scholarly journals The effect of ultrafiltration transmembrane permeation on the flow field in a surrogate system of an artificial kidney

2021 ◽  
Vol 2 ◽  
Author(s):  
Matilde De Pascale ◽  
Monica Faria ◽  
Cristiana Boi ◽  
Viriato Semiao ◽  
Maria Norberta de Pinho
Keyword(s):  
Pressure Drop ◽  
Artificial Kidney ◽  
Shear Stresses ◽  
Removal Rates ◽  
Permeable Membrane ◽  
Fluid Removal ◽  
Renal Replacement Therapies ◽  
Extracorporeal Blood Circulation ◽  
Conventional Hemodialysis ◽  
Upper Chamber

Abstract Renal Replacement Therapies generally associated to the Artificial Kidney (AK) are membrane-based treatments that assure the separation functions of the failing kidney in extracorporeal blood circulation. Their progress from conventional hemodialysis towards high-flux hemodialysis (HFHD) through the introduction of ultrafiltration membranes characterized by high convective permeation fluxes intensified the need of elucidating the effect of the membrane fluid removal rates on the increase of the potentially blood-traumatizing shear stresses developed adjacently to the membrane. The AK surrogate consisting of two-compartments separated by an ultrafiltration membrane is set to have water circulation in the upper chamber mimicking the blood flow rates and the membrane fluid removal rates typical of HFHD. Pressure drop mirrors the shear stresses quantification and the modification of the velocities profiles. The increase on pressure drop when comparing flows in slits with a permeable membrane and an impermeable wall is ca. 512% and 576% for $ \mathrm{CA}22/5\%{\mathrm{SiO}}_2 $ and $ \mathrm{CA}30/5\%{\mathrm{SiO}}_2 $ membranes, respectively.

scholarly journals Discovery of riblets in a bird beak ( Rynchops ) for low fluid drag

2016 ◽  
Vol 374 (2073) ◽  
pp. 20160134 ◽  
Author(s):  
Samuel Martin ◽  
Bharat Bhushan
Keyword(s):  
Pressure Drop ◽  
Drag Reduction ◽  
Shear Stresses ◽  
Structured Surfaces ◽  
Mako Shark ◽  
Fluid Drag ◽  
Bird Beak ◽  
Modelling Studies ◽  
Flow Pressure ◽  
First Time

Riblet structures found on fast-swimming shark scales, such as those found on a mako shark, have been shown to reduce fluid drag. In previous experimental and modelling studies, riblets have been shown to provide drag reduction by lifting vortices formed in turbulent flow, decreasing overall shear stresses. Skimmer birds ( Rynchops ) are the only birds to catch fish in flight by flying just above the water surface with a submerged beak to fish for food. Because they need to quickly catch prey, reducing drag on their beak is advantageous. For the first time, riblet structures found on the beak of the skimmer bird have been studied experimentally and computationally for low fluid drag properties. In this study, skimmer replicas were studied for drag reduction through pressure drop in closed-channel, turbulent water flow. Pressure drop measurements are compared for black and yellow skimmer beaks in two configurations, and mako shark skin. In addition, two configurations of skimmer beak were modelled to compare drag properties and vortex structures. Results are discussed, and a conceptual model is presented to explain a possible drag reduction mechanism in skimmers. This article is part of the themed issue ‘Bioinspired hierarchically structured surfaces for green science’.

scholarly journals Numerical Simulation of Dispersed Particle-Blood Flow in the Stenosed Coronary Arteries

2018 ◽  
Vol 2018 ◽  
pp. 1-16 ◽  
Author(s):  
Mongkol Kaewbumrung ◽  
Somsak Orankitjaroen ◽  
Pichit Boonkrong ◽  
Buraskorn Nuntadilok ◽  
Benchawan Wiwatanapataphee
Keyword(s):  
Numerical Simulation ◽  
Blood Flow ◽  
Shear Stress ◽  
Coronary Artery ◽  
Pressure Drop ◽  
Wall Shear Stress ◽  
Stokes Equations ◽  
Spherical Shape ◽  
Shear Stresses ◽  
Wall Shear

