Abstract
Experiments were performed to investigate the effects of amplitude and depth on the drag reduction of a NACA 0012 airfoil plunging near a free surface for a range of frequencies. Beyond the effect of the free surface, at low Strouhal numbers based on amplitude, Sr A, the drag reduction follows a parabolic trend with greater effect for greater amplitude, similar to the Garrick predictions. At Sr A ≈ 0.08, larger amplitudes break from this trend due to leading-edge vortex formation. As a result, smaller amplitudes become preferable for Sr A > 0.12. In addition, for the first time, vortex lock-in is documented experimentally. The effect of depth is twofold; firstly with decreasing depth, there is a general departure from the Garrick trends. Secondly, a reduction in thrust is observed around a constant unsteady parameter of τ = U ∞ 2πf/g ≈ 0.25; around this value significant free-surface waves form that detract from thrust creation. For depths greater than two chord lengths, there is negligible free-surface effect.
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Abbreviations
- a :
-
Amplitude of plunging motion
- A :
-
Peak-to-peak amplitude of plunging motion
- C d :
-
Time-averaged drag coefficient
- C d0 :
-
Time-averaged drag coefficient for the stationary foil
- c :
-
Chord length
- d :
-
Depth
- f :
-
Frequency
- h :
-
Foil position
- Fr :
-
Froude number, \( U_{\infty } /\sqrt {gc} \)
- Re :
-
Reynolds number, ρU ∞ c/μ
- Sr c :
-
Strouhal number based on chord, fc/U ∞
- Sr A :
-
Strouhal number based on amplitude, 2fa/U ∞
- t :
-
Time t = 0 is top of motion
- T :
-
Plunge period
- U ∞ :
-
Freestream velocity
- α :
-
Angle of attack
- λ w :
-
Wavelength of water wave
- μ :
-
Viscosity
- ρ :
-
Density
- τ:
-
Unsteady parameter, U ∞ 2πf/g
References
Anderson JM, Streitlien K, Barrett DS, Triantafyllou MS (1998) Oscillating foils of high propulsive efficiency. J Fluid Mech 360:41–72
Baik YS, Bernal LP, Granlund K, Ol MV (2012) Unsteady force generation and vortex dynamics of pitching and plunging aerofoils. J Fluid Mech 709:37–68. doi:10.1017/jfm.2012.318
Barrett DS, Triantafyllou MS, Yue DKP, Grosenbaugh MA, Wolfgang MJ (1999) Drag reduction in fish-like locomotion. J Fluid Mech 392:183–212
Belden J, Techet AH (2011) Simultaneous quantitative flow measurement using PIV on both sides of the air-water interface for breaking waves. Exp Fluids 50:149–161. doi:10.1007/s00348-010-0901-5
Calderon DE, Wang Z, Gursul I (2010) Lift enhancement of a rectangular wing undergoing a small amplitude plunging motion, AIAA 2010-386. 48th AIAA Aerospace Sciences meeting including the new horizons forum and Aerospace exposition, Orlando, Florida
Ceccio SL (2010) Friction drag reduction of external flows with bubble and gas injection. Annu Rev Fluid Mech 42:183–203
Cleaver DJ, Wang Z, Gursul I (2011) Lift enhancement by means of small amplitude airfoil oscillations at low Reynolds numbers. AIAA J 49:2018–2033
Cleaver DJ, Wang Z, Gursul I (2012) Bifurcating flows of plunging airfoils at high Strouhal numbers. J Fluid Mech 708:349–376
Dabiri D, Gharib M (1997) Experimental investigation of the vorticity generation within a spilling water wave. J Fluid Mech 330:113–139. doi:10.1017/s0022112096003692
De Silva L, Yamaguchi H (2012) Numerical study on active wave devouring propulsion. J Mar Sci Technol 1–15. doi:10.1007/s00773-012-0169-y
Frampton KD, Goldfarb M, Monopoli D, Cveticanin D (2000) Passive aeroelastic tailoring for optimal flapping wings. In: Proceedings of conference on fixed, flapping and rotary wing vehicles at very low Reynolds numbers, 5–7 June 2000, Notre Dame, USA
Garrick IE (1936) Propulsion of a flapping and oscillating airfoil. NACA report No. 567
Grue J, Palm E (1985) Wave radiation and wave diffraction from a submerged body in a uniform current. J Fluid Mech 151:257–278
Grue J, Mo A, Palm E (1988) Propulsion of a foil moving in water-waves. J Fluid Mech 186:393–417. doi:10.1017/s0022112088000205
Heathcote S (2006) Flexible flapping airfoil propulsion at low Reynolds numbers. University of Bath, Phd Dissertation
