Numerical Simulation of Artificial Purification System by Using Hydrostatic and FULL-3D Combined Model

2003 ◽  
Author(s):  
Tsuguki Kinoshita ◽  
Shigeru Tabeta ◽  
Masataka Fujino
Keyword(s):  
Numerical Simulation ◽  
Dynamic Pressure ◽  
Vertical Direction ◽  
Bottom Layer ◽  
Momentum Equation ◽  
3D Analysis ◽  
Combined System ◽  
Purification System ◽  
Hydrostatic Approximation ◽  
Mixed Water

Ohmura bay is a typical enclosed estuary located in Kyushu, Japan. In the summer season, strong stratification is formed which brings oxygen-dificient water mass in the bottom layer. For the purpose of restoring water quality in the bay, field experiment of an artificial purification system was carried out. In the experiment, a diffusion pump was installed on the bottom of the bay. The instrument draws in the surface water of lower density and rich oxygen, mixes it with the bottom water of higher density and poor oxygen, and diffuses the mixed water upward. The mixed water is expected to spread along the isopycnic as density current, which will cause resolution of anoxic water in the bottom layer and promote the circulation of nutrients. However, it cannot be said the experiment was successful, and detail analysis by numerical simulation should be necessary in order to design more effective purification system. Most of ocean models employ the hydrostatic approximation because the horizontal scale is usually much larger than the vertical scale in oceanic phenomena. In the hydrostatic approximation, dynamic pressure is neglected and momentum equation of vertical direction need not to be solved. But in the present case, around the purification system, hydrodynamic pressure is not negligible and momentum equation of vertical direction must to be solved (called FULL-3D here). In FULL-3D calculation the time of calculation is much longer compared with using hydrostatic approximation. It is almost impossible to calculate the flow of the whole Ohmura bay by FULL-3D approach. The authors developed a new type of ocean model for multi-scale analysis, which conducts hydrostatic analysis for phenomena in wide area and FULL-3D analysis for the detail flow around the interesting object simultaneously. In order to connect the hydrostatic region and FULL-3D region, nested grid system is employed. Using this combined system, the effect of purification system to the whole bay will be investigated accurately.

Unsteady Buoyant Jet Simulations Using Dynamic Connection Scheme of Hydrostatic and Non-Hydrostatic Zone

2010 ◽  
Author(s):  
Masanobu Hasebe ◽  
Shigeru Tabeta
Keyword(s):  
Large Scale ◽  
Dynamic Pressure ◽  
Vertical Direction ◽  
Computation Time ◽  
Hydrodynamic Pressure ◽  
Momentum Equation ◽  
Ocean Model ◽  
Computational Time ◽  
Buoyant Jet ◽  
Hydrostatic Approximation

Most of ocean models employ hydrostatic approximation because the horizontal scale is usually much larger than the vertical scale in oceanic phenomena. In hydrostatic approximation, dynamic pressure is neglected and the momentum equation in vertical direction needs not to be solved. But for the phenomena of buoyant jet from the sea bottom such as submarine groundwater discharge, hydrothermal plume and so on, hydrodynamic pressure cannot be neglected and the momentum equation of vertical direction must to be taken into account. Non-hydrostatic analysis requires so much computation time that it is usually difficult to calculate the current field in the wide ocean area by this approach. On the other hand, analysis assuming the hydrostatic approximation needs less computational time and usually gives reasonable results for large scale ocean phenomena such as tidal current. In the present study, the authors developed a new type of ocean model for multi-scale analysis, which conducts hydrostatic analysis for phenomena in wide area and non-hydrostatic analysis for the detail flow around the buoyant jet simultaneously. The application limit of hydrostatic approximation for ocean model was investigated, and a dynamic connection method of hydrostatic zone with non-hydrostatic zone was developed. By theoretical consideration employing parameter δ and ε which represent the ratio of grid size Δz to Δx and the ratio of vertical velocity to horizontal velocity, it was found that hydrostatic approximation can be applied if δε and ε2 are minute. To examine the developed method, simulations for lock-exchange problem and vertical jet under oscillating current were conducted. The result by the present model was similar to that of non-hydrostatic model in the case that hydrostatic approximation was applied on the area of δε<0.005 and ε2<0.005.

