Numerical Simulation of Cavity Shedding from a Three-Dimensional Twisted Hydrofoil and Induced Pressure Fluctuation by Large-Eddy Simulation

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Xianwu Luo ◽  
Bin Ji ◽  
Xiaoxing Peng ◽  
Hongyuan Xu ◽  
Michihiro Nishi
Keyword(s):  
Large Eddy Simulation ◽  
Pressure Fluctuation ◽  
Three Dimensional ◽  
Cavitating Flow ◽  
Numerical Results ◽  
Central Plane ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Cavity Shedding ◽  
Twisted Hydrofoil

Simulation of cavity shedding around a three-dimensional twisted hydrofoil has been conducted by large eddy simulation coupling with a mass transfer cavitation model based on the Rayleigh-Plesset equation. From comparison of the numerical results with experimental observations, e.g., cavity shedding evolution, it is validated that the unsteady cavitating flow around a twisted hydrofoil is reasonably simulated by the proposed method. Numerical results clearly reproduce the cavity shedding process, such as cavity development, breaking-off and collapsing in the downstream. Regarding vapor shedding in the cavitating flow around three-dimensional foils, it is primarily attributed to the effect of the re-entrant flow consisting of a re-entrant jet and a pair of side-entrant jets. Formation of the re-entrant jet in the rear part of an attached cavity is affected by collapse of the last shedding vapor. Numerical results also show that the cavity shedding causes the surface pressure fluctuation of the hydrofoil and the force vibration. Accompanying the cavity evolution, the wave of pressure fluctuation propagates in two directions, namely, from the leading edge of the foil to the trailing edge and from the central plane to the side of the hydrofoil along the span. It is seen that the large pressure fluctuation occurs at the central part of the hydrofoil, where the flow incidence is larger.

Large eddy simulation of turbulent cavitating flow in a Venturi-type section with special emphasis on LES errors and pressure fluctuation analyses

2021 ◽  
Vol 35 (26) ◽  
pp. 2150440
Author(s):  
Linfeng Deng ◽  
Yun Long ◽  
Bin Ji ◽  
Xinping Long
Keyword(s):  
Large Eddy Simulation ◽  
Pressure Fluctuation ◽  
Cavitating Flow ◽  
Numerical Results ◽  
Fluctuation Analysis ◽  
Simulation Accuracy ◽  
Modified Model ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Relationship

In this study, large eddy simulation (LES) coupled with the homogeneous cavitation model is used to simulate the turbulent cavitating flow in the venturi with special emphasis on LES errors and pressure fluctuation analysis. The numerical results accurately predict the quasi-periodic behavior and frequency characteristics of the cavitation by comparing them with the experimental observations. The modified one-dimensional model is utilized here to figure out the relationship between cavitation and pressure fluctuation. A good coincidence between the predicted and monitored pressure is obtained to validate the consideration of the geometric and flow factors in the modified model. Further analysis indicated that the cavity volume acceleration is the main source of cavitation excited pressure fluctuation. Moreover, LES Verification and Validation (V&V) are involved to quantify the errors and uncertainties of the numerical results. It is found that the large magnitude of the errors often emerges in the region where the re-entrant jet and shedding cavity occurs, which demonstrates the influence of cavitation on the simulation accuracy. The modeling error has a larger magnitude than the numerical error and both often show opposite signs. To better understand the influence of cavitation on LES V&V, the interaction between cavitation and vortex is also discussed further.

scholarly journals Prediction of a methane circular pool fire with fireFoam

2018 ◽  
Vol 240 ◽  
pp. 05026
Author(s):  
Camilo Sedano ◽  
Omar López ◽  
Alexander Ladino ◽  
Felipe Muñoz
Keyword(s):  
Large Eddy Simulation ◽  
Convergence Analysis ◽  
Three Dimensional ◽  
Numerical Results ◽  
Pool Fire ◽  
Medium Scale ◽  
Eddy Simulation ◽  
Large Eddy

