Erwin Sulaeman

Structural Wing Sizing for Multidisciplinary Design Optimization of a Strut-Braced Wing

A structural and aeroelastic model for wing sizing and weight calculation of a strut-braced wing is described. The wing weight is calculated using a newly developed analysis accounting for the special nature of strut-braced wings. A specially developed aeroelastic model enables one to consider wing flexibility and spanwise redistribution of the aerodynamic loads during in-flight maneuvers. The structural model uses a hexagonal wing-box featuring skin panels, stringers, and spar caps, whereas the aerodynamics part employs a linearized transonic vortex lattice method. Thus, the wing weight may be calculated from the rigid or flexible wing spanload. The calculations reveal the significant influence of the strut on the bending material weight of the wing. The strut enables one to design a wing featuring thin airfoils without weight penalty. It also influences the spanwise redistribution of the aerodynamic loads and the resulting deformations. Increased weight savings are possible by iterative resizing of the wing structure using the actual design loads. As an advantage over the cantilever wing, the twist moment caused by the strut force results in increased load alleviation, leading to further structural weight savings.

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.

EFFECT OF COMPRESSIVE FORCE ON STRUT-BRACED WING RESPONSE

Our investigations of a strut-braced wing aircraft, show that at high positive load factors, a large tensile force in the strut leads to a considerable compressive axial force in the inner wing, resulting in a reduced bending stiffness and even buckling of the wing. Studying the influence of this compressive force on the structural response of the strut-braced wing is thus of paramount importance. To perform such a study in a Multidisciplinary Design Optimization (MDO) environment requires an approach that is both accurate and computationally efficient. To that end, we have developed a nonprismatic beam finite element that takes into account the effect of compressive forces on the aeroelastic response of the inner wing. Both the elastic and the geometric stiffness matrices along with the mass matrix are derived. The buckling load of the wing can be obtained using either an eigenvalue analysis or specifying a constraint on the wing deflection. The influence of the compressive force on the aerodynamic load distribution due to the wing flexibility is also studied, as is the sensitivity of the wing response to the strut position. As expected, the effect of compressive forces on the response can be reduced by placing the strut closer to the wing tip. The proposed procedure is validated by comparing results with those given by NASTRAN.

PASSIVE LOAD ALLEVIATION IN THE DESIGN OF A STRUT-BRACED WING TRANSONIC TRANSPORT AIRCRAFT

This paper describes the multidisciplinary design optimization (MDO) of a transonic strutbraced wing aircraft. The optimization considers aeroelastic deformations of the wing and passive load alleviation. The calculations reveal that the strut twist moment provides substantial load alleviation and significant reductions in structural wing weight. To benefit from the potential of appl ying passive load alleviation during preliminary aircraft design, a flexible wing sizing module has been linked to the MDO design tool to optimize the design of three different strut-braced wing aircraft configurations featuring fuselage mounted engines, underwing mounted engines, and wingtip mounted engines.

EFFECT OF COMPRESSIVE FORCE ON FLUTTER SPEED OF A STRUT-BRACED WING

Previous investigations on a strut-braced wing analysis revealed that aeroelasticity plays an important role on the strut-braced wing design. The investigations showed that the location of the strut support on the wing affects the wing deformation, aerodynamic load redistribution and flutter speed. Another study on the buckling analysis of the strut-braced wing indicated also that the wing stiffness may have a significantly lower stiffness due to the compressive force due to the strut during a positive flight load maneuver. In the present work, a further investigation on the effect of compressive force on flutter and divergence speeds of the strut-braced wing is presented. To reduce the computational time, an efficient non-uniform beam finite element model is used for the wing structure, and a modified doublet lattice method is used for the unsteady aerodynamic calculations. Variation of several parameters, including strut location along the wing spanwise and chordwise directions, were investigated. To calculate the compressive force, a trim analysis was performed for each variation of these parameters. Comparison between the flutter boundary and flight envelope of the present strut braced wing design indicates that the influence of the compressive force on flutter speed is significant when the strut is placed near the wing tip.

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

Stability and Takeoff Ground Roll Issues of Hybrid Buoyant Aircraft

In the field of aviation it is well known that a vehicle’s stability and takeoff flight segment are critical. This issue becomes more critical for a hybrid aircraft which is concealed as an airship with huge volume of hull as compared with fuselage of a conventional aircraft. In the present work, stability issues of a generic model of airship and of a conceptual model of hybrid aircraft are discussed. Special emphasis is given for future sizing of empennages of IWHA-14, a hybrid aircraft concept proposed for Malaysian inter island transportation. Effect of gondola position on rotation angle for takeoff ground roll was analyzed and it was found that such configurations can meet the requirement of minimum roll angle.

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.

AEROSTATIC AND AERODYNAMIC MODULES OF A HYBRID BUOYANT AIRCRAFT: AN ANALYTICAL APPROACH

An analytical approach is essential for the estimation of the requirements of aerodynamic and aerostatic lift for a hybrid buoyant aircraft. Such aircrafts have two different modules to balance the weight of aircraft; aerostatic module and aerodynamic module. Both these modules are to be treated separately for estimation of the mass budget of propulsion systems and required power. In the present work, existing relationships of aircraft and airship are reviewed for its further application for these modules. Limitations of such relationships are also disussed and it is precieved that it will provide a strating point for better understanding of design anatomy of such aircraft.

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.