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Vortex-enhanced propulsion

Published online by Cambridge University Press:  22 December 2010

LYDIA A. RUIZ
Affiliation:
Department of Mechanical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
ROBERT W. WHITTLESEY
Affiliation:
Graduate Aeronautical Laboratories, California Institute of Technology, Pasadena, CA 91125, USA
JOHN O. DABIRI*
Affiliation:
Graduate Aeronautical Laboratories, California Institute of Technology, Pasadena, CA 91125, USA Department of Bioengineering, California Institute of Technology, Pasadena, CA 91125, USA
*
Email address for correspondence: jodabiri@caltech.edu

Abstract

It has been previously suggested that the generation of coherent vortical structures in the near-wake of a self-propelled vehicle can improve its propulsive efficiency by manipulating the local pressure field and entrainment kinematics. This paper investigates these unsteady mechanisms analytically and in experiments. A self-propelled underwater vehicle is designed with the capability to operate using either steady-jet propulsion or a pulsed-jet mode that features the roll-up of large-scale vortex rings in the near-wake. The flow field is characterized by using a combination of planar laser-induced fluorescence, laser Doppler velocimetry and digital particle-image velocimetry. These tools enable measurement of vortex dynamics and entrainment during propulsion. The concept of vortex added-mass is used to deduce the local pressure field at the jet exit as a function of the shape and motion of the forming vortex rings. The propulsive efficiency of the vehicle is computed with the aid of towing experiments to quantify hydrodynamic drag. Finally, the overall vehicle efficiency is determined by monitoring the electrical power consumed by the vehicle in steady and unsteady propulsion modes. This measurement identifies conditions under which the power required to create flow unsteadiness is offset by the improved vehicle efficiency. The experiments demonstrate that substantial increases in propulsive efficiency, over 50 % greater than the performance of the steady-jet mode, can be achieved by using vortex formation to manipulate the near-wake properties. At higher vehicle speeds, the enhanced performance is sufficient to offset the energy cost of generating flow unsteadiness. An analytical model explains this enhanced performance in terms of the vortex added-mass and entrainment. The results suggest a potential mechanism to further enhance the performance of existing engineered propulsion systems. In addition, the analytical methods described here can be extended to examine more complex propulsion systems such as those of swimming and flying animals, for whom vortex formation is inevitable.

