COMPARISON OF THE EXPERIMENTAL AND COMPUTATIONAL STUDY ON THE EFFECTS OF VORTEX CONTROL BY DEFLECTING FLAPS ON A HIGHLY SWEPT DELTA WING

In order to investigate the effects of vortex control by deflecting flaps on the improvement of the aerodynamics of highly swept wings at large incidence, comparison of the experimental and numerical studies was conducted for a 74° delta wing equipped with an apex flap and leading edge flaps. In the experimental study, flow visualization and force measurement were employed and in the numerical study the pseudo compressibility method was utilized to solve the 3 D incompressible Navier Stokes equations. The flow visualization and numerical simulation show that two vortex systems generated on the apex flap and leading edge flaps interact in the form of mergence, and the downward deflection of the apex flap enhances the strength and delays the breakdown of the prime vortex at large incidence. The comparison of the aerodynamic characteristics illustrates that there are advantageous effects of deflecting flaps downward on the control of vortices.

Numerical Simulation of Wake Deflection Control around NACA0012 Airfoil Using Active Morphing Flaps

This study demonstrates an active flow control for deflecting a direction of wake vortex structures behind a NACA0012 airfoil using an active morphing flap. Two-dimensional direct numerical simulations are performed for flows at the chord Reynolds number of 10,000, and the vortex pattern in the controlled and noncontrolled wakes as well as the effect of an actuation frequency on the control ability are rigorously investigated. It is found that there is an optimum actuation-frequency regime at around F + = 2.00 which is normalized by the chord length and freestream velocity. The wake vortex pattern of the well-controlled case is classified as the 2P wake pattern according to the Williamson’s categorization [1] [2], where the forced oscillation frequency corresponds to the natural vortex shedding frequency without control. The present classification of wake vortex patterns and finding of the optimum frequency regime in the wake deflection control can lead to a more robust design suitable for vortex-induced-vibration (VIV) related engineering systems.

Hypothenar fat pad flap vs conventional open release in primary carpal tunnel syndrome:A randomized controlled trial

AIM To compared outcomes between the hypothenar fat pad flap(HTFPF) and conventional open carpal tunnel release(COR) in primary carpal tunnel syndrome(CTS). METHODS Forty-five patients(49 hands) were enrolled into the study from January 2014 to March 2016, 8 patients were excluded. Randomization was conducted in 37 patients(41 hands) by computer generated(Block of four randomization) into COR and HTFPF group. Nerve conduction study(NCS) included distal sensory latency(DSL), distal motor latency(DML), sensory amplitude (S-amp), motor amplitude(M-amp) and sensory nerve conduction velocity(SCV) were examined at 6 and 12 wk after CTR. Levine score, grip and pinch strength, pain [visual analog scale(VAS)], 2-point discrimination(2-PD), Semmes-Weinstein monofilament test(SWM), Phalen test and Tinel's sign were evaluated in order to compare treatment outcomes.RESULTS The COR group, 19 patients(20 hands) mean age 50.4 years. The HTFPF group, 20 patients(21 hands) mean age 53.3 years. Finally 33 patients(36 hands) were analysed, 5 patients were loss follow-up, 17 hands in COR and 19 hands in HTFPF group. NCS revealed significant difference of DSL in HTFPF group at 6 wk(P < 0.05) compared with the COR group. S-amp was significant improved postoperatively in both groups(P < 0.05) but not significant difference between two groups. No significant difference of DML, M-amp and SCV postoperatively in both groups and between two groups. Levine score, pain(VAS), grip and pinch strength, 2-PD, SWM, Phalen test and Tinel's sign were improved postoperatively in both groups, but there was no significant difference between two groups.CONCLUSION There is no advantage outcome in primary CTS for having additional HTFPF procedure in CTR. COR is still the standard treatment. Nevertheless, improvement of DSL and S-amp could be observed at 6 wk postoperatively.

On Belly-flap for Pitch Control at Transonic Airfoil

One of the issues about Blended-Wing-Body configuration （BWB） is its difficulty in pitch control due to the missing tail. To solve this problem, a novel pitch control surface, belly-flap, has been presented. In this paper, the feasibility of belly-flap being used as a transonic pitch control device for tailless configuration is investigated on a BWB in-body airfoil, using the computationalfluid dynamic （CFD） method. The size, location and deflection angle of the flap are studied to detect their effect on the aerodynamic characteristics. The results reveal that the bubble separation due to the belly-flap can affect shock position on the upper surface of the airfoil and change the surface pressure distribution. By choosing appropriate geometry parameters, the load distribution can be improved to obtain significant pitch-up moment increment in a wide angle of attack with no lift-loss and less lift-drag ratio decrement.

