Tidally averaged circulation in Puget Sound sub-basins: Comparison of historical data, analytical model, and numerical model

Medium-frequency (MF) transformer has gained much popularity in power conversion systems. Temperature control is a paramount concern, as the unexpected high temperature declines the safety and life expectancy of transformer. The scrutiny of losses and thermal-fluid behavior are thereby critical for the design of MF transformers. This paper proposes a coupled, semi-numerical model for electromagnetic and thermal-fluid analysis of MF oil natural air natural (ONAN) transformer. An analytical model that is based on spatial distribution of flux density and AC factor is exploited to calculate the system losses, while the thermal-hydraulic behavior is modelled numerically leveraging the computational fluid dynamics (CFD) method. A close-loop iterative framework is formulated by coupling the analytical model-based electromagnetic analysis and CFD-based thermal-fluid analysis to address the temperature dependence. Experiments are performed on two transformer prototypes with different conductor types and physical geometries for validation purpose. Results suggest that the proposed model can accurately model the AC effects, losses, and the temperature rises at different system components. The proposed model is computationally more efficient than the full numerical method but it reserves accurate thermal-hydraulic characterization, thus it is promising for engineering utilization.

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Bistable regimes in an elastic tensegrity system

Proceedings of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rspa.2013.0052 ◽

2013 ◽

Vol 469 (2154) ◽

pp. 20130052 ◽

Cited By ~ 27

Author(s):

Andrea Micheletti

Keyword(s):

Numerical Model ◽

Analytical Model ◽

The Other ◽

Initial Deformation ◽

Reduced Order ◽

Tensegrity Systems ◽

Elastic Elements

Tensegrity systems are prestressed frameworks composed of bars and cables. A particular elastic tensegrity system is examined. This system can be bistable in two fundamentally different ways, one depending on its geometric dimensions, and the other one depending on the initial deformation, or prestrain, of the elastic elements. A reduced-order semi-analytical model is derived, and its predictions are verified with a full-order numerical model. In particular, the critical geometry and prestrain at which the system switches from one regime to another are determined. This case study provides a benchmark and new insights on this class of structures.

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Multi-layered diffusive convection. Part 2. Dynamics of layer evolution

Journal of Fluid Mechanics ◽

10.1017/s0022112010994160 ◽

2010 ◽

Vol 651 ◽

pp. 465-481 ◽

Cited By ~ 7

Author(s):

TAKASHI NOGUCHI ◽

HIROSHI NIINO

Keyword(s):

Numerical Simulation ◽

Numerical Model ◽

Direct Numerical Simulation ◽

Analytical Model ◽

The Other ◽

One Dimensional ◽

Turbulent Entrainment ◽

Diffusive Convection ◽

Two Component

Evolution of layers in an unbounded diffusively stratified two-component fluid and its dynamics are studied by means of a direct numerical simulation (DNS) and an analytical model. The numerical simulation shows that the layers grow by repeating mergings with the neighbouring layers. By analysing the results of the numerical simulation, the mechanism of the merging is examined in detail. Two modes of merging are found to exist: one is the layer vanishing mode and the other is the interface vanishing mode. The vanishings of layers and interfaces are caused by turbulent entrainment at the interfaces. Based on the analysis of the numerical model, a one-dimensional asymmetric entrainment model is proposed. In the model, each layer is assumed to interact with its neighbouring layers through simplified convective entrainment laws. The model is applied to two simple configurations of layers and is proved to reproduce the layer evolutions found in the DNS successfully.

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Transport Modelling of Copper Contamination in Groundwater Caused by a Wood Preservation Plant

Water Quality Research Journal ◽

10.2166/wqrj.2005.050 ◽

2005 ◽

Vol 40 (4) ◽

pp. 469-475 ◽

Cited By ~ 1

Author(s):

Mustafa Tombul ◽

Ali Savaş Koparal ◽

Ülker Bakır Öğütveren

Keyword(s):

Numerical Model ◽

Analytical Model ◽

Carrier Transport ◽

Copper Concentration ◽

Analytical Models ◽

Wood Preservation ◽

Measured Quantity ◽

Copper Contamination ◽

Transport Modelling ◽

Effect Of Copper

Abstract Contaminants can adhere to soil and subsequent rainfall can leach the adhered contaminant into groundwater. Transport models can determine the main features of contaminant and carrier transport in groundwater systems, and therefore determine potential risks for public health and ecosystems. In this study, the effect of copper contamination caused by a wood preservation plant near Eskişehir, Turkey, on the possible pollution of drinking water supply wells was investigated with two different models. The first model, which deals with the movement of contaminants to groundwater, is a numerical model known as Flonet/Trans (Waterloo Hydrogeologic 1997). It has been used to investigate the change in contaminants from the source with respect to time and distance. The second model, which measures contaminant movement with respect to time and distance through simulations, is an analytical model known as Multi-Flow. It was used for verification of the first model. Both numerical and analytical models have been successfully applied at the work area for investigation of the effects of copper contamination in groundwater. Using the numerical model, the copper concentration in the first observation well was found to be 1.59 mg L-1, and using the analytical model, the copper concentration was found to be 1.35 mg L-1 after 550 days. The measured quantity was 2.11 mg L-1, thus the analytical model is best used for verification of results obtained by simulations of the numerical model.

