A study of airfoil parameterization,modeling, and optimization based on the computational fluid dynamics method

An excellent airfoil with a high lift-to-drag ratio may decrease oil consumption and enhance the voyage. Based on NACA 0012, an improved airfoil is explored in this paper. The class/shape function transformation has been proved to be a good method for airfoil parameterization, and in this paper it is modified to improve imitation accuracy. The computational fluid dynamics method is applied to obtain numerically the aerodynamic parameters of the parameterized airfoil, and the result is proved credible by comparison with available experimental data in the open literature. A polynomial-based response surface model and the uniform Latin hypercube sampling method are employed to decrease computational cost. Finally, the nonlinear programming by quadratic Lagrangian method is utilized to modify the multi-island genetic algorithm, which has an improved optimization effect than the method used on its own. The obtained result shows that the modified class/shape function transformation method produces a better imitation of an airfoil in the nose and tail regions than the original method, and that it will satisfy the tolerance zone of the model in a wind tunnel. The response surface model based on the uniform Latin hypercube sampling method gives an accurate prediction of the lift-to-drag ratio with changes in the design variables. The numerical result of the flow around the airfoil shows reasonable agreement with the experimental data graphically and quantitatively. Ultimately, an airfoil with better capacity than the original one is acquired using the multi-island genetic algorithm based nonlinear programming by quadratic Lagrangian optimization method. The pressure contours and lift-to-drag ratio along with the attack angle have been compared with those of the original airfoil, and the results demonstrate the strength of the optimized airfoil. The process for exploring an improved airfoil through parameterization to optimization is worth referencing in future work.     

不同密实度网衣周围流场数值模拟

将网衣进简化为平面透空薄板,应用有限体积法求解湍流模型,计算了不同密实度网衣与流场的耦合作用。结果表明,当流速和冲角一定时,密实度越大流速衰减越明显,并且网衣背流区上下两侧的流速增加也越大。随着冲角增大流速衰减越明显,并且阻力系数也随之增大,举力系数先增大后减小,在冲角45°时举力系数最大,在冲角为90度时,举力系数减小为0。     

Kinematic optimization of 2D plunging airfoil motion using the response surface methodology

The propulsive efficiency of a plunging NACA0012 airfoil is maximized by means of a simple numerical optimization method based on the response surface methodology (RSM). The control parameters are the amplitude and the reduced frequency of the harmonic sinusoidal motion. The 2D unsteady laminar flow around the plunging airfoil is computed by solving the Navier-Stokes equations for three Reynolds number values (Re = 3.3×10³, 1.1×10⁴, and 2.2×10⁴). The Nelder-Mead algorithm is used to find the best control parameters leading to the optimal propulsive efficiency over the constructed response surfaces. It is found that, for a given efficiency level and regardless of the considered Re value, it is possible either to obtain high thrust by selecting a high oscillation frequency or to reduce the input power by adopting a low plunging amplitude.     

大风量空调箱内空气均流的数值模拟研究

为使大风量、高风速空调箱内的空气流能够迅速地实现均流,开发出了一种草帽型均流板。该均流板能够使空气在仅为0．4～0．6m的距离内将空气由40m／s降低到2．5m／s,并使空气在蒸发器迎风面上均匀分布,以提高蒸发器的换热效果,减小蒸发器结霜的可能性．提高机组的能效比。     

PIV技术在油品调和流场测试中的应用

利用相似理论建立数学模型,应用激光粒子测速仪PIV,以两种不同的油品为介质,有机玻璃油罐为载体,使用环形喷管,模拟了油品的调和,进行了速度场的测量。从而得到了同一个截面的平均速度矢量场和涡量场,分析了不同雷诺数对流场的影响,以及对应的涡量变化。通过实验表明,PIV测试油品调和的流场是一种可行和有效的实验方法。     

五孔球探针旋转流场测量的应用方法与误差探讨

介绍五孔球探针的基本结构和使用方法。通过深入探讨气体绕流球体的的原理,分析了在调节探针方位确定气流方向时出现多个平衡点的原因,并进行实验验证,提出在复杂流场中确定正确的气流方向角的三个基本判据。从压力测量、探针位置精度、速度梯度和静压梯度等方面分析了流场测量误差的来源,并指出了实现误差控制的相应措施。     

