Flow-Induced Noise and Vibration in Aircraft Cylindrical Cabins: Closed-Form Analytical Model Validation

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
Joana da Rocha ◽  
Afzal Suleman ◽  
Fernando Lau
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Turbulent Flow ◽  
Closed Form ◽  
Experimental Studies ◽  
Interior Noise ◽  
Analytical Models ◽  
Simply Supported ◽  
Aircraft Cabin ◽  
Flow Induced Noise

The turbulent boundary layer is a major source of interior noise in transport vehicles, mainly in aircraft during cruise flight. Furthermore, as new and quieter jet engines are being developed, the turbulent flow-induced noise will become an even more important topic for investigation. However, in order to design and develop systems to reduce the cabin interior noise, the understanding of the physical system dynamics is fundamental. In this context, the main objective of the current research is to develop closed-form analytical models for the prediction of turbulent boundary-layer-induced noise in the interior of aircraft cylindrical cabins. The mathematical model represents the structural-acoustic coupled system, consisted by the aircraft cabin section coupled with the fuselage structure. The aircraft cabin section is modeled as a cylindrical acoustic enclosure, filled with air. The fuselage structure, excited by external random excitation or by turbulent flow, is represented through two different models: (1) as a whole circular cylindrical shell with simply supported end caps and (2) as a set of individual simply supported open circular cylindrical shells. This paper presents the results obtained from the developed analytical framework and its validation through the successful comparison with several experimental studies. Analytical predictions are obtained for the shell structural vibration and sound pressure levels, for the frequency range up to 10,000 Hz.

Prediction of Turbulent Flow-Induced Noise in Aircraft Cabins

2010 ◽  
Author(s):  
Joana da Rocha ◽  
Afzal Suleman ◽  
Fernando Lau
Keyword(s):  
Turbulent Flow ◽  
Analytical Model ◽  
Sound Pressure ◽  
Real Life ◽  
Interior Noise ◽  
Analytical Models ◽  
Aircraft Cabins ◽  
Wide Range ◽  
Flow Induced Noise ◽  
Cabin Interior

Flow-induced noise in aircraft cabins can be predicted through analytical models or numerical methods. However, the analytical methods existent nowadays were obtained for simple structures and cabins, in which, usually, a single panel is excited by the turbulent flow, and coupled with an acoustic enclosure. This paper discusses the development of analytical models for the prediction of aircraft cabin noise induced by the external turbulent boundary layer (TBL). The coupled structural-acoustic analytical model is developed using the contribution of both structural and acoustic natural modes. While, in previous works, only the contribution of an individual panel to the cabin interior noise was considered, here, the simultaneous contribution of multiple flow-excited panels is also analyzed. The analytical models were developed for rectangular and cylindrical cabins. The mathematical models were successfully validated through the good agreement with several independent experimental studies. Analytical predictions are presented for the interior sound pressure level (SPL) at different locations inside the cabins. It is shown that identical panels located at different positions have dissimilar contributions to the cabin interior noise, showing that the position of the vibrating panel is an important variable for the accurate prediction of cabin interior noise. Additionally, the results show that the number of vibrating panels significantly affects the interior noise levels. It is shown that the average SPL, over the cabin volume, increases with the number of vibrating panels. The space-averaged SPL is usually accepted to provide the necessary information for the noise prediction. However, in some real life applications, the local sound pressure may be desirable. To overcome this point, the model is also able to predict local SPL values, at specific locations in the cabin, which are also affected by number of vibrating panels, and often differ from the average SPL values. The developed analytical model can be used to study a wide range of different systems involving a cabin coupled with vibrating panels, excited by the TBL. The properties of the external flow, acoustic cabin, and panels, as well as the number of vibrating panels, can be easily changed to represent different systems. These abilities of the model make it a solid basis for future investigations involving the implementation of noise reduction techniques and multidisciplinary design optimization analyzes.

scholarly journals Prediction of Turbulent Boundary Layer Induced Noise in the Cabin of a BWB Aircraft

2012 ◽  
Vol 19 (4) ◽  
pp. 693-705 ◽  
Author(s):  
Joana Rocha ◽  
Afzal Suleman ◽  
Fernando Lau
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Sound Pressure ◽  
Pressure Level ◽  
Interior Noise ◽  
Analytical Models ◽  
Frequency Range ◽  
Noise Levels ◽  
Cabin Noise ◽  
Cabin Interior

This paper discusses the development of analytical models for the prediction of aircraft cabin noise induced by the external turbulent boundary layer (TBL). While, in previous works, the contribution of an individual panel to the cabin interior noise was considered, here, the simultaneous contribution of multiple flow-excited panels is analyzed. Analytical predictions are presented for the interior sound pressure level (SPL) at different locations inside the cabin of a Blended Wing Body (BWB) aircraft, for the frequency range 0–1000 Hz. The results show that the number of vibrating panels significantly affects the interior noise levels. It is shown that the average SPL, over the cabin volume, increases with the number of vibrating panels. Additionally, the model is able to predict local SPL values, at specific locations in the cabin, which are also affected with by number of vibrating panels, and are different from the average values.

