• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.8
• /
• pp.3611-3616
• /
• 2013

Physical characteristics of a magneto-rheological(MR) fluid can be influenced by a magnetic field. In the present study, the behaviors of MR fluid are visualized and the shear stresses are measured under the magnetic field for density 1.3, 1.5 and 1.7 $g/cm^3$, and viscosity 100, 1000 and 10000cp. When the magnetic field is applied, particles of MR fluid are arranged along lines of magnetic field. It is observed that the flow pattern of MR fluid under the magnetic field is different from that of MR fluid without the magnetic field. Shear stress of MR fluids under the magnetic field changes significantly. Shear stress by the magnetic field increases the shape of a quadratic equation. When the density changes from $1300kg/m^3$ to $1700kg/m^3$ at 2.0A, the shear stress increases about 33%.

• Proceedings of the Korean Society of Rheology Conference
• /
• 2000.05a
• /
• pp.66-69
• /
• 2000

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.37 no.10
• /
• pp.927-932
• /
• 2013

The intracranial aneurysm model is extracted based on the Computed Tomography (CT) scan images. Computational fluid dynamics simulations were conducted under both steady and realistic flow conditions in ANSYS-FLUENT. The minimum wall shear stress in the intracranial aneurysm tended to occur in the aneurysmal region. The magnitude of wall shear stress along inner wall of the curvature in the right M1 segment of middle cerebral artery is approximately 20 times higher than that along both the proximal and distal walls. However, the magnitudes of the wall shear stress at the aneurysm region were considerably low. The blood flow has the complex distribution in the aneurysmal region during the systolic period. Complex helical flow patterns are observed inside the aneurysm. Through an analysis of the hemodynamic characteristics, one may predict the rupture of the cerebral aneurysms.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1993.04b
• /
• pp.310-314
• /
• 1993

본 연구에서는 전기유동체의 전기장 부하 변화에따른 역학적특성을 고찰하였다. 유체에 가해지는 전기장은 0 .approx. 2.5 kV/mm 까지 변화시켰고, 외부에서 가해지는 회전력은 0 .approx. 500 rpm 까지의 범위로 하였으며, 용매의 종류를 달리하고 각각의 용매에 대한 중량비를 달리하여 자체 조성한 5종류의 전기유동유체에 대하여특성 고찰하였다. 각각의 전기유동유체는 부하되는 전기장에 대하여 전단력과 전단비의 관계가 선형적으로 증가하였고, 전기유동유체의 항복응력도 부하되는 전기장의함수로 증가함을 알 수 있었다. 또한 부하되는 전기장의 크기뿐만 아니라 입자의 중량비, 용매의 종류도 전기 유동유체의 역학적 특성에많은 영향을 미침을 알 수 있었다.

• Journal of the Korean Geotechnical Society
• /
• v.27 no.6
• /
• pp.49-61
• /
• 2011

This paper presents the applicability of rheological models for describing fine-laden debris flows and analyzes the flow characteristics as a function of grain size. Two types of soil samples were used: (1) clayey soils - Mediterranean Sea clays and (2) silty soils - iron ore tailings from Newfoundland, Canada. Clayey soil samples show a typical shear thinning behavior but silty soil samples exhibit the transition from shear thinning to the Bingham fluid as shear rate is increased. It may be due to the fact that the determination of yield stress and plastic viscosity is strongly dependent upon interstructrual interaction and strength evolution between soil particles. So grain size effect produces different flow curves. For modeling debris flows that are mainly composed of fine-grained sediments (<0.075 mm), we need the yield stress and plastic viscosity to mimic the flow patterns like shape of deposition, thickness, length of debris flow, and so on. These values correlate with the liquidity index. Thus one can estimate the debris flow mobility if one can measure the physical properties.

