检索结果-内蒙古大学图书馆

A flux correction approach for the pressure equation in incompressible flows on overset meshes in OpenFOAM

COMPUTER PHYSICS COMMUNICATIONS 2022年 273卷 108279-108279页

作者： Chandar, Dominic D. J. Sitaraman, Jayanarayanan Queens Univ Belfast Sch Mech & Aerosp Engn Belfast BT7 1NN Antrim North Ireland Parallel Geometr Algorithms LLC Sunnyvale CA 94087 USA

Standard interpolation methods between overset meshes in finite-volume methods such as distance-weighted or least squares based methods do not respect the conservation property of the finite-volume method. As the resultant fluxes exchanged between meshes do not vanish on a global scale, there is either a source or sink in the mass, momentum or energy. This then manifests itself as reduced order of accuracy in the flow variables such as velocity and pressure or high amplitude oscillations in the pressure field when the mesh moves. For incompressible flows, the pressure Poisson equation unanimously decides the extent to which mass is conserved. In this paper, the pressure Poisson equation is isolated and analyzed independently to understand the source of the conservation error. Based on the discretized pressure Poisson equation, a novel flux correction method applicable to moving overset meshes is derived. Using exact solutions for the pressure Poisson equation, it is shown that this method improves the order of accuracy and the discretization error and reduces the mass conservation error. An order of magnitude reduction in the oscillations of the pressure field is also observed when the mesh moves. (C) 2021 Elsevier B.V. All rights reserved.

关键词： Incompressible flows Overset meshes Finite-volume methods OpenFOAM

来源：评论

学校读者我要写书评

暂无评论

Lessons Learned from a Combined Experimental-Computational Study on Pitching Airfoil Cycle-to-cycle Variations

Lessons Learned from a Combined Experimental-Computational S...

引用

AIAA Science and Technology Forum and Exposition (AIAA SciTech Forum)

作者： Tran, Steven Sitaraman, Jayanarayanan Ramasamy, Manikandan NASA Sci & Technol Corp Ames Res Ctr Moffett Field CA 94035 USA Parallel Geometr Algorithms LLC Sunnyvale CA USA US Army Combat Capabil Dev Command Aviat & Missil Moffett Field CA USA

ISBN: (纸本)9781624106316

This paper describes a combined experimental and computational effort to characterize the cycle-to-cycle variations previously observed in oscillating airfoil experiments. It is common in the dynamic stall community to assume that the variation in loads between pitch cycles is primarily due to random turbulent fluctuations, which in turn justifies the assumption that the loads can be accurately represented using simple phase averages. However this work, which numerically and experimentally models an oscillating modified VR-12 airfoil at two different conditions, shows that various aspects ranging from model setup to the inherent fluid dynamics may lead to significant furcation in the loads. These clusters of loads are poorly represented by simple phase averaging techniques and require special consideration. To the best of the authors' knowledge, this work is the first study to successfully capture furcation using CFD and excellent agreement is observed overall for cluster averaged quantities. Furthermore, this work also presents several lessons learned concerning best practices for the dynamic stall community towards improving future correlations between CFD and experimental data and the quality of future dynamic stall datasets in general.

关键词： Computational fluid dynamics

来源：评论

学校读者我要写书评

暂无评论

ROAM-ML: A reduced order aerodynamic module augmented with neural network digital surrogates

ROAM-ML: A reduced order aerodynamic module augmented with n...

引用

AIAA Science and Technology Forum and Exposition (AIAA SciTech Forum)

作者： Martinez, Daniel Jude, Dylan Sitaraman, Jayanaranayan Brewer, Wesley Wissink, Andrew Ames Res Ctr Sci & Technol Corp Moffett Field CA 94035 USA Ames Res Ctr US Army DEVCOM AvMC Moffett Field CA USA Parallel Geometr Algorithms LLC Sunnyvale CA USA DoD RPCMP PET GDIT Vicksburg MS USA