Human Memory/Learning Inspired Control Method for Flapping-Wing Micro Air Vehicles

The problem of flapping motion control of Micro Air Vehicles (MAVs) with flapping wings was studied in this paper.Based upon the knowledge of skeletal and muscular components of hummingbird, a dynamic model for flapping wing wasdeveloped.A control scheme inspired by human memory and learning concept was constructed for wing motion control ofMAVs.The salient feature of the proposed control lies in its capabilities to improve the control performance by learning fromexperience and observation on its current and past behaviors, without the need for system dynamic information.Furthermore,the overall control scheme has a fairly simple structure and demands little online computations, making it attractive for real-timeimplementation on MAVs.Both theoretical analysis and computer simulation confirms its effectiveness.

Redundant Hydraulic Secondary Flight Control Systems Behavior in Failure Conditions

The flight control systems, designed in order to assure the necessary safety level even in failure conditions, are generally characterized by a proper redundant layout. The redundancies must be designed in order to assure an adequate system behavior when some failures are present; in fact an incorrect layout may cause serious shortcomings concerning the response when some component is not operational. Therefore the usual correct design activities request the complete analysis of the system behavior in failure condition. The work analyses the response of a redundant secondary flight control hydraulic servo-mechanism equipped with some proper equalization devices, when some of the most probable and representative failures are present. It must be noted that the redundancy layout, designed in order to assure the necessary safety level even in failure conditions, may behave improperly during normal operations, if the system architecture is unsuitable, when manufacturing defects are present. The improper behavior, generally consisting of force fighting or speed fighting caused by different offsets or asymmetries between the two sections of the system, may be usually overcome by means of a suitable equalization device. Therefore, the system behavior during and following the failure transient greatly depends on both its redundancy architecture and related equalization device. The above mentioned problems have been studied by means of an appropriate physical-mathematical model of a typical electro-hydraulic servo-mechanism prepared to the purpose, performing a certain number of simulations of representative actuations in which different types of failures are accurately modeled. In the opinion of the authors, this paper concerns a topic quite neglected but important in the technical literature. At the best of the authors＇ knowledge, no specific scientific work in this field is available, excepting some industrial technical reports.

Numerical Analysis of Influence of Gurney Flaps Applied to Wind Turbines

The effect of Gurney flaps with different heights on the S809 airfoil and NH1500 blade is numerically simulated.The influence of the Gurney flap is analyzed at different wind speeds and the comparison of the aerodynamic performance is given between the blades with and without the Gurney flap.The results demonstrate that a Gurney flap added on the blade can greatly increase the efficiency of the wind turbine especially at high wind speeds.

Flutter Suppression of Long-Span Bridges Using Suboptimal Control

Based on the Theodorsen’s Theory of the aerodynamic forces on wing-aileron, the Scanlan’s Theory is expanded considering a deck-flap system. It is suggested that a new forced vibration method can acquire aerodynamic derivatives of this deck-flap system theoretically. After obtaining the wind induced forces, a deck-flap equation of motion in time domain is established to investigate its control law. Numerical simulation results indicate suboptimal control law of the deck-flap system can suppress the flutter effectively, and the flutter speed can be increased for desirable purpose.

基于ESO的仿蝙蝠扑翼飞行器姿态控制仿真

针对仿蝙蝠扑翼飞行器的纵向气动特性不稳定、易受扰动的问题,设计了一种基于扩张状态观测器(ESO)的姿态控制方法,实现了扑翼飞行器姿态的稳定与抗干扰控制。首先建立仿蝙蝠扑翼飞行器的动力学模型;进而在该模型基础上分析了扑翼飞行器的纵向稳定性;然后将系统的不确定部分与各种未知的外界扰动作为系统的总扰动,引入ESO模块对总扰动进行实时观测与跟踪;最后在原有的PID控制器中加入扰动补偿环节。数值仿真结果表明,基于ESO的控制算法对于仿蝙蝠扑翼飞行器的控制效果显著优于基于PID的控制方法,阶跃响应的调节时间加快41.27%,对系统输入的白噪声干扰波动峰值从6.02%降低到2.82%,正弦扰动的波动峰值从11.56%降低到3.22%。

一种单反馈通道振荡射流激励器设计

为了设计一种有利于分离控制的振荡射流激励器,选取单反馈通道的形式,重点研究第二喉道与扩张段参数对射流振荡特性与偏转襟翼分离控制效果的影响,并总结几何参数设计依据,完成激励器设计并对比了其与典型激励器的分离控制效果。结果表明:反馈段参数应使射流在混合段扩张部分的偏角最大;混合段参数应使射流附着于混合段壁面;第二喉道应使射流向流场中均匀传递动量,其过小或过大均会减小射流偏角并导致射流向流场中传递动量不均匀;扩张段扩张角应增大至刚好不阻挡射流偏转,过大会使扩张段内射流发生不对称附着现象;增大出口高度可以增大射流偏移量,但其过大会延长射流在扩张段两侧的停滞时间。不同激励器的分离控制效果对比表明,采用自主设计激励器时的偏转襟翼减阻量是采用典型激励器时的3.8倍。

