Fluid dynamics refers to the study of fluids in motion. Fluid motion is represented by velocity vectors or streamlines. A multitude of velocity vectors at different points show the fluid motion by arrows representing their magnitudes and direction. Streamlines are the curves obtained by plotting the tangent to the instantaneous velocity vector at each point in the fluid. Fluid flow can be either laminar or turbulent. In laminar flow, fluid travels in smooth and parallel layers, whereas in turbulent flow, fluid travels irregularly, and its motion changes abruptly and continuously over time. The flow pattern of fluid depends on flow speed, roughness of the flow path and density of the fluid. A river flowing through a plain region represents laminar flow, but when a motorboat crosses it, its flow turns turbulent forming swirls and waves. A water fountain exhibits laminar flow at lower flow speed, however, at greater speed, its flow turns turbulent.