time and/or space is often the primary objective in fluid dynamics research. Thus, most of the tools and
techniques used in experimental fluid mechanics research are used to measure the fluid velocity in a given flow.