scholarly journals Fluid Flow Behavior of Sheared Rough Fractures Subjected to Different Stress State

Crystals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1055
Author(s):  
Min Wang ◽  
Qifeng Guo ◽  
Pengfei Shan ◽  
Yakun Tian ◽  
Bing Dai
Keyword(s):  
Fluid Flow ◽  
Normal Stress ◽  
Contact Area ◽  
Reverse Flow ◽  
Flow Behavior ◽  
Nonlinear Coefficient ◽  
Flow Characteristics ◽  
Shear Displacement ◽  
Navier Stokes Equation ◽  
Linear Coefficient

The hydraulic properties of fractures are greatly affected by the stress. Knowing the fluid flow behavior of fractures is of great importance to underground engineering construction and environmental safety. The main purpose of this paper is to study the fluid flow characteristics of rough fractures under different stress states. First, rough fracture surfaces were generated by using the corrected successive random addition (SRA) algorithm. Then, the sheared fracture models subjected to different stress condition were obtained under the boundary condition of constant normal stiffness (CNS). Finally, the hydraulic characteristics of the three-dimensional rough rock fractures were analyzed by numerically solving the full Navier–Stokes equation. It has been found that (1) the aperture of fractures all obeys the Gaussian distribution. The dilatancy effect is gradually obvious and aperture becomes larger with the increase of shear displacement. (2) When the initial normal stress increases, the contact area of fracture becomes larger and the reverse flow can be observed around the contact area. (3) The relationship between hydraulic gradient and flowrate exhibits nonlinearity which can be described by the Forchheimer’s law. The linear coefficient a and the nonlinear coefficient b gradually decrease with the increase of shear displacement and finally stabilize. The values of a and b are reduced by 1–2 and 1–3 orders of magnitude respectively during the shear. The critical Reynolds number increases with the increase of shear displacement and decrease as the initial normal stress increases.

A Device for Measuring Thin Fluid Flow Depth Over an Inclined Open Rectangular Channel

2009 ◽  
Vol 131 (10) ◽  
Author(s):  
A. K. Majumder
Keyword(s):  
Fluid Flow ◽  
Flow Behavior ◽  
Rectangular Channel ◽  
Flow Characteristics ◽  
Operating Conditions ◽  
Multiple Point ◽  
Flow Depth ◽  
Flow Rates ◽  
Law Of The Wall ◽  
Measured Flow

Accurate knowledge of the fluid flow depth over an inclined rectangular open channel is of obvious value in the modeling of flow characteristics over that channel. Understanding of this type of fluid flow behavior is of immense importance to the mineral processing fraternity as a large number of separators work on this principle. Therefore, a multiple point computer-controlled depth gauge was developed to measure water flow depths at various flow rates ranging from 0.81 l/s to 2.26 l/s over an inclined (17.5 deg) rectangular channel (2400 mm long and 370 mm wide). This paper describes the details about the device and the data acquisition procedure. An attempt has also been made to predict the measured flow depths at various operating conditions by using a modified form of the conventional law of the wall model. An overall relative error of 4.23% between the measured and the predicted flow depths at various flow rates establishes the validity of the model.

Velocity Profile Investigation of FFS Microchannel at Re 100

2014 ◽  
Vol 487 ◽  
pp. 290-293
Author(s):  
Vithyacharan Retnasamy ◽  
Zaliman Sauli ◽  
Steven Taniselass ◽  
Nor Shakirina Nadzri ◽  
Tan Hsio Mei ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Fluid Flow ◽  
Velocity Profile ◽  
Velocity Distribution ◽  
Cross Sections ◽  
Flow Behavior ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Step Height ◽  
Forward Facing Step

Recently, microfluidics system has been widely employed in various areas for instance biomedical,pharmaceuticals and cell biological researchdue to its advantages. The flow behavior in microchannels with different cross-sections has been topic in previous studies. In this paper, numerical simulation of fluid flow in Forward Facing Step (FFS) configuration was performed to investigate velocity profile after the step. Reynolds numbers (Re) 100 with different step heights, 1μm and 3μm were used to observe trend occurs in the flow characteristics. The result illustrated an increase of velocity distribution with the increase of the step height.