流场可视化的便携式烟风洞装置

文章介绍了一种整体长度为0.64m,重约为4kg,轻巧、便携的烟风洞装置的特点.该装置有着良好的烟气发生装置和烟气流动质量,方便的燃油补充机构和试件磁力固定结构,是流体力学学科中一种较完美的教学工具.轻巧的结构使得这种烟风洞装置可以很方便地携入教室用于教学演示.各种研究对象在风洞中的绕流情况可以很好地用高质量的数字照片显示出来,这些照片如圆柱绕流,平面叶栅的流线分布,都能较好地反映了流体力学流动基本规律;同时,通过对一个模型汽车所进行的流体力学数值计算（FLUENT）与实验对比,其结果显示出它们的流动状态吻合较好,说明这种便携式烟风洞的良好性能.     

Assessment of semi-empirical mass transfer correlations for pervaporation treatment of wastewater contaminated with chlorinated hydrocarbons

INTRODUCTION Chlorinated hydrocarbons, a class of widely used dry-cleaning liquids, industrial organic solvents, and degreasers, increasingly find their way into drinking water sources, thus posing a very serious health and environmental problem (Love and Eliers, 1982). These organic solvents are known for their stability in the environment and cancer-causing po- tency and cannot be effectively and economically eliminated by current conventional treatment tech- nologies. One of the few av…     

玉米螟成虫羽化早期飞行能力研究

利用昆虫飞行磨测试玉米螟Ostrinia furnacalis成虫羽化早期1~4日龄在室温条件下的飞行能力,最终获得22头个体的飞行数据,其中最大累计飞行距离为5 952.06 m,最长累计飞行时间为7 279.55 s,平均飞行速度最大为1.23 m/s,最大飞行速度1.55 m/s,最久单次起飞飞行时间最大值为4 902.21 s,最远单次起飞平均速度最大值为1.28 m/s,最远单次起飞飞行距离最大值为2 895.92 m.统计分析结果表明：玉米螟羽化早期的雌雄虫在飞行距离、飞行时间、平均飞行速度、最大飞行速度、最久单次起飞所飞行的时间、最远单次起飞平均速度、最久单次起飞所飞行的距离等方面差异均不显著（P〉0.05）.     

小型垂直轴风力机叶片气动特性模拟与分析

针对NACA4412翼型风力发电机扰流流动特点,建立了二维和三维不可压缩湍流模型,并对基于流体连续性方程和N-S方程及k-ε湍流模型的二维流场进行数值模拟计算。采用多参考系计算（MRF）模型,用FLUENT模拟了流场内翼型截面的受力情况和速度分布情况,得到了NACA4412翼型风机的气动特性。     

雷诺实验仪的改进与创新

雷诺实验是显示层流和湍流的重要实验。在传统雷诺实验仪的基础上,自主设计开发了新型的雷诺实验仪,该实验装置具有自循环水系统、贮水箱水头稳定以及示踪剂颜色自动消失等特点。通过实验教学使用,明显比传统的雷诺实验仪具有优越性,解决了传统雷诺实验仪存在的一些弊端,值得在高校流体力学实验教学中推广使用。     

Investigation on critical equilibrium of trapped air pocket in water supply pipeline system

A trapped air pocket can cause a partial air lock in the top of a hump pipe zone. It increases the resistance and decreases the hydraulic cross section, as well as the capacity of the water supply pipeline. A hydraulic model experiment is conducted to observe the deflection and movement of the trapped air pocket in the hump pipe zone. For various pipe flow velocities and air volumes, the head losses and the equilibrium slope angles are measured. The extra head losses are also obtained by reference to the original flow without the trapped air pocket. Accordingly, the equivalent sphere model is proposed to simplify the drag coefficients and estimate the critical slope angles. To predict the possibility and reduce the risk of a hump air lock, an empirical criterion is established using dimensional analysis and experimental fitting. Results show that the extra head losses increase with the increase of the flow velocity and air volume. Meanwhile, the central angle changes significantly with the flow velocity but only slightly with the air volume. An air lock in a hump zone can be prevented and removed by increasing the pipe flow velocity or decreasing the maximum slope of the pipe.     

