Tidal currents and mixing in the Gulf of St. Lawrence: an application of the incremental approach to data assimilation

2001 ◽  
Vol 58 (4) ◽  
pp. 723-735 ◽  
Author(s):  
Youyu Lu ◽  
Keith R Thompson ◽  
Daniel G Wright
Keyword(s):  
Data Assimilation ◽  
Three Dimensional ◽  
Tidal Currents ◽  
Tide Gauges ◽  
Three Dimensional Model ◽  
Density Profiles ◽  
Water Column Stability ◽  
Incremental Approach ◽  
Tidal Frequency ◽  
Good Agreement

Tidal heights from 19 tide gauges around the Gulf of St. Lawrence are assimilated into a fully nonlinear, three-dimensional model using the incremental approach to data assimilation. The predicted sea level fields are realistic and agree with the assimilated tidal heights to within about 0.05 m at the M2 tidal frequency. The model also predicts tidal currents with useful skill. The prediction error at the M2 tidal frequency is typically less than 0.05 m·s–1. The maps of predicted tidal currents are used to identify regions of mixed and stratified water in the Gulf of St. Lawrence using a version of the Simpson–Hunter stability parameter, E. Overall, the map of E is in good agreement with a direct measure of water column stability based on observed density profiles.

Use of a three-dimensional model to predict heavy metal (copper) fluxes in the Oujiang estuary

2014 ◽  
Vol 69 (6) ◽  
pp. 1334-1343 ◽  
Author(s):  
Shasha Lu ◽  
Ruijie Li ◽  
Xiaoming Xia ◽  
Jun Zheng
Keyword(s):  
River Discharge ◽  
Water Surface ◽  
Three Dimensional ◽  
Measured Data ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Pollutant Concentrations ◽  
Suspended Sediment Concentrations ◽  
Adsorption Desorption ◽  
Good Agreement

Measuring pollutant concentrations in major tributaries is the standard method for establishing pollutant fluxes to the sea. However, this method is costly and difficult, and may be subject to a great deal of uncertainty due to the presence of unknown sources. This uncertainty presents challenges to managers and scientists in reducing contaminant discharges to water bodies. As one less costly method, a three-dimensional model was developed and used to predict pollutant fluxes to the sea. The sorptive contaminant model was incorporated into hydrodynamic and sediment models. Adsorption–desorption of copper by sediments in the Oujiang estuary were described using Henry's law. The model was validated using measured data for water surface elevations, flow velocity/direction, suspended sediment concentrations, and the proportion of copper sorbed to sediment. The validated model was then applied to predict fluxes of copper. Combined with the measured data, the copper concentration in the Oujiang River discharge was calculated as 13.0 μg/L and copper fluxes were calculated as 52 t in 2010. This copper flux prediction was verified using measured dissolved copper concentrations. Comparisons between the modeled and measured results showed good agreement at most stations, demonstrating that copper flux prediction in the Oujiang estuary was reasonably accurate.

A System of Selective Non Catalytic Reduction of NOx for Diesel Engine

2011 ◽  
Vol 201-203 ◽  
pp. 643-646 ◽  
Author(s):  
Bo Yan Xu ◽  
Hai Ying Tian ◽  
Jie Yang ◽  
De Zhi Sun ◽  
Shao Li Cai
Keyword(s):  
Catalytic Reduction ◽  
Three Dimensional ◽  
Exhaust Gas ◽  
Test Results ◽  
Practical Application ◽  
Three Dimensional Model ◽  
Reduction Efficiency ◽  
Different Temperatures ◽  
Reduction Of Nox ◽  
Good Agreement

SNCR (Selective Non Catalytic Reduction) system is proposed, with 40% methylamine aqueous solution as reducing agent to reduce NOx in diesel exhaust gas. The effect of injection position and volume on the reduction efficiency through the test bench is systematically researched. A three-dimensional model of a full-sized diesel SNCR system generated by CFD software FIRE is used to investigate the reduction efficiency under different temperatures. The simulated results have a good agreement with the test results, and it can be used to optimize SNCR system. The results can indicate the practical application of this technology.

scholarly journals Forecasting of Surface Currents via Correcting Wind Stress with Assimilation of High-Frequency Radar Data in a Three-Dimensional Model

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Lei Ren ◽  
Stephen Nash ◽  
Michael Hartnett
Keyword(s):  
Data Assimilation ◽  
High Frequency ◽  
Three Dimensional ◽  
Hf Radar ◽  
Surface Velocity ◽  
Shear Stresses ◽  
Surface Currents ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
The Impact

