scholarly journals Numerical and Experimental Comparison of Spinnaker Aerodynamics Close to Curling

2021 ◽  
Vol 06 (01) ◽  
pp. 118.0-132.0
Author(s):  
Benoît Augier ◽  
Benoît Paillard ◽  
Matthieu Sacher ◽  
Jean-Baptiste Leroux ◽  
Nicolas Aubin

When sailing downwind with a spinnaker, the “verge of curling” is one of the common recommendations that sailors follow for efficient sailing. Wind tunnel experiments on spinnaker models conducted by Aubin et al. (2017) in the Twisted Flow Wind Tunnel of the Yacht Research Unit of the University of Auckland have shown that curling can be related to better performance at Apparent Wind Angle ≥ 100°. In the present article, we will focus on the aerodynamic performance jump observed at Apparent Wind Angle AWA = 100°, where the drive force increases up to 15% when the sail starts to flap. Thanks to four triggered HD cameras and coded targets stuck on the sail, three flying shapes of the spinnaker are reconstructed by photogrammetry for different sheet lengths from over trimmed to flapping occurrence. The pimpleFOAM solver from OpenFOAM is used to simulate the aerodynamics of the three rigid extracted flying shapes. Results highlight the ability of the model to simulate the experimental jump observed closed to curling and the significant confinement effect of the roof of the wind tunnel.

2020 ◽  
Vol 10 (23) ◽  
pp. 8612
Author(s):  
Yao Lei ◽  
Yiqiang Ye ◽  
Zhiyong Chen

The coaxial Tri-rotor micro air vehicle (MAV) is composed of three coaxial rotors where the aerodynamic characteristics of is complicated in flight especially when the wind effect is introduced. In this paper, the hovering performance of a full-scale coaxial Tri-rotor MAV is analyzed with both the simulations and wind tunnel experiments. Firstly, the wind effect on the aerodynamic performance of coaxial Tri-rotor MAV is established with different rotor speed (1500–2300 rpm) and horizontal wind (0–4 m/s). Secondly, the thrust and power consumption of coaxial Tri-rotor (L/D = 1.6) were obtained with low-speed wind tunnel experiments. Furthermore, the streamline distribution, pressure distribution, velocity contour and vortex distribution with different horizontal wind conditions are obtained by numerical simulations. Finally, combining the experiment results and simulation results, it is noted that the horizontal wind may accelerate the aerodynamic coupling, which resulting in the greater thrust variation up to 9% of the coaxial Tri-rotor MAV at a lower rotor speed. Moreover, the aerodynamic performance is decreased with more power consumption at higher rotor speed where the wind and the downwash flow are interacted with each other. Compared with no wind flow, the shape of the downwash flow and the deformation of the vortex affect the power loading and figure of metric accordingly.


2017 ◽  
Vol 260 ◽  
pp. 85-91 ◽  
Author(s):  
Gurvan Jodin ◽  
Johannes Scheller ◽  
Eric Duhayon ◽  
Jean François Rouchon ◽  
Marianna Braza

Amongst current aircraft research topics, morphing wing is of great interest for improving the aerodynamic performance. A morphing wing prototype has been designed for wind tunnel experiments. The rear part of the wing - corresponding to the retracted flap - is actuated via a hybrid actuation system using both low frequency camber control and a high frequency vibrating trailing edge. The camber is modified via surface embedded shape memory alloys. The trailing edge vibrates thanks to piezoelectric macro-fiber composites. The actuated camber, amplitude and frequency ranges are characterized. To accurately control the camber, six independent shape memory alloy wires are controlled through nested closed-loops. A significant reduction in power consumption is possible via this control strategy. The effects on flow via morphing have been measured during wind tunnel experiments. This low scale mock-up aims to demonstrate the hybrid morphing concept, according to actuator capabilities point of view as well as aerodynamic performance.


Aerospace ◽  
2005 ◽  
Author(s):  
James R. Sonnenmeier ◽  
Oladipo Onipede ◽  
Andrew J. Detar ◽  
Heather L. Myers

Aerodynamic performance of aircraft can be changed by moving separate surfaces which are mechanically connected to the main wing and moved with complex linkages. A possible alternative method of changing performance with less mechanical complexity is presented. Instead of separate control surfaces, the shape of complete aerodynamic structures can be changed with shape memory alloy (SMA) materials as part of the structure. In this work SMA wire is wrapped around a simple test wing. When activated by heating, the wire contracts which results in twisting the wing. The angle of attack along the wingspan changes which changes the aerodynamic forces on the wing. This could be used to optimize the flight condition. Results are presented from initial wind tunnel experiments which show the change in lift due to twisting. Aerodynamic models that account for the variable angle of attack along the span are also developed. The results from the experiments and aerodynamic model are compared.