Multiple Vortex Body Vortex Numerical Simulation

2011 ◽  
Vol 328-330 ◽  
pp. 1755-1758
Author(s):  
Han Xiao Liu ◽  
Zhong Liu ◽  
Huai Liang Li ◽  
Xin Xin Feng ◽  
Zhen Zhong Xing
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Turbulence Intensity ◽  
Continuity Equation ◽  
Momentum Equation ◽  
Turbulent Intensity ◽  
Good Effect ◽  
Train Of Thought

In this paper, the continuity equation, momentum equation and the k-ε turbulence equation were introduced to simulate the flow field of the multiple vortex bodies in different spacing cases. Found that each vortex body had good effect in producing vortex, and the greater flow field spacing, the smaller the highest velocity; the turbulence intensity is increasing gradually from the former vortex body to the next one, and there may be a best spacing between the vortex bodies which makes the best turbulent intensity. All of these theories provide a train of thought for the turbulent coalescence mechanism.

Numerical Simulation of Gasoline Blending with Two Different Mixing Systems

2011 ◽  
Vol 317-319 ◽  
pp. 2107-2112
Author(s):  
Song Ying Chen ◽  
Fu Chao Xie ◽  
Jun Jie Mao
Keyword(s):  
Numerical Simulation ◽  
Reynolds Equation ◽  
Mixing Time ◽  
Three Dimensional ◽  
Momentum Equation ◽  
Moving Mesh ◽  
Mixing Models ◽  
Turbulent Model ◽  
Jet Mixing ◽  
Mixing Effects

Based on two different mixing systems: Rotary Jet Mixing (RJM) system and side-entering agitator, two kinds of three-dimensional gasoline components mixing models are established. The incompressible Reynolds equation is selected as the momentum equation and the algorithm of SIMPLE is used to simulate the jet facility. To get the mixing time, moving mesh and the standard k-ε turbulent model has been employed in the multiphase unsteady flow. The results show that the dead areas of RJM are less than side-entering agitator, and the mixing effects are much better. Furthermore, the mixing time of RJM is only 58.2s, which is 69.7% of Side-entering Agitator.

A Numerical Simulation of Fuel Premixing for PCCI Combustion by Direct Injection

2011 ◽  
Author(s):  
Tsuyoshi Kondo ◽  
Tsuguhiko Nakagawa
Keyword(s):  
Numerical Simulation ◽  
Diesel Engine ◽  
Direct Injection ◽  
Vertical Direction ◽  
General Purpose ◽  
Injection Timing ◽  
Injection Angle ◽  
Equivalent Ratio ◽  
Local Equivalent ◽  
The Rich

Diesel engine has some advantages that thermal efficiency is high and control response is fast. On the other hand, more particulate matter (PM) and nitrogen oxide (NOx) are contained in the exhaust gas of diesel engine. Premixed charge compression ignition (PCCI) combustion is proposed to reduce the PM and NOx. In the lean range of equivalent ratio, unburned fuel is left and in the rich range, PM and soot are generated. For the practical use of PCCI combustion, mixing fuel and air well is important under the low equivalent ratio of injection. In this study, the mixing characteristics of fuel and air in a cylinder were numerically evaluated. A numerical simulation was performed with general-purpose simulator. The fuel has been injected into the vertical direction of cylinder and injection angle has been defined as 0 degree. In order to express the collusion, impingement on the wall model, that defines behavior of a droplet impinged on the wall with the Weber number of a droplet, was applied. By the injection timing, standard deviation of local equivalent ratio at Top Dead Center (TDC) was plotted. In this study, Frequency of mixing in each cell statistically was observed to evaluate the fuel-air mixing degree. The authors have taken notice of the condition which can be reduced the amount of scatter in the distribution of local equivalent ratio.

Numerical Simulation of Multi-Field Coupling in Aqueous Humor Under the Condition of Dynamic Pressure

2019 ◽  
Vol 16 (03) ◽  
pp. 1842001 ◽  
Author(s):  
Hongfang Song ◽  
Lin Li ◽  
Wenjia Wang ◽  
Qi Li ◽  
Zhicheng Liu
Keyword(s):  
Numerical Simulation ◽  
Aqueous Humor ◽  
Dynamic Pressure ◽  
Field Coupling ◽  
Rabbit Eye ◽  
Aqueous Humor Flow ◽  
Simulation Based ◽  
Dynamic Pressure Measurement ◽  
Ocular Pressure ◽  
Fluid Solid Interaction

