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.

Large‐Eddy Simulation of Three‐Dimensional Flow Structures Over Wave‐generated Ripples

2021 ◽  
Author(s):  
Chuang Jin ◽  
Giovanni Coco ◽  
Rafael O. Tinoco ◽  
Pallav Ranjan ◽  
Jorge San Juan ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Three Dimensional ◽  
Flow Structures ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Eddy Simulation ◽  
Large Eddy

Large Eddy Simulation of the Flow Around a Diffuser-Equipped Bluff Body in Ground Effect

2011 ◽  
Author(s):  
Lara Schembri Puglisevich ◽  
Gary Page
Keyword(s):  
Large Eddy Simulation ◽  
Bluff Body ◽  
Vortex Formation ◽  
Ground Effect ◽  
Vortical Flow ◽  
Navier Stokes ◽  
Flow Structures ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Flow Features

Unsteady Large Eddy Simulation (LES) is carried out for the flow around a bluff body equipped with an underbody rear diffuser in close proximity to the ground, representing an automotive diffuser. The goal is to demonstrate the ability of LES to model underbody vortical flow features at experimental Reynolds numbers (1.01 × 106 based on model height and incoming velocity). The scope of the time-dependent simulations is not to improve on Reynolds-Averaged Navier Stokes (RANS), but to give further insight into vortex formation and progression, allowing better understanding of the flow, hence allowing more control. Vortical flow structures in the diffuser region, along the sides and top surface of the bluff body are successfully modelled. Differences between instantaneous and time-averaged flow structures are presented and explained. Comparisons to pressure measurements from wind tunnel experiments on an identical bluff body model shows a good level of agreement.

Large eddy simulation modelling of asymmetrical flow structures in a vertical-bending continuous caster

2019 ◽  
Vol 116 (6) ◽  
pp. 636
Author(s):  
Peng Zhao ◽  
Yinhe Lin ◽  
Bin Yang ◽  
Kegao Liu ◽  
Jingrui Zhao ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Large Eddy Simulation ◽  
Casting Speed ◽  
Oscillation Frequency ◽  
Continuous Caster ◽  
Water Model ◽  
Flow Structures ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Coherent Vortices

Transient asymmetric circulations in the vertical-bending section of a continuous caster were simulated using a large eddy simulation (LES) model. The accuracy of the modelling was verified by comparing the jet behaviours, asymmetrical flow structures in the water model, and velocities reported in the literature. Coherent structures play an essential role in the circulations motion in the vertical-bending caster. A classical Q-criterion was introduced to detect and identify coherent vortices to investigate flow structures. The results indicate that coherent vortices in the lower circulation exhibit asymmetrical features, which further reveal the nature of the turbulence behind the flow structures in the caster. Monitoring points were then selected to investigate the motions of the “strong” and “weak” circulatory vortices and corresponding velocity variations at the interface between the vertical and bending section of the caster. The alternative variations show the periodic behaviours of asymmetrical circulations at both sides of the vertical-bending caster. Besides these circulations were interrelated and interacted, they were also affected by the curved section of the caster, which resulted in the asymmetrical flow structures in the vertical-bending caster. Finally, the effects of casting speed and SEN immersion depths on the oscillation frequency of circulations during a continuous casting process were analysed. As the casting speed increased, the oscillation frequency and power spectrum increased accordingly; as the SEN immersion depth increased, the oscillation frequency and power spectrum thereof decreased accordingly.

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