Agency: Department of Defense | Branch: Air Force | Program: STTR | Phase: Phase I | Award Amount: 150.00K | Year: 2013
ABSTRACT: The proposed work aims to build a physics-based rapid turnaround simulation capability for resolving combustion dynamics in liquid rocket engines operating at trans-critical and supercritical flow regimes. The methodology will explore both Reduced-Order Methods and Reduced-Basis Methods as potential candidates for efficient unsteady flow simulation, data storage and retrieval, and data reduction, as well as system identification and transformation of data to information and knowledge to support decision making at all levels. BENEFIT: This capability helps simulate, analyze, and predict combustion dynamics in rocket engines and gas turbine combustors at a computational cost about an order of magnitude less than what is currently needed. The increased efficiency comes with error bounds within tolerance levels that can be specified at run time. The building blocks of this methodology can also be used in data reduction and feature extraction in post processing field data from an unsteady-flow simulation. It has the potential to compress unsteady flow data to manageable levels for storage. In addition, the work will provide a basis for establishing practical means for transformation of data to knowledge to support decision making at all levels.
Agency: Department of Defense | Branch: Air Force | Program: STTR | Phase: Phase I | Award Amount: 100.00K | Year: 2010
The occurrence of combustion instability has long been a matter of serious concern in the development of liquid-propellant rocket engines due to the high rate of energy release in a confined volume in which energy losses are relatively small. Shear layer instabilities and intermittent growth rates of the mixing layer cause fluctuations in the burning rates and result in acoustic waves triggering flow instabilities. These flow oscillations may grow uncontrolled if there is a positive feedback between the oscillatory heat release at the combustion front and acoustic waves within the combustion chamber. The proposed work will focus on shear layers and mixing around single and multiple jets under acoustic excitation. Conditions that lead to positive feedback between the acoustic waves and shear layers will be identified and the influence of amplitude and frequency of excitation on shear layer development will be quantified. BENEFIT: The study of shear layer development around fuel jets in the presence of acoustic excitation will furnish useful information concerning the instability mechanisms in rocket engines. It will extend experimental data and enable identification of cause and effect relationships between flow features evolving in three-dimensional, unsteady fields. The outcome of the proposed research has the potential to help build stable liquid propellant rocket engines. The proposed work will support the experimental investigation at AFRL. The experimental results will serve as a validation of the proposed methodology. The simulation will augment the experimental observations by providing a complete, three dimensional view of the evolving flow.
Agency: Department of Defense | Branch: Missile Defense Agency | Program: STTR | Phase: Phase I | Award Amount: 100.00K | Year: 2010
The occurrence of combustion instability has long been a matter of serious concern in the development of liquid-propellant rocket engines due to the high rate of energy release in a confined volume in which energy losses are relatively small. Positive feedback between the acoustic waves and unsteady combustion could lead to the destruction of an engine in a fraction of a second. The situation is especially serious for engines of MDA’s concern in which the energy density is exceedingly high. The proposed work will employ physics-based simulations of the interaction between unsteady flow oscillations, acoustic waves, and combustion response in liquid-propellant rocket engines to identify and quantify underlying physiochemical mechanisms for driving combustion and flow oscillations. The effect of various design attributes will be investigated systemically.
Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase II | Award Amount: 723.76K | Year: 2011
ABSTRACT: When using the current state-of-the-art in spatial discretization, numerical flux functions and temporal integration techniques, the amount of effort required for simulations in general geometries is prohibitively large for most unsteady simulations in multi-element rocket engines. In addition, current numerical techniques, while effective for stationary flows, have a potential for spurious reflections at interfaces, where grid sizes change abruptly. These limitations render present day approaches less than successful for unsteady flows. Following an exhaustive search for an efficient method to push rocket engine flow simulations to the next level, both in terms of fidelity and turnaround time, Metacomp Technologies proposes to employ an innovative application of high resolution methodologies in the CFD++ framework. In Phase II, the innovative methodology will be applied to gas-gas, gas-liquid and liquid-liquid problem classes. BENEFIT: The proposed technology will result in a dramatic reduction in computational effort to achieve a desirable level of fidelity in the simulation of unsteady flow in rocket engines. It will lead to a modern high-fidelity rocket engine flow simulation capability that can predict the onset of instability as well as transient response of the flow in the combustion chamber to disturbances. The proposed research will complement other developments at Metacomp sponsored by the Air Force. CFD++ will become a useful tool for AFRL to explore new designs for high performance rocket engines. Concurrently, rocket engines are increasingly used in the commercial, non-military, market. Examples are the various Earth-to-Space rocket-powered payload carriers, some of which are government-sponsored, others privately owned. Recent years have seen the birth of commercial space travel. While still in its infancy, increased activity in this area indicates a potentially big market in the near future. Since all these vehicles must be able to travel in vacuum, most of them will resort to chemically fueled rocket engines, which will encounter the same transient problems associated with military rocket motors. Consequently, the current proposal has potential for a diverse usage, benefitting both military and commercial sectors.
