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High Performance Computing Modernization Program Users Group Conference (HPCMP-UGC), 2010 DoD

Date 14-17 June 2010

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  • [Front cover]

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  • [Title page i]

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  • [Title page iii]

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  • Copyright (c) 2011 by The Institute of Electrical and Electronics Engineers, Inc. All rights reserved.

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  • Table of contents

    Page(s): v - xi
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  • Editor's Preface

    Page(s): xii - xiv
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  • Conference Committee

    Page(s): xv
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  • Reviewers

    Page(s): xvi
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  • Numerical Modeling of Turbulent, Parallel, Round Jets

    Page(s): 3 - 7
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (528 KB) |  | HTML iconHTML  

    Although extensive research has been conducted for turbulent single and offset wall jets, relatively little research has been conducted for turbulent parallel jets. Relevant applications include burners, boilers, film cooling, fuel-injection, heating and air-conditioning systems, and designs for pollutant exhaust stacks. The objective of the present work is to evaluate the use of Reynolds-averaged Navier-Stokes, k-epsilon, numerical simulations to predict the three-dimensional evolution of twin, isothermal, turbulent, round jets at a Reynold's number (based on jet diameter d and jet exit velocity Ue) of 25,000. Comparisons with existing experimental literature are conducted with respect to the stream wise turbulence intensity. Further, the stream-wise distance to the combined point is evaluated, along with integrations of stream wise momentum flux. This research will offer an enhanced understanding of parallel jet flow interaction in terms of flow entrainment, as well as provide insights into the sensitivity of the numerical results to variations of inlet turbulence. View full abstract»

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  • The Advantages and Costs of Higher-Fidelity Turbulence Modeling

    Page(s): 8 - 11
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (509 KB) |  | HTML iconHTML  

    This paper compares the results and the computational efficiency of a research code with that of a commercial code on the same problem. The research code (REACT-MB) is tested using its unsteady hybrid large-eddy simulation/Reynolds-averaged Navier-Stokes (LES/RANS) method as well as a more common steady-state Menter RANS method. CFD++ of Metacomp is tested on the same problem using its realizable k-ε turbulence model. Normal sonic ethylene injection through a circular injector into a Mach 2 cross-flow was simulated by each code. Time-averaged statistics of the hybrid LES/RANS computations and converged solutions from the RANS computations are compared with experimental contours of time-averaged mixture fraction. Scalability of the codes is also compared. View full abstract»

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  • Large-Scale Computations of Unsteady Forces on Marine Vehicles

    Page(s): 12 - 19
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1384 KB) |  | HTML iconHTML  

    Despite efforts to maintain streamlined shapes for minimal resistance and noise, US Navy marine vehicles oftentimes must have bluff body geometries or must operate in off-design modes. These situations produce separated flows that are unsteady. At large scales the flow unsteadiness may be the cause of structural concerns while the entire range of fluid dynamic scales, from large to small, may be the cause of unwanted hydro-acoustic radiated noise. Large-eddy simulations (LES) are a class of fluid flow solvers that resolve the energy-containing scales of attached and separated flows, potentially providing the velocity field forcing functions for structural and hydro-acoustics analyses. LES have strict temporal and spatial grid spacing requirements and in order to resolve the energy-containing turbulence scales at practical flow velocities, the problem sizes and run times can be quite impressive. The objective of this Challenge Project is to apply LES to several problems of urgent US Navy need that have heretofore been considered too large to solve in a timely fashion. The first of these problems occurs when a marine vehicle, translating forward, must stop suddenly. This entails reversing the rotation of the propeller in a maneuver called crashback. This generates the largest forces that a propeller will undergo in its lifetime, and therefore, prediction of the forces and determination of procedures to reduce the forces, are of utmost importance. Using LES we have been able to uncover and verify the physics of force generation. With this Challenge Project, methodologies are being developed for one-way coupling between fluid flow and structural calculations that entail 300,000+ hours of CPU time. Another problem that is being tackled with the help of the Challenge grant is flow about the Advanced SEAL Delivery System (ASDS). This is a challenging geometry as it has both complex geometry and is a high-Reynolds number attached flow. Thus, the grid quality and size are im- - portant issues to overcome. In this paper, we document simulations of bare-hull structured grids with 4 and 20 million cells. Results of our wall-resolved simulation show that the attached boundary layers behave as expected and therefore, give us confidence that we can correctly predict the occurrence and strength of stern flow separations. View full abstract»

