Spectral and Temporal Characteristics of Post-Stenotic Turbulent Wall Pressure Fluctuations

1979 ◽  
Vol 101 (2) ◽  
pp. 89-95 ◽  
Author(s):  
W. H. Pitts ◽  
C. F. Dewey
Keyword(s):  
Steady Flow ◽  
Pressure Fluctuations ◽  
Wall Pressure ◽  
Experimental Uncertainty ◽  
Flow Parameters ◽  
Wall Pressure Fluctuations ◽  
Power Spectral ◽  
Fluctuation Amplitude ◽  
Arterial Constriction ◽  
Turbulent Wall

The power spectral density of turbulent wall pressure fluctuations was measured in a tube downstream of a model arterial constriction. The flow parameters were varied from steady flow to conditions simulating human arterial pulsatile flow. Within the experimental uncertainty (±10 percent in characteristic turbulent frequency, fo, and ±25 percent in absolute rms pressure fluctuation amplitude), turbulent flow at the peak of systole produces wall pressure fluctuations identical to those of a steady flow at the same Reynolds number.

Characterization of the Response of a Curved Elastic Shell to Turbulent Boundary Layer

2010 ◽  
Author(s):  
Francesca Magionesi ◽  
Elena Ciappi
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Pressure Gradient ◽  
Pressure Fluctuations ◽  
Wall Pressure ◽  
Scale Model ◽  
Spectral Densities ◽  
Flow Parameters ◽  
Wall Pressure Fluctuations

For the effective operation of sonar system mounted inside the bulbous of a fast ship, it is important to reduce all the possible noise and vibration sources that cause the dome to vibrate thus radiating noise and interfering with sonar sensor response. In particular, pressure fluctuations induced by the turbulent boundary layer on the surface of the sonar dome represent one of the major sources of self-noise for the on board sensors. Calculation of the structural vibrations and of the noise radiated inside the dome requires as a first step the characterization of the frequency spectra of turbulent boundary layer excitation. Most of the literature related to wall pressure fluctuations is devoted to the study of equilibrium turbulent boundary layers on flat plates in zero pressure gradient (ZPG) flow, for which scaling laws for the power spectral densities and empirical models for the cross spectral densities are well established. The turbulent boundary layer on the bulbous can present several differences with respect to the canonical case because of the presence of hull surface curvatures and of the free water surface that produce pressure gradient variation along the bulbous surface. Moreover, hydrodynamic coincidence effects play a markedly different role in the underwater problem than in the aerodynamic problem. Therefore, an experimental campaign was performed in a towing tank to measure wall pressure fluctuations at different locations along a large scale model of a bulbous and to investigate their spectral characteristics in terms of auto and cross spectral densities. Boundary layer mean flow parameters were obtained with a finite volume code solving the Reynolds Averaged Navier Stokes Equations. The auto spectral densities (ASD) of the measured wall pressure fluctuations were scaled using different combinations of inner and outer flow parameters in order to make ASD independent of the tested conditions i.e. of Reynolds number. The modelled load was used as input for a numerical procedure aimed at evaluating the dynamical response of a section of the bulbous under analysis. The validation of this procedure was experimentally obtained through the measurements of the vibrational response of an elastic section inserted into the bulbous model. Moreover, this comparison indirectly provides additional insights on the physics of wall pressure fluctuations for complex flows.

The Wavenumber-Phase Velocity Representation for the Turbulent Wall-Pressure Spectrum

1994 ◽  
Vol 116 (3) ◽  
pp. 477-483 ◽  
Author(s):  
Ronald L. Panton ◽  
Gilles Robert
Keyword(s):  
Scaling Laws ◽  
Flow Direction ◽  
Pressure Fluctuations ◽  
Phase Speed ◽  
Universal Function ◽  
Wall Pressure ◽  
Large Reynolds Number ◽  
Number Range ◽  
Wall Pressure Fluctuations ◽  
Turbulent Wall

Wall-pressure fluctuations can be represented by a spectrum level that is a function of flow-direction wavenumber and frequnecy, Φ (k1, ω). In the theory developed herein the frequency is replaced by a phase speed; ω = ck1. At low wavenumbers the spectrum is a universal function if nondimensionalized by the friction velocity u* and the boundary layer thickness δ, while at high wavenumbers another universal function holds if nondimensionalized by u* and viscosity ν. The theory predicts that at moderate wavenumbers the spectrum must be of the form Φ+ (k+1, ω+ = c+ k+1) = k+1 − 2 P+ (Δc+) where P+ (Δc+) is a universal function. Here Δc+ is the difference between the phase speed and the speed for which the maximum of Φ+ occurs. Similar laws exist in outer variables. New measurements of the wall-pressure are given for a large Reynolds number range; 45,000 < Re = Uoδ/ν < 113,000. The scaling laws described above were tested with the experimental results and found to be valid. An experimentally determined curve for P+ (Δc+) is given.

Sign in / Sign up

Export Citation Format

Share Document