Aerodynamic load control on a dynamically pitching wind turbine airfoil using leading-edge protuberance method

The aerodynamic loads of wind turbine blades are substantially affected by dynamic stall induced by the variations of the angle of attack of local airfoil sections.The purpose of the present study is to explore the effect of leading-edge protuberances on the fluctuation of the aerodynamic performances for wind turbine airfoil during dynamic stall.An experimental investigation is carried out by a direct force measurement technique employing force balance at a Reynolds number Re=2×105.The phase-averaged and instantaneous aerodynamic loads of the pitching airfoil,including the baseline and the wavy airfoil,are presented and analyzed.The phase-averaged results indicate that the effects of dynamic stall for the wavy airfoil can be delayed or minimized compared to the baseline airfoil,and the negative damping area of the wavy airfoil is significant decreased in full-stall condition.These effects of leading-edge protuberances are more notable at a higher reduced frequency.For the instantaneous aerodynamic loads of the wavy airfoil,there is an observable reduction in fluctuations compared with baseline case.Furthermore,spectral analysis is applied to quantitatively undercover the nonstationary features of the instantaneous aerodynamic loads.It is found that the leading edge protuberances can reduce the harmonics of the aerodynamic force signal,and enhance the stability of the aerodynamic loads under different reduced frequencies.In conclusion,leading-edge protuberances are found effective to reduce the fluctuation characteristics of the aerodynamic loads during the dynamic stall process,and help to improve the stability and prolong the service life of the wind turbine blades.

Effect of leading-edge tubercles on the flow over low-aspect-ratio wings at low Reynolds number

Two-dimensional time-resolved particle image velocimetry(TR-PIV)and stereographic particle image velocimetry(SPIV)techniques were used to investigate the effect of leading-edge tubercles on the flow over low-aspect-ratio wing models.The angle of attack is fixed at 10°,and the Reynolds number based on chord length is 5.8×10^(3).It is shown that the leading-edge tubercles can effectively mitigate flow separation in the model and also reduce the contribution of wake vortex to the fluctuating energy of flow.Counter-rotating vortex pairs(CVPs)initiated from the peak of leading-edge tubercles can promote nearby momentum exchange,enhance mixing of the flow and increase the energy contained in the boundary layer,which results in resisting the larger adverse pressure gradient.Therefore,it is concluded that CVPs play an important role in mitigating the flow separation for wings with leading-edge tubercles.

Influence of Dimensions of UHMW-PE Protuberances on Sliding Resistance and Normal Adhesion of Bangkok Clay Soil to Biomimetic Plates

A number of investigations into application of polymers for macro-morphological modification of tool surface have been carried out. These researches, with extensive stress on convex or domed protuberations as one of the widely used construction units, have tried to harness benefits from using polymers in agriculture. Ultra high molecular weight polyethylene （UHMW-PE） has proved an emerging polymer in its application to reduce soil adhesion. This research was conducted to study the effect of shape （flat, semi-spherical, semi-oblate, semi short-prolate and semi long-prolate） and dimensions （base diameter and dome height） on sliding resistance and normal adhesion of biomimetic plates. To incorporate both shape and size, a dimensionless ratio of height to diameter （HDR） was introduced to characterize the effect of construction unit＇s physique. Experiments were conducted in Bangkok clay soil with dry （ 19.8% d.b.）, sticky （36.9% d.b.） and flooded （60.1% d.b.） soil conditions respectively. Soil at sticky limit exhibited the highest sliding resistance （77.8 N） and normal adhesion （3 kPa to 7 kPa）, whereas these values were 61.7 N and 〈0.2 kPa in dry, and 53.7 N and 0.5 kPa to 1.5 kPa in flooded soil conditions. Protuberances with HDR ≤ 0.5 lowered sliding resistance by 10% - 30% and the same reduced normal adhesion by 10% - 60%. The amount of reduction in both sliding resistance and normal adhesion was higher in flooded soil. Lighter normal loads obviously produced lesser resistance and adhesion.