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  • Analysis of External and Internal Aero-propulsive Phenomena in Hypersonic Vehicles

    Page(s): 20 - 25
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (317 KB) |  | HTML iconHTML  

    Several parallel efforts were initiated in the first year of the Challenge Project C4D with the goal of computing and understanding the main aero-propulsive phenomena that dominate hypersonic flight. For external transition, stability analyses were performed for the HIFiRE Flight 1. A 7 degree sphere-cone fore body was employed to determine likely transition characteristics and location at different times in the flight path. The implications of a shroud encapsulating the vehicle on placement of the pitot tube were also investigated. Since ground-tests are a major component of the HIFiRE campaign, the effectiveness of large-eddy simulations (LES) in predicting isolator dynamics was evaluated by comparison with experimental data. Finally, high-fidelity, three-dimensional simulations were employed to examine inlet-combustor coupling effects in a scramjet flow path. This is particularly relevant for configurations where the isolator segment is relatively short. Reynolds-averaged Navier-Stokes (RANS) with a k-w turbulence model, as well as LES, were performed with a finite-rate hydrocarbon-air mixture on the integrated inlet and combustor flow path, and compared to sequentially performed situations. The upstream influence of the combustor is considerably larger when the solution is obtained in an integrated fashion and sequential simulations may be overly optimistic in predicting un-start. Parametric studies indicate that reducing the fuel injection and equivalence ratio increases mixing efficiency in certain ranges, while reducing the tendency towards un-start. View full abstract»

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  • High-Fidelity Computations for Flexible Micro Air Vehicle Applications

    Page(s): 26 - 34
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (655 KB) |  | HTML iconHTML  

    Implicit large-eddy simulation (ILES) computations have been performed for canonical problems associated with flexible, flapping-wing micro air vehicles (MAVs). This computationally-intensive approach, which is able to directly model laminar/transitional/turbulent flow fields, requires the use of the best high performance computational platforms available. Results for the direct numerical simulation of the deep dynamic stall phenomenon over a rigid plunging airfoil section at transitional Reynolds numbers relevant to MAV systems are presented. Next, computations for two different flexible-wing geometries, a membrane-wing section and a three-dimensional, flexible-wing with an NACA0012 cross-section, are discussed. Finally, to investigate the relevant physics associated with a perching maneuver, computational results for a pitch, hold and return motion are examined. All computed results show good correlation with corresponding experimental measurements. View full abstract»

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  • Investigation of Boundary-Layer Separation for Lifting Surfaces

    Page(s): 35 - 44
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (881 KB) |  | HTML iconHTML  

    Flow separation from lifting surfaces such as airfoils is undesirable as it deteriorates performance. For example, when airfoils that are designed for large Reynolds numbers are operated at smaller off-design Reynolds numbers, laminar separation can occur. Laminar separation typically leads to transition and reattachment. Transition is influenced by factors, such as free-stream turbulence and wall roughness. Transition and reattachment affect the circulation and, thereby, separation itself. We are employing computational fluid dynamics for investigating the fundamental mechanisms of separation and transition for lifting surfaces. Using highly-resolved direct numerical simulations, we are investigating fundamental aspects of separation and transition in the presence of free-stream turbulence for canonical separation bubbles. In parallel, we are carrying out hybrid turbulence model simulations of an entire airfoil at a larger chord Reynolds number. The combined approach will advance both physical understanding and modeling capabilities, and thus provide a solid platform for the development of separation control strategies for practical applications. View full abstract»

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  • Investigation of Three-Dimensional Internal and External Flow Separation

    Page(s): 45 - 53
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1103 KB) |  | HTML iconHTML  

    Flow separation is always three-dimensional despite the fact that most of the past research has focused on two-dimensional separation. The three-dimensional character of separation is particularly relevant when low-aspect ratio geometries are considered. Separation is often associated with unsteadiness, which is caused by large coherent structures that are a consequence of hydrodynamic instability mechanisms of the mean-flow. We are employing direct numerical simulations for investigating the highly-complex flow physics of three-dimensional laminar separation bubbles. The introduction of pulse disturbances allows us to probe the instability mechanisms. In parallel, we are also employing hybrid turbulence models for simulations of the turbulent flow through a square-duct, and for the Stanford University asymmetric diffuser experiments. By advancing the understanding of the fundamental mechanisms governing three-dimensional separation and by devising modeling strategies for high-Reynolds number flows, we are laying the foundation that may lead to better predictive tools and to separation control devices for practical applications. View full abstract»