Agency: Department of Defense | Branch: Missile Defense Agency | Program: SBIR | Phase: Phase I | Award Amount: 99.99K | Year: 2011
The goal of the activity is to increase simulation fidelity in predicting the fluid dynamics and plasma environment in the vicinity of reentry vehicle configurations. We begin with our current implementation of thermal equilibrium and non-equilibrium chemistry capability that includes the effects of finite rate chemistry with dissociation and ionization, catalytic wall treatment, general geometry capability, etc., and we will further enhance it. We also expect to develop a new model to help better predict turbulent flow in the boundary layer and wake including the effect of turbulence on the plasma environment. The enhanced capability will be able to fit into current end-to-end simulation processes that include relevant post-processing aspects.
Agency: Department of Defense | Branch: Missile Defense Agency | Program: SBIR | Phase: Phase I | Award Amount: 149.99K | Year: 2012
Metacomp Technologies, Inc. proposes a new 3D plume simulation tool to add another level of sophistication to MDA's IR scene generation capabilities. The new tool will provided an automated capability to obtain 3D solutions for relevant missile plume flow fields including angle-of-attack effects, verniers (with and without) gimballing, paddles, etc. High fidelity modeling techniques are used. The scope of the work begins with the treatment of steady-state simulations, but the infrastructure is intended to be extensible to transient flow simulation needs. Handoff capability to transfer the solution to DSMC codes, FLITES, SPURC, and other postprocessing tools will be provided.
Agency: Department of Defense | Branch: Missile Defense Agency | Program: SBIR | Phase: Phase I | Award Amount: 100.00K | Year: 2012
Metacomp proposes the development of a new class of efficient methods to incorporate the 3D and transient effects of vernier deployment into a base plume flow field. The methods are based on a hierarchical approach. Members of the hierarchy will be evaluated to establish their efficiency versus fidelity in the corresponding signature predictions.
Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase I | Award Amount: 100.00K | Year: 2010
Metacomp Technologies proposes to use a near-body fine mesh DNS sub-domain, coupled to a hybrid URANS/LES-type grid in the rest of the flowfield. Statistically-steady solutions will first be computed over a domain large enough to tolerate the imposition of ambient or freestream conditions at infinity. These solutions can be achieved rapidly, using conventional turbulence closures (possibly on a different mesh to that subsequently used for the transient simulation). A restricted sub-domain will then be created either by cutting or by a complete re-meshing of the region of interest, with the sub-domain mesh much more refined and with a strong emphasis on element isotropy as required by DNS. The truncated outer surfaces of the sub-domain mesh will be treated using special boundary conditions, which include self-tuning, far-field absorbing layer boundary conditions. There will also be the option of stochastically reconstructing any given statistical inlet information, in particular turbulent fluctuations which are obtained as a spatially-varying set of second-moments and length/time correlations from the given a priori URANS solution. The flexible wings of the MAV will be tightly coupled to an FSI tool, providing a robust grid deformation methodology which deforms the CFD mesh based on the deformation of the CSD grid. BENEFIT: Both military and civil applications are foreseeable: 1. Military application: Micro Aerial Vehicles, 2. Commercial application: Homeland security, law enforcement, and similar agencies where Micro Air Vehicles could be used for surveillance purposes.
Agency: Department of Defense | Branch: Missile Defense Agency | Program: SBIR | Phase: Phase II | Award Amount: 990.18K | Year: 2013
The proposed Phase II SBIR will address several 3-D flowfield features using a combination of steady-state and time-dependent modeling. Angle-of-Attack and multiple nozzle interactions at high altitude will be part of the study. The 3-D modeling is based on Metacomp Technologies CFD codes. The proposed effort will also develop methodologies to improve the"ease of use"of CFD codes by a non-expert. Topics include automatic 3-D grid generation and adaptive 3-D gridding. Validation of the 3-D flowfield effects through IR radiance map and associated total intensity comparison to available data is a key component of the proposed effort. The results of this Phase II effort will be compatible with OSF.
Agency: Department of Defense | Branch: Missile Defense Agency | Program: SBIR | Phase: Phase II | Award Amount: 1000.00K | Year: 2010
Metacomp Technologies has demonstrated, in Phase I, improvements to continuum approaches that can achieve higher fidelity in modeling the near-transitional flow regime. In Phase II, the new approach will be enhanced further, and additional possibilities explored. Improvements to the simulation processes are also being planned to ensure reliable accuracy, grid convergence, robustness, as well as significant reduction of simulation times. The improved methods will be applicable to systems with complex aerothermodynamics effects as well as to systems influenced by particulates.