TRANSONIC DRAG REDUCTION ON SUPERCRITICAL WING SECTION USING SHOCK CONTROL BUMPS

Two-dimensional and three-dimensional shock control contour bumps are designed for a supercritical wing section with the aim of transonic wave drag reduction. The supercritical airfoil （NASA SC （02）-0714） is selected considering the fact that most modern jet transport aircrafts that operate in the transonic flow regime （cruise at transonic speeds） employ supercritical airfoil sections. Here it is to be noted that a decrease in the transonic wave drag without loss in lift would result in an increased lift to drag ratio, which is a key range parameter that can potentially increase both the range and endurance of the aircraft. The major geometric bump parameters such as length, height and span are altered for both the two-dimensional and three-dimensional bumps in order to obtain the optimum location and shape of the bump. Once an optimum standalone three-dimensional bump is acquired, an array of bumps is manually placed spanwise of an unswept supercritical wing and analyzed under fully turbulent flow conditions. Different configurations are tested with varying three-dimensional bump spacing in order to determine the contribution of bump spacing on overall performance. The results show a 14% drag reduction and a consequent 16% lift to drag ratio rise at the design Mach number for the optimum arrangement of bumps along the wing span.

Research advances in enhanced coal seam gas extraction by controllable shock wave fracturing

With the continuous increase of mining in depth,the gas extraction faces the challenges of low permeability,great ground stress,high temperature and large gas pressure in coal seam.The controllable shock wave(CSW),as a new method for enhancing permeability of coal seam to improve gas extraction,features in the advantages of high efficiency,eco-friendly,and low cost.In order to better utilize the CSW into gas extraction in coal mine,the mechanism and feasibility of CSW enhanced extraction need to be studied.In this paper,the basic principles,the experimental tests,the mathematical models,and the on-site tests of CSW fracturing coal seams are reviewed,thereby its future research directions are provided.Based on the different media between electrodes,the CSW can be divided into three categories:hydraulic effect,wire explosion and excitation of energetic materials by detonating wire.During the process of propagation and attenuation of the high-energy shock wave in coal,the shock wave and bubble pulsation work together to produce an enhanced permeability effect on the coal seam.The stronger the strength of the CSW is,the more cracks created in the coal is,and the greater the length,width and area of the cracks being.The repeated shock on the coal seam is conducive to the formation of complex network fracture system as well as the reduction of coal seam strength,but excessive shock frequency will also damage the coal structure,resulting in the limited effect of the enhanced gas extraction.Under the influence of ground stress,the crack propagation in coal seam will be restrained.The difference of horizontal principal stress has a significant impact on the shape,propagation direction and connectivity of the CSW induced cracks.The permeability enhancement effect of CSW is affected by the breakage degree of coal seam.The shock wave is absorbed by the broken coal,which may hinder the propagation of CSW,resulting in a poor effect of permeability enhancement.When arranging two adjacent boreholes for CSW permeability enhancement test,the spacing of boreholes should not be too close,which may lead to negative pressure mutual pulling in the early stage of drainage.At present,the accurate method for effectively predicting the CSW permeability enhanced range should be further investigated.

Transonic buffet control research with two types of shock control bump based on RAE2822 airfoil

Current research shows that the traditional shock control bump（SCB） can weaken the intensity of shock and better the transonic buffet performance. The author finds that when SCB is placed downstream of the shock, it can decrease the adverse pressure gradient. This may prevent the shock foot separation bubble to merge with the trailing edge separation and finally improve the buffet performance. Based on RAE2822 airfoil, two types of SCB are designed according to the two different mechanisms. By using Reynolds-averaged Navier-Stokes（RANS） and unsteady Reynolds-averaged Navier-Stokes（URANS） methods to analyze the properties of RAE2822 airfoil with and without SCB, the results show that the downstream SCB can better the buffet performance under a wide range of freestream Mach number and the steady aerodynamics characteristic is similar to that of RAE2822 airfoil. The traditional SCB can only weaken the intensity of the shock under the design condition. Under the off-design conditions, the SCB does not do much to or even worsen the buffet performance. Indeed, the use of backward bump can flatten the leeward side of the airfoil, and this is similar to the mechanism that supercritical airfoil can weaken the recompression of shock wave.

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.

Shock control bump optimization for a low sweep supercritical wing

Shock control bumps are a promising technique in reducing wave drag of civil transport aircraft flying at transonic speeds.This paper investigates the optimization of 3D shock control bumps on a supercritical wing with a sweep angle of 16°at the1/4 chord.A similar supercritical wing with a higher sweep angle of 24.5°at the 1/4 chord has been adopted as a baseline for the study.Numerical results show that the drag coefficient of the low sweep wing with the optimized 3D shock control bumps is reduced below that for the high sweep wing,indicating shock control bumps can be used as an effective means to reduce the wave drag caused by reducing the wing sweep angle.From the point of view of the wing structure design,lower sweep angle will also bring the benefits of weight reduction,resulting in further fuel reduction.

