Heat Transfer Analysis of a 50% Scale Formula 1 Wheel Assembly

The heat transfer of a 50% scale model F1 wheel assembly has been analysed experimentally with hot films, using a brake cooling test rig for internal analyses, and the Durham University wind tunnel for combined internal and external analyses. Computational analysis using the Exa PowerFlow CFD software was undertaken as both a correlation exercise, and to complement the experimental results, providing insight into the flow characteristics within the wheel assembly. The systematic error within the system was evaluated by determining the level of heat transfer at zero-flow conditions, which led to the conclusion that varying flow application method does not affect the disc heat transfer coefficient. Experimental and computational results were used to derive the Nusselt number equation, with the wind tunnel disc revealing a Reynolds number exponent of 0.87, a figure closely correlating to literature. Results for the sidewall presented a range of heat transfer values, to which a combined model fit was applied. Investigations into unmatched tyresurface velocity and flow velocity determined that 77% of the convective heat transfer experienced at the sidewall was due solely to the tyre’s rotation. The level of applied air-flow, did however, affect the rate of heat transfer. Internal of the upright, comparison of results for a blocked and open Inlet scoop found the Inlet scoop to be the predominant source of cooling to the disc. Wind tunnel heat transfer coefficientresults for the tyresidewall displayed a relationship to radial position, with HTC increasing from the central position of the sidewall both toward the internal diameter and external diameter. The capability of the CFD software to extract heat transfer coefficients was assessed using two rotational simulation methods; Sliding mesh (physical rotation) and moving reference frame(imposed rotation through the application of rotational fluid forces), neither of which was able to reproduce the patterns of heat transfer outlined in the wind tunnel results

A computational model for analysis of uncoupled NO synthase on nitric oxide and superoxide interaction in microcirculation

Nitric oxide (NO) produced by endothelial cells is a key component for blood-vessel dilation. Dilation is achieved through smooth muscle relaxation as a response to NO transport. Inhibition of this process occurs through the inactivation of NO by reactive oxygen species, especially superoxide (O2 -). NO and superoxide react quickly, forming peroxynitrite (ONOO-). Both superoxide and peroxynitrite apply oxidative stress on vascular tissue. Experimental studies investigating NO interactions are difficult since these reactions occur rapidly and over small distances. This study presents a computational model to describe the interactions of NO, superoxide, and peroxynitrite across an arteriole/venule pair. Based on principles of mass transport, and using knowledge of chemical concentrations and reaction rates, a mathematical model was developed to generate the concentration profiles for NO, O2 -, and ONOO-. We simulated excessive oxidative stress by uncoupled eNOS and determined its effect on NO concentration profiles throughout the region. Based on our understanding of the interactions involved, we predicted 1) increased oxidative stress in the venule decreases NO levels in regions of both the venule and neighboring arteriole, and 2) the amount of NO reduction will vary depending on the location of O2 - increase. The model demonstrates that different sources of O2 - have varied effects on NO concentration profiles, and excessive oxidative stress in the venule can impact NO levels in the venule as well as the arteriole. The results provide a more complete description of nitric oxide transfer, which is an important step toward understanding vascular complications in many pathological conditions

Advanced Simulation of Particle Processing: The Roles of Cohesion, Mass and Heat Transfer in Gas-Solid Flows

This dissertation addresses the simulation of several important unit operations in the field of granular processing, which includes particle mixing and segregation, cohesive gas-solid flows, liquid transfer between particles, heat transfer in gas-solid flows and the drying process in gas-solid flows. Particle dynamics (PD) is employed to probe the solid flows and computational fluid dynamics (CFD) is used to simulate the gas phase.Achieving good mixing of free-flowing particulate solids with different properties is not a trivial exercise. By introducing periodic flow inversions, we show both experimentally and computationally that forcing with a value above a critical frequency can effectively eliminate both density and size segregation.The mechanics of cohesive flowing gas-particle systems is still poorly understood. Toward that end, we introduce a discrete characterization tool for gas-solid flow of wet (cohesive) granular material- the Granular Capillary Number. The utility of this tool is computationally tested over a range of cohesive strengths in two prototypical applications of gas-solid flows.While slow granular flows have been an area of active research in recent years, heat transfer in flowing particulate systems has received relatively little attention. We employ a computational technique that couples the PD, CFD, and heat transfer calculations to simulate realistic heat transfer in a rotary kiln. Our results suggest a transition in heat transfer regime as the conductivity of the particles changes.Liquid transfer between particles plays a central role in the operation of a variety of particle processing equipment. We introduce a dynamic liquid transfer model for use in PD of heterogeneous particle systems. As a test of this new model we present results from the simulation of a rotary drum spray-coating system.The drying process in gas-solid flows involves complex mass, momentum and heat transfer. By incorporating mass transfer modeling into our existing gas-solid PD-based heat transfer code, the drying process is successfully simulated. Results are reported for both mono-disperse and bi-disperse cases.Finally, we outline how to simulate amphiphilic particles, which are spheres comprised of two parts. We use the quaternion method to track the particle rotation, such that we can study the issues relating to anisotropic particles

