This Part I presents a detailed description of a numerical system built and tested with the final goal of reaching an accuracy of 2-3 dB over a meaningful range of frequencies for airliner engine noise, while having low empiricism and a general-geometry capability. The turbulence is treated by Large-Eddy Simulation with grids of around 1 million points, slightly upwind-biased high-order differencing, and implicit time integration. The code can incorporate boundaries and multi-block grids (thus avoiding the centerline singularity), and capture shocks. The sub-grid scale model is de-activated, because on present grids it strongly interferes with transition in the mixing layer. Without unsteady inflow forcing, the shear-layer roll-up and three-dimensionalization are realistic and reasonably insensitive to the grid. The far-field noise is computed using the permeable Ffowcs-Williams/Hawkings (FWH) formulation without external quadrupoles. The treatment of the disk that closes the FWH surface near the outflow ...

Noise prediction for increasingly complex jets. Part I: Methods and tests

: This book has several purposes, including a broad historical summary of combustion instabilities in propulsion systems; a concise compilation of the main mechanisms for instabilities in liquid and solid fueled rockets, ramjets, thrust augmentors and gas turbines; development of a theoretical framework for investigating unsteady motions in combustion systems; and accessible surveys of the basic material required to understand the subject. Emphasis is placed throughout the book on observed behavior. For well-understood reasons, the best, and in many respects most useful quantitative data, have been obtained for solid propellant rockets. Hence that type of device occupies a special position in the subject. The book comprises nine chapters and eight annexes. Material in the annexes is not essential for reading and broadly understanding the main part of the book, but is likely interesting for those choosing to do research on the subject. The nine chapters divide into three parts.

Unsteady Motions in Combustion Chambers for Propulsion Systems

A review of recent advances in the use of surface integral methods in Computational AeroAcoustics (CAA) for the extension of near-field CFD results to the acoustic far-field is given. These integral formulations (i.e. Kirchhoff's method, permeable (porous) surface FfowcsWilliams Hawkings (FW-H) equation) allow the radiating sound to be evaluated based on quantities on an arbitrary control surface if the wave equation is assumed outside. Thus only surface integrals are needed for the calculation of the far-field sound, instead of the volume integrals required by the traditional acoustic analogy method (i.e. Lighthill, rigid body FW-H equation). A numerical CFD method is used for the evaluation of the flow-field solution in the near field and thus on the control surface. Diffusion and dispersion errors associated with wave propagation in the far-field are avoided. The surface integrals and the first derivatives needed can be easily evaluated from the near-field CFD data. Both methods can be extended in orde...

https://engineering.purdue.edu/~lyrintzi/JAAfinal.pdf

Surface integral methods in computational aeroacoustics—From the (CFD) near-field to the (Acoustic) far-field

Experience gained from previous jet noise studies with the unstructured large-eddy simulation flow solver “Charles” is summarized and put to practice for the predictions of supersonic jets issued f...

Unstructured Large-Eddy Simulations of Supersonic Jets

This volume brings together international scientists in the field of solid rocket propulsion. Thirty-nine papers present in-depth coverage on a wide range of topics including: advanced materials and non-traditional formulations; the chemical aspects of organic and inorganic components in relation to decomposition mechanisms, kinetics, combustion and modelling; safety issues, hazards and explosive characteristics; and experimental and computational interior ballistics research, including chemical information and the physics of the complex flow field.

