Transitional flow refers to a type of fluid flow that occurs between laminar and turbulent flow regimes. In this state, the flow exhibits characteristics of both smooth, orderly movement and chaotic, irregular patterns. Transitional flow typically happens at certain velocities and conditions, where the fluid's behavior can change rapidly. This flow regime is important in various applications, such as in pipe systems and aerodynamics. Understanding transitional flow helps engineers design more efficient systems by predicting how fluids will behave under different conditions, ultimately improving performance and safety in mechanical systems and transportation.