1. Flow Produced Noise & Fluid Mechanical Treatment Flow Produced Noise & Fluid Mechanical Treatment Prepared By: Eng. Ashraf Al-Shalalfeh Mechanical Engineering Dept. Faculty Of Engineering & Tech. University Of Jordan

2. Noise effect on health Noise effect on health  It can destroy hearing.  It can create physical and psychological stress.  And it can contribute to accidents by making it impossible to hear warning signals.  It can destroy hearing.  It can create physical and psychological stress.  And it can contribute to accidents by making it impossible to hear warning signals.

3. Basic Noise terms  Sound  Frequency  Noise  Sound  Frequency  Noise

4. Sound  Sound is produced when a sound source sets the air nearest to it in wave motion  Sound travels in air at a speed of about 340 meters per second.  The rate of travel is greater in liquids and solids; for example, 1,500 m/s in water and 5,000 m/s in steel.  Sound is produced when a sound source sets the air nearest to it in wave motion  Sound travels in air at a speed of about 340 meters per second.  The rate of travel is greater in liquids and solids; for example, 1,500 m/s in water and 5,000 m/s in steel.

5. Frequency  The frequency of a sound wave refers to the number of vibrations per second.  Sound is found within a large frequency range.  measured in units of hertz (Hz).  The frequency of a sound wave refers to the number of vibrations per second.  Sound is found within a large frequency range.  measured in units of hertz (Hz).

6. Noise  It is customary to call any undesirable sound “noise”  The disturbing effects of noise depend both on the intensity and the frequency of the tones.  higher frequencies are more disturbing than low ones.  Pure tones are more disturbing than a sound made up of many tones.  It is customary to call any undesirable sound “noise”  The disturbing effects of noise depend both on the intensity and the frequency of the tones.  higher frequencies are more disturbing than low ones.  Pure tones are more disturbing than a sound made up of many tones.

7. The possibility of flow-produced noise may be raised if the flow velocity in a system is increased for better performance. What is the Flow produced-Noise? Laminar Flow Turbulent Flow

8.  marine structures, such as marine risers, and sub surface pipelines.  units used in various power generation plants and chemical plants.  marine structures, such as marine risers, and sub surface pipelines.  units used in various power generation plants and chemical plants. Where Flow Produced- noise Found?

9.  Pressure  Density  Velocity (longitudinal)  Temperature  Pressure  Density  Velocity (longitudinal)  Temperature Noise is a disturbance in :

10.  Control valve is an important example on the high Noise emission.  Noise results at certain operating conditions from the internal flow in the form of pressure and velocity pulses in the flowing medium.  These propagate themselves in the pipelines and produce mechanical noise.  Control valve is an important example on the high Noise emission.  Noise results at certain operating conditions from the internal flow in the form of pressure and velocity pulses in the flowing medium.  These propagate themselves in the pipelines and produce mechanical noise. Control Valves

11.  Turbulence due to turbulent flow leaving the throttle cross-section at a higher speed leads to turbulence and relieves with wide-band noises.  When the sonic velocity is reached and the downstream pressure further decreases, substantial sound level increases  Turbulence due to turbulent flow leaving the throttle cross-section at a higher speed leads to turbulence and relieves with wide-band noises.  When the sonic velocity is reached and the downstream pressure further decreases, substantial sound level increases compressible flow media (gases and vapors)

12.  Due to a pressure reduction to the vapor pressure of the liquid in the throttling point area vapor bubbles are formed which subsequently implode due to the pressure recovery.  Which becomes noticeable as a sudden drumming noise when cavitation starts.  Due to a pressure reduction to the vapor pressure of the liquid in the throttling point area vapor bubbles are formed which subsequently implode due to the pressure recovery.  Which becomes noticeable as a sudden drumming noise when cavitation starts. non-compressible flow (liquids)

13. Compressible media (gases and vapors)  Valve inlet Pressure [bar absolute]  Valve inlet Temperature [K]  Standard density, standard  conditions.  Pressure ratio or differential pressure  ratio   Valve correction element (type), standard  valves with special noise reducing measures = 0 dB.  Pipeline correction element,,  for nominal pressure 40 = 0 dB  Valve inlet Pressure [bar absolute]  Valve inlet Temperature [K]  Standard density, standard  conditions.  Pressure ratio or differential pressure  ratio   Valve correction element (type), standard  valves with special noise reducing measures = 0 dB.  Pipeline correction element,,  for nominal pressure 40 = 0 dB

14.  An increasing inlet pressure, increasing temperature at the inlet, with a larger differential pressure ratio x and increasing (mass flow).  An increasing inlet pressure, increasing temperature at the inlet, with a larger differential pressure ratio x and increasing (mass flow). Noise pressure level in [dB(A)] at 1m from the pipeline behind the valve: The sound pressure level rises with: The sound pressure level falls with:  With higher standard density. The sound pressure level falls with:  With higher standard density.

