Tip vortex flow is crucial in designing and operating several engineering applications. In this work, the effect of tip fins on vortex flow in non-cavitating and cavitating conditions is investigated experimentally. Rectangular hydrofoils with and without fin tips are considered. The hydrofoil is placed in a water tunnel at an angle of attack of α = 15° and the velocity field is measured using laser Doppler velocimetry (LDV) at several plane sections. A high-speed camera is used to visualize the tip vortex cavitation (TVC), and pressure transducers are employed for acoustic measurements. The operational chord Reynolds number (Re) ranges from 3.3 × 10⁵–6.0 × 10⁵. The non-cavitating flow results reveal that Re has no discernible effect on the tip vortex characteristics, although the axial velocity at the tip vortex core is significantly affected (accelerated to 1.25 times the inlet velocity behind the hydrofoil without a fin tip, decelerated by a factor of 0.75 for the hydrofoil with a fin tip). The fin tip slightly reduces the turbulent kinetic energy (TKE) and transversal velocity at the vortex core. The LDV measurements indicate that the tip fin affects the development of the tip vortex. The fin tip increases the dissipation of TKE and axial velocity in the tip vortex core downstream of the hydrofoil by causing chaotic flow mixing. The cavitating flow results indicate that TVC first occurs at a cavitation number of σ = 3.30 and Re = 3.71 × 10⁵ around the tip of both hydrofoils. Leading-edge TVC appears at the tip of the hydrofoil without the fin and develops as Re increases, before interacting and merging with the trailing-edge TVC when Re > 4.18 × 10⁵. There is a peak frequency range of the sound pressure level in the foil without a fin, but this disappears in the case of the fin tip.

Nanofluids are considered to offer significant advantages as thermodynamic fluids because of their admirable properties on thermal conduction, thermal convection, boiling heat transfer and stability. This paper presents numerous researches focusing on the improvement of heat transfer via facing step and corrugated channels using nanofluids and without it. Exploration on the convective heat transfer was done through numerical modeling. It was reported that experimental studies were carried out in corrugated and facing step channels through the application of nanofluids and conventional fluids for heat transfer enhancement. The turbulent and laminar flows along corrugated and facing step channels have been presented. The numerical and experimental findings in maximizing the heat transfer rate are in accord. Comparisons between thermal conductivity measurement methods were done. Innovative design of corrugated facing step channel is being proposed. The heat transfer enhancements reach 60% by using facing step channel under laminar flow with nanofluid. The dimensions of new channel such as height and width of the baffle, the height of the step, shape and height of corrugated are needed to compare that might to provide the ideal rate of heat transfer. Â

The influence of sweep angles on cavitation characteristics and mechanisms of a wedge-section hydrofoil is investigated experimentally and numerically. Four hydrofoils with sweep angles of 0° (straight), 30°, 45°, and 60° are considered across a range of cavitation numbers from 2.00 to 0.48 and angle of attack (AOA) of 0°, 5°, 10°, and 15°. Two high-speed cameras are used to visualize the cavitation flow in a high-speed cavitation tunnel. The numerical simulation is conducted using unsteady Reynolds-averaged Navier–Stokes equations through OpenFOAM. At an AOA of 0° and 5°, vortex cavitation first appears in the wake region of all models at a cavitation number of 0.98. However, at higher AOA values of 10° and 15°, tip-vortex cavitation (TVC) begins first for the straight foil, and this is followed by sheet and wake cavitation. In contrast, the swept foil does not succumb to TVC. Instead, as the sweep angle increases, sheet cavitation develops into root leading-edge vortex cavitation (LEVC). The inclination angle of the LEVC from the leading edge is observed to be between 6° and 15°, depending on the sweep angle, and it is independent of the cavitation number and AOA. The wake vortex changes from eddy vortex shedding at the wake region of the straight hydrofoil into two root trailing-edge vortices as the sweep angle increases. The swept hydrofoil reduces the average cavity volume by more than 45% compared with the straight foil. The lift coefficient of the straight hydrofoil increases as sheet cavitation is generated and reaches a maximum value of 0.6 when cavitation covers the suction side of the hydrofoil before dropping sharply when it extends to the wake region. However, there is only minor deterioration in the lift coefficient of the 60° swept-angle foil when the cavitation occurs. The drag coefficient reduces when cavitation forms for both foils. However, the drag coefficient of the swept hydrofoil is lower than that of the straight foil. These findings offer valuable insight into the design and optimization of foils for various applications where cavitation affects their performance and stability.