An Experimental and Numerical Study on Coaxial Extrusion of a Non-Newtonian Hydrogel Material

2021 ◽  
pp. 1-34
Author(s):  
Ilhan Yu ◽  
Roland K. Chen
Keyword(s):  
Newtonian Fluid ◽  
Flow Rate ◽  
Numerical Study ◽  
Flow Behavior ◽  
Extrusion Process ◽  
Pluronic F127 ◽  
Flow Rate Ratio ◽  
Guiding Principle ◽  
Fluid Behavior ◽  
The Stability

Abstract Coaxial extrusion is a commonly used process to manufacture tubular structures to mimic vascular systems in 3D bioprinting. In this study, the stability of coaxial extrusion of a non-Newtonian material, Pluronic F127, is investigated. The extrusion process is considered stable when the extrudate form a core-annular structure. When it is unstable, dripping or jetting of the inner fluid is observed. In this study, the effects of the viscosity ratio, flow rate ratio, and the non-Newtonian behaviors on the stability of the coaxial extrusion process are investigated experimentally and numerically. The results show that all three factors can affect the stability of the process. When the ratio of viscosities increases, the process becomes unstable. The extrusion process tends to be stable when the flow rate of the outer fluid is much higher than that of the inner fluid. When the overall flow rate decreases, due to the non-Newtonian fluid behavior, the extrusion process can become unstable. This study shows the interconnected relationship between viscosity, flow rate, and non-Newtonian fluid behaviors and their effects on the stability of the coaxial extrusion process. The non-Newtonian flow behavior needs to be considered when studying or using coaxial extrusion. This study also provides a guiding principle on how to alter extrusion parameters in order to achieve the desired flow pattern.

NEWTONIAN AND NON-NEWTONIAN BLOOD FLOW AT A 90∘-BIFURCATION OF THE CEREBRAL ARTERY: A COMPARATIVE STUDY OF FLUID VISCOSITY MODELS

2018 ◽  
Vol 18 (05) ◽  
pp. 1850043 ◽  
Author(s):  
S. V. FROLOV ◽  
S. V. SINDEEV ◽  
D. LIEPSCH ◽  
A. BALASSO ◽  
P. ARNOLD ◽  
...  
Keyword(s):  
Blood Flow ◽  
Newtonian Fluid ◽  
Flow Rate ◽  
Fluid Model ◽  
Cerebral Arteries ◽  
High Viscosity ◽  
Flow Rate Ratio ◽  
Parent Artery ◽  
Fluid Viscosity ◽  
Recirculating Flow

The majority of numerical simulations assumes blood as a Newtonian fluid due to an underestimation of the effect of non-Newtonian blood behavior on hemodynamics in the cerebral arteries. In the present study, we evaluated the effect of non-Newtonian blood properties on hemodynamics in the idealized 90[Formula: see text]-bifurcation model, using Newtonian and non-Newtonian fluids and different flow rate ratios between the parent artery and its branch. The proposed Local viscosity model was employed for high-precision representation of blood viscosity changes. The highest velocity differences were observed at zones with slow recirculating flow. During the systolic peak the average difference was 17–22%, whereas at the end of diastole the difference increased to 27–60% depending on the flow rate ratio. The main changes in the viscosity distribution were observed distal to the flow separation point, where the non-Newtonian fluid model produced 2.5 times higher viscosity. A presence of such high viscosity region substantially affected the size of the flow recirculation zone. The observed differences showed that non-Newtonian blood behavior had a significant effect on hemodynamic parameters and should be considered in the future studies of blood flow in cerebral arteries.

Scaling Behavior in Electrohydrodynamic Jetting of Polymeric Solutions

2019 ◽  
Author(s):  
Abhishek K. Singh ◽  
Kaushlendra Dubey ◽  
Rajiv K. Srivastava ◽  
Supreet Singh Bahga
Keyword(s):  
Flow Rate ◽  
Flow Behavior ◽  
Polymer Concentration ◽  
Viscoelastic Behavior ◽  
Scaling Behavior ◽  
Jet Stability ◽  
Polymeric Solutions ◽  
Newtonian Liquids ◽  
The Stability ◽  
Viscoelastic Liquids

Abstract An electrohydrodynamic (EHD) jet forms when a leaky-dielectric liquid issuing out of a needle is accelerated and stretched by electrostatic forces. Stability and scaling behavior of the EHD jet of polymeric solutions depend on electrostatics, fluid mechanics and rheology of the liquid. While EHD jetting of Newtonian liquids have been described in the literature, the effect of non-Newtonian rheology on EHD jetting is still not well-understood. Therefore, we present a detailed experimental investigation of the stability and scaling behavior of EHD jets of polymeric solutions that exhibit non-Newtonian flow behavior. The stability of cone-jet was analyzed by varying flow rate, electric field and polymer concentration. Experiments were performed for polymeric solutions of polycaprolactone (PCL) dissolved in acetic acid. Our experiments show that non-Newtonian viscoelastic behavior can significantly alter the stability characteristics of the EHD jet. We have found that increase of elasticity of polymeric solutions results in enhanced jet stability. Finally, we present the dependence of experimentally measured diameter dj of the EHD jet on the flow rate Q. Experimentally measured diameter of the EHD jet scales as dj ∼ Q0.65 for both Newtonian and non-Newtonian viscoelastic liquids, which can be attributed to dominant inertia forces in our experiment.

