Aerodynamic analysis of cambered blade H-Darrieus rotor in low wind velocity using CFD

Anal Ranjan Sengupta,Agnimitra Biswas,Rajat Gupta 한국풍공학회 2021 Wind and Structures, An International Journal (WAS Vol.33 No.6

This present paper leads to investigation of blade-fluid interactions of cambered blade H-Darrieus rotor having EN0005 airfoil blades using comprehensive Computational Fluid Dynamics (CFD) analysis to understand its performance in low wind streams. For several blade azimuthal angle positions, the effects of three different low wind speeds are studied regarding their influence on the blade-fluid interactions of the EN0005 blade rotor. In the prevailing studies by various researchers, such CFD analysis of H-Darrieus rotors are very less, hence it is needed to improve their steady-state performance in low wind velocities. Such a study is also important to obtain important performance insights of such thin cambered blade rotor in its complete rotational cycle. It has been seen that the vortex generated at the suction side of the EN0005 blade rolls back to its leading edge due to the camber of the blade and thus a peak velocity occurs near to the nose position of this blade at its leading edge, which leads to peak performance of this rotor. Again, in the returning phase of the blade, a secondary recirculating vortex is generated that acts on the pressure side of EN0005 blade rotor that increases the performance of this cambered EN0005 blade rotor in its downstream position as well. Here, the aerodynamic performances have been compared considering Standard k-ε and SST k-ω models to check the better suited turbulence model for the cambered EN0005 blade H-Darrieus rotor in low tip speed ratios.

임실 하가 구석기유적의 돌날제작기법 연구

정보현 한국구석기학회 2022 한국구석기학보 Vol.- No.46

The blade is a representative artifact of the upper Paleolithic of Korea. The study of the manufacturing techniques of the blade and restoration of it play an important role in understanding of survival skills of upper Paleolithic human. This paper researches into the technology and process of the blade production through the blade production technology we learned from ‘Refitting artifact’ of Imsil Haga site, and analogizes the kind of the hammer which they used for the blade production in comparison with the existing research result of experimental archaeology on the blade production. Restoring the blade production process as a result of the analysis of ‘refitting artifacts’, 1. Shaping, removed cortical face and unnecessary parts of the raw material are made into sizes and shapes suitable for blade production using stone hammer direct percussion (refitting artifacts 1, 3). 2. creation of a striking platform, 3. blade debitage using the Antler hammer direct percussion. (refitting artifacts 1, 3) 4. Change the striking platform according to the production process, and blade debitage by making the most of the stones several times (refitting artifacts 1, 2). 5. When knapping accidents (step, hinge, and flange) appeared on the blade core, or when the size of the core became smaller and it became difficult to make a blade of the desired size, the blade was discarded without production more blades. The reason for the abandonment of the blade was 1. If it is no longer possible to make the blade due to the Knapping accidents (step, plunging, hinged), 2. If the size of the blade cannot be made, The ‘Refitting artifact 1’ includes two tools (tanged point), which analyzed the length and production space of the tool that the tool maker wanted. First of all, considering that the length of the blade identified in ‘Refitting artifact 1’ is about 40 to 88mm, and the tanged point is about 51, 54mm, it is thought that the stone maker made a blade with a length of about 50 to 70mm or made a tool. The excavation location of tanged point is about 2m away from the central part of the bladecore, and it is thought that the tool was made by moving the blade after manufacturing it. 돌날은 우리나라 후기구석기를 대표하는 유물로 당시 사람들의 생활을 추정하는 데 중요한 역할을 한다. 이러한 돌날의 제작 연구를 통해 돌감의 획득, 제작 준비, 제작, 제작된 돌날을 이용한 행위 등 다양한 모습에 대한 복원이 가능하다. 논문에서는 임실 하가유적의 붙는 유물(3개의 돌날몸돌에 붙는 유물 47점)의 분석을 통해 제작기법과 과정을 연구하고 기존에 연구된 실험고고학 자료와의 비교를 통해 사용한 망치의 종류를 유추했다. 붙는 유물의 분석 결과로 돌날제작과정을 복원해보면 1. 몸체다듬기를 통해 자갈면과 불필요한 부분을 돌망치 직접떼기를 사용해 돌날 제작에 적합한 크기와 모양으로 만든다(붙는 유물 1, 3). 2. 다듬어진 몸체에 평평한 때림면을 만들고, 3. 뿔망치 직접떼기를 사용해 돌날을 제작한다(붙는 유물 1, 3). 4. 떼기 과정에 맞춰 때림면을 바꾸고, 다시 만들어가며 여러 차례에 걸쳐 돌감을 최대한 활용해 돌날을 제작한다(붙는 유물 1, 2). 5. 돌날몸돌에 의도치 않은 떼기(스텝, 힌지, 플런징)가 나타나거나, 몸돌의 크기가 작아져 원하는 크기의 돌날을 제작하기 어려워지면 돌날을 더 제작하지 않고 버렸다. 돌날몸돌이 버려진 이유는 1. 의도치 않은 떼기(스텝, 플런징, 힌지)로 인해 돌날제작이 불가능할 경우, 2. 돌날몸돌의 크기가 원하는 돌날을 제작할 수 없는 경우로 나타났다. ‘붙는 유물 1’에는 2점의 도구(슴베찌르개)가 포함되는데, 이를 통해 석기제작자가 원한 도구의 길이와 제작공간에 대해 분석했다. 먼저 ‘붙는 유물 1’에서 확인되는 돌날의 길이는 약 40~88㎜이고, 슴베찌르개가 약 51, 54㎜인 것으로 보아 석기제작자는 길이가 약 50~70㎜인 돌날을 제작해 사용하거나 도구를 만든 것으로 생각된다. 슴베찌르개의 출토 위치는 돌날몸돌을 중심으로 한 집중부와 약 2m 정도 떨어져 있는데, 돌날을 제작한 후 이동하여 도구를 제작한 것으로 생각된다. 종합하면 하가유적에서는 유적 앞 섬진강 변에서 자갈돌을 가져와 돌망치 직접떼기를 사용해 불필요한 부분을 제거하고 때림면을 평평하게 만들어 돌날을 제작하기 적합한 몸체를 만들었다. 이후 뿔망치 직접떼기를 사용해 돌날을 제작했는데, 길이가 약 50~70㎜인 돌날을 제작했다. 몸체를 최대한 활용하기 위해 때림면을 다시 만들거나 바꿔가며 다시 돌날을 제작했다. 원하는 크기의 돌날을 제작하기 어렵거나 의도치 않은 떼기가 떼어질 때 더는 돌날을 제작하지 않고 몸돌을 버렸다.

