Numerical aerodynamic investigations on stratospheric airships of different tail configurations
Numerical investigations on stratospheric airships of different tail configurations are conducted based on the Reynolds-averaged N-S equations and k-ω SST turbulent model in the condition of the same volume and total area of the tails. The influence of tail configurations on the force and moment characteristics as well as flow phenomena on both hull and fins are analyzed. In particular, the hull-fin mutual interference effect is discussed compared to the bare hull performance. It is found that a cross-shaped tail produces a superior lift characteristic and stability at high angle but greater drag due to horizontal fins, both in pitch and yaw channels than the inverted Y and X shaped tail. The hull-fin interference generates additional hull lift, drag and an offsetting moment and causes side edge separation on the suction side of horizontal (side) fins in the cross (inverted Y and X shaped) tail configuration. The inverted Y-shaped tail provides the greatest interference drag. These investigations serve to provide references for airship configuration design.
Aerodynamic estimation techniques for aerostats and airships
A semi-empirical steady-state model of a finned axisymmetric body is developed and used to compute hull -fin mutual interference factors and cross flow drag coefficients from wind tunnel data on five aerostats and airships. The results are in general agreement with expectations from theory and provide a b asis for predicting aerodynamic coefficients. The model is extended to unsteady motion by considering the local flow on finite hull segments and the fins. This dynamic model is applicable to non-linear simulations and the computation of rotational stability derivatives for which equations are derived. For one zerostat, rotational stability derivatives calculated from static wind tunnel data are compared with experimental results from a whirl ing-arm tow tank.
Subsonic aircraft: Evolution and the matching of size to performance
Methods for estimating the approximate size, weight, and power of aircraft intended to meet specified performance requirements are presented for both jet-powered and propeller-driven aircraft. The methods are simple and require only the use of a pocket computer for rapid application to specific sizing problems. Application of the methods is illustrated by means of sizing studies of a series of jet-powered and propeller-driven aircraft with varying design constraints. Some aspects of the technical evolution of the airplane from 1918 to the present are also briefly discussed.