The Application of Different Tripping Techniques to Determine the Characteristics of the Turbulent Boundary Layer Over a Flat Plate

Silvestri, Anton; Ghanadi, Farzin; Arjomandi, Maziar; Cazzolato, B.; Zander, Anthony C.

doi:10.1115/1.4037675

Cited by 30 publications

(21 citation statements)

References 31 publications

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“…All streamwise velocity measurements throughout this paper were non-dimensionalised using the viscous length scale ( ) and friction velocity ( ). An iterative process defined by Kendall and Koochesfahani [18] and applied by Ghanadi et al [1,2] and Silvestri et al [5,6,19] was used to estimate the friction velocity. The process is explained in more detail by Silvestri et al [5][6][7].…”

Section: Methodsmentioning

confidence: 99%

The Control of a turbulent boundary layer by the application of a micro-cavity array

Silvestri¹,

Jafari²,

Bhat³

et al. 2020

Australasian Fluid Mechanics Conference (AFMC)

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Micro-cavity arrays have been identified as a potential passive device to disrupt and capture sweep events, which are responsible for the Reynolds stresses in the boundary layer. The application of micro-cavity arrays for drag reduction was proposed 10 years ago by the University of Adelaide [1-8] and the present article summarises the findings of its investigation during this time. These results are based on data obtained through comprehensive experimental investigations, which has shown that the application of microcavity arrays can achieve a reduction of up to 16% in turbulence energy production within the wall-bounded turbulent flow at low Reynolds numbers [7]. This reduction of turbulent production can be correlated to a skin friction drag reduction of approximately 3% [9]. In a more recent work, a direct numerical modelling investigation into the shared common backing cavity arrangement has been conducted [8]. The results revealed that a maximum reduction in the wall shear stresses of 7.12% could be achieved, which lasted for a considerable distance downstream of the cavity array.

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Section: Methodsmentioning

confidence: 99%

The Control of a turbulent boundary layer by the application of a micro-cavity array

Silvestri¹,

Jafari²,

Bhat³

et al. 2020

Australasian Fluid Mechanics Conference (AFMC)

Self Cite

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“…Two types of surface roughness elements were investigated in this research: zigzag strips and sharkskin-like trips. Zigzag strips were chosen because they are widely used in wind tunnel tests due to their ease of installation and effectiveness in hastening the boundary layer transition [10,13]. In this study, zigzag strips of 60 • teeth angle, 12 mm width and manufactured by Glasfaser-Flugzeug-Service GmbH were utilized.…”

Section: Surface Roughnessmentioning

confidence: 99%

“…The maximum surface roughness height is determined based on the findings of [10,13,25]. The maximum height is suggested to be equal to the undisturbed boundary layer thickness at the trip position in order to prevent overstimulation of the boundary layer, which leads to a non-canonical turbulent flow.…”

Section: Surface Roughness Heightmentioning

confidence: 99%

“…Wind-turbine and gas-turbine blades erode due to particle impact, resulting in the formation of surface roughness close to the leading edge [11,12]. Previous research has shown that the type of surface roughness and its height have a direct influence on the transition onset and the turbulent boundary layer development [10,[13][14][15][16][17], consequently also affecting the trailing edge noise. Braslow [17] stated that for two-dimensional surface roughness, e.g., zigzag strips, spots of turbulence begin to move forward of the natural position of transition when a critical value of Reynolds number based on the trip height is reached.…”

Section: Introductionmentioning

confidence: 99%

“…A critical parameter in determining which roughness height ( ) to use is its ratio with the undisturbed boundary layer thickness at the trip location ( ) [10,13]. When / is too small it does not introduce enough instabilities in the boundary layer to develop a turbulent flow at the TE [15] and a too high ratio changes the boundary layer characteristics [10,13]. A common practice in wind tunnel tests is to perform velocity sweeps with the same roughness height, as performed by Ye et al [15].…”

Section: Introductionmentioning

confidence: 99%

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Influence of Surface Roughness Geometry on Trailing Edge Wall Pressure Fluctuations and Noise

Santos,

Even,

Botero-Bolívar

et al. 2021

Preprint

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Surface roughness elements are commonly used in wind tunnel testing to hasten the laminarturbulent transition of the boundary layer in model tests to mimic the aerodynamic effects present in the full-scale application. These devices can alter the characteristics of the turbulent boundary layer, such as the spanwise correlation length, the boundary layer thickness, the displacement thickness, etc. This not only affects the aerodynamic performance but also the aeroacoustic characteristics of the tested model. Few studies have investigated the effects of the surface roughness elements on the trailing edge near-and far-field noise. So far, the influence of roughness on the wall pressure fluctuations and spanwise coherence at the trailing edge has been left unexplored. Thus, this research addresses the effects of surface roughness geometries of different heights on the trailing edge wall pressure fluctuations, the spanwise coherence, and the far-field noise. The experiments were performed in the Aeroacoustic Wind Tunnel of the University of Twente adopting zigzag strips and novel sharkskin-like surface roughness installed in a NACA 0012 at zero angle of attack. The tested surface roughness heights ranged from 29% to 233% of the undisturbed boundary layer thickness. The wall pressure fluctuations and the far-field noise were measured for Reynolds numbers from 1.3 × 10 5 to 3.3 × 10 5 .It was observed that the surface roughness affects the low-and high-frequency range of the wall pressure spectrum, with trip heights in the range from 50% to 110% of the undisturbed boundary layer thickness having a slight level increase for low frequencies and no difference for high frequencies. The far-field noise increased for low and high frequencies as the trip height increased. The low-frequency increase is a consequence of the trip effects on the trailing edge wall pressure fluctuations, whereas for high frequencies the increase is due to the noise generated by the trip itself. Moreover, the sharkskin-like trip showed to be an effective tripping device. However, this geometry results in high levels of far-field noise in the high-frequency range.

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Attenuation of sweep events in a turbulent boundary layer using micro-cavities

et al. 2017

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The Application of Different Tripping Techniques to Determine the Characteristics of the Turbulent Boundary Layer Over a Flat Plate

Cited by 30 publications

References 31 publications

The Control of a turbulent boundary layer by the application of a micro-cavity array

The Control of a turbulent boundary layer by the application of a micro-cavity array

Influence of Surface Roughness Geometry on Trailing Edge Wall Pressure Fluctuations and Noise

Attenuation of sweep events in a turbulent boundary layer using micro-cavities

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