Effect of amplitude and mean angle-of-attack on the boundary layer of an oscillating aerofoil

Soltani, Mohammad Reza; Bakhshalipour, A.

doi:10.1017/s0001924000002670

Cited by 12 publications

(6 citation statements)

References 7 publications

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“…This leads to further delay in transition onset during the pitchup. This is similar to the effect of reduced frequency on the load hysteresis loop that has been previously reported [9,15,16,19]. Also, for oscillation beyond αss (αm = 10 deg), the hysteresis loop for transition onset locations is larger.…”

Section: Resultssupporting

confidence: 88%

“…Also, a new RMS parameter is defined based on the time-frequency analysis of the hot-film signals which could be employed for unsteady transition and relaminarization onset detection. This work follows the previous investigations of Soltani and co-workers [15][16][17][18][19] on explaining the aerodynamic behavior of the current airfoil model in steady and unsteady conditions.…”

Section: Nomenclaturesupporting

confidence: 55%

“…11, one can obtain transition onset and relaminarization points for various oscillation cases.Figure 12presents the variations of the transition point versus angle of attack for the current investigation. The data are compared with those obtained by the Xfoil code and by the previous experimental studies using the same model[15,18]. The results are shown for the static condition, i.e.…”

mentioning

confidence: 97%

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Time-Frequency Analysis and Transitional Boundary Layer Investigation over a Pitching Airfoil

2020

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Transitional boundary layer over a pitching airfoil at low Reynolds number (Re = 2.7×10 5) is experimentally investigated through the space-frequency and time-frequency analyses of hot-film signals. Boundary layer events are visualized based on the spacefrequency and time-frequency plots. The precursor phenomena for turbulent as well as fully separated flows are presented based on the time-frequency analysis. A new technique based on the time-frequency analysis of hot-film signals is presented to measure the transition onset as well as the relaminarization locations. This technique is based on the analysis of highfrequency disturbances of the measured data. Special attention is focused on the spatial/temporal progression of the transition onset and the relaminarization points, compared to the static values, for different oscillation frequencies and amplitudes. Investigations are performed prior to, within and beyond the static stall angle of attack conditions. The results obtained by the new technique will be discussed and compared with the observations from the previous investigators.

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Section: Resultssupporting

confidence: 88%

Section: Nomenclaturesupporting

confidence: 55%

mentioning

confidence: 97%

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Time-Frequency Analysis and Transitional Boundary Layer Investigation over a Pitching Airfoil

2020

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“…Note that the roughness is installed on the upper surface of the model only. As shown in [17], roughness reduces suction peak drastically and extends the separation point towards the leading edge. Figure 4 shows that, as angles of attack increase, ow separation moves towards the leading edge and roughness promotes this.…”

Section: Resultsmentioning

confidence: 85%

Roughness and Turbulence Effects on the Aerodynamic Efficiency of a Wind Turbine Blade Section

2016

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Numerous experiments were conducted on the section of a 660 kw wind turbine blade in a subsonic wind tunnel. The selected airfoil was tested with a clean and distributed contamination roughness surface, with a high and low tunnel turbulence intensity. Surface contamination was simulated by applying 0.5 mm height roughness over the entire upper surface of the airfoil. The surface pressure distribution is measured under a steady and unsteady condition, at three Reynolds numbers; 0.43, 0.85, and 1.3 million, and over a range of angles of attack, AOA=7-19. Unsteady data were acquired by both pitch and plunge-type oscillation of the model about its quarter chord at a reduced frequency of 0.07. Results show that the surface roughness reduces section aerodynamic e ciency and the lift coe cient, but increases the drag coe cient for all Reynolds numbers. The application of roughness reduces the upper surface pressure coe cient and extends a separation region at high angles of attack. Increasing the tunnel turbulence intensity resulted in delay of the stall, an increase of maximum lift coe cient, and smoothness of stall behavior. However, the drag coe cient increased signi cantly. Furthermore, turbulence intensity a ected the predicted power output of the blade.

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“…To the authors knowledge, there is no information regarding the steady or unsteady characteristics of this aerofoil. Therefore, attempts are made to investigate the aerodynamic behaviour of the aerofoil in steady and unsteady situations (12)(13)(14) . The velocity in the wake is measured using the pressure rake and real time data acquisition.…”

Section: Methodsmentioning

confidence: 99%

Measurements of velocity Field in the wake of an oscillating wind turbine blade

Soltani¹,

Mahmoudi

2010

Aeronaut. j.

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Effect of amplitude and mean angle-of-attack on the boundary layer of an oscillating aerofoil

Cited by 12 publications

References 7 publications

Time-Frequency Analysis and Transitional Boundary Layer Investigation over a Pitching Airfoil

Time-Frequency Analysis and Transitional Boundary Layer Investigation over a Pitching Airfoil

Roughness and Turbulence Effects on the Aerodynamic Efficiency of a Wind Turbine Blade Section

Measurements of velocity Field in the wake of an oscillating wind turbine blade

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