Constitutive Model of a Transversely Isotropic Bingham Fluid

2002 ◽  
Vol 69 (5) ◽  
pp. 641-648 ◽  
Author(s):  
D. N. Robinson ◽  
K. J. Kim ◽  
J. L. White
Keyword(s):  
Viscous Flow ◽  
Potential Function ◽  
Flow Characteristics ◽  
Transversely Isotropic ◽  
Bingham Fluid ◽  
Threshold Function ◽  
Isotropic Model ◽  
Flow Potential ◽  
Characterization Procedure

A constitutive theory is presented for a transversely isotropic, viscoplastic (Bingham) fluid. The theory accounts for threshold (yield) and viscous flow characteristics through inclusion of a potential function serving the dual role of a threshold function and a viscous flow potential. The arguments and form of the potential function derive from the theory of tensorial invariants. The model reduces to a transversely isotropic model of perfect plasticity in the limit of vanishing viscosity. In the limit of isotropy, it reduces to the Hohenemser-Prager generalization of Bingham’s model. A characterization procedure is prescribed based on correlation with experiments conducted under simple states of stress. Application is made to polymer melts filled with talc particles.

A Viscoplastic Constitutive Theory for Monolithic Ceramics—I

1998 ◽  
Vol 120 (1) ◽  
pp. 155-161 ◽  
Author(s):  
L. A. Janosik ◽  
S. F. Duffy
Keyword(s):  
Potential Function ◽  
Constitutive Equations ◽  
Hydrostatic Stress ◽  
Functional Dependence ◽  
Threshold Function ◽  
Cauchy Stress ◽  
Creep Stress ◽  
Flow Potential ◽  
Tension And Compression ◽  
Monolithic Ceramics

This paper, which is the first of two in a series, provides an overview of a viscoplastic constitutive model that accounts for time-dependent material deformation (e.g., creep, stress relaxation, etc.) in monolithic ceramics. Using continuum principles of engineering mechanics, the complete theory is derived from a scalar dissipative potential function first proposed by Robinson (1978), and later utilized by Duffy (1988). Derivations based on a flow potential function provide an assurance that the inelastic boundary value problem is well posed, and solutions obtained are unique. The specific formulation used here for the threshold function (a component of the flow potential function) was originally proposed by Willam and Warnke (1975) in order to formulate constitutive equations for time-independent classical plasticity behavior observed in cement and unreinforced concrete. Here constitutive equations formulated for the flow law (strain rate) and evolutionary law employ stress invariants to define the functional dependence on the Cauchy stress and a tensorial state variable. This particular formulation of the viscoplastic model exhibits a sensitivity to hydrostatic stress, and allows different behavior in tension and compression.

scholarly journals A Viscoplastic Constitutive Theory for Monolithic Ceramics: I

1996 ◽  
Author(s):  
Lesley A. Janosik ◽  
Stephen F. Duffy
Keyword(s):  
Potential Function ◽  
Constitutive Equations ◽  
Hydrostatic Stress ◽  
Functional Dependence ◽  
Threshold Function ◽  
Cauchy Stress ◽  
Creep Stress ◽  
Flow Potential ◽  
Tension And Compression ◽  
Monolithic Ceramics

This paper, which is the first of two in a series, provides an overview of a viscoplastic constitutive model that accounts for time-dependent material deformation (e.g., creep, stress relaxation, etc.) in monolithic ceramics. Using continuum principles of engineering mechanics the complete theory is derived from a scalar dissipative potential function first proposed by Robinson (1978), and later utilized by Duffy (1988). Derivations based on a flow potential function provide an assurance that the inelastic boundary value problem is well posed, and solutions obtained are unique. The specific formulation used here for the threshold function (a component of the flow potential function) was originally proposed by Willam and Warnke (1975) in order to formulate constitutive equations for time-independent classical plasticity behavior observed in cement and unreinforced concrete. Here constitutive equations formulated for the flow law (strain rate) and evolutionary law employ stress invariants to define the functional dependence on the Cauchy stress and a tensorial state variable. This particular formulation of the viscoplastic model exhibits a sensitivity to hydrostatic stress, and allows different behavior in tension and compression.

scholarly journals Water-Worked Gravel Bed: State-of-the-Art Review

Water ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 694 ◽  
Author(s):  
Ellora Padhi ◽  
Subhasish Dey ◽  
Venkappayya R. Desai ◽  
Nadia Penna ◽  
Roberto Gaudio
Keyword(s):  
State Of The Art ◽  
Flow Characteristics ◽  
Streamwise Velocity ◽  
Secondary Currents ◽  
Gravel Bed ◽  
Natural Stream ◽  
Art Research ◽  
The Comparative Study ◽  
Water Work

In a natural gravel-bed stream, the bed that has an organized roughness structure created by the streamflow is called the water-worked gravel bed (WGB). Such a bed is entirely different from that created in a laboratory by depositing and spreading gravels in the experimental flume, called the screeded gravel bed (SGB). In this paper, a review on the state-of-the-art research on WGBs is presented, highlighting the role of water-work in determining the bed topographical structures and the turbulence characteristics in the flow. In doing so, various methods used to analyze the bed topographical structures are described. Besides, the effects of the water-work on the turbulent flow characteristics, such as streamwise velocity, Reynolds and form-induced stresses, conditional turbulent events and secondary currents in WGBs are discussed. Further, the results form WGBs and SGBs are compared critically. The comparative study infers that a WGB exhibits a higher roughness than an SGB. Consequently, the former has a higher magnitude of turbulence parameters than the latter. Finally, as a future scope of research, laboratory experiments should be conducted in WGBs rather than in SGBs to have an appropriate representation of the flow field close to a natural stream.

