scholarly journals Analysis of Mathematics and Sustainability in an Impulsive Eutrophication Controlling System

2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
Hengguo Yu ◽  
Min Zhao ◽  
Qi Wang
Keyword(s):  
Numerical Simulation ◽  
Theoretical Basis ◽  
Algal Bloom ◽  
Critical Parameters ◽  
Critical Factors ◽  
Experiment Data ◽  
Threshold Functions ◽  
Controlling System ◽  
Best Value ◽  
Mathematical System

Eutrophication removal problems have captured the attention of biologists, mathematicians, and environmental scientists. Within this framework, an impulsive eutrophication controlling system is studied analytically and numerically. A key advantage of the eutrophication system is that it can be quite accurate to describe the interaction effect of some critical factors (fishermen catch and releasing small fry, etc.), which enables a systematic and logical procedure for fitting eutrophication mathematical system to real monitoring data and experiment data. Mathematical theoretical works have been pursuing the investigation of two threshold functions of some critical parameters under the condition of all species persistence, which can in turn provide a theoretical basis for the numerical simulation. Using numerical simulation works, we mainly focus on how to choose the best value of some critical parameters to ensure the sustainability of the eutrophication system so that the eutrophication removal process can be well developed with maximizing economic benefit. These results may be further extended to provide a basis for simulating the algal bloom in the laboratory and understanding the application of some impulsive controlling models about eutrophication removal problems.

scholarly journals Development of Depth-Limited Wave Boundary Layers over a Smooth Bottom

2020 ◽  
Vol 9 (1) ◽  
pp. 27
Author(s):  
Hitoshi Tanaka ◽  
Nguyen Xuan Tinh ◽  
Xiping Yu ◽  
Guangwei Liu
Keyword(s):  
Numerical Simulation ◽  
Boundary Layer ◽  
Boundary Layers ◽  
Wave Motion ◽  
Numerical Study ◽  
Experiment Data ◽  
Tidal Motion ◽  
Long Period ◽  
Simulation Results ◽  
Wave Boundary

A theoretical and numerical study is carried out to investigate the transformation of the wave boundary layer from non-depth-limited (wave-like boundary layer) to depth-limited one (current-like boundary layer) over a smooth bottom. A long period of wave motion is not sufficient to induce depth-limited properties, although it has simply been assumed in various situations under long waves, such as tsunami and tidal currents. Four criteria are obtained theoretically for recognizing the inception of the depth-limited condition under waves. To validate the theoretical criteria, numerical simulation results using a turbulence model as well as laboratory experiment data are employed. In addition, typical field situations induced by tidal motion and tsunami are discussed to show the usefulness of the proposed criteria.

Numerical Simulation of Cavitating Flow in a Francis Turbine

2008 ◽  
Author(s):  
Lingjiu Zhou ◽  
Zhengwei Wang ◽  
Yongyao Luo ◽  
Guangjie Peng
Keyword(s):  
Numerical Simulation ◽  
Transport Equation ◽  
Flow Rate ◽  
Suction Side ◽  
Cavitating Flow ◽  
Francis Turbine ◽  
Efficiency Change ◽  
Experiment Data ◽  
Calculation Results ◽  
Vapor Fraction

The 3-D unsteady Reynolds averaged Navier-tokes equations based on the pseudo-homogeneous flow theory and a vapor fraction transport-equation that accounts for non-condensable gas are solved to simulate cavitating flow in a Francis turbine. The calculation results agreed with experiment data reasonably. With the decrease of the Thoma number, the cavity first appears near the centre of the hub. At this stage the flow rate and the efficiency change little. Then the cavity near the centre of the hub grows thick and the cavities also appear on the blade suction side near outlet. With further reduce of the Thoma number the cavitation extends to the whole flow path, which causes flow rate and efficiency decrease rapidly.

Research on Propagation Numerical Simulation of Blast Shock Waves in Subway Station

2013 ◽  
Vol 380-384 ◽  
pp. 1725-1728
Author(s):  
Yang Hu ◽  
Huai Yu Kang
Keyword(s):  
Numerical Simulation ◽  
Shock Wave ◽  
Experimental Study ◽  
Shock Waves ◽  
Theoretical Basis ◽  
Damage Effect ◽  
Subway Station ◽  
Element Calculation ◽  
Dynamic Finite Element ◽  
Walking Pattern

In this paper, we Research on Propagation Numerical Simulation and damage effect of Blast Shock Waves in Subway Station by using LS-DYNA dynamic finite element calculation program , the results reproduce the formation process of the explosive flow field, and analysis the shock wave waveform, attenuation and walking pattern, provides the theoretical basis for further experimental study.

Simulation and Analysis of Swing Motion of Lifting Load System on Rescue Vehicle

2012 ◽  
Vol 538-541 ◽  
pp. 725-729
Author(s):  
Han Ming Liu ◽  
Heng Zhao ◽  
Ning Li
Keyword(s):  
Numerical Simulation ◽  
Theoretical Basis ◽  
Safety Assessment ◽  
Kinematic Model ◽  
Excitation Frequency ◽  
Lagrange’S Equation ◽  
Set Up

In lifting, remoted operated dive vehicle（ROV） may swing with the effect of wave. Based on the general form of Lagrange’s equation, a 3-DOF nonlinear swing motion kinematic model was set up. The kinematic response was studied using methods of numerical simulation. The results demonstrated that the kinematic response depends on the length of cable, lifting speed and excitation frequency. Conclusions drawn from this work can be used for safety assessment and theoretical basis for lifting ROV.

scholarly journals Complex Dynamical Behavior of a Predator-Prey System with Group Defense

