Document Type : Research Article


PhD Student, Department of Aerospace Engineering, Sharif University of Technology ، Tehran،Iran


In this paper, we study and introduce the drag force reduction in flexible structures. Firstly, a review of the inspiration of this phenomenon by nature is presented, and thenthe amount of drag force reduction in the flexible structure is measured experimentally. The obtained results show that this reduction can be up to 50% of the total drag force. In addition, influential factors on this phenomenon have been investigated.


[1]Hassani, M., Elastic Reconfiguration of Bending and Twisting Rods in Air Flow, (PhD Thesis) École Polytechnique de Montréal, Montreal, Quebec, Canada, 2016.
[2]Bhatiy, A., Sawanniy, R., Kulkarni, K. and Bhardwaj, R., “Role of Skin Friction Drag during Flow-Induced Recon_guration of a Flexible Thin Plate”, Accepted for publication in Journal of Fluids and Structures, Dec 2017.
[3] Langre, E., Gutierrez, A. and Cossé, J., “On the Scaling of Drag Reduction by Reconfiguration in plants”, Comptes Rendus Mecanique, Vol. 340, 2012, pp. 35-40.
[4]Gosselin, F., De Langre, E. and Machado-Almeida, B., “Drag Reduction of Flexible Plates by Reconfiguration”, Journal of Fluid Mechanics, Cambridge University Press (CUP), Vol. 650, 2010, pp.319-341.
[5] Denny, M. and Gaylord, B., “The Mechanics of Wave-swept Algae”, Journal of Experimental Biology, Vol. 205, No. 10, 2002, pp. 1355-1362.
[6] Harder, D.L., Speck, O., Hurd, C.L. and Speck, T., “Reconfiguration as a Prerequisite for Survival in Highly Unstable Flow-dominated Habitats”, Journal of Plant Growth Regulation, Vol. 23, No. 2, 2004, pp. 98-107.
[7] de Langre, E., “Effects of wind on plants”, Annual Review of Fluid Mechanics, Vol. 40, 2008, pp. 141-168.
[8] Koizumi, A., Motoyama, J., Sawata, K., Sasaki, Y. and Hirai, T., “Evaluation of Drag Coefficients of Poplar-tree Crowns by a Field Test Method”, Journal of Wood Science, Vol. 56, No. 3, 2010, pp. 189-193.
[9]Gosselin, F. and de Langre, E., “Drag Reduction by Reconfiguration of a Poroelastic System”, Journal of Fluids and Structures, Vol. 27, 2011, pp. 1111-1123.
[10]Beeby, S.P., Tudor, M.J. and White, N.M., “Energy Harvesting Vibration Sources for Microsystems Applications”, Meas. Sci. Technol, Vol. 17, 2006, pp. 175–195.
[11]Weissenbock, N.M., Weiss, C.M., Schwammer, H.M. and Kratochvil, H. “Thermal Windows on the Body Surface of African Elephants (Loxodonta Africana) Studied by Infrared Thermography”, J. Therm. Biol., Vol. 35, No. 4, 2010, pp. 182–188.
[12]Mills, Z.G., Aziz, B. and Alexeev, A., “Beating Synthetic Cilia Enhance Heat Transport in Microfluidic Channels”, Soft Matter, Vol. 8, No. 45, 2012, pp. 11508–11513.
[13]De-langre, E., “Methodological Advances in Predicting Flow-induced Dynamics of Plants Using Mechanical-engineering Theory,” Journal of Experimental Biology, Vol. 215, No. 6, 2013, pp. 914–921.
[14]Leclercq, T., Peake, N. and de Langre, E. “Does Flutter Prevent Drag Reduction by Reconfiguration?”, Proceedings of The Royal Society A Mathematical Physical and Engineering Sciences, 474 (2209): 20170678 , January 2018.