• 대한의용생체공학회:의공학회지
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• 제27권3호
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• pp.94-100
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• 2006

The effectiveness of the treatment of intracranial aneurysms with endovascular coiling depends on coil packing density, the location of aneurysm, its neck dimensions with respect to the aneurysm dome, and its size with respect to the surrounding tissue. Clinical data also suggests that the aneurysm neck size is the main predictor of aneurysm recanalization. In this study, the force impinging on the aneurysm neck in an idealized aneurysm was calculated by using a three dimensional finite volume method for the non-Newtonian incompressible laminar flow. To quantify the effect of neck size on the impingement force, calculations were performed for aneurysm neck diameters (Da) varying from 10% to 100% of the parent artery diameter (Dp). Also, maximum impingement forces were represented by a function of the ratio of the aneurysm neck to the diameter of the parent vessel. The results show that the hemodynamic forces exerted on the coil mass at the aneurysm neck due to the pulsatile blood flow are larger for wide necked aneurysms.

• Smart Structures and Systems
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• 제2권1호
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• pp.61-80
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• 2006

The concept of structural vibration control is to absorb vibration energy of the structure by introducing auxiliary devices. Various types of structural vibration control theories and devices have been recently developed and introduced into mechanical systems. One of such devices is damper employing controllable fluids such as ElectroRheological (ER) or MagnetoRheological (MR) fluids. MagnetoRheological (MR) materials are suspensions of fine magnetizable ferromagnetic particles in a non-magnetic medium exhibiting controllable rheological behaviour in the presence of an applied magnetic field. This paper presents the modelling of an MRfluid damper. The damper model is developed based on Newtonian shear flow and Bingham plastic shear flow models. The geometric parameters are varied to get the optimised damper characteristics. The numerical analysis is carried out to estimate the damping coefficient and damping force. The analytical results are compared with the experimental results. The results confirm that MR damper is one of the most promising new semi-active devices for structural vibration control.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제16권3호
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• pp.181-192
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• 2012

Here in this paper, the steady paint film flow on a vertical wall of a non-Newtonian pseudo plastic fluid for drainage problem has been investigated. The exact solution of the nonlinear problem is obtained for the velocity profile. Also the average velocity, volume flux, shear stress on the wall, force to hold the wall in position and normal stress difference have been derived. We retrieve Newtonian case, when material constant ${\mu}_1$ and relaxation time ${\lambda}_1$ equal zero. The results for co-rotational Maxwell fluid is also obtained by taking material constant ${\mu}_1$ = 0. The effect of the zero shear viscosity ${\eta}_0$, the material constant ${\mu}_1$, the relaxation time ${\lambda}_1$ and gravitational force on the velocity profile for drainage problem are discussed and plotted.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1987-1992
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• 2004

Hemodynamics behavior of the blood flow is influenced by the presence of the arterial stenosis. If stenosis is present in an artery, normal blood flow is disturbed. In the present study, characteristics of steady and pulsatile flow of non-Newtonian fluid, the effects of stenosised geometry are analyzed by numerical simulation. One interesting point is that non-symmetric solutions were obtained at severity stenosis, although the stenosis and the boundary condition were all axisymmetric.

• 한국전산유체공학회지
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• 제19권4호
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• pp.61-67
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• 2014

Since the most of the existing non-Newtonian models are not adequate to apply to the lattmce Boltzmann method, it is a challenging task from both the theoretical and the numerical points of view. In this research the hydro-kinetic model was modified and applied to the 3-D moving sphere in the circular channel flow and the characteristics of the shear thinning effect by the HK-model was evaluated and the condition of ${\Gamma}$ in the model was suggested for the stable simulation to generate non-trivial prediction in three dimension strong shear flows. On the wall boundaries of circular channel the curved wall surface treatment with constant velocity condition was applied and the bounceback condition was applied on the sphere wall to simulate the relative motion of the sphere. The condition is adequate at the less blockage than 0.7 but It may need to apply a multi-scale concept of grid refinement at the narrow flow region. to obtain the stable numerical results.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1999년도 춘계 학술대회논문집
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• pp.192-198
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• 1999

The present study proposes modified temperature-dependent non-Newtonian viscosity model and investigates flow characters and heat transfer enhancement of the viscoelastic non-Newtonian fluid in a 2:1 rectangular duct. The proposed modified temperature dependent viscosity model has non-zero value near the high temperature and high shear rate region while on the existing viscosity models have zero value. Two versions of thermal boundary conditions involving difference combination of heated walls and adiabatic walls are analyzed in this study. The combined effect of temperature dependent viscosity, buoyancy, and secondary flow caused by second normal stress difference are ail considered. The Reiner-Rivlin model is adopted as a viscoelastic fluid model to simulate the secondary flow caused by second normal stress difference. Calculated Nusselt numbers by the modified temperature-dependent viscosity model gives under prediction than the existing temperature-dependent viscosity model in the regions of thermally developed with same secondary normal stress difference coefficients with experimental results in the regions of thermally developed. The heat transfer enhancement of the viscoelastic fluid in a 2:1 rectangular duct is highly dependent on the secondary flow caused by the magnitude of second normal stress difference.

