scholarly journals Near-wall pressure fluctuations over noise reduction add-ons

2017 ◽  
Author(s):  
Francesco Avallone ◽  
Wouter C. van der Velden ◽  
Roberto Merino Martinez ◽  
Daniele Ragni
Keyword(s):  
Noise Reduction ◽  
Pressure Fluctuations ◽  
Wall Pressure ◽  
Wall Pressure Fluctuations ◽  
Near Wall

Active Control Methods of Flow-Induced-Vibrations: Near-Wall-Turbulent-Pressure-Fluctuation Measurements

2002 ◽  
Author(s):  
Efim B. Kudashev ◽  
Leonid R. Yoblonik
Keyword(s):  
Turbulent Flows ◽  
Pressure Fluctuations ◽  
Wall Pressure ◽  
Control Methods ◽  
Flow Induced Vibration ◽  
Active Method ◽  
Wall Pressure Fluctuations ◽  
Turbulent Pressure ◽  
Flow Induced Vibrations ◽  
Near Wall

Near-wall pressure fluctuations in turbulent flows are of considerable interest in many engineering applications. We shall concentrate on a number of specific questions related to the resolution of components of wall pressure spectra. Our emphasis shall be on outstanding problems of experiment and theory and their relationship to one another. A study on pressure fluctuations transducer’s interaction with wall vibration resulting from near-wall turbulent flows has been performed. Piezoelectric pressure transducer generates the signal also on vibration influence. Algorithm of assign of turbulent surface pressure in conditions of flow-induced-vibration is suggested. An active method of vibration control has been developed.

Wall-Layer Scale Electromagnetic Turbulence Control in an Axisymmetric Body

Volume 1 ◽  
2004 ◽  
Author(s):  
Promode R. Bandyopadhyay ◽  
John M. Castano ◽  
Daniel P. Thivierge
Keyword(s):  
Boundary Layer ◽  
Large Diameter ◽  
Pressure Fluctuations ◽  
Axisymmetric Body ◽  
Wall Pressure ◽  
Wall Region ◽  
Turbulence Control ◽  
Wall Pressure Fluctuations ◽  
Surface Normal ◽  
Near Wall

The progress made with the control of turbulence in a boundary layer developing over a small axisymmetric body in saltwater at moderate Reynolds numbers is briefly described. A resonance-interference mechanism of control by means of a small periodic Lorenz force confined to the near-wall region, designed to overcome the issue of low efficiency of electromagnetic turbulence control in general, is attempted to alter surface normal turbulence near-wall. At a low momentum thickness Reynolds number of 2300, drag is reduced by 15–25% at a freestream speed of 5.12 m/s with an efficiency of 2–3.4%. Bi-polar pulsing succeeds in lowering surface-normal turbulence intensity near wall. It also makes wall pressure fluctuations less spiky. Positive uni-polar pulsing is found to weaken the sources of wall-pressure fluctuations residing in the logarithmic region of the boundary layer. Further confirmatory work is needed with robust electrodes and drag measurements on a large diameter axisymmetric body.

Space–time characteristics of a compliant wall in a turbulent channel flow

2014 ◽  
Vol 756 ◽  
pp. 30-53 ◽  
Author(s):  
Euiyoung Kim ◽  
Haecheon Choi
Keyword(s):  
Channel Flow ◽  
Wall Motion ◽  
Pressure Fluctuations ◽  
Turbulent Channel Flow ◽  
Space Time ◽  
Wall Pressure ◽  
Wall Displacement ◽  
Wall Pressure Fluctuations ◽  
Compliant Wall ◽  
Near Wall

AbstractThe space–time characteristics of a compliant wall in a turbulent channel flow are investigated using direct numerical simulation (DNS). The compliant wall is modelled as a homogeneous plane supported by spring-and-damper arrays and is passively driven by wall-pressure fluctuations. The frequency/wavenumber spectra and convection velocities of the wall-pressure fluctuations, wall displacement and wall velocity are obtained from the present simulation. As the spring, damping, and tension coefficients decrease, the wall becomes softer and the wall displacement and velocity fluctuations increase. For a relatively stiff compliant wall (i.e. large spring, damping and streamwise tension coefficients), there are few changes in the skin-friction drag and near-wall turbulence structures. However, when a compliant wall is soft (i.e. small spring, damping and streamwise tension coefficients), the wall moves in the form of a large-amplitude quasi-two-dimensional wave travelling in the downstream direction. This wave is generated by the resonance of the wall property and the near-wall flow is significantly activated by this wall motion. The power spectra of wall variables show distinct peaks near the resonance frequencies. The convection velocities of the wall motion and wall-pressure fluctuations become smaller with a softer wall.

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