J.S. Mohamed Ali

Conceptual design of a winged hybrid airship

The present study focuses on the sizing and aerodynamic contour design of a two-seater 1000 kg gross take-off mass winged hybrid airship. Unlike the conventional hybrid airships, which stay aloft and takeoff with the help of VTOL propulsion systems, a winged hybrid airship requires a certain speed to takeoff by utilizing lift coming from its aerodynamic surfaces. Heaviness fraction and takeoff ground roll are considered as measure of merit in initial sizing. Based on the design requirement of Malaysian inter-island tourism and transportation of agricultural products, range is set to 450 km and ground roll for take-off about 150 m. For the airship to be heavy enough for ground handling, the ratio of hydrostatic to hydrodynamic lift is set equal to 49:51. Summary of the results to be obtained in early design phase will give a baseline start to study the aerodynamics and stability characteristics of such airships in future.

Mirrorless Car: A Feasibility Study

Mirrorless cars are the conceptual cars in which the mirrors which are used as a visual aid for safe driving are replaced with camera and LCD screens thus making it totally mirrorless. These cars without mirror projections will result in clean external aerodynamics thereby reducing considerable amount of drag and hence offers a high potential to achieve higher fuel economy in driving a car. The present study is a trial to test whether such a mirrorless car can create a better driving condition for the driver in terms of ergonomics, safety and comfortability. Thus the latest modern technology is fused in a Malaysian car model making it mirrorless with the cameras replacing mirrors and the dashboard was modified to install the LCD screens on it. The modified car was tested for its characteristics on safety, comfortability and ergonomics. The driver’s behaviour while driving the mirrorless car was studied extensively and numerous interesting conclusions were derived.

Cambered profile of a California sea lion's body

More than 100 research articles have referred to an experimental study by [Feldkamp (1987][1]) on the California sea lion, which mentions that its body resembles a symmetric airfoil, NACA 66018. We believe that perhaps an oversimplification has been made in this comparison. This conclusion may be

Wind tunnel testing of hybrid buoyant aerial vehicle

Purpose Realistic data bank of aerodynamic and stability derivatives is still missing for hybrid buoyant aerial vehicles. Such vehicles take-off and land similar to an aircraft with their partial weight balanced by the aerostatic lift. The purpose of this paper is to use wind tunnel testing for a better understanding of the aerodynamic and static stability behavior of such vehicles. Design/methodology/approach The effect of wing on the aerodynamic and static stability characteristics of a clean configuration hybrid buoyant is analyzed. The free stream velocity is 20 m/s, and ranges of angle of attack and side slip angle are from −8° to 12° and ±16°, respectively. Data are corrected to account for the effect of strut interference and zero load condition. The maximum blockage of the model with respect to the cross-section area of the test section is about 2.7 per cent. Findings A hybrid model manufactured by using wood and metal is an optimum solution with less number of parts. The vehicle is statically, longitudinally and directionally stable. Wings designed to fulfill the partial requirement of lift contribute significantly to counter the huge moment generated by the voluminous hull for centre of gravity location ahead of the leading edge of the wing. Research limitations/implications There are number of manufacturing constraints for scaling down a model of a hybrid buoyant aerial vehicle configuration. Specially, the thickness of the wing limits the testing envelop of angle of attack and free stream velocity. Practical implications The data presented here are a preliminary guide for further work on larger size models. The data may also be used to build and perform flight tests on small full-scale instrumented models and to obtain flight dynamics data. Originality/value The estimated aerodynamic and stability derivatives and slopes can be utilized in future for multidisciplinary design.

Comparison of Digital DATCOM and Wind Tunnel Data of a Winged Hybrid Airship’s Generic Model

Use of low fidelity tools in designing subscale generic wind tunnel models is usually required to get first-hand knowledge about general trends of aerodynamic and stability parameters. Most of such tools are limited to well-defined conventional aircraft configurations. In the present work, aerodynamic and stability characteristics of a winged hybrid airship is explored at low subsonic speed by using Aircraft Digital DATCOM, which is based on semi-empirical methods for preliminary aircraft geometries. Spheroidal ellipsoidal shaped hull of the airship is modeled in DATCOM along with the geometrical details of wing and empennages. The prediction of zero lift drag coefficient, coefficient of lift and pitching moment is the focus of this paper. Except the drag coefficients, trends of analytical results compare well with experimental data.

Optimal location of piezoelectric patches For active vibration control

This paper focuses on finding the optimal location for a piezoelectric patch for minimizing the settling time of an excited isotropic and orthotropic plate. COMSOL Multiphysics has been used to design and model the plate with PID controller. Classical Optimization tool called Parametric Sweep has been used to achieve the objective of the experiment. Five different stacking sequences were used in the study of orthotropic plate. The results obtained by the FEA software indicated that by placing the piezoelectric patches at the optimal location, the settling time of a plate can decrease by 40% compared to placing it at the centre of the fixed end.

Effect of Temperature and moisture dependent material properties on the Bending behavior of Laminated Cylindrical Shell under Hygrothermal Loads

The effect of temperature and moisture dependent material properties on the bending behavior of simply supported angle-ply composite laminated shells has been investigated. A 13 term accurate higher order shear deformation theory with zigzag function is used in this analysis in which the effects of transverse shear deformation are taken into account. A number of examples are solved to illustrate the numerical results concerning bending response of simply supported angle-ply composite shell subjected to hygrothermal effects. It is suggested that temperature-dependent and/or moisture-dependent material properties ought to be used in the analysis of laminated composite shell subjected to hygrothermal loads.

Tensile Mechanical Property of Oil Palm Empty Fruit Bunch Fiber Reinforced Epoxy Composites

Natural, short, untreated and randomly oriented oil palm empty fruit bunch fiber reinforced epoxy composites were manufactured using vacuum bagging technique with 20% fiber volume composition. The performance of the composite was evaluated as an alternative to synthetic or conventional reinforced composites. Tensile properties such as tensile strength, modulus of elasticity and Poissons ratio were compared to the tensile properties of pure epoxy obtained via tensile tests as per ASTM D 638 specifications using Universal Testing Machine INSTRON 5582. The tensile properties of oil palm empty fruit bunch fiber reinforced epoxy composites were lower compared to plain epoxy structure with the decrement in performances of 38% for modulus of elasticity and 61% for tensile strength.

HYGROTHERMOELASTIC ANALYSIS OF ORTHOTROPIC CYLINDRICAL SHELLS

In this work, the combined effect of moisture and temperature on the bending behavior of simply supported orthotropic cylindrical shells has been investigated. Initially three dimensional equilibrium equations of thermoelasticity, simplified to the case of generalized plane strain deformations in the axial direction are solved analytically for an orthotropic cylindrical shell strip under thermal loading. Based on the realistic variation of displacements from the elasticity approach, a new higher order shear deformation theory was proposed for the analysis of an orthotropic cylindrical shell strip under hygrothermal and mechanical loading. The zigzag form of the displacement is incorporated via the Murakami zigzag function. Results are presented for mechanical and thermal loading for various layups and they are validated against the derived elasticity solution. The significance of retaining various higher-order terms in the present model, in evaluating the stresses and deflection for composite laminates is brought out clearly through parametric study. Useful results for combined hygrothermal loading are presented in tabular and graphical form. It is expected that the numerical results presented herein will serve as bench mark in future.