A Study on Flow Characteristics and Cooling Performance for Different Turbine Blade Shapes

박찬우(Chan Woo Park),이동렬(Dong-Ryul Lee) Korean Society for Precision Engineering 2019 한국정밀공학회지 Vol.36 No.11

The purpose of this study was to investigate the flow characteristics and cooling performance for the heavy turbine blade with different shapes. Research was focused on the numerical study on forced convective heat transfer coefficients for three different blades with base, tip, and hole. Thus, selected local locations for various temperature distributions were shown in the flow domain. Final temperature on the local surface of blades was compared with three different blades. According to the results of velocity and temperature distributions in the fluid domain, the blade with holes had the best convective cooling performance with higher 13-16% average heat transfer coefficient than the other two blades. Apparent vortex at the tip of tip and hole blade caused the stable temperature drop. According to the calculations of local convective heat transfer coefficient between blade surface and atmosphere in the blade, approximately 18% of heat transfer coefficient at hole was higher than the base blade and 7% at hole blade was higher than the base blade. Lowest cooling performance existed at the center position of all three blades.

Dynamic behavior of smart material embedded wind turbine blade under actuated condition

Yuvaraja Mani,Jagadeesh Veeraragu,Sangameshwar S.,Rudramoorthy Rangaswamy 한국풍공학회 2020 Wind and Structures, An International Journal (WAS Vol.30 No.2

Vibrations of a wind turbine blade have a negative impact on its performance and result in failure of the blade, therefore an approach to effectively control vibration in turbine blades are sought by wind industry. The small domestic horizontal axis wind turbine blades induce flap wise (out-of-plane) vibration, due to varying wind speeds. These flap wise vibrations are transferred to the structure, which even causes catastrophic failure of the system. Shape memory alloys which possess physical property of variable stiffness across different phases are embedded into the composite blades for active vibration control. Previously Shape memory alloys have been used as actuators to change their angles and orientations in fighter jet blades but not used for active vibration control for wind turbine blades. In this work a GFRP blade embedded with Shape Memory Alloy (SMA) and tested for its vibrational and material damping characteristics, under martensitic and austenite conditions. The embedment portrays 47% reduction in displacement of blade, with respect to the conventional blade. An analytical model for the actuated smart blade is also proposed, which validates the harmonic response of the smart blade.