Heathcote S, Gursul I (2007) Flexible flapping airfoil propulsion at low Reynolds numbers. AIAA J 45:1066–1079
Heathcote S, Wang Z, Gursul I (2008) Effect of spanwise flexibility on flapping wing propulsion. J Fluids Struct 24:183–199. doi:10.1016/jjfluidstructs.2007.08.003
Huang RF, Lee HW (2000) Turbulence effect on frequency characteristics of unsteady motions in wake of wing. AIAA J 38:87–94
Huang RF, Lin CL (1995) Vortex shedding and shear-layer instability of wing at low-Reynolds numbers. AIAA J 33:1398–1403
Jones KD, Dohring CM, Platzer MF (1998) Experimental and computational investigation of the Knoller-Betz effect. AIAA J 36:1240–1246
Koochesfahani MM (1989) Vortical patterns in the wake of an oscillating airfoil. AIAA J 27:1200–1205
Lin JC, Rockwell D (1995) Evolution of a quasi-steady breaking wave. J Fluid Mech 302:29–44. doi:10.1017/s0022112095003995
McCormic ME, Bhattach R (1973) Drag reduction of a submersible hull by electrolysis. Nav Eng J 85:11–16
McGowan GZ, Granlund K, Ol MV, Gopalarathnam A, Edwards JR (2011) Investigations of lift-based pitch-plunge equivalence for airfoils at low Reynolds numbers. AIAA J 49:1511–1524. doi:10.2514/1.j050924
Michell JH (1893) The highest waves in water. Philos Mag Ser 5(36):430–437
Moffat RJ (1985) Using uncertainty analysis in the planning of an experiment. J Fluids Eng Trans ASME 107:173–178
Naito S, Isshiki H (2005) Effect of bow wings on ship propulsion and motions. Appl Mech Rev 58:253–268
Palm E, Grue J (1999) On the wave field due to a moving body performing oscillations in the vicinity of the critical frequency. J Eng Math 35:219–232
Pan YL, Dong XX, Zhu Q, Yue DKP (2012) Boundary-element method for the prediction of performance of flapping foils with leading-edge separation. J Fluid Mech 698:446–467. doi:10.1017/jfm.2012.119
Pierson WJ, Moskowitz L (1964) A proposed spectral form for fully developed wind seas based on the similarity theory of S.A. Kitaigorodskii. J Geophys Res 69:5181–5190
Reichl P, Hourigan K, Thompson MC (2005) Flow past a cylinder close to a free surface. J Fluid Mech 533:269–296. doi:10.1017/s0022112005004209
Shen XC, Ceccio SL, Perlin M (2006) Influence of bubble size on micro-bubble drag reduction. Exp Fluids 41:415–424. doi:10.1007/s00348-006-0169-y
Tsuji Y, Nagata Y (1973) Stokes’ expansion of internal deep water waves to the fifth order. J Oceanogr 29:61–69. doi:10.1007/bf02109505
Tuncer IH, Kaya M (2005) Optimization of flapping airfoils for maximum thrust and propulsive efficiency. AIAA J 43:2329–2336
Tuncer IH, Walz R, Platzer MF (1998) A computational study on the dynamic stall of a flapping airfoil. AIAA paper 98-2519. 16th AIAA applied aerodynamics conference, June 15–18, 1998, Albuquerque
Visbal MR (2009) High-fidelity simulation of transitional flows past a plunging airfoil. AIAA J 47:2685–2697. doi:10.2514/1.43038
Winkel ES, Oweis GF, Vanapalli SA, Dowling DR, Perlin M, Solomon MJ, Ceccio SL (2009) High-Reynolds-number turbulent boundary layer friction drag reduction from wall-injected polymer solutions. J Fluid Mech 621:259–288. doi:10.1017/s0022112008004874
Young J, Lai JCS (2004) Oscillation frequency and amplitude effects on the wake of a plunging airfoil. AIAA J 42:2042–2052
Young J, Lai JCS (2007a) Mechanisms influencing the efficiency of oscillating airfoil propulsion. AIAA J 45:1695–1702. doi:10.2514/1.27628
Young J, Lai JCS (2007b) Vortex lock-in phenomenon in the wake of a plunging airfoil. AIAA J 45:485–490. doi:10.2514/1.23594
Zhu Q, Liu Y, Yue D (2006) Dynamics of a three-dimensional oscillating foil near the free surface. AIAA J 44:2997–3009
Acknowledgments
The authors would like to acknowledge the support from the Department of the Navy Grant N62909-10-1-7117 issued by the Office of Naval Research Global.
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Cleaver, D.J., Calderon, D.E., Wang, Z. et al. Periodically plunging foil near a free surface. Exp Fluids 54, 1491 (2013). https://doi.org/10.1007/s00348-013-1491-9
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DOI: https://doi.org/10.1007/s00348-013-1491-9