scholarly journals Variation of Streaming Potentials with Time under Steady Fluid Pressure in Bone

2019 ◽  
Vol 9 (18) ◽  
pp. 3726
Author(s):  
Liu ◽  
Hou ◽  
Qin ◽  
Fu ◽  
Pan
Keyword(s):  
Theoretical Model ◽  
Fluid Pressure ◽  
Fluid Flows ◽  
Experimental Setup ◽  
Viscous Resistance ◽  
Streaming Potentials ◽  
Charge Densities ◽  
Holding Period ◽  
Plate Specimen ◽  
Haversian Canals

This paper investigates the streaming potentials’ behaviors when fluid flows through the micropores in bone. An experimental setup was developed for measuring the streaming potentials between two surfaces of a bone plate specimen. It was found that the streaming potentials measured increased almost linearly with time under a constant fluid pressure gradient, which does not agree with the prediction from the classical theory of streaming potentials. To explain the reasons associated with the results obtained, a theoretical model was proposed in which the electric charge densities on the inner surfaces of the capillary are unevenly distributed. A formula was developed for solving the model, and the solutions demonstrate that nonuniform accumulations of electric charges carried by the fluid on the inner surfaces of the microcanals in bone can induce streaming potentials which linearly increase with time during the driving air pressure holding period. This phenomenon represents the specific characteristics of bone. The solution implies that the streaming potentials in Haversian canals, lacunas and canaliculi are not affected by electro-viscous resistance in the bone fluid.

The surface charge on manganese dioxides

Soil Research ◽  
1981 ◽  
Vol 19 (1) ◽  
pp. 41 ◽  
Author(s):  
RM McKenzie
Keyword(s):  
Theoretical Model ◽  
Surface Charge ◽  
Charge Densities

Surface charge was measured on four synthetic manganese dioxides. Charge densities on two cryptomelanes followed closely the values predicted by a theoretical model. Charge densities on two birnessites were much higher, and did not fit the model.

Thermodynamic Properties of Fluids

1997 ◽  
Author(s):  
David Jon Furbish
Keyword(s):  
Mechanical Energy ◽  
Fluid Pressure ◽  
Fluid Flows ◽  
Thermal Conditions ◽  
Fluid Viscosity ◽  
Frozen Ground ◽  
Patterned Ground ◽  
Fluid Behavior ◽  
Fluid Properties ◽  
Convective Motions

Fluid behavior in many geological problems is strongly influenced by extant thermal conditions and flow of heat. Recall, for example, that the coefficient A in Glen’s law for ice (3.40) varies over three orders of magnitude with a change in temperature of 50 °C. The effect of this is to strongly modulate the rate of ice deformation for a given level of stress. Recall further that we introduced several fluid properties—fluid compressibility, for example—where we asserted that our purely mechanical developments were incomplete inasmuch as they did not treat effects of varying temperature. The reasons for this will become clear in this chapter, including why it is difficult to maintain isothermal conditions when the pressure of a fluid is changing. In addition, many geological problems involve fluid flows that are induced by effects of variations in thermal conditions over time and space. These include buoyancy-driven convective motions that arise from variations in fluid density associated with variations in temperature (Chapter 16). Specific examples include convective overturning in a magma chamber, which can significantly influence how crystallizing minerals are distributed; convective circulations of water and chemical solutions in a sedimentary basin, which can influence where rock materials are dissolved and where they are precipitated as cements within pores; and convective circulation of water within the active layer above seasonally frozen ground, which may influence where patterned ground develops in periglacial environments. These processes, and viscous flows in general, invariably involve conversions of mechanical energy to heat, or vice versa. So in considering problems involving heat energy, we should recall from introductory chemistry and physics that such conversions can involve work performed on the fluid or its surroundings, and anticipate that the effects of this ought be manifest in fluid behavior. This chapter, then, is concerned with fluid pressure, temperature, and density, and how these variables are related to heat, mechanical energy, and work. We will note in digressions how these macroscopic concepts, like fluid viscosity, often have clear interpretations at a molecular scale based on kinetic theory of matter.

CFD Analysis of a Continuous Inkjet Print Head for Direct Write Fabrication

2007 ◽  
Author(s):  
Salil Desai ◽  
Michael Lovell
Keyword(s):  
Dimensional Space ◽  
Fluid Pressure ◽  
Harsh Environments ◽  
Drop Formation ◽  
Experimental Setup ◽  
Direct Write ◽  
Cfd Analysis ◽  
Cfd Model ◽  
3 Dimensional ◽  
Miniaturized Devices

This paper investigates the fluid generation mechanism in a modified Continuous Inkjet Print (CIJ) method. The CIJ technique is utilized to deposit a variety of conductive nano particulate materials for building miniaturized devices that can sustain harsh environments. These include devices and structures that can sustain high temperature and humidity applications. Given the complex drop formation mechanism a CFD model is developed that is further validated using an ultrahigh speed photography experimental setup. Various input parameters such as frequency, voltage and fluid pressure can be tuned using the model for different fluid types to obtain an optimal drop formation. These findings can be useful for the fabrication of freeform miniaturized devices in 3 dimensional space.

