Turbulence and noise are common challenges in fluid systems, such as pipes, ducts, valves, pumps, and fans. They can reduce efficiency, increase wear and tear, and create unwanted vibrations and sounds. In this article, you will learn some basic principles and techniques to minimize turbulence and noise in fluid systems.
Turbulence is a phenomenon that occurs when a fluid flows at high speeds or over irregular surfaces. It causes the fluid to form chaotic and unpredictable eddies, vortices, and fluctuations. Turbulence increases the drag, friction, and pressure losses in the system, and also generates noise by interacting with the walls and components of the system.
Turbulence can be avoided by right design ie lower velocity, maintaining flow as laminar flow. However, turbulence is not always bad. Turbulent flow is required for proper mixing of fluids. Turbulent flow in heat exchanger improves its efficiency. During transfer of slurry / mixture turbulent flow is required, else it may get separated.
Factors adding to flowing fluid noise depends on density of fluid, speed ,shape of container, pipe ,objects through which it is flowing. Turbulence is a fluid flow in which layers mix together via eddies and swirls. It has two main causes. First,?any obstruction or sharp corner, such as in a faucet, creates turbulence by imparting velocities perpendicular to the flow. Second, high speeds cause turbulence. So by keeping right pipe diameter ,right curves , proper viscosity with right limited velocity turbulence can be controlled.
Noise is a form of sound that is unwanted or harmful. It can be caused by various sources in fluid systems, such as turbulent flow, cavitation, flow-induced vibration, and mechanical operation. Noise can affect the performance, safety, and comfort of the system and its users. It can also cause fatigue, stress, and damage to the system and the surrounding environment.
Noise is unwanted sound considered unpleasant, loud, or disruptive to hearing. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrations through a medium, such as air or water. The difference arises when the brain receives and perceives a sound. It is important to control it at the starting point by proper design of components
One way to reduce turbulence is to optimize the design and layout of the system. This includes choosing smooth and round pipes and ducts, avoiding sharp bends and sudden changes in cross-section, and minimizing obstructions and fittings. Another way to reduce turbulence is to control the flow rate and velocity of the fluid. This can be done by using appropriate pumps, fans, valves, and regulators. A lower flow rate and velocity can reduce the Reynolds number, which is a dimensionless parameter that indicates the likelihood of turbulence.
In turbulent flow the speed of the fluid at a point is continuously undergoing changes in both magnitude and direction.So we need to control the flow rate and velocity of the fluid with respect to material and design for smooth flow.
One way to reduce noise is to address the sources of turbulence, as explained above. Another way to reduce noise is to use noise reduction devices and materials. These include silencers, mufflers, baffles, diffusers, and acoustic insulation. These devices and materials can absorb, reflect, or cancel out the noise generated by the fluid system. A third way to reduce noise is to isolate and decouple the system from the surrounding structure. This can be done by using flexible connections, vibration dampers, and anti-vibration mounts. These methods can prevent the transmission and amplification of noise and vibration.
To measure turbulence and noise, you need to use appropriate instruments and methods. For turbulence, you can use devices such as pitot tubes, anemometers, flow meters, and pressure sensors. These devices can measure the flow rate, velocity, pressure, and turbulence intensity of the fluid. For noise, you can use devices such as microphones, sound level meters, and spectrum analyzers. These devices can measure the sound pressure level, frequency, and spectrum of the noise.
To evaluate turbulence and noise, you need to use appropriate criteria and standards. For turbulence, you can use criteria such as the Reynolds number, the friction factor, and the pressure drop. These criteria can indicate the degree of turbulence and its effects on the system. For noise, you can use criteria such as the sound power level, the sound pressure level, and the sound quality. These criteria can indicate the loudness, the annoyance, and the psychoacoustic characteristics of the noise. You can also use standards such as ISO, ANSI, and ASHRAE to compare and comply with the recommended or required levels of turbulence and noise.
Back in the good old bad old days, heating system piping could operate well without pumps by using the thermosyphon principle.
while working on a diesel engine installation on a ship we used a mixer unit where sea water will be mixed with exhaust to reduce the noise