Solid propellant chemistry, combustion, and motor interior ballistics

http://gcasalis.free.fr/Files/ast2003.pdf

Instabilities and pressure oscillations in solid rocket motors

This paper describes a new mechanism leading to vortex shedding instabilities in long (large L/D) solid propellant motors. This mechanism is termed "parietal vortex shedding" and has been discovered thanks to numerical simulations of the unsteady, 2D, compressible, Navier-Stokes equations. It seems to involve hydrodynamic instabilities of the mean flow velocity profiles, corresponding to injection induced internal flow (so called Culick or Taylor profiles), that couple with the acoustic frequencies of the chamber. Although this mechanism is found to be very powerful, it seems to need some background noise to feed it. The presented simulations can explain observed instabilities in configurations, without segmentation or without protruding inhibitor rings, of a simplified subscale setup of the Ariane 5 MPS P230 solid propellant motor. Detailed comparisons are proposed and the influence of the propellant combustion response and of the turbulence of the flow field are analyzed by means of recently developed models. INTRODUCTION-OBJECTIVES not precisely known if inhibitor rings are or not destroyed or completely slack; on the other hand non segmented motors have also given rise to a same type of instability as vortex shedding : this is the case of one of the configuration (LP3D) of the LP3 set up presented in a preceding paper. As it is known ' ' , classical linear acoustic balance computations do not give reliable stability predictions in complex internal geometries (such as in the P230 motor), and then an effort was carried out to perform full numerical simulations of the unsteady, compressible internal flow fields. On the other hand, motor internal flows are mostly non-observable, and without numerical simulations it is not possible to describe the path of the aerodynamic instability development. The object of the present paper is to show hydrodynamic instabilities (which drive pressure oscillations) in configurations without shear flows induced by inhibitor rings, and to explain how these instabilities occur by means of numerical simulations. LP3D AND LP3E TEST CASES This work is part of the overall research effort, supported by CNES, accompanying the development of the Ariane 5 P230 MPS solid propellant motor (program ASSM for Aerodynamics of Segmented Solid Motors) and makes use of experimental results obtained during the combustion stability assessment program carried out for BPD and CNES, by delegation of ESA. In this scope, it is the continuation of earlier works about numerical simulations in solid propellant rocket motors ". The Ariane 5 motor, as other large segmented motors (U.S. Space Shuttle and Titan SRM) has been reported to exhibit pressure and thrust oscillations. Until recently, it was believed that such instability was exclusively due to the segmented design : inhibitor rings induce shear layers and vortex shedding driven oscillations. Nevertheless it is * Research scientist, Energetics Dept. 1 Project manager, Energetics Dept., Member AIAA Copyright © 1996 by the American Institute of Aeronautics and Astronautics, Inc., All rights reserved. The test cases are based on two configurations of the LP3 motor. The LP3 motor, which has been presented in reference , is a simplified 1/15 subscale set-up of the Ariane 5 P230 motor used to test several inter-segment arrangements. The configurations of interest here, called LP3D and LP3E, have no prominent obstacles at the mid chamber point, see figure 1. Both configurations have a cylindrical chamber of length 1632 mm and inner diameter 203 mm. At ignition, the main propellant burning surface is cylindrical, inner diameter 90 mm, with a chamfered surface near the aft end. The supersonic outlet nozzle is submerged, with a throat diameter of 56.5 mm, then the total length of the motor is 1650 mm. LP3D and LP3E have a small forward segment of 225 mm length, cylindrical for LP3D (169.5

Parietal vortex shedding as a cause of instability for long solid propellant motors - Numerial simulations and comparisons with firing tests

Investigation of integral surface formulations for acoustic post-processing of unsteady aerodynamic jet simulations

