Stress-Induced Radial Pressure Gradients in Liquid-Filled Multiple Concentric Cylinders

1977 ◽  
Vol 44 (2) ◽  
pp. 218-221 ◽  
Author(s):  
M. Munro ◽  
K. Piekarski
Keyword(s):  
Hydrostatic Pressure ◽  
Pressure Gradient ◽  
Experimental Model ◽  
Analytical Model ◽  
Axial Loading ◽  
Radial Pressure ◽  
Pressure Gradients ◽  
Hydraulic Oil ◽  
Concentric Cylinders ◽  
Good Agreement

The concept of liquid-filled multiple concentric cylinders under compressive axial loading is investigated. An analytical model to predict the hydrostatic pressures in the liquid regions is formulated. It is found that upon loading a radially decreasing pressure gradient in the liquid layers is produced. The values of hydrostatic pressure from an experimental model comprising aluminum cylinders filled with hydraulic oil show good agreement with those predicted by the analytical model.

The mechanism of water absorption by roots I. Preliminary studies on the effects of hydrostatic pressure gradients

1957 ◽  
Vol 147 (928) ◽  
pp. 367-380 ◽  
Keyword(s):  
Hydrostatic Pressure ◽  
Pressure Gradient ◽  
Mass Flow ◽  
Osmotic Potential ◽  
Permeability Coefficient ◽  
External Medium ◽  
External Pressure ◽  
Pressure Gradients ◽  
Unit Change ◽  
Direct Technique

During transpiration the hydrostatic tension which develops in the xylem conducting elements of the root draws water from the soil through the intervening tissues of the cortex, etc. It is uncertain whether this movement is entirely diffusional or in part a mass flow. To detect any such mass flow tomato plants grown in water culture were decapitated and placed in a canister through the lid of which the cut stem protruded and in which the pressure on the culture medium could be raised. The resulting rate of exudation (flux) was measured, and compared with the flux caused by an equivalent difference in osmotic potential obtained by measuring the ∆ f. p. of the medium and sap exuded. If these values of flux were equal, movement was by diffusion alone, but if pressure caused a greater flux, an additional mass flow was indicated. Preliminary experiments indicated a much greater flux in response to differences of pressure than osmotic potential, but accurate assessment of the effect was precluded by difficulties inherent in this straightforward approach. A less direct technique was therefore devised; the change in flux caused by changing the osmotic potential of the external medium (the hydrostatic pressure being maintained constant) was compared with the change in flux caused by changing the external pressure (the osmotic potential of the external medium being kept constant). The changes in flux were measured in such a way as to minimize changes in the osmotic potential in the xylem and in resistances to diffusion or mass flow respectively. In this way the change in flux per unit change in osmotic potential difference across the cortex (osmotic permeability coefficient, k 0 ) and the change in flux per unit change in pressure difference across the cortex (pressure permeability coefficient, k p ) could be compared under the same pressure gradient and in addition the effects of pressure gradients on k 0 could be studied. Thus, the effects of a pressure gradient on the diffusional movement of water could be assessed, as well as any mass flow component of the flux detected and measured.

scholarly journals Analytical modeling of bond stress at steel-concrete interface due to corrosion

2021 ◽  
Author(s):  
Luaay Hussein
Keyword(s):  
Bond Strength ◽  
Analytical Model ◽  
Outer Cylinder ◽  
Radial Pressure ◽  
Confining Pressure ◽  
Corrosion Products ◽  
Proposed Model ◽  
Corrosion Of Steel ◽  
Concrete Interface ◽  
Good Agreement

An analytical model that describes the deterioration of bond strength, due to corrosion of steel reinforcement, at the steel-concrete interface in a reinforced concrete is developed. Concrete is assumed as a thick-walled cylinder subjected to internal pressure exerted from the growth of corrosion products on the concrete at the steel-concrete interface. The concrete in the inner cylinder is considered as an anisotropic material with stiffness degradation factor as an exponential function, while at the outer cylinder, the concrete is treated as an isotropic material. A frictional model is used to combine the action of confining pressure resulted from radial pressure produced by principal bar ribs on surrounding concrete, and corrosion pressure resulted from the expansion of corrosion products. The results of the proposed model are validated with experimental results by several researchers and a good agreement was noted; this shows that the derived analytical model was able to satisfactory [sic] predict the reduction of bond strength between steel and concrete.

