Power extraction performance of two semi-active flapping airfoils at biplane configuration

Jianyang Zhu,Jiacheng Zhang 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.1

The power extraction performance of two semi-active flapping airfoils at biplane configuration is analyzed in this work through numerical approach. Two NACA0015 airfoils, which are regarded as an energy extraction turbine, are arranged in a biplane configuration to perform forced counter pitching motion and are subsequently induced in a plunging motion. A numerical code based on finite volume method to solve the Navier–Stokes equations coupled with finite center difference method to solve the passive plunging motion governing equation is developed to simulate the interaction between the two semi-active flapping airfoils and fluid. Results show that the semi-active flapping airfoil cannot absorb more power from the fluid with biplane arrangement, but this arrangement is beneficial for the power extraction efficiency of the airfoil. Analysis of the fluid field of the airfoil reveals that the wing–wing interaction can promote the vortex evolution and reduce the vortex magnitude of the suction side of the biplane airfoils with appropriate initial distance (h s = 2.5d). As a result, the maximum plunging of the biplane airfoils is smaller than that of the single airfoil. The smaller maximum plunging displacement contributes to the increase in power extraction efficiency.

The aerodynamic performance of flexible wing in plunge

Jianyang Zhu,Chaoying Zhou 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.7

Inspired by the fact that flexible wing in nature possesses advance aerodynamic performance, a numerical experiment is applied to investigatethe aerodynamic performance of flexible wing in plunge motion, where the incompressible Navier-Stokes (N-S) equations coupledwith the structural dynamic equation for the motion of the wing is solved. A two-dimensional, elastic and inextensible beam modelwing is considered at Re = 1256. The harmonic plunge motion is specified at the leading edge of wing, and the other part of wing is respondedpassively deforming by the aerodynamic force. By analyzing the flow field, aerodynamic force and energy efficiency of differentflexibility wings, it is found that the flexibility influences the aerodynamic characteristics of the plunge wing greatly and when theplunge frequency is less than the structural frequency the flexibility can increase the thrust force and the energy efficiency of the wing,and the maximum energy efficiency is obtained when the wing plunge near the resonance. Moreover, a lighter wing possesses largerenergy efficiency than a heavier wing, but it may not be functioning for too light wing. The results obtained in this study will providephysical insight into the understanding of fluid and structure interaction problem.

Numerical study of a variable camber plunge airfoil under wind gust condition

Jianyang Zhu,Lin Jiang,Hui Zhao,Bo Tao,Bin Lei 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.11

Variable camber deformation is observed during the flight of some insects and bird species; however, the effect of this special airfoilshape motion on the aerodynamic characteristics of the airfoil is not well understood, especially for the airfoil under gust wind. We did anumerical study to investigate the aerodynamic characteristics of a variable camber plunge airfoil under wind gusts. A weak couplingprogram was developed to simulate the interaction between the variable camber plunge airfoil and fluid, and the flow field, aerodynamicforce and energy efficiency of different camber airfoils under different wind gust conditions are investigated. It was found that camberdeformation influences the aerodynamic characteristics of the airfoil greatly. If the airfoil has an appropriate camber deformation, thedeformation can increase the mean thrust and the propulsive efficiency of the airfoil. Moreover, the aerodynamic characteristics of theappropriate camber airfoils are not significantly affected by the gust frequency, and there exists a range of gust amplitude where the aerodynamiccharacteristics of the airfoils are also not significantly affected by the gust amplitude, which may be beneficial for aerodynamicstability of the airfoil. The results also show that appropriate camber deformation can suppress leading edge vortex separation, whichimproves the aerodynamic characteristics of the airfoil.

Aerodynamic Performance of the Three-Dimensional Lumped Flexibility Wing Under Wind Fluctuating Condition

Zhu Mingkang,Zhu Jianyang,Zhang Tao 한국항공우주학회 2021 International Journal of Aeronautical and Space Sc Vol.22 No.4

Understanding the effect of fluctuating wind on the aerodynamic performance of the wing is important for designing practical using flapping-wing micro air vehicles (FMAV). This paper aims at providing a systematic synthesis on the fluctuating wind influence on the performance of the three dimensional lumped flexibility wing based on the numerical analysis approach. The fluctuating wind is simplified as a sine type function, and the flexibility of the wing is modeled as the passive pitching motion by connecting a rigid wing to a torsional spring at the root of the wing. The interaction between the fluctuating wind and the lumped flexibility wing is performed on a high-resolution computational grid. The evaluation is based on validation with published experiment data. The results indicate that the fluctuating wind cannot enhance the flexible wings’ propulsive and lifting performance simultaneously, however, it influences the aerodynamic characteristics of the wing greatly. Comparing to the rigid wing, the suppress leading edge vortex and trailing edge vortex are observed of the flexible wing under appropriate fluctuating wind, which leads the flexible wing to not only have better propulsive and lifting performance, but also flight stability performance.