A mathematical model of dispersed bioparticle-blood flow through the stenosed coronary artery under the pulsatile boundary conditions is proposed. Blood is assumed to be an incompressible non-Newtonian fluid and its flow is considered as turbulence described by the Reynolds-averaged Navier-Stokes equations. Bioparticles are assumed to be spherical shape with the same density as blood, and their translation and rotational motions are governed by Newtonian equations. Impact of particle movement on the blood velocity, the pressure distribution, and the wall shear stress distribution in three different severity degrees of stenosis including 25%, 50%, and 75% are investigated through the numerical simulation using ANSYS 18.2. Increasing degree of stenosis severity results in higher values of the pressure drop and wall shear stresses. The higher level of bioparticle motion directly varies with the pressure drop and wall shear stress. The area of coronary artery with higher density of bioparticles also presents the higher wall shear stress.

scholarly journals Numerical Model to Predict Hemolysis and Transport in a Membrane-Based Microfluidic Device

2020 ◽  
Author(s):  
Matthew D Poskus ◽  
Thomas R Gaborski ◽  
Steven W Day
Keyword(s):  
Patient Outcomes ◽  
Shear Stresses ◽  
Device Performance ◽  
Flow Rates ◽  
Blood Damage ◽  
Damage Models ◽  
Conventional Hemodialysis ◽  
Prototype Design ◽  
Improve Patient

AbstractMicrofluidic devices may overcome the limitations of conventional hemodialysis and oxygenation technology to improve patient outcomes. Namely, the small form of this technology and parallel development of highly permeable membranes may facilitate the development of portable, low-volume, and efficient alternatives to conventional membrane-based equipment. However, the characteristically small dimensions of these devices may also inhibit transport and may also induce flow-mediated nonphysiologic shear stresses that may damage red blood cells (RBCs). In vitro testing is commonly used to quantify these phenomenon, but is costly and only characterizes bulk device performance. Here we developed a computational model that predicts the blood damage and solute transport for an abitrary microfluidic geometry. We challenged the predictiveness of the model with three geometric variants of a prototype design and validated hemolysis predictions with in vitro blood damge of prototype devices in a recirculating loop. We found that six of the nine tested damage models statistically agree with the experimental data for at least one geometric variant. Additionally, we found that one geometrical variant, the herringbone design, improved toxin (urea) transport to the dialysate by 38% in silico at the expense of a 50% increase in hemolysis. Our work demonstrates that computational modeling may supplement in vitro testing of prototype microdialyzer/micro-oxygenators to expedite the design optimization of these devices. Furthermore, the low device-induced blood damage measured in our study at physiologically relevant flow rates is promising for the future development of microfluidic dialyzers and oxygenators.

scholarly journals The effect to flow rate characteristic on biodegradation of bone scaffold

2017 ◽  
Vol 13 (4-2) ◽  
pp. 546-552 ◽  
Author(s):  
Hasan Basri ◽  
Jimmy Deswidawansyah Nasution ◽  
Ardiyansyah Syahrom ◽  
Mohd Ayub Sulong ◽  
Amir Putra Md. Saad ◽  
...  
Keyword(s):  
Shear Stress ◽  
Fluid Flow ◽  
Pressure Drop ◽  
Computational Models ◽  
Shear Stresses ◽  
Experimental Conditions ◽  
Flow Rates ◽  
Pressure Drops ◽  
Bone Scaffolds ◽  
Wall Shear

