Turbulence models with adaptive meshing for industrial CFD

Computational fluid dynamics (CFD) and affordable computing power have advanced considerably in recent years, bringing full 3D simulation of complex high Reynolds number flows within reach of industry. However, providing accurate and trustworthy results in diverse flows with constraints on computational resources is still a considerable challenge. Owing to the complexity of commonly-encountered turbulent flows, robust turbulence models are required which do not have to be manually tuned to specific flow conditions to ensure their accuracy. In this regard, a highly effective approach is unstructured mesh adaptivity which automatically refines or coarsens the mesh locally in order to achieve a desired accuracy with minimum computational effort. However, the use of such adaptive meshes with turbulence models raises questions about the origins and interactions of various errors. This thesis describes the development, verification and validation of robust turbulence models suited to high Reynolds number single-phase turbulent flow using unstructured adaptive meshes. The main focus of this thesis is a new tensorial dynamic large eddy simulation (LES) model. The novel combination of the dynamic LES method with a tensorial definition of filter width is ideal for capturing the anisotropy and inhomogeneity of turbulence. This model is designed for use with unstructured mesh adaptivity, which enables the simulation of turbulent flow with high efficiency in terms of mesh resolution. Furthermore, the model is robust since both the resolution and the sub-filter-scale (SFS) stresses adapt to local flow conditions so that little a priori knowledge of the flow is required. Verification tests of the filtering method and validation of the new LES model in the 3D backward-facing step are presented. To provide context for the research, the contribution made by CFD simulations to the analysis of nuclear reactor safety and performance is discussed. The practicalities of performing simulations on high performance computing (HPC) facilities are also discussed. Background theory necessary to understand the research is presented, including a mathematical description of turbulent flow and the classes of CFD methods used to approximate it. A review of turbulence models, discretisation methods, boundary conditions and adaptive meshing methods is included. The construction and testing of a Reynolds-averaged Navier-Stokes (RANS) k - ε turbulence model and a scale-adaptive very large eddy simulation (VLES) model in the open-source CFD code Fluidity are also described. The development of a law-of-the-wall boundary condition for turbulent flow in variational (weak) form is also presented. Verification tests are performed to establish that the k - ε model has been coded correctly. Validation of the RANS model and the wall function using fixed and adaptive meshes is carried out in the 2D backward-facing step. Finally, results of simulations of a vortex diode device using various turbulence models are presented and compared to results from the commercial CFD code CFX and experimental results. This study was carried out during the industrial component of the Engineering Doctorate, which was intended to further the development and understanding of CFD at Rolls-Royce Nuclear. The device presents a challenging test case for CFD but some useful conclusions are reached about how to model it. The thesis concludes with a summary of findings and proposals for further research

Proceedings, MSVSCC 2015

The Virginia Modeling, Analysis and Simulation Center (VMASC) of Old Dominion University hosted the 2015 Modeling, Simulation, & Visualization Student capstone Conference on April 16th. The Capstone Conference features students in Modeling and Simulation, undergraduates and graduate degree programs, and fields from many colleges and/or universities. Students present their research to an audience of fellow students, faculty, judges, and other distinguished guests. For the students, these presentations afford them the opportunity to impart their innovative research to members of the M&S community from academic, industry, and government backgrounds. Also participating in the conference are faculty and judges who have volunteered their time to impart direct support to their students’ research, facilitate the various conference tracks, serve as judges for each of the tracks, and provide overall assistance to this conference. 2015 marks the ninth year of the VMASC Capstone Conference for Modeling, Simulation and Visualization. This year our conference attracted a number of fine student written papers and presentations, resulting in a total of 51 research works that were presented. This year’s conference had record attendance thanks to the support from the various different departments at Old Dominion University, other local Universities, and the United States Military Academy, at West Point. We greatly appreciated all of the work and energy that has gone into this year’s conference, it truly was a highly collaborative effort that has resulted in a very successful symposium for the M&S community and all of those involved. Below you will find a brief summary of the best papers and best presentations with some simple statistics of the overall conference contribution. Followed by that is a table of contents that breaks down by conference track category with a copy of each included body of work. Thank you again for your time and your contribution as this conference is designed to continuously evolve and adapt to better suit the authors and M&S supporters. Dr.Yuzhong Shen Graduate Program Director, MSVE Capstone Conference Chair John ShullGraduate Student, MSVE Capstone Conference Student Chai

Aeronautical Engineering. A continuing bibliography with indexes, supplement 156

This bibliography lists 288 reports, articles and other documents introduced into the NASA scientific and technical information system in December 1982