• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.1
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• pp.9-16
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• 2014

This paper presents the theoretical analysis of a flow driven by surface tension and gravity in an inclined circular tube. A governing equation is developed for describing the displacement of a non-Newtonian fluid(Power-law model) that continuously flows into a circular tube owing to surface tension, which represents a second-order, nonlinear, non-homogeneous, and ordinary differential form. It was found that quantitatively, the theoretical predictions of the governing equation were in excellent agreement with the solutions of the equation for horizontal tubes and the past experimental data. In addition, the predictions compared very well with the results of the force balance equation for steady.

• Journal of Biomedical Engineering Research
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• v.23 no.4
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• pp.281-286
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• 2002

In this study, blood flow in a carotid artery supplying blood to the human's brain has been numerically simulated to find out how the blood flow affects the genesis and the growth of atherosclerosis and arterial thrombosis. Velocity Profiles and hemodynamic parameters have been investigated for the carotid arteries with three different stenoses under physiological flow condition. Blood has been treated as Newtonian and non-Newtonian fluid. To model the shear thinning properties of blood for non-Newtonian fluid, the Carreau-Yasuda model has been employed. The result shows that the wall shear stress(WSS) increases with the development of stenosis and that the wall shear stress in Newtonian fluid is highly evaluated compared with that in non-Newtonian Fluid. Oscillatory shear index has been employed to identify the time-averaged reattachment point and this point is located farther from the stenosis for Newtonian fluid than for non-Newtonian fluid The wall shear stress gradient(WSSG) along the wall has been estimated to be very high around the stenosis region when stenosis is developed much and the WSSG peak value of Newtonian fluid is higher than that of non-Newtonian fluid.

• Journal of Korea Multimedia Society
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• v.8 no.10
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• pp.1322-1328
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• 2005

The circulation flows passing through the Ekman boundary layer on the rotating disk and transfer the angular momentum into the interior region of the container. Consequently, the circulation enhances the momentum transfer and the interior fluid is divided by a propagating shear front. This investigation focuses on computer vision and image processing technique for analysis of Non-Newtonian Fluids. To visualize marching velocity shear front for the transient flow, a particular shaped particles and light are used. To validate the proposed method, quantitative image are compared with the optical data acquired by a direct measurement of LDV (Laser Doppler Velocimetry).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.545-550
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• 2017

When the systolic blood pressure is high, intermittent turbulence in blood flow appears in the aorta and carotid artery with stenosis during the systolic period. The turbulent blood flow is difficult to analyze using the Newtonian turbulence model due to the viscous characteristics of blood flow. As the shear rate is increased, the blood viscosity decreases by the viscoelastic properties of blood and a drag reduction phenomenon occurs in turbulent blood flow. Therefore, a new non-Newtonian turbulent model is required for viscoelastic fluid and hemodynamics. The main aims of this study were to develop a non-Newtonian turbulence model using the drag reduction phenomenon based on the standard $k-{\varepsilon}$ turbulent model for a general non-Newtonian fluid. This was validated with the experimental data and has a good tendency for non-Newtonian turbulent flow. In addition, the computation time and resources were lower than those of the low Reynolds number turbulent model. A modified turbulent model was used to analyze various turbulent blood flows.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.6
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• pp.751-759
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• 2007

We have developed several methods for the optimization problem having large-scale and highly nonlinear system. First, step by step method in optimization process was employed to improve the convergence. In addition, techniques of furnishing good initial guesses for analysis using sensitivity information acquired from optimization iteration, and of manipulating analysis/optimization convergency criterion motivated from simultaneous technique were used. We applied them to flow control problem and verified their efficiency and robustness. However, they are based on quasi-Newton method that approximate the Hessian matrix using exact first derivatives. However solution of the Navier-Stokes equations are very cost, so we want to improve the efficiency of the optimization algorithm as much as possible. Thus we develop a true Newton method that uses exact Hessian matrix. And we apply that to the three-dimensional problem of flow around a sphere. This problem is certainly intractable with existing methods for optimal flow control. However, we can attack such problems with the methods that we developed previously and true Newton method.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.57-62
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• 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.