ISBN: (纸本)9781624106316

Computational engineering and analysis is evolving with the inclusion of accurate and efficient digital surrogate models. Recently, neural networks have been proposed as machine learning tools to complement and solve physics-based processes using data-driven or physics-informed or a combination of these. The U.S Army Technology Development Directorate (TDD) computational aeromechanics group has built a research and operational infrastructure over the past ten years to model full-scale helicopter maneuvers with Helios simulation software, which consequently has allowed subject matter experts to generate significant amounts of meaningful data and rotorcraft engineering analysis. In this work, we integrate machine learning training and inference modules to the Helios software architecture in order to mine the high-fidelity computational domain and develop optimal digital surrogates. We expose our workflow and ML-pipeline with the purpose of revealing reproducible guidelines, valuable insights, limitations and early successes. Moreover, the operational deployment and validation of these surrogates in Helios reduced order aerodynamic module ROAM has allowed us to better understand how to evolve and mature these surrogates. ROAM-Surf-ML and ROAM-Line-ML are the high and mid-fidelity neural network surrogates presented in this work, suggesting a model fidelity spectrum where multiple formulations are feasible. ROAM-Surf-ML achieves a generalization accuracy that significantly outperforms currently in-place reduced order methods without introducing additional computational costs. Our implementation efficiently integrates network inference with actuator line methods and GPU-accelerated or CPU-based Cartesian solvers.

关键词： Aerodynamics

来源：评论

学校读者我要写书评

暂无评论

Overset meshes for incompressible flows: On preserving accuracy of underlying discretizations

引用

JOURNAL OF COMPUTATIONAL PHYSICS 2021年 428卷 109987-109987页

作者： Sharma, Ashesh Ananthan, Shreyas Sitaraman, Jayanarayanan Thomas, Stephen Sprague, Michael A. Natl Renewable Energy Lab Golden CO 80401 USA Parallel Geometr Algorithms LLC Sunnyvale CA USA

This study on overset meshes for incompressible-flow simulations is motivated by accurate prediction of wind farm aerodynamics involving large motions and deformations of components with complex geometry. Using first-order hyperbolic and elliptic equation proxies for the incompressible Navier-Stokes (NS) equations, we investigate the influence of information exchange between overset meshes on numerical performance where the underlying discretization is second-order accurate. The first aspect of information exchange surrounds interpolation of solution where we examine Lagrange and point-cloud-based interpolation for creating constraint equations between overset meshes. To maintain overall second-order accuracy, higher-order interpolation is required for elliptic problems, but linear interpolation is sufficient for hyperbolic problems in first-order form. Higher order point-cloud-based interpolation provides a pathway to maintaining accuracy in unstructured meshes, but at higher complexity. The second aspect of information exchange focuses on comparing the approaches of overset single system (OSS) and overset Additive Schwarz (OAS) for coupling the linear systems of the overlapping meshes. While the former involves a single linear system, in the latter the discrete linear systems are solved separately, and solving the global system is accomplished through outer iterations and sequential information exchange in a Jacobi fashion. For the test cases studied, accuracy for hyperbolic problems is maintained by performing two outer iterations, whereas many outer iterations are required for elliptic systems. The order-of-accuracy studies explored here are critical for verifying the overset-mesh coupling algorithms used in engineering simulations. Accuracy of these simulations themselves is, however, quantified using engineering quantities of interest such as drag, power, etc. Consequently, we conclude with numerical experiments using NS equations for incompressible flows wher

关键词： Computational fluid dynamics Unstructured meshes Chimera grid Overset Additive Schwarz Wind energy

来源：评论

学校读者我要写书评

暂无评论

Fully Automated Surface Mesh Adaptation in Strand Grid Framework

Fully Automated Surface Mesh Adaptation in Strand Grid Frame...

引用

AIAA Science and Technology Forum and Exposition (AIAA SciTech Forum)

作者： Lakshminarayan, Vinod Aubry, Romain Sitaraman, Jayanaranayan Wissink, Andrew NASA Sci Technol Corp Ames Res Ctr Moffett Field CA 94035 USA KeyW Corp 17740 Milestone Pkwy Hanover MD USA Parallel Geometr Algorithms LLC Sunnyvale CA USA US Army Combat Capabil Dev Directorate Aviat & Missile Ctr Moffett Field CA USA

ISBN: (纸本)9781624106316

An approach for dynamically adapting body-fitted overset Strand meshes in HPCMP CREATE (TM)-AV Helios is demonstrated. The approach couples the Strand-Cartesian near-body/off-body meshing paradigm with the HPCMP CREATE (TM)-FT Capstone software to generate and refine surface meshes. Helios then constructs the dual volume mesh and interpolates data to the adapted mesh. The approach is parallel and fully automated, requiring no intervention on the part of the user during the adaptation process. Tests are conducted for RANS calculations on the ONERA M6 wing configuration, both static and pitching. With the pitching wing, the adaptive process completes 192 time-dependent adapt cycles, maintaining good quality and good solution accuracy. On 440 processors, the adaptive process incurred less than 8% computation overhead.

