scholarly journals Numerical Study on Diffusion of Chloride and Induced Rebar Corrosion by Two-Dimensional Multiscale Approach

2018 ◽  
Vol 2018 ◽  
pp. 1-20
Author(s):  
Xi Tu ◽  
Jin Di ◽  
Cunjun Pang ◽  
Xiaoqing Xu
Keyword(s):  
Numerical Simulation ◽  
Volume Fraction ◽  
Numerical Study ◽  
Macroscopic Model ◽  
Multiscale Approach ◽  
Two Dimensional ◽  
Analysis Model ◽  
Mesoscopic Model ◽  
Random Aggregate ◽  
Rebar Corrosion

Modeling approach for mesoscopic model of concrete depicting mass transportation and physicochemical reaction is important since there is growing demand for accuracy and computational efficiency of numerical simulation. Mesoscopic numerical simulation considering binder, aggregate, and interfacial transition zone (ITZ) generally produces huge number of DOFs, which is inapplicable for full structure. In this paper, a two-dimensional multiscale approach describing three-phase structure of concrete was discussed numerically. An effective approach generating random aggregate in polygon based on checking centroid distance and intersection of line segment was introduced. Moreover, ITZ elements were built by parallel expanding the edge of aggregates on inner side. By combining mesoscopic model including full-graded aggregate and macroscopic model, cases related to diffusivity and width of ITZ, volume fraction, and grade of aggregate were studied regarding the consideration of multiscale compensation. Result clearly showed that larger analysis model in multiscale model expanded the diffusion space of chloride ion and decreased chloride content in front of rebar. Finally, this paper addressed some noteworthy conclusions about the chloride distribution and rebar corrosion regarding the configuration of rebar diameter, concrete cover, and exposure period.

Experimental and numerical study of vortex couples in two-dimensional flows

1986 ◽  
Vol 173 ◽  
pp. 225-251 ◽  
Author(s):  
Y. Couder ◽  
C. Basdevant
Keyword(s):  
Numerical Simulation ◽  
Turbulent Flows ◽  
Opposite Sign ◽  
Numerical Study ◽  
Liquid Films ◽  
Thin Liquid Films ◽  
Two Dimensional ◽  
Spontaneous Formation ◽  
Laboratory Results ◽  
Two Dimensional Flows

Two-dimensional turbulence is investigated experimentally in thin liquid films. This study shows the spontaneous formation of couples of opposite-sign vortices in von Kármán wakes. The structure of these couples, their behaviour and their role in turbulent flows is then studied using both a numerical simulation and laboratory results.

scholarly journals Numerical Study of MHD Natural Convection in Trapezoidal Enclosure Filled With (50%MgO-50%Ag/Water) Hybrid Nanofluid: Heated Sinusoidal from Below

2021 ◽  
Vol 39 (4) ◽  
pp. 1271-1279
Author(s):  
Mohammed Azeez Alomari ◽  
Khaled Al-Farhany ◽  
Alaa Liaq Hashem ◽  
Mohamed F. Al-Dawody ◽  
Fares Redouane ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Hartmann Number ◽  
Volume Fraction ◽  
Numerical Study ◽  
Working Fluid ◽  
Hybrid Nanofluid ◽  
Nusselt Numbers ◽  
Stream Functions ◽  
Trapezoidal Enclosure ◽  
Good Agreement

Numerical simulation of MHD free convection in a two-dimensional trapezoidal cavity of a hybrid nanofluid has been carried out in this research. The cavity is heated sinusoidal from the bottom wall, and the inclined walls are cooled while the top wall is isolated. The hybrid nanofluid (MgO-Ag/water) has been used as a working fluid. The numerical simulation has been validated with past papers and met a good agreement. The considered parameters are a range of Rayleigh number (Ra= 103 to 106), Hartmann number (Ha= 0 to 60) and volume fraction (f= 0 to 0.02). The results are presented as isotherms, stream functions, local and average Nusselt numbers, from which it is observed that the strength of the stream functions and isotherms increases with the increase of the Ra and ϕ while the increase in Hartmann number reduce the circulation of the flow and increases the isotherms strength. Also, the Nusselt number is increases with Ra and ϕ while it decreases with Ha.

