Rinku Mukherjee

This paper uses a numerical post-stall predictive tool based on ‘decambering’ approach to study the aerodynamic characteristics of a lead-trail formation in pre and post-stall flow conditions. A basic lead-trail formation consisting of 2 wings and an extended formation consisting of 5 wings are studied with a view to the possibility of fuel savings, increase in range of operation, delayed flow separation and efficient positioning of the wings with respect to each other. Whether increasing the number of wings in a configuration is more useful is also looked into. The optimum operational angles of attack for maximum advantage in terms of fuel efficiency of all wings is studied including post-stall angles of attack. Numerical results for CL, CDi, section Cl distribution and their dependence on vertical offsets and angle of attack are reported.

In this paper, a novel decambering technique has been implemented using a vortex lattice method to study the effects of wing twist on the induced drag of individual lifting surfaces in configuration flight including post-stall angles of attack. The effect of both geometric and aerodynamic twist is studied. In the present work, 2D data of NACA0012 airfoil from XFoil at Re=1×106 is used to predict 3D post-stall data using geometric twist for a single wing and compared with literature. The effect of aerodynamic twist is implemented by using different airfoils along wing–span and the resulting wing CL–α and Cdi–α are compared with experiment. Study of wings of different aspect ratios with & without aerodynamic twist on both leading and trailing wings helps to understand the effect of twist on the lift and induced drag when they are varied on both wings simultaneously and individually.

A vortex-lattice numerical scheme that uses a novel decambering technique to predict post-stall aerodynamic characteristics is used to study the aerodynamics of tandem Cessna 172 aircrafts flying in echelon formation. Results like CL- α from the current method are compared with experiment. Additional results like section Cldistributions over wing spans, CM- α and CLW- αtw(i.e. CLof the leading aircraft for different angles of attack of the trailing aircraft) and analysis for (-) ve y-offset, which are available only from the current numerical method are reported that supplement the experimental results. Detailed post-stall numerical analysis and the effect of chord-wise, span-wise and vertical offsets on the aerodynamics of the formation are also reported.

In this paper, numerical analysis is conducted using a local camber correction approach called “decambering” to predict pre and post-stall aerodynamic characteristics of multiple lifting surfaces operating in formation. A three wings Chevron formation and five and nine wings V-formation are studied. NACA2412 wing section is used and experimental validation is provided with Cessna 172 aircrafts flying in Chevron formation. Effect of wing incidence and shifting of stall angles is looked at along with changes in geometric offsets between the wings in formation. The spanwise distribution of coefficients of lift and induced drag at different angles of attack, including high and post-stall angles of attack is studied for all the wings. The span efficiency factor, which represents the correction in drag due to change in lift as compared to that of an ideal wing of the same aspect ratio but with elliptical lift distribution is calculated. The maximum possible efficiency is then used to estimate the maximum reduction in drag possible for individual wings in different formations. The change in efficiency with number of lifting surfaces in a formation is also estimated.

A vortex-lattice numerical scheme that uses a novel decambering technique to predict post-stall aerodynamic characteristics is used to study the aerodynamics of tandem Cessna 172 aircrafts flflying in echelon formation. Results like CL -α from the current method are compared with experiment. Additional results like section Cl distributions over wing spans, CM - α and CLW αtw (i.e. CL of the leading aircraft for diαerent angles of attack of the trailing aircraft) and analysis for (-)ve y-oαset, which are available only from the current numerical method are reported that supplement the experimental results. Detailed post-stall numerical analysis and the eαect of chord-wise, span-wise and vertical oαsets on the aerodynamics of the formation are also reported.

In this paper, a novel decambering technique has been implemented using a vortexlattice method to study the effects of wing twist on the induced drag of individual lifting surfaces in congurationight. The effects of both geometric and aerodynamic twist arestudied. 2D Cl−α and Cm−α from XFoil at Re = 1×106for NACA0012 airfoil is used as inputto predict 3D post-stall aerodynamic characteristics for a single wing with geometric twistand compared with literature. Aerodynamic twist is implemented by using dierent airfoilsalong wing-span and wing CL−α and Cdi−α aare compared with experiment. The effect ofasymmetric aerodynamic twist on the leading wing shows distinct changes in the span-wisedistribution of Cland Cdion the trailing wing and throws up interesting inferences aboutformation ight aerodynamics.