Using Computational Fluid Dynamics (CFD) for Evaluation of Fluid Flow Through a Gate Valve

2012 ◽  
Vol 8 (4) ◽  
Author(s):  
Pedro Esteves Duarte Augusto ◽  
Marcelo Cristianini
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Fluid Flow ◽  
Pressure Drop ◽  
Gate Valve ◽  
Flow Behavior ◽  
Flow Characteristics ◽  
Type Equation ◽  
Pharmaceutical Products ◽  
Computational Fluid Dynamics Cfd

Abstract Gate valves are the most common valve in industrial plants. However, there is no work in the literature regarding the use of computational fluid dynamics (CFD) to evaluate the fluid flow characteristics and pressure drop in gate valves. The present work evaluated the fluid flow and pressure drop through a commercial gate valve using CFD. The obtained values for the pressure loss coefficient (k) are in accordance to those described in the literature and a power type equation could be used for modeling it as function of the Reynolds Number. Fluid flow behavior through the gate valve highlighted the flow recirculation and stagnant areas, being critical for food and pharmaceutical products processing. The obtained results reinforce the advantages in using CFD as a tool for the engineering evaluation of fluid processes.

scholarly journals Numerical Investigation of Flow Characteristics of Molten Steel in the Tundish with Channel Induction Heating

Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1937
Author(s):  
Bin Yang ◽  
Hong Lei ◽  
Yingshi Xu ◽  
Kun Liu ◽  
Peng Han
Keyword(s):  
Fluid Flow ◽  
Flow Pattern ◽  
Numerical Investigation ◽  
Induction Heating ◽  
Molten Steel ◽  
Flow Behavior ◽  
Plug Flow ◽  
Flow Characteristics ◽  
Main Flow ◽  
Mixed Flow

In the continuous process, fluid flow is an important physical phenomena in the tundish, as it affects the process of heat transfer, bubble motion and inclusion collision-coalescence and grow up. This paper undertakes a detailed numerical investigation of fluid flow characteristics in the tundish with and without induction heating. The individual unit method and the volume subtraction model are applied to analyze the flow characteristics. A quantitative evaluation method of flow characteristics is proposed to investigate the flow characteristics. In the tundish with and without induction heating, firstly, the main flow behavior of molten steel is mixed flow in the receiving chamber; secondly, the main flow behavior of molten steel is plug flow in the channel; lastly, the main flow pattern is mixed flow, and the minor flow pattern is plug flow in the discharging chamber. The method of the volume subtraction model is an effective way to analyze the flow characteristics in the tundish with channel induction heating.

scholarly journals Numerical Simulation of the Nonlinear Flow Properties in Self-Affine Aperture-Based Fractures

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Xin Zhou ◽  
Jianlong Sheng ◽  
Ruili Lu ◽  
Zuyang Ye ◽  
Wang Luo
Keyword(s):  
Fractal Dimension ◽  
Standard Deviation ◽  
Flow Rate ◽  
Empirical Relationship ◽  
Nonlinear Coefficient ◽  
Nonlinear Flow ◽  
Flow Properties ◽  
Navier Stokes Equation ◽  
Linear Coefficient ◽  
Hydraulic Aperture

In order to study the effect of fracture geometry on the nonlinear flow properties in aperture-based fractures, a fractal model based on the self-affinity is proposed to characterize the three-dimensional geometry of rough-walled fractures. By solving the N–S (Navier–Stokes) equation directly, the relationships between the Forchheimer-flow characteristics, fractal dimension, and standard deviation of the aperture have been obtained. The Forchheimer equation is validated to describe the nonlinear relationship between flow rate and pressure gradient. For lower flow rate, the influence of the fractal dimension almost can be ignored, but the linear coefficient increases and the hydraulic aperture decreases with increasing standard deviation of the aperture, respectively. For larger flow rate, the nonlinear coefficient increases with the growth of the standard deviation of the aperture and fractal dimension. Thus, an empirical relationship between the nonlinear coefficient, fractal dimension, and standard deviation of aperture is proposed. In addition, the critical Reynolds number decreases with the increase of the standard deviation of the aperture and the fractal dimension, and the numerical results are generally consistent with the experimental data.

