The correct answer is: C. space-mean speed
An enoscope is a device that measures the speed of a fluid at a specific point in space. It does this by measuring the time it takes for a particle of fluid to travel between two points. The space-mean speed is the average of the speeds of all the particles in a fluid at a given point in space.
The average speed is the total distance traveled by a particle of fluid divided by the total time it takes to travel that distance. The spot speed is the speed of a particle of fluid at a specific instant in time. The time-mean speed is the average of the speeds of all the particles in a fluid over a period of time.
Enoscopes are used in a variety of applications, including:
- Measuring the flow rate of fluids in pipes and channels
- Studying the flow of blood in the human body
- Analyzing the flow of air in a wind tunnel
- Monitoring the flow of water in rivers and streams