Numerical evaluation of passive control of shock wave/boundary layer interaction on NACA0012 airfoil using jagged wall

Shock formation due to flow compressibility and its interaction with boundary layers has adverse effects on aerodynamic characteristics, such as drag increase and flow separation. The objective of this paper is to appraise the practicability of weakening shock waves and, hence, reducing the wave drag in transonic flight regime using a two-dimensional jagged wall and thereby to gain an appropriate jagged wall shape for future empirical study. Different shapes of the jagged wall, including rectangular, circular, and triangular shapes, were employed. The numerical method was validated by experimental and numerical studies involving transonic flow over the NACA0012 airfoil, and the results presented here closely match previous experimental and numerical results. The impact of parameters, including shape and the length-to-spacing ratio of a jagged wall, was studied on aerodynamic forces and flow field. The results revealed that applying a jagged wall method on the upper surface of an airfoil changes the shock structure significantly and disintegrates it, which in turn leads to a decrease in wave drag. It was also found that the maximum drag coefficient decrease of around 17 % occurs with a triangular shape, while the maximum increase in aerodynamic efficiency（lift-to-drag ratio）of around 10 % happens with a rectangular shape at an angle of attack of 2.26？.

NUMERICAL MODELING OF MULTI-CYLINDER ELECTRO-HYDRAULIC SYSTEM AND CONTROLLER DESIGN FOR SHOCK TEST MACHINE

A high fidelity dynamic model of a high-energy hydraulically-actuated shock test machine for heavy weight devices is presented to satisfy the newly-built shock resistance standard and simulate the actual underwater explosion environments in laboratory as well as increase the testing capability of shock test machine. In order to produce the required negative shock pulse in the given time duration, four hydraulic actuators are utilized. The model is then used to formulate an advanced feedforward controller for the system to produce the required negative waveform and to address the motion synchronization of the four cylinders. The model provides a safe and easily controllable way to perform a ＂virtual testing＂ before starting potentially destructive tests on specimen and to predict performance of the system. Simulation results have demonstrated the effectiveness of the controller.

Gain Scheduling Control of Nonlinear Shock Motion Based on Equilibrium Manifold Linearization Model

The equilibrium manifold linearization model of nonlinear shock motion is of higher accuracy and lower complexity over other models such as the small perturbation model and the piecewise-linear model. This paper analyzes the physical significance of the equilibrium manifold linearization model, and the self-feedback mechanism of shock motion is revealed. This helps to describe the stability and dynamics of shock motion. Based on the model, the paper puts forwards a gain scheduling control method for nonlinear shock motion. Simulation has shown the validity of the control scheme.

Control of Transonic Shock Wave Oscillation over a Supercritical Airfoil

In the present study, a numerical investigation is carried out on the aerodynamic performance of a supercritical airfoil RAE 2822. Transonic flow fields are considered where self-excited shock wave oscillation prevails. To control the shock oscillation, a passive technique in the form of an open rectangular cavity is introduced on the upper surface of the airfoil where the shock wave oscillates. Reynolds Averaged Navier-Stokes (RANS) equations have been used to predict the aerodynamic behavior of the baseline airfoil and airfoil with cavity at Mach number of 0.729 and at angle of attack of 5°. The aerodynamic characteristics of the baseline airfoil are well validated with the available experimental data. It is observed that the introduction of a cavity around the airfoil upper surface can completely stop the self-excited shock wave oscillation and successively improve the aerodynamic characteristics.

Optimization of passive control performance for different hard disk drives subjected to shock excitation

Laptop personal computers(LPCs) and their components are vulnerable devices in harsh mechanical environments. One of the most sensitive components of LPCs is hard disk drive(HDD) which needs to be protected against damages attributable to shock and vibration in order to have better magnetic read/write performance. In the present work, a LPC and its HDD are modeled as two degrees of freedom system and the nonlinear optimization method is employed to perform a passive control through minimizing peak of HDD absolute acceleration caused by a base shock excitation. The presented shock excitation is considered as half-sine pulse of acceleration. In addition, eleven inequality constraints are defined based on geometrical limitations and allowable intervals of lumped modal parameters. The target of the optimization is to reach optimum modal parameters of rubber mounts and rubber feet as design variables and subsequently propose new characteristics of rubber mounts and rubber feet to be manufactured for the HDD protection against shock excitation. The genetic algorithm and the modified constrained steepest descent algorithm are employed in order to solve the nonlinear optimization problem for three widely-used commercial cases of HDD. Finally, the results of both optimization methods are compared to make sure about their accuracy.

