Buzz Instability in a Mixed-Compression Air Intake

Abstract

Euler equations. The starting as well as the unstarting of the intake wasstudied.Recently,Trapieretal.[11]carriedoutadetached-eddy simulation and compared the results with their own experiments. The present work is a part of our ongoing work [10] to study flow in mixed-compression intakes. The viscous effects have been included in this work. The geometry of the inlet is very similar to the one experimentally studied by Anderson and Wong [9]. The governing equations for the flow analysis are the compressible Navier–Stokes equations in the conservation law form. A stabilized finite element formulationbasedonconservationvariablesisusedtosolvethe flow equations. The streamline-upwind/Petrov–Galerkin stabilization method [12,13] is employed to stabilize the computations against spuriousnumericaloscillationsduetoadvection-dominated flows.A shock capturing term is added to the formulation to provide stability to the computations in the presence of discontinuities and large gradients in the flow [14–16]. The time integration of the flow equations is done via the generalized trapezoidal rule. For unsteady computations, we employ a second-order accurate-in-time procedure. The role of bleed in starting/unstarting the intake and controlling the buzz instability is investigated. The flow during the buzz is studied in detail to bring out the difference between the little and big buzz.