Wavenumber Spectra of High Magnitude Wall Pressure Events in a Numerically Simulated Turbulent Boundary Layer

1997 ◽  
Vol 119 (2) ◽  
pp. 281-288
Author(s):  
B. M. Abraham ◽  
W. L. Keith
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Fourier Transforms ◽  
Experimental Studies ◽  
Detection Algorithm ◽  
Wall Pressure ◽  
Negative Events ◽  
Discrete Fourier Transforms ◽  
High Magnitude ◽  
The Time Domain

A method for conditionally sampling the spatial field of the wall pressure beneath a turbulent boundary layer in order to search for high magnitude events and calculate the corresponding wavenumber spectrum is presented. The high magnitude events are found using a simple peak detection algorithm at a fixed instant in time and the wavenumber spectra are calculated using discrete Fourier transforms. The frequency of occurrence for high magnitude positive events is found to be approximately the same as for high magnitude negative events. The contribution of the high magnitude events to the rms wall pressure for various trigger levels is calculated and compared with results from similar experimental studies performed in the time domain. The high magnitude events are shown to occur infrequently and to contribute significantly to the rms wall pressure. Wavenumber spectra from the high magnitude positive and negative events are calculated and compared with the unconditionally sampled spectra. The high magnitude events contain energy focused around a particular stream-wise wavenumber and have high broadband spectral levels.

Wall Pressure Phase Velocity Measurements in a Turbulent Boundary Layer

2012 ◽  
Author(s):  
Teresa S. Miller ◽  
Mark J. Moeller
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Phase Velocity ◽  
Group Velocity ◽  
Noise Source ◽  
Wall Pressure ◽  
Interior Noise ◽  
Convection Velocity ◽  
Phase Velocities ◽  
Wall Pressure Fluctuation

The turbulent boundary layer that forms on the outer surfaces of vehicles can be a significant source of interior noise. In automobiles this is known as wind noise, and at high speeds it dominates the interior noise. For airplanes the turbulent boundary is also a dominant noise source. Because of its importance as a noise source, it is desirable to have a model of the turbulent wall pressure fluctuations for interior noise prediction. One important parameter in building the wall pressure fluctuation model is the convection velocity. In this paper, the phase velocity was determined from the streamwise pressure measurements. The phase velocity was calculated for three separation distances ranging from 0.25 to 1.30 boundary layer thicknesses. These measurements were made for a Mach number range of 0.1 < M < 0.6. The phase velocity was shown to vary with sensor spacing and frequency. The data collapsed well on outer variable normalization. The phase velocities were fit and the group velocity was calculated from the curve fit. The group velocity was consistent with the array measured convection velocities. The group velocity was also estimated by a band limited cross correlation technique that used the Hilbert transform to find the energy delay. This result was consistent with the group velocity inferred from the phase velocities and the array measured convection velocity. From this research, it is suggested that the group velocity found in this study should be used to estimate the convection velocity in wall pressure fluctuation models.

Large-eddy simulation of a three-dimensional shear-driven turbulent boundary layer

2000 ◽  
Vol 423 ◽  
pp. 175-203 ◽  
Author(s):  
CHANDRASEKHAR KANNEPALLI ◽  
UGO PIOMELLI
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Turbulent Boundary Layer ◽  
Turbulent Kinetic Energy ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Quasi Equilibrium ◽  
Mean Flow ◽  
Curvature Effects ◽  
Large Eddy

A three-dimensional shear-driven turbulent boundary layer over a flat plate generated by moving a section of the wall in the transverse direction is studied using large-eddy simulations. The configuration is analogous to shear-driven boundary layer experiments on spinning cylinders, except for the absence of curvature effects. The data presented include the time-averaged mean flow, the Reynolds stresses and their budgets, and instantaneous flow visualizations. The near-wall behaviour of the flow, which was not accessible to previous experimental studies, is investigated in detail. The transverse mean velocity profile develops like a Stokes layer, only weakly coupled to the streamwise flow, and is self-similar when scaled with the transverse wall velocity, Ws. The axial skin friction and the turbulent kinetic energy, K, are significantly reduced after the imposition of the transverse shear, due to the disruption of the streaky structures and of the outer-layer vortical structures. The turbulent kinetic energy budget reveals that the decrease in production is responsible for the reduction of K. The flow then adjusts to the perturbation, reaching a quasi-equilibrium three-dimensional collateral state. Following the cessation of the transverse motion, similar phenomena take place again. The flow eventually relaxes back to a two-dimensional equilibrium boundary layer.

Heat transfer from hypersonic turbulent flow at a wedge compression corner

1972 ◽  
Vol 56 (4) ◽  
pp. 741-752 ◽  
Author(s):  
G. T. Coleman ◽  
J. L. Stollery
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Turbulent Flow ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Separated Flows ◽  
Rate Distribution ◽  
Compression Corner

A hypersonic gun tunnel has been used to measure the heat-transfer-rate distribution over a compression corner under turbulent boundary-layer conditions. Attached, incipient and separated flows are considered. The results are compared with other experimental data and with the predictions of a simple theory.

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