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Jianglin Zhao ◽  
Min Zhao ◽  
Hengguo Yu
Keyword(s):  
Numerical Simulation ◽  
Theoretical Basis ◽  
Dynamical Behavior ◽  
Turing Instability ◽  
Equilibrium Density ◽  
Prey Refuge ◽  
Predator Prey ◽  
Prey System ◽  
Group Defense ◽  
Complex Dynamical Behavior

A diffusive predator-prey system with prey refuge is studied analytically and numerically. The Turing bifurcation is analyzed in detail, which in turn provides a theoretical basis for the numerical simulation. The influence of prey refuge and group defense on the equilibrium density and patterns of species under the condition of Turing instability is explored by numerical simulations, and this shows that the prey refuge and group defense have an important effect on the equilibrium density and patterns of species. Moreover, it can be obtained that the distributions of species are more sensitive to group defense than prey refuge. These results are expected to be of significance in exploration for the spatiotemporal dynamics of ecosystems.

NUMERICAL SIMULATION OF DAM BREAK BY ADAPTIVE STENCIL DIFFUSE INTERFACE METHOD

2009 ◽  
Vol 23 (03) ◽  
pp. 293-296 ◽  
Author(s):  
L. DING ◽  
C. SHU ◽  
N. ZHAO
Keyword(s):  
Numerical Simulation ◽  
Adaptive Algorithm ◽  
Leading Edge ◽  
Dam Break ◽  
Experimental Results ◽  
Diffuse Interface ◽  
Fine Scale ◽  
Experiment Data ◽  
Interface Behavior

This paper presents the application of an adaptive stencil diffuse interface method to the simulation of dam break problem. The adaptive stencil diffuse interface method is the combination of the diffuse interface method and a stencil adaptive algorithm, where the diffuse interface method is used as the solver, and the adaptive stencil refinement scheme is applied to improve the resolution around the interface so that the fine-scale interface behavior can be captured. In this paper, we use this method to simulate the dam break problem, study the dam height and leading edge position, and compare our results with the experiment data available in the literature. It is shown that the results using the adaptive stencil diffuse interface method agree very well with the experimental results.

FEM Analysis of Contact for Converter Spherical Hinge

2013 ◽  
Vol 365-366 ◽  
pp. 331-334
Author(s):  
Xue Ping Ren ◽  
Jian Da Gao
Keyword(s):  
Numerical Simulation ◽  
Thermal Stress ◽  
Optimum Design ◽  
Theoretical Basis ◽  
Fem Analysis ◽  
Structure Design ◽  
Coupling Field ◽  
Main Components ◽  
Spherical Hinge

The role of converter spherical hinge is one of the main components, combined with practical work and With help of FEM, Thermal Stress coupling field of spherical washer can been obtained through numerical simulation. The result supplies substantial theoretical basis for further structure design and optimum design of mechanism.

scholarly journals Discussion on the Theoretical Basis for Cross-Over Method Applied to Downhole Wave Velocity Test

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Qing Dong ◽  
Zheng-hua Zhou ◽  
Su Jie ◽  
Bing Hao ◽  
Yuan-dong Li
Keyword(s):  
Numerical Simulation ◽  
Numerical Simulations ◽  
Wave Velocity ◽  
Theoretical Basis ◽  
Influence Factors ◽  
P Wave ◽  
Engineering Practice ◽  
S Wave ◽  
Simulation Results ◽  
The Cross

At engineering practice, the theoretical basis for the cross-over method, used to obtain shear wave arrival time in the downhole method of the wave velocity test by surface forward and backward strike, is that the polarity of P-wave keeps the same, while the polarity of S-wave transforms when the direction of strike inverted. However, the characteristics of signals recorded in tests are often found to conflict with this theoretical basis for the cross-over method, namely, the polarity of the P-wave also transforms under the action of surface forward and backward strike. Therefore, 3D finite element numerical simulations were conducted to study the validity of the theoretical basis for the cross-over method. The results show that both shear and compression waves are observed to be in 180° phase difference between horizontal signal traces, consistent with the direction of excitation generated by reversed impulse. Furthermore, numerical simulation results prove to be reliable by the analytic solution; it shows that the theoretical basis for the cross-over method applied to the downhole wave velocity test is improper. In meanwhile, numerical simulations reveal the factors (inclining excitation, geophone deflection, inclination, and background noise) that may cause the polarity of the P-wave not to reverse under surface forward and backward strike. Then, as to reduce the influence factors, we propose a method for the downhole wave velocity test under surface strike, the time difference of arrival is based between source peak and response peak, and numerical simulation results show that the S-wave velocity by this method is close to the theoretical S-wave velocity of soil.

Numerical Simulation of the H-Beam during Cooling Process

2013 ◽  
Vol 310 ◽  
pp. 145-149 ◽  
Author(s):  
Jian Liu ◽  
Fu Zeng Hou ◽  
Xiao Guang Yu
Keyword(s):  
Mechanical Properties ◽  
Numerical Simulation ◽  
Heat Treatment ◽  
Theoretical Basis ◽  
Treatment Process ◽  
Residual Austenite ◽  
Heat Treatment Process ◽  
Cooling Process ◽  
Controlled Cooling ◽  
H Beam

In order to improve the comprehensive mechanical properties of the steel, the heat treatment software COSMAP is used to simulate the rolling and controlled cooling of H-beam. The numerical simulation shows that the mechanical properties of controlled cooling can be obviously improved, when the cooling rate is controlled at 10°C/s around. Strength and hardness can be improved under the condition of ductility and toughness ensured. Meanwhile the amount of residual austenite can be reduced significantly. It provides a theoretical basis for further optimization of the heat treatment process.

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