Measurements of the fluctuating pressure at the wall beneath a thick turbulent boundary layer

1962 ◽  
Vol 14 (2) ◽  
pp. 187-210 ◽  
Author(s):  
W. W. Willmarth ◽  
C. E. Wooldridge
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Pressure Fluctuations ◽  
Spatial Separation ◽  
Wall Pressure ◽  
Small Scale ◽  
Mean Square ◽  
Pressure Transducers ◽  
Wall Pressure Fluctuations ◽  
Displacement Thickness

Measurements of the turbulent pressure field at the wall beneath a thick (5-inch) turbulent boundary layer produced by natural transition on a smooth surface are reported. The data include the mean-square pressure, parallel to the stream, and spatial correlation of the pressure transverse to the stream.The root-mean-square wall pressure was 2.19 times the wall shear stress. The power spectra of the pressure were found to scale with the free-stream speed and the boundary-layer displacement thickness. A few tests with a rough surface showed that the increase in root-mean-square wall pressure was greater than the increase in wall shear stress.The space-time correlation measurements parallel to the stream direction exhibit maxima at certain time delays corresponding to the convection of pressure-producing eddies at speeds varying from 0.56 to 0.83 times the stream speed. The lower convection speeds are measured when the spatial separation of the pressure transducers is small, or when only the pressure fluctuations at high frequencies are correlated. Higher convection speeds are observed when the spatial separation of the pressure transducers is large, or when only low frequencies are correlated. The result that low-frequency pressure fluctuations have the highest convection speed is in agreement with the measurements of Corcos (1959, 1962) in a fully turbulent tube flow. Analysis of these measurements also shows that both large- and small-scale pressure-producing eddies decay after travelling a distance proportional to their scale. More precisely, a pressure-producing eddy of large or small wavelength λ decays and vanishes after travelling a distance of approximately 6λ.The transverse spatial correlation of the wall-pressure fluctuations was measured and compared with the longitudinal scale. Both the transverse and the longitudinal scale of the pressure fluctuations were of the order of the boundary-layer displacement thickness. The transverse and longitudinal scales of both large- and small-scale wall-pressure fluctuations were also measured and were also found to be approximately the same.

Effect of Bubbles on Flow Induced Vibration

2006 ◽  
Author(s):  
Angela R. Pelletier ◽  
Ian A. McKelvey ◽  
Joseph Katz
Keyword(s):  
Boundary Layer ◽  
Bubble Size ◽  
Pressure Fluctuations ◽  
Wall Pressure ◽  
Flow Induced Vibration ◽  
Pressure Transducers ◽  
Plate Vibrations ◽  
Wall Pressure Fluctuations ◽  
Bubble Sizes ◽  
The Impact

The effects of a turbulent, bubbly boundary layer on wall skin friction have been investigated in numerous previous studies. However, the impact of such a multiphase flow on fluid-structure interactions has not been studied. To this end, the present project examines experimentally the effect of a bubbly boundary layer on the vibration of a vertical plate. Using a combination of accelerometers and pressure transducers, we simultaneously measure the plate vibrations and wall pressure fluctuations for varying flow rates, gas void fractions, and characteristic bubble sizes. The results show that the presence of bubbles substantially increases both the plate vibrations and the wall pressure fluctuations. The vibrations increase by up to 20 dB compared to the same flow without bubbles. The spectra of vibrations become broad and vary significantly with the characteristic bubble size. The variations with bubble size are consistent with the resonant frequency of the bubbles, indicating that, in addition to changing the compressibility of the medium, individual bubbles act at sources.

Direct Measurements of Turbulent Boundary Layer Wall Pressure Wavenumber-Frequency Spectra

1998 ◽  
Vol 120 (1) ◽  
pp. 29-39 ◽  
Author(s):  
B. M. Abraham ◽  
W. L. Keith
Keyword(s):  
Boundary Layer ◽  
Pressure Fluctuations ◽  
Pressure Sensors ◽  
Streamwise Velocity ◽  
Accurate Estimate ◽  
Wall Pressure ◽  
Frequency Spectra ◽  
Wall Pressure Fluctuations ◽  
Direct Measurements ◽  
Displacement Thickness

Direct measurements of streamwise wavenumber-frequency spectra of turbulent wall pressure fluctuations were made in an acoustically quiet water tunnel. A linear array of evenly spaced flush mounted pressure sensors was used to measure the wall pressure field at 48 streamwise locations. This array provided over 24 dB of resolution (sidelobe rejection) in the wavenumber domain, leading to an accurate estimate of the “convective ridge” and part of the subconvective and low wavenumber portions of the spectrum at discrete frequencies. Boundary layer parameters, including the mean wall shear stress, boundary layer thickness, displacement thickness, and momentum thickness, were derived from mean streamwise velocity measurements for 8100 < Rθ < 16,700. Time and length scales derived from these parameters were used to nondimensionalize the measured spectra. The effectiveness of different scalings for nondimensionalizing the low and convective wavenumber regions at discrete frequencies was evaluated.

Predicting Turbulent Boundary Layer Wall Pressure Fluctuations in Adverse Pressure Gradients

2005 ◽  
Author(s):  
Frank J. Aldrich
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Pressure Gradient ◽  
Pressure Fluctuations ◽  
Adverse Pressure Gradient ◽  
Wall Pressure ◽  
Prediction Tool ◽  
Pressure Gradients ◽  
Wall Pressure Fluctuations ◽  
The Difference

A physics-based approach is employed and a new prediction tool is developed to predict the wavevector-frequency spectrum of the turbulent boundary layer wall pressure fluctuations for subsonic airfoils under the influence of adverse pressure gradients. The prediction tool uses an explicit relationship developed by D. M. Chase, which is based on a fit to zero pressure gradient data. The tool takes into account the boundary layer edge velocity distribution and geometry of the airfoil, including the blade chord and thickness. Comparison to experimental adverse pressure gradient data shows a need for an update to the modeling constants of the Chase model. To optimize the correlation between the predicted turbulent boundary layer wall pressure spectrum and the experimental data, an optimization code (iSIGHT) is employed. This optimization module is used to minimize the absolute value of the difference (in dB) between the predicted values and those measured across the analysis frequency range. An optimized set of modeling constants is derived that provides reasonable agreement with the measurements.

The scaling of the wall pressure fluctuations in polymer-modified turbulent boundary layer flow

2000 ◽  
Vol 108 (1) ◽  
pp. 71-75 ◽  
Author(s):  
Timothy A. Brungart ◽  
Wayne J. Holmberg ◽  
Arnold A. Fontaine ◽  
Steven Deutsch ◽  
Howard L. Petrie
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Boundary Layer Flow ◽  
Pressure Fluctuations ◽  
Wall Pressure ◽  
Wall Pressure Fluctuations ◽  
Turbulent Boundary Layer Flow ◽  
Layer Flow
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