DIAGNOSTIC AND THERAPEUTIC TREATMENTS OF PLAQUES IN THE CAROTID BIFURCATION — STUDIES IN MODELS WITH STENTS AND FILTERS

2014 ◽  
Vol 14 (03) ◽  
pp. 1450030
Author(s):  
D. LIEPSCH ◽  
A. BALASSO ◽  
C. ZIMMER ◽  
H. BERGER ◽  
R. BURKHART ◽  
...  
Keyword(s):  
Flow Rate ◽  
Fluid Dynamic ◽  
Flow Behavior ◽  
Carotid Bifurcation ◽  
Flow Rate Ratio ◽  
Shear Stresses ◽  
Dynamic Factors ◽  
Rate Ratios ◽  
Visualization Techniques

Fluid dynamics, especially forces and velocity distribution, influence the development of plaques. Flow parameters: pulsatility, the non-Newtonian flow behavior of blood and wall elasticity are considered. Flow visualization techniques (dyes and birefringent solution with a photo-elasticity apparatus) and LDA measurements demonstrate the importance of the flow. Accurate in vivo velocity measurements are necessary to calculate shear stresses. Different bifurcation angles and flow rate ratios were tested in true to life artery models. The most important fluid dynamic factors at bifurcations are the flow rate ratio and the geometry which create flow separation regions which are responsible for platelet aggregation and intima damage. It is necessary to measure all three velocity components to calculate the velocity vector. The highest shear stresses in a healthy carotid artery are 16 Pa and are found just at the apex. In artery models with 90% stenosis, shear stresses up to 250 Pa were found. Distally, vortices were created where particles remained over several pulse cycles. Measurements show that stents must be selected carefully and placed precisely. Filters must be closed during the systolic phase before removal, so that no trapped particles can escape.

scholarly journals Numerical Study of the Winter–Kennedy Flow Measurement Method in Transient Flows

Energies ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1310
Author(s):  
Binaya Baidar ◽  
Jonathan Nicolle ◽  
Bhupendra K. Gandhi ◽  
Michel J. Cervantes
Keyword(s):  
Flow Rate ◽  
Transient Flow ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Cross Sectional ◽  
Transient Flows ◽  
Sectional Plane ◽  
The Stability ◽  
Opening And Closing ◽  
Spiral Casing

This paper explores the possibility of using the Winter–Kennedy (WK) method for transient flow rate measurement in hydraulic turbines. Computational fluid dynamic (CFD) analysis of a numerical model of an axial turbine was carried out for accelerating and decelerating flows. Those were obtained by linearly opening and closing of the guide vanes, respectively, while retaining the inlet pressure constant during the simulations. The behavior of several WK configurations on a cross-sectional plane and along the azimuthal direction of the spiral casing was studied during the transients. The study showed that there are certain WK configurations that are more stable than others. The physical mechanism behind the stability (or instability) of the WK method during transients is presented. Using the steady WK coefficient obtained at the best efficiency point (BEP), the WK method could estimate the transient flow rate with a deviation of about 7.5% and 3.5%, for accelerating and decelerating flow, respectively.

Changes in Carotid Artery Flow Velocities after Stent Implantation: A Fluid Dynamics Study with Laser Doppler Anemometry

2003 ◽  
Vol 10 (2) ◽  
pp. 275-284 ◽  
Author(s):  
Oliver Greil ◽  
Gottlieb Pflugbeil ◽  
Klaus Weigand ◽  
Wolfgang Weiß ◽  
Dieter Liepsch ◽  
...  
Keyword(s):  
Carotid Artery ◽  
Flow Rate ◽  
Rate Ratio ◽  
Laser Doppler Anemometry ◽  
Flow Behavior ◽  
Laser Doppler ◽  
Flow Rate Ratio ◽  
External Carotid ◽  
Flow Profile ◽  
Separation Zones