Internal Variable Theory Formulated by One Extended Potential Function

2020 ◽  
Vol 45 (3) ◽  
pp. 311-318
Author(s):  
Qiang Yang ◽  
Zhuofu Tao ◽  
Yaoru Liu
Keyword(s):  
Potential Function ◽  
Internal Variable ◽  
The State ◽  
Internal Variables ◽  
State Variables ◽  
Kinetic Rate ◽  
Variable Theory ◽  
Rate Laws ◽  
Flow Potential ◽  
Internal Variable Theory

AbstractIn the kinetic rate laws of internal variables, it is usually assumed that the rates of internal variables depend on the conjugate forces of the internal variables and the state variables. The dependence on the conjugate force has been fully addressed around flow potential functions. The kinetic rate laws can be formulated with two potential functions, the free energy function and the flow potential function. The dependence on the state variables has not been well addressed. Motivated by the previous study on the asymptotic stability of the internal variable theory by J. R. Rice, the thermodynamic significance of the dependence on the state variables is addressed in this paper. It is shown in this paper that the kinetic rate laws can be formulated by one extended potential function defined in an extended state space if the rates of internal variables do not depend explicitly on the internal variables. The extended state space is spanned by the state variables and the rate of internal variables. Furthermore, if the rates of internal variables do not depend explicitly on state variables, an extended Gibbs equation can be established based on the extended potential function, from which all constitutive equations can be recovered. This work may be considered as a certain Lagrangian formulation of the internal variable theory.

Role of Dissipation Characteristics in Predicting Flow from Dissimilar Centrifugal Pumps

1994 ◽  
Vol 208 (4) ◽  
pp. 285-294 ◽  
Author(s):  
E A Bunt ◽  
B Parsons ◽  
F Holtzhausen
Keyword(s):  
Flow Characteristics ◽  
Maximum Flow ◽  
Centrifugal Pumps ◽  
Graphical Solution ◽  
Dissipative Flow ◽  
In Series ◽  
Lower Maximum ◽  
Output Field ◽  
High Series

Examination of flows in a particular case of dissimilar pumps coupled in series or in parallel (without check valves) showed that the ‘classical’ graphical solution of combined characteristics in the [+H, +Q] quadrant did not accord with the output field in certain regions. To predict the full flow fields, it was necessary to take into account dissipative flow characteristics in two other quadrants: for low-output parallel flow (when there is still flow available from the pump of higher head when the ‘weaker’ pump's flow has been reduced to zero), that in the [+H, –Q] quadrant; and for high series flow (after the output head of the pump of lower maximum flow has been reduced to zero), that in the [–H, +Q] quadrant. This problem does not arise when the pumps have identical characteristics.

Salivary peptide histatin 1 mediated cell adhesion: a possible role in mesenchymal-epithelial transition and in pathologies

2018 ◽  
Vol 399 (12) ◽  
pp. 1409-1419 ◽  
Author(s):  
Irene A. van Dijk ◽  
Enno C.I. Veerman ◽  
Eric A.J. Reits ◽  
Jan G.M. Bolscher ◽  
Jan Stap
Keyword(s):  
Cell Adhesion ◽  
Oral Cavity ◽  
Potential Function ◽  
Clinical Applications ◽  
Epithelial Barrier ◽  
Salivary Peptide ◽  
Mesenchymal To Epithelial Transition ◽  
Mesenchymal Epithelial Transition

Abstract Histatins are histidine-rich peptides present in the saliva of humans and higher primates and have been implicated in the protection of the oral cavity. Histatin 1 is one of the most abundant histatins and recent reports show that it has a stimulating effect on cellular adherence, thereby suggesting a role in maintaining the quality of the epithelial barrier and stimulating mesenchymal-to-epithelial transition. Here we summarize these findings and discuss them in the context of previous reports. The recent findings also provide new insights in the physiological functions of histatin 1, which are discussed here. Furthermore, we put forward a possible role of histatin 1 in various pathologies and its potential function in clinical applications.