This paper details work in assessing the capability of a hydrodynamic model to forecast surface currents and in applying data assimilation techniques to improve model forecasts. A three-dimensional model Environment Fluid Dynamics Code (EFDC) was forced with tidal boundary data and onshore wind data, and so forth. Surface current data from a high-frequency (HF) radar system in Galway Bay were used for model intercomparisons and as a source for data assimilation. The impact of bottom roughness was also investigated. Having developed a “good” water circulation model the authors sought to improve its forecasting ability through correcting wind shear stress boundary conditions. The differences in surface velocity components between HF radar measurements and model output were calculated and used to correct surface shear stresses. Moreover, data assimilation cycle lengths were examined to extend the improvements of surface current’s patterns during forecasting period, especially for north-south velocity component. The influence of data assimilation in model forecasting was assessed using a Data Assimilation Skill Score (DASS). Positive magnitude of DASS indicated that both velocity components were considerably improved during forecasting period. Additionally, the improvements of RMSE for vector direction over domain were significant compared with the “free run.”

Rotational temperature profiles of shock waves in diatomic gases

1971 ◽  
Vol 49 (2) ◽  
pp. 337-351 ◽  
Author(s):  
A. K. Macpherson
Keyword(s):  
Shock Waves ◽  
Rotational Temperature ◽  
Rotational Velocity ◽  
Three Dimensional ◽  
Intermolecular Potential ◽  
Collision Dynamics ◽  
Density Profiles ◽  
Frequency Distributions ◽  
Dimensional Approximation ◽  
Good Agreement

The variation of the translational temperature, rotational temperature, and density through shock waves in oxygen and nitrogen was studied using classical laws of mechanics and a Monte Carlo scheme. The collision dynamics were calculated using an intermolecular potential by Parker with both a two-dimensional approximation and the full three-dimensional calculations. The rotational velocity frequency distributions were also calculated. The average number of collisions a molecule will experience a t various stages passing through a shock wave were found and plotted with the temperature and density profiles. The nitrogen results were compared with experimental results and good agreement was found. This also provided a method for giving a first approximation to the three-dimensional intermolecular potential.

Waves of Acoustically Induced Transparency in Bubbly Liquids: Theoretical Prediction and Experimental Validation

2013 ◽  
Author(s):  
Nail A. Gumerov ◽  
Iskander S. Akhatov ◽  
Claus-Dieter Ohl ◽  
Sergei P. Sametov ◽  
Maxim V. Khasimulin ◽  
...  
Keyword(s):  
Acoustic Field ◽  
Acoustic Waves ◽  
Three Dimensional ◽  
Self Organization ◽  
Nonlinear Phenomenon ◽  
Three Dimensional Model ◽  
Bubbly Liquids ◽  
Strongly Nonlinear ◽  
Induced Transparency ◽  
Good Agreement

Self-organization of bubbles in acoustic fields, or self-action of the acoustic waves in bubbly liquids is a strongly nonlinear phenomenon due to two-way interaction of the bubbles and the acoustic field. Theoretical model and preliminary computations predict that waves of self-induced acoustic transparency may exist. Such effect is confirmed in the experiments presented in this paper. Formation of a wave of void fraction which rapidly propagates through the bubbly medium leaving a region almost free of bubbles behind its front is observed in the experiments. Measurements of the dynamics of such a wave at different acoustic frequencies and amplitudes are carried out. A three dimensional model of self-organization of a polydisperse bubble continuum in acoustic field is developed and the results of simulations are compared with experiments. A good agreement of the theory and experiment is found.

A three-dimensional model of the human airway tree

1999 ◽  
Vol 87 (6) ◽  
pp. 2207-2217 ◽  
Author(s):  
Hiroko Kitaoka ◽  
Ryuji Takaki ◽  
Béla Suki
Keyword(s):  
3D Model ◽  
Human Lung ◽  
Three Dimensional ◽  
Deterministic Algorithm ◽  
Three Dimensional Model ◽  
Fluid Delivery ◽  
Human Airway ◽  
Airway Tree ◽  
Function Relationship ◽  
Good Agreement

A three-dimensional (3D) model of the human airway tree is proposed using a deterministic algorithm that can generate a branching duct system in an organ. The algorithm is based on two principles: 1) the amount of fluid delivery through a branch is proportional to the volume of the region it supplies; and 2) the terminal branches are arranged homogeneously within the organ. These principles define the basic process of branching: generation of the dimensions and directionality of two daughter branches is governed by the properties of the parent branch and the region the parent supplies. The algorithm is composed of nine basic rules and four complementary rules. When the contour of an organ and the position of the trunk are specified, branches are successively generated by the algorithm. Applied to the human lung, the algorithm generates an airway tree that consists of ∼54,000 branches. Its morphometric characteristics are in good agreement with those reported in the literature. The algorithm and the 3D airway model are useful for studying the structure-function relationship in the lung.

