Numerical analysis of aeroelastic characteristics of airship envelope

Stratospheric airship has great advantages, such as long-endurance, large coverage area, low-cost and so on, these advantages make airship be an ideal stratospheric platform and become highly valued. Airship envelope is a large inflatable membrane structure. As a key component, the envelope features flexible and large displacement. There is strong coupling between envelope structure and the ambient air when airship operating in the high altitude sky. The coupling characteristics have great impact on the aerodynamic and structural performance of airship. Aiming at the aeroelastic characteristics of the envelope structure, a fluid-structure coupled computational method is presented basing on a finite element program. As an example, the envelope structure of airship is computed and the S-A turbulent model is used. The envelope drag coefficient under different attack angle is computed. The contrast between experimental results coming from reference paper and numerical results highlight the correctness of this method. With the developed computational approach, the NPL envelope is also analyzed. The changes of length to diameter ratio, max cross section location and Reynolds number are studied and the aeroelastic characteristics of flexible envelope are analyzed. These results can give some valuable information for precise forecast of the overall airship performance

Dynamics testing and simulation of inflatable deployable

The inflatable deployablemembrane antenna structures have many advantages such as small folding size, high reliability and low cost. The structure mainly consists of its center hub, thin-plate ribs, inflatable thermo-curing torus, reflected membrane and inflation control system. This paper establishes a deployable system to simulate zero-gravity based on the parabolic membrane antenna with inflatable torus and tests the deployable process. The shell-membranes finite element model of the antenna structuresis modeled to simulateof the dynamics charactersof the structure. After that the effectsof the different inflatable pressure inside its support torus, the temperature of thermos-curing on the dynamic characteristics are also discussed.Finally,the dynamic charactersof the inflatable antenna was tested on the condition of the horizontal suspension system with 12 elastic strings and the fully structural vibrational frequency were given, and the mode of vibration and damping ratio was verified to the correctness of the simulation method. These results provide the reference for the design of inflatable deployment antenna structures

Numerical simulations for gas-structure interaction in inflated deployment of folded membrane boom

AbstractIt is very important for gas-structure interaction between compressible ideal gas and elastic structure of space folded membrane booms during the inflatable deployment. In order to study this gas-structure interaction problem, Arbitrary Lagrangian-Eulerian (ALE) finite element method was employed. Gas-structure interaction equation was built based on equilibrium integration relationship, and solved by operator split method. In addition, numerical analysis of V-shape folded membrane booms inflated by gas was given, the variation of inner pressure as well as deployment velocities of inflatable boom at different stage were simulated. Moreover, these results are consistent with the experiment of the same boom, which shows that both ALE method and operator split method are feasible and reliable methods to study gas-structure interaction problem

Accuracy of EGN model in ultra-wideband optical fiber communication systems

The efficient and accurate evaluation of the transmission performance of high-capacity optical communication systems has always attracted significant research attentions. The enhanced Gaussian noise (EGN) model is considered as an excellent solution to predict the system performance taking into account linear and nonlinear transmission impairments. Since the conventional form of the EGN model is complicated and intractable for a fast computation, the closed-form simplification has been regarded as a direction to significantly reduce the computational complexity. However, the accuracy of such a closed-form EGN model becomes a main concern in the application of ultra-wideband optical communication systems. In this work, we have investigated the accuracy of the closed-form EGN model for ultra-wideband optical fiber communication systems, where the performance of the system using electronic dispersion compensation, multi-channel nonlinearity compensation and full-field nonlinearity compensation has been evaluated in terms of symbol rate, number of channels and signal power. Our work will provide an insight on the application of the EGN model in next-generation ultra-wideband long-haul optical fiber communication networks

Numerical analysis of aeroelastic characteristics of airship envelope

Stratospheric airship has great advantages, such as long-endurance, large coverage area, low-cost and so on, these advantages make airship be an ideal stratospheric platform and become highly valued. Airship envelope is a large inflatable membrane structure. As a key component, the envelope features flexible and large displacement. There is strong coupling between envelope structure and the ambient air when airship operating in the high altitude sky. The coupling characteristics have great impact on the aerodynamic and structural performance of airship. Aiming at the aeroelastic characteristics of the envelope structure, a fluid-structure coupled computational method is presented basing on a finite element program. As an example, the envelope structure of airship is computed and the S-A turbulent model is used. The envelope drag coefficient under different attack angle is computed. The contrast between experimental results coming from reference paper and numerical results highlight the correctness of this method. With the developed computational approach, the NPL envelope is also analyzed. The changes of length to diameter ratio, max cross section location and Reynolds number are studied and the aeroelastic characteristics of flexible envelope are analyzed. These results can give some valuable information for precise forecast of the overall airship performance

Effects of Crop Planting Structure Adjustment on Water Use Efficiency in the Irrigation Area of Hei River Basin