组合式叶片附加件对潮流能水轮机叶片水动力学特性的影响研究

为抑制潮流能水轮机叶片根部的边界层流动分离,提高水轮机叶片的发电效率,将格尼襟翼(GF)和涡流发生器(VGs)附加件组合引入到潮流能水轮机叶片设计领域。以NACA63418翼型为对象,分别建立原始叶片、带GF叶片、带VGs叶片、带GF和VGs附加件组合的叶片模型。通过试验和CFD数值模拟相结合的方法,研究单独加装GF和VGs对水轮机三维扭曲叶片的影响效果和作用机理,进而开展GF和VGs组合式叶片附加件对水轮机叶片水动力学特性的影响规律的研究。结果表明:1)对直径为700 mm的原始水轮机叶片,其叶片吸力侧根部容易发生流动分离和径向流动;2)单独安装GF既能改善水轮机叶片根部翼型尾缘处的径向流动,又能增大叶片翼型的后半部分上下表面的压差,且当GF高度为2.0%C时,最佳叶尖速比(λ=5)下的叶片获能系数可提高约1.7%;3)单独安装VGs可通过抑制叶片根部的流动分离,使处在最佳叶尖速比下的叶片获能系数提高约1.0%;4)安装GF和VGs组合式叶片附加件可将单独加装二者的优势充分融合,既能有效抑制叶片根部的流动分离,又能全面增大叶片翼型上下表面的压差,叶片获能系数可提高约1.7%~4.8%,其中最佳叶尖速比下的叶片获能系数可提高约2.5%。

影响振荡射流分离控制效果的关键因素

为找出影响振荡射流对流场分离控制效果的关键因素,采用典型振荡射流激励器对偏转襟翼流场施加控制,通过数值模拟分析施加控制后的流场特点,总结了射流停滞的原因和影响;并对比不同扩张段、脉冲式和扫掠式振荡射流的控制效果,总结了射流扫掠范围对控制效果的影响。结果表明:射流向流场中传递动量的均匀程度和扫掠范围是影响控制效果的关键因素。射流向流场中传递动量越均匀,扫掠范围越大,则控制效果越好。激励器喉道过小会抑制射流偏转,使射流在出口两侧停滞,导致射流向流场中传递动量不均匀,因此偏转襟翼两侧的控制效果好于中部;增大扩张段会增大射流扫掠范围从而改善控制效果;脉冲式激励器内的尖劈会阻挡射流扫掠至其后方,导致射流扫掠范围小,偏转襟翼中部控制效果差。

仿生扑翼飞行器姿态稳定控制设计与实验

针对扑翼飞行器在飞行过程中姿态调整控制问题,提出了一种快速响应的自动姿态稳定控制方法。利用牛顿定律和动量矩定理建立扑翼飞行器数学模型,结合扑翼飞行器姿态变化工作原理,研究飞行过程中姿态调整控制方案策略。采用串级PID控制算法设计姿态调整内环和外环控制器,以扑翼飞行器欧拉角为输出,对扑翼飞行器姿态调整过程进行了仿真计算以及外场飞行实验。通过对扑翼飞行器姿态角的响应仿真分析及外场飞行实验数据分析,验证了扑翼飞行器数学模型的准确性及姿态控制器的有效性。结果表明:在阶跃信号输入下,姿态角能快速响应并快速趋于稳态,外场飞行中扑翼飞行器俯仰角保持15°,飞行加速度保持1 m/s^(2),可以较好地自动保持姿态稳定。

具有不确定性的扑翼微型飞行器抗干扰控制

研究了具有内部不确定性和外部干扰的扑翼微型飞行器的姿态和位置跟踪控制问题。利用神经网络对扑翼微型飞行器数学模型中复杂非线性和不确定性进行逼近估计,同时对于外部扰动,采用自适应技术来处理干扰对系统的影响。基于反步递推框架,引入一阶滤波器,设计了动态表面控制器,克服了传统反步递推设计中“微分爆炸”的局限性。进一步,利用Lyapunov稳定理论证明了扑翼飞行器姿态和位置闭环系统的稳定性和所有状态变量的半全局一致最终有界性。结果表明,所提控制器不仅能够使稳态误差更好地收敛,而且还提高了收敛速度。仿真结果验证了所提控制方法能够有效地处理不确定性和外部干扰,且能够很好地跟踪期望轨迹。

