Experimental Techniques for Studying Poroelasticity in Brain Phantom Gels Under High Flow Microinfusion

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
O. Ivanchenko ◽  
N. Sindhwani ◽  
A. Linninger
Keyword(s):  
Fluid Flow ◽  
Hydraulic Conductivity ◽  
Computational Model ◽  
Alternative Pathway ◽  
Volumetric Strain ◽  
High Flow ◽  
Optical Methods ◽  
Solid Matrix ◽  
Convection Enhanced Delivery ◽  
Catheter Tip

Convection enhanced delivery is an attractive option for the treatment of several neurodegenerative diseases such as Parkinson, Alzheimer, and brain tumors. However, the occurrence of a backflow is a major problem impeding the widespread use of this technique. In this paper, we analyze experimentally the force impact of high flow microinfusion on the deformable gel matrix. To investigate these fluid structure interactions, two optical methods are reported. First, gel stresses during microinfusion were visualized through a linear polariscope. Second, the displacement field was tracked using 400 nm nanobeads as space markers. The corresponding strain and porosity fields were calculated from the experimental observations. Finally, experimental data were used to validate a computational model for fluid flow and deformation in soft porous media. Our studies demonstrate experimentally, the distribution and magnitude of stress and displacement fields near the catheter tip. The effect of fluid traction on porosity and hydraulic conductivity is analyzed. The increase in fluid content in the catheter vicinity enhances the gel hydraulic conductivity. Our computational model takes into account the changes in porosity and hydraulic conductivity. The simulations agree with experimental findings. The experiments quantified solid matrix deformation, due to fluid infusion. Maximum deformations occur in areas of relatively large fluid velocities leading to volumetric strain of the matrix, causing changes in hydraulic conductivity and porosity close to the catheter tip. The gradual expansion of this region with increased porosity leads to decreased hydraulic resistance that may also create an alternative pathway for fluid flow.

scholarly journals Upstream rheotaxis of catalytic Janus spheres

2021 ◽  
Author(s):  
Priyanka Sharan ◽  
Zuyao Xiao ◽  
Viviana Mancuso ◽  
William E. Uspal ◽  
Juliane Simmchen
Keyword(s):  
Fluid Flow ◽  
Type System ◽  
Shear Plane ◽  
High Flow ◽  
Physical Factors ◽  
Theoretical Studies ◽  
Directional Response ◽  
Swimming Pattern ◽  
Flow Speeds ◽  
Stream Migration

Fluid flow is ubiquitous in many environments that form habitats for microorganisms. The tendency of organisms to navigate towards or away from flow is termed rheotaxis. Therefore, it is not surprising that both biological and artificial microswimmers show responses to flows that are determined by the interplay of chemical and physical factors. In particular, to deepen understanding of how different systems respond to flows, it is crucial to comprehend the influence played by swimming pattern. In recent studies, pusher-type Janus particles exhibited cross-stream migration in externally applied flows. Earlier, theoretical studies predicted a positive rheotactic response for puller-type spherical Janus micromotors. To compare to a different swimmer, we introduce Cu@SiO2 micromotors that swim towards their catalytic cap. Based on experimental observations, and supported by flow field calculations using a model for self-electrophoresis, we hypothesize that they behave effectively as a puller-type system. We investigate the effect of externally imposed flow on these spherically symmetrical Cu@SiO2 active Janus colloids, and we indeedobserve a steady upstream directional response. Through a simple squirmer model for a puller, we recover the major experimental observations. Additionally, the model predicts a unique “jumping” behaviour for puller-type micro- motors at high flow speeds. Performing additional experiments at high flow speeds, we capture this phenomenon, in which the particles “roll” with their swimming axes aligned to the shear plane, in addition to being dragged down- stream by the fluid flow.

Transport Phenomena in Smectite Clay Explained by Considering Microstructural Features

1997 ◽  
Vol 506 ◽  
Author(s):  
Roland Pusch
Keyword(s):  
Hydraulic Conductivity ◽  
High Flow ◽  
Diffusive Transport ◽  
Transport Capacity ◽  
Microstructural Parameter ◽  
Flow Capacity ◽  
Natural Clays ◽  
Microstructural Data ◽  
Microstructural Homogeneity ◽  
Diffusive Capacity

ABSTRACTThe microstructure of clays controls their transport properties. This is concluded from comparing microstructural parameter data with the hydraulic conductivity and the ion diffusive transport capacity. Illitic clays contain a number of interacting open voids with a high flow capacity while natural smectite-rich clays are more homogeneous with smaller voids and a lower hydraulic conductivity than illitic clays with the same density. Artificially prepared smectitic clays, like those proposed for embedding canisters with highly radioactive waste, have a higher conductivity than natural clays with the same smectite content because the microstructural homogeneity of the artificial clays is less good.The anion diffusive transport capacity of smectite-rich clays with high density is much lower than that of clays with low density in contrast to the cation diffusive capacity. This is explained by using quantitative microstructural data.