Shockwave–boundary layer interaction control by plasma aerodynamic actuation:An experimental investigation

The potential of controlling shockwave-boundary layer interactions （SWBLIs） in air by plasma aerodynamic actua- tion is demonstrated. Experiments are conducted in a Mach 3 in-draft air tunnel. The separation-inducing shock is generated with a diamond-shaped shockwave generator located on the wall opposite to the surface electrodes, and the flow properties are studied with schlieren imaging and static wall pressure probes. The measurements show that the separation phenomenon is weakened with the plasma aerodynamic actuation, which is observed to have significant control authority over the inter- action. The main effect is the displacement of the reflected shock. Perturbations of incident and reflected oblique shocks interacting with the separation bubble in a rectangular cross section supersonic test section are produced by the plasma actuation. This interaction results in a reduction of the separation bubble size, as detected by phase-lock schlieren images. The measured static wall pressure also shows that the separation-inducing shock is restrained. Our results suggest that the boundary layer separation control through heating is the primary control mechanism.

断路器选相投切系统在换流站中的应用研究

在换流站滤波器组及换流变压器配置断路器选相投切系统,可改善断路器开合暂态过程,在取消合闸电阻工况下仍可避免对电力设备及系统造成冲击。基于多个换流站选相投切工程实施及调试经验,进行了换流站选相投切系统应用的调查。介绍了选相投切系统构成、选相投切要求、断路器配套及预测试方法等。重点针对滤波器组、换流变压器的选相投切应用,总结了控制策略、选相投切系统带电冲击试验,及工程使用中需重点关注的问题、设备运维要求等,为相关技术人员提供参考。试点工程在特高压断路器中创新性地采用取消合闸电阻、增设选相合闸的专项改造方案。断路器选相投切系统总体运行效果良好,为技术的推广积累了工程运行经验。

导弹等离子体合成射流流动控制技术综述与展望

在反导技术不断发展的背景下,为提高导弹的命中率,需要对导弹的机动性、快响应性等提出更高的要求。近年来,由于响应时间短、无机械部件、工作频带宽等优势,基于等离子体合成射流激励器的主动流动控制技术成为兵器科学与技术以及航空航天领域的研究热点。该技术在导弹的快响应气动力控制、横向主流干扰控制、激波控制、激波/边界层干扰控制等流动控制领域均展现出巨大的应用前景,为减小导弹的阻力、提高导弹的机动性、快响应性等提供了技术保障。结合近二十年来国内外的相关文献资料,以及多年的研究经验,对导弹等离子体合成射流流动控制技术的原理内涵、发展状况、关键问题等进行阐述和总结,以便为相关研究人员提供帮助。

激波/湍流边界层干扰中的自适应控制技术

从激波/湍流边界层干扰机理以及流动控制的迫切需求入手,从自适应涡流发生器、自适应鼓包、自适应微射流以及自适应次流循环四个方面对激波/湍流边界层干扰中的自适应控制技术研究进展进行了总结。分析认为,结合AI技术发展自适应流动控制技术,加速控制方式智能化,可作为新一代高超声速飞行器宽速域飞行的重要技术手段。具体来说,就是通过调节外加激励对高超声速飞行器不同区域实现局部流动加/减速、气动热防护、气动控制等功能,根据流场参数建立控制反馈回路,自适应调整局部流场结构,以满足工程实际需求。

体外冲击波响应型唑来膦酸钙纳米颗粒靶向控释对骨质疏松骨代谢及骨量的影响

目的研究体外冲击波(extracorporeal shock wave,ESW)响应型唑来膦酸(zoledronic acid,ZOL)钙纳米颗粒(ZOL-Ca nanoparticals,ZCNP)的制备及其靶向控释对骨质疏松骨代谢及骨量的影响。方法通过模板法以ZOL为磷源,CaCl2为钙源制备ZCNP。利用扫描电子显微镜、动态光散射对ZCNP进行表征。通过紫外可见吸收光谱及电感耦合等离子体光发射光谱法评估ZOL的负载以及载药率。利用CCK-8法检测ZCNP对鼠源骨髓单核细胞(bone marrow mononu-clear cells,BMMs)活力的影响;采用溶血实验检测ZCNP的生物相容性。通过荧光标记ZCNP对其骨靶向性进行验证。采用药物释放实验验证了ZCNP的ESW响应性。在体外,利用TRAP染色检验ZCNP的破骨抑制情况;ARS染色检验ZCNP对成骨活性的影响。在体内,利用卵巢摘除骨质疏松模型验证ZCNP对骨量的影响。结果ZCNP呈类球形结构,约60 nm。ZCNP的ZOL负载率为(59.68±1.48)%。ZCNP在0、0.01、0.1、1、10μmol/L浓度下对小鼠BMMs的细胞活性影响无明显差异(P>0.05)。ZCNP在ESW作用下可快速释放ZOL。ESW+ZCNP可抑制破骨细胞活性,促进成骨细胞增殖。ESW+ZCNP可明显提高卵巢摘除骨质疏松模型局部骨量。结论ESW响应型ZCNP可通过有效精准靶向控释,抑制破骨,促进成骨提升卵巢摘除模型局部骨量,预防骨质疏松性骨折。