Validation of a method for odor sampling on solid area sources

2012 ◽  
Vol 66 (8) ◽  
pp. 1607-1613 ◽  
Author(s):  
L. Capelli ◽  
S. Sironi ◽  
R. Barczak ◽  
M. Il Grande ◽  
R. Del Rosso
Keyword(s):  
Experimental Data ◽  
Theoretical Model ◽  
Wind Tunnel ◽  
Solid Surface ◽  
Laboratory Tests ◽  
Theoretical Data ◽  
Experimental Setup ◽  
Good Correspondence ◽  
Adopted Model ◽  
Solid Area

The aim of this paper is the study and the validation of a method for odor sampling on solid area sources. This aim is achieved by considering a suitable theoretical model that accounts for all the variables involved in the volatilization process of odorous compounds from solids into the atmosphere. The simulation of the emission of odors from a solid surface was achieved by designing a suitable experimental setup and a specific wind tunnel for laboratory tests. The results of the tests show a good correspondence between the theoretical data derived from the adopted model and the experimental data. The verification of the possibility of describing the wind tunnel functioning with a theoretical volatilization model proves the applicability of this device for sampling on solid area sources.

scholarly journals MODELING FLUID FLOWS IN DISTENSIBLE TUBES FOR APPLICATIONS IN HEMODYNAMICS

2013 ◽  
Vol 24 (05) ◽  
pp. 1350030 ◽  
Author(s):  
X. DESCOVICH ◽  
G. PONTRELLI ◽  
S. MELCHIONNA ◽  
S. SUCCI ◽  
S. WASSERTHEURER
Keyword(s):  
Fluid Pressure ◽  
Three Dimensional ◽  
Fluid Flows ◽  
Two Dimensional ◽  
Wall Deformation ◽  
Pulsatile Flows ◽  
Compliant Walls ◽  
Flow Pressure ◽  
Wall Perturbation ◽  
Bounce Back

We present a lattice Boltzmann (LB) model for the simulation of hemodynamic flows in the presence of compliant walls. The new scheme is based on the use of a continuous bounce-back boundary condition, as combined with a dynamic constitutive relation between the flow pressure at the wall and the resulting wall deformation. The method is demonstrated for the case of two-dimensional (axisymmetric) pulsatile flows, showing clear evidence of elastic wave propagation of the wall perturbation in response to the fluid pressure. The extension of the present two-dimensional axisymmetric formulation to more general three-dimensional geometries is currently under investigation.

scholarly journals Piezoresistive Conductive Microfluidic Membranes for Low-Cost On-Chip Pressure and Flow Sensing

2021 ◽  
Author(s):  
Md Nazibul Islam ◽  
Steven M Doria ◽  
Zachary R Gagnon
Keyword(s):  
Time Pressure ◽  
Low Cost ◽  
Fluid Pressure ◽  
Fluid Flows ◽  
Microfluidic Devices ◽  
Microfluidic Channels ◽  
Impedance Change ◽  
Conductive Membranes ◽  
Chip Fabrication ◽  
On Chip

Over the last two decades, microfluidics has received significant attention from both academia and industry, and researchers report thousands of new prototype devices each year for use in a broad range of environmental, pharmaceutical, and biomedical engineering applications. While lab-on-a-chip fabrication costs have continued to decrease, the hardware required for monitoring fluid flows within microfluidic devices themselves remains expensive and often cost prohibitive for researchers interested in starting a microfluidics project. As microfluidic devices become capable of handling complex fluidic systems, low-cost, precise and real time pressure and flow rate measurement capabilities has become increasingly important. While many labs use commercial platforms and sensor, these solutions can often cost thousands of dollars and can be too bulky for on-chip use. Here we present a new inexpensive and easy -to-use piezoresistive pressure and flow sensor that can be easily integrated into existing on-chip microfluidic channels. The sensor consists of PDMS-Carbon black conductive membranes and uses an impedance analyzer to measure impedance change due fluid pressure. The sensor costs several orders of magnitude less than existing commercial platforms and can monitor local fluid pressures and calculate flow rates based on pressure gradient.

Fuel Injection Scheme for a Compact Afterburner Without Flameholders

2007 ◽  
Author(s):  
Shai Birmaher ◽  
Philipp W. Zeller ◽  
Peter Wirfalt ◽  
Yedidia Neumeier ◽  
Ben T. Zinn
Keyword(s):  
Theoretical Model ◽  
Gas Turbine ◽  
Fuel Injection ◽  
State Of The Art ◽  
Combustion Process ◽  
Operating Conditions ◽  
Experimental Setup ◽  
Turbine Engine ◽  
Theoretical Predictions ◽  
Significant Length

State of the art afterburner combustion employs spray bars and flameholders in a long cavity, which adds significant length and weight to the engine and increases its observability. This paper presents a feasibility study for the development of a compact “prime and trigger” afterburner that eliminates the flameholders and reduces the length of the engine. In this concept, fuel is injected just upstream or in between the turbine stages in such a manner that upon exiting the turbine the fuel has evaporated and premixed with the flow without significant combustion, a process referred to as “priming”. Downstream of the turbine, combustion is initiated either through autoignition or by using a low power plasma radical generator being developed in a parallel investigation to “trigger” the combustion process. The prime and trigger injection and ignition scheme has been investigated using an experimental setup that simulates the operating conditions in a typical gas turbine engine. For this investigation, a trigger is not used, and combustion of the fuel occurs through autoignition. A physics-based theoretical model was developed to predict the location of autoignition for given flow and spray properties and injection locations. The theoretical predictions and the experimental results obtained using thermocouple measurements and CH* chemiluminescence confirm the feasibility of the prime and trigger concept by demonstrating the predictable and controlled autoignition of the afterburner fuel.