Hydraulic Conductivity in Trunk Xylem of Elm, Ulmus Americana

IAWA Journal ◽  
1985 ◽  
Vol 6 (4) ◽  
pp. 303-307 ◽  
Author(s):  
George S. Ellmore ◽  
Frank W. Ewers
Keyword(s):  
Fluid Flow ◽  
Hydraulic Conductivity ◽  
Fluid Transport ◽  
Growth Ring ◽  
Theoretical Calculations ◽  
Transport Pathway ◽  
Growth Rings ◽  
Ulmus Americana ◽  
Xylem Transport ◽  
Flow Through

The notion that most xylem transport in stems of ring-porous trees occurs in the outermost growth ring requires experimental support. Significance of this ring is challenged by workers who find tracer dyes appearing in 4 to 8 growth rings rather than in only the outermost increment. We test the hypothesis that the outermost growth ring is of overriding significance in fluid transport through stems of Ulmus, a ring-porous tree. Fluid flow through the outermost ring was quantified by removing that ring, calculating gravity flow rates (hydraulic conductivity at 10.13 kPa m-1 ), and by tracing the transport pathway through control and experimental stem segments. From measurements corroborating theoretical calculations based on Poiseuille's law, over 90% of fluid flow through the stem occurs through the outermost ring. Remaining rings combine to account for less than 10% of xylem transport. As a result of dependence upon transport in the most superficial xylem, ring-porous trees such as elm, oak, ash, and chestnut are particularly susceptible to xylem pathogens entering from the bark.

Streaming Potential Induced by Canaliculi Fluid Flow: A Fluid-Filled Thick-Walled Cylinder Osteon Model Subjected to Axial Loading

2010 ◽  
Vol 34-35 ◽  
pp. 117-122
Author(s):  
Xiao Gang Wu ◽  
Wei Yi Chen
Keyword(s):  
Fluid Flow ◽  
Streaming Potential ◽  
Axial Loading ◽  
Fluid Phase ◽  
Form Solution ◽  
Solid Matrix ◽  
Intraosseous Pressure ◽  
Elastic Transverse ◽  
Close Form ◽  
Walled Cylinder

Based on the physiological structure of osteon, a single fluid-filled osteon model under only time-dependent axial loading is modeled for calculating the streaming potential induced by canaliculi fluid flow. Solid matrix is modeled as an elastic transverse isotropic thick-walled cylinder and fluid phase is considered as an incompressible Newtonian fluid. Close-form solution of the streaming potential for a single osteon model was obtained and used to study the electromechanical properties on intraosseous pressure and potential distribution. The solution can also be used as a benchmark for numerical studies of other osteon models.

scholarly journals Influence of an intratumoral cyst on drug distribution by convection-enhanced delivery: case report

2017 ◽  
Vol 20 (3) ◽  
pp. 256-260 ◽  
Author(s):  
Iryna Ivasyk ◽  
Peter F. Morgenstern ◽  
Eva Wembacher-Schroeder ◽  
Mark M. Souweidane
Keyword(s):  
Drug Distribution ◽  
Diffuse Intrinsic Pontine Glioma ◽  
Positive Pressure ◽  
Target Point ◽  
Convection Enhanced Delivery ◽  
Clinical Trial Registration ◽  
Software Analysis ◽  
Catheter Tip ◽  
Cystic Cavity ◽  
Brainstem Tumors

