Parametric characterization of wall pressure fluctuations induced by a compressible jet flow interacting with a flat plate

2019 ◽  
Author(s):  
Stefano Meloni ◽  
Alessandro Di Marco ◽  
Roberto Camussi ◽  
Matteo Mancinelli
Keyword(s):  
Flat Plate ◽  
Pressure Fluctuations ◽  
Jet Flow ◽  
Wall Pressure ◽  
Wall Pressure Fluctuations ◽  
Compressible Jet

Multivariate and conditioned statistics of velocity and wall pressure fluctuations induced by a jet interacting with a flat plate

2017 ◽  
Vol 823 ◽  
pp. 134-165 ◽  
Author(s):  
Matteo Mancinelli ◽  
Alessandro Di Marco ◽  
Roberto Camussi
Keyword(s):  
Flat Plate ◽  
Large Scale ◽  
Pressure Fluctuations ◽  
Experimental Tests ◽  
Jet Flow ◽  
Wall Pressure ◽  
Scale Model ◽  
Order Moment ◽  
Wall Pressure Fluctuations ◽  
Interaction Phenomenon

The increasing size of aircraft engines is leading to reconsideration of their conventional integration in the under-wing configuration due to the strong interaction between the jet and the airframe components. As a consequence, more insight is needed into the complex mechanisms underlying the interaction phenomenon between the jet flow and a surface. The objective of this paper is to carry out a series of experimental tests on a simplified laboratory-scale model to approach/deepen the problem. This analysis is the continuation of a previous study (Di Marco et al., J. Fluid Mech., vol. 770, 2015, pp. 247–272) on a rigid flat plate installed tangentially to the axis of an incompressible jet. In the present work, the velocity and wall pressure fields were simultaneously measured for different radial distances of the plate from the nozzle axis. Pointwise hot-wire anemometer measurements were carried out to characterize the effect of the plate on the velocity field statistics up to the fourth-order moment. The analysis revealed that the presence of the plate brings about a deflection of the mean aerodynamic field over the surface and a reduction of the turbulence intensity. Wall pressure fluctuations induced by the jet flow over the plate were measured by a linear array of cavity-mounted microphones placed along the streamwise direction. The velocity/pressure cross-statistics are achieved in the time and frequency domains using cross-correlations and Fourier analysis. A wavelet-based conditional sampling procedure is applied as well to characterize the flow signatures related to the velocity and wall pressure fluctuations, revealing that the surface induces the breakdown of the large-scale turbulent structures. The dependence of the multivariate and conditioned statistics on the plate distance from the jet as well as on the streamwise and crosswise probe positions is extensively discussed. Different organized flow motions over the surface are found based on the wall pressure events detected. A scaling criterion for velocity signatures is also presented addressing the governing parameters of the jet–plate interaction phenomenon.

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.

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.

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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