Elastohydrodynamic Analysis of an Elastomeric Hydraulic Rod Seal During Fully Transient Operation

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Azam Thatte ◽  
Richard F. Salant
Keyword(s):  
Shear Stress ◽  
Fluid Transport ◽  
Fluid Pressure ◽  
Hydraulic Fluid ◽  
Time Varying ◽  
Fluid Flow Rate ◽  
Transient Operation ◽  
Zone Length ◽  
Lip Seal ◽  
Sealing Zone

A soft elastohydrodynamic model of a reciprocating elastomeric hydraulic rod seal has been developed. It consists of coupled fluid mechanics, contact mechanics, and deformation analyses. The model has been used to analyze a U-cup lip seal in an injection molding application with a time-varying sealed pressure and rod velocity. Results include the histories of the hydraulic fluid flow rate, fluid transport, mean shear stress on rod, sealing zone length, and friction force on rod, as well as distributions of the fluid pressure, film thickness, and contact pressure.

Effects of heterogeneity on frictional-viscous deformation and the depth-extent of the seismogenic zone

2021 ◽  
Author(s):  
Ake Fagereng ◽  
Adam Beall
Keyword(s):  
Shear Stress ◽  
Yield Strength ◽  
Fault Zone ◽  
Fluid Pressure ◽  
Local Stress ◽  
Seismogenic Zone ◽  
Depth Range ◽  
Viscous Deformation ◽  
Viscosity Contrast ◽  
Depth Extent

<p>Current conceptual fault models define a seismogenic zone, where earthquakes nucleate, characterised by velocity-weakening fault rocks in a dominantly frictional regime. The base of the seismogenic zone is commonly inferred to coincide with a thermally controlled onset of velocity-strengthening slip or distributed viscous deformation. The top of the seismogenic zone may be determined by low-temperature diagenetic processes and the state of consolidation and alteration. Overall, the seismogenic zone is therefore described as bounded by transitions in frictional and rheological properties. These properties are relatively well-determined for monomineralic systems and simple, planar geometries; but, many exceptions, including deep earthquakes, slow slip, and shallow creep, imply processes involving compositional, structural, or environmental heterogeneities. We explore how such heterogeneities may alter the extent of the seismogenic zone.</p><p> </p><p>We consider mixed viscous-frictional deformation and suggest a simple rule of thumb to estimate the role of heterogeneities by a combination of the viscosity contrast within the fault, and the ratio between the bulk shear stress and the yield strength of the strongest fault zone component. In this model, slip behaviour can change dynamically in response to stress and strength variations with depth and time. We quantify the model numerically, and illustrate the idea with a few field-based examples: 1) earthquakes within the viscous regime, deeper than the thermally-controlled seismogenic zone, can be triggered by an increase in the ratio of shear stress to yield strength, either by increased fluid pressure or increased local stress; 2) there is commonly a depth range of transitional behaviour at the base of the seismogenic zone – the thickness of this zone increases markedly with increased viscosity contrast within the fault zone; and 3) fault zone weakening by phyllosilicate growth and foliation development increases viscosity ratio and decreases bulk shear stress, leading to efficient, stable, fault zone creep. These examples are not new interpretations or observations, but given the substantial complexity of heterogeneous fault zones, we suggest that a simplified, conceptual model based on basic strength and stress parameters is useful in describing and assessing the effect of heterogeneities on fault slip behaviour.         </p>

scholarly journals Development and analytical validation of a finite element model of fluid transport through osteochondral tissue

2020 ◽  
Author(s):  
Brady D. Hislop ◽  
Chelsea M. Heveran ◽  
Ronald K. June
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Fluid Transport ◽  
Fluid Pressure ◽  
Viscoelastic Model ◽  
Element Model ◽  
Pressure Gradients ◽  
Superficial Zone ◽  
Bone Interface ◽  
Osteochondral Tissue

