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Numerical Investigation of the Effects of Geometric Parameters and Impulsive Flow on Thrust Vectoring of an ACHEON Nozzle in Compressible Turbulent Flow

Nayebi, Alireza | 2024

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 58281 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Taeibi Rahni, Mohammad
  7. Abstract:
  8. Achieving effective thrust vectoring to improve aircraft maneuverability, particularly during vertical takeoff and landing (VTOL), has remained a critical challenge in aerospace engineering. This study investigates the ACHEON nozzle, a fluidic thrust vectoring system that utilizes the Coanda effect. Previous studies have largely overlooked key aerodynamic and geometric parameters influencing thrust vectoring, such as total mass flow rate, septum position, and geometric ratios of three-dimensional nozzles. Additionally, critical phenomena, including compressibility effects, shock wave formation, and choking regions have received limited attention. Furthermore, most previous research has concentrated on turbulent flows under stationary condition and neglecting the impact of impulsive flow control methods in this nozzle configuration. In this research, a comprehensive numerical investigation was carried out to evaluate the interactions among geometric, aerodynamic, and impulsive jet factors. The key parameters, including total mass flow rate, Reynolds number, septum position (relative to the nozzle throat), and width-to-throat height ratios of three-dimensional nozzles, were systematically analyzed. Impulsive jets were applied at various effective frequencies under non-stationary flow conditions to assess their effects on the nozzle's response time, flow structure, and thrust vectoring performance. The study employed the Favre-averaged Navier-Stokes equations to model compressible, turbulent, and three-dimensional flow, which were numerically solved using the standard k-ε turbulence model. A pressure-based finite volume method was implemented with structured and hybrid computational grids, and grid independence and validation studies were performed to ensure the accuracy of the numerical results. The study identified the effects of aerodynamic and geometric factors on flow structure and thrust vectoring, leading to the determination of an optimal geometric ratio for three-dimensional nozzles. The results reveal a strong dependency of thrust vectoring on total mass flow rate, septum position, and Reynolds number. Additionally, specific total mass flow rates and septum positions lead to the formation of shock waves, which have a significant impact on thrust vectoring. The study further identifies the effective frequency range for applying impulsive jets, highlighting that the response time of the ACHEON nozzle can be significantly reduced. Notably, an inverse correlation between impulsive jet frequency and thrust vectoring fluctuation amplitude is observed. These findings highlight the potential of impulsive flow within a specific frequency range to substantially improve nozzle performance. The findings offer valuable insights for optimizing the design of Coanda-based nozzles in advanced propulsion systems, particularly for applications in unmanned aerial vehicles (UAVs)
  9. Keywords:
  10. Coanda-Effect Air Vehicle ; Thrust Vectoring Control System (TVCS) ; Turbulent Flow ; Compressible Flow ; Impulsive Flow ; ACHEON Nozzle

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