This paper proposes an improved modeling approach for bone scaffolds biodegradation. In this study, the numerical analysis procedure and computer-based simulation were performed for the bone scaffolds with varying porosities in determining the wall shear stresses and the permeabilities along with their influences on the scaffolds biodegradation process while the bio-fluids flow through within followed with the change in the flow rates. Based on the experimental study by immersion testing from 0 to 72 hours of the time period, the specimens with different morphologies of the commercial bone scaffolds were collected into three groups samples of 30%, 41%, and 55% porosities. As the representative of the cancellous bone morphology, the morphological degradation was observed by using 3-D CAD scaffold models based on microcomputed tomography images. By applying the boundary conditions to the computational fluid dynamics (CFD) and the fluid-structure interaction (FSI) models, the wall shear stresses within the scaffolds due to fluid flow rates variation had been simulated and determined before and after degradation. The increase of fluid flow rates tends to raise the pressure drop for scaffold models with porosities lower than 50% before degradation. As the porosities increases, the pressure drop decreases with an increase in permeability within the scaffold. The flow rates have significant effects on scaffolds with higher pressure drops by introducing the wall shear stresses with the highest values and lower permeability. These findings indicate the importance of using accurate computational models to estimate shear stress and determine experimental conditions in perfusion bioreactors for tissue engineering more accurate results will be achieved to indicate the natural distributions of fluid flow velocity, wall shear stress, and pressure.

A New Blood Module for Continuous Renal Replacement Therapies

1994 ◽  
Vol 17 (1) ◽  
pp. 14-18 ◽  
Author(s):  
C. Ronco ◽  
L. Fecondini ◽  
L. Gavioli ◽  
P. Conz ◽  
M. Milan ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Critically Ill Patients ◽  
Plasma Proteins ◽  
Continuous Measurement ◽  
Hollow Fibers ◽  
Treatment Efficiency ◽  
Renal Replacement Therapies ◽  
Safe Management ◽  
Continuous Renal Replacement Therapies ◽  
Post Filter

A new blood module for continuous renal replacement therapies has been utilized to perform CVVH in critically ill patients. The features of the new module named (HP300 and manifactured by Medica srl (Medolla, Modena) are the easy installation and transportability to the bedside, the simple and safe management and the continuous measurement of the pre and post filter pressure with automatic calculation of the end-to-end pressure drop inside the filter. The last feature permits to detect early malfunctions of the filter due to fibers clotting or due to the internal coating of the hollow fibers by plasma proteins. In both cases the efficiency of the treatment can be reduced because of a significant reduction of the ultrafiltration rates or a remarkable decay of the membrane permeability and solute sieving coefficients. In many cases this reduction is only detected when important effects on solute removal have already occurred. In our experience, the new module permitted the substitution of the filters when early malfunctions were detected and maximal treatment efficiency was therefore guaranteed over extended periods of time.

Annular Two-Phase Flow—Part 1: A Simple Theory

1970 ◽  
Vol 92 (1) ◽  
pp. 59-72 ◽  
Author(s):  
G. B. Wallis
Keyword(s):  
Pressure Drop ◽  
Two Phase Flow ◽  
Simple Theory ◽  
Shear Stresses ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Regime Transition ◽  
Flow Part ◽  
Numerous Data ◽  
Wall Shear

A simple theory for annular two-phase flow is developed in terms of equations for the interfacial and wall shear stresses. Expressions for the pressure drop and void fraction are derived. Criteria for the minimum pressure drop, zero wall shear, and flow regime transition in vertical flow are given. The results are compared with numerous data and alternative theories from the literature.

scholarly journals Control system for glucose level regulation in peritoneal dialysis

2021 ◽  
Vol 2091 (1) ◽  
pp. 012019
Author(s):  
N M Zhilo ◽  
E L Litinskaia ◽  
N A Bazaev
Keyword(s):  
Peritoneal Dialysis ◽  
Control System ◽  
Glucose Concentration ◽  
Removal Rate ◽  
Artificial Kidney ◽  
Automatic Regulation ◽  
Fluid Removal ◽  
Dialysis Solution ◽  
Water Salt ◽  
Dialysate Solution

Abstract Kidney failure leads to the serious health issues associated with abnormal water-salt balance. In this case, peritoneal dialysis therapy is often prescribed: 1-2 liters of dialysis solution is administered in peritoneal cavity for 3-4 hours. During this time, due to diffusion and osmosis, toxins and excess water are transferred from blood to solution. One of the method’s downsides is the transition of glucose (osmotic agent) into the bloodstream, which leads to a gradual decrease in the fluid removal rate. To mitigate this problem, one must use the system, which will measure current glucose concentration and inject glucose into solution to compensate absorption. The paper proposes such a control system for automatic regulation of the glucose concentration in peritoneal dialysate solution. Its structure, elements, their functions and characteristics are discussed. Proposed system is capable to work autonomously or can be incorporated into wearable “artificial kidney” device.