Purpose: To study the influence of stent size and location on flow patterns in a physiological carotid model. Methods: Wallstents were positioned in silicon models of the carotid artery at various locations: 2 stents appropriately sized to the anatomy were placed in (1) the internal carotid artery (ICA) and (2) the ICA extending completely into the common carotid artery so as to cover the external carotid artery (ECA) orifice. Another 2 stents were placed in the ICA extending (1) partially and (2) completely into the bulb to simulate stent displacement and disproportion between stent size and the original vessel geometry. Measurements were performed with laser Doppler anemometry (LDA) using pulsatile flow conditions (Reynolds number=250; flow 0.431 L/min; ICA:ECA flow rate ratio 70:30) in hemodynamically relevant cross sections. The hemodynamic changes were analyzed with 1-dimensional flow profiles. Results: With the stent in the ICA, no changes of the normal flow profile were seen. For stents positioned in the ICA and extending partially or completely into the carotid bulb, the flow behavior was affected by the resistance of the stent to flow in the ECA. Hemodynamically relevant disturbances were seen in the ICA and ECA, especially in the separation zones (regions along the walls just after a bifurcation, bend, or curve). The ICA:ECA flow rate ratios shifted from 70:30 to 71.3:28.7 and from 70:30 to 75.1:24.9, respectively, in the 2 malpositioned stent models. With the stent placed in the ICA extending completely into the CCA, the ICA:ECA flow rate ratio shifted from 70:30 to 72.4:27.6. In this configuration, there were no notable flow changes in the ICA, but a clear diminishing of the separation zones in the ECA separation zones. Conclusions: Anatomically correct positioning of appropriately sized stents does not lead to relevant flow disturbances in the ICA. In the ECA, depending on the position, size, and interstices of the stent, the physiological flow was considerably disturbed when any part of the stent covered the inflow of the vessel. Disturbances were seen when the stent was positioned into the bulb. For clinical application, stent location and size must be carefully determined so that the stent covers the bifurcation completely or is in the ICA only.

Numerical Study of Fluid Behavior Induced by Anchor Impeller in a Stirred Vessel

2015 ◽  
Vol 789-790 ◽  
pp. 257-262
Author(s):  
Amine Benmoussa ◽  
Lakhdar Rahmani ◽  
Mebrouk Rebhi
Keyword(s):  
Yield Stress ◽  
Stokes Equations ◽  
Numerical Study ◽  
Flow Behavior ◽  
Navier Stokes ◽  
Rheological Parameters ◽  
Navier Stokes Equations ◽  
Stirred Vessel ◽  
Fluid Behavior ◽  
Basic Fluid

In the present paper, we have described in-depth numerical study of the basic fluid mechanics problem of yield stress fluid flow with regularization model of Berovier and Engelman in a cylindrical vessel not chicaned equipped with an anchor stirrer by using computational fluid dynamics (CFD) based on the finite volumes method discretization of Navier - Stokes equations formulated in variables (U.V.P). We study the effect of inertia and the yield stress influence by the variation of Hedström number on the flow; we have analyzed also the influence of rheological parameters on the hydrodynamic flow behavior, such as the velocity components and the power consumption.

Influence of Connection Geometry and SVC-IVC Flow Rate Ratio on Flow Structures within the Total Cavopulmonary Connection: A Numerical Study

2002 ◽  
Vol 124 (4) ◽  
pp. 364-377 ◽  
Author(s):  
Yottana Khunatorn ◽  
Shankar Mahalingam ◽  
Curt G. DeGroff ◽  
Robin Shandas
Keyword(s):  
Pressure Drop ◽  
Flow Rate ◽  
Rate Ratio ◽  
Numerical Study ◽  
Flow Rate Ratio ◽  
Flow Structures ◽  
Total Cavopulmonary Connection ◽  
Local Flow ◽  
Flow Parameters ◽  
Cavopulmonary Connection

The total cavopulmonary connection (TCPC) is a palliative cardiothoracic surgical procedure used in patients with one functioning ventricle that excludes the heart from the systemic venous to pulmonary artery pathway. Blood in the superior and inferior vena cavae (SVC, IVC) is diverted directly to the pulmonary arteries. Since only one ventricle is left in the circulation, minimizing pressure drop by optimizing connection geometry becomes crucial. Although there have been numerical and in–vitro studies documenting the effect of connection geometry on overall pressure drop, there is little published data examining the effect of SVC-IVC flow rate ratio on detailed fluid mechanical structures within the various connection geometries. We present here results from a numerical study of the TCPC connection, configured with various connections and SVC:IVC flow ratios. The role of major flow parameters: shear stress, secondary flow, recirculation regions, flow stagnation regions, and flow separation, was examined. Results show a complex interplay among connection geometry, flow rate ratio and the types and effects of the various flow parameters described above. Significant changes in flow structures affected local distribution of pressure, which in turn changed overall pressure drop. Likewise, changes in local flow structure also produced changes in maximum shear stress values; this may have consequences for platelet activation and thrombus formation in the clinical situation. This study sheds light on the local flow structures created by the various connections and flow configurations and as such, provides an additional step toward understanding the detailed fluid mechanical behavior of the more complex physiological configurations seen clinically.

