• International Journal of Automotive Technology
• /
• v.8 no.2
• /
• pp.165-177
• /
• 2007

Predictions of diesel particulate filtration are typically made by modeling of a particle collection, and providing particle trapping levels in terms of a pressure drop. In the present study, a series of single channel diesel particulate filter (DPF) experiments are conducted, the pressure traces are inversely analyzed and essential filtration parameters are deducted for model closure. A DPF filtration model is formulated with a non-linear description of soot cake regression. Dependence of soot cake porosity, packing density, permeability, and soot density in filter walls on convective-diffusive particle transportation is examined. Sensitivity analysis was conducted on model parameters, relevant to the mode of transition. Soot cake porosity and soot packing density show low degrees of dispersion with respect to the Peclet number and have asymptotes at 0.97 and $70\;kg/m^3$, respectively, at high Peclet number. Soot density in the filter wall, which is inversely proportional to filter wall Peclet number, controls the filtration mode transition but exerts no influence on termination pressure drop. The percolation constant greatly alters the extent of pressure drop, but is insensitive to volumetric flow rate or temperature of exhaust gas at fixed operation mode.

• Advances in nano research
• /
• v.14 no.3
• /
• pp.295-302
• /
• 2023

The characteristics of motile microorganism and three dimensional Darcy-Forchheimer nanofluid flow by a porous rotatable disk with heat generation/absorption is reported. Thermophoretic and Brownian motion aspects are included by utilizing Buongiorno model. Moreover, slip conditions are considered on velocity, thermal, concentration and microorganism. Shooting procedure is implemented to find the numerical results of physical quantities are evaluated parametrically. The different physical parameters like heat sink/source parameter, thermal, Brownian number, thermophoresis parameter, concentration, Peclet number, bioconvected Lewis number, microorganism on concentration and density of motile microorganism distributions is considered. Graphs of concentration and microorganism are plotted to examine the influence of distinct prominent flow parameters.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.29 no.5 s.236
• /
• pp.707-715
• /
• 2005

In this work, Scalar Passive code in Lattice Boltzmann Method is employed to simulate two-phase flow of low Reynolds number in a micro-channel. The mixing characteristics in a micro-channel is a function of Peclet number. The mixing length increases with the Peclet number. It is found that with the inclusion of static elements at the channel, rapid mixing of two liquids can be achieved, as shown by the results of computer simulations. The enhancement in mixing performance is thought to be caused by the generation of eddies and by lateral velocity component when the mixture flows past static elements. The results indicate that the size of static element has more effect on the mixing than the number of static element.

• Journal of the Korean Society of Safety
• /
• v.31 no.4
• /
• pp.143-149
• /
• 2016

In this study, a series of numerical simulation of dam break flow was conducted using EFDC model, and input conditions including cell size, time step, and turbulent eddy viscosity were considered to analyze parameter sensitivity. In case of coarse mesh layout, the propagated length of the shock wave front was ${\Delta}_x$ longer than that of other mesh layouts, and the velocity results showed jagged edge, which can be cured by applying fine grid mesh. Turbulent eddy viscosity influenced magnitude of the maximum velocity passing through gate up to 20% and the cell Peclet number less than 2.0 ensured no numerical oscillations.

• Polymer(Korea)
• /
• v.29 no.6
• /
• pp.549-556
• /
• 2005

Effects of the dimensionless variables on the heat transport phenomena in the extrusion process of a single screw extruder have been studied numerically. Based on the understanding of the solids conveying related to the geometrical structure and characteristics of the screw, the heat balance equation for the solids conveying zone was established and normalized. The finite volume method and power-law scheme were applied to derive a discretized equation and the equation was solved using the alternating direction iterative method with relaxation. Effects of the dimensionless parameters, Biot and Peclet numbers, that define the heat transfer characteristics of the solids conveying zone have been investigated with respect to the temperature of the feeding zone and the length of the solids conveying zone. As the Biot number is increased, the heat loss by cooling dominates to decrease the temperature of the barrel but it has little effects on the temperature of the solids bed and the length of the solids conveying zone. On the other hand, if the Peclet number is increased, the convection term dominates to decrease the temperature of the solids bed and it results in an increase in the length of the solids conveying zone.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2005.04a
• /
• pp.135-138
• /
• 2005

