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The aerodynamic characteristics of turboprop aircraft are greatly affected by the running propellers. In this paper, propeller slipstream effects on the static lateral-directional stability characteristics of a typical twin-engine turboprop aircraft with clockwise rotating propellers were investigated through unsteady computational fluid dynamics (CFD) simulations and wind tunnel experiments. The propeller slipstream led to a significant decrease in the lateral static stability contribution of the wing-body-nacelle (WBN), and the most affected wing sections were located near the left boundary of the port propeller slipstream region. Moreover, the influence of the propeller slipstream on the lateral static stability contribution of the vertical tail plane (VTP) significantly altered the rolling moment curve slope of the entire airframe. Due to the effects of the propeller slipstream on the local dynamic pressure and therefore the effectiveness of the VTP, the aircraft showed significantly different directional static stability behaviors between the positive and negative sideslip conditions. Furthermore, it was found that the configurations with clockwise rotating propellers readily experience dramatic losses in directional static stability at large negative sideslip angles.

In this study, we differentiate wet processes from dry processes in shaping the extratropical thermal stratification during the Last Glacial Maximum. Our findings indicate that even during the dry glacial period the influence of wet processes on thermal stratification cannot be overlooked. The applicability of dry and wet baroclinic adjustment theory strongly depends on the seasonality rather than the glaciation as the warm season is characterized by a weaker meridional temperature gradient and increased precipitation than the cold season. Despite that the baroclinic adjustment theory based on effective static stability can be proficiently applied to all seasons, the classical dry baroclinic adjustment theory may be better suited for use during relatively cold seasons. These findings have important implications for understanding processes governing the extratropical thermal stratification, particularly in the context of cold climate. Plain Language Summary In this study, we examined how different processes affect the formation of the extratropical thermal stratification during the Last Glacial Maximum. We found that both dry and wet processes play a crucial role, with the wet processes being particularly important during warm seasons. Our results suggest that the importance of wet process is largely dependent on the seasonality instead of glaciation. These findings help to improve our understanding of the extratropical thermal stratification and its governing processes, particularly in the context of cold climates. Key Points The study differentiates wet process from dry process in shaping extratropical thermal stratification during the Last Glacial Maximum Even during the dry glacial period, wet processes still poses a significant influence on thermal stratification Seasonality governs dry and wet baroclinic adjustment theory applicability, with the dry theory being more suited for cold seasons

This article is the first attempt to employ deep learning to estimate the mechanical performance of multi-phase systems. Features of the design-points are obtained with the aid of the fast-converging numerical method used to solve the governing motion equations developed according to the kinematics of shear deformable structures. The optimum values of the parameters involved in the mechanism of the fully-connected neural network are determined through the momentum-based optimizer. The strength of the method applied in this survey comes from the high accuracy besides lower epochs needed to train the multi-layered network. It should be mentioned that the mechanical characteristics of the structure are computed through a two-step micromechanical scheme including the Halpin–Tsai method. The accuracy of the employed approach is examined and verified through the comparison of the results with those published in the literature. The numerical results give the practical hint that increasing the content of the reinforcement phase not always equal to increasing the resistance of the composite structure toward static instability. Thus, designers must choose the weight content of nano or macro-scale reinforcements by considering the shape factors of these materials to boost the strength of the system appropriately.

Precipitation was claimed to increase over Asian–African summer monsoon (AAM) regions during past interglacial epochs and also under future global warming scenario. Using CMIP6 model experiments, this study compares the simulated changes of AAM in Last Interglacial (LIG) and Mid-Holocene (MH) to that global warming scenario. Moisture budget analysis shows that the increased monsoon rainfall during interglacial epochs primarily results from the dynamic process associated with strengthened monsoon circulation but is caused by thermodynamic process under global warming scenario associated with increased mean moisture. To disentangle the mechanisms for the distinct changes in vertical and horizontal monsoon circulation, we further decompose the response of AAM to global warming into the direct effect from CO 2 radiative forcing and the indirect effect due to increased sea surface temperature (SST), based on idealized experiments. The results show that the effect of direct CO 2 radiative forcing on the AAM is similar with that in interglacial epochs driven by enhanced land–ocean equivalent potential temperature contrast, both of which are characterized by strengthened vertical and horizontal monsoon circulation despite regional difference. However, the above effect is overwhelmed by the substantially increased SST under global warming, which is absent in interglacial epochs. The substantial SST warming acts to weaken the monsoon circulation by decreasing the land–ocean equivalent potential temperature contrast and enhancing atmospheric static stability. Therefore, the lack of global SST warming in interglacial epoch is the primary cause for the distinct change of AAM circulation from global warming scenario.