A PREDICTIVE MODEL OF PERMEABILITY FOR FRACTAL-BASED ROUGH ROCK FRACTURES DURING SHEAR

Fractals ◽  
2017 ◽  
Vol 25 (05) ◽  
pp. 1750051 ◽  
Author(s):  
NA HUANG ◽  
YUJING JIANG ◽  
RICHENG LIU ◽  
BO LI ◽  
ZHENYU ZHANG
Keyword(s):  
Predictive Model ◽  
Normal Stress ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Shear Displacement ◽  
Roughness Coefficient ◽  
Fracture Aperture ◽  
Rock Fractures ◽  
Simple Method ◽  
The Mean

This study investigates the roles of fracture roughness, normal stress and shear displacement on the fluid flow characteristics through three-dimensional (3D) self-affine fractal rock fractures, whose surfaces are generated using the modified successive random additions (SRA) algorithm. A series of numerical shear-flow tests under different normal stresses were conducted on rough rock fractures to calculate the evolutions of fracture aperture and permeability. The results show that the rough surfaces of fractal-based fractures can be described using the scaling parameter Hurst exponent [Formula: see text], in which [Formula: see text], where [Formula: see text] is the fractal dimension of 3D single fractures. The joint roughness coefficient (JRC) distribution of fracture profiles follows a Gauss function with a negative linear relationship between [Formula: see text] and average JRC. The frequency curves of aperture distributions change from sharp to flat with increasing shear displacement, indicating a more anisotropic and heterogeneous flow pattern. Both the mean aperture and permeability of fracture increase with the increment of surface roughness and decrement of normal stress. At the beginning of shear, the permeability increases remarkably and then gradually becomes steady. A predictive model of permeability using the mean mechanical aperture is proposed and the validity is verified by comparisons with the experimental results reported in literature. The proposed model provides a simple method to approximate permeability of fractal-based rough rock fractures during shear using fracture aperture distribution that can be easily obtained from digitized fracture surface information.

Fluid Flow Characteristics for Partially-Confined Compact Plain-Plate-Fin Heat Sinks

2005 ◽  
Author(s):  
M. P. Wang ◽  
T. Y. Wu ◽  
J. T. Horng ◽  
C. Y. Lee ◽  
Y. H. Hung
Keyword(s):  
Experimental Data ◽  
Fluid Flow ◽  
Pressure Drop ◽  
Heat Sink ◽  
Flow Behavior ◽  
Flow Characteristics ◽  
Heat Sinks ◽  
Experimental Investigations ◽  
Channel Height ◽  
Fluid Flow Characteristics

A series of experimental investigations with a stringent measurement method on the study of the fluid flow behavior for confined compact heat sinks in forced convection have been successfully conducted. In the present study, a theoretical model to effectively predict the velocity and pressure drop for partially-confined heat sinks has been successfully developed. The air velocities flowing into heat sink Us through side bypass U1 and top bypass U2 for various 0.47<H/Hc<1 ratios are evaluated, where H/Hc is the ratio of the heat sink height to channel height. The maximum and average deviations of the velocities predicted by the present model from the experimental data are less than 20.31% and 13.13%, respectively, for confined compact heat sinks. Besides, the results show a good agreement between the predicted results and the experimental data of the pressure drop for the cases of H/Hc = 1. Nevertheless, the relative deviation of the predictions from the experimental data becomes more significant with decreasing H/Hc ratio, i.e., increasing the top bypass of confined compact heat sink. A new modified correlation of pressure drop including the H/Hc effect is presented. The maximum and average deviations of the results predicted by the new correlation from the experimental data are 14.48% and 7.72%, respectively.

scholarly journals Fluid Flow Characterization of Single-Strand Tundish with Flow Modifiers through Physical Water Model (PWM) and CFD Simulation

2021 ◽  
Vol 12 (1) ◽  
pp. 211-221
Keyword(s):  
Fluid Flow ◽  
Residence Time ◽  
Cfd Simulation ◽  
Flow Behavior ◽  
Flow Characteristics ◽  
Steel Production ◽  
Single Strand ◽  
Experimental Simulation ◽  
Water Model ◽  
Inclusion Removal

The flow behavior in the continuous casting tundish dominates the quality and cleanliness of steel production. In this research, the single strand tundish's fluid flow behavior with different flow modifiers is investigated through numerical and experimental simulation. The numerical; simulation is performed in ANSYS FLUENT 19.2 (commercial package) and experimental through physical water model technique. The flow behaviors of bare tundish and tundish with three different flow modifiers are investigated. The three different flow modifiers deployed are the dam, baffle, and turbulence inhibiter (TI). Fluid flow performance is examined through residence time distribution (RTD) curves, which are derived from the measurement of the tracer concentration at the outlet. Good agreement between the CFD simulation and physical water model experiments is discovered. The results show there is an improvement in residence time and fluid flow (also improved inclusion removal) after the deployment of flow modifiers. There is a 20% improvement in peak and minimum residence time of RTD curves due to flow modifiers application. It is also discovered that the tundish configuration in this research, the tundish with turbulence inhibiter, provides optimal flow characteristics and eventually intended to promote a better level of inclusion removal.

