Numerical simulation of local flow characteristic around spur dikes

2011 ◽  
Author(s):  
Jilun Miao ◽  
Chenglin Huang ◽  
Yongxiang Zhang
Keyword(s):  
Numerical Simulation ◽  
Flow Characteristic ◽  
Local Flow ◽  
Spur Dikes

scholarly journals Flow topologies in bubble-induced turbulence: a direct numerical simulation analysis

2018 ◽  
Vol 857 ◽  
pp. 270-290 ◽  
Author(s):  
Josef Hasslberger ◽  
Markus Klein ◽  
Nilanjan Chakraborty
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Turbulent Flows ◽  
Volume Fraction ◽  
Fluid Velocity ◽  
Small Scale ◽  
Flow Topology ◽  
Two Phase ◽  
Local Flow ◽  
Interface Curvature

This paper presents a detailed investigation of flow topologies in bubble-induced two-phase turbulence. Two freely moving and deforming air bubbles that have been suspended in liquid water under counterflow conditions have been considered for this analysis. The direct numerical simulation data considered here are based on the one-fluid formulation of the two-phase flow governing equations. To study the development of coherent structures, a local flow topology analysis is performed. Using the invariants of the velocity gradient tensor, all possible small-scale flow structures can be categorized into two nodal and two focal topologies for incompressible turbulent flows. The volume fraction of focal topologies in the gaseous phase is consistently higher than in the surrounding liquid phase. This observation has been argued to be linked to a strong vorticity production at the regions of simultaneous high fluid velocity and high interface curvature. Depending on the regime (steady/laminar or unsteady/turbulent), additional effects related to the density and viscosity jump at the interface influence the behaviour. The analysis also points to a specific term of the vorticity transport equation as being responsible for the induction of vortical motion at the interface. Besides the known mechanisms, this term, related to surface tension and gradients of interface curvature, represents another potential source of turbulence production that lends itself to further investigation.

scholarly journals Flow topologies in primary atomization of liquid jets: a direct numerical simulation analysis

2018 ◽  
Vol 859 ◽  
pp. 819-838 ◽  
Author(s):  
Josef Hasslberger ◽  
Sebastian Ketterl ◽  
Markus Klein ◽  
Nilanjan Chakraborty
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Direct Numerical Simulation ◽  
Incompressible Flows ◽  
Flow Structures ◽  
Liquid Jets ◽  
Small Scale ◽  
Flow Topology ◽  
Local Flow ◽  
Turbulent Length Scale

The local flow topology analysis of the primary atomization of liquid jets has been conducted using the invariants of the velocity-gradient tensor. All possible small-scale flow structures are categorized into two focal and two nodal topologies for incompressible flows in both liquid and gaseous phases. The underlying direct numerical simulation database was generated by the one-fluid formulation of the two-phase flow governing equations including a high-fidelity volume-of-fluid method for accurate interface propagation. The ratio of liquid-to-gas fluid properties corresponds to a diesel jet exhausting into air. Variation of the inflow-based Reynolds number as well as Weber number showed that both these non-dimensional numbers play a pivotal role in determining the nature of the jet break-up, but the flow topology behaviour appears to be dominated by the Reynolds number. Furthermore, the flow dynamics in the gaseous phase is generally less homogeneous than in the liquid phase because some flow regions resemble a laminar-to-turbulent transition state rather than fully developed turbulence. Two theoretical models are proposed to estimate the topology volume fractions and to describe the size distribution of the flow structures, respectively. In the latter case, a simple power law seems to be a reasonable approximation of the measured topology spectrum. According to that observation, only the integral turbulent length scale would be required as an input for the a priori prediction of the topology size spectrum.

Numerical simulation of gas-solid flow characteristic of particles in fibrous media using OpenFOAM

2019 ◽  
Vol 29 (7) ◽  
pp. 921-930 ◽  
Author(s):  
Zhiyong Shu ◽  
Fuping Qian ◽  
Jinjing Zhu ◽  
Jinli Lu
Keyword(s):  
Numerical Simulation ◽  
Flow Characteristic ◽  
Two Phase Flow ◽  
Dendritic Structure ◽  
Filtration Efficiency ◽  
Pressure Differential ◽  
Phase Flow ◽  
Fibrous Media ◽  
Two Phase ◽  
Solid Flow