In the present work, the fireFoam solver was used with Large Eddy Simulation (LES) and the Eddy Dissipation Concept (EDC) for modelling a medium-scale methane pool fire. A convergence analysis performed, showed that a 2 Million elements three-dimensional mesh, is good enough to attain good numerical results. By comparing the numerical results obtained, with the experimental ones, as well as numerical results from previous studies, it was proven that the fireFoam solver is able to obtain satisfactory results.

scholarly journals Cloud Cavitating Flow Over a Submerged Axisymmetric Projectile and Comparison Between Two-Dimensional RANS and Three-Dimensional Large-Eddy Simulation Methods

2016 ◽  
Vol 138 (6) ◽  
Author(s):  
Yiwei Wang ◽  
Chenguang Huang ◽  
Xin Fang ◽  
Xianian Yu ◽  
Xiaocui Wu ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Cavitating Flow ◽  
Two Dimensional ◽  
Cloud Cavitation ◽  
Cavity Collapse ◽  
Eddy Simulation ◽  
2D Simulation ◽  
Large Eddy

For the cloud cavitation around slender axisymmetric projectiles, a two-dimensional (2D) numerical method was based on the mixture approach with Singhal cavitation model and modified renormalization-group (RNG) k–ε turbulence model, and a three-dimensional (3D) method was established with large-eddy simulation (LES) and volume of fraction (VOF) approach. The commercial computational fluid dynamic (CFD) software fluent is used for the 2D simulation, and the open source code OpenFOAM is adopted for the 3D calculation. Experimental and numerical results were presented on a typical case, in which the projectile moves with a quasi-constant axial speed. Simulation results agree well with experimental results. An analysis of the evolution of cavitating flow was performed, and the related physical mechanism was discussed. Results demonstrate that shedding cavity collapse plays an important role in the generation and acceleration of re-entry jet, which is the main reason for the instability of cloud cavitation. The 2D Reynolds-Averaged Navier–Stokes (RANS) method can represent the physical phenomena effectively. The 3D LES method can give an efficient simulation on the shedding vortices, and considerable accurate shapes of shedding cavities are captured.

scholarly journals Large Eddy Simulation of Periodic Transient Pressure Fluctuation in a Centrifugal Pump Impeller at Low Flow Rate

Symmetry ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 311
Author(s):  
Renfei Kuang ◽  
Xiaoping Chen ◽  
Zhiming Zhang ◽  
Zuchao Zhu ◽  
Yu Li
Keyword(s):  
Large Eddy Simulation ◽  
Centrifugal Pump ◽  
Flow Rate ◽  
Pressure Fluctuation ◽  
Low Frequency ◽  
Pump Impeller ◽  
Eddy Simulation ◽  
Inlet Flow Rate ◽  
Large Eddy ◽  
Centrifugal Pump Impeller

This paper presents a large eddy simulation of a centrifugal pump impeller during a transient condition. The flow rate is sinusoidal and oscillates between 0.25Qd (Qd indicates design load) and 0.75Qd when the rotating speed is maintained. Research shows that in one period, the inlet flow rate will twice reach 0.5Qd, and among the impeller of one moment is a stall state, but the other is a non-stall state. In the process of flow development, the evolution of low-frequency pressure fluctuation shows an obviously sinusoidal form, whose frequency is insensitive to the monitoring position and equals to that of the flow rate. However, inside the impeller, the phase and amplitude in the stall passages lag behind more and are stronger than that in the non-stall passages. Meanwhile, the strongest region of the high-frequency pressure fluctuation appears in the stall passages at the transient rising stage. The second dominant frequency in stall passages is 2.5 times to that in non-stall passages. In addition, similar to the pressure fluctuation, the evolution of the low-frequency head shows a sinusoidal form, whose phase is lagging behind that by one-third of a period in the inlet flow rate.

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