Viscosity, density, and surface tension are all properties of fluids. Viscosity is the resistance of a fluid to flow, density is the mass per unit volume of a fluid, and surface tension is the tendency of a fluid to minimize its surface area.

The SI unit of viscosity is the pascal-second (Pa·s). It is defined as the shear stress required to produce a unit velocity gradient in a fluid.

Laminar flow, turbulent flow, and compressible flow are all types of fluid flow. Laminar flow is characterized by smooth, orderly flow, while turbulent flow is characterized by chaotic, irregular flow. Compressible flow is characterized by changes in density due to changes in pressure.

The Reynolds number is a dimensionless number that characterizes the flow regime of a fluid. It is defined as the ratio of inertial forces to viscous forces in a fluid.

Fluid mechanics is used in the design of aircraft wings, ship hulls, and wind turbines. In each case, fluid mechanics is used to understand the flow of air or water around the object and to design the object in a way that minimizes drag and maximizes lift or thrust.

The Bernoulli equation is an equation that relates the pressure, velocity, and elevation of a fluid. It is used to analyze the flow of fluids in pipes, channels, and other fluid systems.

The Navier-Stokes equation is a set of equations that govern the motion of a viscous fluid. It is a complex set of equations that can be difficult to solve, but it is used to model a wide variety of fluid flows.

The Darcy-Weisbach equation is an equation that relates the pressure drop in a pipe to the flow rate, pipe diameter, and pipe length. It is used to design and analyze piping systems.

The Moody diagram is a graph that shows the relationship between the friction factor, Reynolds number, and relative roughness of a pipe. It is used to design and analyze piping systems.

The Pitot tube is a device used to measure the velocity of a fluid. It consists of a tube that is pointed upstream into the flow. The pressure inside the tube is measured and used to calculate the velocity of the fluid.

The Venturi meter is a device used to measure the flow rate of a fluid. It consists of a section of pipe that is constricted in the middle. The pressure drop across the constriction is measured and used to calculate the flow rate of the fluid.

The orifice plate is a device used to measure the flow rate of a fluid. It consists of a plate with a hole in the middle. The pressure drop across the plate is measured and used to calculate the flow rate of the fluid.

The rotameter is a device used to measure the flow rate of a fluid. It consists of a vertical tube with a float inside. The float is lifted by the flow of the fluid, and the position of the float is used to indicate the flow rate.

The ultrasonic flow meter is a device used to measure the flow rate of a fluid. It consists of a pair of transducers that are mounted on the outside of a pipe. The transducers emit ultrasonic waves into the fluid, and the waves are reflected back to the transducers. The difference in the time it takes for the waves to travel upstream and downstream is used to calculate the flow rate of the fluid.