The Effect of Gurney Flap and Trailing-edge Wedge on the Aerodynamic Behavior of an Axial Turbine Blade

In this research, the effect of Gurney flap and trailing-edge wedge on the aerodynamic behavior of blunt trailing-edge airfoil Du97-W-300 which is equipped with vortex generator is studied. To do this, the role of Gurney flap and trailing-edge wedge on the lift and drag coefficient and also aerodynamic performance of the airfoil is studied. Validation of the numerical model is performed by comparison of the obtained results with those of experiment. Results show that before stall, Gurney flap leads to the increase in the aerodynamic performance in a wider range of angle of attack. Numerical findings reveal that the maximum increment for the aerodynamic performance is obtained at low angle of attack when trailing-edge wedge is employed. It is found that for the highest considered value of Gurney flap and trailing-edge wedge heights, where the highest values for the lift occur, the higher aerodynamic performance at low angle of attack is obtained when trailing-edge wedge is used and at high angle of attack, the Gurney flap results in a higher aerodynamic performance. It is also shown that when high aerodynamic performance is concerned, addition of Gurney flap to the airfoil leads to the higher value for the lift. Doi: 10.28991/HIJ-2021-02-04-03 Full Text: PDF

Study of unsteady cavitating flow around Clark-Y hydrofoil using nonlinear PANS model with near-wall correction

In this paper, we describe the use of a new nonlinear partially-averaged Navier–Stokes (PANS) model with near-wall correction for simulating the cavitating flow around a Clark-Y hydrofoil. For comparison, the standard [Formula: see text]–[Formula: see text] PANS model is also used. The results demonstrate that compared to [Formula: see text]–[Formula: see text] PANS and experiment, the new PANS model shows better performance for cavitation flow, including time-averaged velocity, root mean square (rms) velocity and cavity shedding processing. Through the calculation of the lift and drag coefficient at [Formula: see text] and [Formula: see text], it can be concluded that the cavitation will decrease the lift and increase the drag of the hydrofoil, resulting in a decrease of the lift-to-drag ratio. From the analysis of different terms in both the turbulent kinetic energy (TKE) and dissipation rate transport equations of the cloud cavitation, it is found that the production term and the dissipation term are dominant in the turbulent transport, and they are mainly distributed in the vapor–liquid interface and the trailing edge of the hydrofoil.

Design of Elevons, Wings, and Performance Investigation for A Blended Wing Body UAV

Objectives: To study a hybrid VTOL- Blended wing body design for its wings and elevons and perform CFD simulations with the wings. The steps for designing wing configuration and Elevon positioning involve different variables giving rise to a large number of design possibilities for a control surface. In the current study methods, have been proposed for the selection of optimized wing configuration and elevons positioning and validated with simulations model. Methods: Meta-heuristic methods like genetic algorithms are used for arriving at favorable solutions and Matlab coding is written for the initial draft of wing geometry, selected geometries are iterated in XFLR5 for stability and control, and later validated with simulations around the fluid domain. Elevons are control surfaces generally installed in tailless aircraft at the wing's trailing edge. It applies to roll and pitching force to wings as it combines the functionality of both pitching and rolling control. Design space was mathematically plotted and solved using MATLAB to decide elevons, wing configuration, and their positions.Findings: Initial selection of wing geometry, aoa, and structural design for maneuverability and stability for the enhanced aerodynamic performance of BWB UAV. In this presented paper drag coefficient of the designed BWB UAV comes out to be precisely around 0.02216 using computational modeling. Variation curve of Lift and drag coefficient with aspect ratio and angle of attack. Post-processing results of pressure forces and velocity profile on Wings accurately validate the proposed method of control surface optimization. Novelty: Designed BWB UAV has increased lift to drag ratio, reduced weight of airframe which improves performance. The Design phase is highly iterative, Through this research paper, an attempt has been made to develop a methodology for selection and investigation of control surfaces against requirements that makes BWB UAV more helpful for practical use and increasing the lift and endurance efficiency of the hybrid VTOL- Blended wing body aircraft.

Investigations of Lift and Drag Performances on Neo-Ptero Micro UAV Models

This paper presents the investigation and improvement of lift and drag characteristics of Neo-Ptero micro-UAV models based on the virtual wind tunnel method. Despite its successful development and flight stability, the lift and drag coefficients characteristics of the current Mark 1 Neo-Ptero remain unknown. To improve the Mark 1 Neo-Ptero performances, Mark 2 Neo-Ptero model has given a new unsymmetrical airfoil wing configuration. The computational aerodynamic analysis was executed and focused on certain lift and drag coefficient characteristics. Lift coefficient results showed that Mark 2 improved in overall lift characteristics such as zero-lift angle, maximum lift magnitude and stall angle magnitude. Conversely, Mark 2 model suffered a slightly higher drag coefficient magnitude and more significant drag increment percentage than Mark 1. However, the trade-off between superior lift magnitude and minor drag generation induced by Mark 2 boosts the model’s aerodynamic efficiency performances but is only limited at early angle stages.

CFD Analysis on Aerodynamic Coefficients of Flying Saucer

With the growing of Unmanned Aerial Vehicle (UAV) usage, many new types of UAV are introduced. Flying Saucer is a new type of UAV which is not yet famous in the market. The aim of this study is to analysis the aerodynamic coefficients of a Flying Saucer. The research question arise is What the optimum angle of attack for Flying Saucer flight is. The study is conducted in Computational Fluid Dynamics (CFD) using COMSOL Multiphysics with Laminar Flow physics for several angles of attack. The analysis considers Lift and Drag coefficient in the form of 𝐶𝐿 and 𝐶𝐷 to angle of attack (α) plot, ratio of 𝐶𝐿/𝐶𝐷 to angle of attack (α) plot and drag polar plot. We conclude that a symmetric Flying Sauce has aerodynamic characteristic with the optimum operational angle of attack in the range of 8 to 16 deg. The 𝐶𝐷 and 𝐶𝐿 has a quadratic relationship with large 𝐶𝐷0 due to the geometric of Flying Saucer. It recommends that further study should explore in the area of zero and maximum angle of attack (α) and validation in wind tunnel experiment.

