Development of Two-Dimensional Wakes Within Curved Channels, Theoretical Framework and Experimental Investigation

Abstract

The development of a wake flow downstream of a cylindrical rod within a curved channel under zero streamwise pressure gradient is theoretically and experimentally investigated. The measured asymmetric wake quantities such as the mean velocity and turbulent fluctuations in longitudinal and lateral directions as well as the turbulent shear stress are transformed from the probe coordinate system into the curvilinear wake eigen-coordinate system. For the transformed non-dimensionalized velocity defect and the turbulent quantities, affine profiles are observed throughout the flow regime. Based on these observations and using the transformed equations of motion and continuity, a theoretical frame work is established that generally describes the two-dimensional curvilinear wake flow. The theory also describes the straight wake as a special case, for which the curvature radius approaches infinity. The comparison of the theory with the experimental data pertaining to the curvilinear and straight wakes demonstrate the general validity of the theory.

Periodic Unsteady Flow Aerodynamics and Heat Transfer: Studies on a Curved Surface, Combined Part I and II

“…The wake generator rotates counterclockwise from the point of view of Fig. 3 Schobeiri et al (1996) show that the wake drag coefficient is approximated as CD 1.0 for a distance/diameter ratio of Xple/d R 126.5 (see Table I). The parameter f is related to the Strouhal number introduced by Speidel (1957) and taken over by several researchers.…”

Intermittent Behavior of the Separated Boundary Layer Along the Suction Surface of a Low Pressure Turbine Blade Under Periodic Unsteady Flow Conditions

“…The sensor also serves as the triggering mechanism for data transfer and its initialization, which is required for ensemble-averaging. This type of wake generator produces clean 2-dimensional wakes, whose turbulence structure, decay and development is, to a great extent, predictable [30]. The unsteady boundary layer transition and heat transfer investigations [1], [2], [27], [28] performed on this facility serve as the bench mark data for validation of turbulence models, transition models, and general code assessments.…”

“…In this form, however, they cannot quantitatively describe the complex unsteady transition process. To establish the basic relations essential for a quantitative description of the unsteady boundary layer transition, we resort to the fundamental studies by Schobeiri and his co-workers ( [14], [27], [30]) that deal with the physics of steady and unsteady wake development in a curved environment. These studies show that the turbulence structure of the steady and unsteady wake flow is determined by the wake defect, which is a Gaussian function.…”

“…To simulate the wake width and spacing that stem from the trailing edge of rotor blades, the diameter and number of rods can be varied. The rod diameter, its distance from the LPT blade leading edge, the wake width and the corresponding drag coefficient is chosen according to the criteria outlined by Schobeiri et al [30]. The belt-pulley system is driven by an electric motor and a frequency controller.…”

Aerodynamic and Performance Behavior of a Three‐Stage High Efficiency Turbine at Design and Off‐Design Operating Points

“…of steady and unsteady wake development under turbomachinery specific conditions. Schobeiri et al (1994) investigated the phenomenon of steady wake development and decay and established a comprehensive theoretical frame-work. Schobeiri and his co-workers also extended the theoretical work by Schobeiri et al (1995a) to a relative frame of reference to explain the development and decay of unsteady wakes.…”