Large-eddy simulation of a rotor tip-clearance flow

2002 ◽  
Author(s):  
D. You ◽  
R. Mittal ◽  
M. wang ◽  
P. Moin
Keyword(s):  
Large Eddy Simulation ◽  
Tip Clearance ◽  
Tip Clearance Flow ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Clearance Flow

scholarly journals Verification and Validation of Large Eddy Simulation for Tip Clearance Vortex Cavitating Flow in a Waterjet Pump

Energies ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7635
Author(s):  
Chengzao Han ◽  
Yun Long ◽  
Mohan Xu ◽  
Bin Ji
Keyword(s):  
Large Eddy Simulation ◽  
Tip Clearance ◽  
Verification And Validation ◽  
Flow Structures ◽  
Tip Clearance Flow ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Clearance Flow ◽  
Vorticity Transport ◽  
Waterjet Pump

In this paper, large eddy simulation (LES) was adopted to simulate the cavitating flow in a waterjet pump with emphasis on the tip clearance flow. The numerical results agree well with the experimental observations, which indicates that the LES method can make good predictions of the unsteady cavitating flows around a rotor blade. The LES verification and validation (LES V&V) analysis was used to reveal the influence of cavitation on the flow structures. It can be found that the LES errors in cavitating region are larger than those in the non-cavitating area, which is mainly caused by more complicated cavitating and tip clearance flow structures. Further analysis of the interaction between the cavitating and vortex flow by the relative vorticity transport equation shows that the stretching, dilatation and baroclinic torque terms have major effects on the generation and transport of vortex structure. Meanwhile the Coriolis force term and viscosity term also exacerbate the vorticity transport in the cavitating region. In addition, the flow loss characteristics of this pump are also revealed by the entropy production theory. It is indicated that the tip clearance flow and trailing edge wake flow cause the viscous dissipation and turbulent dissipation, and the cavitation can further enhance the instability of the flow field in the tip clearance.

A Computational Methodology for Large-Eddy Simulation of Tip-Clearance Flows

2003 ◽  
Author(s):  
Donghyun You ◽  
Rajat Mittal ◽  
Meng Wang ◽  
Parviz Moin
Keyword(s):  
Large Eddy Simulation ◽  
Pressure Fluctuations ◽  
Spatial Dynamics ◽  
Quantitative Agreement ◽  
Tip Clearance ◽  
Immersed Boundary ◽  
Tip Clearance Flow ◽  
Mesh Topology ◽  
Eddy Simulation ◽  
Large Eddy

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 an incompressible rotor tip-clearance flow. The overall objective of these simulations is to determine the underlying mechanisms for low-pressure fluctuations downstream of the rotor near the endwall. Salient features of the numerical methodology, including the mesh topology, the immersed boundary method, the treatment of numerical instability for non-dissipative schemes on highly skewed meshes, and the parallelization of the code for shared memory platforms are discussed. The computational approach is shown to be capable of capturing the evolution of the highly complicated flowfield characterized by the interaction of distinct blade-associated vortical structures with the turbulent endwall boundary layer. Simulation results are compared with experiments and qualitative as well as quantitative agreement is observed.

scholarly journals Zonal Large-Eddy Simulation of a Fan Tip-Clearance Flow, With Evidence of Vortex Wandering

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Jérôme Boudet ◽  
Adrien Cahuzac ◽  
Philip Kausche ◽  
Marc C. Jacob
Keyword(s):  
Large Eddy Simulation ◽  
Good Description ◽  
Region Of Interest ◽  
Tip Clearance ◽  
Velocity Spectrum ◽  
Tip Leakage Flow ◽  
Tip Clearance Flow ◽  
Tip Leakage ◽  
Eddy Simulation ◽  
Large Eddy

The flow in a fan test-rig is studied with combined experimental and numerical methods, with a focus on the tip-leakage flow. A zonal RANS/LES approach is introduced for the simulation: the region of interest at tip is computed with full large-eddy simulation (LES), while Reynolds-averaged Navier–Stokes (RANS) is used at inner radii. Detailed comparisons with the experiment show that the simulation gives a good description of the flow. In the region of interest at tip, a remarkable prediction of the velocity spectrum is achieved, over about six decades of energy. The simulation precisely captures both the tonal and broadband contents. Furthermore, a detailed analysis of the simulation allows identifying a tip-leakage vortex (TLV) wandering, whose influence onto the spectrum is also observed in the experiment. This phenomenon might be due to excitation by upstream turbulence from the casing boundary layer and/or the adjacent TLV. It may be a precursor of rotating instability. Finally, considering the outlet duct acoustic spectrum, the vortex wandering appears to be a major contribution to noise radiation.