scholarly journals Analytical modeling of bond stress at steel-concrete interface due to corrosion

2021 ◽  
Author(s):  
Luaay Hussein
Keyword(s):  
Bond Strength ◽  
Analytical Model ◽  
Outer Cylinder ◽  
Radial Pressure ◽  
Confining Pressure ◽  
Corrosion Products ◽  
Proposed Model ◽  
Corrosion Of Steel ◽  
Concrete Interface ◽  
Good Agreement

An analytical model that describes the deterioration of bond strength, due to corrosion of steel reinforcement, at the steel-concrete interface in a reinforced concrete is developed. Concrete is assumed as a thick-walled cylinder subjected to internal pressure exerted from the growth of corrosion products on the concrete at the steel-concrete interface. The concrete in the inner cylinder is considered as an anisotropic material with stiffness degradation factor as an exponential function, while at the outer cylinder, the concrete is treated as an isotropic material. A frictional model is used to combine the action of confining pressure resulted from radial pressure produced by principal bar ribs on surrounding concrete, and corrosion pressure resulted from the expansion of corrosion products. The results of the proposed model are validated with experimental results by several researchers and a good agreement was noted; this shows that the derived analytical model was able to satisfactory [sic] predict the reduction of bond strength between steel and concrete.

scholarly journals Study of Influence of Width to Thickness Ratio in Sheet Metals on Bendability under Ambient and Superimposed Hydrostatic Pressure

2021 ◽  
Vol 2 (3) ◽  
pp. 542-558
Author(s):  
Mohammadmehdi Shahzamanian ◽  
David Lloyd ◽  
Amir Partovi ◽  
Peidong Wu
Keyword(s):  
Hydrostatic Pressure ◽  
Stress Ratio ◽  
Fracture Strain ◽  
Stress Triaxiality ◽  
Volumetric Strain ◽  
Thickness Ratio ◽  
Sheet Metals ◽  
The Finite Element Method ◽  
Bending Strain ◽  
Good Agreement

The effect of the width to thickness ratio on the bendability of sheet metal is investigated using the finite element method (FEM) employing the Gurson–Tvergaard–Needleman (GTN) model. Strain path changes in the sheet with change in the width/thickness ratio. It is shown that bendability and fracture strain increase significantly by decrease in the width/thickness ratio. The stress state is almost uniaxial when the stress ratio (α) is close to zero for narrow sheets. Stress ratio is nothing but the major stress to minor stress ratio. This delays the growth and coalescence of micro-voids as the volumetric strain and stress triaxiality (pressure/effective stress) decrease. On the other hand, ductility decreases with increase in α for wider sheets. Fracture bending strain is calculated and, as expected, it increases with decrease in the width/thickness ratio. Furthermore, a brief study is performed to understand the effect of superimposed hydrostatic pressure on fracture strain for various sheet metals with different width/thickness ratios. It is found that the superimposed hydrostatic pressure increases the ductility, and that the effect of the width/thickness ratio in metals on ductility is as significant as the effect of superimposed hydrostatic pressure. Numerical results are found to be in good agreement with experimental observations.

scholarly journals Determinants of valve gating in collecting lymphatic vessels from rat mesentery

2011 ◽  
Vol 301 (1) ◽  
pp. H48-H60 ◽  
Author(s):  
Michael J. Davis ◽  
Elaheh Rahbar ◽  
Anatoliy A. Gashev ◽  
David C. Zawieja ◽  
James E. Moore
Keyword(s):  
Pressure Gradient ◽  
Muscle Tone ◽  
Lymphatic Vessels ◽  
Vessel Diameter ◽  
Intraluminal Pressure ◽  
Pressure Gradients ◽  
Rat Mesentery ◽  
Temporal Relationships ◽  
Wide Range ◽  
Valve Opening