Fatigue failure of a composite wind turbine blade at its root end

Lee, Hak Gu,Kang, Min Gyu,Park, Jisang Elsevier 2015 Composite structures Vol.133 No.-

<P><B>Abstract</B></P> <P>As blade failures at wind farms have increased, the structural safety of composite wind turbine blades is ever more important. The recent implementation of considerably larger blades has made the problem even more crucial. One of the critical failure modes is the blade root failure, which can result in the blade being pulled out from its wind turbine during operation. In this study, we experienced delamination failure at the blade root during fatigue testing of a 3MW full-scale wind turbine blade according to international standard IEC 61400-23: full-scale structural testing of rotor blades. Comparing the measured data with the FE analysis results, we simulated the situations the blade had experienced, and then found what caused the delamination failure as well as the problem of the conventional design approach. The bumping motions of the blade shell caused by geometric complexities between the maximum chord and the root alter significantly the load distribution at the end of the blade root. Therefore, to enhance the structural safety of a large composite wind turbine blade, a more detailed FE analysis on the blade root in the design stage is needed.</P>

우리나라 돌날몸돌 제작기술체계의 특징과 변화 시고

이헌종,이상석 한국구석기학회 2014 한국구석기학보 Vol.- No.29

Chronology of blade tool culture is examined through absolute dating, it is confirmed that it had been maintained for 20~15ka around 35ka in Korea. As for the raw material for the blade tools, the volcanic rocks ro sedimentary rocks were mainly used for tis manufacturing. The blade core confirmed at the site had passed through the core shaping process in order to detach blades. Regarding the relationship between the striking platform and the working face, the type of one striking platform-one working face is the most popular and the next is the type of 2 striking platform-1 working face. In the case of large blade core, the type of one striking platform-one working face is main techonological system, and the middle or small size blade core have various types of striking platform and working face. According to the research of blade core with blade tools, 2/3 length or whole length of blades were consecutively detached using hinging method on the basis of perpendicular flaking. And the straight blade received from this process use for the materials of tanged point and end scraper and others. It can be classified as two stages based on the change of blade core technical system. The 1st stage(35ka~30ka) is characterized mainly pebble tool tradition with small number of blade cores and blade tools without controled technological system, and it is belonged to Hopyeong-dong site and Chongok site. The 2nd stage(30~15ka) is the charaterized the typical blade tool technology, and it is included to Yongsan-dong site, Gorae-ri site, Jinguneul site, Juknae-ri site, Oji-ri site, Sinhwa-ri site, Jeongjang-ri site etc. 절대연대를 통해 살펴보면, 우리나라 돌날석기문화의 편년은, 35ka를 전후로 시작하여 20~15ka 어느 시기까지 지속되는 것으로 확인된다. 석재는 화산암이나 퇴적암계의 암석이 주류를 이룬다. 유적에서 확인된 돌날몸돌을 타격면 및 작업면의 상관관계에 따르면, 1타격면 1작업면의 형태가 가장 많고, 그 다음은 2타격면·1작업면의 몸돌이다. 대형의 돌날몸돌일수록 1타격면 1작업면의 형태가 가장 많고, 중·소형의 돌날몸돌은 타격면과 작업면의 형태가 다양해진다. 돌날몸돌과 돌날을 복합적으로 분석해 보면 수직박리를 기반한 hinging기법을 이용하여 2/3 혹은 전 길이의 돌날을 연속적으로 박리하였던 것을 알 수 있다. 이러한 과정을 통해 얻어진 비교적 곧은 돌날은 그런 돌날이 필요한 슴베찌르개와 끝날긁개 및 다른 돌날석기 제작의 소재로 활용되었다. 돌날석기 제작기법 변화는 크게 2단계로 나누어 설명할 수 있다. 1기는 자갈돌석기전통을 기반으로 하고 있으며 부분적으로 돌날석기관련 석기들과 몸돌이 공반되는 시기(35ka~30ka)이며, 호평동 유적과 촌곡 유적이 그에 해당된다. 2기는 전형적인 돌날석기 제작 기술체계를 잘 나타내주는 시기 (30~15ka)로서 용산동 유적, 고례리 유적, 진그늘 유적, 죽내리 유적, 오지리 유적, 신화리 유적, 정장리 유적 등이 이에 해당된다.

