Simulations of the flow generated by fluidic inserts in a converging diverging nozzle

Open Access
Author:
Lampenfield, Jacob John
Graduate Program:
Aerospace Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
None
Committee Members:
  • Philip John Morris, Thesis Advisor
Keywords:
  • CFD
  • computational fluid dynamics
  • converging
  • diverging
  • nozzle
  • aeroacoustics
  • noise reduction
Abstract:
This investigation of military jet noise prediction and reduction is a continuation from previous projects and is still ongoing. Numerical simulations have been performed on baseline nozzles and nozzles with the addition of fluidic inserts. The design Mach number of the nozzle is 1.65, but only the over-expanded Mach number of 1.36 has been analyzed. The fluidic inserts have been generated using different numbers of injectors and injector hole sizes. The supersonic military style jet simulation makes use of advanced meshes combined with CFD technology. Steady Reynolds-averaged Navier-Stokes (RANS) simulations are produced by the CFD technology and used to predict and understand the flow field. Through collaboration with experimental noise measurements, a correlation between flow field properties and noise reduction is examined. The ANSYS suite is used to create grids and run simulations by using ANSYS-ICEM and ANSYS-CFX respectively. The geometry of the nozzle is modeled using an unstructured hexahedral mesh. The Menter SST turbulence model with a wall function is used inside of the CFX-Solver. The objective is to further simulate a military-style nozzle, similar to the GE F404 family, with added fluidic inserts. Previous simulations have been conducted and new simulations were planned and performed based on information gathered from the previous simulations and experiments. The fluidic inserts are used to alter the flow field to achieve the same effect of hard wall corrugations, which have been shown to reduce noise levels. The numerical simulations are used to help understand the effects on the flow field created by the fluidic inserts and to attempt to find flow parameters that can be correlated to noise reduction. Simulations were first run on a simpler geometry to give an understanding of the fluidic inserts. They were conducted by having three injectors exhausting into a supersonic boundary layer. The freestream Mach number was 1.5 to simulate the inside of the nozzle. A study was then conducted to see the effect of a change in downstream injector angle on the fluidic insert. There was also a study of an increase Reynolds number as three different sized nozzles were modeled. The first size is a small nozzle with an exit diameter of 0.885 inches. The nozzle size was then increased by a factor of 1.2 to an exit diameter of 1.06 inches. A third nozzle was then modeled to recreate the nozzle used in the GE experiments. This nozzle had a diameter of 5.07 inches. The results from all the simulations were then compared to experimental acoustic data. Flow parameters were then integrated from each simulation to attempt to find a correlation to noise reduction. Parameters such as streamwise vorticity, turbulent kinetic energy, and Q criterion were all analyzed.