Numerical simulation of thrust generating flow past a pitching airfoil Sunetra Sarkar, Kartik Venkatraman * Department of Aerospace Engineering, Indian Institute of Science, Bangalore 560012, India Received 19 May 2004; received in revised form 4 October 2004; accepted 18 October 2004 Available online 19 February 2005 Abstract Earlier analytical and experimental studies predict that pitching motions at high frequency can generate thrust on the airfoil. The present work is an effort towards a systematic understanding of the influence of various parameters on thrust generation from a harmonically pitching airfoil. Quantitative instantaneous force computations have been discussed together with qualitative vortex patterns using a 2-D discrete vor- tex simulation of incompressible viscous flow. In general, thrust force increases with the oscillation fre- quency. The trend is very similar to the inviscid theory prediction. Further, the thrust force is seen to decrease with the increase in mean angle of attack. However, in a clear deviation from inviscid theory trends, pitching at high amplitudes about high mean angle of attack, only drag is observed for high values of reduced frequency considered. The effect of location of the pitching axis is also found to be significant on the propulsive characteristics of the airfoil. Ó 2005 Elsevier Ltd. All rights reserved. 1. Introduction The generation of lift and thrust due to the oscillation of lifting surfaces at high frequency is common in many flying and aquatic animals. In recent years many thrust generating devices 0045-7930/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.compfluid.2004.10.002 * Corresponding author. Tel.: +91 80 2293 2874; fax: +91 80 2360 0134. E-mail address: kartik@aero.iisc.ernet.in (K. Venkatraman). URL: http://aero.iisc.ernet.in/aselab/ (K. Venkatraman). www.elsevier.com/locate/compfluid Computers & Fluids 35 (2006) 16–42