scholarly journals Transient Flows of Newtonian Fluid through a Rectangular Microchannel with Slip Boundary

2014 ◽  
Vol 2014 ◽  
pp. 1-13 ◽  
Author(s):  
Benchawan Wiwatanapataphee ◽  
Yong Hong Wu ◽  
Suharsono Suharsono
Keyword(s):  
Pressure Gradient ◽  
Newtonian Fluid ◽  
Flow Rate ◽  
Transient Flow ◽  
Flow Behavior ◽  
Separation Of Variables ◽  
Fourier Series Expansion ◽  
Slip Parameter ◽  
Boundary Slip ◽  
Rectangular Microchannel

We study the transient flow of a Newtonian fluid in rectangular microchannels taking into account boundary slip. An exact solution is derived by using the separation of variables in space and Fourier series expansion in time. It is found that, for different forms of driving pressure field, the effect of boundary slip on the flow behavior is qualitatively different. If the pressure gradient is constant, the flow rate is almost linearly proportional to the slip parameterlwhenlis large; if the pressure gradient is in a waveform, as the slip parameterlincreases, the amplitude of the flow rate increases until approaching a constant value whenlbecomes sufficiently large.

scholarly journals Fabrication and Characterization of Carbon-Based Nanofluids through the Water Vortex Trap Method

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Ching-Min Cheng ◽  
Shang-Pang Yu ◽  
Tun-Ping Teng
Keyword(s):  
Electron Microscopy ◽  
Particle Size ◽  
Flow Rate ◽  
Rate Ratio ◽  
Near Infrared ◽  
Flow Rate Ratio ◽  
Future Research ◽  
Step Method ◽  
The Stability ◽  
Carbon Based

This study designed an efficient one-step method for synthesizing carbon-based nanofluids (CBNFs). The method employs the vortex trap method (VTM) and an oxygen-acetylene flame, serving as a carbon source, in a manufacturing system of the VTM (MSVTM). The flow rate ratio of O2 and C2H2 was adjusted to form suitable combustion conditions for the reduced flame. Four flow rate ratios of O2 and C2H2 were used: 1.5 : 2.5 (V1), 1.0 : 2.5 (V2), 0.5 : 2.5 (V3), and 0 : 2.5 (V4). The morphology, structure, particle size, stability, and basic physicochemical characteristics of the obtained carbon-based nanomaterials (CBNMs) and CBNFs were investigated using transmission electron microscopy, field-emission scanning electron microscopy, X-ray diffraction, Raman spectrometry, ultraviolet–visible–near-infrared spectrophotometry, and a particle size-zeta potential analyzer. The static positioning method was utilized to evaluate the stability of the CBNFs with added EP dispersants. The evaluation results revealed the morphologies, compositions, and concentrations of the CBNFs obtained using various process parameters, and the relation between processing time and production rate was determined. Among the CBNMs synthesized, those obtained using the V4-0 flow rate ratio had the highest stability when no EP dispersant was added. Moreover, the maximum enhancement ratios of the viscosity and thermal conductivity were also obtained for V4-0: 4.65% and 1.29%, respectively. Different types and concentrations of dispersants should be considered in future research to enhance the stability of CBNFs for further application.

THE CHARACTERISTICS OF ARTIFICIAL RICE WITH SEAWEED Eucheuma cottonii ADDITION AS A DIETARY FIBER SOURCE

2014 ◽  
Vol 6 (1) ◽  
Author(s):  
Natalia Prodiana Setiawati ◽  
Joko Santoso ◽  
Sri Purwaningsih
Keyword(s):  
Blood Glucose ◽  
Dietary Fiber ◽  
Dietary Fibre ◽  
Extrusion Process ◽  
The Body ◽  
Starch Digestibility ◽  
Food Commodities ◽  
The Stability ◽  
Extrusion Technology ◽  
Eucheuma Cottonii

The utilization of local food commodities such as corn and cassava with seaweed addition as a dietary fiber source for producing artificial rice through extrusion technology is an  alternative for food diversification. The research was carried out to find out the best composition (rice, corn, cassava, and seaweed) and temperature of extrusion process on making artificial rice and the influence of dietary fibre on sensory properties and physicochemical. The composition of rice, corn, and cassava in proportion  of 1:3:1 with 20% seaweed, Eucheuma cottonii, addition and temperature extruder of 90 °C were selected as the best product for artificial rice. The  sensory evaluation was 8.02±0.21 (people’s preference). In physicochemical properties, dietary fiber significantly affected on low bulk density and starch digestibility. This condition is very good for health especially in maintaining the stability of blood glucose in the body. Keywords: artificial rice, composition, extrusion, seaweed, dietary fibre, temperature

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