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Numerical and Experimental Study of Induced Drag Reduction Using a Wing Grid at Low Reynolds Numbers

Sadeghi Malek Abadi, Mahyar | 2019

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52000 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Soltani, Mohamad Reza; Banazadeh, Afshin; Farahani, Mohammad
  7. Abstract:
  8. Wing grids are among devices used for increasing wing performance. Wing grids decrease wing induced drag by breaking the wing main tip vortex to smaller vortices with lower turbulence intensity value. These devices are mostly used in low Reynolds regimes, and their effectiveness decreases as the Reynolds number increases. In most researches around the world, wing grids have simple design configurations, but in this research wing grids are designed in such a way that each grid has a minimum value of induced drag respectively. So, in addition to reducing baseline wing induced drag by breaking the main vortex to smaller vortices by means of wing grid, each grid has a minimum value of induced drag itself. There are lots of parameters associated with wing grid configurations. Taper ratio, aspect ratio, twist, sweep angle, and dihedral angle are among the most important factors. In this research wing grid taper ratio, aspect ratio, and twist are designed for minimum induced drag. Subsequently, two important parameters such as wing grid dihedral angle and sweep angle are investigated numerically. Wing grid dihedral angle decreases induced drag by increasing the space between separate tip vortices and prevents them from superposition. On the other hand, dihedral angle distribution should be in such a way to effectively increase the lift to drag ratio of the baseline wing. To put it another way, excess increase in dihedral angle is deficient to wing overall performance. In this research, a dihedral angle distribution with a 20° dihedral angle for the first grid, declining with a constant rate to a value of -20° for the last grid. Sweep angle distribution is another parameter which is investigated in the aforementioned optimized dihedral angle distribution. Firstly, each grid span is decreased from first grid to final grid with a constant rate. With increasing grid sweep angles, the lift to drag ratio is increased by 15%. Secondly, the sweep angle is defined from the grid in the middle, decreasing grid span, marching to the wing leading edge and trailing edge. With this configuration, as the grids’ area is increased and similar to elliptic wing tip distribution, wing performance is increased by almost 50%
  9. Keywords:
  10. Winggrid ; Wing Tip Vortex ; Induced Drag ; Dihedral Angle ; Sweep Angle

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