Internal Duct Cooling (IDC) with rib turbulators is one of the common cooling techniques applied inside the turbine airfoils. It is very important for the gas turbine industry to design and develop an optimized cooling channel that maximizes the amount of heat removed, while simultaneously minimizing the pressure drop for a target overall cooling effectiveness. Angled ribs perform superior to the transverse ribs due to additional secondary flow associated with them. However, they result in a highly non-homogenous heat transfer distribution, which is a manifestation of the complex, turbulent flow field inside the channel. It is very important to comprehend the secondary flow physics to characterize the heat transfer distribution in such angled ribbed channels. Additionally, due to the manufacturing constraint, the gas turbine industry encounters a challenge to make ribs edge sharp and results in ribs with rounded edges. The one of the main objectives of the present study is to provide a fundamental understanding of the flow physics on the heat transfer and pressure drop behavior in 45° ribbed channels both with sharp and rounded-edge ribs. It is found that the secondary flow has a significant effect on the heat transfer behavior for both types of ribs. There is a great need of high-fidelity PIV flow field data in the inter-rib space for an angled ribbed channel which can be used for CFD validation, especially for LES. The current study provides benchmarking flow field data in the inter-rib space in a square channel with 45° ribs using stereoscopic PIV technique. Besides the experiments, numerical studies were also conducted by using LES and different RANS models. The LES results show an excellent prediction capability for aerothermal behavior in such channels. However, the prediction capability of RANS models is found to be inconsistent for different rib configurations and flow conditions.
Doctor of Philosophy (Ph.D.)
College of Engineering and Computer Science
Mechanical and Aerospace Engineering
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Ahmed, Lumaya, "Detailed Understanding of Flow, Heat Transfer, and Pressure Drop Behavior in a Square Channel With 45 Deg Ribs" (2018). Electronic Theses and Dissertations, 2004-2019. 6249.