ORCID Profile
0000-0002-0906-6765
Current Organisations
UNSW Sydney
,
UNSW
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Publisher: Cambridge University Press (CUP)
Date: 26-07-2019
DOI: 10.1017/JFM.2019.522
Abstract: This paper presents a combined experimental and large-eddy simulation study to characterise the effect of aspect ratio on the near-wake structure of a square finite wall-mounted cylinder (FWMC). The cylinder aspect ratios (span $L$ to width $W$ ) investigated in the experiments were $1.4\\leqslant L/W\\leqslant 21.4$ and the oncoming boundary-layer thicknesses were $1.3W$ and $0.9W$ at a Reynolds number based on cylinder width of $1.4\\times 10^{4}$ and $1.1\\times 10^{4}$ , respectively. In complementary simulations, the cylinder aspect ratios investigated were 1.4, 4.3, 10 and 18.6. The cylinder wake structure was visualised in three-dimensional space using a vortex core detection method and decomposed to its oscillation modes using the spectral proper orthogonal decomposition (SPOD) technique. A parametric diagram is proposed to predict whether the time-averaged wake structure is a dipole or a quadrupole pattern, based on oncoming boundary-layer height and aspect ratio. Cellular shedding occurs when the aspect ratio is high with up to three shedding cells occurring across the span for aspect ratios $L/W $ . Each of these cells sheds at a distinct frequency, as evidenced by the spectral content of the surface pressure measured on the side face and the near-wake velocity. Amplitude modulation is also observed in the vortex shedding, which explains the litude modulation of the acoustic pressure emitted by square FWMCs. SPOD is shown to be a viable method to identify the occurrence of cellular shedding in the wake.
Publisher: Acoustical Society of America (ASA)
Date: 09-2017
DOI: 10.1121/1.5003651
Abstract: Numerical simulations are used to investigate the noise generated by the passage of a rotor blade past a fixed object (the blade-passage effects), which was studied by simulating a three-bladed rotor that is supported by a vertical cylindrical tower. To isolate the blade-passage effects, no incoming wind was introduced in the simulation. The symmetric blade was set to zero pitch angle relative to the plane of rotation and two blade-tower distances were investigated. The sliding mesh method was used to simulate the rotation of the blades and Curle's acoustic analogy was used to predict the noise generated from the simulated flow data. Intense force fluctuations occur during the interaction on both the tower and the passing blade, and these are the primary sources of blade-passage noise. The contribution of the force fluctuations on the support tower to blade-passage noise, which previously had been ignored, was revealed to be more significant than that of the blades. The numerical model successfully predicts the noise spectra, which are validated by the very good agreement with experimental measurements. The simulations provide a framework to better understand blade–tower interaction noise in various applications.
Publisher: American Institute of Aeronautics and Astronautics
Date: 24-06-0014
DOI: 10.2514/6.2018-3296
Publisher: American Institute of Aeronautics and Astronautics
Date: 24-06-2018
DOI: 10.2514/6.2018-3792
Publisher: Elsevier BV
Date: 03-2019
No related grants have been discovered for Yendrew Yauwenas.