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Indian Institute of Science

1. Theerthamalai, P. Aerodynamic Analysis Of Grid Fins Using Analytical And Computational Methods.

Degree: 2007, Indian Institute of Science

Grid fins (lattice fins) are used as a lifting and control surface for highly manoeuvrable missiles. Grid fins also find their applications for air-launched submunitions. The main advantages are its low hinge moment requirement and good high angle of attack performance characteristics. Two dimensional analysis has been carried out using linear and shock-expansion theo- ries. The results indicate that above certain depth-to-height ratio, (called critical depth-to-height ratio,) the local normal force becomes negative due to shock reflection from the opposite side. Hence, depth (chord) for grid fin cell should not exceed a critical value. A prediction method has been developed for the estimation of aerodynamic character- istics of grid fin-body combinations at supersonic Mach numbers based on shock-expansion theory. Body upwash theory has been used for the effect of body; method of images has been used for carry-over forces onto the body. Empirical relation has been used for the modelling of separated body vortices and their effect on the leeward side fins. The method has been validated with experimental results for three configurations. The comparison is good for individual fin characteristics as well as overall characteristics for all the cases at higher supersonic Mach numbers. For lower supersonic Mach numbers at higher angles of attack, the prediction deviates from experiment. The reason for the deviation is due to shock detachment and shock reflection from opposite side, which is not modelled in the present method. Vortex lattice method has been used for prediction of linear aerodynamic character- istics of grid-fins at subsonic Mach numbers. Empirical relation based on trends from available experimental data has been used for the non-linear effect. The method has been validated with experimental results for several configurations without and with control surface deflections. The predicted aerodynamic characteristics compare well with experimental results for all the cases and the difference is within 15%. Based on the subsonic and supersonic analytical methods, a prediction code for the aerodynamic analysis of configuration with grid fins has been developed. Flow field computations inside isolated cells have been carried out using CFD code, PARAS-3D. Effects of depth-to-height ratio, web thickness, web leading edge angle and cell width-to-height ratio have been studied. Increase in thickness reduces the critical depth and increases the normal force. This increment in normal force is due to shock wave formation at the expansion side and its interaction with the opposite side. Effect of cell cross sectional shape has been studied using inviscid computation over isolated cells. Square, right triangular, equilateral triangular and hexagonal cross sections have been considered for this study. The normal force for square cell at zero roll is higher compared to 45 deg roll (diamond shape). Triangular cells show large variation in normal force with roll orientation due to large variation in projected area with… Advisors/Committee Members: Balakrishnan, N.

Subjects/Keywords: Aerodynamics - Data Processing; Grid Fins; Supersonic Flows; Subsonic Flows; Grid Fin Aerodynamics; Grid Fin Cell Geometry; Lattice Fins; Isolated Cells; Grid-Fin Configuration; Supersonic Speeds; Subsonic Speeds; Grid Fin Cells; Aeronautics

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APA (6th Edition):

Theerthamalai, P. (2007). Aerodynamic Analysis Of Grid Fins Using Analytical And Computational Methods. (Thesis). Indian Institute of Science. Retrieved from http://hdl.handle.net/2005/563

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Theerthamalai, P. “Aerodynamic Analysis Of Grid Fins Using Analytical And Computational Methods.” 2007. Thesis, Indian Institute of Science. Accessed July 22, 2019. http://hdl.handle.net/2005/563.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Theerthamalai, P. “Aerodynamic Analysis Of Grid Fins Using Analytical And Computational Methods.” 2007. Web. 22 Jul 2019.

Vancouver:

Theerthamalai P. Aerodynamic Analysis Of Grid Fins Using Analytical And Computational Methods. [Internet] [Thesis]. Indian Institute of Science; 2007. [cited 2019 Jul 22]. Available from: http://hdl.handle.net/2005/563.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Theerthamalai P. Aerodynamic Analysis Of Grid Fins Using Analytical And Computational Methods. [Thesis]. Indian Institute of Science; 2007. Available from: http://hdl.handle.net/2005/563

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

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