Short Answer:

Jet pumps work in fluid lifting systems by using a high-speed jet of fluid to create a low-pressure zone that draws another fluid upward. They use the principle of fluid entrainment, where a moving fluid jet pulls in surrounding fluid and lifts it to a higher level without any mechanical moving parts in the lifting section.

In civil engineering, jet pumps are commonly used for lifting groundwater, dewatering construction sites, and pumping from wells. They are efficient, simple in design, and suitable for handling mixed or sandy water without damaging the system.

Detailed Explanation

How jet pumps work in fluid lifting systems

A jet pump is a device used to lift or move fluid by using the energy of another high-velocity fluid stream. It works without any mechanical components in direct contact with the lifted fluid, making it ideal for systems where reliability and simplicity are required. Jet pumps are widely used in civil engineering applications such as well water lifting, site drainage, and groundwater control.

Jet pumps function based on the Bernoulli principle and momentum transfer. They operate by converting pressure energy into kinetic energy to form a fast-moving fluid jet. This jet creates a vacuum that draws another fluid (usually water) into the system, mixes with it, and then lifts it to the surface.

Jet pump working process in fluid lifting:

1. High-pressure fluid supply (motive fluid):

A pump delivers pressurized water (called the motive fluid) into the jet pump. This water enters a nozzle where its pressure is converted into velocity.

2. Jet formation and suction creation:

The high-speed jet from the nozzle enters a chamber (called the venturi or throat section) inside the pump. As the jet travels, it creates a low-pressure zone due to its velocity. This low pressure draws in surrounding fluid (like groundwater) from a well or tank.

3. Mixing and momentum transfer:

The motive fluid and the drawn-in fluid (called suction fluid) mix in the throat section. The energy from the high-speed jet transfers to the suction fluid, increasing its velocity.

4. Diffuser and pressure recovery:

This mixture then flows into a diffuser, a widening section of the pipe that slows the fluid down. As velocity decreases, pressure increases again, allowing the mixed fluid to be lifted and discharged to the desired location.

Applications in Civil Engineering:

1. Well Water Lifting:
   Jet pumps are ideal for shallow and deep wells, especially where mechanical parts cannot be placed inside the well.
2. Construction Site Dewatering:
   Jet pumps remove accumulated water from foundations or trenches using minimal equipment and maintenance.
3. Groundwater Control:
   In excavation zones, jet pumps help control underground water levels to maintain dry and safe working conditions.
4. Irrigation and Water Supply:
   Jet pumps are used in agricultural fields to lift water from canals or underground tanks for irrigation.
5. Industrial Waste Handling:
   Jet pumps can also handle mixed fluids or slurries with some solids without clogging.

Advantages of Jet Pumps:

• No moving parts inside the fluid path, reducing wear
• Easy to maintain and operate
• Works at various depths, especially in deep wells with proper setup
• Suitable for dirty or sandy water
• Compact and flexible for temporary or mobile use

However, jet pumps are generally less efficient than mechanical pumps and may require a larger power supply to generate enough pressure for the motive fluid. Careful design of the nozzle, throat, and diffuser is necessary for best performance.

Conclusion:

Jet pumps work in fluid lifting systems by using a high-speed fluid jet to create suction and lift another fluid. They operate based on velocity, pressure difference, and fluid entrainment, making them useful in groundwater lifting, dewatering, and other civil engineering tasks. With no moving parts in the submerged section, jet pumps offer durability and reliability, especially in tough working conditions.