On the Enhancement of the Thrust Production of LPMSMs: Application to Ropeless Elevators

In flapping underwater vehicles the propulsive performance of harmonically sinusoidal heaving and pitching foil will be degraded by some awkward changes in effective angle of attack profile, as the Strouhal number increases. This paper surveys different angle of attack profiles (Sinusoidal, Square, Sawtooth and Cosine) and considers their thrust production ability. In the wide range of Strouhal numbers, thrust production of Square profile is considerable but it has a discontinuity in heave velocity profile, in which an infinite acceleration exists. This problem poses a significant defect in control of flapping foil. A novel profile function is proposed to omit sharp changes in heave velocity and acceleration. Furthermore, an optimum profile is found for different Strouhal numbers with respect to Square angle of attack profile.DOI: http://dx.doi.org/10.3329/jname.v10i2.14229

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Computational Investigation of Thrust Production of a Dolphin at Various Swimming Speeds

10.1115/fedsm2021-65792 ◽

2021 ◽

Author(s):

Junshi Wang ◽

Vadim Pavlov ◽

Zhipeng Lou ◽

Haibo Dong

Keyword(s):

Surface Pressure ◽

Swimming Performance ◽

Three Dimensional ◽

Numerical Approach ◽

Immersed Boundary ◽

Reconstruction Method ◽

Force Coefficient ◽

Speed Increase ◽

Generation Mechanisms ◽

Thrust Production

Abstract Dolphins are known for their outstanding swimming performance. However, the difference in flow physics at different speeds remains elusive. In this work, the underlying mechanisms of dolphin swimming at three speeds, 2 m/s, 5 m/s, and 8 m/s, are explored using a combined experimental and numerical approach. Using the scanned CAD model of the Atlantic white-sided dolphin (Lagenorhynchus acutus) and virtual skeleton-based surface reconstruction method, a three-dimensional high-fidelity computational model is obtained with time-varying kinematics. A sharp-interface immersed-boundary-method (IBM) based direct numerical simulation (DNS) solver is employed to calculate the corresponding thrust production, wake structure, and surface pressure at different swimming speeds. It is found that the fluke keeps its effective angle of attack at high values for about 60% of each stroke. The total pressure force coefficient along the x-axis converges as the speed increase. The flow and surface pressure analysis both show considerable differences between lower (2 m/s) and higher (5 m/s and 8 m/s) speeds. The results from this work help to bring new insight into understanding the force generation mechanisms of the highly efficient dolphin swimming and offer potential suggestions to the future designs of unmanned underwater vehicles.

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Thrust Production in Highly Flexible Pectoral Fins: A Computational Dissection

Marine Technology Society Journal ◽

10.4031/mtsj.45.4.7 ◽

2011 ◽

Vol 45 (4) ◽

pp. 56-64 ◽

Cited By ~ 3

Author(s):

Srinivas Ramakrishnan ◽

Meliha Bozkurttas ◽

Rajat Mittal ◽

George V. Lauder

Keyword(s):

Computational Analysis ◽

Autonomous Underwater Vehicles ◽

Underwater Vehicles ◽

Bluegill Sunfish ◽

Robust Performance ◽

Pectoral Fin ◽

Pectoral Fins ◽

And Performance ◽

Thrust Production ◽

Computational Dissection

AbstractBluegill sunfish pectoral fins represent a remarkable success in evolutionary terms as a means of propulsion in challenging environments. Attempts to mimic their design in the context of autonomous underwater vehicles have overwhelmingly relied on the analysis of steady swimming. Experimental observations of maneuvers reveal that the kinematics of fin and wake dynamics exhibit characteristics that are distinctly different from steady swimming. We present a computational analysis that compares, qualitatively and quantitatively, the wake hydrodynamics and performance of the bluegill sunfish pectoral fin for two modes of swimming: steady swimming and a yaw turn maneuver. It is in this context that we comment on the role that flexibility plays in the success of the pectoral fin as a versatile propulsor. Specifically, we assess the performance of the fin by conducting a “virtual dissection” where only a portion of fin is retained. Approximately 90% of peak thrust for steady swimming is recovered using only the dorsal half. This figure drops to 70% for the yaw turn maneuver. Our findings suggest that designs based on fin analysis that account for various locomotion modes can lead to more robust performance than those based solely on steady swimming.

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Thrust Enhancement From Radial Velocity in Squid Inspired Thrusters

Volume 5: Ocean Engineering; CFD and VIV ◽

10.1115/omae2012-83976 ◽

2012 ◽

Author(s):

Michael Krieg ◽

Kamran Mohseni

Keyword(s):

Radial Velocity ◽

Driving Mechanism ◽

Low Thrust ◽

Vortex Ring Formation ◽

Total Impulse ◽

Fluid Jets ◽

Force Range ◽

And Control ◽

Thrust Production ◽

Control Surfaces

Squid and jellyfish generate propulsive forces by successively taking in and expelling high momentum jets of water. This method of propulsion offers several advantages to underwater vehicles/robots. The driving mechanism can be placed internal to the vehicle, reducing the drag associated with an abundance of external thrusters and control surfaces. The thrusters can generate accurate predictable forcing in the low thrust range, while still generating thrust nearly instantaneously over the entire force range. Vortex ring formation dynamics play an important role in creating thrust. It is observed that squid and jellyfish eject fluid jets which are not exactly parallel, and have a contracting velocity in the radial direction. A prototype thruster was developed which generates both parallel and converging propulsive jets. The total impulse of the jet is determined from DPIV techniques to determine the effect a non-zero radial velocity had on thrust production. The radial velocity was observed to increase the total impulse of the jet by 70% for low stroke ratio jets, and 75% for large stroke ratio jets.

