Large-eddy simulation of a rotor tip-clearance flow

Abstract

A large-eddy simulation (LES) solver which combines an immersed-boundary technique with a curvilinear structured grid has been developed to study the temporal and spatial dynamics of a rotor tip-clearance flow, with the objective of determining the underlying mechanisms for low pressure fluctuations downstream of the rotor near the endwall. Salient feature of the numerical methodology, including the mesh topology, the treatment of numerical instability for non-dissipative schemes in a highly skewed mesh, and the parallelization of the code for shared memory platforms are discussed. Qualitative agreements have been observed between present LES and experimental measurements. The simulations indicate that the interaction between the moving endwall boundary layer and blade boundary layers and tip-leakage flow creates a highly complicated flow which is dominated by distinct vortical structures including the tip-leakage and tip-separation vortices. These vortical structures are found to convect downstream, expand in size and generate intense turbulent fluctuations in the endwall region.

Advances in large eddy simulation methodology for complex flows

“…advantageous to combine the IB technique with a structured curvilinear mesh topology. This novel approach is applied in an ongoing large-eddy simulation of the tip-clearance flow in a stator-rotor combination (You et al, 2002). A schematic of the flow configuration is shown in Fig.…”

Analysis of stability and accuracy of finite-difference schemes on a skewed mesh

“…The detrimental effects of highly skewed meshes on the 0021-9991/$ -see front matter Ó 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.jcp.2005.08.007 solution quality and numerical stability have been reported in a number of recent large-eddy simulations [1][2][3]. For example, You et al [1] observed severe numerical instability in a large-eddy simulations of rotor tip-leakage flow which advects through a highly skewed mesh.…”

“…doi:10.1016/j.jcp.2005.08.007 solution quality and numerical stability have been reported in a number of recent large-eddy simulations [1][2][3]. For example, You et al [1] observed severe numerical instability in a large-eddy simulations of rotor tip-leakage flow which advects through a highly skewed mesh. By performing numerical tests, they found that a simulation employing the divergence or skew-symmetric form of the nonlinear terms in the Navier-Stokes equations produces a more stable solution than employing the advection form.…”

A Review of Tip Clearance in Propeller, Pump and Turbine

“…They developed an LES code using immersed boundary and grid refinement, and validated the code using the measurement data [34]. Thereafter, they applied the LES method to study the tip-clearance flow mechanism in hydraulic turbomachines [35,36]. As shown in Figure 14, the tip-clearance flow can be divided into three parts: the TLV, the tip-separation vortex, and the induced vortex.…”

“…Therefore, the basic vortex types and their corresponding characteristics should be clarified. You and Moin [34][35][36][37][38][39][40][41] systematically analyzed the flow pattern near the tip clearance in a turbomachinery and its temporal and spatial evolution. They developed an LES code using immersed boundary and grid refinement, and validated the code using the measurement data [34].…”