关键词： Mesh generation

来源：评论

学校读者我要写书评

暂无评论

Algorithmic Improvements and Capability Enhancements to PUNDIT

Algorithmic Improvements and Capability Enhancements to PUND...

引用

AIAA Science and Technology Forum and Exposition (AIAA SciTech Forum)

作者： Sitaraman, Jay Jude, Dylan Roget, Beatrice Tran, Steven Abras, Jennifer Bin, Jonhoon Shipman, Jeremy Parallel Geometr Algorithms LLC Sunnyvale CA 94087 USA US Army Combat Capabil Dev Command Aviat & Missil Moffett Field CA USA NASA Sci Technol Corp Ames Res Ctr Moffett Field CA USA HPCMP CREATETM AV Qual Assurance Moffett Field CA USA CRAFT Tech Pipersville PA USA

ISBN: (纸本)9781624106316

Overset methods, when utilized within a multi-solver framework, are a very flexible and powerful toolset for analyzing moving body problems. The parallel Unsteady Domain Information Technology (PUNDIT) module is the dedicated overset grid assembly module that is used within both HPCMP CREATE (TM)-AV Helios and Kestrel. PUNDIT is fully parallel and uses the automated implicit hole-cutting technique. Several development efforts are being pursued such as (1) Improved representation of body hole maps (2) Extension of domain connectivity algorithms to be amenable for GPU computing (3) investigation of high-order conservative interpolation algorithms and (4) General grid-to-grid interpolation techniques. The methodologies and results obtained in these research areas are described in this manuscript.

关键词： Interpolation

来源：评论

学校读者我要写书评

暂无评论

Towards Adaptive Surface Meshing in Strand Grid Framework

Towards Adaptive Surface Meshing in Strand Grid Framework

引用

AIAA Science and Technology Forum and Exposition (AIAA SciTech Forum)

作者： Lakshminarayan, Vinod Sitaraman, Jayanarayanan Wissink, Andrew NASA Ames Res Ctr Sci & Technol Corp Moffett Field CA 94035 USA Parallel Geometr Algorithms LLC Sunnyvale CA USA US Army Combat Capabil Dev Command Aviat & Missil Moffett Field CA USA

ISBN: (数字)9781624106095

ISBN: (纸本)9781624106095

The strand grid approach is a flow solution method where a prismatic-like grid using \strands" is grown to a short distance from the body surface to capture the viscous boundary layer and the rest of the domain is covered using an adaptive Cartesian grid. The approach offers several advantages in terms of nearly automatic grid generation and adaptation, ability to implement fast and efficient flow solvers that use structured data in both the strand and Cartesian grids, and the development of an efficient and highly scalable domain connectivity algorithm. Earlier works by the authors presented meshing and domain connectivity algorithms to automatically generate meshes for geometrically and topologically complex test cases;and introduced a fully parallel and highly efficient strand grid solver called mStrand. An initial attempt has also been made in automating the generation of surface meshes starting from a closed parameterized surface. This paper aims at developing an infrastructure in the strand grid framework to support fully automated surface mesh adaptation, which will allow better use of the available degrees of freedom and improve the overall automation process. The developed infrastructure is verified by performing uniform surface mesh refinement on the ROBIN fuselage. In addition, an initial demonstration of a solution-based surface mesh refinement is provided for the ONERA M6 wing configuration.

关键词： Fuselages Turbulent Boundary Layer Wing Configurations parallel Mesh Generation Roe Approximate Riemann Solver Reynolds Averaged Navier Stokes Rotorcraft Simulations Computational Fluid Dynamics High Performance Computing Lift Coefficient

来源：评论

学校读者我要写书评

暂无评论

Prismatic mesh generation using minimum distance fields

引用

COMPUTERS & FLUIDS 2020年第0期200卷 104429-000页

作者： Roget, Beatrice Sitaraman, Jay Lakshminarayan, Vinod Wissink, Andrew NASA Sci & Technol Corp Ames Res Ctr Moffett Field CA 94035 USA Parallel Geometr Algorithms LLC Sunnyvale CA USA US Army CCDC AvMC Technol Dev Directorate TDD Moffett Field CA USA

