197 research outputs found
Implementation and Verification of a Synthetic Eddy Method (SEM) in the Eagle3d Compressible Flow Solver
The objective of this thesis is to implement and evaluate a Synthetic Eddy Method (SEM) into the Eagle3D compressible ow solver. Both the ability of Eagle3D to resolve unsteady turbulent ow field and capability of the SEM to reproduce given Reynolds stress profiles to start realistic turbulent behavior are verified using common academic cases. Eagle3D is a Computational Fluid Dynamics (CFD) solver using a novel combination of a Bounded Central Differencing (BCD) scheme with Weighted Essentially Non-Oscillatory (WENO) approximation to reduce numerical dissipation. SEM is a modern synthetic turbulence method able to reproduce an arbitrary Reynolds stresses specification on discretionary geometries while keeping computational costs low. The Large-Eddy Simulation (LES) capability of Eagle3D is evaluated using the flow over a cylinder and compared to results by ANSYS Fluent. The SEM is used to reproduce unsteady inlet conditions for channel and at plate cases and relayed into Eagle3D. Common ow parameters such as skin friction, Reynolds stresses and velocity components are compared against analytic, Direct Numerical Simulation (DNS) and periodic LES to estimate the performance of this solver combination in accuracy and development length. Parametric studies of grid dependence, varying upstream Reynolds-Averaged Naiver-Stokes (RANS) data and prescribed eddy length scale are performed. Modifications to the SEM are prescribed and tested where suitable. Further studies and modifications to the SEM based on the obtained data are suggested
Slow Down! Reducing Downtown Bloomington\u27s Progression Speed
A stated goal of the Citywide Retiming Project was to reduce the progression speed along the College Avenue and Walnut Street one-way pair through downtown Bloomington while improving signal coordination, increasing greenband, and providing clearance interval compliance. Pedestrian and bicycle safety was also taken into consideration. While it’s the same small town, this project has resulted in fewer stops, lower progression speed, and less driver frustration. This presentation details the before-and-after study, including the benefit-cost analysis
An Efficient Sliding Mesh Interface Method for High-Order Discontinuous Galerkin Schemes
Sliding meshes are a powerful method to treat deformed domains in
computational fluid dynamics, where different parts of the domain are in
relative motion. In this paper, we present an efficient implementation of a
sliding mesh method into a discontinuous Galerkin compressible Navier-Stokes
solver and its application to a large eddy simulation of a 1-1/2 stage turbine.
The method is based on the mortar method and is high-order accurate. It can
handle three-dimensional sliding mesh interfaces with various interface shapes.
For plane interfaces, which are the most common case, conservativity and
free-stream preservation are ensured. We put an emphasis on efficient parallel
implementation. Our implementation generates little computational and storage
overhead. Inter-node communication via MPI in a dynamically changing mesh
topology is reduced to a bare minimum by ensuring a priori information about
communication partners and data sorting. We provide performance and scaling
results showing the capability of the implementation strategy. Apart from
analytical validation computations and convergence results, we present a
wall-resolved implicit LES of the 1-1/2 stage Aachen turbine test case as a
large scale practical application example
Towards Exascale CFD Simulations Using the Discontinuous Galerkin Solver FLEXI
Modern high-order discretizations bear considerable potential for the
exascale era due to their high fidelity and the high, local computational load
that allows for computational efficiency in massively parallel simulations. To
this end, the discontinuous Galerkin (DG) framework FLEXI was selected to
demonstrate exascale readiness within the Center of Excellence for Exascale CFD
(CEEC) by simulating shock buffet on a three-dimensional wing segment at
transsonic flight conditions. This paper summarizes the recent progress made to
enable the simulation of this challenging exascale problem. For this, it is
first demonstrated that FLEXI scales excellently to over 500 000 CPU cores on
HAWK at the HLRS. To tackle the considerable resolution requirements near the
wall, a novel wall model is proposed that takes compressibility effects into
account and yields decent results for the simulation of a NACA 64A-110 airfoil.
