Conditionally-averaged structures in wall-bounded turbulent flows

The quadrant-splitting and the wall-shear detection techniques were used to obtain ensemble-averaged wall layer structures. The two techniques give similar results for Q4 events, but the wall-shear method leads to smearing of Q2 events. Events were found to maintain their identity for very long times. The ensemble-averaged structures scale with outer variables. Turbulence producing events were associated with one dominant vortical structure rather than a pair of counter-rotating structures. An asymmetry-preserving averaging scheme was devised that allowed a picture of the average structure which more closely resembles the instantaneous one, to be obtained

Transient Analysis and Modeling of Automotive PEM Fuel Cell System Accounting for Water Transport Dynamics

ABSTRAC

A 1-D PLANAR SOLID OXIDE FUEL CELL MODEL FOR SIMULATION OF SOFC-BASED ENERGY SYSTEMS

ABSTRACT A one-dimensional steady-state model for planar solid oxide fuel cells (SOFCs) is presented. Appropriately simplified, the model includes sufficient detail for supporting ongoing investigations involving the simulation of SOFC-based advanced energy systems. The presentation focuses on a set of nonlinear equations accounting for conservation of mass and energy along a single SOFC in a co-flow configuration. Electrochemical models also are employed, including one previously used for a zero dimensional approach. The equations are described through a phenomenological approach based on the best recent work in the field and model validation is carried out in two distinct phases using previously published information. Potential areas of application for the model presented are noted. INTRODUCTION The objective of this paper is to report on work in progress aimed at simulating advanced energy systems having a solid oxide fuel cell as a principal component. For such work it is sufficient to employ a simplified SOFC model that captures the salient physical/chemical effects. Accordingly, efforts thus far have centered on the development of a one-dimensional SOFC model resting solidly on the best recent work in the field, while being convenient and effective for achieving the larger goal of simulating SOFC-based advanced energy systems. The intent of this modeling effort is to be able to handle both the hydrogen and internal reforming cases, while representing the electrochemistry using either a grey box approach or black box approach. Specifically in this paper, a 1-D model has been developed that captures the dominant physical and electrochemical phenomena taking place in a co-flow planar SOFC, accounting for internal reforming while retaining computational simplicity and good accuracy. The objective of the model is to simulat

Daisie D. Boettner Gino Paganelli Proton Exchange Membrane Fuel Cell System Model for Automotive Vehicle Simulation and Control

This paper describes a proton exchange membrane (PEM

Flow Visualization of Forced and Natural Convection in Internal Cavities

The report descries innovative flow visualization techniques, fluid mechanics measurements and computational models of flows in a spent nuclear fuel canister. The flow visualization methods used a fluid that reacted with a metal plate to show how a local reaction affects the surrounding flow. A matched index of refraction facility was used to take mean flow and turbulence measurements within a generic spent nuclear fuel canister. Computational models were also made of the flow in the canister. It was determined that the flow field in the canister was very complex, and modifications may need to be made to ensure that the spent fuel elements are completely passivated