Abstract
In this research, an experimental investigation was carried out at the International Islamic University Malaysia - Low Speed Wind Tunnel facility on a generic model of a hybrid lifting hull. Based on the historical trends of non-rigid airships, the fineness ratio of the said hull has been selected equal to 4. Free stream velocity was kept at 20 m*s and, along with the estimation of aerodynamic parameters, longitudinal and lateral stability characteristics were determined over a range of angles of attack from −8° to +12° and angles of sideslip from −10° to +10°. Zero lift coefficient was obtained at −4.2°, and the corresponding value was found to be greater than that at zero angle of attack. The comparison of the experimental results with the existing analytical relationships of wing has revealed that such an airfoil shaped hull cannot be considered as a wing due to 37% less analytical value of lift coefficient than that obtained by CFD simulations of the said hull. Existing equation of form factor of hull for conventional airships was also revisited, and a correction factor equal to 1.16 in the fundamental drag equation of aircraft’s fuselage was also proposed for fineness ratio equal to 4. Trends of the experimental data and comparison of the same with the theoretical calculations and computational results posed some interesting findings. The longitudinal and directional stabilities of a hybrid lifting hull were found to be statically unstable.
Highlights
The concept of lifting fuselage for aircraft and hybrid lifting hull for hybrid airship is derived from nature as a few marine animals do generate aerodynamic lift from the body (Ul Haque et al 2016a). Vogel (1994) was among the first who noticed that, if one looks at a housefly or fruit fly from the side, the head, thorax and abdomen seem to form a non-symmetrical airfoil-flatter on the bottom, more rounded on top
In order to find the aerodynamic and static stability behavior of a hybrid lifting hull (HLH) model, tests were conducted at the International Islamic University Malaysia - Low Speed Wind Tunnel (IIUM-LSWT) at Reynolds number (Re) equal to 6.3 × 105 against free stream velocity equal to 20 m∙s–1
In order to get the 1st-order approximation of aerodynamics and static stability derivatives of the HLH, the steady-state simulations were run by using ANSYS® Fluent software for which the SIMPLE scheme is employed for pressure velocity coupling along with the k-ω SST model
Summary
The concept of lifting fuselage for aircraft and hybrid lifting hull for hybrid airship is derived from nature as a few marine animals do generate aerodynamic lift from the body (Ul Haque et al 2016a). Vogel (1994) was among the first who noticed that, if one looks at a housefly or fruit fly from the side, the head, thorax and abdomen seem to form a non-symmetrical airfoil-flatter on the bottom, more rounded on top. The concept of lifting fuselage for aircraft and hybrid lifting hull for hybrid airship is derived from nature as a few marine animals do generate aerodynamic lift from the body (Ul Haque et al 2016a). There are some cases in which there is a requirement of negative lift (Vogel 2013). Ducks have enough air in their plumage so they are awkwardly buoyant and may need negative lift (Prange and Schmidt-Nielsen 1970). Ul Haque et al (2015a) argued that the lift generated by the body is perhaps free of cost lift and can be utilized if such a marine animal want to swim at constant level/height in the sea. Additional lift is required for those flight segments like coming out from water, sharp turns etc
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