Numerical Simulation of Streaming Potentials Due to Deformation-Induced Hierarchical Flows in Cortical Bone

2000 ◽  
Vol 123 (1) ◽  
pp. 66-70 ◽  
Author(s):  
A. F. T. Mak ◽  
J. D. Zhang
Keyword(s):  
Bone Remodeling ◽  
Streaming Potential ◽  
Fluid Flows ◽  
Haversian Canal ◽  
Disuse Atrophy ◽  
Element Discretization ◽  
Streaming Potentials ◽  
Flow Channels ◽  
The Matrix ◽  
Correct Understanding

Bone is a very dynamic tissue capable of modifying its composition, microstructure, and overall geometry in response to the changing biomechanical needs. Streaming potential has been hypothesized as a mechanotransduction mechanism that may allow osteocytes to sense their biomechanical environment. A correct understanding of the mechanism for streaming potential will illuminate our understanding of bone remodeling, such as the remodeling associated with exercise hypertrophy, disuse atrophy, and the bone remodeling around implants. In the current research, a numerical model based on the finite element discretization is proposed to simulate the fluid flows through the complicated hierarchical flow system and to calculate the concomitant stress generated potential (SGP) as a result of applied mechanical loading. The lacunae–canaliculi and the matrix microporosity are modeled together as discrete one-dimensional flow channels superposed in a biphasic poroelastic matrix. The cusplike electric potential distribution surrounding the Haversian canal that was experimentally observed and reported in the literature earlier was successfully reproduced by the current numerical calculation.

Investigation of Pipe Strain Measurements in a Curved Wide Plate Specimen

2010 ◽  
Author(s):  
Stijn Hertele´ ◽  
Wim De Waele ◽  
Rudi Denys ◽  
Jeroen Van Wittenberghe ◽  
Matthias Verstraete
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Strain Measurement ◽  
Entire Range ◽  
Experimental Setup ◽  
Element Analysis ◽  
Widespread Application ◽  
Strain Measurements ◽  
Plate Specimen ◽  
Girth Welds

Throughout the last two decades, curved wide plate (CWP) tests have proven to be highly valuable to evaluate the strain capacity of defected girth welds. Despite its widespread application, the CWP test is not yet standardized. In particular, the effects of specimen geometry and deformation measurement setup on the measurement of pipe (remote) strain have not yet been thoroughly documented. Recently, Laboratory Soete published its ‘UGent’ guidelines for CWP testing, in which advice is given on the entire experimental setup. This paper elaborates a finite element analysis of the effect of the CWP specimen’s geometry on the strain measurement. It is found that, following the UGent guidelines and under the assumptions of the study, the geometry has a limited influence for the entire range of investigated materials and pipe dimensions. This indicates that meeting the UGent guidelines for CWP testing yields representative pipe strain measurements.

Seepage Mechanics Mechanism of Undercompacted Mudstone's Formation

2013 ◽  
Vol 459 ◽  
pp. 693-697 ◽  
Author(s):  
Chong Feng ◽  
Hua Cai
Keyword(s):  
Fluid Flow ◽  
Flow Regime ◽  
Oil And Gas ◽  
Fluid Pressure ◽  
Fluid Flows ◽  
Pore Fluid ◽  
Pore Fluid Pressure ◽  
Flow Through ◽  
Physical Quantities ◽  
Practical Sense

Buried mudstones general have undercompacted phenomenon. Undercompacted mudstones have the characteristics that the porosity and pore fluid pressure are abnormal bigger. In order to disclosure the seepage mechanics mechanism of undercompacted mudstones formation, this paper has summed up the seepage mechanics relationship when fluid flows through the mudstone, and has verified the relationships between the key physical quantities with the minimal pressure (pressure that can let the fluid flow in the mudstone) by the experiments in physics. This paper has also analysis the formations process of undercompacted mudstone. The result shows that, the flow regime of fluid in the mudstone is the low speed seepage, and it is not applicable by Darcy equation; the fluid what flow through the thick and heavy compacted mudstone has the big minimal pressure. At the beginning or during the deposit, the rule of fluid flow in the mudstone decides that the fluid inside of the mudstone is more difficult to flow out than the fluid surface of the mudstone, and the inside mudstone becomes undercompacted. Because of the undercompacted mudstone is more important for the exploration of oil and gas, it has theoretic and practical sense to analysis the formations mechanism of the undercompacted mudstone.

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