Propulsion performance and unsteady forces of a pump-jet propulsor with different pre-swirl stator parameters

2020 ◽  
Vol 100 ◽  
pp. 102184 ◽  
Author(s):  
Haiting Yu ◽  
Ningyuan Duan ◽  
Hongxing Hua ◽  
Zhenguo Zhang
2009 ◽  
Vol 14 (3) ◽  
pp. 296-309 ◽  
Author(s):  
Vishwanath Nagarajan ◽  
Dong-Hoon Kang ◽  
Kazuhiko Hasegawa ◽  
Kenjiro Nabeshima ◽  
Toshihiko Arii

Author(s):  
Yu-Sheng Yang ◽  
Alicia M. Koontz ◽  
Yu-Hsuan Hsiao ◽  
Cheng-Tang Pan ◽  
Jyh-Jong Chang

Maneuvering a wheelchair is an important necessity for the everyday life and social activities of people with a range of physical disabilities. However, in real life, wheelchair users face several common challenges: articulate steering, spatial relationships, and negotiating obstacles. Therefore, our research group has developed a head-mounted display (HMD)-based intuitive virtual reality (VR) stimulator for wheelchair propulsion. The aim of this study was to investigate the feasibility and efficacy of this VR stimulator for wheelchair propulsion performance. Twenty manual wheelchair users (16 men and 4 women) with spinal cord injuries ranging from T8 to L2 participated in this study. The differences in wheelchair propulsion kinematics between immersive and non-immersive VR environments were assessed using a 3D motion analysis system. Subjective data of the HMD-based intuitive VR stimulator were collected with a Presence Questionnaire and individual semi-structured interview at the end of the trial. Results indicated that propulsion performance was very similar in terms of start angle (p = 0.34), end angle (p = 0.46), stroke angle (p = 0.76), and shoulder movement (p = 0.66) between immersive and non-immersive VR environments. In the VR episode featuring an uphill journey, an increase in propulsion speed (p < 0.01) and cadence (p < 0.01) were found, as well as a greater trunk forward inclination (p = 0.01). Qualitative interviews showed that this VR simulator made an attractive, novel impression and therefore demonstrated the potential as a tool for stimulating training motivation. This HMD-based intuitive VR stimulator can be an effective resource to enhance wheelchair maneuverability experiences.


2014 ◽  
Vol 26 (12) ◽  
pp. 125110 ◽  
Author(s):  
O. Lehmkuhl ◽  
I. Rodríguez ◽  
R. Borrell ◽  
J. Chiva ◽  
A. Oliva

Author(s):  
Friedrich-Karl Benra ◽  
Hans Josef Dohmen ◽  
Oliver Schneider

The extreme vibrations of sewage water pumps with single-blade impellers are induced mainly by interaction of the flow in the impeller and the casing. The resulting periodically unsteady forces affect the impeller and produce radial deflections of the pump shaft. These oscillations of the rotor are transferred to the pump casing and attached pipes. They can be recognized as vibrations at the bearing blocks or at the pump casing. The present contribution describes the investigation of the transient flow in a sewage water pump. The three-dimensional, viscous, unsteady flow in a pump with a single blade impeller is determined by numerical simulation. After that the hydrodynamic stimulation forces are calculated from the so known transient flow field. The forces can be classified into pressure and friction forces. The pressure forces usually exceed the friction forces on several orders of magnitude. A separate view on the fluid-wetted impeller surfaces shows that the pressure forces acting on the blade are clearly larger than the forces at the hub and at the shroud. So they are decisive for the vibration amplitudes of single-blade sewage water pumps. By a following dynamic analysis of the pump rotor using a commercial Finite-Element-Method (FEM) the resulting vibration amplitudes are determined for several operating points. With the known pressure field and the calculated vibration amplitudes the vibration behavior of sewage water pumps can be influenced during the design by changing the relevant construction parameters.


2020 ◽  
Vol 10 (18) ◽  
pp. 6226
Author(s):  
Zhanfeng Qi ◽  
Lishuang Jia ◽  
Yufeng Qin ◽  
Jian Shi ◽  
Jingsheng Zhai

A numerical investigation of the propulsion performance and hydrodynamic characters of the full-active flapping foil under time-varying freestream is conducted. The finite volume method is used to calculate the unsteady Reynolds averaged Navier–Stokes by commercial Computational Fluid Dynamics (CFD) software Fluent. A mesh of two-dimensional (2D) NACA0012 foil with the Reynolds number Re = 42,000 is used in all simulations. We first investigate the propulsion performance of the flapping foil in the parameter space of reduced frequency and pitching amplitude at a uniform flow velocity. We define the time-varying freestream as a superposition of steady flow and sinusoidal pulsating flow. Then, we study the influence of time-varying flow velocity on the propulsion performance of flapping foil and note that the influence of the time-varying flow is time dependent. For one period, we find that the oscillating amplitude and the oscillating frequency coefficient of the time-varying flow have a significant influence on the propulsion performance of the flapping foil. The influence of the time-varying flow is related to the motion parameters (reduced frequency and pitching amplitude) of the flapping foil. The larger the motion parameters, the more significant the impact of propulsion performance of the flapping foil. For multiple periods, we note that the time-varying freestream has little effect on the propulsion performance of the full-active flapping foil at different pitching amplitudes and reduced frequency. In summary, we conclude that the time-varying incoming flow has little effect on the flapping propulsion performance for multiple periods. We can simplify the time-varying flow to a steady flow field to a certain extent for numerical simulation.


2014 ◽  
Vol 2014 ◽  
pp. 1-13
Author(s):  
Yonghui Xie ◽  
Kun Lu ◽  
Di Zhang ◽  
Gongnan Xie

The thrust generation performance of airfoils with modified pitching motion was investigated by computational fluid dynamics (CFD) modeling two-dimensional laminar flow at Reynolds number of 104. The effect of shift distance of the pitch axis outside the chord line(R), reduced frequency(k), pitching amplitude(θ), pitching profile, and airfoil shape (airfoil thickness and camber) on the thrust generated and efficiency were studied. The results reveal that the increase inRandkleads to an enhancement in thrust generation and a decrease in propulsive efficiency. Besides, there exists an optimal range ofθfor the maximum thrust and the increasingθinduces a rapid decrease in propulsive efficiency. Six adjustable parameters(K)were employed to realize various nonsinusoidal pitching profiles. An increase inKresults in more thrust generated at the cost of decreased propulsive efficiency. The investigation of the airfoil shape effect reveals that there exists an optimal range of airfoil thickness for the best propulsion performance and that the vortex structure is strongly influenced by the airfoil thickness, while varying the camber or camber location of airfoil sections offers no benefit in thrust generation over symmetric airfoil sections.


1986 ◽  
Vol 52 (475) ◽  
pp. 1197-1206
Author(s):  
Takahiko TANAHASHI ◽  
Tatsuo SAWADA ◽  
Eriya KANAI ◽  
Akira CHINO ◽  
Tsuneyo ANDO

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