Performance Prediction and Design of Stratospheric Propeller

In this paper, a performance prediction method is proposed for the design of a stratospheric propeller. The Spalart–Allmaras (S–A) model was used to calculate the airfoil performance of FX63, and the polynomial fitting method was utilized to establish the airfoil database of the lift and drag coefficient. A computational fluid dynamics (CFD) model was applied at different altitudes to prove the feasibility of the method. The CFD results were compared with the results of the vortex theory and prediction; the prediction result accuracy was improved compared with that of the vortex theory over a greater range of advance ratios. The airfoil performance data requirements and the number of iterative calculations were reduced. These results indicate that the proposed propeller design meets the requirements of stratospheric airship propulsion systems.

Near Stall Unsteady Flow Responses to Morphing Flap Deflections

The unsteady flow characteristics and responses of an NACA 0012 airfoil fitted with a bio-inspired morphing trailing edge flap (TEF) at near-stall angles of attack (AoA) undergoing downward deflections are investigated at a Reynolds number of 0.62 × 106 near stall. An unsteady geometric parametrization and a dynamic meshing scheme are used to drive the morphing motion. The objective is to determine the susceptibility of near-stall flow to a morphing actuation and the viability of rapid downward flap deflection as a control mechanism, including its effect on transient forces and flow field unsteadiness. The dynamic flow responses to downward deflections are studied for a range of morphing frequencies (at a fixed large amplitude), using a high-fidelity, hybrid RANS-LES model. The time histories of the lift and drag coefficient responses exhibit a proportional relationship between the morphing frequency and the slope of response at which these quantities evolve. Interestingly, an overshoot in the drag coefficient is captured, even in quasi-static conditions, however this is not seen in the lift coefficient. Qualitative analysis confirms that an airfoil in near stall conditions is receptive to morphing TEF deflections, and that some similarities triggering the stall exist between downward morphing TEFs and rapid ramp-up type pitching motions.

Study of a New Type of Flettner Rotor in Merchant Ships

Wind energy is a clean and renewable source of energy. This study seeks to explore the potential for utilising wind power for merchant ships. A new type of Flettner rotor (rotating cylinder) mounted on the superstructure of a ship is proposed and numerically simulated. The construction and installation of the rotating cylinder is designed and a numerical simulation of the ship-mounted cylinder is carried out, using the commercially available CFD code Ansys Fluent to obtain parameters such as lift and drag coefficient of the cylinder in different conditions. Specifically, it is found that the cylinder type superstructure can play a certain role in reducing the effect of friction by comparing traditional and cylindrical superstructures; the rotating cylinder can generate auxiliary thrust for the ship. After analysis, the wind speed around the cylinder and spin ratio will have a direct influence on its thrust effect; there is an inflection point in the lift coefficient with the increase of α; the thrust coefficient (8.63) reaches the maximum environmental wind speed at 10 m/s and spin ratio is 2.5. For the rotating cylinder, the greater the environmental wind, the greater the thrust contribution generated under the same spin ratio conditions. The maximum thrust can reach 750,000 N; the cylinder’s auxiliary propulsion contribution shows a better advantage in α = 2.0. The effective power generated by the cylinder reaches a maximum of 2,240 kW for environmental wind speed = 20 m/s and α = 1.0.

Numerical simulation of icing effect on aerodynamic characteristics of a wind turbine blade

Icing accretion on wind turbine will degrade its performance, resulting in reduction of output power and even leading to accidents. For solving this problem, it is necessary to predict the icing type and shape on wind turbine blade, and evaluate the variation of aerodynamic characteristics. In this paper the icing types and shapes in presence of airfoil, selected from blade of 1.5 MW horizontal-axis wind turbine, are simulated under different ambient temperatures and icing time lengths. Based on the icing simulation results, the aerodynamic characteristics of icing airfoils are simulated, including lift and drag coefficient, lift-drag ratio, etc. The simulation results show that the glaze ice with two horns presents on airfoil under high ambient temperature such as -5?C. When ambient temperatures are low, such as -10?C and -15?C, the rime ices with streamline profiles present on the airfoil. With increase in icing time the lift forces and coefficients decrease, and the drag ones increase. According to the variations of lift-drag ratios of icing airfoil, the aerodynamic performance of airfoil deteriorates in the presence of icing. The glaze ice has great effect on aerodynamic characteristics of airfoil. The research findings lay theoretical foundation for icing wind tunnel experiment.

Numerical Analysis of the Aerodynamic Characteristics of NACA-4312 Airfoil

The aim of the work is to investigate the aerodynamic characteristics such as lift coefficient, drag coefficient, pressure distribution over a surface of an airfoil of NACA-4312. A commercial software ANSYS Fluent was used for these numerical simulations to calculate the aerodynamic characteristics of 2-D NACA-4312 airfoil at different angles of attack (α) at fixed Reynolds number (Re), equal to 5×10^5 . These simulations were solved using two different turbulence models, one was the Standard k-ε model with enhanced wall treatment and other was the SST k-ω model. Numerical results demonstrate that both models can produce similar results with little deviations. It was observed that both lift and drag coefficient increase at higher angles of attack, however lift coefficient starts to reduce at α =13° which is known as stalling condition. Numerical results also show that flow separations start at rare edge when the angle of attack is higher than 13° due to the reduction of lift coefficient.