基于高压气体驱动的爆炸波模拟激波管冲击波衰减历程控制方法

基于高压气体驱动的爆炸波模拟激波管,一般采用驱动段、喉部、膨胀段的结构形式,可产生特征与爆炸波接近的模拟冲击波,是实验室中开展长正压作用时间爆炸毁伤效应研究的理想平台。通过调整激波管的变截面结构和驱动段形状,实现冲击波超压衰减历程的控制,是此类爆炸波模拟激波管设计面临的核心问题之一。基于实验室现有的爆炸波模拟激波管结构,建立了激波管内一维流动数值计算模型;参考统计学理论,提出了基于决定系数的激波管模拟冲击波与标准爆炸波相似度评价方法;进而以变截面激波管的流动特性为基础,研究了驱动段形状对冲击波衰减历程的影响机理。研究结果表明:采用距离喉部越远、截面直径越小的驱动段形状,以决定系数为量化标准、优化驱动段形状,控制稀疏波、压缩波在激波管内的运动过程,可以获得接近于爆炸波指数衰减特征的模拟冲击波。

空间管路结构振动控制技术研究

飞行器在服役过程中,管路结构会产生大量级振动响应,严重时会发生断裂失效。振动控制是延缓管路结构失效,提升可靠性的主要途径。本文通过边界简化及焊接部位建模,建立了复杂空间三维管路结构动力学模型,模态仿真结果与试验模态结果对比最大误差小于3%。在此基础上,使用金属减振器进行振动控制。通过计算,获得随机振动载荷下使用金属减振器前后空间管路结构的减振效率为8.46%;通过试验获得金属减振器实际的减振效率达到14.26%。本文计算和试验结果表明使用金属减振器能够显著降低复杂空间管路结构的振动响应。

旋流后置型超声速分离器激波控制方法数值模拟

目的超声速分离是一种基于收缩-扩张喷管的新型气体净化与燃料气加工技术。旋流后置型超声速分离器中的旋流器通常设置在扩压段前,易诱发正激波并破坏分离器内部低温环境,同时,激波难以控制。因此,拟通过优化超声速分离器结构的方式削弱激波的影响。方法①基于热力学和空气动力学的原理,提出了一种适用于旋流后置型超声速分离器的激波控制理论;②根据该理论设计了一种能够控制激波的跨旋流结构,建立了该结构的普适性设计公式;③通过数值模拟研究,分析了跨旋流结构的倾斜角度、渐扩段长度、旋流器的叶片扭转角度3个重要结构参数对激波控制的影响。结果当跨旋流结构的倾斜角度为3.3°、渐扩段长度为107 mm、旋流器的叶片扭转角度为120°时,分离器具有最佳性能。结论相比传统的旋流后置型分离器,添加跨旋流结构可以保证流体流通面积在渐扩段持续增加,从而实现对激波的有效控制,以提高分离器的冷凝和分离效率。

损害控制复苏研究新进展

创伤失血性休克已成为人类死亡和伤残的重要原因,目前尚无最佳的救治方案,损害控制复苏(DCR)是一种较为先进的整合复苏策略,目前已被广泛应用于创伤失血性休克。创伤出血患者的病理生理基础常被称为死亡钻石(低体温、酸中毒、凝血功能障碍、低钙血症),DCR通过强调允许性低血压、限制性液体复苏和输血治疗、目标定向纠正凝血功能障碍、行损害控制手术纠正生理紊乱,挽救创伤患者生命。本综述旨在阐述DCR新的研究进展,加深对该理念的新认识。

基于磁流变减振器和天棚ON-OFF控制的汽车半主动悬架研究

介绍了磁流变减振器的特点与结构,论述了天棚ON-OFF控制的原理,基于磁流变减振器和天棚ON-OFF控制,对汽车半主动悬架进行运动仿真分析,并与被动悬架进行对比。研究结果表明,基于磁流变减振器和天棚ON-OFF控制的半主动悬架能够提升汽车行驶的稳定性。