Large eddy simulation of unsteady flows in turbomachinery

Lee, S.; Kim, H.-J.; Runchal, Akshai K.

doi:10.1243/0957650042457006

Cited by 10 publications

(3 citation statements)

References 23 publications

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“…In addition, the turbulence closure is addressed using an LES scheme, which solves directly the large scales of the flow, but models the effect of eddies smaller than the grid cell size. In the case of turbomachinery, with typical high Reynolds numbers, it is important to rely on an appropriate model for these scales (Lee et al , 2004). A subgrid scale model is introduced after filtering the incompressible Navier–Stokes equations (in the following, a hat denotes a subgrid average).…”

Section: Numerical Methodology and Les Computationsmentioning

confidence: 99%

LES-based simulation of the time-resolved flow for rotor-stator interactions in axial fan stages

Oro

Meana-Fernández

Vega

et al. 2019

HFF

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Purpose The purpose of this paper is the development of a CFD methodology based on LES computations to analyze the rotor–stator interaction in an axial fan stage. Design/methodology/approach A wall-modeled large eddy simulation (WMLES) has been performed for a spanwise 3D extrusion of the central section of the fan stage. Computations were performed for three different operating conditions, from nominal (Q_N) to off-design (85 per cent Q_N and 70 per cent Q_N) working points. Circumferential periodic conditions were introduced to reduce the extent of the computational domain. The post-processing procedure enabled the segregation of unsteady deterministic features and turbulent scales. The simulations were experimentally validated using wake profiles and turbulent scales obtained from hot-wire measurements. Findings The transport of rotor wakes and both wake–vane and wake–wake interactions in the stator flow field have been analyzed. The description of flow separation, particularly at off-design conditions, is fully benefited from the LES performance. Rotor wakes impinging on the stator vanes generate a coherent large-scale vortex shedding at reduced frequencies. Large pressure fluctuations in the stagnation region on the leading edge of the vanes have been found. Research limitations/implications LES simulations have shown to be appropriate for the assessment of the design of an axial fan, especially for specific operating conditions for which a URANS model presents a lower performance for turbulence description. Originality/value This paper describes the development of an LES-based simulation to understand the flow mechanisms related to the rotor–stator interaction in axial fan stages.

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Section: Numerical Methodology and Les Computationsmentioning

confidence: 99%

LES-based simulation of the time-resolved flow for rotor-stator interactions in axial fan stages

Oro

Meana-Fernández

Vega

et al. 2019

HFF

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“…The unsteady flows for a forward multi-wing centrifugal fan are essential to study the rotation stall flow field characteristics at small flow conditions. Lee et al [1] studied the unsteady flows in turbomachinery by means of the large eddy simulation. Conway et al [2] analyzed the flow through the blades in a swirl generator by the large eddy simulation.…”

Section: Introductionmentioning

confidence: 99%

Unsteady Characteristics of Forward Multi-Wing Centrifugal Fan at Low Flow Rate

Lun

Ye²,

Lin³

et al. 2019

Processes

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The unsteady flow characteristics of a forward multi-wing centrifugal fan under a low flow rate are studied using the computational fluid dynamics (CFD) method. This paper emphasizes the eddy current distribution in terms of the Q criterion method, as well as pressure fluctuation, frequency spectrum, and kinetic energy spectrum analysis of internal monitoring points in a forward multi-wing centrifugal fan. The numerical results show that abnormal eddies mainly appear at the volute outlet and near the volute tongue, boundary layer separation occurs near the suction surface of the blade, and shedding eddies appear at the trailing edge of the blade with the time evolution. The unsteady flow characteristics of a forward multi-wing centrifugal fan at a small flow rate provide significant physical insight into understanding the internal flow law.

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“…The numerical solutions for the viscous flow of centrifugal turbomachinery are made by the RANS calculations from the 1980s [1][2][3]. More recently, LES techniques have been attempted to simulate unsteady flows of turbomachinery [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Computation of aerodynamic noise of centrifugal fan using large eddy simulation approach, acoustic analogy, and vortex sound theory

Liu

Tang

2007

Proceedings of the Institution of Mechanical Engineers, Part C:

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Large eddy simulation is applied to solve the unsteady three-dimensional viscous flow in the whole impeller-volute configuration of a centrifugal fan. The results of the simulation are used to predict the impeller-volute interaction and to obtain the unsteady pressure, velocity, and vorticity fluctuations in the impeller and volute casing. The simulation at the design point is carried out with the wall-adapting local eddy-viscosity subgrid-scale model and a sliding mesh technique is applied to consider the impeller-volute interaction. The results show that a strongly unsteady flow field occurs in the impeller and volute casing of the fan, and the flow is characterized with obvious pressure and vorticity fluctuations, especially at the tongue and at the blade wake region. The large pressure fluctuation at the tongue and the large fluctuation of the blade wake vorticity appear as the blade wake is passing the tongue. Acoustic analogy and vortex sound theory are used to compute the radiated dipole and quadrupole sound fields, which are in good agreement with the experiment. The sound results show that the vortex sound theory is convenient for the broadband noise computation, and the dipole sound is much higher than the quadrupole sound. The dipoles, distributed over the volute tongue surface, are the dominant sound source of the fan.

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Large eddy simulation of unsteady flows in turbomachinery

Cited by 10 publications

References 23 publications

LES-based simulation of the time-resolved flow for rotor-stator interactions in axial fan stages

LES-based simulation of the time-resolved flow for rotor-stator interactions in axial fan stages

Unsteady Characteristics of Forward Multi-Wing Centrifugal Fan at Low Flow Rate

Computation of aerodynamic noise of centrifugal fan using large eddy simulation approach, acoustic analogy, and vortex sound theory

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