To address the shocks in the domain, a finite-volume-based shock capturing
method was implemented in FLEXI, which is validated here using the simulation
of a linear compressor cascade at supersonic flow conditions, where the method
is demonstrated to yield efficient, robust and accurate results. Lastly, we
present the TensorFlow-Fortran-Binding (TFFB) as an easy-to-use library to
deploy trained machine learning models in Fortran solvers such as FLEXI.Comment: 15 pages, 5 figure
Observation of High-Energy Astrophysical Neutrinos in Three Years of IceCube Data
A search for high-energy neutrinos interacting within the IceCube detector
between 2010 and 2012 provided the first evidence for a high-energy neutrino
flux of extraterrestrial origin. Results from an analysis using the same
methods with a third year (2012-2013) of data from the complete IceCube
detector are consistent with the previously reported astrophysical flux in the
100 TeV - PeV range at the level of per flavor and reject a
purely atmospheric explanation for the combined 3-year data at .
The data are consistent with expectations for equal fluxes of all three
neutrino flavors and with isotropic arrival directions, suggesting either
numerous or spatially extended sources. The three-year dataset, with a livetime
of 988 days, contains a total of 37 neutrino candidate events with deposited
energies ranging from 30 to 2000 TeV. The 2000 TeV event is the highest-energy
neutrino interaction ever observed.Comment: 8 pages, 5 figures. Accepted by PRL. The event catalog, event
displays, and other data tables are included after the final page of the
article. Changed from the initial submission to reflect referee comments,
expanding the section on atmospheric backgrounds, and fixes offsets of up to
0.9 seconds in reported event times. Address correspondence to: J. Feintzeig,
C. Kopper, N. Whitehor
Theory and description in African Linguistics: Selected papers from the 47th Annual Conference on African Linguistics
The papers in this volume were presented at the 47th Annual Conference on African Linguistics at UC Berkeley in 2016. The papers offer new descriptions of African languages and propose novel theoretical analyses of them. The contributions span topics in phonetics, phonology, syntax, semantics, and pragmatics and reflect the typological and genetic diversity of languages in Africa. Four papers in the volume examine Areal Features and Linguistic Reconstruction in Africa, and were presented at a special workshop on this topic held alongside the general session of ACAL
Theory and description in African Linguistics: Selected papers from the 47th Annual Conference on African Linguistics
The papers in this volume were presented at the 47th Annual Conference on African Linguistics at UC Berkeley in 2016. The papers offer new descriptions of African languages and propose novel theoretical analyses of them. The contributions span topics in phonetics, phonology, syntax, semantics, and pragmatics and reflect the typological and genetic diversity of languages in Africa. Four papers in the volume examine Areal Features and Linguistic Reconstruction in Africa, and were presented at a special workshop on this topic held alongside the general session of ACAL
Theory and description in African Linguistics: Selected papers from the 47th Annual Conference on African Linguistics
The papers in this volume were presented at the 47th Annual Conference on African Linguistics at UC Berkeley in 2016. The papers offer new descriptions of African languages and propose novel theoretical analyses of them. The contributions span topics in phonetics, phonology, syntax, semantics, and pragmatics and reflect the typological and genetic diversity of languages in Africa. Four papers in the volume examine Areal Features and Linguistic Reconstruction in Africa, and were presented at a special workshop on this topic held alongside the general session of ACAL
Theory and description in African Linguistics: Selected papers from the 47th Annual Conference on African Linguistics
The papers in this volume were presented at the 47th Annual Conference on African Linguistics at UC Berkeley in 2016. The papers offer new descriptions of African languages and propose novel theoretical analyses of them. The contributions span topics in phonetics, phonology, syntax, semantics, and pragmatics and reflect the typological and genetic diversity of languages in Africa. Four papers in the volume examine Areal Features and Linguistic Reconstruction in Africa, and were presented at a special workshop on this topic held alongside the general session of ACAL
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