UFR 2-07 Description
3D flow around blades
Underlying Flow Regime 2-07 © copyright ERCOFTAC 2004
The flow around turbomachinery blades is an important flow type for the power generation and aeropropulsion industries. The NATO Advisory Group for Aerospace Research and Development (AGARD) sponsored and documented many experimental studies of turbomachinery flow, including studies involving flow in and around single blade rows. In AGARD's Advisory Report No. 275, the results of these experiments were published with the expressed intention of their comparison for computational studies. Two well-known, well-studied and well-published cases from this Advisory Report are the NASA-designed, single transonic fan rotors Rotor 37 and Rotor 67. As it had been discovered by independent researchers that the experimental data for Rotor 37 is flawed due to a hub leakage , Rotor 67 was chosen for this study. Transonic, three-dimensional flows represent severe challenges for any numerical flow prediction method: the thorough description of one such analysis therefore lends itself well as an Underlying Flow Regime demonstration.
With possible exceptions of unsteady flow and separated flow, three-dimensional, transonic flow prediction represents the most difficult task for CFD engineers. Rotor 67 is a fan rotor whose flow can be classified as both highly three-dimensional and transonic. The Mach number measured along the span at the leading-edge of the blade varies from 0.6 to 1.4, and both inlet and outlet measured boundary conditions strongly indicate the presence of a boundary layer at the fan hub and casing.
Review of UFR studies and choice of test case
Numerical and experimental studies of three-dimensional turbomachinery flow are to be found numerous times monthly in journals; however, often the cases focus on intricate blade designs, stall characteristics, or other minutiae which disqualify their inclusion as a case demonstrating an underlying flow regime (hereafter ‘UFR’). Rotors 37 and 67 were ideal candidates for a UFR because of their generality and thorough documentation. Rotor 37 was disqualified because of the hub leakage flow identified by a subsequent team. The experimental setup and subsequent documentation of Rotors 37 and 67 were designed for the purpose of CFD validation, as is evidenced by the title of the AGARD Advisory Report.
© copyright ERCOFTAC 2004
Contributors: William Anderson - ALSTOM Power (Switzerland) Ltd