• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2002년도 학술대회지
• /
• pp.317-320
• /
• 2002

The effect of vibration on the viscosity of a shear-thinning fluid was investigated with a newly designed pressure-scanning capillary viscometer. The viscometer was designed to measure non-Newtonian viscosity continuously over a range of shear rates at a time. Low frequency vibration was applied perpendicularly to the direction of the flow. The effect of the transversal vibration was investigated for both Newtonian fluids and non-Newtonian fluids. The experimental results showed that the vibration had no effect on the viscosity of the Newtonian fluids. However, the vibration caused a significant reduction of the shear-thinning fluid viscosity. The viscosity reduction was strongly dependent on both vibration frequency and shear rate. In addition, the viscosity reduction was affected by the amplitude of vibration, and, the bigger amplitude applied, the more viscosity reduction occurred.

• 센서학회지
• /
• 제13권6호
• /
• pp.473-478
• /
• 2004

This study focused on the charateristic of magnetic fluids, the viscosity deviation of magnetic fluids due to temperature changes, and fabrication of a 'purely' liquid type microvalve. The viscosity of magnetic fluids decreases sharply during increasing of temperature. The viscosity of magnetic fluids is rated 1,000 cP at the room temperature and 25 cP when the temperature reaches $100^{\circ}C$. Briefly, it is remarkable that the fluid flow can be controlled by the temperature and this characteristic can be adopted to the microfluidics as a microvalve. The fabrication of a liquid type microvalve is more easy than solid state microvalves and which can increase an efficiency of the controlability with respect to the thermo-pneumatic micropump which is studied broadly for many years. When the magnetic fluid used as a sealant for high level sealing, the pressure leakage is less than solid state microvalve. The experimental results show that the pressure drop in microchannel, filled with the magnetic fluid, is significant in the temperature range of $20^{\circ}C{\sim}50^{\circ}C$ and this result explains why the use of magnetic fluids is possible as a microvalve searcher uses this characteristics. Well known thermo-pnumatic.

• 한국유체기계학회 논문집
• /
• 제7권2호
• /
• pp.21-26
• /
• 2004

In this study the effects of fluid viscosity on the pump performances for a conventional centrifugal pump were experimentally investigated. The study aimed to compare the pump characteristics between water and viscosity fluids. In order to measure the flow rate and pressure, v-notch welt and bourdon pressure gauges were used for the codes of KS B6301 and KS B6302. The working fluids were water, aqueous sugar and glycerin solutions. The results were summarized as follows : The experimental results were summarized as follows : the pump characteristics of the total head, shaft power, and efficiency with high viscosity fluids were different from those of water. When the viscosity of the applied fluid was increased, the total head and efficiency were more decreased than those of water. The decreasing gradients of the total head and the efficiency were larger than water due to the increased disk friction losses at the duty operation point. However, the shut-off head was almost constant regardless the viscosity of applied fluids. Each efficiency curves for the sugar $20w\%$ and glycerin $20w\%$ solutions was decreased up to $15.1\%$ and $34.4\%$ than that of water, respectively.

• 한국해양공학회:학술대회논문집
• /
• 한국해양공학회 2001년도 춘계학술대회 논문집
• /
• pp.196-201
• /
• 2001

Electro-Rheological(ER) fluids change their apparent viscosity according to the electric field strength. Therefore, there are many practical applications using the ER fluids. ER effect on the dispersive system of polarizable fine powder/dielectric oil has been investigated. The electrical and rheological properties of starch based ER fluid were reported. Yield stress of the fluids were measured on the couette cell type rheometer as a function of electric fields, particle concetrations, and temperatures. The electric field is applied by high voltage DC power supply, The outer cup is connected to positive electrode(+) and the bob becomes ground(-). And the temperatures the viscosity(or shear stress) versus shear rates were measured. In this experiment shear rates were increased from 0 to 200s$^{-1}$ in 2 minutes. This thesis presents Bingham properties of ER fluids subjected to temperature variations. The temperature dependence of the viscosity was determined for ER fluids consisting of 35 weight % starch particles in automatic transmission oil.

• 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.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 2002년도 춘계학술대회 논문집
• /
• pp.451-456
• /
• 2002

This paper describes the properties of Temperature-Viscosity characteristics of hydrous and anhydrous ER fluids containing starch and titanium particle in silicone oil. ER effects arise from electrostatic forces between the starch particles and titanium particles dispersed in the electrically insulating silicone oil induced when electric field is applied. ER fluids under electric field have been found to provide resonable estimates of ER fluid viscosity variation characteristics. Yield shear stress of the ER fluids were measured on the couette cell type rheometer as a function of electric fields. The outer cup is connected to positive electrode(+) and bob becomes ground(-). The electric field is applied by high voltage DC power supply. In this experiment shear rates were increased from 0 to 200/equation omitted/ in 2 minutes.

• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
• /
• pp.367-370
• /
• 2003

In this study the effects of fluid viscosity on the pump performances of a conventional centrifugal pump were experimentally studied. The study aimed to compare the pump characteristics for water and high viscosity fluids. The Working fluids are water, aqueous sugar solution and glycerin solution. The pump characteristics of total head and efficiency with high viscosity fluids were different. The performance curves of efficiency for the sugar and glycerin solutions were decreased up to 8.1% and 12.9% than that of water.

• 한국기계가공학회지
• /
• 제2권3호
• /
• pp.48-55
• /
• 2003

This study investigates the effect of temperature and electric field strength on the Bingham characteristics of Electro-Rheological(ER) fluids which change their Yield shear stress and viscosity by temperature and electric field strength. It is found that under constant temperature the Yield sheal stress and viscosity of ER fluids proportionally increase with the applied electric field strength, and under constant applied electric field strength the Yield shear stress and viscosity of ER fluids decrease with the increasing temperature. These results are considered to be applied to the fluid and pneumatic power industry.

• 대한기계학회논문집
• /
• 제14권1호
• /
• pp.241-250
• /
• 1990

본 연구에서는 낙구식 점도계를 이용하여 낮은 농도의 용액을 실험할 때 종말 속도측정의 어려움을 해결하기 위하여 레이저와 특수 타이머를 설치하였으며 정확한 특성시간을 결정하기 위하여 실린더 내부의 시험유체를 교란시키지 않고, 떨어뜨린 구 를 회수하는 장치를 제작하였다. 또한 주로 rheogoniometer에 의존하던 영 전단률 점성계수를 측정하기 위하여 속이 빈 알루미늄 구(hollow aluminium ball)의 밀도를 시험 유체와 거의 같은 정도까지 변화시켜가며 종말 속도를 측정하였으며 점탄성 유체 로써 Separan AP-273의 낮은 농도인 300에서 2000wppm까지의 저농도 용액에 대한 특성 시간을 여러모델에 의하여 실험적으로 결정하고 저농도 폴리머 용액에서 퇴화로 인한 점탄성유체의 특성 변화를 분석하였다.

• Journal of the korean society of oceanography
• /
• 제35권2호
• /
• pp.78-88
• /
• 2000

A weakly viscous wave and an approximate variational principle in viscous fluids are introduced, with which we can interpret the fundamentals such as how viscosity dissipation occurs with time elapse, and how the free surface boundary layer exists at the wavy surface in weakly viscous fluids. As an application, responses of a spherical buoy on the weakly viscous capillary gravity wave are investigated to show the viscosity effects. At the end, surfactant problems are briefly reviewed with the view of short viscous waves as expected future applications.