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THE DYNAMICS OF OSCILLATING SHEETFLOW

Coastal Engineering Proceedings ◽

10.9753/icce.v20.71 ◽

1986 ◽

Vol 1 (20) ◽

pp. 71 ◽

Cited By ~ 5

Author(s):

W.T. Bakker ◽

W.G.M. Van Kesteren

Keyword(s):

Boundary Layer ◽

Numerical Model ◽

Turbulent Boundary Layer ◽

Analytical Model ◽

Darcy Law ◽

Elastic Response ◽

Sheet Flow ◽

Grain Interaction ◽

Spherical Grains ◽

Intrusion Depth

Two mathematical models for the simulation of the dynamics of sheetflow are presented, an analytical and a numerical one. In the analytical model the theory of Bagnold (1954) is implemented: a constant ratio between shear stress and normal stresses is assumed. In the numerical model the motion of each layer of grains is considered separately; each layer exists of a rigid rectangular structure of spherical grains. Grain- grain interaction between the successive layers occurs in two ways: on one hand viscous interaction forces, comparable with squeezing forces in lubrication problems and on the other hand direct contact with elastic response when the distance between the grains becomes less than .01 of the grain diameter. When the relative motion of adjacent layers results into compression or dilatation, a resistant force analogous to the Darcy law is assumed.The numerical model has been combined with the turbulent boundary layer model of Bakker and v. Kesteren (1984). Results of computations are compared with measurements of Bagnold (1954) and Horikawa et al (1982). The analytical model predicted the concentration in the sheet flow layer and the intrusion depth rather well, where the numerical model gave reasonable results with respect to the velocity pattern above the sheetflow layer. It is concluded, that up to now the more sophisticated assumptions of the numerical model do not lead as yet to higher accuracy with respect to the intrusion depth of the sheet flow, probably because the separation between sheet flow and the turbulent boundary layer above has been assumed too smooth.

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Analytical and Numerical Simulation of Asymmetric Converging Flow of Gas under Drill Bits in Reverse Circulation Gas Drilling

Journal of Energy Resources Technology ◽

10.1115/1.4051551 ◽

2021 ◽

pp. 1-11

Author(s):

Xu Yang ◽

Boyun Guo ◽

Tamaralayefa Timiyan

Keyword(s):

Numerical Model ◽

Analytical Model ◽

Gas Flow ◽

Relative Difference ◽

Structure Design ◽

Drill Bit ◽

Drill Cuttings ◽

Gas Drilling ◽

Reverse Circulation ◽

Converging Flow

Abstract Reverse circulation gas drilling has been considered to solve engineering problems such as formation water influx, wellbore instability, and excess gas requirement in gas drilling. The performance of reverse circulation gas drilling depends to a large extent on the structure design of drill bit. An analytical model and a numerical model were developed in this study to simulate the asymmetric converging flow of gas under drill bit for reverse circulation gas drilling. The two models were compared and applied to the evaluation of a drill bit structure design for bottom hole cleaning capacity of gas flow. It was found that the pressure, velocity, and specific kinetic energy given by the analytical model are slightly lower than that given by the numerical model. The relative difference between the gas flow rates given by the analytical model and the numerical model is less than 5%. For the drill bit structure design considered in this study, the gas flow energy between the short blades is much higher than that between the long blades. A gas injection rate of 10 m3/min (360 ft3/min) is expected to clean the drill cuttings between the short blades, while a gas flow rate of 28 m3/min (990 ft3/min) is required to clean the drill cuttings between the long blades. Although the numerical model gives more accurate result than the analytical model in predicting hydraulics parameters, the analytical model is recommended for evaluating drill bit structure design because of its simplicity and conservativeness.

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Abundance of an economically important nematode parasite increased in Puget Sound between 1930 and 2016: Evidence from museum specimens confirms historical data

Journal of Applied Ecology ◽

10.1111/1365-2664.13264 ◽

2018 ◽

Vol 56 (1) ◽

pp. 190-200 ◽

Cited By ~ 4

Author(s):

Ingrid Howard ◽

Ellie Davis ◽

Gregory Lippert ◽

Thomas P. Quinn ◽

Chelsea L. Wood

Keyword(s):

Historical Data ◽

Puget Sound ◽

Nematode Parasite ◽

Museum Specimens

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Finite Element Analysis of the Effect of Currents on the Dynamics of a Moored Flexible Cylindrical Net Cage

Journal of Marine Science and Engineering ◽

10.3390/jmse9020159 ◽

2021 ◽

Vol 9 (2) ◽

pp. 159

Author(s):

Zhongchi Liu ◽

Sarat Chandra Mohapatra ◽

C. Guedes Soares

Keyword(s):

Finite Element Analysis ◽

Finite Element ◽

Numerical Model ◽

Analytical Model ◽

Structural Response ◽

Wave Theory ◽

Design Parameters ◽

Element Analysis ◽

Net Cage ◽

Comparison Of The Results

A numerical model associated with wave–current interactions with a moored flexible cylindrical cage was developed based on the finite element method. An analytical model was formulated under the linearised wave theory and small structural response, and a semi-analytical solution was obtained using the Fourier Bessel series solution and least squares approximation method, along with a matching technique. The numerical results from the finite element analysis of the horizontal displacements for different design parameters under a uniform current were compared with the analytical model solutions. It was seen that they had a good level of agreement with their results. The effects of different current speeds and time on the cage shapes were analysed from the finite element results. Further, the mooring forces on the flexible cage for different values of the cage height and cage radius were also presented. The comparison of the results indicated that the numerical model results could be used with confidence in the design of a flexible cylindrical net cage for applications to offshore aquacultures.

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