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Designing the high-performance, high-subsonic airfoils suitable for different Reynolds number flow is the major challenge for high-altitude long-endurance drones and ultra-high altitude solar aircraft. To overcome the difficulties, this paper proposed a set of aerodynamic optimization design methods that combine the improved category shape function transformation method, parallel computational fluid dynamics, and an improved whale optimization algorithm. This approach achieves high modeling accuracy, computational efficiency, and strong optimization ability. Verification using single-peak, multi-peak, and fixed-dimensional test functions demonstrates that the improved whale optimization algorithm has significantly enhanced optimization capabilities compared with the conventional whale optimization, particle swarm optimization, and gravity search algorithms. Numerical simulations are used to analyze the internal flow mechanisms before and after airfoil optimization under different Reynolds numbers. The results show that, compared with the original airfoil, the optimized airfoil has front loading characteristics that effectively reduce the adverse pressure gradient of the rear part of suction surface, promoting the transition in this region. The reduced adverse pressure gradient also inhibits the development and growth of laminar separation bubbles and slows down the growth of the boundary layer displacement thickness, thereby reducing wake mixing loss and improving the aerodynamic performance. [ABSTRACT FROM AUTHOR]

Distributed pulsating flow planar tube bundle heat exchanger (DPFPTB-HE) can improve heat transfer and have a high prospect of application in the industry. Computational fluid dynamics (CFD) software Fluent was utilized as an analysis tool, and the factors affecting heat transfer in heat exchangers were comprehensively studied based on the theory of fluid mechanics and heat transfer in this article. The local average surface Nusselt number(Nuv) evaluated the heat transfer performance. Results found that the DPFPTB-HE proposed in this paper has more uniform distribution of cold fluid in the shell domain and higher heat transfer efficiency in each layer of the tube bundle compared with the conventional planar tube bundle heat exchanger (PTB-HE). In this paper's single-factor analysis experimental session, the study showed that with the inlet velocity increases, Nuv increases; as the length of the branch pipe increases, Nuv decreases; branch pipe diameter increases, Nuv decreases. The results obtained Nuv by applying the optimal experimental parameters selected by the Taguchi method were 7.22% larger than the maximum value in the control group. The numerical result and methodology are beneficial for providing further insight into guiding the optimization of heat exchanger structure and promoting industrial progress. [ABSTRACT FROM AUTHOR]

Exploration of host–guest complexation between a shape-persistent H-bonded macrocycle and flexible guests may enable construction of new pseudorotaxanes systems. Here, we present the impact of varying the spacer length of four bis(4-phenylpyridinium) guests G1-G4 on production of pseudorotaxanes with a 2D H-bonded macrocycle 1a. The host–guest complexes are probed by 1H NMR, 2D NOESY and UV–vis spectroscopic techniques. [2]- and [3]- pseudorotaxane assemblies are formed specifically using these guests, demonstrating the dependency of accessing [2]- and [3]- pseudorotaxane on the spacer length of these dications. Theoretical calculations reveal the difference in the conformation of the guests between these two binding modes: the one with a 1:1 stoichiometry (spacer length: C4 and C6) show Z-shaped conformation and the other with a 2:1 stoichiometry (spacer length: C8 and C10) take a linear conformation. The findings of the threading modes may help develop new H-bonded macrocycle-based rotaxanes and other related mechanically interlocked molecules. [ABSTRACT FROM AUTHOR]