Flow modification around a circular cylinder applying splitter plates

A number of different studies were reviewed to investigate the functionality of splitter plates for the purpose of drag reduction and vortex elimination behind a circular cylinder. The studies were carried out numerically or experimentally in different combinations of Reynolds range, 2D or 3D dimensions, with intention of drag reduction, vortex suppression or both. Results were compared to discover the generalities of a splitter plate's applications and its performance in drag reduction and vortex control. The reduction of 12% up to 38.6% in drag coefficient suggests that all reviewed studies verified the effectiveness of upstream plate in drag reduction. Varied upstream plate's gap ratios (gap between the plate and cylinder) were tested and the optimum position was obtained. For the finite cylinder case, however, the studies discovered that the effectiveness of upstream plate decreased severely and thus, are barely considered as a drag reductive tool for shorter cylinders. Although downstream plate influences drag force, its prominent application is found to be vortex shedding elimination (up to 14.7%). The length ratio and gap ratio of downstream plate were varied in these studies and it was found that the length ratio was a more important factor compared with the gap ratio in the case of vortex suppression

Active Vibration Suppression of an elastic piezoelectric sensor and actuator fitted cantilevered beam configurations as a generic smart composite structure

An efficient analytical method for vibration analysis of a Euler–Bernoulli beam with Spring Loading at the Tip has been developed as a baseline for treating flexible beam attached to central-body space structure, followed by the development of MATLAB© finite element method computational routine. Extension of this work is carried out for the generic problem of Active Vibration Suppression of a cantilevered Euler–Bernoulli beam with piezoelectric sensor and actuator attached as appropriate along the beam. Such generic example can be further extended for tackling light-weight structures in space applications, such as antennas, robot’s arms and solar panels. For comparative study, three generic configurations of the combined beam and piezoelectric elements are solved. The equation of motion of the beam is expressed using Hamilton’s principle, and the baseline problem is solved using Galerkin based finite element method. The robustness of the approach is assessed

Study on start-up characteristics of H-Darrieus vertical axis wind turbines comprising NACA 4-digit series blade airfoils

Installation of H-type vertical axis wind turbines is in many cases limited by the inherent start-up issues associated with this type of turbine. This could be crucial in environments with low wind speed. The aim of this study is to provide an appropriate CFD modeling setup for investigation of the start-up behavior associated with this class of turbines. For this purpose, a series of transient CFD simulations were carried out using ANSYS Fluent. In contrast with the conventional approach, whereby a constant angular velocity is specified for the rotor, in the present work, the turbine was left free to accelerate based on the torque experienced over time. Careful considerations were made regarding turbulence modeling and grid generation, which are key to ensuring accuracy in this investigation. The result of this simulation, in the form of an accelerating time series, demonstrates good agreement with the published experimental data, and the method yields a high level of accuracy, proving its usefulness for similar problems. In another attempt, the validated CFD setup was utilized to evaluate the effects of several geometric attributes of the turbine rotor on the starting characteristics. Symmetric and cambered airfoils of different thicknesses with a wide range of pitch angles were examined. The optimum start-up characteristics were observed with the use of a medium-thickness cambered airfoil, NACA2418, put to use with an outward pitch angle of 1.5°; this configuration decreased the start-up time while retaining the turbine's peak performance

Conceptual product design methodology through functional analysis

Due to high competitive nature of todays product market, it is essential for conceptual design architecture solution to be derived faster while still maintaining a certain level of innovation to differentiate it from other competing products. This can be a handful task for the development of complex product designs with the current geometrical-based approaches due to plethora of possible physical alternatives to be considered. The search for product design architecture solutions from its functional requirements is more effective as the functional space is comparatively smaller than the physical search space. This allows the design and development effort to be more focused and saves time and resources. With this notion, there is a driving motivation to adapt the functional approach into the conceptual design process to exploit some of its benefits. In this paper, a methodology to derive the product architecture solution from functional approach is discussed and proposed

An overview of passive and active drag reduction methods for bluff body of road vehicles

This paper is an overview of results done on bluff body road vehicle’s base drag reduction either by experimental or numerical methods. Two categories of devices are divided that prove certain degrees of effectiveness in reducing the base drag, namely passive and active. The reduction of drag coefficient achieved in existing research ranging from 5% to 50%, which varies for each method and device. However, the higher the achieved drag reduction is, the greater the compensation required is. The compensation comes in various forms to achieve the desirable drag reduction. For passive drag reduction, hump shaped bluff body with boat-tail shows significant drag reduction by 50.9% compared to the other methods. Meanwhile, one of the potential of active drag reductions is by utilizing rotating cylinder. The rotating can reduce the drag on the bluff body by influencing the separation of boundary layer. The drag can be further reduced by enhancing the rotating cylinder with surface roughness and rotation speed. A notable 23% reduction of drag coefficient using rough surface on bluff body vehicle’s is achieved compared to the smooth surface

Kinematic and aerodynamic modelling of bi- and quad-wing flapping wing micro-air-vehicle