Flutter study of flapwise bend-twist coupled composite wind turbine blades

Touraj Farsadi,Altan Kayran 한국풍공학회 2021 Wind and Structures, An International Journal (WAS Vol.32 No.3

Bending-twisting coupling induced in big composite wind turbine blades is one of the passive control mechanisms which is exploited to mitigate loads incurred due to deformation of the blades. In the present study, flutter characteristics of bend-twist coupled blades, designed for load alleviation in wind turbine systems, are investigated by time-domain analysis. For this purpose, a baseline full GFRP blade, a bend-twist coupled full GFRP blade, and a hybrid GFRP and CFRP bend-twist coupled blade is designed for load reduction purpose for a 5 MW wind turbine model that is set up in the wind turbine multi-body dynamic code PHATAS. For the study of flutter characteristics of the blades, an over-speed analysis of the wind turbine system is performed without using any blade control and applying slowly increasing wind velocity. A detailed procedure of obtaining the flutter wind and rotational speeds from the time responses of the rotational speed of the rotor, flapwise and torsional deformation of the blade tip, and angle of attack and lift coefficient of the tip section of the blade is explained. Results show that flutter wind and rotational speeds of bend-twist coupled blades are lower than the flutter wind and rotational speeds of the baseline blade mainly due to the kinematic coupling between the bending and torsional deformation in bend-twist coupled blades.

일본 도호쿠(東北)지역의 석인석기군 연구

장용준(Chang, Yongjoon) 한국고고학회 2018 한국고고학보 Vol.0 No.107

일본 도호쿠(東北)지역은 혼슈지역에서 석인기법이 발달한 곳이다. 이 지역의 석인기법은 비능조정 방식과 능조정 방식으로 나눌 수 있다. 비능조정 석인기법은 현지에서 조달한 석재를 이용하였다. 특히 도호쿠지역과 간토우지역을 제외한 일본열도, 한반도, 러시아, 중국지역에서는 찾아볼 수 없는 독특한 기법이었다. 반면, 능조정 석인기법은 규질혈암을 이용하였다. 특히 원산지유적들이 야마가타현(山形縣)과 아키타현(秋田縣)을 중심으로 발견되었다. 일본열도에서 자주 사용된 흑요석은 석인석기군의 중요한 석재로 채택되지 못하였다. 일본열도 내에서 도호쿠지역의 능조정 석인석기군은 다른 지역에서는 찾아보기 힘들 정도로 기술이 뛰어났다. 석인관련 접합유물을 분석한 결과, 석인기법과 관련된 특수한 기술들이 모두 적용되었다. 능조정 석인기법은 후기구석기 초의 소형박편석기군 또는 간토우지역이나 쥬부지역의 비능조정 석인기법에서 기술적 연원을 찾기는 어려웠다. 비능조정 석인석기군에서 능조정 석인석기군으로 시간적인 변화는 인정되지만, 기술적인 계통의 상관성은 찾을 수 없었다. 후기구석기 중엽의 능조정 석인석기군은 홋카이도를 제외하면 일본열도에서는 주로 도호쿠지역에서만 사용되었다. 도호쿠지역의 능조정 석인집단은 새로운 제작기술과 수렵정보를 도구에 접목시켰다. 대량으로 생산된 석인은 착장형 수렵구(기부가공첨두기)를 만드는 데 우선적으로 사용하였다. 하지만, 비능조정 석인석기군은 제대로 된 수렵도구와의 상관성을 찾기 어려웠다. 두 석기군은 수렵도구의 제작수준, 도구사용의 방식 등에서 분명한 차이가 있었다. Blade tools and technology were developed in the Yamagata and Akita Prefectures in the Tohoku (northeast part of Honshu) region of Japan. This area is home to many sources of silicate shale which was used by Late Paleolithic people to make blade tools and spears. These sources were optimized for the production of blade tools in Japan. The Honshu region of Japan (except Tohoku region) have not siliceous shale that can make blades. Many symmetrical blades were made using the crested technique. In Japan, the blade technology of the Tohoku region did not evolve from the non-crested technique. The blade technology appeared at around 30ka. The Tohoku region had witnessed flake tool industries in the early Late Paleolithic. Blades produced between 27ka and 22ka made up a dominant component of the stone tool industries of the Tohoku region. The foraging groups of this area that used the blades were different from the groups that made flake tools. Among the many blades, the well-shaped blades were used primarily in hafted spears as tanged points. The foraging groups of the Tohoku region that used blades had produced new types of tools for their livelihood. Foraging groups using the crested technique blade technology would have had a more extensive activity area, compared to groups using flake tools.

