Abstract
In the present paper, the effect of the proposed T-shape tip on the energy performance, flow patterns and broadband noise sources of a NACA0009 hydrofoil with tip clearance is investigated. The vortex induced by the gap is simulated by means of the SST k-ω turbulence model, and then, the noise generated by dipoles and quadrupoles are analyzed by using the Curle acoustic analogy and Proudman acoustic analogy, respectively. The numerical simulation results agree well with the experimental measurements. Results indicate that three tip shapes, including the half pressure side T-shape model (MPT), the half suction side T-shape model (MST) and the T-shape model (MT), have complex influence on energy performance of the foil. Only the MST model can promote the energy performance of the hydrofoil at all inlet velocities, with the maximum ratio of lift coefficient to drag coefficient increasing by 4.26%. In addition, the ratio of lift coefficient to drag coefficient for MT obviously increases when the inlet velocity is 7.5 m/s, 10 m/s, 12.5 m/s and 15 m/s, and the maximum promotion is 15.21% at 7.5 m/s. The T-shape tip can effectively suppress the tip clearance leakage vortex, which makes the vortex area decrease with a maximum drop of 5.02%. Furthermore, the MPT and MT have good suppression effect on the hydrofoil dipole noise, and reduce the maximum Curle Acoustic Power (AP) of the foil with 2.64% and 3.03%, respectively. The MST model obviously reduces the isosurface area of the Proudman AP by 6.55% for 55 dB.
Highlights
Hydraulic machineries are widely used in modern submarines and warships, such as pumps, duct propulsors and waterjet propulsors, which have attracted the attention of researchers on a worldwide scale [1,2,3,4,5]
The tip leakage flow (TLF) and tip leakage vortex (TLV) is induced by the existence of the gap, which results in pressure drop and energy loss, and leads to cavitation, erosion, vibration and noise [8,9,10,11,12]
The results indicated that the TLF along the aft side of the blade was strong enough to cause sheet cavitation in the gap starting from the pressure side corner
Summary
Hydraulic machineries are widely used in modern submarines and warships, such as pumps, duct propulsors and waterjet propulsors, which have attracted the attention of researchers on a worldwide scale [1,2,3,4,5]. The tip leakage flow (TLF) and tip leakage vortex (TLV) is induced by the existence of the gap, which results in pressure drop and energy loss, and leads to cavitation, erosion, vibration and noise [8,9,10,11,12]. The internal mechanism among TLF, energy loss and radiated noise is waiting to be explored. Considerable experimental investigations have been conducted on the tip leakage flow, cavitation and noise mechanism. Wu et al [13,14] experimentally investigated the cavitation within the gap of a waterjet pump. The results indicated that the TLF along the aft side of the blade was strong enough to cause sheet cavitation in the gap starting from the pressure side corner
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