Evolution of vortices in the wake of an ARJ21 airplane: Application of the lift-drag model

Wake separation is crucial to aircraft landing safety and is an important factor in airport operational efficiency.The near-ground evolution characteristics of wake vortices form the foundation of the wake separation system design.In this study,we analysed the near-ground evolution of vortices in the wake of a domestic aircraft ARJ21 initialised by the lift-drag model using large eddy simulations based on an adaptive mesh.Evolution of wake vortices formed by the main wing,flap and horizontal tail was discussed in detail.The horizontal tail vortices are the weakest and dissipate rapidly,whereas the flap vortices are the strongest and induce the tip vortex to merge with them.The horizontal tail and flap of an ARJ21 do not significantly influence the circulation evolution,height change and movement trajectory of the wake vortices.The far-field evolution of wake vortices can therefore be analysed using the conventional wake vortex model.

Analysis of static structural mechanics of vertical axis wind turbine with lift-drag combined starting structures

The finite element analysis was carried out for a composite vertical axis wind turbine with lift-drag combined starting structures to ensure the structure safety of a vertical axis wind turbine(VAWT).The static and modal analysis of rotor of a composite vertical axis wind turbine was conducted by using ANSYS software.The relevant contour sketch of stress and deformation was obtained.The analysis was made for static structural mechanics,modal analysis of rotor and the total deformation and vibration profile to evaluate the influence on the working capability of the rotor.The analysis results show that the various structure parameters lie in the safety range of structural mechanics in the relative standards.The analysis showing the design safe to operate the rotor of a vertical axis wind turbine.The methods used in this study can be used as a good reference for the structural mechanics′analysis of VAWTs.

Influence of Flap Parameters on the Aerodynamic Performance of a Wind-Turbine Airfoil

A numerical method has been used to analyze the flow field related to a NACA 0015 airfoil with and without a flap and assess the influence of the flap height and angle on the surface pressure coefficient,lift coefficient,and drag coefficient.The numerical results demonstrate that the flap can effectively improve the lift coefficient of the airfoil;however,at small attack angles,its influence is significantly reduced.When the angle of attack exceeds the critical stall angle and the flap height is 1.5%of the chord length,the influence of the flap becomes very evident.As the flap height increases,the starting point of the separation vortex gradually moves forward and generates a larger wake vortex.Optimal aerodynamic characteristics are obtained for 1.5%(of the chord length)flap height and a 45°flap angle;in this case,the separation vortex is effectively reduced.

The Full Flowpath Analysis of a Hypersonic Vehicle

A numerical study has been carried out to investigate the full flow path and aerodynamic characteristics of a hypersonic vehicle at a 7.0 free stream Mach number. Results indicate that the inlet started and unstarted operations have remarkable effects on the flow pattern of the full flow path. When the inlet operates in a started mode, the transverse pressure gradient generated by the forebody alters the air captured characteristics and the entering flow quality of the inlet. Furthermore, the expansion process of the nozzle jet flow is obviously affected by the external flow field around the afterbody with the cross section shape transiting from a near rectangle at the exit of the nozzle to a near triangle at the tail of the vehicle. When the inlet operates in an unstarted mode, the aerodynamic instability can be observed in the full flow path of the vehicle. Due to the oscillation of the external compressed shock wave and nozzle jet flow, the aerodynamic characteristics of the vehicle vary periodically with the lift-drag ratio changing from 0.25 to 2.09. Finally, by comparing to the experimental data, the reliability of the CFD is verified.

Functional design of wind turbine airfoils based on roughness sensitivity characteristics

To improve aerodynamic performance of wind turbine airfoils,the shape profile characteristic of the airfoil is investigated.Application of conformal transformation,one functional and integrated expression of wind turbine airfoils is presented.Using the boundary layer theory,the aerodynamic model with roughness of wind turbine airfoils is introduced by studying flow separation around the airfoil.Based on the shape expression and aerodynamic performance of airfoils,the function design of wind turbine airfoils is carried out that the maximum lift-drag ratio and low roughness sensitivity are designed objects.Three wind turbines airfoils with different thickness are gained which are used at tip part of blades.As an example,the aerodynamic performance of one designed airfoil with relative thickness of 15%is simulated in different conditions of clean surface,rough surface,laminar flow and turbulent flow.The comparison of aerodynamic performance between the designed airfoil and one popular NACA airfoil is completed which can verify the better performance of the designed airfoil and reliability of the designed method.

AERODYNAMIC OPTIMIZATION FOR TURBINE BLADE BASED ON HIERARCHICAL FAIR COMPETITION GENETIC ALGORITHMS WITH DYNAMIC NICHE

A global optimization approach to turbine blade design based on hierarchical fair competition genetic algorithms with dynamic niche （HFCDN-GAs） coupled with Reynolds-averaged Navier-Stokes （RANS） equation is presented. In order to meet the search theory of GAs and the aerodynamic performances of turbine, Bezier curve is adopted to parameterize the turbine blade profile, and a fitness function pertaining to optimization is designed. The design variables are the control points＇ ordinates of characteristic polygon of Bezier curve representing the turbine blade profile. The object function is the maximum lift-drag ratio of the turbine blade. The constraint conditions take into account the leading and trailing edge metal angle, and the strength and aerodynamic performances of turbine blade. And the treatment method of the constraint conditions is the flexible penalty function. The convergence history of test function indicates that HFCDN-GAs can locate the global optimum within a few search steps and have high robustness. The lift-drag ratio of the optimized blade is 8.3% higher than that of the original one. The results show that the proposed global optimization approach is effective for turbine blade.