기도확보가 어려운 상황에서 Miller blade와 Macintosh blade를 이용한 기관내삽관의 비교 : 숙련되지 않은 인턴을 대상으로 한 마네킨 연구

이미림,김철태,이효철 사단법인 한국응급구조학회 2018 한국응급구조학회지 Vol.22 No.3

Purpose: The purpose of this study was to compare laryngoscopic views and ease of use and success of intubation, via the percentage of glottic opening (POGO) scale when using the Miller blade and Macintosh blade in paraglossal approach. Methods: Forty intern doctors were randomized for laryngoscopy to be performed in a crossover manner. They performed endotracheal intubation with Miller blade and Macintosh blade in two airway scenarios: normal airway and difficult airway with edema. We observed the rate of successful intubation, time required for visualizing the glottis, time to complete endotracheal intubation, ease of intubation, and the POGO scale. Results: In the normal airway, there was no difference in intubation between the two endoscopes. In the difficult airway, the time for visualizing the glottis (7.80 versus 10.24 sec; p=.006), the time to tube passage (19.38 versus 23.03 sec; p=.038) and the time to complete endotracheal intubation (21.84 versus 28.54 sec; p=.022) with Miller blade was shorter than with Macintosh blade. The POGO scale(%) of the Miller blade was higher than that of the Macintosh blade’s (62.25 versus 56.32; p=.030). Conclusion: Compared to the Macintosh blade, Miller blade provided better visualization of the glottis and POGO scale, and faster time to completion of endotracheal intubation.

대퇴 전자부 골절에 있어 U-Blade를 이용한 감마정과 Zimmer Natural Nail의 치료 비교

서재성 ( Jae Sung Suh ),류형곤 ( Hyung-gon Ryu ),노영주 ( Young Ju Roh ),신대원 ( Dae Won Shin ),김상민 ( Sang-min Kim ) 대한골절학회 2021 대한골절학회지 Vol.34 No.2

목적: 대퇴 전자간 골절 치료에 있어 U-blade 3세대 감마정과 ZNN의 치료 결과를 임상적, 방사선학적 측면에서 비교 분석하였다. 대상 및 방법: 2015년 7월부터 2018년 12월까지 대퇴 전자간 골절로 수술한 환자군 129예(U-blade감마정 90예, ZNN 39예) 중 65세 미만, 보행 불가자, 고에너지 및 병적골절, 6개월 미만 추시자 제외 후 선택편향을 줄이기 위해 나이, 체질량지수, 골밀도, 골절 유형을 기준으로 성향점수매칭을 시행하여 각각 39예를 선출하였다. 임상적으로 수술시간, 출혈량, 술 전후 보행 정도, HHS를 평가하였고 방사선학적으로 정복의 안정성, 지연나사 고정 위치 및 대퇴골두 천공, 활강거리, TAD, 골유합 기간 등을 비교하였다. 결과: 임상적으로는 두 군 간 차이가 없었으며 방사선학적으로 TAD가 U-blade감마정군에서 유의하게 길었고(23.4 mm vs. 21.0 mm) (p=0.042), 지연나사 골두천공 또한 U-blade감마정군에서 1예 관찰되었으나 그 외에는 두 군 간 차이가 없었다. 결론: 대퇴 전자간 골절 치료에 있어 U-blade감마정과 ZNN의 치료 결과 통계적으로 유의한 차이는 없었고 U-blade의 추가 삽입으로 인한 장점은 갖기 어려울 것으로 판단된다. Purpose: This study was performed to compare the clinical results and radiological follow-up differences between intertrochanteric fractures treated with the U-blade Gamma3 nail or the Zimmer natural nail (ZNN). Materials and Methods: The medical records of 129 cases diagnosed with an intertrochanteric fracture (90 cases of U-blade Gamma3 nail, 39 cases of ZNN) from July 2015 to December 2018 were reviewed. Patients were assigned to a U-blade Gamma3 nail (n=39) or a ZNN (n=39) group. To reduce selective bias, groups were subjected to Propensity score matching by age, body mass index, bone mineral density, and fracture type. Patients that met the following criteria were excluded; age <65 years, non-ambulatory, high energy or pathologic fracture, and a follow-up of <6 months. Operation times, estimated blood losses, preoperative and postoperative Koval grades, Harris hip score and radiological lag screw positions in the femoral head, reduction quality, cut-out, tip-apex distance (TAD), lag screw sliding distances, and times to union were compared. Results: Clinical results were similar in the two groups, but lag screw TAD was significantly greater in U-blade Gamma3 nail group (23.4 mm vs. 21.0 mm) (p=0.042). One case of cut-out occurred in the U-blade Gamma3 nail group, but no other nail-related postoperative complication was noted. Conclusion: No significant difference was observed between the outcomes of U-blade Gamma3 nail or ZNN treatments of intertrochanteric fractures. We conclude that the U-blade confers no specific advantage.