The Wall Pressure Spectrum of High Reynolds Number Rough-Wall Turbulent Boundary Layers

Forest, Jonathan

doi:10.2514/6.2011-2741

Cited by 22 publications

(20 citation statements)

References 32 publications

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“…Willmarth [17] found that the pressure fluctuations on a rough surface increased at all frequencies by the ratio of the mean-square pressure measured on rough surfaces to that on smooth surfaces. Jonathan [27] investigated the wall pressure spectrum beneath rough-wall turbulent boundary layers and found that increasing wall roughness will cause the spectra to rise in the low frequency region, reducing the range of the linear overlap region. Comparing to experiments performed by J.M.Clinch [26] investigating the wall pressure field of a smooth-walled pipe (tolerance of 0.002 in) with fully-developed turbulent flow at various Reynolds numbers, the maximum point in the spectra is found at the lowest frequencies with spectral magnitude then decreasing with increasing frequency.…”

Section: The Mechanism Investigationmentioning

confidence: 99%

In-Situ Modal Response Characterization of Pipe Structures Through Reynolds Number Variation

Chen

Hugo

Park

2018

Volume 3: Operations, Monitoring, and Maintenance; Materials and Joining

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The modal response characterization of structures is a proven and reliable technique used to monitor system behavior and change, providing information for condition assessment and damage identification. In traditional modal response characterization procedures, an external mass excitation source is used to excite the system, and this is modeled as an impact function. This provides system forcing across a broad range of frequencies. In this investigation, an in-situ method of system excitation is explored. The modal characteristics of externally-supported pipe structures are investigated by varying the flow Reynolds number (Red). Given the increase in flow turbulence with Reynolds number, hydrodynamic pressure fluctuations on the pipe wall provide a varying excitation source. This removes the requirement for an external excitation source. A comparative analysis of data sets collected for both Acrylic and ABS pipe material show similar pressure spectra, while vibration spectra change significantly. Pressure spectra reveal a character whereby the spectral energy increases with increasing Reynolds number. A comparison of in-situ results to those obtained using traditional impact response tests show that vibration spectra collected through Reynolds number variation successfully capture the modal characteristics of the pipe-structure.

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Section: The Mechanism Investigationmentioning

confidence: 99%

In-Situ Modal Response Characterization of Pipe Structures Through Reynolds Number Variation

Chen

Hugo

Park

2018

Volume 3: Operations, Monitoring, and Maintenance; Materials and Joining

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“…The false wall was custom built for previous research efforts by Forest (2012). The wall consists of six 13 mm thick Lexan panels each 1.78 x 1.22 meters.…”

Section: False Wallmentioning

confidence: 99%

Rotor Inflow Noise Caused by a Boundary Layer: Inflow Measurements and Noise Predictions

Morton

Devenport

Alexander

et al. 2012

18th AIAA/CEAS Aeroacoustics Conference (33rd AIAA Aeroacoustics Conference)

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A rotor immersed in a thick turbulent boundary layer produces unsteady loading on the blades which generates unwanted noise and vibration. Two point velocity fluctuations were measured in detail to determine the full four-dimensional correlation function of a boundary layer generated over a smooth wall in the Virginia Tech Stability Wind Tunnel. The correlation function reveals anisotropy in the flow dominated by a large scale correlation structure elongated in the streamwise direction and inclined relative to the wall. This correlation function was then evaluated in the blade frame of reference of an idealized 10 bladed rotor partially immersed in the flow. Blade to blade upwash coherence shows significant asymmetry which is a direct result of the anisotropy of the flow. Using a newly developed theory, the correlation function was used to predict the far-field radiated noise from the rotor at various operating and flow conditions. Predictions show the sound field is dominated by the effects of "haystacking" which is further increased with the inclusion of the presence of the wall. Directivity predictions suggest the far-field sound field acts like a monopole/dipole combination.iii

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“…Understanding the behavior of the single-point spectrum is crucial in examining how certain regions and sizes of coherent turbulent structures within the boundary layer influence the fluctuating pressure signal and thus structural response of the chamber are also possible with the use of acoustic kevlar walls. These walls allow sound to freely pass through with minimal attenuation and reverberation to then be absorbed by the surrounding chamber walls [32,33]. Anechoic chambers are enclosures with panelized walls (usually 4 inch thick acoustic panels) which are lined with sound attenuating material which is designed to minimize noise background levels inside the chamber.…”

Section: Figure 15mentioning

confidence: 99%

“…Due to the potential for noise sources to contaminate the pressure fluctuation measurements (downstream propagation of control valve noise, air expansion out of tanks, panel vibrations, etc.) which are difficult to remove, a method for filtering out noise in the measurements outlined by Forest [33] was employed. This method is similar in nature to other spectral or temporal signal subtraction methods used to isolate the contributions due solely to the TBL.…”

Section: Noise Cancellation Techniquesmentioning

confidence: 99%

“…a second flow conditioning screen may not be needed if acceptable turbulence metrics are achieved in the test section). Another more robust method is to implement closed test section walls around the test panel using acoustically transparent material such as Kevlar (this type of set-up has been studied and implemented in various aeroacoustic facilities such as the one at Virginia Polytechnic Institute and State University [33,46] which is shown in Figure 7.1). Implementing a closed wall test section would lower pressure losses in the test section and would also lower the test section static pressure significantly to be able to achieve the same governed flow speeds at a lower required test section total pressure and mass flow rate.…”

Section: Control System and Instrumentation Improvementsmentioning

confidence: 99%

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The Design, Fabrication, and Commissioning of a High-Speed Aeroacoustic Wind Tunnel for Studies of Surface Pressure Fluctuations Beneath Turbulent Boundary Layers

Giardino¹

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The High-Speed Aeroacoustic Wind Tunnel (HSAWT) at Carleton University is a newly commissioned facility with the purpose of facilitating experimental studies of Turbulent Boundary Layer (TBL) induced surface pressure fluctuations. This research is intended for applications regarding aircraft noise generation from structures exposed to high-speed flow. This open-jet, blowdown facility is unique in Canada and one of a few aeroacoustic wind tunnels in the world capable of achieving speeds up to Mach 0.8. The details of the complete design and fabrication methodology for all wind tunnel duct components, control system hardware, and instrumentation systems is discussed; along with the numerical simulations performed in the validation of the designed components. Preliminary experimental flow measurements and characterization of the wind tunnel control system is examined. The results of initial measurements of TBL surface pressure fluctuations developed over a flat test section plate are compared with established data and empirical models in literature. iv Acknowledgements First and foremost, I would like to thank my thesis and research supervisor, Professor Joana Rocha, for her support and invaluable guidance provided throughout my entire Master's Degree program. Our countless free and open discussions during research meetings has helped me to develop a better understanding and appreciation regarding the complex topics of fluid mechanics and aeroacoustics. I have no doubt that my experiences the past couple of years as a part of her research team will benefit me in my future career initiatives and endeavors.

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The Wall Pressure Spectrum of High Reynolds Number Rough-Wall Turbulent Boundary Layers

Cited by 22 publications

References 32 publications

In-Situ Modal Response Characterization of Pipe Structures Through Reynolds Number Variation

In-Situ Modal Response Characterization of Pipe Structures Through Reynolds Number Variation

Rotor Inflow Noise Caused by a Boundary Layer: Inflow Measurements and Noise Predictions

The Design, Fabrication, and Commissioning of a High-Speed Aeroacoustic Wind Tunnel for Studies of Surface Pressure Fluctuations Beneath Turbulent Boundary Layers

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