Aerodynamic design and static stability of a hybrid buoyant aircraft /
Hybrid buoyant (HB) aircraft in which 50% of gross takeoff mass is supported by “free of cost aerostatic lift”, are a new arena to boost up the tourism and agricultural industry by leveraging on the new merger of lighter than air and heavier than air technologies. Due to non-availability of historic...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
Kuala Lumpur :
Kulliyyah of Engineering, International Islamic University Malaysia,
2017
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| Subjects: | |
| Online Access: | Click here to view 1st 24 pages of the thesis. Members can view fulltext at the specified PCs in the library. |
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| Summary: | Hybrid buoyant (HB) aircraft in which 50% of gross takeoff mass is supported by “free of cost aerostatic lift”, are a new arena to boost up the tourism and agricultural industry by leveraging on the new merger of lighter than air and heavier than air technologies. Due to non-availability of historical trends for HB aircraft, which are required to begin with traditional method for aircraft design, it is quite difficult to estimate its aerodynamic and stability characteristics. In the present research work, correlation of the geometric and buoyant properties of the swimming animals with the HB flying vehicles has been done to link the existing modern knowledge of aerospace with the biological sciences. Fineness ratio, location of maximum width and buoyant independent drag of a California sea lion are found to be the three quantities which are common with hybrid buoyant aircraft. Based on the existing fundamental relationships used for aircraft as well as airship design, a new conceptual design methodology for such aircraft is proposed with the help of two design examples. Pugh concept selection charts have assisted to rank the population of different concepts of such aircraft. Driving factors of such design concepts have been reviewed along with the selection of figure of merits. The diffused lift technology in HB aircraft seems to have eradicated the separate requirement of the heating mechanism for the lifting gas. A methodology for system design for consistent aerostatic lift is also proposed. The focus of this research work is not on the degree of “exactness” of the potential designs being considered at conceptual level, but rather to get the first- hand knowledge of the aerodynamics and static stability characteristics. Existing analytical relationships for the skin friction drag and Munk-Multhopp's relationships for the estimation of pitching moment are revisited and potential issues related to their derivation are also elaborated. For the conceptual design work, Aircraft Digital DATCOM is used for a hybrid lift aerial vehicle. XFLR software along with the CFD results of the fuselage are used for HB aircraft, designed for STOL application. New analytical relationship for the estimation of the neutral point of a HB aircraft is derived. A first order approximation of the power-off stick fixed neutral point is done by using the computational results of the fuselage along with the panel method results for the lifting surfaces. The value so obtained is then compared with that obtained from the steady state simulations of the clean configuration of a two seater HB aircraft for which the SIMPLE scheme is employed for pressure velocity coupling along with the k-ω SST model. CFD results under predicts the slope of pitching moment as well as the static margin. Irrespective of the difference of flight and wind tunnel's Reynolds number, a good comparison of results is obtained. However, from the controllability point of view, it's negative sign can be made positive by designing an elevator for constant pitch down position for the level flight, moving the wing to further aft position or by increasing the anhedral angle of the canard. A chaotic behavior in the overall lift, drag and yawing moment is observed due to the dorsal fins. An increase in the aerodynamic coefficients is also observed when the configuration is tested after removing the dorsal fins. Moreover, an increase in the lateral stability is also observed when the canard is given a small anhedral angle. The developed databank of aerodynamic and static stability derivatives will be highly beneficial for the future design work of such aircraft after applying the Reynolds number corrections. |
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| Physical Description: | xxi, 220 leaves : illustrations ; 30cm. |
| Bibliography: | Includes bibliographical references (leaves 171-182). |