Earl P. N. Duque

Revolutionary Physics-Based Design Tools for Quiet Helicopters

Abstract : A computational research program was performed at Georgia Institute of Technology, Penn State University, and at Northern Arizona University to develop a set of first-principles based computational modeling tools for analyzing and designing advanced helicopter configurations. The approach involved incorporation of advanced numerical algorithms and turbulence models in OVERFLOW 2, development of advanced comprehensive analyses (DYMORE and RCAS) that are seamlessly coupled to the flow analysis, modeling of rotor noise characteristics using an advanced acoustics prediction tool (PSU-WOPWOP) that is seamlessly coupled to the flow analysis and the comprehensive analyses, and validation and application of the integrated suite of tools for current generation (UH-60, BO105) and next generation configurations. Under the Phase I-B extension, assessment of this suite of tools is being performed by Ga Tech and Penn State for the Boeing MD-900 model rotor (MDART), an actively controlled rotor (SMART), and the Comanche rotor blade (as an option).

GPGPU parallel algorithms for structured-grid CFD codes

A new high-performance general-purpose graphics processing unit (GPGPU) computational uid dynamics (CFD) library is introduced for use with structured-grid CFD algorithms. A novel set of parallel tridiagonal matrix solvers, implemented in CUDA, is included for use with structured-grid CFD algorithms. The solver library supports both scalar and block-tridiagonal matrices suitable for approximate factorization (AF) schemes. The computational routines are designed for both GPU-based CFD codes or as a GPU accelerator for CPU-based algorithms. Additionally, the library includes, among others, a collection of nite-volume calculation routines for computing local and global stable time

Rotor wake modeling with a coupled Eulerian and Vortex Particle Method

A new coupled Eulerian/Lagrangian CFD method is presented for rotorcraft wake ∞ow modeling. Speciflcally, the Vortex Particle Method is coupled with an overset, flnite-difierence URANS algorithm to solve the wallbounded and wake ∞ow. The coupled algorithm is presented in detail along with the necessary parallel computing algorithms. The coupled algorithm is then used to model the ∞ow over a NACA0015 airfoil wing at 12 ‐ angle-of-attack. Results from the coupled algorithm are compared to a baseline CFD solution and, where available, experimental data. Surface pressure proflles, sectional loads and tip vortex visualization and velocity proflles are compared to assess the efiectiveness of the coupling algorithm. Comparisons show that the coupled approach can capture the tip vortex far better than the baseline URANS solution. However, the particle solution can be signiflcantly impacted by the excessive dissipation through the Eulerian domain.

Computational Fluid Dynamics of Flatback Airfoils for Wind Turbine Applications

This paper presents results from a computational study of the aerodynamic performance of various atbac k airfoils designed for wind turbines. Multiple turbulence modelings methods are used for the aerodynamic modeling: Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations, Detached-Eddy Simulations (DES) and a Hybrid RANS/Large-Eddy Simulations (HRLES) method based on the k{! RANS model and k{equation sub-grid LES model. All simulations make use of overset structured grids. Turbulence modeling and grid resolution studies show that both DES and HRLES methods capture the expected qualitative turbulent behavior such as cross o w in the separated wake regions of the o w. Quantitative results include the predicted lift and drag over a range of angles-of-attack using URANS. It is shown that the atbac k airfoil design results in a substantially increased lift compared to traditional thin trailing edge airfoils. Flow-eld results from the two advanced modeling methods, DES and HRLES, are qualitatively compared and analyzed. It is observed that the DES method does not predict the transition and separation along the airfoil while the HRLES method does. This limitation is explained and the eects on the aerodynamic forces is also given.

Performance analysis, design considerations, and applications of extreme-scale in situ infrastructures

A key trend facing extreme-scale computational science is the widening gap between computational and I/O rates, and the challenge that follows is how to best gain insight from simulation data when it is increasingly impractical to save it to persistent storage for subsequent visual exploration and analysis. One approach to this challenge is centered around the idea of in situ processing, where visualization and analysis processing is performed while data is still resident in memory. This paper examines several key design and performance issues related to the idea of in situ processing at extreme scale on modern platforms: scalability, overhead, performance measurement and analysis, comparison and contrast with a traditional post hoc approach, and interfacing with simulation codes. We illustrate these principles in practice with studies, conducted on large-scale HPC platforms, that include a miniapplication and multiple science application codes, one of which demonstrates in situ methods in use at greater than 1M-way concurrency.

