M. Rafiuddin Ahmed

Low Reynolds number airfoil optimization for wind turbine applications using genetic algorithm

Optimization of a low Reynolds number airfoil for use in small wind turbines is carried out using a Genetic Algorithm (GA) optimization technique. With the aim of creating a roughness insensitive airfoil for the tip region of turbine blades, a multi-objective genetic algorithm code is developed. A review of existing parameterization and optimization methods is presented along with the strategies applied to optimize the airfoil in this study. A composite Bezier curve is used to parameterize the airfoil. The resulting airfoil, the USPT2 has a maximum thickness of 10% and shows insensitivity to roughness at the optimized angles and at other angles of attack as well. The characteristics of USPT2 are studies by comparing it against the popular SG6043 airfoil. While a slight loss in lift is noticed for both airfoils, the drag increments due to early transition are noticeable as well. The airfoil is also studied using computational fluid dynamics (CFD) and wind tunnel experiments during free and forced transitio...

A Design Outline for Floating Point Absorber Wave Energy Converters

An overview of the most important development stages of floating point absorber wave energy converters is presented. At a given location, the wave energy resource has to be first assessed for varying seasons. The mechanisms used to convert wave energy to usable energy vary for different wave energy conversion systems. The power output of the generator will have variations due to varying incident waves. The wave structure-interaction leads to modifications in the incident waves; thus, the power output is also affected. The device has to be stable enough to prevent itself from capsizing. The point absorber will give optimum performance when the incident wave frequencies correspond to the natural frequency of the device. The methods for calculating natural frequencies for pitching and heaving systems are presented. Mooring systems maintain the point absorber at the desired location. Various mooring configurations as well as the most commonly used materials for mooring lines are discussed. An overview of scaled modelling is also presented.

Conceptual Design of a 100kW Energy Integrated Type Bi‐Directional Tidal Current Turbine

The development of a tidal current turbine that can extract maximum energy from the tidal current will be extremely beneficial for supplying continuous electric power. The present paper presents a conceptual design of a 100kW energy integrated type tidal current turbine for tidal power generation. The instantaneous power density of a flowing fluid incident on an underwater turbine is proportional to the cubic power of current velocity which is approximately 2.5m/s. A cross‐flow turbine, provided with a nozzle and a diffuser, is designed and analyzed. The potential advantages of ducted and diffuser‐augmented turbines were taken into consideration in order to achieve higher output at a relatively low speed. This study looks at a cross‐flow turbine system which is placed in an augmentation channel to generate electricity bi‐directionally. The compatibility of this turbine system is verified using a commercial CFD code, ANSYSCFX. This paper presents the results of the numerical analysis in terms of pressure, ...

In-situ wave resource assessment near Taveuni, Fiji Islands

A lack of field data, visible dominant wave activity in the northern division of Fiji Islands particularly off the southern coast of Taveuni, and increasing cost of nonrenewable energy sources coupled with associated harmful effects to the environment have led to initial wave energy resource assessment. The present work involved twelve months of on-site wave measurements commencing July 2012. The measured data were compared with a 30 yr hindcast WW3 model data from a joint project between the Bureau of Metrology, Australia (BoM) and The Pacific Australia Climate Change Science and Adaption Planning. The model was used to relate to the site characteristic in terms of significant wave-height and period in representation of Fijis overall wave climate and at the same time validating the model with site measurements. The swell and wind wave components together with its prevailing direction was studied in detail. The calculated average power output was 12 kW/m for an average wave-height of 1 m while a peak wav...

Design and Optimization of a Ducted Marine Current Savonius Turbine for Gun-barrel Passage, Fiji

Marine current energy is a reliable and clean source of energy. Many marine current turbines have been designed and developed over the years. Placement of an appropriately designed duct or shroud around the turbine significantly improves the turbine performance. In the present work, a Ducted Savonius Turbine (DST) is designed and optimized and its performance analysis carried out. The components of ducted Savonius turbines are simple and easily available and can be manufactured in developing countries like Fiji. A scaled-down model of 1/20 of a DST was fabricated and tested in a water stream at a velocity of 0.6 m/s and the results were used to validate the results from a commercial Computational Fluid Dynamics (CFD) code ANSYS-CFX. Finally, a full-scale DST was modeled to study the flow characteristics in the turbine and the performance characteristics. The maximum efficiency of the turbine is around 50% at the tip speed ratio (TSR) of 3.5 and the maximum shaft power obtained is 10 kW at the rated speed of 1.15 m/s and around 65 kW at a free-stream velocity of 2.15 m/s. The stress distribution on the ducted turbine was also obtained.

Airfoil Optimization for Small Wind Turbines Using Multi Objective Genetic Algorithm

Small wind turbines are gaining popularity due to their ability to meet community or domestic needs in isolated areas with relatively easier installation and lower cost than large wind turbines. This study looks at optimizing airfoils for use in small horizontal axis wind turbines. The optimization looks to maximize the lift coefficient (Cl) while minimizing or fixing the drag coefficient (Cd). To satisfy these two objectives a multi–objective genetic algorithm is used. The airfoil is parameterized using a composite Bezier curve with two Bezier segments and 11 control points. Appropriate curvature conditions are implemented at the leading and trailing edge of the airfoil and geometric constraints are applied to maintain the maximum thickness between 8% to 14% of the chord for structural reasons. An existing genetic algorithm (GA) code is modified in C++ to generate suitable airfoils using the 13 control points and pass the coordinates to a solver for analysis. As a result four new airfoils are generated for application in low Reynolds number (Re) flow. The characteristics and suitability of the four airfoils are discussed while comparing them to the popular SG6043 airfoil.Copyright