Role of animal pole protuberance and microtubules during meiosis in sea cucumber Apostichopus japonicus oocytes

Fully grown oocytes of Apostichopus japonicus have a cytoplasmic protuberance where the oocyte attaches to the follicle. The protuberance and the oolamina located on the opposite side of the oocyte indicate the animal-vegetal axis. Two pre-meiotic centrosomes are anchored to the protuberance by microtubules between centrosomes and protuberance. After meiosis reinitiation induced by DTT solution, the germinal vesicle (GV) migrates towards the protuberance. The GV breaks down after it migrates to the oocyte membrane on the protuberance side. The protuberance then contracts back into the oocyte and the first polar body extrudes from the site of the former protuberance. The second polar body forms beneath the first. Thus the oocyte protuberance indicates the presumptive animal pole well before maturation of the oocyte.

Leading-edge receptivity of boundary layer to three-dimensional free-stream turbulence

The laminar-turbulent transition has always been a hot topic of fluid mechanics. Receptivity is the initial stage and plays a crucial role in the entire transition process. The previous studies of receptivity focus on external disturbances such as sound waves and vortices in the free stream, whereas those on the leading-edge receptivity to the three-dimensional free-stream turbulence (FST), which is more general in the nature, are rarely reported. In consideration of this, this work is devoted to investigating the receptivity process of three-dimensional Tollmien-Schlichting (T-S) wave packets excited by the three-dimensional FST in a flat-plate boundary layer numerically. The relations between the leading-edge receptivity and the turbulence intensity are established, and the influence of the FST directions on the propagation directions and group velocities of the excited T-S wave packets is studied. Moreover, the leading-edge receptivity to the anisotropic FST is also studied. This parametric investigation can contribute to the prediction of laminar-turbulent transition.

Submucosal protuberance caused by a fish bone in the absence of preoperative positive signs:A case report

BACKGROUND Submucosal protuberance caused by fish bone insertion into the digestive tract has rarely been reported.These cases usually include patients with clear signs such as a history of fish intake,pain,and dysphagia,as well as positive findings on endoscopy and imaging.Here,we report a case of a fish bone hidden in the submucosal protuberance of the gastric antrum during endoscopic submucosal dissection without preoperative obvious positive signs.CASE SUMMARY A 58-year-old woman presented with epigastric pain for the past 20 d and a submucosal protuberance.Abdominal computed tomography and endoscopic ultrasonography did not indicate the presence of a fish bone.We assumed the cause to be an ordinary submucosal eminence and performed an endoscopic submucosal dissection to confirm its essence.During the operation,a fish bone approximately 20 mm in length was found incidentally.CONCLUSION Our report could potentially prevent the oversight of embedded fish bones and associated adverse effects in patients with similar presentation.

超声引导下粗针活检术联合CD34免疫组化标记在隆突性皮肤纤维肉瘤诊断中的应用

目的探讨超声引导下粗针活检术联合CD34在隆突性皮肤纤维肉瘤的诊断中的应用价值。方法回顾性分析于术前经超声引导下粗针活检术及CD34免疫组化标记诊断为隆突性皮肤纤维肉瘤的32例患者的病理资料与超声检查结果,并将其与手术后病理结果进行对比分析。结果32例患者中,30例患者于术前经超声引导下粗针活检术及CD34免疫组化标记诊断为隆突性皮肤纤维肉瘤,1例患者诊断为“倾向于隆突性皮肤纤维肉瘤”,另1例考虑“间叶源性肿瘤,不能除外纤维肉瘤”。术后病理结果提示31例患者为隆突性皮肤纤维肉瘤,1例患者为纤维肉瘤型皮肤纤维肉瘤。超声引导下粗针活检术联合CD34免疫组化标记诊断隆突性皮肤纤维肉瘤与术后病理结果的符合率为93.75%(30/31)。结论超声引导下粗针活检术联合CD34免疫组化标记诊断隆突性皮肤纤维肉瘤的准确性高,具有较大的临床应用价值。