Unsteady Numerical and Experimental Study of Cavitation in Axial Pump

2014 ◽  
Vol 4 (1) ◽  
pp. 55-68
Author(s):  
Mohamed Adel ◽  
Nabil H. Mostafa
Keyword(s):  
Numerical Simulation ◽  
Void Growth ◽  
High Speed ◽  
Volume Fraction ◽  
Numerical Study ◽  
Three Dimensional ◽  
Axial Flow ◽  
Two Phase ◽  
Impeller Blade ◽  
Axial Pump

This paper presents an experimental and three-dimensional numerical study of unsteady, turbulent, void growth and cavitation simulation inside the passage of the axial flow pump. In this study a 3D Navier-Stokes code was used (CFDRC, 2008) to model the two-phase flow field around a four blades axial pump. The governing equations are discretized on a structured grid using an upwind difference scheme. The numerical simulation used the standard K-e turbulence model to account for the turbulence effect. The numerical simulation of void growth and cavitation in an axial pump was studied under unsteady calculating. Pressure distribution and vapor volume fraction were completed versus time at different condition. The computational code has been validated by comparing the predicated numerical results with the experiment. The predicted of cavitation growth and distribution on the impeller blade also agreed with that visualized of high speed camera.

Numerical Study of Cavitation on Hydrofoils

2010 ◽  
Vol 44-47 ◽  
pp. 2001-2005
Author(s):  
Jing Hu ◽  
Xian Zhou Wang ◽  
Ming Yue Liu ◽  
Zhi Guo Zhang ◽  
Qi Zhou
Keyword(s):  
Numerical Simulation ◽  
Stokes Equation ◽  
Turbulence Model ◽  
Volume Fraction ◽  
Numerical Study ◽  
Navier Stokes ◽  
Special Focus ◽  
Navier Stokes Equation ◽  
The Relationship ◽  
Incompressible Navier Stokes Equation

Based on CFD technology, flow around a 2-dimentional hydrofoil of highly skewed propeller and NACA series hydrofoils are simulated using 2D incompressible Navier-Stokes equation with Realizable k- turbulence model. In the numerical simulation, the vapor volume fraction is calculated for different cavitation numbers and angles of attack by adding the mixture model. The hydrofoil’s performance and the relationship with hydrofoil parameter are qualitatively analyzed. Special focus is given to the influence of the cavitation numbers and angle of attack on cavitation characteristics.

A Numerical Study of a Two-Dimensional Stepped Planing Surface

2012 ◽  
Vol 28 (02) ◽  
pp. 60-72 ◽  
Author(s):  
William R. Garland ◽  
Kevin J. Maki
Keyword(s):  
Numerical Simulation ◽  
Free Surface ◽  
Numerical Study ◽  
Pressure Profile ◽  
The Body ◽  
Nonlinear Flow ◽  
Two Dimensional ◽  
Free Surface Elevation ◽  
Frictional Drag ◽  
Drag Ratio

In this paper the performance of a stepped planing hull is analyzed through numerical simulation of the fully nonlinear flow under a two-dimensional body. The height and location of the step are systematically varied to investigate the resulting free-surface elevation, pressure profile on the body, and fraction of the total lift that is developed on the downstream portion of the body. The results indicate that indeed a larger step height will generate a larger lift-to-frictional-drag ratio. This suggests that the largest step possible should be chosen, with the upper bound for this dimension being the height in which the flow no longer reattaches to the after-body. The results show that the lift-to-frictional-drag ratio varies very little with respect to the step location over the range studied in this work.