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HOW THE BODY CONTRIBUTES TO THE WAKE IN UNDULATORY FISH SWIMMING

Journal of Experimental Biology ◽

10.1242/jeb.204.16.2751 ◽

2001 ◽

Vol 204 (16) ◽

pp. 2751-2762 ◽

Cited By ~ 24

Author(s):

ULRIKE K. MÜLLER ◽

JORIS SMIT ◽

EIZE J. STAMHUIS ◽

JOHN J. VIDELER

Keyword(s):

Body Wave ◽

Vortex Pair ◽

Maximum Flow ◽

The Body ◽

Double Row ◽

Image Velocimetry ◽

Swimming Efficiency ◽

Swimming Mode ◽

Thrust Production ◽

Tail Beat

SUMMARY Undulatory swimmers generate thrust by passing a transverse wave down their body. Thrust is generated not just at the tail, but also to a varying degree by the body, depending on the fish's morphology and swimming movements. To examine the mechanisms by which the body in particular contributes to thrust production, we chose eels, which have no pronounced tail fin and hence are thought to generate all their thrust with their body. We investigated the interaction between body movements and the flow around swimming eels using two-dimensional particle image velocimetry. Maximum flow velocities adjacent to the eel's body increase almost linearly from head to tail, suggesting that eels generate thrust continuously along their body. The wake behind eels swimming at 1.5Ls-1, where L is body length,consisted of a double row of double vortices with little backward momentum. The eel sheds two vortices per half tail-beat, which can be identified by their shedding dynamics as a start—stop vortex of the tail and a vortex shed when the body-generated flows reach the `trailing edge' and cause separation. Two consecutively shed ipsilateral body and tail vortices combine to form a vortex pair that moves away from the mean path of motion. This wake shape resembles flow patterns described previously for a propulsive mode in which neither swimming efficiency nor thrust is maximised but sideways forces are high. This swimming mode is suited to high manoeuvrability. Earlier recordings show that eels also generate a wake reflective of maximum swimming efficiency. The combined findings suggest that eels can modify their body wave to generate wakes that reflect their propulsive mode.

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Numerical investigation on thrust production and unsteady mechanisms of three-dimensional oscillating wing

Journal of Mechanical Science and Technology ◽

10.1007/s12206-019-1134-z ◽

2019 ◽

Vol 33 (12) ◽

pp. 5889-5900 ◽

Cited By ~ 1

Author(s):

A. R. Shanmugam ◽

C. H. Sohn

Keyword(s):

Numerical Investigation ◽

Three Dimensional ◽

Thrust Production

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Experimental and Numerical Investigations on the Thrust Production Process of Magnetoplasma Sail

AIAA Guidance, Navigation, and Control Conference ◽

10.2514/6.2010-6773 ◽

2010 ◽

Author(s):

Ikkoh Funaki ◽

Hiroshi Yamakawa ◽

Yoshihiro Kajimura ◽

Kazuma Ueno ◽

Yuya Oshio ◽

...

Keyword(s):

Production Process ◽

Numerical Investigations ◽

Thrust Production

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Leading edge strengthening and the propulsion performance of flexible ray fins

Journal of Fluid Mechanics ◽

10.1017/jfm.2011.538 ◽

2012 ◽

Vol 693 ◽

pp. 402-432 ◽

Cited By ~ 38

Author(s):

Kourosh Shoele ◽

Qiang Zhu

Keyword(s):

Phase Difference ◽

Structural Characteristics ◽

Leading Edge ◽

Immersed Boundary ◽

Propulsion Performance ◽

Thrust Generation ◽

Generation Capacity ◽

Effective Angle ◽

Edge Separation ◽

Thrust Production

AbstractA numerical model of a ray-reinforced fin is developed to investigate the relation between its structural characteristics and its force generation capacity during flapping motion. In this two-dimensional rendition, the underlying rays are modelled as springs, and the membrane is modelled as a flexible but inextensible plate. The fin kinematics is characterized by its oscillation frequency and the phase difference between different rays (which generates a pitching motion). An immersed boundary method (IBM) is applied to solve the fluid–structure interaction problem. The focus of the current paper is on the effects of ray flexibility, especially the detailed distribution of ray stiffness, upon the capacity of thrust generation. The correlation between thrust generation and features of the surrounding flow (especially the leading edge separation) is also examined. Comparisons are made between a fin with rigid rays, a fin with identical flexible rays, and a fin with flexible rays and strengthened leading edge. It is shown that with flexible rays, the thrust production can be significantly increased, especially in cases when the phase difference between different rays is not optimized. By strengthening the leading edge, a higher propulsion efficiency is observed. This is mostly attributed to the reduction of the effective angle of attack at the leading edge, accompanied by mitigation of leading edge separation and dramatic changes in characteristics of the wake. In addition, the flexibility of the rays causes reorientation of the fluid force so that it tilts more towards the swimming direction and the thrust is thus increased.

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