👉 In fluid dynamics, the "fluid" variable refers to any substance that flows or moves in response to external forces, such as pressure, temperature, or gravity. This includes liquids and gases, which exhibit properties like viscosity, density, and compressibility that influence their behavior under different conditions. The fluid variable is central to understanding how these substances interact with their environment, enabling the analysis of phenomena such as fluid flow, pressure distribution, heat transfer, and the forces acting upon moving fluids. It forms the basis for modeling and predicting the behavior of systems involving moving or stagnant fluids, from simple pipes to complex atmospheric and oceanic currents.
