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미세입자분산 액적의 고체면에서 모세퍼짐 현상에 관한 직접수치해석 기법개발
황욱렬(Wook Ryol Hwang),정현준(Hyun Jun Jeong),김시조(See Jo Kim),김종엽(Chongyoup Kim) 한국전산유체공학회 2007 한국전산유체공학회지 Vol.12 No.4
We present a direct numerical simulation technique and some preliminary results of the capillary spreading of a droplet containing particles on the solid substrate. We used the level-set method with the continuous surface stress for description of droplet spreading with interfacial tension and employed the discontinuous Galerkin method for the stabilization of the interface advection equation. The distributed Lagrangian-multipliers method has been combined for the implicit treatment of rigid particles. We investigated the droplet spreading by the capillary force and discussed effects of the presence of particles on the spreading behavior. It has been observed that a particulate drop spreads less than the pure liquid drop. The amount of spread of a particulate drop has been found smaller than that of the liquid with effectively the same viscosity as the particulate drop.
김시조(See Jo Kim),황욱렬(Wook Ryol Hwang),임경훈(Kyung Hun Lim) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.10
Screw extrusion processings are being used in many cases for blending or compounding in order to produce uniform mixtures of more than two different materials. As far as mixing in a single-phase flow is concerned in the single-screw extrusion process a striation thickness can be considered as a mixing measure. In the two-phase immiscible mixing system, however, due to combination of shear rate and interfacial tension on the drop interface, drops easily tend to be in the status of large elongation and eventually breakup under the repetition of the flow with high shear near the barrel surface and low shear near the screw walls. Recently, deformation and breakup mechanism of an immiscible drop were investigated experimentally in a screw channel flow, which mimics the flow in the metering section of section of the single-screw extruder. They presented the flow visualization results of drop deformation patterns and observed the peculiar thread deformation of drop as the comet-like thread. In our research, the numerical simulations by using the commercial software were carried out to understand the drop deformation and breakup mechanism and compared with the experimental results.
이현도(Hyun Do Lee),황욱렬(Wook Ryol Hwang) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.5-3
Considering that chaos is the only way to enhance mixing performance for such a high viscous fluid, we propose mechanically simple but highly effective designs for the mixing tank, which enables periodic reorientation of material elements by the stream surface crossing mechanism [1-3]. For a specific case of four paddled impeller as an example, we introduce a theoretical dynamical systems modeling that predicts existence of dominant homoclinic tangling and small regions governed by usual near-integrable structures (resonance bands and KAM tori). And prototypical flow will be presented by using of a disk impeller for experimental observation and computational inspection of geometrical and dynamical effects. In addition, general aspects of chaotic transports in industrial mixing vessels will be discussed. The experimental flow visualization results will be presented that verify the presence of the dynamical systems structures. The quantitative evaluation of the mixing performance through measurement of unmixed zones (resonance bands and KAM tori) by means of image processing techniques will be processing techniques will be presented. Especially numerical simulation results will be presented that the dynamical systems structures through the Poincare section and quantitative evaluation of the mixing performance by Liapunov exponents for disk impeller case.
이동현(Dong Hyun Lee),황욱렬(Wook Ryol Hwang) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.5-3
We will discuss a method to increase the mixing efficiency of highly viscous fluid materials in industrial mixing vessels. This research uses a propeller impeller. Experiments with fluorescent dyes and a laser will be presented along with dynamical fluid structures and the use of simulation to help understand the dynamical structure. Using a propeller type impeller, we found the flow pattern of RPM change. Using baffle and pin, we increased mixing performance and the use of propeller types of impeller for observing flow pattern of newtonian fluids.