Reynolds-Averaged Navier-Stokes (RANS) is a mathematical approach used to analyze fluid flow, particularly in turbulent conditions. It simplifies the complex equations governing fluid motion by averaging the effects of turbulence over time. This allows engineers and scientists to predict how fluids behave in various scenarios, such as airflow around vehicles or water flow in pipes. RANS equations are derived from the Navier-Stokes equations, which describe the motion of viscous fluid substances. By applying statistical methods, RANS helps in modeling the mean flow characteristics while accounting for the chaotic nature of turbulence, making it a valuable tool in fields like aerodynamics and hydraulics.