Research on helicopter stability is essential for the design of flotation systems and serves as a primary basis for evaluating wind and wave resistance. The drainage volume method and fluid–solid coupling method are commonly used for calculating floating characteristics. However, the drainage volume method ignores the flexibility of airbags and their interaction with the helicopter, while the fluid–solid coupling method is computationally intensive. In contrast, the analysis of a helicopter’s hydrostatic floating characteristics is a static problem. It suffices to obtain relevant results when the helicopter reaches a stationary state, without the need to accurately simulate the dynamic process of achieving that state. Therefore, this paper proposes an equivalent calculation method, in which the hydrostatic effect of water on the helicopter is represented by the hydrostatic pressure applied across the entire flotation system. The finite element method (FEM) is then employed to determine the final static state, and the results are compared with those from the drainage volume method and available experimental data to validate the reliability of the proposed approach. To elucidate the influence mechanism of airbags and flexible connecting straps on the lateral static stability of helicopters, this paper analyzes airbag positions at various heeling angles and examines the impact of different internal airbag pressures. The results indicate that the main factor affecting lateral static stability is the displacement of the airbags. This displacement causes variations in the airbag’s buoyancy and center of buoyancy, thereby reducing the lateral heeling moment.

Dynamic or static stability of electrical networks is maintained not only by the internal energy of the system but also by the utilization of a hot power reserve. In networks that incorporate renewable energy sources, this reserve should be commensurate with the power capacity of the renewable energy sources. However, this leads to an increase in economic costs. Additionally, the integration of renewable energy sources results in a decrease in the dynamic stability of the system due to the unregulated changes in the supplied energy. The objective of this research is to analyze the potential impact of renewable energy sources on network stability and explore possibilities for enhancing stability through adaptive operation of smart consumers. Renewable energy generation is characterized by temporal and concentration uncertainties, which can potentially disrupt the operation of the energy system. The primary approach employed in this study involves analyzing the potential influence of various operational modes of smart consumers, both during load commutation and energy source switching. The main outcome of this work is the development of a smart consumer algorithm. The devised operating principle mitigates the effects of unstable renewable energy operation or uncertain consumer behavior.

The western North Pacific subtropical anticyclone (WNPAC) usually fully develops during El Niño mature winter, and it is a key system connecting East Asian climate to ENSO. Based on a comparison between the RCP8.5 and the historical experiment of 30 coupled models from the CMIP5, we find that the response of the intensity in the anomalous WNPAC during El Niño mature winter remains almost unchanged under global warming. Taken the anomalous WNPAC as a two-step response to the diabatic heating anomaly over the equatorial central-eastern Pacific, numerical experiments based on GFDL_dry model and diagnoses are performed to explore the underlying mechanisms. The results demonstrate that the competition between the enhanced diabatic heating anomaly over the equatorial central-eastern Pacific and the enhanced mean state static stability results in a weakly enhanced low-level northeasterly wind anomaly over the WNP. Under an enhanced negative meridional gradient of the mean state low-level specific humidity, the negative moist enthalpy advection anomaly is enhanced over the WNP, which favors the enhanced negative precipitation anomaly. The negative precipitation anomaly over the WNP is thus enhanced due to atmospheric internal processes rather than the changed local SST anomaly. Finally, the competition between the enhanced local diabatic heating anomaly over the WNP and the enhanced mean state static stability results in an almost unchanged anomalous WNPAC.

