• Journal of Korean Neurosurgical Society
• /
• 제62권2호
• /
• pp.183-192
• /
• 2019

Objective : The objective of this study was to analyze patient-specific blood flow in ruptured aneurysms using obtained non-Newtonian viscosity and to observe associated hemodynamic features and morphological effects. Methods : Five patients with acute subarachnoid hemorrhage caused by ruptured posterior communicating artery aneurysms were included in the study. Patients' blood samples were measured immediately after enrollment. Computational fluid dynamics (CFD) was conducted to evaluate viscosity distributions and wall shear stress (WSS) distributions using a patient-specific geometric model and shear-thinning viscosity properties. Results : Substantial viscosity change was found at the dome of the aneurysms studied when applying non-Newtonian blood viscosity measured at peak-systole and end-diastole. The maximal WSS of the non-Newtonian model on an aneurysm at peak-systole was approximately 16% lower compared to Newtonian fluid, and most of the hemodynamic features of Newtonian flow at the aneurysms were higher, except for minimal WSS value. However, the differences between the Newtonian and non-Newtonian flow were not statistically significant. Rupture point of an aneurysm showed low WSS regardless of Newtonian or non-Newtonian CFD analyses. Conclusion : By using measured non-Newtonian viscosity and geometry on patient-specific CFD analysis, morphologic differences in hemodynamic features, such as changes in whole blood viscosity and WSS, were observed. Therefore, measured non-Newtonian viscosity might be possibly useful to obtain patient-specific hemodynamic and morphologic result.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 추계학술대회
• /
• pp.1634-1639
• /
• 2004

The present study concerns a experimental study of fully developed laminar flow of a Newtonian and non-Newtonian fluid through a concentric annulus with a combined bulk axial flow and inner cylinder rotation for the various radius ratio. This study shows the fundamental difference between Newtonian and non-Newtonian fluid flow in an annulus for various radius ratio.

• 설비공학논문집
• /
• 제4권4호
• /
• pp.342-350
• /
• 1992

An experimental investigation of the stenosis effects on the pressure drop and flow change in the internal flow is presented. Stainless steel tubes of small diameter(3.175mm, 3.4mm) are used for the test section of the flow loop. Percent contraction ranges from 35% to 83% and the stenosis length ratio (L/d) is varied from 2.8 to 8. Water and aqueous glycerol solutions are used for Newtonian fluids and polymer solutions of Separan AP-273 (500 wppm, 1000 wppm) for non-Newtonian fluids. Pressure loss coefficients of non-Newtonian fluids decrease just as those of Newtonian fluids. The loss coefficients of Newtonian and non-Newtonian fluids increase as the percent contraction increases and the loss coefficients of non-Newtonian fluids are larger than those of Newtonian fluids for the same stenosed tube. The loss coefficient increases as the stenosis length ratio increases.

• Korean Chemical Engineering Research
• /
• 제49권3호
• /
• pp.314-319
• /
• 2011

본 연구에서는 전산유체모사기인 Fluent를 활용하여 slot 다이 내부에서 Newtonian과 non-Newtonian 코팅액의 동적 거동을 고찰함으로써 최적 다이 설계를 위한 방법론을 구축하고자 하였다. 다이 출구에서 코팅액의 속도분포를 일정하게 하기 위해 chamber 구조를 변화시킴으로써 최적 하이브리드 다이의 설계가 가능하였다. 특히, non-Newtonian 유체의 경우, 전단담화 정도와 chamber의 coat-hanger 최적 길이의 상관관계를 도출하였다.

• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
• /
• pp.57-62
• /
• 2004

In the current study the effects on pump performances of a conventional centrifugal pump for Newtonian and non-Newtonian fluid were experimentally studied. The study aimed to compare the pump characteristics for Newtonian and non-Newtonian fluid. The working fluids are water, aqueous sugar solution, glycerin solution, muddy solution and pulp solution. The pump characteristics with high viscosity fluids were different. The operating efficiency for the sugar and glycerin solutions were decreased to $8.1\%$ and $12.9\%$ than that of water. The head reductions of the muddy solution for different concentration ratios were decreased to $7.97\%,\;15.11\%$ and $24.87\%$ than that of water And the head reductions of the pulp solution for different concentration ratios were decreased to $11.87\%,\;19.79\%$ md $36.81\%$ than that of water.

• 대한기계학회논문집B
• /
• 제20권5호
• /
• pp.1603-1612
• /
• 1996

The pressure loss coefficient of Newtonian and non-Newtonian fluids such as water, aqueous solutions of Carbopol-934 and Separan AP-273 and blood in the stenotic tubes are determined experimentally and numerically. The numerical analyses for flows of non-Newtonian fluids in the stenotic tubes are conducted by the finite element method. The effect of the contraction ratio and the ratio of length to diameter on the pressure drop are investigated by the experiments and numerical analysis. The pressure loss coefficients are significantly dependent upon the Reynolds number in the laminar flow regime. As Reynolds number increases, the pressure loss coefficients of both Newtonian and non-Newtonian fluids decrease in the laminar flow regime. As the ratio of length to diameter increases the maximum pressure loss coefficient increases in the laminar flow regime for both Newtonian and non-Newtonian fluids. Newtonian fuid shows the highest values of pressure loss coefficient and blood the next, followed by Carbopol solution and Separan solution in order. Experimental results are used to verify the numerical analyses for flows of Newtonian and non-Newtonian fluids. Numerical results for the maximum pressure loss coefficient in the stenotic tubes are in fairly good agreement with the experimental results. The relative differences between the numerical and experimental results of the pressure loss coefficients in the laminar flow regime range from 0.5% to 14.8%.

