Q1: __________ fluid force is not considered in the Navier-Stokes equation.

ANS:A - Turbulent

Turbulence refers to the chaotic and irregular motion of fluid flow characterized by fluctuations in velocity, pressure, and other flow properties. It is a common phenomenon observed in fluid dynamics, occurring when the flow becomes highly disordered and unpredictable. Here are some key characteristics and aspects of turbulence:

1. Irregular Flow: Turbulent flow is characterized by irregular and seemingly random fluctuations in velocity and pressure throughout the fluid. These fluctuations occur at different spatial and temporal scales, ranging from large-scale eddies to small-scale turbulent structures.
2. Vortices and Eddies: Turbulence often involves the formation of vortices and eddies within the flow, which are swirling regions of fluid motion. These vortices can vary in size and intensity, interacting with each other to create complex flow patterns.
3. Energy Dissipation: Turbulent flow involves the transfer of kinetic energy from large-scale motions to smaller-scale motions through a process known as energy cascade. This results in the dissipation of energy into heat due to viscous effects within the fluid.
4. Reynolds Number: The transition from laminar (smooth and orderly) flow to turbulent flow is characterized by a dimensionless parameter known as the Reynolds number. When the Reynolds number exceeds a critical value, the flow becomes turbulent.
5. Applications: Turbulence is prevalent in various natural and engineered systems, including atmospheric flows, ocean currents, river flows, combustion processes, and industrial fluid systems. Understanding and controlling turbulence is crucial for optimizing the performance and efficiency of these systems.
6. Challenges: Turbulence presents significant challenges in fluid dynamics and engineering, as it complicates flow predictions and can lead to increased energy consumption, erosion, noise, and structural fatigue in engineering systems.