• 한국유변학회:학술대회논문집
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• 한국유변학회 2002년도 추계학술발표회 논문집
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• pp.63-66
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• 2002

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.324-329
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• 2001

This experimental study concerns the characteristics of a transitional flow in a concentric annulus with a diameter ratio of 0.52, whose outer cylinder is stationary and inner one rotating. The pressure losses and skin-friction coefficients have been measured for the fully developed flow of $0.1\sim0.4%$ aqueous solution of sodium carbomethyl cellulose (CMC), respectively at inner cylinder rotational speed of $0\sim600rpm$. The transitional flow has been examined by the measurement of pressure losses to reveal the relation of the Reynolds and Rossby numbers with the skin-friction coefficients. The present results show that the skin-friction coefficients have the significant relation with the Rossby numbers, only for laminar regime. The occurrence of transition has been checked by the gradient changes of pressure losses and skin-friction coefficients with respect to the Reynolds numbers. The increasing rate of skin-friction coefficients due to the rotation in uniform for laminar flow regime, whereas it is suddenly reduced for transitional flow regime and, then, is gradually declined for turbulent flow regime. Consequently, the critical(axial-flow) Reynolds number decrease as the rotational speed increases. Thus, the rotation of inner cylinder promotes the early occurrence of transition due to the onset of taylor vortices.

• 멤브레인
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• 제7권3호
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• pp.142-149
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• 1997

비대칭형 막기공을 통한 뉴톤 유체의 발산흐름(diverging flow)에 대한 심도있는 해석 결과를 제시하였다. 막기공 모델의 일반적 형태인 슬릿(slit)과 원뿔(cone)형 채널에 대해 미동흐름(creeping flow)을 적용하여 유속분포 관계식을 구하였다. 유속분포의 고찰로부터 발산각도 $\alpha$$\longrightarrow$0 인 경우는 윤활근사법(lubrication approximation)이 적용되어 Poiseuille 흐름으로 되는 것을 확인하였고, 발산각도가 증가할수록 벽면부근에서의 유속분포는 결핍(depletion)됨과 아울러 전체유속은 감소하였다. 구해진 속도분포와 압력분포의 관계식으로부터 투과유량에 대한 이론식을 도출하였다. 예측된 결과는 기공의 비대칭성이 증가할수록 그에 따른 투과유량은 점차 증가하는 거동을 보였다. 본 연구의 이론결과는 궁극적으로 막여과에의 응용 측면과 밀접하게 연관되어 있다.

• 한국수산과학회지
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• 제29권1호
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• pp.92-96
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• 1996

CM-chitin의 고유특성 및 유동특성을 밝혀 효과적으로 식품산업에 이용하기 위하여 CM-chitin 수용액의 유동특성 중 임계농도와 유동방정식을 조사하였다. 물에서 CM-chitin의 환원농도는 2.5이었으며, 이 때의 임계농도는 $0.8\%(w/v)$이었다. 즉 $0.8\%$ 이하의 농도에서는 분자사슬간 상호작용이 일어나지 않았으며, $0.8\%$ 이상에서 상호작용이 일어나는 것으로 나타났다. $0.5\%$ CM-chitin 용액은 전단속도가 증가하여도 점도는 일정하게 유지되는 뉴우튼 유체의 특성을 보였으며, $1.0\%$ 용액은 전단속도가 증가하면 점도가 낮아지는 의가소성 유체의 특성을 보였다. $3.0\%$ CM-chitin 수용액의 유동상수 $\eta_\infty,\;\eta_0,\;\beta$, n은 각각 $0.0908(\fallingdotseq0.1)cp$, 770cp, 0.81, 0.36이었다. 따라서 $3.0\%$ CM-chitin 수용액의 유동방정식은 $\eta=0.1+\{{770/(1+0.81D^{0.36})\}$으로 나타낼 수 있다.