Anisotropic prismatic/strand meshes are often used to capture viscous boundary layer effects in Reynolds Averaged Navier Stokes (RANS) simulations of high Reynolds number flows. This paper describes a new algorithm for generation of prismatic meshes using the minimum distance field of the surface tessellation. The algorithm starts with initial point placement using both the direction of best visibility and the direction to the closest point on the minimum distance iso-surface. Initial point placement is followed by a constrained smoothing operation based on an elastic spring analogy. The constraints ensure movement of nodes is restricted to the iso-surface of the distance field and within the region of visibility. Simulations are performed using a dual-mesh infrastructure, where the prismatic meshes transition to a Cartesian background mesh a short distance from the wall. This overset mesh system is processed by a domain connectivity method to establish connections between self-intersecting strand meshes and strand/Cartesian mesh systems. Mesh and flow simulation results are presented for test cases of varying complexity. (C) 2020 Elsevier Ltd. All rights reserved.

关键词： Computational Fluid Dynamics Mesh Generation Computational geometry

来源：评论

学校读者我要写书评

暂无评论

Wind farm simulations using an overset hp-adaptive approach with blade-resolved turbine models

引用

INTERNATIONAL JOURNAL OF HIGH PERFORMANCE COMPUTING APPLICATIONS 2019年第5期33卷 897-923页

作者： Kirby, Andrew C. Brazell, Michael J. Yang, Zhi Roy, Rajib Ahrabi, Behzad R. Stoellinger, Michael K. Sitaraman, Jay Mavriplis, Dimitri J. Univ Wyoming Dept Mech Engn Laramie WY 82071 USA Parallel Geometr Algorithms LLC Sunnyvale CA USA

Blade-resolved numerical simulations of wind energy applications using full blade and tower models are presented. The computational methodology combines solution technologies in a multi-mesh, multi-solver paradigm through a dynamic overset framework. The coupling of a finite volume solver and a high-order, hp-adaptive finite element solver is utilized. Additional technologies including in-situ visualization and atmospheric microscale modeling are incorporated into the analysis environment. Validation of the computational framework is performed on the National Renewable Energy Laboratory (NREL) 5MW baseline wind turbine, the unsteady aerodynamics experimental NREL Phase VI turbine, and the Siemens SWT-2.3-93 wind turbine. The power and thrust results of all single turbine simulations agree well with low-fidelity model simulation results and field experiments when available. Scalability of the computational framework is demonstrated using 6, 12, 24, 48, and 96 wind turbine setups including the 48 turbine wind plant known as Lillgrund. The largest case consisting of 96 wind turbines and a total of 385 overset grids are run on 44,928 cores at a weak scaling efficiency of 86%. Demonstration of the coupling of atmospheric microscale and Computational Fluid Dynamics (CFD) solvers is presented using the National Center for Atmospheric Research (NCAR) Weather Research and Forecasting Model (WRF) solver and the NREL Simulator fOr Wind Farm Applications (SOWFA) solver.

关键词： High performance computing wind energy overset grids high-order methods discontinuous Galerkin

来源：评论

学校读者我要写书评

暂无评论

An overset generalised minimal residual method for the multi-solver paradigm

引用

INTERNATIONAL JOURNAL OF COMPUTATIONAL FLUID DYNAMICS 2020年第1期34卷 61-74页

作者： Jude, Dylan Sitaraman, Jayanarayanan Lakshminarayan, Vinod Baeder, James Ames Res Ctr Moffett Field CA 94035 USA Univ Maryland Dept Aerosp Engn College Pk MD 20742 USA Sci & Technol Corp Moffett Field CA 94035 USA Parallel Geometr Algorithms LLC Moffett Field CA USA

The multi-mesh, multi-solver paradigm makes use of multiple Computational Fluid Dynamics (CFD) solvers in a single overset framework. A framework-level implementation of the Generalised Minimal Residual algorithm applied to the full implicit overset system is presented. The method requires only minimal changes to existing, Python-wrapped CFD solvers and demonstrates improved convergence compared to traditional methods. Preliminary validation for the method is performed using the Poisson equation on two overset grids. The multi-body, overset GMRES method is shown to be equivalent to a conventional implementation which allocates memory for data across all overset grids on a single processor. Results are shown for two time-accurate flow simulations. The first case analyses convergence of a 2D inviscid wedge and the second analyses convergence of a laminar 3D sphere. Both the wedge and sphere bodies shed unsteady structures into nested, background Cartesian grids. In both unsteady cases, the presented overset GMRES method demonstrates superior convergence over traditional methods.

关键词： Overset GMRES finite volume method convergence acceleration dual-mesh paradigm GPU

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：