Experimental and theoretical research on mechanical behavior of innovative composite beams

Gang Zhu,Jianyang Xue,Yong Yang,Jianguo Nie 국제구조공학회 2013 Steel and Composite Structures, An International J Vol.14 No.4

The web-encased steel-concrete composite (WESCC) beam is a new developed steel-concrete composite beam. Experiments of six simply supported WESCC beam specimens were conducted. The effects of the shear-span ratio and steel section type were all investigated on the static behaviors such as failure modes, failure mechanism and bearing capacity. The experimental results denoted that all specimens failed in bending mode and the degree of combination between the bottom armor plate of steel shape and concrete were very well without any evident slippage, which demonstrated that the function of bottom armor plate and web were fully exerted in the WESCC beams. It could be concluded the WESCC beams have high stiffness, high load carrying capacity and advanced ductility. The design methods are proposed which mainly consist the bearing capacity calculation of bending and flexural rigidity. The calculation results of the bearing capacity and deflection which take the shear deflection into account are in agreement with the experimental results. The design methods are useful for design and application of the innovative composite beams.

Lightweight object detection network model suitable for indoor mobile robots

Lin Jiang,Wenkang Nie,Jianyang Zhu,Xumin Gao,Bin Lei 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.2

This work proposes a lightweight object detection network model ShuffleNetSSD (S-SSD) to solve the problem of single shot multibox detector (SSD) network model where it cannot meet the real-time performance requirement in the task of object detection and recognition of indoor mobile robot. This model is suitable for indoor mobile robot by improving the SSD network model based on ShuffleNet network. The main idea of the improvement is that SSSD replaces VGG-16 network as the basic feature extraction network of SSD network model with ShuffleNet network. The proposed model is based on the design of deep separable convolution, point-by-point grouping convolution, and channel rearrangement. It retains the design idea of multiscale feature graph detection of SSD network model. This model ensures a slight decline in detection accuracy while greatly reduces the amount of computation generated by the network operation, thereby greatly improving the detection rate. A data set for the task of object detection and recognition of indoor mobile robot is made. The S-SSD lightweight network model is superior to the original SSD network model and tiny-YOLO lightweight network model in terms of detection accuracy and detection rate, and can simultaneously meet the requirement of detection accuracy and real-time performance in the task of indoor object detection and recognition of mobile robot. These findings are verified through the comparative experiments of object detection accuracy and detection rate and real-time object detection and recognition of mobile robot under the actual indoor scene.

Polyacrylonitrile mesoporous composite membranes with high separation efficiency prepared by fast freeze-extraction process

Ruixue Lv,Faizal Soyekwo,Qiugen Zhang,Runsheng Gao,Jianyang Wu,Yan Qu,Aimei Zhu,Qinglin Liu 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.49 No.-

Polymer mesoporous membranes are widely employed in many membrane processes includingultrafiltration and dialysis, and become more crucial with increasing demand in chemical and lifefields. Here we report a highly-efficient polymer membrane with sub-5 nm pores and highflux frompolyacrylonitrile (PAN) nanoparticles produced from dilute PAN solution via fast freeze-extractionprocess. The25 nm-size PAN nanoparticles forming brad-like chains are dispersed in ethanol solutionand used to prepare the membrane byfiltration-assisted assembly method across a macroporoussupport. Effects of solvents and usage of PAN on membrane formation is studied in detail. The resultantmembranes comprise of the nanoparticles stacked on the support to form a mesoporous separation layerwith a controllable thickness and a cut-off of below 5 nm. They exhibit excellent separation performancesin ultrafiltration of protein and nanoparticle solutions. Typically, the membrane with 94.6% rejection of5 nm gold nanoparticles has a pure waterflux of 823 L m 1 h 1 bar 1 and perfect rejection for ferritinmolecules and 10 nm gold nanoparticles. The newly developed membranes should have wide applicationin chemical, environment and lifefields.

A Voronoi path planning extracted from improved skeleton for dynamic environments

Lin Jiang,Jun Li,Yuxin Hu,Feng Pan,Jianyang Zhu,Bin Lei,Rui Lin 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.4

Aiming at the problems that the robot being in the process of navigation cannot meet the requirements of real-time and accuracy at the same time, moreover is too close to obstacles and lacks the initiative to avoid obstacles, a Voronoi diagram algorithm for improved skeleton extraction suitable for dynamic environment is proposed. On the one hand, firstly the grid map is preprocessed by binarization, corrosion and expansion, so the reduced skeleton map suitable for navigation is obtained, then the reduced skeleton map is extracted for searching the global path, finally the improved cubic spline smoothing algorithm is used to optimize the global path each planned, thus overcoming the defects of bloated and tortuous in the path obtaining by original Voronoi diagram algorithm. On the other hand, the position information of all obstacles is obtained by a single scan lidar. Firstly, segmenting and linearly fitting all laser point clouds to remove the known obstacles in the map. Then to mark new possible dynamic obstacles with circles of appropriate size. Secondly detecting dynamic obstacles by the alteration of their center coordinates, moreover, solving their motion equations. Finally expanding the cost map along the speed direction of dynamic obstacles and combining DWA dynamic window method to realize dynamic obstacle avoidance. Compared with the original DWA algorithm, it can predict the motion state of dynamic obstacles in advance, which improves the safety of the robot in the dynamic environment. Moreover, the effectiveness of the algorithm is verified by many simulation experiments and real environment experiments.