Type
Papers
Copyright
Copyright © Cambridge University Press 2010

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References

REFERENCES

Batchelor, G. K. 2000 An Introduction to Fluid Dynamics. Cambridge University Press.CrossRefGoogle Scholar
Binder, G. & Didelle, H. 1981 Improvement of ejector thrust augmentation by pulsating or flapping jets. Proc. AGARD Conf. Fluid Dynamics of Jets with Applications to V/STOL, Lisbon, Portugal, vol. 308, pp. 1–11.Google Scholar
Blaurock, J. 1990 An appraisal of unconventional aftbody configurations and propulsion devices. Mar. Tech. 27, 325336.Google Scholar
Bohl, D. G. & Koochesfahani, M. F. 2009 MTV measurements of the vortical field in the wake of an airfoil oscillating at high reduced frequency. J. Fluid Mech. 620, 6388.CrossRefGoogle Scholar
Breslin, J. P. & Andersen, P. 1996 Hydrodynamics of Ship Propellers. Cambridge University Press.Google Scholar
Choutapalli, I. M., Alkislar, M. B., Krothapalli, A. & Lourenco, L. M. 2005 An experimental study of pulsed jet ejector. AIAA paper 2005-1208.CrossRefGoogle Scholar
Cox, B. D. & Reed, A. M. 1988 Contrarotating propellers: design theory and applications. In Proceedings of the Propellers '88 Symposium, pp. 15.1–15.29.Google Scholar
Dabiri, J. O. 2006 Note on the induced Lagrangian drift and added-mass of a vortex. J. Fluid Mech. 547, 105113.CrossRefGoogle Scholar
Dabiri, J. O. 2009 Optimal vortex formation as a unifying principle in biological propulsion. Annu. Rev. Fluid Mech. 41, 1733.CrossRefGoogle Scholar
Dabiri, J. O. & Gharib, M. 2004 Fluid entrainment by isolated vortex rings. J. Fluid Mech. 511, 311331.CrossRefGoogle Scholar
Gharib, M., Rambod, E. & Shariff, K. 1998 A universal time scale for vortex ring formation. J. Fluid Mech. 360, 121140.CrossRefGoogle Scholar
Glover, E. J. 1987 Propulsive devices for improved propulsive efficiency. Trans. Inst. Mar. Engrs 99, 2329.Google Scholar
Grim, O. 1980 Propeller and vane wheel. J. Ship Res. 24, 203226.CrossRefGoogle Scholar
Grothues-Spork, H. 1988 Bilge vortex control devices and their benefits for propulsion. Intl Shipbuilding Prog. 35, 183214.Google Scholar
Hadler, J. B. 1969 Contrarotating propeller propulsion: a state-of-the-art report. Mar. Tech. 6, 281289.Google Scholar
Hill, M. J. M. 1894 On a spherical vortex. Phil. Trans. R. Soc. Lond. A 185, 213245.Google Scholar
Hoerner, S. F. 1965 Fluid-Dynamic Drag. Hoerner Fluid Dynamics.Google Scholar
Houghton, E. L. & Carpenter, P. W. 2003 Aerodynamics. Elsevier.Google Scholar
Hussain, F. & Husain, H. S. 1989 Elliptic jets. Part 1. Characteristics of unexcited and excited jets. J. Fluid Mech. 208, 257320.CrossRefGoogle Scholar
Kanso, E., Marsden, J. E., Rowley, C. W. & Melli-Huber, J. B. 2005 Locomotion of articulated bodies in a perfect fluid. J. Nonlinear Sci. 15, 255289.CrossRefGoogle Scholar
Krieg, M. & Mohseni, K. 2008 Thrust characterization of a bioinspired vortex ring thruster for locomotion of underwater robots. IEEE J. Ocean. Engng 33, 123132.CrossRefGoogle Scholar
Krueger, P. S. 2001 The significance of vortex ring formation and nozzle exit over-pressure to pulsatile jet propulsion. PhD thesis, California Institute of Technology.Google Scholar
Krueger, P. S., Dabiri, J. O. & Gharib, M. 2006 The formation number of vortex rings formed in uniform background co-flow. J. Fluid Mech. 556, 147166.CrossRefGoogle Scholar
Krueger, P. S. & Gharib, M. 2003 The significance of vortex ring formation to the impulse and thrust of a starting jet. Phys. Fluids 15, 12711281.CrossRefGoogle Scholar
Krueger, P. S. & Gharib, M. 2005 Thrust augmentation and vortex ring evolution in a fully pulsed jet. AIAA J. 43, 792801.CrossRefGoogle Scholar
Linden, P. F. & Turner, J. S. 2004 ‘Optimal’ vortex rings and aquatic propulsion mechanisms. Proc. R. Soc. Lond. B 271, 647653.CrossRefGoogle ScholarPubMed
Lockwood, R. M. 1961 Interim summary report on investigation of the process of energy transfer from an intermittent jet to secondary fluid in an ejector-type thrust augmenter. Hiller Aircraft Rep. ARD-286.CrossRefGoogle Scholar
Maxworthy, T. 1972 The structure and stability of vortex rings. J. Fluid Mech. 51, 1532.CrossRefGoogle Scholar
Moslemi, A. A. & Krueger, P. S. 2010 Propulsive efficiency of a bio-inspired pulsed-jet underwater vehicle. Bioinspir. Biomim. 5, 036003.CrossRefGoogle Scholar
Narita, H., Yagi, H., Johnson, H. D. & Breves, L. R. 1981 Development and full-scale experiences of a novel integrated duct propeller. Trans. SNAME 89, 319346.Google Scholar
Norbury, J. 1973 A family of steady vortex rings. J. Fluid Mech. 57, 417431.CrossRefGoogle Scholar
Olcay, A. B. & Krueger, P. S. 2008 Measurement of ambient fluid entrainment during laminar vortex ring formation. Exp. Fluids 44, 235247.CrossRefGoogle Scholar
Paxson, D. E., Litke, P. J., Schauer, F. R., Bradley, R. P. & Hoke, J. L. 2006 Performance assessment of a large scale pulsejet-driven ejector system. NASA Tech. Memo. 2006-214224.CrossRefGoogle Scholar
Prandtl, L. 1952 Essentials of Fluid Dynamics. Hafner.Google Scholar
Prandtl, L. & Tietjens, O. G. 1934 Applied Hydro- and Aeromechanics. Dover.Google Scholar
Reynolds, W. C., Parekh, D. E., Juvet, P. J. D. & Lee, M. J. D. 2003 Bifurcating and blooming jets. Annu. Rev. Fluid Mech. 35, 295315.CrossRefGoogle Scholar
Sachs, A. H. & Burnell, J. A. 1962 Ducted propellers: a critical review of the state of the art. Prog. Aeronaut. Sci. 3, 85135.CrossRefGoogle Scholar
Saffman, P. G. 1992 Vortex Dynamics. Cambridge University Press.Google Scholar
Schlichting, H. & Gersten, K. 2000 Boundary-Layer Theory. Springer.CrossRefGoogle Scholar
Shadden, S. C., Dabiri, J. O. & Marsden, J. E. 2006 Lagrangian analysis of fluid transport in empirical vortex ring flows. Phys. Fluids 18, 047105.CrossRefGoogle Scholar
Stipa, L. 1931 Experiments with intubed propellers. NACA Tech. Rep. TM 655.Google Scholar
Williamson, C. H. K. 1996 Vortex dynamics in the cylinder wake. Annu. Rev. Fluid Mech. 28, 477539.CrossRefGoogle Scholar
Wu, T. Y. 1962 Flow through a heavily loaded actuator disc. Schiffstechnik 9, 134138.Google Scholar