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  • A Dual-Mesh Simulation Strategy for Improved AV-8B Empennage Buffet Load Prediction

    Page(s): 54 - 63
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1553 KB) |  | HTML iconHTML  

    This paper describes the efforts to model full three-dimensional unsteady loads due to aerodynamic, and engine exhaust effects for an AV-8B aircraft model. This study utilizes USM3D for baseline comparison, and a CREATE-AV product - Helios - to transition into an engineering prediction tool. The comparative advantages of the different aerodynamic load predict in codes involved, and the capability gaps to routinely predict engineering loads for buffet performance are also reported. View full abstract»

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  • Computational Naval Ship Hydrodynamics

    Page(s): 64 - 70
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1013 KB) |  | HTML iconHTML  

    The primary purpose of our research efforts is to improve naval design and detection capabilities. Our current research efforts leverage high performance computing (HPC) resources to perform high-resolution numerical simulations with hundreds-of-millions to billions of unknowns to study wave breaking behind a transom stern, wave-impact loading, the generation of spray by high-speed planing craft, air entrainment by plunging breaking waves, forced-motion, and storm seas. This paper focuses on the air entrainment and free-surface turbulence in the flow behind a transom-stern and wave-impact loading on marine platforms. Two codes, Numerical Flow Analysis (NFA) and Boundary Data Immersion Method (BDIM), are used in this study. Both codes are Cartesian-based Large-Eddy Simulation (LES) formulations, and use either Volume-of-Fluid (VOF) (NFA) or conservative Volume-of-Fluid (cVOF) BDIM treatments to track the free-surface interface. The first project area discussed is the flow behind the transom stern. BDIM simulations are used to study the volume of entrained air behind the stern. The application of a Lagrangian bubble-extraction algorithm elucidates the location of air cavities in the wake and the bubble-size distribution for a flow that has over 10 percent void fraction. NFA simulations of the transom-stern flow are validated by comparing the numerical simulations to experiments performed at the Naval Surface Warfare Center, Carderock Division (NSWCCD), where good agreement between simulations and experiments is obtained for mean elevations and regions of white water in the wake. The second project area discussed is wave impact loading, a topic driven by recent structural failures of high-speed planing vessels and other advanced vehicles, as well as the devastation caused by Tsunamis impacting low-lying coastal areas. NFA simulations of wave breaking events are compared to the NSWCCD cube impact experiments and the Oregon State University, O.H. Hinsdale Wave Research L- - aboratories Tsunami experiments, and it is shown that NFA is able to accurately simulate the propagation of waves over long distances after which it also accurately predicts highly-energetic impact events. View full abstract»

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  • A Comparison of Wavelet-Based Schemes for Parameter Estimation

    Page(s): 71 - 76
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (617 KB) |  | HTML iconHTML  

    We present the numerical performance of orthogonal and biorthogonal wavelet-based parameterization schemes for solving parameter estimation problems for finding a global solution using the Simultaneous Perturbation Stochastic Approximation (SPSA) algorithm. The two schemes are tested on a two-phase flow problem using the Integrated Parallel Accurate Reservoir Simulators (IPARS) simulator in MATLAB. This work is an extension of the research described in (Velazquez et al., 2008) where wavelet parameterization was limited to the orthogonal Haar wavelet. We extend this work by considering the orthogonal Daubechies, Coiflet, and Symlet families of wavelets, and the biorthogonal Spline family of wavelets. In addition to a comparison of the various wavelet families, an analysis of the performance of each at different levels of decomposition will also be discussed. View full abstract»

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  • Computational Modeling of Geometrically-Complex Weapons Bays

    Page(s): 77 - 82
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (542 KB) |  | HTML iconHTML  

    A computational study of the weapons bay acoustics characteristics on a geometry representative of the F-35 is currently underway to support the development of possible "control" strategies for the reduction of dynamic pressure loads in the weapons bay. Initial computations evaluate the wind-tunnel model design and establish a baseline of what is expected during the wind-tunnel testing. Computational fluid dynamics (CFD) simulations and wind-tunnel tests on the 1/20th scale model at Mach 1.5 have demonstrated that leading-edge mass blowing combined with leading-edge shape modification as a control strategy provides significant reduction of ~4-5 dB were shown over the entire bay, with some regions showing reductions as high as 10 dB. Furthermore, the introduction of control via blowing resulted in no locations where there was any augmentation of noise levels. The CFD not only guided the wind-tunnel testing, it was also able to significantly improve the understanding of the complex flow field associated with the geometrically-complex weapons bay. The importance of the bay leading-edge geometry and the outboard door interaction with the shear layer are evident from the computational results. View full abstract»

