Title page for ETD etd-08042006-141944


Type of Document Dissertation
Author Viswanathan, Aroon Kumar
Author's Email Address aroonkv@vt.edu
URN etd-08042006-141944
Title Detached Eddy Simulation of Turbulent Flow and Heat Transfer in Turbine Blade Internal Cooling Ducts
Degree PhD
Department Mechanical Engineering
Advisory Committee
Advisor Name Title
Tafti, Danesh K. Committee Chair
Devenport, William J. Committee Member
Diller, Thomas E. Committee Member
Hajj, Muhammad R. Committee Member
Ng, Fai Committee Member
Keywords
  • Detached Eddy Simulations (DES)
  • turbine blade internal cooling
  • ribbed ducts
  • centrifugal buoyancy
  • Coriolis forces
Date of Defense 2006-07-31
Availability unrestricted
Abstract
Detached Eddy Simulations (DES) is a hybrid URANS-LES technique that was proposed to obtain computationally feasible solutions of high Reynolds number flows undergoing massive separation with reliable accuracy. Since its inception, DES has been applied to a wide variety of flow fields, but mostly limited to unbounded external aerodynamic flows. This is the first study to apply and validate DES to predict the internal flow and heat transfer in non-canonical flows of industrial relevance. The prediction capabilities of DES in capturing the effects of Coriolis forces, which are induced by rotation, and centrifugal buoyancy forces, which are induced by thermal gradients, are also authenticated.

The accurate prediction of turbulent flows is sensitive to the level of turbulence predicted by the turbulence scheme. By treating the regions of interest in LES mode, DES allows the unsteadiness in these regions to develop and hence predicts the turbulence levels accurately. Additionally, this permits DES to capture the effects of system rotation and buoyancy. Computations on a rotating system (a sudden expansion duct) and a system subjected to thermal gradients (cavity with a heated wall) validate the prediction capability of DES.

The application of DES is further extended to a non-canonical, internal flow which is of relevance in internal cooling of gas turbine blades. Computations of the fully developed flow and heat transfer shows that DES surpasses several shortcomings of the RANS model on which it is based. DES accurately predicts the primary and secondary flow features, the turbulence characteristics and the heat transfer in stationary ducts and in rotating ducts, where the effects of Coriolis forces and centrifugal buoyancy forces are dominant. DES computations are carried out at a computational cost that is almost an order of magnitude less than the LES with little compromise on the accuracy.

However, the capabilities of DES in predicting the transition to turbulence are inadequate, as highlighted by the flow features and the heat transfer in the developing region of the duct. But once the flow becomes fully turbulent, DES predicts the flow physics and shows good quantitative agreement with the experiments and LES.

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