2019 ◽  
Vol 9 (22) ◽  
pp. 4797
Author(s):  
Yao Lei ◽  
Mingxin Cheng

In this paper, the aerodynamic performance of a Hex-rotor unmanned aerial vehicle (UAV) with different rotational speeds (1500–2300 RPM) considering the horizontal airflow conditions is analyzed by both simulations and experiments. A low-speed wind tunnel experiments platform is applied to measure the thrust, torque, and power consumption of a Hex-rotor UAV with different rotational speeds in horizontal airflow, which varied from 0 m/s–4 m/s. First, this paper introduces the effect of horizontal airflow on a UAV. Then, the low-speed wind tunnel experiments were carried out on a Hex-rotor UAV (D/L = 0.56) with different horizontal velocities to determine the hover performance. Finally, numerical simulations were obtained with the streamline distributions, pressure distributions, velocity contour, and vortex distributions at different horizontal airflow conditions to describe the aerodynamic interference effect of different horizontal airflows. Combined with the experimental results and numerical simulations results, the horizontal airflow proved to have a significant influence on the aerodynamic performance of the Hex-rotor UAV with an increase in thrust and power. Indeed, the streamlines in the flow field were coupled to each other at the presence of the incoming airflow. Especially when the incoming airflow was larger, the Hex-rotor UAV could properly use low-speed flight to maintain high power loading. Finally, it is inferred that the aerodynamic performance of the Hex-rotor UAV is also related to the movement and deformation of the vortex at the tip of the rotor.


Author(s):  
Amin Moosavian ◽  
Lawren L. Gamble ◽  
Alexander M. Pankonien ◽  
Daniel J. Inman

This work aims to investigate how bio-inspired morphing wings built with state-of-the-art materials affect the aerodynamics and extend the range of flight conditions. In particular, this study investigates the aerodynamic effects of coupled airfoil and planform sweep morphing. The morphed geometries were chosen to resemble a current morphing design that uses Macro Fiber Composites (MFCs) and Shape Memory Alloy (SMA) wires. The primary mode of camber actuation is achieved using the MFCs which are supplemented using antagonistic SMA wires, forming a hinge ahead of the MFCs. The SMA hinge also allows for bi-directional actuation, resulting in a reflexed airfoil. Numerical simulations were conducted using a Reynolds-averaged-Navier-Stokes (RANS) turbulence model for low-Reynolds-number flow, in addition to wind tunnel experiments. Nine different wing configurations were considered consisting of combinations of 3 sweep angles and 3 airfoil profiles, including unactuated (baseline), monotonic camber actuation, and reflex actuation. These geometries were 3D printed on a high resolution printer. Tests were conducted in a 2 ft. × 2 ft. wind tunnel at the University of Michigan at a flow speed of 10 m/s, consistent with the flow regime expected for this scale of aircraft. The preliminary results suggest a definite improvement in flight performance associated with the proposed coupling.


Energies ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1808
Author(s):  
S. Arunvinthan ◽  
V.S. Raatan ◽  
S. Nadaraja Pillai ◽  
Amjad A. Pasha ◽  
M. M. Rahman ◽  
...  

A series of wind tunnel tests were carried out to determine the effect of shark scale-based vortex generators (SSVG) on a NACA 0015 symmetrical airfoil's aerodynamic characteristics. Three different sets of SSVG with varying geometrical parameters, such as chord length, amplitude, and wavelength, were designed and fabricated using 3D printing. The SSVG models were blended to the baseline NACA 0015 symmetrical airfoil. The wind tunnel experiments were performed over the test airfoil mounted with different sets of SSVG at various angles of attack, ranging from 0° to 24° in increments of 3°, and operating in the range of Re = 2 × 105. The results revealed that the SSVG blended test airfoil reduced the drag and increased the maximum coefficient of lift (CLmax), thereby enhancing the overall aerodynamic performance. The SSVG offered noteworthy aerodynamic benefits by effectively altering the flow and causing significant spanwise variation in the flow properties. Additionally, attempts were made to identify the optimum chordwise location to blend the SSVG for effective use.


Author(s):  
Somboon Watana, Ph.D.

Thai Buddhist meditation practice tradition has its long history since the Sukhothai Kingdom about 18th B.E., until the present day at 26th B.E. in the Kingdom of Thailand. In history there were many well-known Buddhist meditation master teachers, i.e., SomdejPhraBhudhajaraya (To Bhramarangsi), Phraajarn Mun Puritatto, Luang Phor Sodh Chantasalo, PhramahaChodok Yanasitthi, and Buddhadasabhikkhu, etc. Buddhist meditation practice is generally regarded by Thai Buddhists to be a higher state of doing a good deed than doing a good deed by offering things to Buddhist monks even to the Buddha. Thai Buddhists believe that practicing Buddhist meditation can help them to have mindfulness, peacefulness in their own lives and to finally obtain Nibbana that is the ultimate goal of Buddhism. The present article aims to briefly review history, and movement of Thai Buddhist Meditation Practice Tradition and to take a case study of students’ Buddhist meditation practice research at the university level as an example of the movement of Buddhist meditation practice tradition in Thailand in the present.