An analysis of test data selection criteria using the RELAY model of fault detection

RELAY is a model of faults and failures that defines failure conditions, which describe test data for which execution will guarantee that a fault originates erroneous behavior that also transfers through computations and information flow until a failure is revealed. This model of fault detection provides a framework within which other testing criteria's capabilities can be evaluated. In this paper, we analyze three test data selection criteria that attempt to detect faults in six fault classes. This analysis shows that none of these criteria is capable of guaranteeing detection for these fault classes and points out two major weaknesses of these criteria. The first weakness is that the criteria do not consider the potential unsatisfiability of their rules; each criterion includes rules that are sufficient to cause potential failures for some fault classes, yet when such rules are unsatisfiable, many faults may remain undetected. Their second weakness is failure to integrate their proposed rules; although a criterion may cause a subexpression to take on an erroneous value, there is no effort made to guarantee that the intermediate values cause observable, erroneous behavior. This paper shows how the RELAY model overcomes these weaknesses

Evolutionary Effects of Irradiation in Cataclysmic Variables.

We developed a simple stellar computational model consisting of two concentric polytropic shells in order to investigate compact binary evolution. In this thesis we focus the investigation on the effects of irradiation on the orbital evolution of cataclysmic variables (CVs). In these systems, when the companion is illuminated by a fraction of the accretion luminosity, the orbital evolution consists of irradiation-driven limit cycles on thermal timescales. These cycles are superimposed on the secular evolution toward shorter periods due to systemic angular momentum losses. When the irradiation instability is enhanced by consequential angular momentum losses j\sb{\rm CAML} the net effect is that mass transfer rates vary by orders of magnitude at any given period. This result agrees with observations which show a large dispersion in disk luminosities, associated with mass transfer rates, for all CV periods. The standard theoretical model without irradiation (i.e. the secular evolution) predicts an approximately constant mass transfer rate throughout the binary evolution. In addition, we show that large amplitude positive orbital period derivatives during bright phases are a natural consequence of the expansion of the companion during high mass transfer phases in the limit cycle. We investigate the secular evolution of cataclysmic binaries under the combined effects of irradiation and j\sb{\rm CAML} and show that faster than secular orbital period excursions of either sign may occur. If indeed irradiation-driven mass transfer fluctuations on timescales faster than secular as discussed in this thesis occur, then we may predict the relative abundances of the different types of cataclysmic variables at a given orbital period. For example this mechanism may explain the relative paucity of dwarf novae with respect to nova-like variables with orbital periods between 3 and 4 hours

Numerical analysis of an annular water-air jet pump with self-induced oscillation mixing chamber

This paper presents an improved annular water-air jet pump concept design through integrating a self-induced oscillation mixing chamber with the conventional annular jet pump (AJP). The internal flow characteristics for both conventional and improved AJP were numerically investigated and compared by a validated computational fluid dynamics model. The numerical comparison demonstrated an approximately 10% pumping performance increase compared with the conventional pump, which is mostly attributed to the improved mass and energy transfer along the oscillating phase interface. Furthermore, transient flow analysis was conducted to resolve the unsteady self-introduced oscillation. The results revealed the self-introduced oscillation induces a continuous break-up and formation of fresh water-air interfaces, which exhibits a periodic feature with a dominant frequency of 147 Hz for the current design under given operational conditions. This study contributes toward a better understanding of the internal annular water-air jet pump flow patterns, and also demonstrates the feasibility of incorporating self-introduced oscillation chamber into AJP design