scholarly journals Natural Rock Fractures: From Aperture to Fluid Flow

2021 ◽  
Author(s):  
Alejandro Cardona ◽  
Thomas Finkbeiner ◽  
J. Carlos Santamarina
Keyword(s):  
Fluid Flow ◽  
Normal Stress ◽  
Size Distribution ◽  
Power Law ◽  
Preferential Flow ◽  
Shear Displacement ◽  
Shear Direction ◽  
Aperture Size ◽  
Standard Deviation Increase ◽  
Normal Loading

AbstractFractures provide preferential flow paths and establish the internal “plumbing” of the rock mass. Fracture surface roughness and the matedness between surfaces combine to delineate the fracture geometric aperture. New and published measurements show the inherent relation between roughness wavelength and amplitude. In fact, data cluster along a power trend consistent with fractal topography. Synthetic fractal surfaces created using this power law, kinematic constraints and contact mechanics are used to explore the evolution of aperture size distribution during normal loading and shear displacement. Results show that increments in normal stress shift the Gaussian aperture size distribution toward smaller apertures. On the other hand, shear displacements do not affect the aperture size distribution of unmated fractures; however, the aperture mean and standard deviation increase with shear displacement in initially mated fractures. We demonstrate that the cubic law is locally valid when fracture roughness follows the observed power law and allows for efficient numerical analyses of transmissivity. Simulations show that flow trajectories redistribute and flow channeling becomes more pronounced with increasing normal stress. Shear displacement induces early aperture anisotropy in initially mated fractures as contact points detach transversely to the shear direction; however, anisotropy decreases as fractures become unmated after large shear displacements. Radial transmissivity measurements obtained using a torsional ring shear device and data gathered from the literature support the development of robust phenomenological models that satisfy asymptotic trends. A power function accurately captures the evolution of transmissivity with normal stress, while a logistic function represents changes with shear displacement. A complementary hydro-chemo-mechanical study shows that positive feedback during reactive fluid flow heightens channeling.

scholarly journals Experimental Investigation of Grout Nonlinear Flow Behavior through Rough Fractures

Processes ◽  
2019 ◽  
Vol 7 (10) ◽  
pp. 736 ◽  
Author(s):  
Yuhao Jin ◽  
Lijun Han ◽  
Changyu Xu ◽  
Qingbin Meng ◽  
Zhenjun Liu ◽  
...  
Keyword(s):  
Flow Behavior ◽  
Nonlinear Coefficient ◽  
Nonlinear Flow ◽  
Flow State ◽  
Inertia Effect ◽  
Linear Coefficient ◽  
Three Stages ◽  
Stress Dependent ◽  
Nonlinear Flow Behavior ◽  
Forchheimer’S Law

This research experimentally analyzed the impacts of various water cement (W/C) ratios of ultrafine cement grout material and normal loads FN applied to fractures on grout nonlinear flow behavior through a rough plexiglass fractured sample. An effective self-made apparatus was designed and manufactured to conduct the stress-dependent grout flow tests on the plexiglass sample containing rough fractures. At each W/C ratio, the grout pressure P increased from 0 to 0.9 MPa, and the normal loads FN ranged from 666.3 to 1467.8 N. The results of the experiments indicate that (1) the Forchheimer’s law can be used to express the results of grout nonlinear flow through rough fractures. Moreover, both nonlinear coefficient a and linear coefficient b in Forchheimer’s law decreased with the increase of the W/C ratio, but increased with the increase of the FN value. (2) For normalized transmissivity, with the increase of Re, the decline of the T/T0–Re curves means that the grout flow behavior through the fracture mainly went through three stages: the viscosity effect, then the weak inertia effect, and finally the strong inertia effect. The three stages showed that with the increase of Re, the grout flow state changed from linear to nonlinear. Moreover, with the increase of the W/C ratio, the Forchheimer coefficient β decreased. (3) At a given FN, the critical grout hydraulic gradient Jc decreased, but the critical Reynolds number Rec increased as the W/C ratio increased; at a given W/C ratio, Jc increased, but Rec decreased as FN increased.

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