Viscous Effects on Turbulent Boundary-Layer Noise of Ship's Sonar Dome in a Water Tunnel

1991 ◽  
Vol 35 (04) ◽  
pp. 331-338
Author(s):  
V. Bhujanga Rao ◽  
P. V. S. Ganesh Kumar ◽  
P. K. Gupta
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Wave Vector ◽  
Analytical Method ◽  
Pressure Fluctuations ◽  
Free Field ◽  
Water Tunnel ◽  
Viscous Effects ◽  
Wall Pressure Fluctuations ◽  
Spectrum Modeling

Turbulent boundary-layer (TBL) wall pressure fluctuations of a body measured in a water tunnel need correction to obtain unbounded free-field values. Besides blockage effects in a tunnel which are easily accounted for, viscous effects on TBL noise are to be evaluated to quantify this correction. An analytical method using suitable wave vector spectrum modeling to estimate the correction needed due to viscous effects is presented. A sonar dome body is considered as a typical example.

Effect of a Downstream Ventilated Gas Cavity on the Spectrum of Turbulent Boundary Layer Wall Pressure Fluctuations

2004 ◽  
Author(s):  
Steven D. Young ◽  
Timothy A. Brungart ◽  
Gerald C. Lauchle
Keyword(s):  
Boundary Layer ◽  
Theoretical Model ◽  
Turbulent Boundary Layer ◽  
Pressure Fluctuations ◽  
Pressure Sensors ◽  
Flow Region ◽  
Wall Pressure ◽  
Water Tunnel ◽  
Wall Pressure Fluctuations ◽  
Gas Cavity

This paper theoretically and experimentally examines the effect of a downstream ventilated gas cavity on the spectrum of turbulent boundary layer wall pressure fluctuations. The theoretical model predicts that the ratio of the point spectrum of the turbulent boundary layer wall pressure fluctuations upstream of a ventilated gas cavity to the blocked point pressure spectrum decays rapidly to zero as the cavity origin is approached and undergoes oscillations in amplitude that relax to unity as the quantity ωx/Uc goes to infinity upstream of the cavity. Here ω is the radian frequency, x is the distance upstream from the cavity origin and Uc is the convection velocity. A water tunnel experiment was performed to investigate the theoretical predictions. Dynamic wall pressure sensors were mounted flush to the surface of a flat plate at various distances upstream from a rearward facing step. Carbon dioxide gas was injected into the separated flow region downstream of the step to form a ventilated cavity. The water tunnel measurements were unable to verify the reduction in the amplitude of the turbulent boundary layer wall pressure fluctuations as the step and cavity were approached but did verify the fundamental oscillation predicted by the theoretical model and its relaxation to unity as ωx/Uc went to infinity upstream of the step and cavity.

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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