5,100 research outputs found
Computation of three-dimensional flows using two stream functions
An approach to compute 3-D flows using two stream functions is presented. The method generates a boundary fitted grid as part of its solution. Commonly used two steps for computing the flow fields are combined into a single step in the present approach: (1) boundary fitted grid generation; and (2) solution of Navier-Stokes equations on the generated grid. The presented method can be used to directly compute 3-D viscous flows, or the potential flow approximation of this method can be used to generate grids for other algorithms to compute 3-D viscous flows. The independent variables used are chi, a spatial coordinate, and xi and eta, values of stream functions along two sets of suitably chosen intersecting stream surfaces. The dependent variables used are the streamwise velocity, and two functions that describe the stream surfaces. Since for a 3-D flow there is no unique way to define two sets of intersecting stream surfaces to cover the given flow, different types of two sets of intersecting stream surfaces are considered. First, the metric of the (chi, xi, eta) curvilinear coordinate system associated with each type is presented. Next, equations for the steady state transport of mass, momentum, and energy are presented in terms of the metric of the (chi, xi, eta) coordinate system. Also included are the inviscid and the parabolized approximations to the general transport equations
Economic Sizing of Distributed Energy Resources for Reliable Community Microgrids
Community microgrids offer many advantages for power distribution systems.
When there is an extreme event happening, distribution systems can be
seamlessly partitioned into several community microgrids for uninterrupted
supply to the end-users. In order to guarantee the system reliability,
distributed energy resources (DERs) should be sized for ensuring generation
adequacy to cover unexpected events. This paper presents a comprehensive
methodology for DERs selection in community microgrids, and an economic
approach to meet the system reliability requirements. Algorithms of discrete
time Fourier transform (DTFT) and particle swarm optimization (PSO) are
employed to find the optimal solution. Uncertainties of load demand and
renewable generation are taken into consideration. As part of the case study, a
sensitivity analysis is carried out to show the renewable generation impact on
DERs' capacity planning.Comment: 5 pages, 6 figures, 1 table, 2017 IEEE Power & Energy Society General
Meeting. arXiv admin note: substantial text overlap with arXiv:1708.0102
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