• The Korean Journal of Rheology
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• v.8 no.1
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• pp.1-10
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• 1996

본 논문에서는 협착이 발생된 원관내 뉴턴유체와 비뉴턴유체의 정상 및 맥동유동특 서을 유한요소법으로 해석하였다. 본연구는 맥동유동특성에서 협착관 형상의 변화, 협착이 주기적으로 발생된 협착관에서 협착부사이의 거리와 협착부의 수가유동특성에 미치는 영향 을 검토하였다. 레이놀즈수가 일정할 때 협착이 발생된 원형관내 뉴턴유체와 비뉴턴유체의 맥동유동특성은 정상유동의 경우와 크게 다르게 나타난다. 맥동유동에서는 정상유동보다 관 중앙부에서 속도분포가 훨씬 평탄하고 맥동유동의 속도분포는 감속시에 비하여 가속시에 관 중앙부의 속도분포가 더 평탄하게 나타난다. 정상유동과 맥동유동으 감속시에서는 협착부 하류의 벽면에서 재순환영역이 발생된다. 협착부의 수가 증가하면 각 협착부 주위의 속도장 은 유사하게 나타나지만 전체 압력손실은 크게 증가한다. 협착부사이의 거리가 변화될 경우 맥동유동속도의 국소최대치와 국소최소치의 차이가 가속시에는 거의 없지만 감속시에는 협 착부사이의 거리에 따라 다르게 나타난다.

• Proceeding of EDISON Challenge
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• 2013.04a
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• pp.403-408
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• 2013

본 논문은 EDISON_CFD를 이용하여 관상동맥 분지관에서 점도에 따른 유체의 유동현상에 관하여 연구를 하였다. 뉴턴유체인 물의 점성계수 일때와 비뉴턴유체인 혈액의 Carreau model에서의 영전단율 점성계수(${\eta}_0$)와 무한전단율 점성계수(${\eta}_{\infty}$)일 때의 유동현상을 살펴보았다. 그 결과 점도가 증가할수록 재순환 영역에서 유체의 속도가 감소하였고 CF 및 CP값이 감소하는 구간의 수가 증가하여 벽면의 저전단응력으로 인해 생기는 재순환영역의 수가 증가하는 것으로 나타났다.

• The KSFM Journal of Fluid Machinery
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• v.17 no.6
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• pp.29-37
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• 2014

Non-Newtonian fluid mechanics takes charge of an important role in the oil industries. Especially in the oil well drilling process, the drilling fluid such as mud keeps the drill bit cool and clean during drilling, with suspending drill cuttings and lubricating a drill bit. The purpose of this study is to examine the effect of fluid mud rheological properties to predict different characteristics of non-Newtonian fluid in the mud mixing tank on offshore drilling platforms. In this paper, ANSYS fluent package was used for the simulation to solve the hydrodynamic force and to evaluate mud mixing time. Prediction of the power consumption and the pumping effectiveness has been presented with different operating fluid models as Newtonian and non-Newtonian fluid. The comparison between Newtonain mud model and non-Newtonian mud model is confirmed by the CFD simulation method of drilling mud mixing tank. The results present useful information for the design of the drilling mud mixing tanks and provide some guidance on the use of CFD tool for such non-Newtonian fluid flow.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.385-388
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• 2008

The objective of this paper is simulating blood flow through the branched and stenotic tube numerically. SC-Tetra, which is one of the commercial code using FVM method, was utilized for this analysis. The flow is assumed as an incompressible laminar flow with the additional condition of non-Newtonian fluid. As the constitutive equation for the fluid viscosity, the following models were solved with governing equations ; Cross Model, Modified Cross Model, Carreau Model and Carreau-Yasuda Model. Final goal was achieved to get analytic data about shear stress, at specific points, changing the geometry with various factors like the bifurcation angle, diameter of the branches, the ratio of stenosis, and etc. The material property of blood was referred from the related papers. Furthermore, to verify results they were compared with those of the published papers. There were some discrepancies based on the different solver and the different data post-processing method. However, many parameters like the location of low shear stress, which arised from bifurcation or stenosis, and the tendency of various factors were found to be very similar.