Role of Plaque Morphology in Altering the Flow Characteristics in Diseased Coronary Artery

2012 ◽  
Author(s):  
Carlos Moreno ◽  
Kiran Bhaganagar
Keyword(s):  
Coronary Artery ◽  
Nonlinear Response ◽  
Flow Characteristics ◽  
Proximal Region ◽  
Patient Specific ◽  
Plaque Morphology ◽  
Mean Velocity ◽  
Peak Location ◽  
The Mean

Patient specific simulations of a single patient based on an accurate representation of the plaque in a diseased coronary artery with 35% stenosis are performed to understand the effect of inlet forcing frequency and amplitude on the wall shear stress (WSS). Numerical simulations are performed with unsteady flow conditions in a laminar regime. The results have revealed that at low amplitudes, WSS is insensitive to forcing frequency and is it in phase with Q. The maximum WSS is observed at the proximal region of the stenosis, and WSS has highest negative values at the peak location of the stenosis. For higher pulsatile amplitude (a > 1.0), WSS exhibits a strong sensitivity with forcing frequencies. At higher forcing frequency the WSS exhibits nonlinear response to the inlet forcing frequency. Furthermore, significant differences in the mean velocity profile are observed during maximum and minimum volumetric flow rates.

P–422 Acylglycerol Kinase is a new novel marker in preeclampsia

2021 ◽  
Vol 36 (Supplement_1) ◽  
Author(s):  
F Sun ◽  
Y Ma ◽  
Q Jie ◽  
Q Li
Keyword(s):  
Cell Proliferation ◽  
Potential Function ◽  
Formation Rate ◽  
Future Application ◽  
Migration And Invasion ◽  
Trophoblast Cells ◽  
Gain Of Function ◽  
Acylglycerol Kinase ◽  
Function Models

Abstract Study question What is the potential function of Acylglycerol Kinase (AGK) in the pathogenesis of preeclampsia(PE). Summary answer AGK plays an important role in the pathogenesis of PE by influencing the function of the trophoblast cells. What is known already PE is the leading cause of maternal and perinatal mortality and morbidity. The underlying mechanism is still not completely elucidated. Disorder migration, invasion and mitochondria function of trophoblast cells are one of mechanism in preeclampsia. AGK is a subunit of the mitochondrial channel protein complex TIM22, and maintain the stability of mitochondrial structure and function. Studies have shown that AGK is related to the development of various cancers by infecting the cells migration and invasion. It will be interesting to explore the potential function of AGK in the process of early trophoblast development and the pathogenesis of PE. Study design, size, duration Firstly, explore the expression of AGK in PE. Secondly, lentivirus systems was used to generate loss and gain of function models in trophoblast cell line-HTR8/Sneov to study the role of AGK in the pathogenesis of PE. Participants/materials, setting, methods We examined the expression of AGK both in placental tissues from PE patients and normal pregnant patients. Meanwhile, we generated AGK loss and gain of function models in HTR8/Sneov cells by using lentivirus systems. Transwell assays, scratch-wound assays, EDU and plate clone formation assays, cell apoptosis assays, cell cycle assays, ATP concentration, mtDNA level and transmission electron microscopy were used to examine the function of AGK in HTR8/Sneov cells model. Main results and the role of chance In this study, AGK was significantly decreased in the extra-villous trophoblast (EVT) cells in placental tissues of PE patients compared with that in control group by immunohistochemistry. And further confirmed the expression of AGK in placental tissues by QPCR, western blot. We demonstrated that knockdown of AGK in HTR8 dramatically decreased the cell proliferation, migration and invasion. It also showed the significantly lower plate clone formation rate in AGK knockdown -HTR8 cells compare with the WT HTR8 cells. While overexpression of AGK in HTR8 dramatically increased the cell proliferation, migration, invasion and higher plate clone formation rate. Further, we demonstrated that AGK regulated the ATP level and mtDNA level in HTR8 cells model. And we found that knockdown AGK decreased the number of mitochondria, and shown the mitochondrial crista disorder, mitochondrial swelling and dissolution and mitochondrial membrane fragmentation. While overexpression AGK increased the number of mitochondria. Limitations, reasons for caution Although we show that AGK played an important role in the function of HTR8, the study of working mechanism of AGK in PE is still very limited. More studies will be performed to explore its underline mechanism. Wider implications of the findings: This study was the first time to explore the role of AGK in PE. It will help us to better understand the pathogenesis of PE, which might be helpful in future application of novel therapeutic targets in PE. Trial registration number Not applicable

Modelling Liquid Flow Through Carbon Nanotubes

2013 ◽  
pp. 297-309
Author(s):  
Faig Bakhman Ogli Naghiyev
Keyword(s):  
Mass Transfer ◽  
Continuum Hypothesis ◽  
Flow Characteristics ◽  
Bingham Fluid ◽  
Length Scale ◽  
Review Of The Literature ◽  
Nanoscale Systems ◽  
Flow Through ◽  
Intermolecular Distances ◽  
Moving Fluid

In this paper, the structure of a liquid and character of its flow in carbon nanotube is investigated. A review of the literature and the results of experiments show that the simulation of fluid flow for nanoscale systems should be based on the continuum hypothesis taking into account the quantized character of the liquid in the length scale of intermolecular distances. Consideration of the flow characteristics allowed construction of the analogy of behavior of the liquid in a nanotube with a flow of a viscoplastic Bingham fluid. A model of mass transfer of liquid in a nanotube, based on the possibility of forming an empty interlayer between the moving fluid particles and the particles of the wall of the nanotube, is presented.

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