• Journal of Biomedical Engineering Research
• /
• v.23 no.4
• /
• pp.281-286
• /
• 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 the Korean Society of Marine Environment & Safety
• /
• v.12 no.1 s.24
• /
• pp.9-14
• /
• 2006

Analysis has been made of the anti-corrosive property of organic coating under the shear stress of the flow by means of AC impedance method. Marine anti-corrosive painted panels were placed in the water channel with varying flow rate, thereby experiencing varying flow shear stress on the surfaces. The velocities of the salt water were ranged from 1.48 to 5.2 m/s and the coating thickness of from $70{\mu}m\;to\;140{\mu}m$. For all coating thicknesses investigated, the poorer anti-corrosive property and the lower adhesion strength have been found for the higher shear stress. It has been found that the shear stress accelerates the aging of organic marine coatings.

• Journal of the Korean GEO-environmental Society
• /
• v.12 no.11
• /
• pp.65-70
• /
• 2011

It is well known all much information for evaluation on possibility of liquefaction and lateral flow for sand over the world. Recently, it is started to be known that liquefaction happens on non-plastic silt, too. But cyclic and post-cyclic characteristics for non-plastic silt is a few familiar to the world. Specially, it is not aware of the estimating method for lateral flow on non-plastic silt. The main purpose in this paper is to propose the evaluation for liquefaction and lateral flow on non-plastic silt. The method used in this research is that possibility for liquefaction on non-plastic silt was evaluated with cyclic direct simple shear test, and then residental strength was estimated with static shear test. Through the test results liquefaction on non-plastic silt is well not happened but strength decreases rapidly with increasing shear stress. With the proposed method it can be evaluated possibility of liquefaction and propose lateral flow.

• Journal of Advanced Marine Engineering and Technology
• /
• v.25 no.1
• /
• pp.131-138
• /
• 2001

In this paper, an experimental investigation of characteristics of developing turbulent steady flows in a square-sectional $180^{\circ}$curved duct is presented. The experimental study using air in a square-sectional $180^{\circ}$ curved duct carryed out to measure axials direction velocity and wall shear stress distrbutions by using Laser Dopper Velocimeter(LDV) system with data acquistion and processing the system of FIND6260 softwere at 7 sections from the inlet($\phi=0^{\circ}$) to the outlet($\phi=180^{\circ}$) in $301^{\circ}$ intervals of a curved duct.

• The Korean Journal of Rheology
• /
• v.10 no.1
• /
• pp.31-37
• /
• 1998

전기장이 인가되고 있는 유로를 유동하는 전기유변유체의 기본성질을 파악하기 위 한 실험 및 해석적 연구를 수행하여 빙햄유체로서의 유효성에 대해 알아보고 전기장과 유로 면 형상 및 진동유동으로 인한 영향에 대해 조사함으로써 ER밸브 및 ER대퍼로의 응용과 관련한 감쇄력 제어에 대해 검토하였다. 첫 번째 실험은 ER밸브의 높이가 2mm인 적극면이 평탄한것과 요철로 된 것을 사용하여 압력손실을 압력변환기로 측정함으로써 전기장 및 유 로형상에 대한 영향을 알아보았다. 압력손실 및 전단응력이 전기자세기와 함수관계를 가짐 을 알수 있었고 전기장세기와 유속의 변화시 손실계수에 의한 ER효과의 상이함이 확인되었 으며 레이놀즈수가 커지면 항복전단응력의 영향은 나타나지 않았다. 두 번째 실험은 실린더 를 정현파로 진동시켜 ER밸브에서 감쇠력제어가 가능한가를 알아보고 빙햄유체모델로 설계 된 ER댐퍼의 모델과 비교하였다. ER배르와 ER댐퍼의 수학적 모델을 시뮬레이션한 결과는 약간 벗어남이 보이기는 하나 실험결과와 일치하요 있다. 이것은 ER유체를 단순히 빙행유 체로 취급할수없으나 거시적으로는 빙햄유체로 취급할수 있음을 시사한다.