Three static stability indices (K-index, KI; Lifted-index, LI; and Total Totals index, TTI) and three related thermodynamic parameters (First and second Adedokun indices; ADED1 and ADED2 as well as the available potential energy; CAPE) were estimated to predict instability condition and precipitation over Nigeria. ERA5 reanalysis datasets of daily air temperature and specific humidity at multiple pressure levels from 1979 to 2018 were used for the prediction while the computed seasonal averages of the static stability indices (SSIs) and thermodynamic parameters (TPs) were validated with the precipitation data. It was revealed that SSIs and TPs produced ranges of values that were fairly good predictive of atmospheric convection and instability conditions over different climatic zones. They adequately captured seasonal variations in atmospheric instability conditions and migration and pulsation of the south-westerly and the north-easterly wind systems. Significant decreasing trends in annual SSIs, PTs, and precipitation were obtained over Sahel. Furthermore, fairly strong and significant positive correlations (0.66 ≤ r ≤ 0.87) were obtained between precipitation and SSIs in the north i.e. Sahel and Savannah. Fluctuation in precipitation was explained by 26–70% variations in LI, 13–19% in ADED1, and 27–36% variations in KI, particularly in the north. In conclusion, diminishing trends of the LI, KI, and ADED1 during the 40-year study period were adduced to reduced precipitation. The study has application in improved weather forecast of convection systems and precipitation in West Africa at large.

The recent improvement of technology readiness level in aeronautics and the renewed demand for faster transportation are driving the rebirth of supersonic flight for commercial aviation. However, the design of a future supersonic aircraft is still very challenging due to the complexity of several problems, such as static stability performance during the acceleration phase from subsonic speeds to supersonic speeds. Additionally, the interest of scientific community in open source numerical platform as a valid tool for a reliable and affordable aerodynamic design is considerably growing. In this framework, the present work addresses the aerodynamic performance of a Concorde-like aeroshape developed within the preliminary design of a high-speed civil transportation aircraft. Several flight conditions, ranging from subsonic to supersonic speeds, were investigated in detail by using Computational Fluid Dynamics. The aerodynamic force and moment coefficients are computed with fully three-dimensional and steady state Reynolds Average Navier-Stokes simulations, carried out in turbulent flow conditions. The effect of the Mach number variation on the shift of the aircraft aerodynamic center is detailed, by focusing on the aircraft pitching static stability. Flowfield numerical simulations are performed with both commercial (Ansys-Fluent) tool and open-source (SU2) code, which is also used extensively in multidisciplinary design procedures, for further comparisons. Particular attention is focused on the shift of the aeroshape aerodynamic center to verify that the provided wing design allows the aircraft static margin to be within 5% of the reference length, both at low-speed and high-speed flight conditions. The computed positions of the aerodynamic center are in agreement with the aeroshape surface pressure distributions and confirmed the literature results available for the Concorde aircraft. Therefore, in the view of future simulation campaigns for supersonic transportation aircraft, the present work aims to bridge the gap between previous aerodynamic design experiences, for instance matured on Concorde, and those carried out with modern CFD tools on full-scale aircraft, and on time-scales compatible with conceptual design practice. Finally, as the difference between the computed aerodynamic coefficients reflected mainly on drag computation performed with SU2, a special focus on numerical diffusion effect of the solver is also given and compared with a commercial certified CFD tool. This adds a unique further contribution to the SU2 community for aeronautics application.

The aim of this paper is to investigate the nonlinear static stability of nanocomposite multilayer organic solar cells (NMOSC) on elastic foundations under axial compressive loading in thermal environment. In the previous literatures, the NMOSC consists of five isotropic layers including Al, P3HT:PCBM, PEDOT:PSS, ITO and glass. However, the disadvantages of ITO are high cost, scarcity and low chemical stability. Therefore, the graphene material is chosen to replace the ITO layer in this study. The material properties of graphene layer are assumed to depend on temperature while the elastic moduli of four remaining isotropic layers are constants. For methodology, the geometrical compatibility and nonlinear equilibrium equations are derived based on the Hamilton’s principle and classical plate theory. These equations are solved by using the Galerkin method in order to obtain the expression of critical buckling load and compressive loading – deflection amplitude curves. For geometric optimization problem, three optimization algorithms including social group optimization, basic differential evolution and enhanced colliding bodies optimization algorithms are applied to find the maximum value of the critical buckling loading of NMOSC depending on four geometrical and material variables. Parametric studies are conducted to indicate the influences of temperature increment, geometrical parameters, initial imperfection and elastic foundations on the static stability characteristics of the NMOSC.