Progress In Computational Research

The numerical calculations will be performed in order to understand the basic flow mechanisms, and to extend the parametric range possible with the experiments. RANS simulations and LES (large Eddy Simulations) will be used to provide a description of the flow field for the various parameters where measurements of heat transfer are made in the experimental phase of work. Agreement between the computed and measured heat transfer field will provide confidence in the predictions, and the velocity predictions can be used in understanding the heat transfer behavior in the parameter ranges of interest. The RANS simulations will also be used to extend the parametric range beyond those considered in the experiments.

The specific goals of the computational research are as follows:

□ Perform turbulence model validation for a ribbed coolant channel in the periodically-developed module at low buoyancy parameter and no-rotation. For model validation, use published data (heat transfer and velocity) and LES at lower Re values and the present heat transfer data at higher Re values.

□ Perform RANS simulations, with the appropriate turbulence models, for the full range of parameters for a smooth channel. Evaluate the turbulence model by comparison with current data.

□ Perform RANS simulations for the full range of parameters for the ribbed channel. Use the predictions to get the flowfield associated with the measured heat transfer information. The predicted flowfield and the measured heat transfer data provide a complete picture of the physical process.

□ Use RANS simulations to extend the parametric range, and investigate triangular cavities, Reynolds number up to a million, rotation number up to 1 and buoyancy parameters up to 10.

The following achievements have been completed to date:

1. RANS simulations for a two pass coolant channel (square cross-section, 1:4, and 4:1) with smooth walls, normal trips and inclined trips. Results have been obtained for both stationary and rotating cases and compared with Johnson and Wagner's data with good agreement.

2. LES of flow in smooth and ribbed (normal-trips) duct for stationary and rotating conditions. Results are compared with Johnson and Wagner's data, and provide detailed understanding of flow and heat transfer physics, and how they are influenced by Coriolis and buoyancy forces.

Current activities are focusing on simuations in 1:4 and 4:1 aspect ratios at high Reynolds numbers (up to 500,000) and buoyancy parameters (up to 5).

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