The charge-carriers of the organic layers are one of the dominant factors to influence the performance of OLEDs. Thus, it is very important to study and understand the charge transporting behaviors in the organic layers of OLED. However, the organic materials show usually to have very high resistivity and very low carrier mobility, and then using general modeling techniques suitable for common semiconductors cannot conveniently simulate that. First, a transporting model of the bilayer organic OLED are proposed in this dissertation, in which model were based on the current-voltage characteristics simulation proposed by Lampert and the continuous equation of current transport. The model contains a description of ohmic contacts, thermal emission and tunneling injection, space charge effects, trap effect, field dependent mobility and recombination processes. In addition, the method of Monte Carlo is a computational technique by using random numbers to compute an approximation to something whose exact value is difficult or impossible to compute, and that is used to simulate the bilayer organic OLED. In this study, a numerical model proposed is successfully applied to describe the characteristics of the bilayer organic light-emitting diode. The model is satisfyingly demonstrated not only for applying to simulate several bilayer devices (1-Naphdata/Alq3¡BTPD/Alq3) reported but also for some devices obtained in our results. Finally, it can be extended to optimize the analysis and fabrication of bilayer devices.

A FORTRAN code was developed to numerically simulate the mixed convective flow over a three-dimensional horizontal backward-facing step. The momentum and energy equations under the assumption of the Boussinesq approximation were discretized by means of a finite volume technique. The SIMPLE algorithm scheme was applied to link the pressure and velocity fields inside the domain while an OpenMP parallel implementation was proposed to improve the numerical performance and to accelerate the numerical solution. The heating process corresponds to a channel heated from below at constant temperature keeping insulated all the other channel walls. In addition, the back-step was considered as a thermally conducting block and its influence in the heating process was explored by holding different solid to fluid thermal conductivity ratios. The effects over the velocity and temperature distribution of buoyancy forces, acting perpendicular to the mainstream flow, are studied for three different Richardson numbers Ri=3, 2, and 1 and the results are compared against those of pure forced convection Ri=0. In these simulations the Reynolds number is fixed at 200 while the bottom wall temperature is adjusted to fulfill the conditions for the different Ri. Under this assumption, as Ri increases the buoyancy effects are the dominant effects in the mixed convective process. The numerical results indicate that the velocity field and the temperature distribution for pure forced convection are highly distorted if compared with the mixed convective flow. If the Ri parameter is increased, then the primary re-circulation zone is reduced. Similarly, as the buoyancy forces become predominant in the flow, the convective rolls, in the form of spiral-flow structures, become curlier and then higher velocity components are found inside the domain. The temperature field distribution showed that as the Ri is increased a thicker layer of high temperature flow is located at the channel??s top wall as a result of the higher rates of low-density flow moving to the top wall. The flow is ascending by the channel sidewalls, while descending by the channel span-wise central plane. The parallel numerical strategy is presented and some results for the performance of the OpenMP implementation are included. In this sense, linear speedup was obtained when using 16 possessors in parallel.

In this work, numerical simulations of flow separation control are performed. The sep-aration control technique studied is called 'synthetic jet actuation'. The developed code employs a cell centered finite volume scheme which handles viscous, steady and unsteady compressible turbulent flows. The pulsating zero mass jet flow is simulated by imposing a harmonically varying transpiration boundary condition on the airfoil's surface. Turbulence is modeled with the algebraic model of Baldwin and Lomax. The application of synthetic jet actuators is based in their ability to energize the boundary layer, thereby providing signifcant increase in the lift coefficient. This has been corroborated experimentally and it is corroborated numerically in this research. The performed numerical simulation investigates the flow over a NACA0015 air-foil. For this flow Re = 9??105 and the reduced frequency and momentum coefficient are F+ = 1:1 and C?? = 0:04 respectively. The oscillatory injection takes place at 12.27% chord from the leading edge. A maximum increase in the mean lift coefficient of 93% is predicted by the code. A discrepancy of approximately 10% is observed with corresponding experimental data from the literature. The general trend is, how-ever, well captured. The discrepancy is attributed to the modeling of the injection boundary condition and to the turbulence model.A sensitivity analysis of the lift coefficient to different values of the oscillation parameters is performed. It is concluded that tangential injection, F + ?? O(1) and the utilized grid resolution around the site of injection are optimal. Streamline fields ob-tained for different angles of injection are analyzed. Flow separation and attachment as functions of the injection angle and of the velocity of injection can be observed. It is finally concluded that a reliable numerical tool has been developed which can be utilized as a support tool in the optimization of the synthetic jet operation and in the modeling of its operation.