The adjustment of crop planting structure can change the process of water and material circulation, and thus affect the total amount of water and evapotranspiration in the irrigation district. To guide the allocation of water resources in the region, it is beneficial to ascertain the effects of changing the crop planting structure on water saving and farmland water productivity in the irrigation district. This paper takes Yingke Irrigation District as the background. According to the continuous observation data from 2012 to 2013, Based on the modified Soil and Water Assessment Tool (SWAT) model and taking advantage of monthly scale remote sensing EvapoTranspiration (ET) and crop growth parameters (leaf area index and shoot dry matter), we tested the simulation accuracy of the model, proposed irrigation efficiency calculation methods considering water drainage, and established the scenario analysis method for the spatial distribution of crop planting structure. Finally, we evaluated the changes in water savings in irrigation district projects and resources, the irrigation water productivity and the net income water productivity under different planting structure scenarios. The results indicate that the efficiency of irrigation has increased by 15~20%, while considering drainage, as compared with conventional irrigation efficiency. Additionally, the adjustment of crop planting structure can reduce regional evapotranspiration by 14.9%, reduce the regional irrigation volume by 30%, and increase the net income of each regional water area by 16%

Comparison of Two Folded Methods of Solar Sails

The solar sails can be deployed by jointed truss or by inflated support tube. The deployed process and final deployed state of the solar sails is closely related to the design of the deployed mechanism. Therefore, the design of the deployed mechanism is very important for this new type of spacecraft. In this paper, we study the problem of the inflatable deployment of the solar sail; we utilized MSC.Patran to build the Z-folded and the Z+ curly-folded finite element models. LS-DYNA was used to simulate the dynamic characteristics of the above two solar sails under different conditions, and the results were analyzed. The results show that in the model that adopted the Z-folded method, the deployed process is relatively stable, and the effect of deployment is good, which is more suitable for practical application

Numerical Simulation Analysis and Experimental Research on Damping Performance of a Novel Magnetic Fluid Damper

Considering the low-frequency and large-amplitude vibration characteristics of the high-rise structure, a tuned magnetic fluid rolling-ball damper is proposed to suppress the vibration of the structure. By adjusting the external magnetic field to control the natural rolling frequency of the ball, the purpose of tuning vibration reduction is achieved. Firstly, the working principle of the damper is theoretically analysed, a three-dimensional (3D) magnetic-fluid-solid multiphysical field coupling mathematical model of the damper is established and the governing equations of multiphysical field coupling are derived. Secondly, the magnetic field distribution and operating characteristics of the damper are simulated and analysed. Finally, the effectiveness of the model is verified by experiments, and the damping performance of the damper with two kinds of magnetic fluid is tested and compared. The results show that the magnetic-fluid-solid multiphysical field coupling model can accurately simulate the working characteristics of the damper. The maximum damping force of the damper is about 12% of the elastic force of the structure, which can increase the damping ratio of the structure by about two times, effectively reduce the vibration response time, and suppress the vibration of the high-rise structure

Dynamics testing and simulation of inflatable deployable

The inflatable deployablemembrane antenna structures have many advantages such as small folding size, high reliability and low cost. The structure mainly consists of its center hub, thin-plate ribs, inflatable thermo-curing torus, reflected membrane and inflation control system. This paper establishes a deployable system to simulate zero-gravity based on the parabolic membrane antenna with inflatable torus and tests the deployable process. The shell-membranes finite element model of the antenna structuresis modeled to simulateof the dynamics charactersof the structure. After that the effectsof the different inflatable pressure inside its support torus, the temperature of thermos-curing on the dynamic characteristics are also discussed.Finally,the dynamic charactersof the inflatable antenna was tested on the condition of the horizontal suspension system with 12 elastic strings and the fully structural vibrational frequency were given, and the mode of vibration and damping ratio was verified to the correctness of the simulation method. These results provide the reference for the design of inflatable deployment antenna structures

Study and Prediction of Surface Deformation Characteristics of Different Vegetation Types in the Permafrost Zone of Linzhi, Tibet

Permafrost and alpine vegetation are widely distributed in Tibet, which is a sensitive area for global climate change. In this study, we inverted the surface deformation from 22 May 2018 to 9 October 2021 in a rectangular area within the city of Linzhi, Tibet, using the Sentinel1-A data and two time-series interferometric system aperture radar (InSAR) techniques. Then, the significant features of surface deformation were analyzed separately according to different vegetation types. Finally, multiple machine learning methods were used to predict future surface deformation, and the results were compared to obtain the model with the highest prediction accuracy. This study aims to provide a scientific reference and decision basis for global ecological security and sustainable development. The results showed that the surface deformation rate in the study area was basically between ±10 mm/a, and the cumulative surface deformation was basically between ±35 mm. The surface deformation of grassland, meadow, coniferous forest, and alpine vegetation were all significantly correlated with NDVI, and the effect of alpine vegetation, coniferous forest, and grassland on permafrost was stronger than that of the meadow. The prediction accuracy of the Holt–Winters model was higher than that of Holt′s model and the ARIMA model; it was expected that the ground surface would keep rising in the next two months, and the ground surface deformation of alpine vegetation and the coniferous forest was relatively small. The above studies indicated that the surface deformation in the Tibetan permafrost region was relatively stable under the conditions of alpine vegetation and coniferous forest. Future-related ecological construction needs to pay more attention to permafrost areas under grassland and meadow conditions, which are prone to surface deformation and affect the stability of ecosystems