Multi-point airfoil optimization for axial-flow fan

Airfoil is the element of fan blade design. It is strongly anticipated to design a fan of ave- raged high performance over a wide operation range. Multi-point optimization design of airfoil for axial flow fan was proposed over specific operation range. Weighted objective function of airfoil lift-drag ratio was constructed for several operation points around the designing one. Airfoil was defined by parametric B-spline curve of limited shape controlling points. Results show that normal standard airfoils have remained spaces to be optimized under specific operation conditions. Airfoil performance is sensitive to flow′s Reynolds number and cascade solidity. Predicting flow transition along airfoil profile is essential to search for optimized one. Optimized airfoil of wide operation range is possible to obtain with prescribed fitness function. Obtainments of multi-point optimization may be relatively lower at design point, but positive obtainments are achieved at off-design ones. Resulted airfoil is specially suitable for axial flow fans operating frequently at off-design point such as air condition coolers.

Geochemical Characteristics and Petrogenesis of Permian Basaltic Rocks in Keping Area,Western Tarim Basin:A Record of Plume-Lithosphere Interaction

ABSTRACT： The two basalt flows in Kupukuziman （库普库兹满） Formation of Keping （柯枰） area are the typical products of Permian magmatism. Based on systematic field investigations, we carried out geochemical studies on representative Keping basalts. The results show that the SiO2 contents in basalts range from 44.69 wt.% to 51.68 wt.%, and the total alkalis range from 4.05 wt.% to 5.5 wt.%, belonging to alkaline basalts. The Ti/Y=468.27-565.35 and TIO2=（2.88-3.82） wt.% compared to those of the high-Ti basalts in Emeishan （峨眉山） large igneous province （LIP） （TIO2=（3.58-5.21） wt.%, Ti/Y〉500, Xiao et al., 2004）. The contents of MgO and compatible elements Cr （12.9-18.6 ppm）, Ni （13.7-22.7 ppm）, and Co （39.6-50.2 ppm） are low, which suggest that the samples have undergone varying grades of fractional crystallization. All the samples have uniform REE and other trace element characteristics, with enriched LREE and LILE relative to HREE and HFS, similar REE patterns without Eu anomaly. The basalts are also show slightly depleted of Ta and Nb. They have higher initial STSr/S6Sr ratios （0.707 211-0.708 300）, lower tNd（t） values （-2.47 to -4.14）, and a narrow range of （208pb/204pb）t=37.535 2-38.297 7, （207pb/204pb）~=15.435 7-15.517 0, and （206Pb/204pb）t=17.206 5-17.874 7 ratios. The Ce/Y versus Zr/Nb diagram shows that the parent magmas were originated from low-degree partial melting of the garnet-lherzolite. The analysis results based on geochemical studies seem all point to the same conclusion that the Keping basalts have formed as a product of the interaction between the plume-derived melts and the lithosphere.Geochemical Characteristics and Petrogenesis of Permian Basaltic Rocks in Keping Area, Western Tarim Basin

Multi-objective optimization of shock control bump on a supercritical wing

Based on the supercritical ＂wingl＂ which was released in the DPW-III conference, multi-objective optimization has been done to increase the lift-drag ratio at cruise condition and improve transonic buffet boundary and drag-rise performance. Hicks-Henne shape functions are used to represent the bump shape. In the design optimization to increase lift-drag ratio, the objectives involve the cruise point and three other off-design points nearby. In the other optimization process to improve buffet and drag-rise performance, three buffet onset points near the cruise point and one drag-rise point are selected as the design points. Non-dominating sort genetic algorithm II （NSGA-II） is used in both processes. Additionally, individual analysis for every selected point on the Pareto frontier is conducted in order to avoid local convergence and achieve global optimum. Re- sults of optimization for aerodynamic efficiency show a decrease of 11 counts in drag at the cruise point. Drag at nearby off-design points are also reduced to some extent. Similar approaches are made to improve buffet and drag-rise characteristics, resulting in significant improvements in both ways.

Lasing characteristics of curved semiconductor nanowires

The characteristics of curved semiconductor nanowire （NW） lasers were investigated. The red-shift in the laser spectra with increasing bending angles can be observed much more clearly than that in the photolumi- nescence （PL） spectra. Due to oscillation of light in resonant cavity, the bending loss of laser exhibits multiple times amplification of that of PL. Furthermore, an abnormal phenomenon of dominant peak switching is found in curved NWs when increasing the pump power, which has been first discovered and reported.

Clinical characteristics of patients readmitted for stroke with double anti-platelet therapy after percutaneous coronary intervention

Background The clinical characteristics of stroke patients treated with double anti-platelet therapy （DAPT） after percutaneous coronary intervention （PCI） is not clear. Methods In total, 2675 patients under- went PCI and DAPT in Guangdong General Hospital, and 68 out of them were hospitalized due to suspected stroke, of whom 23 were diagnosed as having stroke. Data of the 23 stroke patients were collected and tradi- tional risk factors associated with stroke were analyzed retrospectively. Results The mean age of these pa- tients was 75.6± 8.7 years, and 20 （87.0%） were males. Notably, 19 patients were complicated with hyper- tension, 7 with diabetes mellitus, 7 with previous history of stroke, none with atrial fibrillation （AF） or patent foramen ovale （PFO）. Specifically, 22 patients were diagnosed with ischemic stroke, and 1 patient with hemorrhagic stroke. Conclusion Stroke in patients treated with DAPT after PCI was correlated with ad- vanced age, gender, hypertension, diabetes mellitus, stroke history. Long term electrocardiography （ECG） may be needed for the diagnosis of AF, while trans-esophageal echocardiography （TEE） may be needed for PFO.