Secondary lymphatic valves are essential for minimizing backflow of lymph and are presumed to gate passively according to the instantaneous trans-valve pressure gradient. We hypothesized that valve gating is also modulated by vessel distention, which could alter leaflet stiffness and coaptation. To test this hypothesis, we devised protocols to measure the small pressure gradients required to open or close lymphatic valves and determine if the gradients varied as a function of vessel diameter. Lymphatic vessels were isolated from rat mesentery, cannulated, and pressurized using a servo-control system. Detection of valve leaflet position simultaneously with diameter and intraluminal pressure changes in two-valve segments revealed the detailed temporal relationships between these parameters during the lymphatic contraction cycle. The timing of valve movements was similar to that of cardiac valves, but only when lymphatic vessel afterload was elevated. The pressure gradients required to open or close a valve were determined in one-valve segments during slow, ramp-wise pressure elevation, either from the input or output side of the valve. Tests were conducted over a wide range of baseline pressures (and thus diameters) in passive vessels as well as in vessels with two levels of imposed tone. Surprisingly, the pressure gradient required for valve closure varied >20-fold (0.1–2.2 cmH2O) as a passive vessel progressively distended. Similarly, the pressure gradient required for valve opening varied sixfold with vessel distention. Finally, our functional evidence supports the concept that lymphatic muscle tone exerts an indirect effect on valve gating.

Protein osmotic pressure gradients and microvascular reflection coefficients

1997 ◽  
Vol 273 (2) ◽  
pp. H997-H1002 ◽  
Author(s):  
R. E. Drake ◽  
S. Dhother ◽  
R. A. Teague ◽  
J. C. Gabel
Keyword(s):  
Reflection Coefficient ◽  
Pressure Gradient ◽  
Osmotic Pressure ◽  
Reflection Coefficients ◽  
Pressure Gradients ◽  
Fluid Filtration ◽  
The Mean ◽  
Osmotic Reflection Coefficient ◽  
New Equation ◽  
Osmotic Pressure Gradient

Microvascular membranes are heteroporous, so the mean osmotic reflection coefficient for a microvascular membrane (sigma d) is a function of the reflection coefficient for each pore. Investigators have derived equations for sigma d based on the assumption that the protein osmotic pressure gradient across the membrane (delta II) does not vary from pore to pore. However, for most microvascular membranes, delta II probably does vary from pore to pore. In this study, we derived a new equation for sigma d. According to our equation, pore-to-pore differences in delta II increase the effect of small pores and decrease the effect of large pores on the overall membrane osmotic reflection coefficient. Thus sigma d for a heteroporous membrane may be much higher than previously derived equations indicate. Furthermore, pore-to-pore delta II differences increase the effect of plasma protein osmotic pressure to oppose microvascular fluid filtration.

scholarly journals Simulation Analysis on Water’s Micro Seepage Laws under Different Pressure Gradients Using Computed Tomography Method

2018 ◽  
Vol 2018 ◽  
pp. 1-26 ◽  
Author(s):  
Gang Zhou ◽  
Lei Qiu ◽  
Wenzheng Zhang ◽  
Jiao Xue
Keyword(s):  
Pressure Gradient ◽  
Mass Flow ◽  
Simulation Analysis ◽  
Effective Porosity ◽  
Pressure Gradients ◽  
Seepage Velocity ◽  
Average Mass ◽  
Depth Analysis ◽  
Tomography Method ◽  
Insight Into

The aim of this paper was to develop a model that can characterize the actual micropore structures in coal and gain an in-depth insight into water’s seepage rules in coal pores under different pressure gradients from a microscopic perspective. To achieve this goal, long-flame coals were first scanned by an X-ray 3D microscope; then, through a representative elementary volume (REV) analysis, the optimal side length was determined to be 60 μm; subsequently, by using Avizo software, the coal’s micropore structures were acquired. Considering that the porosity varies in the same coal sample, this study selected four regions in the sample for an in-depth analysis. Moreover, numerical simulations on water’s seepage behaviors in coal under 30 different pressure gradients were performed. The results show that (1) the variation of the simulated seepage velocity and pressure gradient accorded with Forchheimer’s high-velocity nonlinear seepage rules; (2) the permeability did not necessarily increase with the increase of the effective porosity; (3) in the same model, under different pressure gradients, the average seepage pressure decreased gradually, while the average seepage velocity and average mass flow varied greatly with the increase of the seepage length; and (4) under the same pressure gradient, the increase of the average mass flow from the inlet to the outlet became more significant under a higher inlet pressure.

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