2011 ◽  
Vol 60 (1) ◽  
pp. 87-102 ◽  
Author(s):  
Andrea Farsang ◽  
József Szatmári ◽  
Gábor Négyesi ◽  
Máté Bartus ◽  
Károly Barta

Összefoglalva megállapítható, hogy nagyobb szélsebesség hatására több talajanyag erodálódott, és ezzel együtt megnőtt az áthalmozott tápanyag mennyisége is. Minden vizsgált szélsebesség esetében a szélerózió következtében 3–7%-kal megnőtt az 1 mm és annál nagyobb szemcsék, illetve aggregátumok aránya a kiindulási talajanyag felső 0–1 cm-es rétegében. A finomabb szemcse-, illetve aggregátum-átmérők esetén a fújatást követően csökkenést tapasztaltunk. A leginkább a 315 μm és az annál kisebb szemcsék aránya csökkent, átlagosan 1–2%-kal. A minták kémiai és fizikai elemzéseiből megállapítható, hogy a láda utáni humuszosabb, aggregátumosabb szerkezetű minták N-tartalma nagyobb, mint az alapmintáé. A fogók mintáiban nem tapasztaltunk feldúsulást egy vizsgált elem esetében sem, a fogókban összegyűlt talajanyag kálium- és foszfortartalma is kisebb volt, mint az alapmintáé. Ennek oka, hogy az itt csapdázódott üledékben kisebb a tápanyag-megkötődés helyéül szolgáló leiszapolható rész aránya, mint a kiindulási talajanyagban. A vizsgálatainkból látszik, hogy a szélerózió hatására a lebegtetve, illetve ugráltatva áthalmozott talajszemcsékkel és aggregátumokkal szállított humusz 500–3500 kg/ha nagyságrendben mozoghat a vizsgált csernozjom területen akár egyetlen szélesemény hatására is. A kálium-áthalmozódás mértéke elérheti a 100 kg/ha értéket, a foszforé a 70 kg/ha-t, a nitrogénveszteség mértéke pedig akár 200–300 kg/ha is lehet egy szélesemény alkalmával. E tápanyagmennyiség nagy része több száz méter, de akár kilométeres távolságokra is távozhat a területről. Az általunk végzett szélcsatornás vizsgálatok eredményei becslésnek tekinthetők, hiszen vizsgálatunk során növénymaradvány-mentes, szitált és légszáraz talajanyaggal dolgoztunk. A szitálás eredményeként csupán a 2 mm-es és annál kisebb aggregátumok maradtak meg, ami azonban az intenzív művelés alá vont, porosodott, leromlott szerkezetű talajfelszín körülményeit jól közelíti. Ugyanakkor a természetben zajló széleróziós eseményeknek a szélcsatorna-kísérlet csak leegyszerűsített modellváltozata, hiszen az általunk szimulált szélesemények 15 percig tartottak, s nem tudtunk széllökéseket előállítani, melyek a széleróziós események alakulásában nagy jelentőségűek. Ennek tudatában kell a kapott eredményeket értékelni, mégis érdemes velük foglalkozni. A terepi mérésekkel szemben a szélcsatornában végzett vizsgálatoknak éppen az a legfontosabb előnye, hogy ellenőrzött, kontrollált körülmények között végezzük a méréseket, így rengeteg olyan szempontot meg tudunk vizsgálni, amit terepi mérésekkel lehetetlen lenne. Ilyen szempontok a pontos szélsebesség és szélirány hatása, az erodált felület nagysága és tulajdonságai. Kutatásunk következő lépése a szélcsatornás kísérletekkel vizsgált mintaterületeken terepi, mobil szélcsatornás vizsgálatok végzése, valamint terepi üledékcsapdák elhelyezésével a valós szélesemények által elszállított talaj mennyiségének és minőségének meghatározása. Célunk mind pontosabb képet alkotni a hazai jó minőségű csernozjom talajok szélerózió okozta tápanyagveszteségének mértékéről. A mezőgazdasági művelés alatt álló csernozjom területek feltalajában a tápanyag és szerves anyag szélerózió útján történő mozgási törvényszerűségeinek feltárása több szempontból is hasznos: segítséget jelent a területi tervezésben, a defláció szempontjából optimális területhasználat és művelési módok meghatározásában. Képet kapunk arról, hogy a legnagyobb gazdasági potenciállal rendelkező termőtalajunk milyen veszélyeknek van kitéve, s hogy a nem megfelelő időben, nem megfelelő nedvességviszonyok mellett történő talajművelés következtében kialakuló szerkezetromlás (porosodás) miatti deflációs károk milyen tápanyagveszteséggel járhatnak együtt.


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