computational study

The paper investigates the aerodynamic performance and power requirement characteristics of wing sections integrated with high-lift airfoil to support the operation of solar-powered Unmanned Aerial vehicle (UAV). The flight mission is aimed to simulate the operation of solar-powered UAVs under low -speed environment. The research focuses on studying the aerodynamic effect of non-solar UAV wing model and solar UAV wing model for the varying angle of attack. The UAV wing models are tested using a subsonic wind tunnel to validate the aerodynamic characteristics at low-speed condition. The aerodynamic parameters such as coefficient of lift (Cl), coefficient of drag (Cd), coefficient of pressure (Cp), and the total power required to accelerate the solar UAV are studied to maintain steady level flight.  The solar UAV and non-solar UAV wing models were subjected to a computational process to examine the pressure and velocity distributions for the aerodynamic performance analysis.  Evident results show that the solar cells positioned at the flow separation region of the UAV wing model produces an aerodynamic efficiency rate of 5.45% and required 37.13W of minimum power compared to non-solar UAV at the Reynolds number of 9.8  106.

Wind energy is one of the abundantly available renewable energy resources. Savonius vertical axis wind turbine is better suited for small scale power generation applications with many advantages. The turbine operates independent of wind direction with good starting torque and less noise. But, the power coefficient of the Savonius turbine is less than all other wind turbines. The shape of the turbine blades plays an important role in the performance of the turbine. In this present two-dimensional numerical study, an attempt has been made to improve the turbine performance by considering three types of blade shapes. The complete design details of the proposed new blade shapes are presented. The simulations are carried out using ANSYS Fluent 15.0 with SST K-ω turbulence model. The power coefficient of the modified blade is found to have increased by 20% compared to conventional blade shape. The effect of tip-speed-ratio on power coefficient has also been studied and reported.

A detailed numerical investigation of two different modes of shock wave-turbulent boundary layer interaction (SWBLI) is presented. Equivalence of ramp induced SWBLI (R-SWBLI), and impingement shock based SWBLI (I-SWBLI) is explored from the computational study using an in-house developed compressible flow solver. Multiple flow deflection angles and ramp angles are employed for this study. For all the investigated cases, a freestream Mach number of 2.96 and Reynolds number of 3.47×107m−1 are considered. The k−ε model with the improved wall function of present solver predicted wall pressure distributions and separation bubble sizes very close to the experimental measurements. However, the separation bubble size is slightly over overpredicted by the k−ω model in most of the cases. The effect of overall flow deflection angle and upstream boundary layer thickness on the SWBLI phenomenon is also studied. A nearly linear variation in separation bubble size is observed with changes in overall flow deflection angle and upstream boundary layer thickness. However, the equivalence of SWBLI is noted to be independent of these two parameters. The undisturbed boundary thickness at the beginning of the interaction is identified as the most adequate scaling parameter for the length of the separated region.

Natural or industrial flows of a fluid often involve droplets or bubbles of another fluid, pinned by physical or chemical impurities or by the roughness of the bounding walls. Here we study numerically one drop pinned on a circular hydrophilic patch, on an oscillating incline whose angle is proportional to sin(ωt). The resulting deformation of the drop is measured by the displacement of its center of mass, which behaves similarly to a driven over-damped linear oscillator with amplitude A(ω) and phase lag φ(ω). The phase lag is O(ω) at small ω like a linear oscillator, but the amplitude is O(ω−1) in a wide range of large ω instead of O(ω−2) for a linear oscillator. A heuristic explanation is given for this behaviour. The simulations were performed with the software Comsol in mode Laminar Two-Phase Flow, Level Set, with fluid 1 as engine oil and fluid 2 as water.