Date

2018

Document Type

Thesis

Degree

Master of Science

Department

Mechanical Engineering

First Adviser

Oztekin, Alparslan

Abstract

Computational fluid dynamics simulations of supersonic flows through perforated and non-perforated nozzles are conducted. The primary objective of this thesis is to examine the influence of perforations in the convergent section of the nozzle on the spatial and temporal characteristics of the supersonic flows inside and outside the nozzle. The perforated nozzle might be utilized as supersonic inlet diffuser for high-speed flight engines, like ramjet, to reduce huge total pressure loss at starting process. The nozzle design is crucial for overall design of these systems, and the solution investigated here enjoys a high degree of interest for over 50 years.Open source CFD tool OpenFoam is used in this research. Two compressible solvers named the sonicFoam and rhoCentralFoam are introduced and used. To validate the mathematical model and numerical methods, simulations are conducted for supersonic flows over 23 degree wedge at Mach number 1.5 and flow over 2.86 degree wedge at Mach number 1.6. The pressure and velocity field and the characteristics of the oblique shock are determined and are compared against the results of the analytical solution. The predicted and analytical solution for the location and the pressure ratio matches well; validating the mathematical model and the numerical method employed. Simulations for supersonic flows through non-perforated and perforated nozzle are performed for a range of Mach number from 1.2 to 2.0. The total pressure is set to the same value for all simulations. Discretization is made using the sonicFoam and rhoCentralFoam solver. In order to characterize the flow images of the velocity field are presented for various values of Mach number. It is demonstrated that the bow shock is moved into the nozzle or is swallowed by the nozzle in the perforated nozzle geometry when incoming flow Mach number exceeds 1.8. The comparing of total pressure recovery ratio also demonstrated that the perforation can reduce the total pressure loss as the bow shock is swallowed. Our results in the perforated and non-perforated nozzle geometry agree well with the results reported and documented in the literature. This study aids designing and optimizing of the ramjet intake diffuser. This study also demonstrates that the OpenFoam can effectively be used to characterize the supersonic flow field in a complex geometry.

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