Harijono Djojodihardjo

Application of Coandă Jet for Generating Lift of Micro Air Vehicles - Preliminary Design Considerations

Coandă effect, which has been widely utilized in many engineering applications for circulation control, is here reviewed for the design of Coandă Micro-Air-Vehicles (MAVs). Based on the review, a basic spherical configuration is analyzed to obtain the relationship between relevant parameters to the lift that can be produced based on fundamental principles. The results can be used for preliminary design purposes and are discussed in view of existing literature.

Vibration Analysis of a Cantilevered Beam with Spring Loading at the Tip as a Generic Elastic Structure

Although fundamental, vibration of a cantilevered Euler-Bernoulli beam with spring attached at the tip is not found in literatures and is here solved analytically and numerically using finite element approach. The equation of motion of the beam is obtained by using Hamilton’s principle. Finite element method is utilized to write in-house program for the free vibration of the beam. Results show plausible agreements.

An analysis on the lift generation for Coandă micro air vehicles

A mathematical model for lift generation on a doughnut-shaped Coandă micro air vehicle is developed and an analysis on the lift generation due to Coandă effect is carried out utilizing basic principles. A degenerate two-dimensional case is also developed. The results are discussed in view of related analytical and experimental work in the literature.

Application of a Multipole Secondary Source for Propeller Active Noise Control

The commercial feasibility of active noise control (ANC) is very promising due to its capability beyond passive noise control (PNC). To some extent ANC becomes a complement of PNC. The active noise reduction is also capable and beneficial in reducing noise selectively. However, the active noise reduction using a conventional secondary source can become very complicated if a significant noise level reduction is required, since a large number of secondary sources will be needed. The active noise reduction is also less effective for reducing high-frequency noise. With such perspectives, a novel approach has been developed using a multipole secondary source to addressthe problems mentioned. In addition, the multipole secondary source will be used for numerical simulation of noise reduction in of propeller noise source in a free field.

Generic Modeling and Parametric Study of Flapping Wing Micro-Air-Vehicle

The present work is focused on the unsteady aerodynamics of bio-inspired flapping wing to produce lift and thrust for hovering and forward flight. A generic approach is followed to understand and mimic the mechanism and kinematics of ornithopter by considering the motion of a three-dimensional rigid thin wing in flapping and pitching motion, using strip theory and two-dimensional unsteady aerodynamics for idealized wing in pitching and flapping oscillations with phase lag. Parametric study is carried out to obtain the lift, drag, and thrust characteristics within a cycle for assessing the plausibility of the aerodynamic model, and for the synthesis of a Flapping Wing MAV model with simplified mechanism. Other important parameters such as flapping frequency and wing geometry are considered. Results are assessed in comparison with the existing theoretical results.

First principle analysis of Coandă Micro Air Vehicle aerodynamic forces for preliminary sizing

Purpose The purpose of this paper is to reformulate the governing equations incorporating major variables and parameters for the design a Micro Air Vehicle (MAV), to meet the desired mission and design requirements. Design/methodology/approach Mathematical models for various spherical and cylindrical Coandă MAV configurations were rederived from first principles, and the performance measures were defined. To verify the theoretical prediction to a certain extent, a computational fluid dynamic (CFD) simulation for a Coandă MAV generic models was performed. Findings The major variables and parameters of Coandă MAV have been formulated into practical guidelines, which relate the lift (or thrust) produced for certain input variables, particularly the Coandă MAV jet momentum coefficient. The influences of the geometrical parameters are elaborated. Research limitations/implications The present analysis on Coandă jet-configured MAV is focused on the lift generation due to the Coandă jet effect through a meticulous analysis. The effects of viscosity, the Coandă jet thickness, the radius of curvature of the surface and the stability of Coandă jet are not considered and will be the subject of the following work. Practical implications The results obtained can be used for sizing in the preliminary design of Coandă MAVs. Originality/value Physical and mathematical models were developed which can describe the physical phenomena of the flow field near the Coandă MAV surfaces influenced by Coandă jet sheets and for obtaining a relationship between relevant variables and parameters to the lift of practical interest.

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.

A Parametric Study of Interplanetary Mission Using Solar Sail

Solar sailing has been an attractive concept and possibly an alternative mean of space propulsion for decades to come since solar sail spacecrafts can generate thrust without requiring any propellant. While the resulting acceleration is small, the continuous thrust would lead to high speed. The present work serves to demonstrate the potential of solar sail by analyzing the dynamics of a spacecraft utilizing solar sail and by carrying out a parametric study for an interplanetary mission exemplified by specific trajectory to Mars.

Finite Element Computational Modeling and Simulation Studies of Non-Penetrating Impact Using Fundamental Principles

A set of Mindlin plates bonded together is subjected to loading by impact, which is considered to represent a generic engineering structure and is analyzed through numerical simulation. The objective is to identify optimum configuration in terms of loading, structural dimensions, material properties and composite layup associated with micrometeorites impacts on spacecraft that will not penetrate into its structure. Following the algorithm developed for the problem, the work comprises an in-depth analysis of a generic flat plate structure subjected to impact and numerical simulation. The analyses are based on dynamic response with emphasis on the elastic region. The direct numerical simulation is carried out in parallel for the analysis, synthesis, parametric study and optimization. As simulation case study, the panel structure response to impact loading by a spherical rigid body at certain velocity perpendicular to the panel plate itself and numerical simulation is carried out as appropriate. Simulation results are validated through comparison with analytical work. The entire scheme carried out in this work is a novel comprehensive approach for the structural design of non-penetrated impact on metallic composites. The results show that the use of composites, in particular the bi-metallic composite, is instrumental in tailoring the plate materials to achieve non-penetrating impact.

Computational Simulation for Static and Dynamic Load of Rectangular Plate in Elastic Region for Analysis of Impact Resilient Structure

Impact resilient structures are of great interest in many engineering applications varying from civil, land vehicle, aircraft and space structures, to mention a few examples. To design such structure, one has to resort fundamental principles and take into account progress in analytical and computational approaches as well as in material science and technology. With such perspective, the first objective of this work is to develop a computational algorithm to analyze flat plate as a generic structure subjected to impact loading for numerical simulation and parametric study without considering the surface impact effect. The analysis is carried out from first principles for static and dynamic analysis; the latter is based on dynamic response analysis in the elastic region. The second objective is to utilize the computational algorithm for direct numerical simulation, and as a parallel scheme, commercial off-the shelf numerical code is utilized for parametric study, optimization and synthesis. Through such analysis and numerical simulation, effort is devoted to arrive at optimum configuration in terms of loading, structural dimensions, and material properties, among others. The codes developed are validated for generic cases. Further simulations are carried out using commercial codes for some sample applications to explore impact resilient structural characteristics in the elastic region.