An effective unsteady aerodynamic-optimization method of airfoil for cycloidal propellers is developed. Firstly, the class-function/shape-function transformation parameterization method is adopted to describe the airfoil profile with different geometrical parameters. Secondly, the sample points in the design space are selected using the optimal Latin hypercube design methodology. Thirdly, the actual aerodynamic performance of cycloidal propellers is simulated by using the time-dependent incompressible Reynolds-averaged Navier–Stokes computational fluid dynamics method and the sliding-mesh technique, which are verified by validation cases on an oscillating NACA 0012 airfoil and the baseline cycloidal propeller. Then, to replace the time-consuming computational fluid dynamics solver, kriging surrogate models are established using the sample data. Finally, the genetic algorithm is adopted to determine the optimized airfoil in the design space based on the constructed kriging models. Optimization is conducted on a micro- four-bladed cycloidal propeller with the NACA 0015 airfoil, and the results show that the figure of merit of the cycloidal propeller is increased by 18.31% at the design rotation speed. Although the optimization is conducted only at the design rotation speed, an appreciable improvement of the figure of merit can be achieved for a wide range of rotation speeds.

An improved variational optimization approach is established to optimize and analyse the propulsion efficiency of the high-altitude contra-rotating propellers for high-altitude airships based on the Vortex Lattice Lifting Line Method. The optimum radial circulation distribution, chord and pitch distribution are optimized under the maximum lift-to-drag ratio of aerofoils. To consider the effects of the actual Reynolds number and the Mach number of each aerofoil section, aerodynamics such as lift coefficient, drag coefficient and lift-to-ratio are obtained by interpolating a CFD database, which is established by numerical simulations under different Reynolds number, Mach number and angles-of-attack. The improved method is verified by validation cases on a high-altitude CRP using the three-dimensional steady Reynolds-averaged Navier-Stokes solver and moving reference frames technique. The optimization results of thrust, torque and efficiency for both the individual front/rear propeller and CRP are shown to agree reasonably well with the CFD results. Using the improved approach, the influence of blade numbers, diameter, rotation speeds, axial distance and torque ratio on the optimum efficiency of CRPs is illustrated in detail by conducting parametric studies.

In this technical note, we investigate the agent-based finite-time leader-following consensus for Earth-observation systems with multiple stratosphere airships, in which the high-order nonlinear dynamic and external disturbances are considered for multi-agent systems. Based on the distributed observer, which is used to acquire the state of the leader airship for the following airships, the dynamic cascade control is designed to realize the finite-time leader-following consensus for Earth-observation systems. It is mathematically proven that the convergence is finite for the stratosphere airship earth-observation system. Simulation results are given to illustrate the effectiveness of the proposed scheme.

Based on the biaxial experiment data of the membrane material under hot and cold conditions, the mechanical properties calculation model of envelope material was established with consideration of the effects of varying stress ratios, stress magnitudes and temperatures on the mechanical properties of near-space airship material. Using the heat source model, Computational Fluid Dynamics (CFD) simulation, User-Defined Function (UDF), structural finite element analysis software and the user subroutine of an airship to define the behaviour of fabric material, the fluid–structure–thermal coupling model of airship envelopes was established. In addition, a near-space airship was selected as the research subject to calculate the diurnal temperature differences during the summer solstice and analyse the diurnal temperature distribution of the envelope. Under controlled environmental conditions, the deformation law of the near-space airship under the influence of fluid–structure–thermal coupling was calculated and summarised. The present fluid–solid–thermal coupling model takes into account the anisotropy of materials, temperature, stress magnitude, stress ratio and other influencing factors, which can more accurately reflect and predict the stress–strain distribution and the deformation law of near-space airships.

This paper describes a shape exploration and multidisciplinary optimization method of unconventional semirigid nearing space airships. The approach includes several improved mutually interacting di...

Stratospheric airships have much potential in military and commercial applications. Design, analysis and optimization of stratospheric airships involves complex trade-off of different disciplines, and hence a multidisciplinary approach is essential. This paper describes a methodology coupling several disciplines and involving seven design variables to obtain the optimal design of a stratospheric airship powered by solar arrays. A numerical method is established to calculate the output power of the solar array in the optimization process. The optimal solutions are obtained using hybrid algorithms. The methodology can obtain the optimal envelope shape, solar array layout and other general configurations of subsystems. Results show that the methodology was able to achieve a solution with a 19.2% reduction in airship volume compared to the value being part of an arbitrary initial set of airship parameters. In addition, a comparative study is carried out to highlight the importance of considerations of solar array layouts and array circumferential location. Furthermore, detailed sensitivity analysis shows that operating parameters of latitudes, heading angles and average resisting wind speeds have significant effects on the airship design and solar array layouts.