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  • Parallelization of a Vector-Optimized 3-D Flow Solver for Multi-core Node Clusters

    Page(s): 83 - 88
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (459 KB) |  | HTML iconHTML  

    In this paper, we describe the development of a parallel version of the IR3D (Incompressible Realistic 3-D) code, which simulates the environmental effects on the evolution of vortices trailing behind control surfaces of underwater vehicles. The objective of the project was to parallelize and optimize the existing implementation for clusters of multi-core nodes. The primary motivation was to reduce turnaround time and add the capability to handle large problem sizes. Furthermore we were aiming for portability and scalability. The code solves the 3D Boussinesq equations for incompressible fluids. Fast-Fourier transforms (FFTs) are used for the calculation of horizontal derivatives and a higher-order compact finite difference scheme is used for vertical derivatives. To ensure incompressibility, the code employs a projection method for which we developed a new Poisson Solver. This solver works by computing 2D FFTs in horizontal-planes, numerically solving the resulting ordinary differential equations (ODEs) for Fourier coefficients, and then doing Fourier inversion. Parallelization is based on the Message Passing Interface (MPI) programming paradigm. We present performance and scalability results of PIR3D (Parallel IR3D) on a variety of hardware platforms and discuss methods for further optimization by exploiting additional by exploiting additional levels of parallelism. View full abstract»

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  • Simulation of Combustion of C/B Clouds in Explosions

    Page(s): 89 - 95
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1415 KB) |  | HTML iconHTML  

    We have developed adaptive high-resolution methods for numerical simulations of turbulent combustion of chemical/biological (C/B) clouds in thermobaric explosions. The code is based on our AMR (Adaptive Mesh Refinement) technology that was used successfully to simulate distributed energy release in explosions, such as: afterburning in TNT explosions and turbulent combustion of Shock-Dispersed Fuel (SDF) charges in confined explosions. Versions of the methodology specialized for low-Mach number flows have also been developed and extensively validated on a number of laboratory scale laminar and turbulent flames configurations. In our formulation, we model the gas phase by the multi-component form of the reacting gas-dynamics equations, while the particle-phase is modeled by continuum mechanics laws for 2-phase reacting flows, as formulated by Nigmatulin. Mass, momentum, and energy interchange between phases are taken into account using Khasainov's model. Both the gas and particle phase conservation laws are integrated with their own second-order Godunov algorithms that incorporate the non-linear wave structure associated with such hyperbolic systems. Specialized ordinary differential equation (ODE) methods are used to integrate chemical kinetics and interphase terms. Adaptive grid methods are used to capture the energy-bearing scales of the turbulent flow (the MILES approach of J. Boris) without resorting to traditional turbulence models. The code is built on an AMR framework that manages the grid hierarchy. Our work-based load-balancing algorithm is designed to run efficiently on massively-parallel computers. Gas-phase combustion in the explosion products (EP) cloud is modeled in the fast-chemistry limit, while Aluminum particle combustion in the EP cloud is based on the finite-rate empirical burning law of Ingignoli. The thermodynamic properties of the components are specified by the Cheetah code. At the 19th HPCUG meeting in 2009, we summarized recent progress in:- - "AMR Code Simulations of Turbulent Combustion in Confined and Unconfined SDF Explosions". These models were used successfully to simulate the simultaneous after-burning of booster products and combustion of Aluminum (Al) in SDF explosion clouds. Computed pressure histories were shown to be in excellent agreement with the data -- thereby proving the validity of our combustion modeling of such explosions. This year, the modeling has been extended to include the mixing and combustion of C/B clouds in such explosion fields. Here we will establish how the cloud consumption by combustion depends on chamber environments. View full abstract»

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  • Use of Time-Accurate CFD for Inlet-Fan Interaction

    Page(s): 96 - 103
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (818 KB) |  | HTML iconHTML  

