Viscous Flow and Boundary Layers

Houghton, E.L.; Carpenter, Peter W.; Collicott, Steven H.; Valentine, Daniel T.

doi:10.1016/b978-0-08-100194-3.00003-1

Cited by 4 publications

(2 citation statements)

References 9 publications

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“…This is about 14.2% below the value 1.27 obtained from the momentum-integral analysis for Prandtl’s 1/7th velocity profile for flow over a flat plate. 32 The TBL thickness, however, decreases with Re a . In this context, it may be mentioned that Lueptow et al 31 identified that a 5° misalignment of a cylinder with the free stream direction results in a significant variation in δ/ a .…”

Section: Resultsmentioning

confidence: 97%

Numerical prediction of flow noise levels on towed sonar array

Karthik

Jeyakumar

Sebastin

2020

Proceedings of the Institution of Mechanical Engineers, Part M:

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Flow noise originating in the turbulent boundary layer (TBL) often severely limits the performance of towed sonar array. Therefore, it is necessary to predict this noise for the design of an efficient towed array. This paper presents large eddy simulation methodology to establish the TBL properties and wall pressure fluctuations on a 12 m long towed array with length to diameter ratio of 1200 in the operating tow speed range of 2 to 5 knots in water. The computed flow noise levels are compared with experimental measurements available in the literature successfully. The effectiveness of scaling the flow noise spectra with the diameter and tow speed is discussed, and non-dimensional wall pressure spectra presented with respect to non-dimensional frequency. The overall sound pressure levels are also compared with experimental data that show good accuracy achieved by the proposed numerical methodology.

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Section: Resultsmentioning

confidence: 97%

Numerical prediction of flow noise levels on towed sonar array

Karthik

Jeyakumar

Sebastin

2020

Proceedings of the Institution of Mechanical Engineers, Part M:

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“…During a flight with sufficiently high subsonic speeds, the flow speed on the wing's upper surface can be supersonic due to acceleration through the curvature-created suction, thereby forming a shock wave in a -shape. Further complicated phenomena are also observed by the presence of the transonic flow such as the interaction between -shock and the boundary layer flow [1][2][3]. These phenomena relate to flow separation, thus causing a negative effect on lift production of the wing [4][5].…”

Section: Introductionmentioning

confidence: 99%

Parametric Study on Wing-Lambda-Shock Formation

Chainok

Rungroch

Chairach

et al. 2021

Volume 1: Aerospace Engineering Division Joint Track; Computational Fluid Dynamics

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It is well-known that a wing is one of the most important parts of an aircraft as it is used to generate lift force. According to a wing moving at sufficiently high subsonic speeds, the flow speed on the wing’s upper surface can be supersonic due to acceleration through the curvature-created suction, thereby forming a shock wave in a lambda shape. Additionally, the lambda shock can interact with the boundary layer flow. These phenomena relate to disturbances in the flow field, including flow separation, thus causing undesirable effects on lift production. Hence, a better understanding of the phenomenon of wing-lambda-shock formation and its nature is essential. This study presents a numerical investigation of the lambda-shock formation on an ONERA M6 wing, which is known as a swept, semi-span wing with no twist, under parametric effects of angle-of-attack, and free-stream Mach number, which is increased up to the supersonic regime. The pressure coefficients obtained by simulations are validated by open data. Then, numerical results in terms of the local pressure coefficient, local Mach number, averaged lift and drag coefficients, and λ-shape characteristics based on Mach number and pressure coefficients are discussed under an investigated range of the parameters. Results show that the angle-of-attack and free-stream Mach number can affect the lambda shock formation on the wing upper surface physically. Specifically, an iso-sonic surface with lambda shock waves is disturbed when the angle-of-attack and free-stream Mach number vary in an investigated range. This also affects lift and drag coefficients of the wing.

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Numerical investigation on aerodynamic noise of flow past a cylinder with different spanwise lengths

2023

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A numerical investigation is conducted on aerodynamic noise of flow past a circular cylinder with different spanwise lengths (0.5πD, πD, 2πD, 4πD) at Re = 10, 000, where D is the diameter of the cylinder. The near-field pressure and velocity fields are predicted through Large Eddy Simulation (LES), then the acoustic analogy is used to obtain the far-field noise. The results show good agreements for both the near and far-field with the data from in-house experiments and the literature. Though the spanwise length has limited influence on the power spectral density of the near-field velocity and pressure fluctuations at different spanwise locations, substantial differences are observed for the spanwise pressure coherence and near-wake structures. The 0.5πD case shows primarily two-dimensional flow features immediately behind the cylinder compared to the other three cases, resulting in the overprediction of the spanwise pressure coherence, which has strong implications for the far-field noise prediction. With the spanwise length correction, the differences in overall noise magnitudes of the different cases diminish. Nevertheless, the 2πD and 4πD cases better capture the first and second harmonics of the vortex shedding and its associated directivities than the other two cases, showing the importance of sufficient spanwise lengths in predicting noise from flow past a cylinder.

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Viscous Flow and Boundary Layers

Cited by 4 publications

References 9 publications

Numerical prediction of flow noise levels on towed sonar array

Numerical prediction of flow noise levels on towed sonar array

Parametric Study on Wing-Lambda-Shock Formation

Numerical investigation on aerodynamic noise of flow past a cylinder with different spanwise lengths

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