15. Non-Compressible media (liquids)  Valve inlet Pressure [bar absolute]  Vapor Pressure [bar absolute]  Density at inlet  Pressure difference ratio   Valve correction element (type), standard  valves with special noise reducing measures = 0 dB.  Valve parameter: z value (load-dependent)  Pipeline correction element,,  for nominal pressure 40 = 0 dB  Valve inlet Pressure [bar absolute]  Vapor Pressure [bar absolute]  Density at inlet  Pressure difference ratio   Valve correction element (type), standard  valves with special noise reducing measures = 0 dB.  Valve parameter: z value (load-dependent)  Pipeline correction element,,  for nominal pressure 40 = 0 dB

16. Noise pressure level in [dB(A)] at 1m from the Pipeline behind the valve: Noise pressure level in [dB(A)] at 1m from the Pipeline behind the valve:

17.  Increasing difference between the inlet pressure and the vapor pressure as well as a larger differential pressure ratio and increasing Value (mass flow).  Increasing difference between the inlet pressure and the vapor pressure as well as a larger differential pressure ratio and increasing Value (mass flow). The sound pressure level rises with: The noise level falls with:  higher density

18. Mechanical & Fluid Treatment

19.  When air passes by an object at certain speeds, a strong pure tone, known as a Karman tone, can be produced.  This can be prevented by making the object longer in the direction of flow, such as with a "tail," or by making the object's shape irregular.  When air passes by an object at certain speeds, a strong pure tone, known as a Karman tone, can be produced.  This can be prevented by making the object longer in the direction of flow, such as with a "tail," or by making the object's shape irregular.

20. Ducts without impediments produce the least amount of noise from turbulences.

21. A new branch must be created with softer bends. Tubing pieces are placed between the valves, so that turbulence will be reduced or eliminated before the stream reaches the next valve.

22. When a flowing gas mixes with a non-moving gas, noise may be produced, especially if the flow is disturbed before the outlet. A lower outflow speed will produce a lower sound level. Lower speed

23. The exhaust air from a compressed air-driven grinding machine produces a loud noise. A new handle is developed, filled with a porous sound-absorbing material between two fine-meshed gauzes. The exhaust air from a compressed air-driven grinding machine produces a loud noise. A new handle is developed, filled with a porous sound-absorbing material between two fine-meshed gauzes.

24. The term "jet stream" applies at flow speeds in excess of 325 ft/sec. Turbulence outside the outlet is great. noise production can be it greatly reduced by using an air stream with a lower speed outside the jet stream. Slow Outer Stream

25. The low frequency noise of a gas outlet can be reduced by replacing a large outlet with several small ones. To some extent this will increase the high frequency noise, but this is more easily controlled.

26. Fans make less noise if placed in smooth, undistributed flow streams

27. The control vanes are moved farther from the fan so that the turbulence has time to die down. In the other case, the bend is made smoother, and the fan is moved away from the' bend. Turning vanes could also be used Increase Distance

28.  Rapid pressure changes produce more Noise. Gas is released in the form of bubbles and produces a roaring noise.  Noise is avoided by a slow change in volume.  Rapid pressure changes produce more Noise. Gas is released in the form of bubbles and produces a roaring noise.  Noise is avoided by a slow change in volume.

29.  Noise production takes place at control valves, at pump pistons, and at propellers when large and rapid pressure drops occur in liquids. This so- called "cavitation“.  Cavitation can be reduced by bringing about the pressure reduction in several smaller steps.  Noise production takes place at control valves, at pump pistons, and at propellers when large and rapid pressure drops occur in liquids. This so- called "cavitation“.  Cavitation can be reduced by bringing about the pressure reduction in several smaller steps. Large and rapid changes in pressure produce "cavitation" noise Large and rapid changes in pressure produce "cavitation" noise

30.  Vibration isolation of a machine may be ineffective if sound is transferred through connections for oil, electricity, water.  These connections must be made very flexible. The machine movements will be reduced if a flexible connection used.  Vibration isolation of a machine may be ineffective if sound is transferred through connections for oil, electricity, water.  These connections must be made very flexible. The machine movements will be reduced if a flexible connection used.

31.  Turbulent fluid flow within pipes produces noise which transmitted to the building structure.  the pipe can be covered with sound absorbing material. The vibrations can be isolated from the wall with flexible connecting mechanisms.  Turbulent fluid flow within pipes produces noise which transmitted to the building structure.  the pipe can be covered with sound absorbing material. The vibrations can be isolated from the wall with flexible connecting mechanisms. Noise absorbing material Linear spring

32. Machines should be vibration isolated  Vibration isolation of pipelines can reduced the area of excessive noise.  Vibration isolators are made of various materials and in various shapes. Machines should be vibration isolated  Vibration isolation of pipelines can reduced the area of excessive noise.  Vibration isolators are made of various materials and in various shapes.