Arbitrary Lagrangian-Eulerian form of flowfield dependent variation (ALE-FDV) method for moving boundary problems

Flowfield Dependent Variation (FDV) method is a mixed explicit-implicit numerical scheme that was originally developed to solve complex flow problems through the use of so-called implicitness parameters. These parameters determine the implicitness of FDV method by evaluating local gradients of physical flow parameters, hence vary across the computational domain. The method has been used successfully in solving wide range of flow problems. However it has only been applied to problems where the objects or obstacles are static relative to the flow. Since FDV method has been proved to be able to solve many complex flow problems, there is a need to extend FDV method into the application of moving boundary problems where an object experiences motion and deformation in the flow. With the main objective to develop a robust numerical scheme that is applicable for wide range of flow problems involving moving boundaries, in this study, FDV method was combined with a body interpolation technique called Arbitrary Lagrangian-Eulerian (ALE) method. The ALE method is a technique that combines Lagrangian and Eulerian descriptions of a continuum in one numerical scheme, which then enables a computational mesh to follow the moving structures in an arbitrary movement while the fluid is still seen in a Eulerian manner. The new scheme, which is named as ALE-FDV method, is formulated using finite volume method in order to give flexibility in dealing with complicated geometries and freedom of choice of either structured or unstructured mesh. The method is found to be conditionally stable because its stability is dependent on the FDV parameters. The formulation yields a sparse matrix that can be solved by using any iterative algorithm. Several benchmark stationary and moving body problems in one, two and three-dimensional inviscid and viscous flows have been selected to validate the method. Good agreement with available experimental and numerical results from the published literature has been obtained. This shows that the ALE-FDV has great potential for solving a wide range of complex flow problems involving moving bodies

Arbitrary Lagrangian-Eulerian form of flowfield dependent variation (ALE-ADV) method for moving boundary problems

Flowfield Dependent Variation (FDV) method is a mixed explicit-implicit numerical scheme that was originally developed to solve complex flow problems through the use of so-called implicitness parameters. These parameters determine the implicitness of FDV method by evaluating local gradients of physical flow parameters, hence vary across the computational domain. The method has been used successfully in solving wide range of flow problems. However it has only been applied to problems where the objects or obstacles are static relative to the flow. Since FDV method has been proved to be able to solve many complex flow problems, there is a need to extend FDV method into the application of moving boundary problems where an object experiences motion and deformation in the flow. With the main objective to develop a robust numerical scheme that is applicable for wide range of flow problems involving moving boundaries, in this study, FDV method was combined with a body interpolation technique called Arbitrary Lagrangian-Eulerian (ALE) method. The ALE method is a technique that combines Lagrangian and Eulerian descriptions of a continuum in one numerical scheme, which then enables a computational mesh to follow the moving structures in an arbitrary movement while the fluid is still seen in a Eulerian manner. The new scheme, which is named as ALE-FDV method, is formulated using finite volume method in order to give flexibility in dealing with complicated geometries and freedom of choice of either structured or unstructured mesh. The method is found to be conditionally stable because its stability is dependent on the FDV parameters. The formulation yields a sparse matrix that can be solved by using any iterative algorithm. Several benchmark stationary and moving body problems in one, two and three-dimensional inviscid and viscous flows have been selected to validate the method. Good agreement with available experimental and numerical results from the published literature has been obtained. This shows that the ALE-FDV has great potential for solving a wide range of complex flow problems involving moving bodies

A Study on Aerodynamics and Stability Characteristics of a Bell-Shaped Span-Load Wing

The existence of the new bell-shaped span-load wing is said to has the best lift distribution especially comparing to the elliptical wing. Bell-shaped span-load wing is designed by configuring the twist of the wing. However, the information on the aerodynamic and stability characteristics of the bell-shaped span-load wing is limited. Thus, the main purpose of the research is to evaluate the aerodynamic and stability characteristic to strengthen the claim of the capability of bell-shaped span-load wing in producing minimum induced drag. As the research is expected to be beneficial to the aviation design team, detailed information regarding the lift distribution as well as the induced drag produced is analysed at the optimum angle of attack and the results is further explained in this research. The numerical method for the analysis is done by using Lifting Line Theory (LLT) in the XFLR5 software which can analyse the wings of aircraft in terms of its aerodynamic and stability characteristic. Then, the comparison of the aerodynamic characteristics for bell-shaped span-load, elliptical span-load and tapered wing done in this research is to strengthen the appeal made stating that the bell-shaped span-load wing is the best type of wing ever existed and may replace the elliptical wing as the best wing shape with aerodynamically most efficient. The research has proven that along the wingspan, the bell-shaped span-load wing produced the lowest and minimum induced drag when being compared. At the optimum angle of attack of bell-shaped span-load wing, though the lift produced is slightly lower than the elliptical and tapered wing, the difference in the induced drag is obvious as bell-shaped span-load wing produces induced drag that is lower than 0. In other words, starting from the semi span of the wing to the wingtip, the bell-shaped span-load wing managed to be the most aerodynamically efficient wing