Convection-enhanced delivery (CED) uses positive pressure to induce convective flow of molecules and maximize drug distribution. Concerns have been raised about the effect of cystic structures on uniform drug distribution with CED. The authors describe the case of a patient with a diffuse intrinsic pontine glioma (DIPG) with a large cyst and examine its effect on drug distribution after CED with a radiolabeled antibody. The patient was treated according to protocol with CED of 124I-8H9 to the pons for nonprogressive DIPG after radiation therapy as part of a Phase I trial (clinical trial registration no. NCT01502917, clinicaltrials.gov). Care was taken to avoid the cystic cavity in the planned catheter track and target point. Co-infusion with Gd-DTPA was performed to assess drug distribution. Infusate distribution was examined by MRI immediately following infusion and analyzed using iPlan Flow software. Analysis of postinfusion MR images demonstrated convective distribution around the catheter tip and an elongated configuration of drug distribution, consistent with the superoinferior corticospinal fiber orientation in the brainstem. This indicates that the catheter was functioning and a pressure gradient was established. No infusate entry into the cystic region could be identified on T2-weighted FLAIR or T1-weighted images. The effects of ependymal and pial surfaces on drug delivery using CED in brainstem tumors remain controversial. Drug distribution is a critical component of effective application of CED to neurosurgical lesions. This case suggests that cyst cavities may not always behave as fluid “sinks” for drug distribution. The authors observed that infusate was not lost into the cyst cavity, suggesting that lesions with cystic components can be treated by CED without significant alterations to target and infusion planning.

scholarly journals A Novel Numerical Model for Fluid Flow in 3D Fractured Porous Media Based on an Equivalent Matrix-Fracture Network

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Chi Yao ◽  
Chen He ◽  
Jianhua Yang ◽  
Qinghui Jiang ◽  
Jinsong Huang ◽  
...  
Keyword(s):  
Porous Media ◽  
Fluid Flow ◽  
Hydraulic Conductivity ◽  
Fractured Rock ◽  
Fracture Network ◽  
Numerical Approach ◽  
Porous Matrix ◽  
Fractured Porous Media ◽  
Hydraulic Aperture ◽  
Matrix Fracture

An original 3D numerical approach for fluid flow in fractured porous media is proposed. The whole research domain is discretized by the Delaunay tetrahedron based on the concept of node saturation. Tetrahedral blocks are impermeable, and fluid only flows through the interconnected interfaces between blocks. Fractures and the porous matrix are replaced by the triangular interface network, which is the so-called equivalent matrix-fracture network (EMFN). In this way, the three-dimensional seepage problem becomes a two-dimensional problem. The finite element method is used to solve the steady-state flow problem. The big finding is that the ratio of the macroconductivity of the whole interface network to the local conductivity of an interface is linearly related to the cubic root of the number of nodes used for mesh generation. A formula is presented to describe this relationship. With this formula, we can make sure that the EMFN produces the same macroscopic hydraulic conductivity as the intact rock. The approach is applied in a series of numerical tests to demonstrate its efficiency. Effects of the hydraulic aperture of fracture and connectivity of the fracture network on the effective hydraulic conductivity of fractured rock masses are systematically investigated.

An evaluation of the relationships between catheter design and tissue mechanics in achieving high-flow convection-enhanced delivery

2011 ◽  
Vol 199 (1) ◽  
pp. 87-97 ◽  
Author(s):  
Edward White ◽  
Alison Bienemann ◽  
John Malone ◽  
Lisa Megraw ◽  
Chotirote Bunnun ◽  
...  
Keyword(s):  
Tissue Mechanics ◽  
High Flow ◽  
Convection Enhanced Delivery ◽  
Catheter Design

Effect of plastic fragments on hydraulic characteristics of pretreated municipal solid waste

2006 ◽  
Vol 43 (12) ◽  
pp. 1333-1343 ◽  
Author(s):  
Mingliang Xie ◽  
Dirk Aldenkortt ◽  
Jean-Frank Wagner ◽  
Gerhard Rettenberger
Keyword(s):  
Fluid Flow ◽  
Hydraulic Conductivity ◽  
Municipal Solid Waste ◽  
Solid Waste ◽  
Conceptual Model ◽  
Hydraulic Properties ◽  
Thin Sheet ◽  
Biological Pretreatment ◽  
Soil Material