胃底腺型胃癌1例并文献复习

目的探讨胃底腺型胃癌(gastric adenocarcinoma of fundic gland type,GA-FG)的临床特征、诊断及鉴别诊断。方法回顾性分析1例GA-FG患者的诊疗经过,并复习相关文献。结果患者为54岁女性,因胃镜检查时发现胃体上部SMT样褪色调病变。该病变表面黏膜光滑,可见扩张的树枝样血管改变;放大内镜技术联合窄带成像技术(ME+NBI)示:病变周边黏膜呈典型蜂窝状结果,病变呈茶褐色,表面微腺管可见融合,腺管开口大小不一,白区不规则,表面微血管不规则;超声胃镜示:可见胃体黏膜层病变,呈中等偏低回声,起源于黏膜层,与黏膜肌层分界不清,黏膜下层完整,大小约0.8 cm×0.5 cm。内镜下切除后病理:胃底腺型腺癌,镜下面积约:0.3 cm×0.3 cm,浸润至黏膜下层(漫润深度约220μm);脉管浸润(-),神经侵犯(-);水平切缘及垂直切缘未见癌细胞;周围黏膜组织慢性炎。免疫组化:MUC6(+);MUC5AC(-);P53无义突变(-);Desmin(示黏膜肌不完整);Syn个别细胞(+);CgA个别细胞(+);CD31及D2-40(脉管内未见癌栓);Ki-67阳性率约10%。结论GA-FG是一种新的组织学类型胃癌,具有独特的临床内镜及病理特征,预后良好,但需要长期随访。

正畸治疗患者前牙牙槽骨唇侧骨性凸起研究进展

正畸治疗过程中,患者前牙牙槽骨唇侧有时会出现不规则、大小不一的结节性骨性凸起,这与牙槽骨内外表面的差异性骨改建有着密切关系。牙槽骨唇侧骨性凸起不仅会对正畸治疗的美学效果产生负面影响,还可能增加牙周风险。目前认为牙槽骨唇侧骨性凸起形成可能与患者性别、年龄、牙齿移动速度、前牙内收距离有关。唇侧骨性凸起存在一定自限性,若出现不能自行消退的唇侧骨性凸起需通过牙槽骨修整术进行治疗。本文通过文献回顾,系统性介绍正畸过程中前牙牙槽骨唇侧骨性凸起的发生假说、形成的影响因素、潜在生物力学机制及其对应治疗策略,有助于深入理解正畸治疗中牙槽骨改建的规律和相关机制,并为临床提供预防和治疗的理论支持。

Design optimization and testing of a morphing leading-edge with a variable-thickness compliant skin and a closed-chain mechanism

Climate warming and the increased demand in air travels motivate the aviation industry to urgently produce technological innovations.One of the most promising innovations is based on the smoothly continuous morphing leading-edge concept.This study proposes a two-step process for the design of a morphing leading-edge,including the optimization of the outer variable-thickness composite compliant skin and the optimization of the inner kinematic mechanism.For the compliant skin design,an optimization of the variable thickness composite skin is proposed based on a laminate continuity model,with laminate continuity constraint and other manufacturing constraints.The laminate continuity model utilizes a guiding sequence and a ply-drop sequence to describe the overall stacking sequence of plies in different thickness regions of the complaint skin.For the inner kinematic mechanism design,a coupled four-bar linkage system is proposed and optimized to produce specific trajectories at the actuation points on the stringer hats of the compliant skin,which ensures that the compliant skin can be deflected into the aerodynamically optimal profile.Finally,a morphing leading-edge is manufactured and tested.Experimental results are compared with numerical predictions,confirming the feasibility of the morphing leading-edge concept and the overall proposed design approach.

Aerodynamic characteristics of a pitching airfoil with leading-edge morphing

This paper focuses on the effect of the phase offset of Leading-Edge(LE)morphing on the aerodynamic characteristics of a pitching NACA0012 airfoil.Assuming an unstretched camber and using polynomial interpolation,an explicit expression for LE nonlinear morphing is proposed and implemented for the large pitching motion of the airfoil.Flow field results and aerodynamic forces are obtained by solving the unsteady Reynolds-averaged Navier-Stokes equations for both the airfoil’s pitching motion and LE morphing.Furthermore,the index of instantaneous aerodynamic power is used to quantify the work done by the airflow in a dynamic process.According to the instantaneous aerodynamic power and energy map,which denotes the energy transfer between the airfoil’s oscillation and flow field,the airfoil is subject to stall flutter.The results show that LE morphing with an optimal phase offset of 315°reduces the energy extraction from the flow field,suppressing the stall flutter instability.This optimal phase offset is effective at different pitching axis positions of the airfoil.The results signify that LE morphing can suppress stall flutter by advancing the occurrence of the first LE vortex and increasing the nose-down moment during the upstroke period.

