Fluid mechanics is the branch of physics that studies the behavior of fluids (liquids and gases) and the forces acting on them. It is fundamental in understanding phenomena in engineering, meteorology, oceanography, and biology, where fluid flow is crucial.
Non-steady state flow refers to a fluid flow condition where the velocity, pressure, and other flow properties change with time at any given point in the flow field. This is in contrast to steady state flow, where these properties remain constant over time, making non-steady state flow more complex to analyze due to its time-dependent nature.