Numerical Study on the Performance of a Micropump with a Wiggling Blade

2005 ◽  
Vol 219 (10) ◽  
pp. 1069-1077
Author(s):  
T Uchiyama ◽  
K Kikuyama
Keyword(s):  
Numerical Simulation ◽  
Finite Element Method ◽  
Reynolds Number ◽  
Numerical Study ◽  
Two Dimensional ◽  
Progressive Wave ◽  
Trailing Edge ◽  
Pump Performance ◽  
Dimensional Finite Element ◽  
Straight Conduit

This study is concerned with the numerical simulation for the performance of a micropump having a wiggling blade. The blade is mounted on a straight conduit, and the wiggling motion is expressed by a progressive wave. The flow in the pump is simulated by the two-dimensional finite element method. The Reynolds number Re, based on the phase velocity of the progressive wave and the blade length, ranges from 10 to 150. The similarity for pump performance appears at Re ≥ 100. However, the pump performance deteriorates with decreasing Re at Re < 100. The time variation of the pump flowrate is found to be very small, demonstrating that the pump can deliver almost steady flow. The simulation also reveals the mechanism of the delivery as follows: The flow heading for the pump outlet occurs near the concave surface of the blade, and it is transported by the progressive wave to the blade trailing edge, and eventually, it is shed from the trailing edge.

Numerical study on flow characteristics of rotor pumps including cavitation

2014 ◽  
Vol 229 (14) ◽  
pp. 2626-2638 ◽  
Author(s):  
Yingyuan Liu ◽  
Leqin Wang ◽  
Zuchao Zhu
Keyword(s):  
Numerical Model ◽  
Mass Flow ◽  
Volume Fraction ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Two Dimensional ◽  
Flow Rates ◽  
Factors Affecting ◽  
Remarkable Effect ◽  
Mass Flow Rates

This work is purposed to study the flow characteristics of rotor pumps including cavitation. First, a simplified two-dimensional numerical model is developed and computing strategies of the numerical analysis for cavitation are set up, including the selection of cavitation model and its parameters. Second, the reliability and accuracy of the two-dimensional numerical model are verified by experimental results. Then, several factors affecting the cavitation are discussed, including the rotational speeds, pressure differences, clearance sizes, and inlet pressures. For different rotational speeds and pressure differences, the mass flow rates with cavitation are a little larger than that without cavitation, but the amplitudes of the mass flow rates with cavitation are much larger than that without cavitation. Meanwhile, the volume fraction of the water vapor increases with the increasing speeds and the decreasing pressure differences. However, compared with the influence of rotational speeds, the influence of the pressure differences on the vapor contents is relatively smaller. Regarding the clearance size, the smaller the clearance size is, the stronger the cavitation will be. Furthermore, the clearance size between two rotors has a larger effect on the cavitation than that between rotor and pump case. For inlet pressure, it has a little effect on the mass flow rates when cavitation is not considered, but it presents a remarkable effect for the model with cavitation. In addition, the peaks of the volume fractions of vapor and the mass flow rates generally offset backward with the decreasing inlet pressures.

Instrumentation For Quantitative Microscopy

1977 ◽  
Vol 35 ◽  
pp. 206-209
Author(s):  
B. Ralph ◽  
A.R. Jones
Keyword(s):  
Volume Fraction ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Automatic Data ◽  
Phase Volume Fraction ◽  
Statistical Confidence ◽  
Resultant Data ◽  
Automatic Data Collection ◽  
Third Dimension ◽  
Evolution Of Microstructure

In all fields of microscopy there is an increasing interest in the quantification of microstructure. This interest may stem from a desire to establish quality control parameters or may have a more fundamental requirement involving the derivation of parameters which partially or completely define the three dimensional nature of the microstructure. This latter categorey of study may arise from an interest in the evolution of microstructure or from a desire to generate detailed property/microstructure relationships. In the more fundamental studies some convolution of two-dimensional data into the third dimension (stereological analysis) will be necessary.In some cases the two-dimensional data may be acquired relatively easily without recourse to automatic data collection and further, it may prove possible to perform the data reduction and analysis relatively easily. In such cases the only recourse to machines may well be in establishing the statistical confidence of the resultant data. Such relatively straightforward studies tend to result from acquiring data on the whole assemblage of features making up the microstructure. In this field data mode, when parameters such as phase volume fraction, mean size etc. are sought, the main case for resorting to automation is in order to perform repetitive analyses since each analysis is relatively easily performed.

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