The Prediction of Surface Discharge Jets by a Three-Dimensional Finite-Difference Model

1980 ◽  
Vol 102 (1) ◽  
pp. 138-145 ◽  
Author(s):  
G. D. Raithby ◽  
G. E. Schneider
Keyword(s):  
Finite Difference ◽  
Three Dimensional ◽  
Design Tool ◽  
Surface Discharge ◽  
Three Dimensional Model ◽  
Finite Difference Solution ◽  
Surface Discharges ◽  
Semi Empirical ◽  
Heated Jet ◽  
Good Agreement

A three-dimensional model is presented which describes the thermal and hydrodynamic behavior of a turbulent heated jet entering at the surface of a receiving body of water. A two-equation turbulence model, together with a semi-empirical description of the preferential attenuation of vertical turbulent exchange due to buoyancy, is used to predict non-isotropic turbulent diffusivities. A finite-difference solution method, involving several novel features, has been used. Predictions are compared with both field and laboratory measurements, for both deep and shallow receiving basins, for the special case of a quiescent ambient fluid. Good agreement is found, indicating that the model can be reliably used as a design tool, or to evaluate the environmental impact of surface discharges.

Temperature Field Measuring and Simulation of CMSX-6 Superalloy during Directional Solidification

2015 ◽  
Vol 723 ◽  
pp. 561-564
Author(s):  
Zhi Hong Jia ◽  
Liang Xu ◽  
Ran Tao ◽  
Ming Zhe Ma ◽  
Dao Cun Xie ◽  
...  
Keyword(s):  
Temperature Field ◽  
Temperature Gradient ◽  
Directional Solidification ◽  
Three Dimensional ◽  
Solidification Process ◽  
Three Dimensional Model ◽  
Directional Solidification Process ◽  
Withdrawal Velocity ◽  
Field Measuring ◽  
Good Agreement

A three-dimensional model of CMSX-6 superalloy coupons was built in the paper, temperature field was calculated with software ProCAST. The temperature values of coupons were indicated from the measurement at the rate of 3 mm min-1 withdrawal velocity during directional solidification process, and the temperature gradient of different location of the coupons were calculated. It turned out that: the simulated results and the measured results are in good agreement; due to the different medial and lateral affected by radiation, isotherms showed sloped distributions in the process of the withdrawal; the temperature gradient of the measured positions in the coupons which are 10 mm, 50 mm, 100 mm, 150 mm far from the copper chill, are 8.0 Kmm-1, 3.0 Kmm-1, 2.5 Kmm-1, 1.8 Kmm-1 respectively.

A Three Dimensional Model for Generating the Texture in B-Scan Ultrasound Images

1983 ◽  
Vol 5 (3) ◽  
pp. 253-279 ◽  
Author(s):  
Mitchell M. Goodsitt ◽  
Ernest L. Madsen ◽  
James A. Zagzebski
Keyword(s):  
Three Dimensional ◽  
Time Dependent ◽  
Ultrasound Images ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Gray Scale ◽  
Receiver System ◽  
Gray Scale Image ◽  
Theory And Experiment ◽  
Good Agreement

A three-dimensional model for production of gray scale texture in ultrasound B-mode images is described. The model computes time-dependent echo signals resulting from scattering of acoustic pulses by particles randomly distributed in an attenuating medium and transforms these signals into a gray scale image. Specific transducer and pulser-receiver characteristics are accounted for, as well as the three-dimensional nature of the problem, without loss of computational efficiency. The model generates texture that closely corresponds to that found experimentally in ultrasound images of tissue-mimicking phantoms. The dependence of the texture upon the depth of the region that was scanned and on the characteristics of the transducer-receiver system were clearly demonstrated. Good agreement between theory and experiment was found for the texture in phantoms containing simulated spherical low-scatter tumors.

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