In order to investigate the aqueous humor flow based on the coupling effects of fluid–solid–heat under different ocular pressure, four models of rabbit eye were constructed and multi-field coupling vs. fluid–solid interaction was compared in these models. ADINA software was applied to mimic the aqueous humor flow. The contour of temperature demonstrates multiple peaks with larger value near the pupil. The flow pattern is influenced mainly by the variation of ocular pressure. It is necessary to perform multi-field coupling simulation based on dynamic pressure measurement when studying the aqueous humor flow in eyes.

scholarly journals CostNet: A Concise Overpass Spatiotemporal Network for Predictive Learning

2020 ◽  
Vol 9 (4) ◽  
pp. 209
Author(s):  
Fengzhen Sun ◽  
Shaojie Li ◽  
Shaohua Wang ◽  
Qingjun Liu ◽  
Lixin Zhou
Keyword(s):  
State Of The Art ◽  
Vertical Direction ◽  
Bottom Layer ◽  
Spatiotemporal Data ◽  
Short Term ◽  
The Core ◽  
Predictive Learning ◽  
Fast Gradient ◽  
Unit Output ◽  
Cross Connection

Predicting the futures from previous spatiotemporal data remains a challenging topic. There have been many previous works on predictive learning. However, mainstream models suffer from huge memory usage or the gradient vanishing problem. Enlightened by the idea from the resnet, we propose CostNet, a novel recursive neural network (RNN)-based network, which has a horizontal and vertical cross-connection. The core of this network is a concise unit, named Horizon LSTM with a fast gradient transmission channel, which can extract spatial and temporal representations effectively to alleviate the gradient propagation difficulty. In the vertical direction outside of the unit, we add overpass connections from unit output to the bottom layer, which can capture the short-term dynamics to generate precise predictions. Our model achieves better prediction results on moving-mnist and radar datasets than the state-of-the-art models.

Simulation of Flow and Heat Transfer in a Moving Bed Reactor With Cross Flow

2008 ◽  
Author(s):  
Marcelo J. S. de Lemos
Keyword(s):  
Heat Transfer ◽  
Relative Velocity ◽  
Solid Phase ◽  
Cross Flow ◽  
Vertical Direction ◽  
Momentum Equation ◽  
Solid Matrix ◽  
Flow And Heat Transfer ◽  
Temperature Distributions ◽  
Solid Phases

Heat transfer in a porous reactor under cross flow is investigated. The reactor is modeled as a porous bed in which the solid phase is moving horizontally and the flow is forced into the bed in a vertical direction. Equations are time-and-volume averaged and the solid phase is considered to have a constant imposed velocity. Additional drag terms appearing the momentum equation are a function of the relative velocity between the fluid and solid phases. Turbulence equations are also affected by the speed of the solid matrix. Results show temperature distributions for several ratios of the solid to fluid speed.

Experimentally study of dynamic pressure distribution and oil film forces in journal bearing using ElectroMechanical Film sensor array

2019 ◽  
Vol 234 (4) ◽  
pp. 903-913
Author(s):  
Changmin Chen ◽  
Jianping Jing ◽  
Jiqing Cong ◽  
Chao Ji
Keyword(s):  
Pressure Distribution ◽  
Sensor Array ◽  
Journal Bearing ◽  
Dynamic Pressure ◽  
Vertical Direction ◽  
Journal Bearings ◽  
Film Sensor ◽  
Film Pressure ◽  
Oil Film ◽  
Oil Film Pressure

The acquisition of the oil film pressure and forces on the bearing pads through experimentation is crucial to understanding the characteristics of journal bearing. Lots of efforts had been taken in film pressure measurement, and the pressure was obtained at specified position on the bearing pads. However, due to the space and structure constraint, merely very limited number of the point pressure can be obtained with traditional sensors and acquiring the detail pressure field on whole bearing pad surface is still an open challenge. In this paper, a method based on thin-film sensors technique is proposed and employed to measure the pressure distribution and oil film forces of journal bearings. The measurement is conducted on a cylindrical journal bearing with two axial grooves, and ElectroMechanical Film sensor arrays are designed and laid on the surface of the bearing pads. The oil film pressure is acquired at up to 32 measurement points in total along the bearing pads in both circumference and axial directions. The pressure distribution in a wide rotation speed range is obtained successfully by using fitting algorithm. Furthermore, the oil film forces on horizon and vertical direction are obtained through the integration of the measured pressure filed. The test results prove that it is feasible to measure the oil pressure filed of journal bearings using ElectroMechanical Film piezo-film sensor array.

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