Euler-Lagrangian numerical simulation framework of gas-solid two-phase flow was used to simulate the gas-solid flow characteristic in fibrous media using OpenFOAM in this study. The simulation results were compared with the empirical model and CFD-DEM method. In addition, the deposition morphology of particles, pressure differential and filtration efficiency in unsteady stage and simulation cost were also analysed with OpenFOAM. The results show that OpenFOAM can simulate the process of gas-solid two-phase flow in the fibrous media, and the particles are agglomerated on the surface of fibrous media and form a dendritic structure similar to the experimental observation. The pressure differential in unsteady stage would increase with the mass per unit area. The filtration efficiency would increase with a corresponding increase in the amount of deposition, but the growth rate would decline gradually. Compared with CFD-DEM method, the simulation accuracy with OpenFOAM is slightly lower, especially in the case of large the Stokes number, but the simulation cost is low, too. Therefore, it is necessary to choose one of the two methods according to the actual situation.

Numerical Simulation of Two-Phase Sloshing Flow in LNG Tank Using Finite-Analytic Level-Set Method

2007 ◽  
Author(s):  
Kai Yu ◽  
Hamn-Ching Chen ◽  
Jang Whan Kim ◽  
Young-Bum Lee
Keyword(s):  
Numerical Simulation ◽  
Wave Breaking ◽  
Impact Load ◽  
Three Dimensional ◽  
Impact Pressure ◽  
Staggered Grid ◽  
Two Phase ◽  
Local Flow ◽  
Hull Structure ◽  
Lng Tank

Impact pressure due to sloshing is of great concern for the ship owners, designers and builders of the LNG carriers regarding the safety of LNG containment system and hull structure. Sloshing of LNG in a partially filled tank has been an active area of research with numerous experimental and numerical investigations over the past decade. In order to accurately predict the sloshing impact load, it is necessary to develop advanced numerical simulation tools which can provide accurate resolution of local flow phenomena including wave breaking, jet formation, gas entrapping and liquid-gas interactions. In the present study, a new numerical method is developed for the simulation of violent sloshing flow inside a three-dimensional LNG tank considering wave breaking and liquid-gas interaction. The sloshing flow inside a membrane-type LNG tank is simulated numerically using the Finite-Analytic Navier-Stokes (FANS) method. The governing equations for two-phase air and water flows are formulated in curvilinear coordinate system and discretized using the finite-analytic method on a non-staggered grid. Simulations were performed for LNG tank in transverse and longitudinal motions including horizontal, vertical, and rotational motions. The predicted impact pressures were compared with the corresponding experimental data. The validation results clearly illustrate the capability of the present two-phase FANS method for accurate prediction of impact pressure in sloshing LNG tank including violent free surface motion, three-dimensional instability and air trapping effects.

Numerical Simulation of Flow Characteristic in Microchannel between Parallel Flat Plates

2013 ◽  
Vol 423-426 ◽  
pp. 1763-1767
Author(s):  
Yan Qiu Pan ◽  
Peng Lu ◽  
Lu Yu ◽  
Xin Min Han ◽  
Fa Quan Gong ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Flow Characteristic ◽  
Flat Plates

scholarly journals Improving the 2D Numerical Simulations on Local Scour Hole around Spur Dikes

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1462
Author(s):  
Chung-Ta Liao ◽  
Keh-Chia Yeh ◽  
Yin-Chi Lan ◽  
Ren-Kai Jhong ◽  
Yafei Jia
Keyword(s):  
Numerical Simulation ◽  
Three Dimensional ◽  
Local Scour ◽  
Bridge Piers ◽  
Scour Depth ◽  
Foundation Design ◽  
Mobile Bed ◽  
Scour Hole ◽  
Scour Holes ◽  
Spur Dikes

Local scour is a common threat to structures such as bridge piers, abutments, and dikes that are constructed on natural rivers. To reduce the risk of foundation failure, the understanding of local scour phenomenon around hydraulic structures is important. The well-predicted scour depth can be used as a reference for structural foundation design and river management. Numerical simulation is relatively efficient at studying these issues. Currently, two-dimensional (2D) mobile-bed models are widely used for river engineering. However, a common 2D model is inadequate for solving the three-dimensional (3D) flow field and local scour phenomenon because of the depth-averaged hypothesis. This causes the predicted scour depth to often be underestimated. In this study, a repose angle formula and bed geometry adjustment mechanism are integrated into a 2D mobile-bed model to improve the numerical simulation of local scour holes around structures. Comparison of the calculated and measured bed variation data reveals that a numerical model involving the improvement technique can predict the geometry of a local scour hole around spur dikes with reasonable accuracy and reliability.

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