Semester

Fall

Date of Graduation

2003

Document Type

Dissertation

Degree Type

PhD

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Ismail B. Celik.

Abstract

The objective of this study is to investigate curved buoyant jets in an enclosure using Large Eddy Simulation (LES) methods with an Implicit Turbulent Model (ITM). To accomplish this goal, a numerical solver was written, named DREAMRTM, which is capable of solving three dimensional, transient flows using an accurate monotonic and non-oscillatory upwinding scheme. The three-dimensional Navier-Stokes equations are solved in Cartesian coordinates, with the control volume approach being implemented on a staggered grid. The numerical scheme uses a fractional time step method, with the overall spatial and temporal accuracy being second order.;In ITM simulations, there is no explicit subgrid-scale model (SGS) used for the modeling of the small scale vortical structures. ITM simulations assume that through strict conservation of the fluxing quantities in and out of the cell, the grid resolution is fully capable of capturing the important scales of the flow. The volume averaging techniques used in the ITM methods acts as an implicit subgrid-scale model, and the resolvable scales of the flow are only dependent on the grid resolution within the domain. Comparison of the available experimental data, as well as simulations that used SGS models, to the ITM simulations from DREAMRTM compare favorably for most results.;For the simulations presented in this study, oil is injected at a specified flow rate into a water filled tank, initially taken to be stagnant. Results show that the density stratification tends to damp the amount of turbulence present within the jet near the interface, but overall increases turbulence because of the acceleration of the fuel. Analysis of the curved buoyant jet shows that at an appropriate downstream location, similarity is achieved, and the energy spectrum shows the appropriate inertial subrange characteristics. Impingement of the curved buoyant jet onto the upper wall increases the amount of turbulent present within the enclosure and comparison to vertical buoyant jet simulations with comparable dimensionless parameters shows wall effects may never be completely eliminated from the analysis. Comparison between the curved buoyant jet simulations to the available experimental data from experiments performed explicitly for this study shows good agreement for the buoyant path centerline locations based on the internal densimetric Froude number. The application of these methods to immiscible fluids shows a new dimension to ITM and allows for a high resolution of the resulting flow field without the need for an explicit SGS model. Simulations for the vertical and curved buoyant jet indicate the necessity for small timesteps and increased grid resolution.

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