• Journal of Mechanical Science and Technology
• /
• 제16권2호
• /
• pp.255-261
• /
• 2002

A newly designed mass-detecting capillary viscometer uses a novel concept to continuously measure non-Newtonian fluids viscosity over a range of shear rates. A single measurement of liquid-mass variation with time replaces the now rate and pressure drop measurements that are usually required by capillary tube viscometers. Using a load cell and a capillary, we measured change in the mass flow rate through a capillary tube with respect to the time, m(t), from which viscosity and shear rate were mathematically calculated. For aqueous polymer solutions, excellent agreement was found between the results from the mass-detecting capillary viscometer and those from a commercially available rotating viscometer. This new method overcomes the drawbacks of conventional capillary viscometers meassuring non-Newtonian fluid viscosity. First, the mass-detecting capillary viscometer can accurately and consistently measure non -Newtonian viscosity over a wide range of shear rate extending as low as 1 s$\^$-1/. Second, this design provides simplicity (i. e., ease of operation, no moving parts), and low cost.

• 설비공학논문집
• /
• 제6권3호
• /
• pp.227-236
• /
• 1994

Steady flows of Newtonian and non-Newtonian fluids in the stenotic tubes with various stenotic shapes are numerically simulated. Validity of the modified power-law model as a constitutive equation for the purely viscous non-Newtonian fluid is discussed and the results of the power-law model are compared with those of the Carreau model, the Powell-Eyring model and experimental data for blood. Flow characteristics and reattachment lengths for non-Newtonian fluids in the stenotic tubes are presented extensively. Also, the analysis is extended to predict the influences of diameter ratio, stenosis spacing, number of stenosis and Reynolds number on the flow characteristics in the multiple stenotic tubes.

• Korea-Australia Rheology Journal
• /
• 제18권3호
• /
• pp.161-167
• /
• 2006

This study presents results on the numerical simulation of Newtonian and non-Newtonian flow in a channel obstructed by an asymmetric array of obstacles for clarifying the descriptive ability of current non-Newtonian constitutive equations. Jones and Walters (1989) have performed the corresponding experiment that clearly demonstrates the characteristic difference among the flow patterns of the various liquids. In order to appropriately account for flow properties, the Navier-Stokes, the Carreau viscous and the Leonov equations are employed for Newtonian, shear thinning and extension hardening liquids, respectively. Making use of the tensor-logarithmic formulation of the Leonov model in the computational scheme, we have obtained stable solutions up to relatively high Deborah numbers. The peculiar characteristics of the non-Newtonian liquids such as shear thinning and extension hardening seem to be properly illustrated by the flow modeling. In our opinion, the results show the possibility of current constitutive modeling to appropriately describe non-Newtonian flow phenomena at least qualitatively, even though the model parameters specified for the current computation do not precisely represent material characteristics.

• 대한의용생체공학회:의공학회지
• /
• 제23권4호
• /
• pp.281-286
• /
• 2002

심혈관계에서 자주 발생하는 죽상경화증과 혈전의 발생 및 성장에 관한 복잡한 기전을 이해하기 위하여 뇌의 혈액공급을 담당하는 경동맥을 2차원 축대칭으로 모사하여 수치해석하였다. 박동유동 상태에서 경동맥 내에 25%. 50%, 75%의 협착이 형성된 경우에 대하여 혈관내의 속도분포 및 혈류역학적 벽 파라미터들이 고찰되었다. 혈액은 뉴턴유체 및 전단변형률에 따라 점성이 변화하는 비뉴턴유체로 간주되었으며 비뉴턴모델로는 혈액과 유사한 점성치를 나타내는 Carraeu-Yasuda 모델이 적용되었다. 해석 결과 혈관내벽에 작용하는 벽전단응력은 협착이 커질수록 크게 증가하였으며 비뉴턴유체보다 뉴턴유체의 경우에서 벽전단응력이 크게 평가되었다. 벽전단응력 진동지표(OSI)에 의해 시간평균 재부착점이 예측되었는데 비뉴턴유체보다 뉴턴유체의 경우에서 협착 영역으로부터 멀리 떨어진 곳에서 관찰되었다. 시간평균 벽전단응력구배(WSSG)도 협착이 큰 경우에 상당히 크게 나타났는데 비뉴턴유체보다 뉴턴 유체의 경우에 더 큰 값이 나타났다.