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Reynolds number and slant angle effects on the flow over a slanted cylinder afterbody

Published online by Cambridge University Press:  21 April 2020

Fernando Zigunov Open the ORCID record for Fernando Zigunov [Opens in a new window] ,
Prabu Sellappan Open the ORCID record for Prabu Sellappan [Opens in a new window]  and
Farrukh Alvi
Fernando Zigunov*
Affiliation:
Department of Mechanical Engineering, FAMU-FSU College of Engineering,The Florida State University, Tallahassee, FL, USA
Prabu Sellappan
Affiliation:
Department of Mechanical Engineering, FAMU-FSU College of Engineering,The Florida State University, Tallahassee, FL, USA
Farrukh Alvi
Affiliation:
Department of Mechanical Engineering, FAMU-FSU College of Engineering,The Florida State University, Tallahassee, FL, USA
*
†Email address for correspondence: [email protected]
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Abstract

The cylinder with a slanted base is a simplified, canonical bluff body geometry that shares similarities to aircraft fuselages, which are known to produce a strong vortex pair due to their upswept afterbody. This work will examine in detail the surface flow and near-field characteristics of the flow over the slanted cylinder for slant angles of $20^{\circ }$, $32^{\circ }$ and $45^{\circ }$ with spatially dense measurements. Principal flow features of the mean flow field are identified, showing the connection between the main counter-rotating vortex pair observed in the wake and the separation bubble observed at the leading edge of the slant. A full reconstruction of the three-dimensional mean flow field using stacked stereoscopic particle image velocimetry reveals intricate details of this flow and clearly shows the direct connection between the two features. To our knowledge, this is the first direct measurement of the full three-dimensional flow topology for this geometry. The separation bubble length is found to be directly proportional to the slant angle and inversely proportional to the Reynolds number. Furthermore, the circulation within the primary vortex pair increases with increasing slant angle. This strengthening of the vortices is correlated to the form drag of this body in the vortex-dominated regime. A bi-stable steady-state wake is also observed in this flow at a low Reynolds number for the slant angle of $45^{\circ }$, where the formation of either a separated wake flow state or a vortex-dominated flow state is dependent upon initial conditions, i.e. the presence of overshoot of the free-stream velocity during wind tunnel start-up.

JFM classification

Vortex Flows: Vortex interactions Wakes/Jets: Wakes
Type
JFM Papers
Information
Journal of Fluid Mechanics , Volume 893 , 25 June 2020 , A11
Copyright
© The Author(s), 2020. Published by Cambridge University Press