A generic approach to model the kinematics and aerodynamics of flapping wing ornithopter has been followed, to model and analyze a flapping bi- and quad-wing ornithopter and to mimic flapping wing biosystems to produce lift and thrust for hovering and forward flight. Considerations are given to the motion of a rigid and thin bi-wing and quad-wing ornithopter in flapping and pitching motion with phase lag. Basic Unsteady Aerodynamic Approach incorporating salient features of viscous effect and leading-edge suction are utilized. Parametric study is carried out to reveal the aerodynamic characteristics of flapping bi- and quad-wing ornithopter flight characteristics and for comparative analysis with various selected simple models in the literature, in an effort to develop a flapping bi- and quad-wing ornithopter models. In spite of their simplicity, results obtained for both models are able to reveal the mechanism of lift and thrust, and compare well with other work

Numerical analysis using a fixed grid method for cardiovascular flow application

Motivated by the current interest in the numerical simulation of biological flows in the human body, we develop a new method to simulate fluid flow embedded in a solid region. The novelty of this method lies on the use of a fixed grid in the entire computational domain. The formulation is an extension of the multiphase fluid flow that belongs to the category of the penalty method, where high viscosity is imposed on a solid region. A free open source library, namely, OpenFOAM, is used to integrate high order and advanced numerical schemes into these computational formulations. The Monotone Upstream System for Conservation Laws (MUSCL) scheme by van Leer, with a harmonic limiter from the category of the total variation bounded (TVB) scheme, is used for cell face interpolation. The robustness and accuracy of the solver are compared with the benchmark test case, namely, the free fall of a solid sphere. The test case validates that the rigidity of the solid sphere is ensured with the selected high viscosity ratio. The accurate terminal velocity of the falling solid sphere proves the no-slip condition at the solid-liquid interface. As a real application implementation, the flow on a simplified idealized model of heart valve stenosis is presented

Further development of the kinematic and aerodynamic modeling and analysis of flapping wing ornithopter from basic principles

The basis of this work was to understand the generation of lift and thrust of a flapping bi-wing ornithopter, which is influenced by its geometrical, dynamic, kinematic and aerodynamic features by following a generic approach in order to identify and mimic the mechanisms. As further development of earlier work, three-dimensional rigid thin wing is considered in flapping and pitching motion using strip theory and two-dimensional unsteady aerodynamics for idealized wing in pitching and flapping oscillations with phase lag. Later, parametric study is carried out to attain a complete cycle’s lift and thrust physical characteristics for evaluating the plausibility of the aerodynamic model and for the synthesis of an ornithopter model with simplified mechanism. Further investigation is conducted to identify individual contribution of generic motion towards the flight forces. Results are assessed in comparison with existing theoretical and experimental results as appropriate

Review on the cost and performance of a wige craft a commercialization prospective

This study is prepared as an analysis on potential application and commercialization of the wing-in-ground effect craft (WIGE craft) as a new transportation system for domestic market. As the needs analysis and concept exploration phases commonly carried out within the concept development of a new complex system, this study may serve as validation answers to some basic questions such as “Is there a valid need for this new system?”, “Is there a practical approach to satisfying such need?”, “What performance is required?”, and “Is there at least one feasible approach to achieving such performance at an affordable cost?”. The analysis on potential of application and commercialization of WIGE craft would constitute a basis for making a decision as to whether or not to invest in a further development effort. The conducted analysis can be also considered as a “feasibility study”, which in this case has been based on comparison of certain key features of a WIGE craft with those of other existing transportation vehicles that remain offering services as the “proven” alternative concepts. The key features of a WIGE craft should be in the first place in its capabilities, operational effectiveness, and in its performance requirements, which are supposed to achieve the most beneficial balance between capability, operational life, and cost. During the process of study, it has been found that a WIGE craft may fill in the gap between aircrafts and marine vehicles in terms of technological and operational advantages. However, the operational costs of WIGE craft have been found to be relatively higher if compared to those of other existing transport vehicles. Besides, as a matter of fact, a WIGE craft has never reached acceptance as mainstream transport vehicles, because apparently a WIGE craft contains inherent stability problem due to coupled effect of variation in angle of attacks and in altitude above the surface, which require a solid and generic solution. A further development effort beyond this current study would be the engineering development, which commences with the identification and reduction of development risks. Nevertheless, it can be stated that the development of a WIGE craft may give invaluable advantages in the development of new concept and technology

Basic geometries of the new closed circuit wind tunnel of the Universiti Putra Malaysia (UPM)

The existing UPM low speed wind tunnel was usually occupied by students, who carried out their final year projects or postgraduate researches, so that there was hardly free time slot for any additional testing work. Due to this reason, a new wind tunnel project has been started recently. Some basic specifications of the new tunnel have been pre-selected before the project was started, which comprised the following design decisions: a tunnel speed of 50 m/s, a test section area of lxl m2, and a closed circuit tunnel type. It wouldn’t be difficult to perceive that this pre-selection was made based on some of the trade-off results among the project’s options and constraints. This paper is aimed to present a simple analysis on the design of the new tunnel, focusing only on its basic geometries. Some design decisions that have been made related to its basic geometries are analyzed and reported in this paper. This analysis may be considered as a design verification of the new tunnel or even perhaps be regarded as scientific justification for its existence