scholarly journals Galerkin Approach for the Study of Urea Concentration Distribution in Artificial Kidney in Hemodialysis

2020 ◽  
Vol 15 (1) ◽  
pp. 210-217
Author(s):  
Mina Gumanju ◽  
Dil Bahadur Gurung
Keyword(s):  
Differential Equation ◽  
Partial Differential Equation ◽  
Flow Velocity ◽  
Concentration Distribution ◽  
Waste Product ◽  
Galerkin Approximation ◽  
Urea Concentration ◽  
Artificial Kidney ◽  
Permeable Membrane ◽  
Galerkin Approach

 Hemodialysis is the process of purifying the blood which removes the waste product such as urea from blood through the semi-permeable membrane of dialyzer. In dialyzer, the rate of blood flow velocity is maintained around five times less than the dialyzed flow velocity during hemodialysis. The study focuses on the urea concentration distribution in the blood during dialysis using partial differential equation of diffusion process developed by J. N. Kapur, assuming blood is Newtonian, and laminar flow. The solution of urea concentration is obtained using Galerkin approximation method associated with appropriate boundary conditions.

Determination of the Pressure Drop Optimum Pipe Size for a Two-Phase Slug Flow in an Inclined Pipe

1970 ◽  
Vol 92 (4) ◽  
pp. 717-726 ◽  
Author(s):  
G. Singh ◽  
P. Griffith
Keyword(s):  
Pressure Drop ◽  
Pressure Gradient ◽  
Slug Flow ◽  
Total Pressure ◽  
Model Parameters ◽  
Shear Stresses ◽  
Water Mixture ◽  
Two Phase ◽  
Inclined Pipe ◽  
Pipe Size

A simple model of two-phase slug flow in inclined pipes is proposed. The model parameters are determined experimentally using five different size copper pipes at 5, 10, 15 deg inclinations on an air-water mixture at one atmosphere with up flow. The model predicts the total pressure gradient due to the sum of gravity and wall shear stresses. An investigation of the relationship between pressure gradient and pipe size results in an optimum pipe size at which the pressure gradient is minimum. A comparison between the simplified model predictions and experimental measurements shows a good agreement in the total pressure drop.

scholarly journals Comparative study of heat transfer and pressure drop during flow boiling and flow condensation in minichannels

2014 ◽  
Vol 35 (3) ◽  
pp. 17-37 ◽  
Author(s):  
Dariusz Mikielewicz ◽  
Rafał Andrzejczyk ◽  
Blanka Jakubowska ◽  
Jarosław Mikielewicz
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Shear Stress ◽  
Pressure Drop ◽  
Flow Structure ◽  
Annular Flow ◽  
Flow Boiling ◽  
Bubble Nucleation ◽  
Shear Stresses ◽  
Flow Condensation

Abstract In the paper a method developed earlier by authors is applied to calculations of pressure drop and heat transfer coefficient for flow boiling and also flow condensation for some recent data collected from literature for such fluids as R404a, R600a, R290, R32,R134a, R1234yf and other. The modification of interface shear stresses between flow boiling and flow condensation in annular flow structure are considered through incorporation of the so called blowing parameter. The shear stress between vapor phase and liquid phase is generally a function of nonisothermal effects. The mechanism of modification of shear stresses at the vapor-liquid interface has been presented in detail. In case of annular flow it contributes to thickening and thinning of the liquid film, which corresponds to condensation and boiling respectively. There is also a different influence of heat flux on the modification of shear stress in the bubbly flow structure, where it affects bubble nucleation. In that case the effect of applied heat flux is considered. As a result a modified form of the two-phase flow multiplier is obtained, in which the nonadiabatic effect is clearly pronounced.

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