Development and evaluation of new bleed boundary condition models for supersonic inlet boundary layer bleed flow

Thesis Type: Postgraduate

Institution Of The Thesis: Middle East Technical University, Faculty of Engineering, Department of Aerospace Engineering, Turkey

Approval Date: 2019

Student: Gökhan Akar

Supervisor: SİNAN EYİ


Shock wave/boundary layer interaction is an important issue that should be considered when studying supersonic inlet design for air vehicles. Porous bleed systems have traditionally been used for increase stability and efficiency of the supersonic inlets by means of removing the lower momentum part of the boundary layer to prevent flow separation caused by adverse pressure gradient. However, evaluating and determining the effect of the boundary layer bleed system on the performance of the supersonic inlet is one of the most challenging problems. In this thesis, single and porous bleed systems are studied for validation and investigation of bleed boundary condition modeling with concentrating on normal bleed hole configuration in computational fluid dynamics (CFD). Firstly, for validation of the method, three-dimensional CFD simulations are performed on fully resolved models (FRM) with modeling bleed plenum and hole cavity details. Grid converge study is conducted on different levels of grids using Spalart-Allmaras, Realizable k-ε and SST k-ω turbulence models. Optimal grid resolution and turbulence model are determined for bleed simulations. CFD analyses are expanded for different plenum total pressure ratios (Ppl/Pt). As a result of validation studies, the CFD results show good agreement with the wind tunnel test data. Furthermore, three new bleed boundary condition models are introduced to simulate bleed flow without modeling the bleed plenum and cavity details of the holes. Additional CFD analyses on the porous bleed case are performed including blowing effects to examine the correlation between mass flow rate and flow properties at the reference boundaries. Collected data are presented and discussed according to scaled parameters. The best curve fitting models on the scaled parameters are selected for each new bleed boundary condition (BBC) model. In order to evaluate the validity of BBC modeling alternatives, CFD studies are performed on the porous bleed systems with and without shock interaction with the implementation of new BBC models to the solver. Consequently, the results of the new BBC models are compared with the test data and the results of the FRM simulations. The bleed model based bleed region flow properties predicts bleed flow rates very close to the reference data. Moreover, all three models achieve remarkable success on simulation of flow structure and the models reflect well the impacts of the bleed region on efficiency in terms of total pressure recovery.