최근에 ELLAM 기법을 이용한 오염물 거동 문제를 많은 사람들이 다루어 오고 있다. ELLAM 기법은 기존의 Eulerian-Lagrangian 방식에서 일어나는 질량보존 문제점과 일반경계조건의 체계적인 적용 한계점을 극복하였다. 그러나 본 연구에서는 이 방식의 장단점을 네 개의 예제를 통하여 다른 모델들과 비교 검토하여 ELLAM의 수치적 고찰을 수행하고자 한다. 예제 수행 결과 Mesh Peclet Number가 무한대일때 ELLAM은 수치확산 및 수치진동과 같은 수치오차로 인해 음수의 농도 값을 갖거나 1 보다 큰 농도를 갖는 경향을 보인다. 그러나 Mesh Peclet Number 50 일때는 전체적으로 해석해와 잘 일치함을 볼 수 있다. 반면, LEZOOMPC(Lagrangian-Eulerian ZOOMing Peak and valley Capturing)는 항상 좋은 결과를 보여주고 있다. 따라서 위의 결과를 종합하여 볼 패 ELLAM의 단점은 LEZOOMPC의 성질을 이용하여 개선 및 보완될 수 있음을 간접적으로 시사해준다. 즉 LEZOOMPC에서 사용되는 선택적 국부 격자 세립화 과정을 이용하면 ELLAM에시 일어나는 다양한 수치오차를 줄일 수 있을 것이라고 판단된다.

• Korean Chemical Engineering Research
• /
• v.62 no.1
• /
• pp.112-117
• /
• 2024

Numerical simulations on the onset and the growth of viscous fingering during the miscible displacement due to the radial source flow were conducted. With introduction of a new stability criterion, the critical log-viscosity ratio, R_c, was found as a function of the Peclet number, Pe. Similar to the previous linear stability analyses, Pe made the system unstable, i.e., accelerated the onset of instability. For a large Pe system, the present numerical simulation yielded much stable results than the previous theoretical predictions This discrepancy was commonly encountered in the comparison between the theoretical prediction and the experimental finding. Additionally, the difference between the rectilinear system and the present one was also discussed. The present system was found more insensitive to the Peclet number than the rectilinear one.

• Journal of Mechanical Science and Technology
• /
• v.15 no.2
• /
• pp.268-276
• /
• 2001

In order to improve the efficiency of a direct contact heat exchanger for a solar thermal energy system, the working fluid should be dispersed into small and uniform droplets, and stay within a heat exchanger for a long time. Therefore, installation of meshes in a direct contact heat exchanger is suggested in the present study, and the performance of the direct contact heat exchanger with several layers of meshes is experimentally investigated. Diethyl phthalate is used as the working fluid, and the performance of the heat exchanger is tested for several different operating conditions and compared to that of the heat exchanger without meshes. The results of this investigation show that meshes make droplets uniform and small when the flow rate is low. The relationship between the Peclet number and the Nusselt number becomes linear if it is steady. And, the Nusselt number for the direct contact heat exchanger with meshes becomes greater than that without meshes as the Peclet number increases.

• Journal of computational fluids engineering
• /
• v.18 no.4
• /
• pp.61-68
• /
• 2013

Laser welding is widely used in the industry for the advantage of small heat affected zone and short weld process time. Conduction limit welding can be used to modify the surface characteristic and it is important to identify the heat affecting area correctly for the improvement of manufacturing accuracy. Since time and length scale associated with laser welding process are extremely small, numerical study can be a useful tool. In this study, two-dimensional axi-symmetric version of energy equation with enthalpy method has been used to analyze the effect of laser input conditions on final shape by the laser welding process. The proposed numerical procedure has been benchmarked with several experimental results and compared well. The modified Marangoni and Peclet number have been introduced using controllable input variables. Simple parametric researches have been performed for high Pr number material. The results show that higher Marangoni number increase fluid mixing, thus generating convex type weld pool. On the other hand, the width of the weld pool is proportional to Peclet number.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.25 no.7
• /
• pp.989-996
• /
• 2001

High-speed and low-speed flows are simulated numerically by flowfield-dependent mixed explicit-implicit (FDMEI) method. This algorithm depends on implicitness parameters of convection, diffusion, diffusion gradients, and source terms which are calculated from the changes of local Mach, Reynolds, Peclet, and Damkohler numbers between adjacent nodes. Convection phenomena or shock waves are resolved from Mach number-dependent implicitness parameters whereas diffusion or viscous actions are simulated by Reynolds number or Peclet number-dependent implicitness parameters. Fluctuation components of all variables are properly accommodated spatially and temporally in the FDMEI procedure. To illustrate, some benchmark example problems are presented for comparisons of the FDMEI results with other available data. These results appear to be encouraging and point toward the need for further investigations of the FDMEI theory.