AbstractFluid transport between cartilage and bone is critical to joint health. The objective of this study was to develop and analytically validate a finite element model of osteochondral tissue capable of modeling cartilage-bone fluid transport. A biphasic viscoelastic model using an ellipsoidal fiber distribution was created with three distinct layers of cartilage (superficial zone, middle zone, and deep zone) along with a layer of subchondral bone. For stress-relaxation in unconfined compression, our results for compressive stress, radial stress, effective fluid pressure, and elastic recoil were compared with established biphasic analytical solutions. Our model also shows the development of fluid pressure gradients at the cartilage-bone interface during loading. Fluid pressure gradients developed at the cartilage-bone interface with consistently higher pressures in cartilage following initial loading to 10% strain, followed by convergence towards equal pressures in cartilage and bone during the 400s relaxation period. These results provide additional evidence that fluid is transported between cartilage and bone during loading and improves upon estimates of the magnitude of this effect through incorporating a realistic distribution and estimate of the collagen ultrastructure. Understanding fluid transport between cartilage and bone may be key to new insights about the mechanical and biological environment of both tissues in health and disease.

Mechanical Impact Effects of Fluid Hammer Effects on Drag Reduction of Coiled Tubing

2021 ◽  
pp. 1-10
Author(s):  
Yongsheng Liu ◽  
Xing Qin ◽  
Yuchen Sun ◽  
Zijun Dou ◽  
Jiansong Zhang ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Drag Reduction ◽  
Flow Rate ◽  
Fluid Velocity ◽  
Fluid Pressure ◽  
Great Influence ◽  
Radial Force ◽  
Fluid Flow Rate ◽  
Normal Contact ◽  
Coiled Tubing

Abstract Aiming at the oscillation drag reduction tool that improves the extension limit of coiled tubing downhole operations, the fluid hammer equation of the oscillation drag reducer is established based on the fluid hammer effect. The fluid hammer equation is solved by the asymptotic method, and the distribution of fluid pressure and flow velocity in coiled tubing with oscillation drag reducers is obtained. At the same time, the axial force and radial force of the coiled tubing caused by the fluid hammer oscillator are calculated according to the momentum theorem. The radial force will change the normal contact force of the coiled tubing which has a great influence on frictional drag. The results show that the fluid flow rate and pressure decrease stepwise from the oscillator position to the wellhead position, and the fluid flow rate and pressure will change abruptly during each valve opening and closing time. When the fluid passes through the oscillator, the unit mass fluid will generate an instantaneous axial tension due to the change in the fluid velocity, thereby converting the static friction into dynamic friction, which is conducive to the extend limit of coiled tubing.

Analysis of Flow Disturbance in a Stenosed Carotid Artery Bifurcation Using Two-Equation Transitional and Turbulence Models

2008 ◽  
Vol 130 (6) ◽  
Author(s):  
F. P. P. Tan ◽  
G. Soloperto ◽  
S. Bashford ◽  
N. B. Wood ◽  
S. Thom ◽  
...  
Keyword(s):  
Shear Stress ◽  
Carotid Artery ◽  
Laminar Flow ◽  
Wall Shear Stress ◽  
Turbulence Models ◽  
Carotid Bifurcation ◽  
Patient Specific ◽  
Shear Stresses ◽  
Zone Length ◽  
Wall Shear

In this study, newly developed two-equation turbulence models and transitional variants are employed for the prediction of blood flow patterns in a diseased carotid artery where the growth, progression, and structure of the plaque at rupture are closely linked to low and oscillating wall shear stresses. Moreover, the laminar-turbulent transition in the poststenotic zone can alter the separation zone length, wall shear stress, and pressure distribution over the plaque, with potential implications for stresses within the plaque. Following the validation with well established experimental measurements and numerical studies, a magnetic-resonance (MR) image-based model of the carotid bifurcation with 70% stenosis was reconstructed and simulated using realistic patient-specific conditions. Laminar flow, a correlation-based transitional version of Menter’s hybrid k‐ϵ∕k‐ω shear stress transport (SST) model and its “scale adaptive simulation” (SAS) variant were implemented in pulsatile simulations from which analyses of velocity profiles, wall shear stress, and turbulence intensity were conducted. In general, the transitional version of SST and its SAS variant are shown to give a better overall agreement than their standard counterparts with experimental data for pulsatile flow in an axisymmetric stenosed tube. For the patient-specific case reported, the wall shear stress analysis showed discernable differences between the laminar flow and SST transitional models but virtually no difference between the SST transitional model and its SAS variant.

