Short Answer:

Cavitation negatively affects the efficiency of hydraulic machines such as pumps and turbines. When vapor bubbles form and collapse, they disturb the flow of liquid, reduce smooth energy transfer, and create turbulence inside the machine.

This leads to energy losses, drop in pressure or head, and a decrease in overall performance. In the long term, cavitation causes wear and damage to internal parts, making the machine work harder, consume more power, and deliver less output, thus reducing its operational efficiency.

Detailed Explanation:

Cavitation Effect on Efficiency of Hydraulic Machines

Cavitation occurs when the local pressure in a fluid falls below its vapor pressure, leading to the formation of vapor bubbles. These bubbles later collapse violently in high-pressure regions, releasing energy that damages machine parts. In hydraulic machines like pumps, turbines, and propellers, cavitation causes multiple problems that directly reduce their efficiency and performance.

Efficiency in hydraulic machines is the ratio of useful output energy to input energy. When cavitation interferes with smooth fluid flow and damages components, more energy is wasted, and less useful work is done. This reduces both mechanical efficiency and hydraulic efficiency.

How Cavitation Reduces Efficiency

Flow Disturbance and Energy Loss

Vapor bubbles disturb the normal flow of fluid inside the pump or turbine.
Flow becomes turbulent, unstable, and discontinuous, especially near impellers or blades.
The machine must work harder to push the same amount of fluid, leading to extra energy consumption.

Reduction in Head or Output Pressure

In pumps, cavitation reduces the ability to generate sufficient head (pressure lift).
In turbines, it reduces the effective conversion of water energy into rotational motion.
Both cases lead to lower output for the same input, showing a clear drop in efficiency.

Vibration and Mechanical Imbalance

The violent collapse of bubbles creates pressure shocks and unbalanced forces.
These cause vibration, which reduces mechanical stability and leads to additional energy loss.

Surface Damage and Wear

Repeated cavitation leads to pitting and erosion on impellers, blades, and casings.
Worn-out parts cause irregular flow paths, which increase resistance and reduce flow rate.
Damaged parts also lower the machine’s ability to perform smoothly, requiring more power to operate.

Loss in Volumetric Efficiency

Cavitation reduces the volume of fluid handled by the machine per cycle.
Due to bubble formation, the machine handles more vapor and less liquid, reducing output.
This drop in effective fluid delivery affects volumetric and overall efficiency.

Higher Operating Costs

With cavitation, more energy is required to maintain output.
Operating costs increase due to higher power demand and frequent maintenance needs.

Practical Examples

In centrifugal pumps, cavitation lowers the total dynamic head, causing low discharge.
In hydro turbines, efficiency drops sharply if cavitation occurs near the runner blades.
In marine propellers, cavitation reduces thrust and fuel efficiency.

These impacts show why cavitation must be prevented or minimized during machine design and operation.

Conclusion:

Cavitation significantly reduces the efficiency of hydraulic machines by disturbing flow, causing energy losses, and damaging internal components. It leads to reduced pressure, flow rate, and increased power consumption. Preventing cavitation is crucial to maintain high efficiency, long equipment life, and reliable performance in civil engineering systems using pumps and turbines.