Segmented Solid Rocket Motors tend to develop unpredicted thrust and uressure oscillations. linked to a criodic vortex shcdding phcnomenon. Aspart of Arianc $ PUO MPS solid motor stability assessmcnt. a research effort was initiated and aimed at il full numerical simulation of the unsteady, compressible internal flow. The objective of the present work is to demonstrate the feasibility of a direct numerical simulation of the vortex shedding henomenon on test case motors. The computer equations, by means of an expicit predictor/corrector Mc Cormack scheme with an improved (Jameson type) artificial viscosity algorithm. A r p e r test ,case motor was devised by means of a hydro ynamic stability analy+ of mean flow shear layer. Computations done wth optimized artificial viscosity terms gave rise to a marked self excited vortex shedding phenomenon of constant am litude close to the second axial mode frequency, in v excited phenomenon was observefwith both the Euler and Navler-Stokes codes. Moreover planar com utations artificial viscosity added, and gave rise to identical vortex shedding henomenon. First comparisons with Flandro’s codes, so P ve the 2D unstead , Euler or Navier-Stokes bot R axisymmetrie and planar confi urations. Similar self have been performed with the Euler code, w ~ t R out any linearize 2 approach are also presented. INTRODUCTION-OBJECTIVES This work is part of the overall combustion stability assessment of the Ariane 5 P230 MPS solid ro ellant motor and has been supported b CNES and E P J . Due to the segmented design of the P$ motor, it is believed that there exists a potentially severe risk for motor instabiMy, although the moFor is predicted stable by conventional linear acoustic balance computations. Indeed, a number of US works, related to segmented motors (Space Shuttle and Titan solid boosters) 11-51 have riported significant and un redicted chamber frequencies. Further studies [4,6] have shown that a periodic vortex sheddin phenomenon is likely to be at the source of these oscifations. First suggestion of acoustic mode excitation by vortex shedding in solid rocket motors was made by Flandro and ressure and thrust oscillations at t f e first axial mode 1) Jacobs [7l. The eriodic shedding of vortices is the result of a strong cou Ping between the instabilit of mean flow sense, vortex shedding can be viewed as a, by-product of grain segmentation which produces regons of highly sheared mean flow, due to port area discontinuities and protrusions of inhibitor rings. Several related cold flow e eriments [4, 6, 8-12 have these experiments assume that a pair of diaphragms, at least, are required to give rise to vortex sheddin vortices are enerated at the first diaphragm and provife However, this is not the ony,mechanism for vortex shedding acoustic driving: one diaphragm or one region of sheared flow can be sufficient, the feedback mechanism being provided by the exhaust nozzle. This was the case in the ex eriment of reference [7], and could be the case in the & motor (Fig.1). Among, possible nozzle feedback mechanisms are direct vortex impingement on the nozzle wall or modulation of !he exiting mass flow rate by inhomogeneous flow, associated with one vortex. Flandro [13], extending the work of reference [7] has pro osed a linearized approach to evaluate the vortex shesding risk and to incorporate a corresponding driving term in linear acoustic balance codes. A lication of Flandro’s linearized model to Ariane 5 P a m o t o r has been carried out 141 and concluded of a possible vortex Recognizing the possible failure of classical linear acoustic balance computations even improved by Flandro’s mqdel, to achieve reliable stability predictions in complex internal eometries, such as in the P230 numerical simulation of the unsteady, comprcssiblc, internal flow field. Such a simulation would naturally couple mean flow shear layer instabilities and acoustic motions, including nonlinear effects and nozzle res once to vortices. The present work is the first part, of that effort and is devoted to demonstrating the easibility of a direct numerical capture of the periodic vortex shcdding phenomenon in test case solid propellant motors. This work was made possible by recent rogresses at unsteady state flow fields [15,16]. shear layers an B acoustic motions in the clamber. In this documented the vortex shed 3 ing phenomenon. Mlost of the acoustic B eedback when im inging on the second onc. P shedding driving 1 or Ariane 5 P230. motor,, a research ef B ort was initiated, aiming at a full ONERA in numerical simulations of bot g steady and * Research scientist .. Research scientist, Member AIAA Copyright

Nicolas Lupoglazoff

Papers

Instabilities and pressure oscillations in solid rocket motors

Parietal vortex shedding as a cause of instability for long solid propellant motors - Numerial simulations and comparisons with firing tests

Investigation of integral surface formulations for acoustic post-processing of unsteady aerodynamic jet simulations

Numerical simulation of vortex shedding phenomenon in 2D test case solid rocket motors

Numerical simulations of parietal vortex-shedding phenomenon in a cold flow set-up