Computational Methodology for Large-Eddy Simulation of Tip-Clearance Flows

AIAA Journal ◽  
2004 ◽  
Vol 42 (2) ◽  
pp. 271-279 ◽  
Author(s):  
Donghyun You ◽  
Rajat Mittal ◽  
Meng Wang ◽  
Parviz Moin
Keyword(s):  
Large Eddy Simulation ◽  
Tip Clearance ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Computational Methodology

scholarly journals Zonal Detached-Eddy Simulation Applied to the Tip-Clearance Flow in an Axial Compressor

AIAA Journal ◽  
2016 ◽  
Vol 54 (8) ◽  
pp. 2377-2391 ◽  
Author(s):  
W. Riéra ◽  
J. Marty ◽  
L. Castillon ◽  
S. Deck
Keyword(s):  
Axial Compressor ◽  
Tip Clearance ◽  
Detached Eddy Simulation ◽  
Tip Clearance Flow ◽  
Eddy Simulation ◽  
Clearance Flow

Short Length-Scale Rotating Stall Inception in a Transonic Axial Compressor: Criteria and Mechanisms

2006 ◽  
Author(s):  
Chunill Hah ◽  
Jo¨rg Bergner ◽  
Heinz-Peter Schiffer
Keyword(s):  
Axial Compressor ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Stall Inception ◽  
Tip Clearance Flow ◽  
Transonic Compressor ◽  
Eddy Simulation ◽  
Clearance Flow ◽  
Flow Mechanisms ◽  
Tip Clearance Vortex

The current paper reports on investigations aimed at advancing the understanding of the flow mechanism that leads to the onset of short-length scale rotating stall in a transonic axial compressor. Experimental data show large oscillation of the tip clearance vortex as the rotor operates near the stall condition. Inception of spike-type rotating stall is also measured in the current transonic compressor with high response pressure transducers. Computational studies of a single passage and the full annulus were carried out to identify flow mechanisms behind the spike-type stall inception in the current transonic compressor rotor. Steady and unsteady single passage flow simulations were performed, first to get insight into the interaction between the tip clearance vortex and the passage shock. The conventional Reynolds-averaged Navier-Stokes method with a standard turbulence closure scheme does not accurately reproduce tip clearance vortex oscillation and the measured unsteady pressure field. Consequently, a Large Eddy Simulation (LES) was carried out to capture more relevant physics in the computational simulation of the rotating stall inception. The unsteady random behavior of the tip clearance vortex and it’s interaction with the passage shock seem to be critical ingredients in the development of spike-type rotating stall in a transonic compressor. The Large Eddy Simulation was further extended to the full annulus to identify flow mechanisms behind the measured spike-type rotating stall inception. The current study shows that the spike-type rotating stall develops after the passage shock is fully detached from the blade passages. Interaction between the tip clearance vortex and the passage shock creates a low momentum area near the pressure side of the blade. As the mass flow rate decreases, this low momentum area moves further upstream and reversed tip clearance flow is initiated at the trailing edge plane. Eventually, the low momentum area near the pressure side reaches the leading edge and forward spillage of the tip clearance flow occurs. The flows in the affected blade passage or passages then stall. As the stalled blade passages are formed behind the passage shock, the stalled area rotates counter to the blade rotation just like the classical Emmon’s type rotating stall. Both the measurements and the computations show that the rotating stall cell covers one to two blade passage lengths and rotates at roughly 50% of the rotor speed.

Detached-Eddy Simulation Applied to the Tip-Clearance Flow in a Last Stage Steam Turbine Blade

2018 ◽  
Author(s):  
Tianrui Sun ◽  
Paul Petrie-Repar ◽  
Damian M. Vogt
Keyword(s):  
Steam Turbine ◽  
Flow Structure ◽  
Complex Structure ◽  
Tip Clearance ◽  
Steam Turbines ◽  
Detached Eddy Simulation ◽  
Tip Clearance Flow ◽  
Eddy Simulation ◽  
Clearance Flow ◽  
Last Stage

Prediction of the aerodynamic stability of rotor blades at the last stage of steam turbines is of great importance and widely studied. Considering the large span and low natural frequency of these blades, flow at the tip region has a remarkable effect on blade flutter characteristics. However, the transonic tip-clearance flow in these blades has a complex structure of vortices. To obtain a deep understanding of the transonic tip-clearance flow structure in steam turbines, the Detached-Eddy Simulation (DES) is applied in this paper. DES is a hybrid LES/RANS method that activates LES in specified flow regions and applies URANS in other regions of the flow field. As far as we are aware, the tip-clearance flow structure of real-scale last stage steam turbine by high-fidelity numerical method had not been much analyzed in open literature. In this paper, the transonic tip-clearance flow structure in modern last stage of steam turbines is analyzed by both URANS and DES approaches. The open steam turbine model designed by Durham University is chosen as the research model. The flow solver applied is the commercial software ANSYS CFX. From the DES result, the tip leakage vortex and the induced vortices are presented. Based on the comparison between tip-clearance flow structure captured by the two approaches, the URANS method is not able to resolve all induced vortices. Therefore, the distribution of aerodynamic loading on the blade surface is different between URANS and DES results. The present study serves as a basis for investigating the influence of the tip-clearance flow structure on blade aeroelasticity.

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