Fluid dynamics is a branch of physics that deals with the behavior of fluids (liquids and gases) in motion. It is a fundamental subject in engineering, physics, and applied sciences, playing a crucial role in various industries, including aerospace, automotive, energy, and environmental studies. Understanding how fluids move and interact with their surroundings helps engineers and scientists design efficient systems, predict natural phenomena, and develop innovative technologies.

At its core, fluid dynamics is governed by a set of fundamental principles derived from classical mechanics and thermodynamics. These include the conservation of mass, momentum, and energy. The governing equations, such as the Navier-Stokes equations, describe the motion of fluids by relating forces, pressure, velocity, and viscosity. The study of fluid dynamics is essential for solving real-world problems, from designing aircraft wings and optimizing fuel injection systems to predicting weather patterns and ocean currents.

Fluids can exhibit different types of motion depending on external forces, constraints, and their physical properties. A key distinction in fluid dynamics is between laminar flow and turbulent flow. Laminar flow is characterized by smooth, orderly fluid layers, whereas turbulent flow is chaotic and involves complex mixing and vortices. The Reynolds number, a dimensionless quantity, helps determine whether a flow will be laminar or turbulent based on factors like velocity, viscosity, and characteristic length.