Testing a Special Shaped Body of Revolution Similar to Dolphins Trunk





Wind tunnel tests, Drag reduction, Boundary layer separation, Flow visualization, Aquatic animals


Background. The high swimming velocities of some aquatic animals such as dolphins continue to attract great interest of researchers. The friction drag of the dolphin, estimated with the use of turbulent friction coefficient of the flat plate, was so high to declare that the dolphin should not be able to swim as fast as it does with the muscle power it possesses. Some previous tests of the rigid bodies, similar to the animal shapes, and gliding dolphins revealed the attached flow patterns. Nevertheless, the researchers connected with industrial applications believe that separation is inevitable on every smooth shape, provided no active boundary-layer control methods (e.g., suction) are applied.

Objective. The aim of the paper is to test a special shaped rigid body of revolution in the wind tunnel in order to show that the boundary-layer separation can be removed without any active flow control methods.

Methods. Wind tunnel tests were carried out at velocities 15, 35, and 55 m/s. Static pressure measurements and the oil-flow visualization were used. For this study, we take the UA-2 special shaped model of 200 mm length and 56.78 mm of the maximum diameter. The closed version of the UA-2c model is similar to the dolphin body. The tests were carried out in the subsonic wind tunnel MUB of the Institut für Strömungsmechanik (ISM) at Technische Universität Braunschweig, Germany. The wind tunnel MUB of ISM is an actively cooled Goettingen type tunnel with a square section of 1.3 m and the turbulence level of about 0.2 %. The technique of oil-flow visualization was used to deliver information of the surface near flow. The color used is a mixture of thin mineral oil and petrol, in an optimized ratio. The very fine titan-dioxide particles and UV-light reactive polymer particles in the color deliver a high contrast picture of the flow directions with a high spatial resolution.

Results. The distribution of the static pressure and the oil-flow visualization are presented at three angles of attack. The flow pattern at zero angle of attack is probably attached and laminar.

Conclusions. Pressure measurements and the flow visualization on the special shaped body of revolution showed that it is probably possible to avoid separation in rather large range of the Reynolds numbers. Further experiments are necessary with the use of a visualization of the flow volume and hot-wire velocity probes to clarify the behavior of the boundary layer, its separation and laminar-to-turbulent transition characteristics.

Author Biographies

Igor G. Nesteruk, Institute of Hydromechanics; Igor Sikorsky Kyiv Polytechnic Institute

Ігор Георгійович Нестерук

Markus Brühl, Braunschweig University of Technology

Маркус Брюль

Thorsten Moeller, Braunschweig University of Technology

Торстен Мьоллер


J. Gray, “Studies in animal locomotion VI. The propulsive powers of the dolphin”, J. Exp.Biol., vol. 13, pp. 192–199, 1936.

Yu.G. Aleyev, Nekton. Springer Netherlands, 1977. doi: 10.1007/978-94-010-1324-6

J. Rohr et al., “Experimental approaches towards interpreting dolphin stimulated bioluminescence”, J. Exper. Biol., vol. 201, pp. 1447–1460, 1998.

Underwater Missile Propulsion, L. Greiner, Ed. Compass Publications, 1967.

I. Nesteruk, “Reserves of the hydrodynamical drag reduction for axisymmetric bodies”, Bulletin of Univ. of Kiev, Ser.: Phys. & Math., no. 4, pp. 112–118, 2002.

I. Nesteruk et al., “Shape of aquatic animals and their swimming efficiency”, J. Marine Biol., vol. 2014, Article ID 470715, 2014. doi: 10.1155/2014/470715

R.J. Hansen and J.G. Hoyt, “Laminar-to-turbulent transition on a body of revolution with an extended favorable pressure gradient forebody”, J. Fluids Eng., vol. 106, pp. 202–210, 1984. doi:10.1115/1.3243103

J.S. Parsons et al., “Shaping of axisymmetric bodies for minimum drag in incompressible flow”, J. Hydronautics, vol. 8, no. 3, pp. 100–107, 1974. doi: 10.2514/3.48131

S.S. Dodbele et al., “Shaping of airplane fuselages for minimum drag”, J. Aircraft, vol. 24, pp. 298–304, 1987. doi: 10.2514/3.45444

M.F. Zedan et al., “Drag reduction of fuselages through shaping by the inverse method”, J. Aircraft, vol. 31, no. 2, pp. 279–287, 1994. doi: 10.2514/3.46485

Th. Lutz and S. Wagner, “Drag reduction and shape optimization of airship bodies”, J. Aircraft, vol. 35, no. 3, pp. 345–351, 1998. doi: 10.2514/2.2313

I. Nesteruk, “Peculiarities of turbulization and separation of boundary-layer on slender axisymmetric subsonic bodies”, Naukovi Visti NTUU KPI, no. 3, pp. 70–76, 2002 (in Ukrainian).

I. Nesteruk, “Rigid bodies without boundary-layer separation”, Int. J. Fluid Mech. Res., vol. 41, no. 3, pp. 260–281, 2014. doi: 10.1615/InterJFluidMechRes.v41.i3.50

I. Nesteruk, “New type of unseparated subsonic shape of axisymmetric body”, Reports of the National Academy of Sciences of Ukraine, no. 11, pp. 49–56, 2003.

F.R. Goldschmied, “Integrated hull design, boundary layer control and propulsion of submerged bodies: Wind tunnel verification”, in Proc. AIAA/SAE/ASME 18th Joint Propulsion Conf. (AIAA (82-1204)), pp. 3–18, 1982. doi: 10.2514/6.1982-1204

P. Polivanov et al., “Effects of local wall heating and cooling on hypersonic boundary-layer stability”, in Proc. SFBTRR40 Summer Research Program, Munich (2011), 17 p.

J. Becker et al., “The future role of smart structure systems in modern aircraft”, J. Smart Structures and Systems, vol. 1, no. 2, pp. 159–185, 2005.

K.-S. Choi et al., “Turbulent boundary-layer control with plasma actuators”, Ph. Trans. Royal Soc. A, vol. 369, pp. 1443–1458, 2011. doi: 10.1098/rsta.2010.0362

J.H.M. Fransson et al., “Delaying transition to turbulence by a passive mechanism”, Phys. Rev. Lett., vol. 96, no. 064501, 2006. doi: 10.1103/PhysRevLett.96.064501

I. Nesteruk, “Technology applications of the low drag shapes of aquatic animals”, Biosci. Bioeng., vol. 1, no. 2, pp. 29–33, 2015.

L.G. Loitsyanskiy, Mechanics of Liquids and Gases, 6th ed. New York, Wallingford: Begell House, 1995.