过冷流动沸腾热传递的分形模型

提出过冷流动沸腾热传递的分形模型,根据加热表面活化点的分形分布得到了过冷流动沸腾热流密度的表达式。从该模型中发现过冷流动沸腾热流密度是壁面过热度、流体的过冷度、流体的主流速度与流体的接触角、流体物理特性的函数关系,并且没有增加新的经验常数。模型预测的结果与实验数据进行了比较,两者是极好的吻合。     

Experimental investigation on mixing enhancement mechanism of turbulent jet flow with tabbed nozzle

Flow visualization and hot-wire measurement techniques were combined to investigate the influence of the size and number of tabs on jet flow field and vortex structure generation mechanism. Streamwise vortices generated by the tabs of different sizes and numbers were ob- served from the flow visualization images. Combined with flow visualization, hot-wire measurement gave a quantitative insight of the effect of various tabbed jet flows. Instantaneous two-component velocity signals （longitudinal and transverse velocity components） at different cross sections along radius direction and streamwise direction with different tabbed jet nozzles were measured using hot-wire anemometer. Average flow field parameters of tabbed jet flow such as mean velocity, turbulence intensity, vorticity were analyzed and the effects of tabs with different sizes and numbers were compared with that of circular no-tab jet flow. It is revealed that the generation of a series of counter-rotating quasi-streamwise vortices, azimuthal vortices and double-row azi-muthal vortex are the reasons for mixing enhancement of tabbed turbulent jet flow.     

几种节流装置流体动力特性的实验研究

介绍了几种不同节流装置(即流量计)的结构特点、在风洞中的校准方法、校准结果以及对结果的应用,并对几种节流装置的流体动力特性作了分析,结果表明,在几种节流装置中,除翼型节流装置外,流量测量精度较高的节流装置的压力损失系数较大。     

利用2×2纤锥表面等离子共振传感液体折射率

介绍了2×2纤锥等离子共振的工作原理,并用其对液体折射率进行传感。制作的表面等离子共振传感器用于检测甘油水溶液的折射率时,观测到被测液体折射率在(1.448,1.4515)区间变化时,等离子共振波长在(1450,1593)nm区间移动,两者间呈线性对应关系。系统的传感分辨率为2.448×10-5 RIU。     

水工有压隧洞出口断面压强及输水能力的计算

水工有压隧洞的水力计算是一个很复杂的水力学问题，本文结合管流的计算公式，利用算例详细介绍了水工有压隧洞出口压强及水力计算方法。     

Low-Temperature Plasma Induced Grafting of 2-Methacryloyloxyethyl Phosphorylcholine onto Poly（tetrafluoroethylene） Films

Modification of poly(tetrafluoroethylene) (PTFE) films with 2-methacryloyloxyethyl phosphorylcholine (MPC) was performed by low-temperature plasma treatment and grafting polymerization. Surface properties of PTFE were characterized by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra, X-ray photoelectron spectroscopy (XPS), and static contact angle. The results show that MPC has been grafted onto PTFE film surface successfully. Contact angle for the modified PTFE films in the water decreased from 108° to 58.25°, while surface energy increased from 17.52 mN/m to 45.47 mN/m. The effects of plasma treatment time, monomer concentration and grafting time on degree of grafting were determined. In the meanwhile, blood compatibility of the PTFE films was studied by checking thrombogenic time of blood plasma.     

用倾斜气轨系统与Spss测定重力加速度

用垫块调整气轨的倾斜角,使滑行器在自身重力作用下沿气轨表面直接做功,使用智能计时系统精准测出滑块在气轨斜面定点位置的速度。由测量原理及不确定度分析,对照测量数据,引入Spss的曲线估计功能分析得到速长综合量与垫块高度的定标曲线,并验证出速长综合量与垫块高度存在线性关系,由此标定出重力加速度,并用置信概率为95%的不确定度对其进行了合理的分析和评定,得到更加合理的实验结果。     

分子力与分子间距离关系的模拟演示

本介绍了用表面张力与水膜高度来模拟演示分子力与分子间距离关系的方法，阐述了演示原理，描述了演示过程，并给出简单演示装置图．