Comparison of Flow Topology Between Major Groups of Airfoil with Vortex Shedding

The effect of vortex behavior on airfoil aerodynamic performance has been widely debated for many years, and many research studies have been conducted to examine the relationship. This paper highlights the in-depth study of flow topological processes on major airfoil groups with vortex shedding. It considers various type of corresponding geometries including symmetrical, asymmetrical, thick, and thin airfoils in order to show the differences in flow topology. The study also emphasized the behavior of separation bubbles, vortex shedding and reattachment points. The use of a commercial CFD software for the study gave reliable results within an adequate length of time. The vortex shedding were successfully highlighted either physically or hypothetically. The separation bubble was relatively easier to be identified in all cases of airfoil of interest. The evolution of separation bubble captured by the topology in the case of Eppler 169 was the unique, and involved the break of reattachment point

Distance and Rotational Speed Analysis of Coaxial Rotors for UTHM C-Drone

The prototype of UTHM C-Drone use a coaxial hexacopter concept for its propulsion system. A coaxial rotors consists of two motor and two propellers mounted above each other and aligned in relation to their axis of rotation. The propellers are based on the T-Motor U15XXL KV29 model used in UTHM C-Drone. The distance between the two propellers is usually relative to the radius of the propeller or can be lesser. The objectives for this study are to investigate the effect of distance between upper and lower propeller in a coaxial rotors system and the effect of rotational speed. This study is important to ensure the C-Drone power efficient and capable to lift 180 kg payload. The CAD model of the propeller and coaxial rotors system were designed based on the specification from T-Motor company by Solidworks software and the flow simulations were conducted using Solidworks Flow Simulation module. The total of six CAD models; one for a single propeller and five for coaxial rotors with five difference of distance cases were constructed. For each model, the total thrust was tested from 50% throttle power up to the 90% throttle power. It was found that the coaxial rotors system can generate more thrust than a single propeller but less than double. It was also found that if the lower propeller rotates faster than the upper propeller, the increment of total thrust is very small. However, if the upper propeller rotates faster than the lower propeller, the total thrust increase significantly. For the case of faster upper propeller, as the higher the throttle applied, the thrust increment ratio will decrease, and the efficiency of the thrust produced will be affected. In addition, for same rotation speed, the thrust generated was lesser when both propellers rotate in a same direction compared to when each propeller rotates in the opposite directions of each other

Numerical study of the flow over symmetrical airfoils with ground effects

The paper presents the ground effects on the flow over five NACA symmetrical airfoils by analyzing the coefficients of lift. The unbounded flow over a selected airfoil was first simulated, and the results were validated against the established data in order to validate the method used in obtaining the lift coefficients. In the presence of ground, we kept the angle of attack to be constantly zero throughout the computations. Ground clearances were set based on those for aircrafts whose wing cross sections are the airfoils of interest. ANSYS was used for such numerical computations. We illustrate percentage increment of lift that is inversely proportional to the ground clearance. This work sheds insight on the important parameters that need to be taken into account in the operational of an aircraft

Development and Performance Investigation of a Unique Dual-rotor Savonius-type Counter-rotating Wind Turbine

Wind power is sustainable and prevalent virtually all over the globe. However, the conversion efficiency of the conventional single-rotor wind turbine (SRWT) is still far from satisfactory. The dual-rotor counter-rotating concept is among the reliable techniques used to enhance the efficiency of a wind energy conversion device for its renowned effectiveness. This study aims to investigate the performance of a Savonius dual/twin-rotor system, particularly in low-speed wind conditions while employing the counter-rotating technique. The evaluation of this technique is presented in terms of aerodynamic characteristics, including the power and torque coefficients. The results have shown that the new concept was able to improve the performance of the system extensively and was capable of operating in a lower wind speed condition. Compared to a single-rotor system, an additional 42% more torque was possible owing to the existence of a second rotor in the new system. The results have also revealed that the conversion efficiency of the system has been enhanced substantially. A corresponding average power coefficient of up to 28% was achieved. The present technique is thought to be promising for wind energy conversion systems, including sites with poor wind conditions

The Structural Design and Aerodynamics Analysis for a Hybrid VTOL Fixed-Wing Drone for Parcel Delivery Applications