RCAAPS - Rotorcraft Computational AeroAcoustics Post-Processing System

Large and Unsteady Computational Fluid Dynamic (CFD) solutions are becoming more common place and require better post processing capabilities to handle the data particularly for Large Eddy Simulations and Computational Aero-Acoustics Solutions. To meet this growth a tool is needed that leverages parallel computing paradigms and utilize Faster I/O methods to more quickly compute intensive post processing functions. To address this need, Intelligent Light has developed Rotorcraft Computational AeroAcoustics Post-processing System (RCAAPS). RCAAPS consists of a complete integrated computer hardware system, enhanced NASA flow solvers such as OVERFLOW and FUN3D and a Graphical User Interface that permits interactive exploration of large unsteady data for rotorcraft aero-acoustics. The GUI also enables the user to interactively adjust the inputs to the acoustic code PSU-WOPWOP and to easily create time history and spectral plots. This paper presents the prototype integrated hardware/software system that has been developed.

Visualization and Data Analytics Challenges of Large-Scale High-Fidelity Numerical Simulations of Wind Energy Applications

Visualization and data analysis techniques are explored to alleviate big-data problems found in simulations regarding wind energy applications including full wind farm simulations with blade-resolved geometries for wind turbines. Techniques for streamlining workflows for large-scale simulations are investigated and instrumented in the WAKE3D software framework. In-situ analysis through Libsim is instrumented and used to export data of high-fidelity wind turbine simulations that is post-processed using FieldView and VisIt.

In Situ Visualization and Production of Extract Databases

Simulations running at high concurrency on HPC systems generate large volumes of data that are impractical to write to disk due to time and storage constraints. Applications often adapt by saving data infrequently, resulting in datasets with poor temporal resolution. This can make datasets difficult to interpret during post hoc visualization and analysis, or worse, it can lead to lost science. In Situ visualization and analysis can enable efficient production of small data products such as rendered images or surface extracts that consist of polygonal geometry plus fields. These data products are far smaller than their source data and can be processed much more economically in a traditional post hoc workflow using far fewer computational resources. We used the SENSEI and Libsim in situ infrastructures to implement rendering workflow and surface data extraction workflows in the AVF-LESLIE combustion code. These workflows were then demonstrated at high levels of concurrency and showed significant data reductions and limited impact on the simulation runtime.

In-Situ Feature Tracking and Visualization of a Temporal Mixing Layer

The flow field for a temporal mixing layer was analyzed by solving the Navier-Stokes equations via a Large Eddy Simulation method, LESLIE3D, and then visualizing and post-processing the resulting flow features by utilizing the prototype visualization and CFD data analysis software system Intelligent In-Situ Feature Detection, Tracking and Visualization for Turbulent Flow Simulations (IFDT). The system utilizes volume rendering with an Intelligent Adaptive Transfer Function that allows the user to train the visualization system to highlight flow features such as turbulent vortices. A feature extractor based upon a Prediction-Correction method then tracks and extracts the flow features and determines the statistics of features over time. The method executes In-Situ with the flow solver via a Python Interface Framework to avoid the overhead of saving data to file. The movie submitted for this visualization showcase highlights the visualization of the flow such as the formation of vortex features, vortex breakdown, the onset of turbulence and then fully mixed conditions.

Towards a coupled Eulerian/Lagrangian simulation method for rotorcraft wake modeling

A coupled grid-based (Eulerian) and particle-based (Lagrangian) CFD algorithm intended for rotorcraft wake modeling is presented here. The OVERFLOW-2 CFD (Eulerian) ∞ow solver is coupled with a Lagrangian Vortex Particle Method (VPM) code. The two difierent solver methods are used to model difierent domains of a single simulation environment. Results are presented using both the coupled Eulerian-Lagrangian and traditional Eulerian-only (with overset grids) methods for the ∞ow over a cylinder at Re = 150.