Effects of Surface Irregularity on Turbulent Boundary Layer Wall Pressure Fluctuations

1984 ◽  
Vol 106 (3) ◽  
pp. 343-350 ◽  
Author(s):  
T. M. Farabee ◽  
M. J. Casarella
Keyword(s):  
Spectral Density ◽  
Flat Plate ◽  
Pressure Field ◽  
Pressure Fluctuations ◽  
Low Frequency ◽  
Velocity Profiles ◽  
Wall Pressure ◽  
Surface Irregularity ◽  
Wall Pressure Fluctuations ◽  
Frequency Components

Measurements were made of the mean velocity profiles and wall pressure field upstream and downstream of the flow over both a backward-facing and forward-facing step. For each configuration the velocity profiles show that the effects of the separation-reattachment process persist more than 24 step heights downstream of the step. Extremely high values of the RMS wall pressure are measured near reattachment. These values are 5 and 10 times larger than on a smooth flat plate for the backward-facing step and the forward-facing step, respectively. The spectral density of the wall pressure fluctuations in the recirculation region is dominated by low frequency components. Downstream of reattachment there is a reduction in the low frequency content of the wall pressures and an increase in the high frequency components. At the farthest measured position downstream, the spectral density is still higher than that found on a smooth flat plate. These results show that the complex turbulent flow generated by a surface irregularity can significantly increase the localized wall pressure field and these increases persist far downstream of the irregularity. Consequently, a surface irregularity can be a major source of turbulence-induced vibrations and flow noise, as well as a cause of the inception of cavitation in marine applications.

An Experimental Study of the Flow and Wall Pressure Field Around a Wing-Body Junction

1986 ◽  
Vol 108 (3) ◽  
pp. 308-314 ◽  
Author(s):  
M. A. Z. Hasan ◽  
M. J. Casarella ◽  
E. P. Rood
Keyword(s):  
Pressure Gradient ◽  
Pressure Field ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Low Frequency ◽  
Adverse Pressure Gradient ◽  
Horseshoe Vortex ◽  
Wall Pressure ◽  
Frequency Content ◽  
Wall Pressure Fluctuations

The flow and wall-pressure field around a wing-body junction has been experimentally investigated in a quiet, low-turbulence wind tunnel. Measurements were made along the centerline in front of the wing and along several spanwise locations. The flow field data indicated that the strong adverse pressure gradient on the upstream centerline causes three-dimensional flow separation at approximately one wing thickness upstream and this induced the formation of the horseshoe root vortex which wrapped around the wing and became deeply embedded within the boundary layer. The wall-pressure fluctuations were measured for their spectral content and the data indicate that the effect of the adverse pressure gradient is to increase the low-frequency content of the wall pressure and to decrease the high-frequency content. The wall pressure data in the separated region, which is dominated by the horseshoe vortex, shows a significant increase in the low-frequency content and this characteristic feature prevails around the corner of the wing. The outer edge of the horseshoe vortex is clearly identified by the locus of maximum values of RMS wall pressure.

Measurements of Fluctuating Wall Pressure for Separated/Reattached Boundary Layer Flows

1986 ◽  
Vol 108 (3) ◽  
pp. 301-307 ◽  
Author(s):  
T. M. Farabee ◽  
M. J. Casarella
Keyword(s):  
Boundary Layer ◽  
Pressure Field ◽  
Pressure Fluctuations ◽  
Plate Boundary ◽  
Low Frequency ◽  
Wall Pressure ◽  
Boundary Layer Flows ◽  
Backward Facing Step ◽  
Wall Pressure Fluctuations ◽  
Layer Flow

Measurements were made of the wall pressure field beneath separated/reattached boundary layer flows. These flows consisted of two types; flow over a forward-facing step and flow over a backward-facing step. Wall pressure fluctuations from an equilibrium flat plate boundary layer flow were also measured and used as a baseline for comparative purposes. Values of the RMS fluctuating pressure as well as the frequency spectral density, phase velocity, and coherence of the surface pressure field were measured at various locations upstream and downstream of the steps. The experimental results show that the separation-reattachment process produces large-amplitude, low-frequency pressure fluctuations. The measured spectral statistics of the wall pressure fluctuations are consistent with the view that at reattachment there exists a region of coherent highly energized velocity fluctuations located near the wall which, as it convects downstream, decays and diffuses away from the wall. This energized region remains identifiable in the wall pressure statistics as far as 72 step heights downstream of the backward-facing step.

Pressure and velocity measurements of an incompressible moderate Reynolds number jet interacting with a tangential flat plate

2015 ◽  
Vol 770 ◽  
pp. 247-272 ◽  
Author(s):  
A. Di Marco ◽  
M. Mancinelli ◽  
R. Camussi
Keyword(s):  
Reynolds Number ◽  
Flat Plate ◽  
Scaling Laws ◽  
Pressure Fluctuations ◽  
Wall Pressure ◽  
Theoretical Modelling ◽  
Wall Pressure Fluctuations ◽  
Moderate Reynolds Number ◽  
The Mean ◽  
Pressure And Velocity Measurements

The statistical properties of wall pressure fluctuations generated on a rigid flat plate by a tangential incompressible single stream jet are investigated experimentally. The study is carried out at moderate Reynolds number and for different distances between the nozzle axis and the flat plate. The overall aerodynamic behaviour is described through hot wire anemometer measurements, providing the effect of the plate on the mean and fluctuating velocity. The pressure field acting on the flat plate was measured by cavity-mounted microphones, providing point-wise pressure signals in the stream-wise and span-wise directions. Statistics of the wall pressure fluctuations are determined in terms of time-domain and Fourier-domain quantities and a parametric analysis is conducted in terms of the main geometrical length scales. Possible scaling laws of auto-spectra and coherence functions are presented and implications for theoretical modelling are discussed.