Hydraulic Fluid Mathematical Modeling

2013 ◽  
Vol 432 ◽  
pp. 127-132
Author(s):  
Pei Cheng Shi ◽  
Yang Min Sun
Keyword(s):  
Hydraulic System ◽  
Fluid Pressure ◽  
Mathematical Expression ◽  
Effective Density ◽  
Hydraulic Fluid ◽  
Factors Affecting ◽  
Air Content ◽  
Linear Behavior ◽  
Study Results ◽  
Non Linear

In hydraulic system, the property of hydraulic fluid will have non-linear behavior change when the temperature and pressure of fluid and the amount of dissolved and undissolved air vary, thus influencing the hydraulic system performance. The authors first studied the property of hydraulic fluid, and then constructed the mathematical expression theoretically, which shows the hydraulic fluid effective density using the fluid pressure, temperature and air content parameters. The computation simulations of the hydraulic fluid non-linear property were carried out using the simulation program based on MATLAB software. Meanwhile the key-factors affecting the hydraulic effective density and fluid bulk modulus were discussed. The study results provide computing foundation for designing quickly responsive, running steady and highly accurate hydraulic transmission system, which have important theory and engineering significance.

Elastohydrodynamic Model of the Rotary Lip Seal

1996 ◽  
Vol 118 (2) ◽  
pp. 292-296 ◽  
Author(s):  
R. F. Salant
Keyword(s):  
Film Thickness ◽  
Simplified Model ◽  
Maximum Speed ◽  
Maximum Pressure ◽  
Lip Seal ◽  
Equilibrium Behavior ◽  
Lubricating Film ◽  
Pressure Distributions ◽  
Sealing Zone

A model of the non-leaking equilibrium behavior of the lip seal has been developed. It consists of an elastohydrodynamic model of the lubricating film and a simplified model of the meniscus on the air-side of the seal. The model predicts the location of the meniscus, the film thickness and pressure distributions, and the locations of cavitation regions. It also predicts the maximum pressure that can be sealed with zero leakage, and the maximum speed, above which the meniscus is ingested into the sealing zone.

Tissue Engineered Tumor Microvessels to Study the Role of Flow Shear Stress on Endothelial Barrier Function

2013 ◽  
Author(s):  
Cara F. Buchanan ◽  
Elizabeth Voigt ◽  
Pavlos P. Vlachos ◽  
Marissa Nichole Rylander
Keyword(s):  
Shear Stress ◽  
Growth Factors ◽  
Vascular Function ◽  
Fluid Pressure ◽  
Compressive Force ◽  
Lymphatic Drainage ◽  
Angiogenic Growth Factors ◽  
Flow Shear ◽  
Flow Shear Stress

As solid tumors develop, a variety of physical stresses arise including growth induced compressive force, matrix stiffening due to desmoplasia, and increased interstitial fluid pressure and altered flow patterns due to leaky vasculature and poor lymphatic drainage [1]. These microenvironmental stresses likely contribute to the abnormal cell behavior that drives tumor progression, and have become an increasingly significant area of cancer research. Of particular importance, is the role of flow shear stress on tumor-endothelial signaling, vascular function, and angiogenesis. Compared to normal vasculature, blood vessels in tumors are poorly functional due to dysregulated expression of angiogenic growth factors, such as vascular endothelial growth factor (VEGF) or the angiopoietins. Also, because of the abnormal vessel structure, blood velocities can be an order of magnitude lower than that of normal microvessels. Recently published work utilizing intravital microscopy to measure blood velocities in mouse mammary fat pad tumors, demonstrated for the first time that shear rate gradients in tumors may help guide branching and growth of new vessels [2]. However, much still remains unknown about how shear stress regulates endothelial organization, permeability, or expression of growth factors within the context of the tumor microenvironment.

Sign in / Sign up

Export Citation Format

Share Document