Investigation of non-uniform leading-edge tubercles in compressor cascade:Based on multi-objective optimization and data mining

Corner stall receives noticeable attention in the aeroengine field as an important phenomenon in highly-load compressors.Non-uniform leading-edge tubercles,as an effective method to delay stall,are introduced into the compressor.In this paper,the shape of leading-edge tubercles was controlled by a third-order Fourier function.To judge corner stall,a more precise stall indicator for compressor cascade with flow control methods was defined.Besides,the total kinetic energy of the secondary flow at large incidence was adopted as a parameter for stall evaluation to save computing resources.The results of multiobjective optimization reveal that the loss coefficient exhibited negligible variation at design incidence,while the total kinetic energy of secondary flow showed a significant reduction at large incidence,resulting in a substantial increase in stall incidence.In the optimal profiling cases,the stall incidencewas delayed from 7.9°to 11.6°.The major purpose of the research is to provide proper design guidelines for nonuniformleading-edge tubercles and uncover the flow controlmechanisms of leading-edge profiling.Hence,the geometric features that meet different optimization objectives were extracted through geometric analysis near the Pareto Front and through Self-OrganizingMap(SOM)dataminingmethods in the optimization database.Besides,flow field analysis reveals the flow control mechanism of leading-edge tubercles.The convex-concave-convex structure at the 0%-70%blade height region can form two branches of leading-edge vortex pairs that are opposite in the rotation direction to the passage vortex.The two branches of leading-edge vortex pairs mixed with the leading-edge separation vortex to form two stronger mixed vortices,which can effectively suppress the development of passage vortex and delay stall incidence.

海域花岗岩发育区地震反射精细地质构造调查

广东近海海域位于太平洋板块与大陆板块交界处,地质活动活跃,地质结构复杂。在花岗岩分布区,基岩不均匀风化形成风化基岩凹槽、隆起和孤石等,基岩面起伏较大。单一钻探方法难以反映隧道沿线地质结构的连续变化。本文采用高频小炮距水域地震反射方法,查明隧道沿线详细地质条件,总结各种地质体的地震反射特征,研究断裂走向及活动性。在小炮间距地震剖面中,基岩面表现为反射同相轴起伏变化,基岩隆起对应同相轴上隆,基岩凹槽对应同相轴下凹;断裂表现为同相轴缺失、突变、错断;抛石发育区与孤石(群)形成绕射波。本文利用多条地震反射剖面构建三维地质模型,全面展示隧道沿线复杂地质结构,划定强风化花岗岩区。对比研究发现地震反射解释结论与钻探揭示情况吻合较好,为隧道工程设计和施工提供了可靠的地质资料。

Selective endoscopic ligation for treatment of upper gastrointestinal protuberant lesions

This study explored the clinical value of endoscopic ligation for the treatment of upper gastrointestinal(GI)protuberant lesions in children.According to the appearance and size of lesions,we used different ligation techniques for the treatment of the lesions.Endoscopic ultrasonography was used for preliminary characterization of the lesions.One case diagnosed with PeutzJeghers syndrome was successfully treated by a detachable snare.Two cases with semi-pedunculated or broad-base lesions originating from the submucosal layer of the upper GI were treated with endoscopic variceal ligation;endoscopic examination showed that one case had complete healing 11 wk after ligation,while an ulcer scar was observed at the ligation site after 6 wk in the other case.All lesions were successfully ligated at the first attempt.No significant complications occurred either during or after the procedure.Selective endoscopic ligation of upper GI lesions is an effective and safe treatment for upper GI protuberant lesions in children.

基于凹凸前缘方法的风力机翼型气动噪声研究

该文采用实验测量和数值计算相结合的方法,以DU93-W-210翼型为研究对象,研究仿生凹凸前缘结构对其降噪效果的影响。运用远场麦克风阵列获得光滑前缘翼型和凹凸前缘翼型的气动噪声,并通过数值计算得到翼型表面流场结果。通过对实验和数值计算结果的分析发现:凹凸前缘方法能有效抑制边界层分离,控制翼型吸力面涡量的团状分布,减小翼型表面的压力脉动,分解大尺度高强度脱落涡为小尺度低强度周期性脱落涡,使得仿生凹凸前缘翼型有明显的降低气动噪声的作用;具有凹凸前缘的幅值为0.24c(c为平均弦长)、波长为0.11c的仿生翼型降噪效果更为突出。