A computational study of three-dimensional turbulent flow and heat transfer was performed in four types of rotating channels. The first type is a rotating rectangular channel with V-shaped ribs. The channel aspect ratio (AR) is 4:1, the rib height-to-hydraulic diameter ratio (e/Dh) is 0.078 and the rib pitch-to-height ratio (P/e) is 10. The rotation number and inlet coolant-to-wall density ratio were varied from 0.0 to 0.28 and from 0.122 to 0.40, respectively, while the Reynolds number was varied from 10,000 to 500,000. Three channel orientations (90 degrees, -135 degrees, and 135 degrees from the rotation direction) were also investigated. The second type is a rotating rectangular channel with staggered arrays of pinfins. The channel aspect ratio (AR) is 4:1, the pin length-to-diameter ratio is 2.0, and the pin spacing-to-diameter ratio is 2.0 in both the stream-wise and span-wise directions. The rotation number and inlet coolant-to-wall density ratio varied from 0.0 to 0.28 and from 0.122 to 0.20, respectively, while the Reynolds number varied from 10,000 to 100,000. For the rotating cases, the rectangular channel was oriented at 150 degrees with respect to the plane of rotation. In the rotating two-pass rectangular channel with 45-degree rib turbulators, three channels with different aspect ratios (AR=1:1; AR=1:2; AR=1:4) were investigated. Detailed predictions of mean velocity, mean temperature, and Nusselt number for two Reynolds numbers (Re=10,000 and Re=100,000) were carried out. The rib height is fixed as constant and the rib-pitch-to-height ratio (P/e) is 10, but the rib height-to-hydraulic diameter ratios (e/Dh) are 0.125, 0.094, and 0.078, for AR=1:1, AR=1:2, and AR=1:4 channels, respectively. The channel orientations are set as 90 degrees, the rotation number and inlet coolant-to-wall density ratio varied from 0.0 to 0.28 and from 0.13 to 0.40, respectively. The last type is the rotating two-pass smooth channel with three aspect ratios (AR=1:1; AR=1:2; AR=1:4). Detailed predictions of mean velocity, mean temperature and Nusselt number for two Reynolds numbers (Re=10,000 and Re=100,000) were carried out. The rotation number and inlet coolant-to-wall density ratio varied from 0.0 to 0.28 and from 0.13 to 0.40, respectively. A multi-block Reynolds-averaged Navier-Stokes (RANS) method was employed in conjunction with a near-wall second-moment turbulence closure.

A three dimensional numerical model for a micro proton exchange membrane fuel cell was developed to simulate the concentration distribution of the fuel gas, and analyze the flow field and current field in the fuel cell. Finite control volume scheme with SIMPLEC algorithm was employed in the numerical method. Various operating conditions on the performance of the fuel cell were studied. It was shown that the concentration of oxygen at the cathode can strongly influence the cell performance. Increase the operating temperature and the pressure of the inlet gas can improve the performance of the fuel cell.

Proton exchange membrane (PEM) fuel cell possesses the characteristics of microminiaturization and low temperature operation. For this reason, the proton exchange membrane fuel cell is very suitable to serve as power source of portable electronic products. In this paper, a three-dimensional numerical model to evaluate the voltage and the total current density of a PEM fuel cell stack was developed. The polarization curves of the PEM fuel cell stack under three different operating temperatures were investigated. In this study, the micro PEM fuel cell stack contains two single cells. Pure H2 gas stream was supplied as the anode inlet flow and air as the cathode inlet flow under constant pressure at 97 kPa and constant cell temperate (298K¡B308K¡B323K) conditions. Because the cell temperature may affect the chemical reaction rate on the cathode side, we discussed the influences of different temperatures on the cell performance. Solutions were compared with the experimental data. Both the value of power density and the tendency of polarization curve are in good agreement with the experimental data.

Thesis (M. Sc.(Mathematics and Applied Mathematics))--University of Pretoria, 2009. / Summary in English. Includes bibliographical references.

Thesis (M.S.)--University of Delaware, 2009. / Principal faculty advisors: Kenneth E. Barner and Karl V. Steiner, Dept. of Electrical & Computer Engineering. Includes bibliographical references.

Thesis (Ph. D. in Applied Mathematics)--Naval Postgraduate School, June 2003. / Dissertation supervisors: Beny Neta, Dan Givoli. Includes bibliographical references (p. 131-133). Also available online.

Thesis (Ph. D.)--Tampere University of Technology, 2002. / Includes bibliographical references. Also available on the World Wide Web.