Turbulent Pressure-Velocity Measurements in a Fully Developed Concentric Annular Air Flow

1983 ◽  
Vol 105 (3) ◽  
pp. 345-354 ◽  
Author(s):  
R. J. Wilson ◽  
B. G. Jones
Keyword(s):  
Velocity Field ◽  
Pressure Field ◽  
Air Flow ◽  
Pressure Fluctuations ◽  
Core Region ◽  
Flow Channel ◽  
Wall Pressure ◽  
Analysis Method ◽  
Local Pressure ◽  
Wall Pressure Fluctuations

An experimental study of the fluctuating velocity field and the fluctuating static wall pressure in an annular turbulent air flow system with a radius ratio of 4.314 has been conducted. The study included direct measurements of the mean velocity profile, turbulent velocity field and fluctuating static wall pressure from which the statistical values of the turbulent intensity levels, power spectral densities of the turbulent quantities, and the cross-correlation between the fluctuating static wall pressure and the fluctuating velocity field in the core region of the flow were obtained. The effect of the turbulent core region of the flow on the wall pressure fluctuations was studied by cross-correlating the axial and radial velocity components with the wall pressure fluctuations. A three-sensor, signal subtraction data analysis method using coherence techniques was developed to separate the superimposed local pressure fluctuations and acoustically transmitted noise. This analysis method is shown to adequately isolate the local pressure fluctuation information at each wall of the flow channel. The results of the experimental measurements are compared with existing experimental and numerical information on turbulent annular flow fields and wall pressure statistics. The pressure-velocity correlation indicates that a substantial contribution to the pressure field on the wall of the flow channel is from the turbulent core region outside of the boundary layer. The wall pressure field is shown to be significantly different on the two dissimilar walls. The pressure-velocity correlations show that this difference is due to the geometric difference between the dissimilar volumetric sources which contribute to the wall pressure field. The results of this study show that vibration modeling must incorporate the effects of the flow geometry on the wall pressure statistics, which are used as the driving force for flow-induced vibrations.

Simulation of turbulent boundary layer wall pressure fluctuations via Poisson equation and synthetic turbulence

2017 ◽  
Vol 826 ◽  
pp. 421-454 ◽  
Author(s):  
Nan Hu ◽  
Nils Reiche ◽  
Roland Ewert
Keyword(s):  
Flat Plate ◽  
Boundary Layers ◽  
Poisson Equation ◽  
Pressure Fluctuations ◽  
Turbulent Boundary Layers ◽  
Wall Pressure ◽  
Fluctuating Pressure ◽  
Reynolds Number Flow ◽  
Wall Pressure Fluctuations ◽  
Interaction Term

Flat plate turbulent boundary layers under zero pressure gradient are simulated using synthetic turbulence generated by the fast random particle–mesh method. The stochastic realisation is based on time-averaged turbulence statistics derived from Reynolds-averaged Navier–Stokes simulation of flat plate turbulent boundary layers at Reynolds numbers $\mathit{Re}_{\unicode[STIX]{x1D70F}}=2513$ and $\mathit{Re}_{\unicode[STIX]{x1D70F}}=4357$. To determine fluctuating pressure, a Poisson equation is solved with an unsteady right-hand side source term derived from the synthetic turbulence realisation. The Poisson equation is solved via fast Fourier transform using Hockney’s method. Due to its efficiency, the applied procedure enables us to study, for high Reynolds number flow, the effect of variations of the modelled turbulence characteristics on the resulting wall pressure spectrum. The contributions to wall pressure fluctuations from the mean-shear turbulence interaction term and the turbulence–turbulence interaction term are studied separately. The results show that both contributions have the same order of magnitude. Simulated one-point spectra and two-point cross-correlations of wall pressure fluctuations are analysed in detail. Convective features of the fluctuating pressure field are well determined. Good agreement for the characteristics of the wall pressure fluctuations is found between the present results and databases from other investigators.

Wall Pressure Fluctuations During Transition on a Flat Plate

1991 ◽  
Vol 113 (2) ◽  
pp. 255-266 ◽  
Author(s):  
C. J. Gedney ◽  
P. Leehey
Keyword(s):  
Flat Plate ◽  
Pressure Fluctuations ◽  
Plate Boundary ◽  
Wall Pressure ◽  
Source Distribution ◽  
Turbulent Region ◽  
Wall Pressure Fluctuations ◽  
Dynamic Head ◽  
Processing Techniques ◽  
Made In

Detailed measurements of wall pressure fluctuations have been made in the intermittent (laminar-turbulent) region of a flat plate boundary layer. Digital sampling and processing techniques were used. The properties of these pressure fluctuations were found to be similar to the previous measurements made in the fully turbulent region. The measurements were repeated with a single two-dimensional surface roughness on the plate. The only changes in the results were a decrease in the transition Reynolds number from 2 × 106 to 1.6 × 106, and an increase in the decay rate of the longitudinal cross-spectral density magnitude by a factor of about 1.5. Emmons’ (1951) analytical model was applied for two cases: (1) a constant source density downstream of transition and, (2) a line source distribution at transition. Both predicted burst rates as functions of intermittency appreciably higher than measured values. Wall pressure spectra scaled on dynamic head showed a strong dependency on intermittency. This dependency was largely resolved, at least for intermittencies greater than 64 percent, by scaling on turbulent mean shear stress at the wall.

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