A number of companies are experimenting with multicopter drones to deliver items to clients. Because electric planes have a restricted range, their flight range is usually constrained. However, if propelled by gasoline, electric multicopters drones can only travel a short distance because to high power consumption and noise difficulties. Despite their lower aerodynamic efficiency than fixed-wing aircraft, multicopters' ability to do vertical take-off and landing (VTOL) makes them ideal delivery vehicles. Hybrid fixed-wing VTOL systems with a tilting system that alters the flight mode could be an upgrade. The goal is to effectively manufacture a fixed-wing drone with appropriate structural design and a functional tilting mechanism that can take off vertically. SolidWorks and SIMNET aero were the two approaches used throughout the design software. The drone's aerodynamic qualities were investigated in order to better understand its behaviour, such as range of flight at a given altitude, stall speed, and maximum lift created, in order to determine the maximum parcel weight the drone can carry. The drone was built using SolidWorks 3D-Solid modelling and SIMNET aero design software. Because it is lightweight and sturdy, the tilting mechanism is 3D printed utilising (Polylactic Acid, PLA). The in-fill can also be changed to modify the strength. Following manufacturing, many test flights were done to investigate the drone's genuine behaviour and improve its performance. The drone's theoretical stall speed was found to be 11.43 m/s at free load and 12.74 m/s with a maximum payload of 500g. For maximum glide, the range calculated 1.2 kilometres. During test flights, the drone yaws to the left at 63.43 degrees at 4.879 degrees per second at 50% throttle. It slanted to the front nose down with a weight of 516 g while support was given at the tip of the left wing. The pitch rate was 2.5 degrees per second without payload and 3.12 degrees per second with the 516g payload. Experimental results that are similar to theoretical outcomes would be obtained with further design and calibration improvements

The Augmentation of a Flight Control Mechanism for a Hybrid Fixed-Wing VTOL Drone for Parcel Delivery

Several companies are experimenting with multicopters drones to deliver packages to customers. Although they are less aerodynamically efficient than fixed-wing aircraft, their ability to do the vertical take-off and landing (VTOL) makes them ideal for delivery services. In this study, two methodologies will be used to build the drone which is software simulation and experimental approach. Software such as SIMNET is used to simulate and design an electronic operation of the drone while Mission Planner is used to setup the flight controller. Electronics layout is done prior to ensure a clear sight of work, components and information through the software. The flight controller used is called Pixhawk which is an open hardware mainly used for drone. The radio control system is also setup to be used as the link to control the flight controller. Flight tests were also performed to study the behavior of the UAV at various percentage of throttle. At 60 percent throttle, the drone yaws continously to the left at 63.43 degrees at 4.879 degrees per second during test flights. With a payload weight of 516g, it tilted to the front nose down, with support provided at the tip of the left wing. With more design and calibration advancements, experimental findings that are similar to theoretical outcomes might be attained. Flight data after each test flight is extracted from the software and analysed for further improvement. The fabrication of complete prototype could not be finished within the stipulated time due to a delay in acquiring new parts such as propeller due to a problem, as well as procuring the appropriate material for the wing. A test of the drone motions including roll, pitch, and yaw, is also carried out using flight charts to validate the suggested design parameter. The drone tends to fly better with the motor turning with the same orientation rather than turning with different orientation due to better stability. This flight chart allows users to choose the best design parameters by determining the length of the wingspan, motor RPM, and propeller diameter that are expected to meet the performance requirements in these three flying motions. The procedure for estimating the UAV's battery usage has also been presented in the flight chart

Computational fluid dynamic (CFD) analysis of parachute canopies design for aludra SR-10 UAV as a parachute recovery systems (PRS)

Unmanned Systems Technology (UST) Aludra SR-10 Unmanned Aerial Vehicle (UAV) was purposely designed for survey and mapping mission. In the early design stage of Aludra SR-10 UAV, skid and belly landing method was used as a recovery method. This type of landing method may encounter a harsh landing on hard soil and gravel, producing high impact momentum on the aircraft body and may cause structural or system damage. To increase the safety of Aludra SR-10 UAV operation, Parachute Recovery System (PRS) are purposely design to replace the belly landing technique for landing method. This study was performed by simulation approach (using Computational Fluid Dynamic, CFD) to analyse an aerodynamic performance for selecting the best canopy design that can produce higher drag during recovery process. This computational study focuses on an aerodynamic flow simulation over threedimensional surface on two different canopy designs (i.e. annular canopy and cruciform canopy), and also focuses on drag coefficient in a steady and turbulent condition. Two‐equation k-ε turbulence flow was modelled by adopting Navier-Stokes numerical equations to simulate aerodynamic characteristics and drag. The computational results with an efficient grid study shows an annular parachute canopy produced highest drag coefficient (1.03) than cruciform parachute canopy (0.91). The findings also highlighted the significance of separation and recirculating flows behind studied geometries, which in turn was responsible in producing the drag. This computational simulation analysis successfully provided a baseline annular parachute design was about 2.41 meter of the nominal diameter was selected as the main parachute which can be applied for this research