Thesis (Ph.D.) - University of Queensland, 2005. / Includes bibliography.

Dissertation (Ph.D.) -- Worcester Polytechnic Institute. / Keywords: Turbulence; mixing length; vortical structure. Includes bibliographical references (p.).

No description available.

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 139-148).

Th.--Sci. phys.--Toulouse--I.N.P., 1983. N°: 70.

Th. doct.-ing.--Méc.--Toulouse--I.N.P., 1982. N°: 204.

Th.--Doct.-ing.--Lille 1, 1980. N°: 250.

Th. doct.-ing.--Toulouse, I.N.P., 1978. N°: 25.

In this thesis, the flow and heat transfer in dimpled channels have been investigated using the Reynolds-averaged Navier-Stokes (RANS) approach. The primary objective of this investigation is to identify the capabilities of RANS models to reproduce the characteristics of the flow and heat transfer in dimples. The flow in dimpled channels has been chosen as the test case due to their relevance to gas turbine cooling applications, as well as the fairly complex flow features over dimples, which poses a challenge to turbulence modelling. Five turbulence models have been tested in the present work. These include: the Launder and Sharma k-epsilon model, both the Craft et al. (1996) and (2000) cubic k-epsilon models, the Hanjalic and Jakirlic Reynolds stress model (RSM), as well as the Craft (1998) two-component limit (TCL) RSM. The models have been chosen such that all three classes of RANS closure were tested. The tested models have been applied to two dimpled channel configurations with increasing complexity. In the first, the flow over a single dimple in a channel has been considered, while in the second, the case of a staggered array of dimples has been examined. Moreover, across these two configurations, the effect of the dimple depth, the channel height and the Reynolds number have also been investigated. The results show that all models produce a physically viable solution for the problem of the flow in dimpled channels. Nevertheless, the Craft et al. (1996) and (2000) cubic k-ε models, as well as the Craft (1998) TCL RSM, predicted dimple flow structures that deviate from the expected state. In general, the main flow characteristics are reproduced by the RANS models, and the predicted mean velocity profiles are in good agreement with the data. All models report an overall enhancement in heat transfer levels when using dimples in comparison to those of a plane channel.

Although turbulence near the ocean surface is of great significance to the air-sea exchange of heat, gas and momentum it is a poorly understood phenomenon especially at high wind speeds when vertical transfer processes tend to be greatest. This work evaluates ocean surface turbulence at high sea states by exploiting heat as a naturally occurring passive tracer. To this end, a freely drifting instrument with a mechanically driven temperature profiler, fixed depth thermistors and conductivity cells was used to monitor the fine scale temperature structure and breaking wave activity. These open ocean measurements form the basis for a comprehensive account of the near surface turbulence field. Temperature profiles reveal a rich fine structure which, when combined with independent air-sea heat flux measurements reveal the presence of a surface layer of wave enhanced turbulence, modulated by subsurface advection associated with Langmuir circulation. The concept of wave enhanced turbulence, previously based on observations in fetch limited environments, is here extended to open ocean storm conditions. Generation of turbulence depends on the scale and frequency of breaking events. Our observations, which span a wide range of conditions from a coastal strait to the open ocean, show that wind speed or wave age are inadequate predictors of the occurrence frequency of wave breaking, motivating a scaling based on energy input. The decay of turbulence following wave breaking proceeds more rapidly than for isotropic turbulence, permitting generation of a thermal boundary layer a few centimetres thick, which accounts for brief temperature fluctuations observed beneath breaking waves. Advection due to Langmuir circulation also leaves its signature on the near surface temperature field. Both advection and enhanced diffusion are reconciled in a two-dimensional model of the upper ocean boundary layer, providing a framework for studying Langmuir circulation and upper ocean turbulence in terms of the measured temperature structure. The depth integrated dissipation derived from a model analysis of the data closely matches the energy input into the wave field, identifying breaking waves as the major source of turbulent kinetic energy. / Graduate