流动控制组合对潮流能水轮机翼型水动力学的特性影响研究

为全面提升潮流能水轮机叶片的水动力学性能,将格尼襟翼(GF)和涡流发生器(VGs)的附加件组合引入到潮流能水轮机领域,研究附加件组合对改善水轮机叶片水动力性能的作用机理。以NACA4418翼型为研究对象,分别建立加装格尼襟翼、涡流发生器和二者流动控制组合的水轮机翼型三维模型,应用数值模拟方法研究流动控制组合对水轮机叶片水动力性能的影响机理。结果表明:安装GF可有效提高翼型段的升力系数,但会降低翼型的失速角;安装VGs可抑制翼型段吸力面的流动分离、增大翼型段的失速角,但攻角越小水动力学性能改善效果越不明显;GF和VGs的流动控制组合则可将二者优势充分结合,在全面提高翼型段升力系数的同时,还可抑制翼型表面的流动分离、增大翼型的失速角,从而获得最佳的流动控制效果。

电动车空调内外循环风门模糊控制研究

电动车空调内外循环风门控制对乘客舱防雾、空气清新度、空调能耗等多个方面有重要影响,但是内外循环风门控制难以建立精确的数学模型。文章采用模糊控制方法,将起雾风险、CO_(2)浓度、空调负荷作为输入,将内外循环风门开度作为输出,采用高斯型函数,利用MATLAB Simulink软件建立模糊控制器,并基于Simscape软件搭建汽车空调仿真模型。经过仿真验证,内外循环风门模糊控制方法可以在乘客舱防雾、空气清新度、空调能耗等多方面都有很好的控制效果,相比固定比例外循环控制,模糊控制综合评分最高,综合性能表现最好。

控制性阶梯式大骨瓣减压术在重型颅脑损伤中的疗效观察

目的:探讨控制性阶梯式大骨瓣减压术在重型颅脑损伤中的疗效。方法:选择2022年1月—2023年8月抚州市第一人民医院收治的80例重型颅脑损伤患者作为研究对象,采取随机数字表法分两组,各40例。参照组开展标准大骨瓣减压术治疗,研究组开展控制性阶梯式大骨瓣减压术治疗。比较两组围手术期指标、意识状况、预后情况及并发症发生情况。结果:研究组手术时间及住院时间均短于参照组,术后清醒时间早于参照组(P<0.05)。术后,研究组格拉斯哥昏迷量表(GCS)、格拉斯哥预后量表(GOS)评分均高于参照组(P<0.05)。研究组并发症发生率低于参照组(P<0.05)。结论:重型颅脑损伤患者实施控制性阶梯式大骨瓣减压术治疗,可取得更为理想的治疗效果,可提高手术效率和促进康复进程,改善重型颅脑损伤患者术后意识状况及预后情况,减少相关并发症发生。

基于人工智能的排水管网截污拍门控制系统研究及应用

针对合流制排水管网截污拍门功能、安装和使用等问题导致的溢流污染,开展截污拍门控制系统研究和应用。设计气动拍门截污控制技术,实现雨天排涝和旱天截污功能;设计低成本一次性电池续航供电技术,实现极限微功耗的一次性电池续航供电,消除拍门安装条件限制;研究双模糊逻辑模型控制技术,精准检测并控制障碍物阻挡拍门关闭导致的缝隙污水泄漏。通过广州市猎德涌现场安装拍门应用测试,结果表明:旱天拍门截污功能控制精度>99%,一次性电池续航供电3.7年以上,拍门缝隙污水泄漏检测与控制综合精度>99%,进一步减少合流制排水管网的溢流污染。

带控制舵飞行器机动特性研究

研究带控制舵双锥外形再入飞行器的机动特性。文章首先利用“部件叠加法”,通过对干扰因子和等效攻角等概念的引入,发展了一套可以计算该类飞行器纵横向气动力的工程计算方法。其次,文章通过大量计算,分析研究了该类飞行器的配平特性。最后,利用气动力与六自由度弹道耦合方法,研究分析了此类飞行器实现射面拉起/下压机动飞行及空间锥形机动的舵面控制规律。

大迎角下两段式翼型后翼作俯仰拍动的实验研究

通过氢气泡流动显示和PIV流场测量研究了大迎角下两段式翼型后翼作俯仰拍动时的流场结构及其演化。实验在北航1.0m×1.2m水槽中进行,基于翼型弦长的实验雷诺数为9000。实验结果显示:在大迎角情况下,当翼型静止时,前缘产生的分离涡会远离背风面向下游脱落,背风面上方会形成大范围的分离区;而当翼型前翼保持不动,后翼进行简谐拍动时,前缘产生的分离涡将靠近背风面向下游运动,背风面上方原有的大范围分离区将显著缩小甚至消失,这意味着可能增升和改善升阻比。此外,本文对后翼拍动的频率和振幅的影响也进行了较为详细的讨论。