A systematic study was undertaken of the granular composition and hydraulic properties of municipal solid waste (MSW) produced by mechanical–biological pretreatment (MBP–MSW) from three different treatment plants with the aim of evaluating the potential application of MBP–MSW as an alternative barrier material for landfill final cover systems. Despite its coarse granular composition, MBP–MSW has low hydraulic conductivity. Long-term permeability tests show that the hydraulic conductivity decreases with time. The most likely explanation for the long-term changes in permeability is the swelling of organic material contained within the compost. In the case of saturated flow, the virtually impermeable plastic fragments embedded in the material impede fluid flow. In the unsaturated case, such fragments slow down the drying process by disrupting fluid flow and allowing pooling of water above horizontally oriented fragments. The larger the number and size of the plastic fragments, the greater the influence on hydraulic conductivity and shrinkage. These processes can be better understood with the newly developed conceptual model, the thin-sheet model. Based on this conceptual model, laboratory tests were undertaken to compare natural soil material with mixtures of soil material and plastic fragments. Corresponding numerical simulations of some experiments verified the influence of plastic fragments on the hydraulic properties of MBP–MSW.Key words: mechanical–biological pretreatment, municipal solid waste (MSW), thin-sheet model, plastic fragment, hydraulic conductivity, drying test.

scholarly journals Preferential Pathways for Fluid and Solutes in Heterogeneous Groundwater Systems: Self-Organization, Entropy, Work

2021 ◽  
Author(s):  
Erwin Zehe ◽  
Ralf Loritz ◽  
Yaniv Edery ◽  
Brian Berkowitz
Keyword(s):  
Fluid Flow ◽  
Steady State ◽  
Hydraulic Conductivity ◽  
Solute Transport ◽  
Energy Input ◽  
Self Organization ◽  
Saturated Porous Media ◽  
Concentration Gradients ◽  
Transport Pathways ◽  
Preferential Pathways

Abstract. Patterns of distinct preferential pathways for fluid flow and solute transport are ubiquitous in heterogeneous, saturated and partially saturated porous media. Yet, the underlying reasons for their emergence, and their characterization and quantification, remain enigmatic. Here we analyze simulations of steady state fluid flow and solute transport in two-dimensional, heterogeneous saturated porous media with a relatively short correlation length. We demonstrate that the downstream concentration of solutes in preferential pathways implies a downstream declining entropy in the transverse distribution of solute transport pathways. This reflects the associated formation and downstream steepening of a concentration gradient transversal to the main flow direction. With an increasing variance of the hydraulic conductivity field, stronger transversal concentration gradients emerge, which is reflected in an even smaller entropy of the transversal distribution of transport pathways. By defining "self-organization" through a reduction in entropy (compared to its maximum), our findings suggest that a higher variance and thus randomness of the hydraulic conductivity coincides with stronger macroscale self-organization of transport pathways. While this finding appears at first sight striking, it can be explained by recognizing that emergence of spatial self-organization requires, in light of the second law of thermodynamics, that work be performed to establish transversal concentration gradients. The emergence of steeper concentration gradients requires that even more work be performed, with an even higher energy input into an open system. Consistently, we find that the energy input necessary to sustain steady-state fluid flow and tracer transport grows with the variance of the hydraulic conductivity field as well. Solute particles prefer to move through pathways of very high power, and these pathways pass through bottlenecks of low hydraulic conductivity. This is because power depends on the squared spatial head gradient, which is in these simulations largest in regions of low hydraulic conductivity.

scholarly journals The Effect of Groove Shape on Molten Metal Flow Behaviour in Gas Metal Arc Welding

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7444
Author(s):  
Amin Ebrahimi ◽  
Aravind Babu ◽  
Chris R. Kleijn ◽  
Marcel J. M. Hermans ◽  
Ian M. Richardson
Keyword(s):  
Fluid Flow ◽  
Computational Model ◽  
Arc Welding ◽  
Gas Metal Arc Welding ◽  
Metal Flow ◽  
Groove Shape ◽  
Melt Pool ◽  
Numerical Predictions ◽  
Metal Arc Welding ◽  
Welding Processes

One of the challenges for development, qualification and optimisation of arc welding processes lies in characterising the complex melt-pool behaviour which exhibits highly non-linear responses to variations of process parameters. The present work presents a computational model to describe the melt-pool behaviour in root-pass gas metal arc welding (GMAW). Three-dimensional numerical simulations have been performed using an enhanced physics-based computational model to unravel the effect of groove shape on complex unsteady heat and fluid flow in GMAW. The influence of surface deformations on the magnitude and distribution of the heat input and the forces applied to the molten material were taken into account. Utilising this model, the complex thermal and fluid flow fields in melt pools were visualised and described for different groove shapes. Additionally, experiments were performed to validate the numerical predictions and the robustness of the present computational model is demonstrated. The model can be used to explore the physical effects of governing fluid flow and melt-pool stability during gas metal arc root welding.

Sign in / Sign up

Export Citation Format

Share Document