基于多排螺旋CT容积重建图像评价枕外隆凸分型与性别、年龄差异

目的分析多排螺旋CT容积重建(VR)图像评价枕外隆凸分型的一致性,探究枕外隆凸分型与性别、年龄之间的关系。资料与方法回顾性收集2016年2月—2021年5月北京中医药大学东方医院共604例(男、女各302例)患者头部多层螺旋CT资料,VR后处理图像评价枕外隆凸影像学类型,比较不同枕外隆凸分型间的性别、年龄差异。结果基于VR后处理图像评价枕外隆凸分型一致性较高(Kappa=0.847,P<0.001)。不同枕外隆凸分型间的性别构成差异有统计学意义(χ^(2)=92.949,P<0.001)。枕外隆凸I型中,女性例数约为男性的2.42倍(160例比66例);枕外隆凸III型中,男性例数约为女性的4.40倍(110例比25例)。不同年龄组间枕外隆凸分型差异无统计学意义(χ^(2)=3.847,P=0.697)。结论多排螺旋CTVR图像可以评价枕外隆凸分型,枕外隆凸分型与性别存在显著相关。

Influences of Leading-Edge Tubercle Amplitude on Airfoil Flow Field

The influences of leading-edge tubercle amplitude on airfoil flow field have been analyzed at high angle of attack.The accuracy of a large eddy simulation(LES)research is validated through quantitative comparisons with corresponding experimental results.Then,a proper orthogonal decomposition(POD)analysis has been carried out based on the unsteady flow field and the fluid mechanisms of corresponding POD modes have been identified.Consequently,the influences of leading-edge tubercle amplitude have been uncovered.Since the streamwise vorticity is larger than that of small amplitude cases,the momentum transfer process at peaks is more obvious for large amplitude,leading to delayed flow separation.Both amplitude and wavelength play important roles in the generation of laminar separation bubble(LSB)at troughs.Moreover,the Karman vortex shedding process takes place at specific trough sections as pairs of periodic spatial structures exist in the dominant POD modes.The destruction of Karman vortex shedding process is strengthened along with the increase of amplitude.

矿井巷道支护中锚固长度的影响作用研究

锚杆支护是煤矿开采中常用的支护方式,对于巷道围岩的变形控制具有重要的作用。在锚杆支护的过程中,采用锚固剂进行锚固的长度不同,对围岩的支护效果具有重要的影响作用。采用有限元模拟的形式对不同锚固长度时围岩的水平位移、地表沉降及基坑的隆起量进行分析,从而为锚固段长度的设计取值提供参考,以提高锚杆支护的效果,保证煤矿的开采支护安全。

热轧辊型技术对冷轧钢卷局部突起缺陷的抑制

为解决由热轧带钢不良断面形状遗传到冷轧带钢而引起的钢卷局部突起缺陷,在分析猫耳形磨损辊型对热轧带钢断面形状不良影响的基础上,提出了以抑制热轧带钢边部增厚和局部高点相对高度为目的的工作辊余弦辊型。模拟计算和实验表明,余弦辊型明显改善了带钢断面形状、降低了边部增厚和局部高点的相对高度,解决了冷轧钢卷局部突起缺陷问题,并为现场解决类似问题提供了新思路。

284例内镜超声检查与治疗分析

目的探讨内镜超声诊断与治疗价值。方法284例黏膜隆起性病变和胰腺疾病采用日本Pentax EG-3630u型超声内镜,探头频率5.0～7.5MHz,纵轴电子线阵扇扫。结果食管63例(平滑肌瘤30例,炎症6例,息肉4例,癌症6例,食管囊肿1例,外压9例),胃169例(胃炎67例、间质瘤40例、平滑肌瘤3例、癌症14例、息肉9例、脂肪瘤6例、胃溃疡2例、胃底静脉瘤2例、异位胰1例、外压25例),十二指肠16例(息肉6例,炎症1例,间质瘤3例,异位胰2例,外压1例),胰腺36例(肿瘤11例,炎症9例,假性囊肿4例,囊腺瘤1例)。治疗息肉电切治疗14例,良性肿瘤套扎治疗13例。胰腺穿刺注射治疗5例,腹腔神经丛注射治疗2例,疼痛可暂时缓解。手术病理与内镜超声诊断符合率为96.3%。结论该组黏膜隆起性病变患者中食管平滑肌瘤和胃间质瘤多见,超声图像和发生部位有助诊断。癌症、异位胰腺、脂肪瘤或脂肪肉瘤、静脉瘤、腔外压迹、扁平息肉、炎性增生等内镜超声表现特点清晰,易于诊断处理。胰腺疾病内镜超声可提高早期诊治率。