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References

Ahmed, S. R., Ramm, G. & Faltin, G.1984 Some salient features of the time-averaged ground vehicle wake, Tech. Rep. SAE Technical Paper.CrossRefGoogle Scholar
Bergeron, K., Hayes, M., Aronoff, J. & Charles, R.2009 C-17 low speed wind tunnel wake-vortex study. AIAA Paper 2009–1482.CrossRefGoogle Scholar
Britcher, C. P. & Alcorn, C. W. 1991 Interference-free measurements of the subsonic aerodynamics of slanted-base ogive cylinders. AIAA J. 29 (4), 520–525.CrossRefGoogle Scholar
Bulathsinghala, D., Wang, Z. & Gursul, I. 2016 Effect of upsweep angle on afterbody vortices. In 46th AIAA Fluid Dynamics Conference, pp. 1–25.Google Scholar
Bulathsinghala, D., Wang, Z. & Gursul, I. 2019 Modified near-wakes of axisymmetric cylinders with slanted base. Aerosp. Sci. Technol.CrossRefGoogle Scholar
Bulathsinghala, D. S., Jackson, R., Wang, Z. & Gursul, I. 2017 Afterbody vortices of axisymmetric cylinders with a slanted base. Exp. Fluids 58 (5), 1–24.Google Scholar
Bury, Y., Jardin, T. & Klöckner, A. 2013 Experimental investigation of the vortical activity in the close wake of a simplified military transport aircraft. Exp. Fluids 54 (5), 1524.Google Scholar
Crow, S. 1970 Stability theory for a pair of trailing vortices. AIAA J. 8, 2172–2179.CrossRefGoogle Scholar
Epstein, R. J., Carbonaro, M. C. & Caudron, F. 1994 Experimental investigation of the flowfield about an upswept afterbody. J. Aircraft 31 (6), 1281–1290.CrossRefGoogle Scholar
Garmann, D. J. & Visbal, M. R. 2019 High-fidelity simulations of afterbody vortex flows. AIAA J. 57 (9), 3980–3990.CrossRefGoogle Scholar
Hunt, J. C., Wray, A. A. & Moin, P. 1988 Eddies, streams, and convergence zones in turbulent flows. In Proc. 1988 Summer Program Cent. Turbul. Res., pp. 193–207. Center for Turbulence Research, Stanford, CA.Google Scholar
Johnson, W., Trickey, C., Forsythe, J., Albertson, J. & Leigh, E. 2002 Experimental and computational investigation of the flow behind a C-130 with tailgate down. In 40th AIAA Aerospace Sciences Meeting and Exhibit, Reno, NV.Google Scholar
Morel, T. 1978 The Effect of Base Slant on the Flow Pattern and Drag of Three-Dimensional Bodies with Blunt Ends. Springer.CrossRefGoogle Scholar
Morel, T. 1980 Effect of base slant on flow in the near wake of an axisymmetric cylinder. Aeronaut. J. 31 (2), 132–147.CrossRefGoogle Scholar
Neal, D., Sciacchitano, A., Smith, B. & Scarano, F. 2015 Collaborative framework for piv uncertainty quantification: the experimental database. Meas. Sci. Technol. 26 (7), 074003.CrossRefGoogle Scholar
Rossitto, G., Sicot, C., Ferrand, V., Borée, J. & Harambat, F. 2017 Aerodynamic performances of rounded fastback vehicle. Proc. Inst. Mech. Engrs D 231 (9), 1211–1221.CrossRefGoogle Scholar
Rossitto, G., Sicot, C., Ferrand, Vérie, Borée, J. & Harambat, F. 2016 Influence of afterbody rounding on the pressure distribution over a fastback vehicle. Exp. Fluids 57 (3), 43.CrossRefGoogle Scholar
Sellappan, P., McNally, J. & Alvi, F. S. 2018 Time-averaged three-dimensional flow topology in the wake of a simplified car model using volumetric PIV. Exp. Fluids 59 (8), 124.CrossRefGoogle Scholar
Wieneke, B. 2015 PIV uncertainty quantification from correlation statistics. Meas. Sci. Technol. 26 (7), 074002.CrossRefGoogle Scholar
Wortman, A. 1999 Reduction of fuselage form drag by vortex flows. J. Aircraft 36 (3), 501.CrossRefGoogle Scholar
Xia, X. & Bearman, P. 1983 An experimental investigation of the wake of an axisymmetric body with a slanted base. Aeronaut. Q. 34 (1), 24–45.CrossRefGoogle Scholar
Zhang, B. F., Zhou, Y. & To, S. 2015 Unsteady flow structures around a high-drag Ahmed body. J. Fluid Mech. 777, 291–326.CrossRefGoogle Scholar

Zigunov et al. supplementary movie 1

Time-lapse of surface oil flow development for ɸ=32º and ReD=5×105.

Download Zigunov et al. supplementary movie 1(Video)
Video 7.1 MB

Zigunov et al. supplementary movie 2

Time-lapse of surface oil flow development for ɸ=20º and ReD=5×105. Detail view highlights small reversed flow region inside separation bubble.

Download Zigunov et al. supplementary movie 2(Video)
Video 6.9 MB

Zigunov et al. supplementary movie 3

Time-lapse of surface oil flow development for ɸ=45º and ReD=5×105.

Download Zigunov et al. supplementary movie 3(Video)
Video 5 MB