    The Compressor Aerodynamics Research Laboratory at Wright-Patterson Air Force Base is currently investigating, experimentally and numerically, the effects of inlet distortion on transonic fan performance. The experimental investigation will quantify the flowfield for a cold-tested diffuser-fan with distortion screens, and a coupled diffuser-fan system. Each of these experiments will be mirrored numerically using the solver TURBO. The primary research goal of the work is to quantify the physical mechanisms for distortion-transfer and develop reduced-order models to account for performance and stall-margin loss in engine design. As inlet geometries become more aggressive, namely having smaller length to diameter ratios, the secondary flow physics induce potentially-harmful distortion at the engine fan face. The effects of distortion are typically only investigated experimentally, and at too low a temporal and spatial resolution to adequately quantify the mechanisms which attenuate or amplify total pressure and total temperature non-uniformities. Because of the imbalance of operating conditions between different passages of the turbo-machine, adverse effects have been noted on stall-margin which cannot be explained with traditional design methods. Recently large-scale simulations have been used to investigate total pressure distortion patterns on several full-annulus, multi-stage fan configurations. The current effort simulates a distortion-producing inlet coupled with a single-stage fan. This allows distortion of total pressure, total temperature, and flow angularity to be investigated. Preliminary numerical results have been obtained on the US Air Force Research Laboratory DoD Supercomputing Resource Center (AFRL DSRC) SGI Altix 4700 system for the coupled diffuser-fan system. Total pressure and temperature exhibit both a distinct circumferential variation and a counter-rotation shift. As the simulations are analyzed, a greater understanding of performance detriment,- - stall-inception, and distortion- transfer in an installed aircraft system will be gained. Finally, a brief discussion of continued efforts investigating blade-row interactions will be presented. View full abstract»

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  • Use of the NRL DHPI System to Transfer Dispersion Nomograf Capabilities to the Field

    Page(s): 104 - 108
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (294 KB) |  | HTML iconHTML  

    As the ability to generate Dispersion Nomografs™ on the Dedicated High Performance Computing Project Investment (DHPI)-provided machine matures, the focus of this project has moved to the transition of CT-Analyst. CT-Analyst provides near-instantaneous urban plume prediction with unprecedented accuracy and ease. This paper will focus on the transition efforts to deploy CT-Analyst's unique Dispersion Nomograf to military and civilian training and field applications. Overall, it has been easier to transition CT-Analyst's capabilities to training tools versus field deployable applications. We will describe the users and types of applications CT-Analyst has been transitioned to, as well as the difficulties encountered during the transition process. View full abstract»

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  • Computational Analysis for Air/Ship Integration: 1st Year Report

    Page(s): 109 - 114
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (786 KB) |  | HTML iconHTML  

    This paper documents the accomplishments from the first year of a three-year Grand Challenge Project focusing on the application of computational fluid dynamics (CFD) to predict coupled ship and aircraft aerodynamics. Unstructured chimera techniques were used to simulate the coupled ship and aircraft systems. Dynamic aircraft maneuvers were prescribed with the intention of building to simulations with an auto-pilot in- the-loop. All simulations were computed in a time- accurate fashion, due to the unsteady nature of the flow field, and used the commercial flow solver Cobalt. Analyses for both vertical shipboard landings of the Joint Strike Fighter and rotary-wing aircraft are discussed. View full abstract»

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  • Advancing State-of-the-Art Unsteady, Multidisciplinary Rotorcraft Simulations

    Page(s): 115 - 122
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (764 KB) |  | HTML iconHTML  

    To address the complex multidisciplinary nature of rotorcraft analysis, high-fidelity computational fluid and structural dynamics models have been developed to investigate a range of challenging rotorcraft issues. First, an advanced technology, active flap rotor (Boeing SMART) is investigated, and performance, aerodynamic and structural loads, vibration, noise prediction and flow physics mechanisms are shown. The rotor model includes complex and detailed flap and flap-gap modeling. Second, analyses on an advanced dynamics model (ADM) research configuration rotor investigate regressing lag mode (RLM) aero elastic instabilities. Tightly-coupled computational fluid dynamics (CFD)/computational structural dynamics (CSD) stability calculations show noticeable improvement over lower fidelity methods. Third, the state-of-the-art capability of CFD methods to directly predict low frequency in-plane noise on realistic lifting rotors is benchmarked for the first time. In all cases, comparisons are made between CFD/CSD, comprehensive analyses, and experimental data. Taken together, these works offer an important advancement in rotorcraft analysis capability for advanced technology rotor configurations under study for future Army rotorcraft, and highlight future needs in next-generation rotorcraft analysis software. View full abstract»

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