Investigation of Free Surface Turbulence Damping in RANS Simulations for Complex Free Surface Flows

Kamath, Arun; Fleit, Gábor; Bihs, Hans

doi:10.3390/w11030456

Cited by 34 publications

(17 citation statements)

References 33 publications

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“…Standard two-phase RANS turbulence models do not account for this which can lead to increased ω and damped fluctuations normal to the surface due to a redistributed to parallel fluctuations. Additionally, standard RANS turbulence closure will incorrectly predict the maximum turbulence intensity at the free surface because the mean rate of strain S can be large especially in the vicinity of the interface between water and air [34]. A more realistic representation of the free surface effect on the turbulence can be achieved through the replacement of the original equation for ω in the vicinity of the surface by the empirical formula [34,35]:…”

Section: Reef3d::cfdmentioning

confidence: 99%

A Comparison of Different Wave Modelling Techniques in An Open-Source Hydrodynamic Framework

Wang¹,

Kamath²,

Pákozdi³

et al. 2020

JMSE

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Modern design for marine and coastal activities places increasing focus on numerical simulations. Several numerical wave models have been developed in the past few decades with various techniques and assumptions. Those numerical models have their own advantages and disadvantages. The proper choice of the most useful numerical tool depends on the understanding of the validity and limitations of each model. In the past years, REEF3D has been developed into an open-source hydrodynamic numerical toolbox that consists of several modules based on the Navier–Stokes equations, the shallow water equations and the fully nonlinear potential theory. All modules share a common numerical basis which consists of rectilinear grids with an immersed boundary method, high-order finite differences and high-performance computing capabilities. The numerical wave tank of REEF3D utilises a relaxation method to generate waves at the inlet and dissipate them at the numerical beach. In combination with the choice of the numerical grid and discretisation methods, high accuracy and stability can be achieved for the calculation of free surface wave propagation and transformation. The comparison among those models provide an objective overview of the different wave modelling techniques in terms of their numerical performance as well as validity. The performance of the different modules is validated and compared using several benchmark cases. They range from simple propagations of regular waves to three-dimensional wave breaking over a changing bathymetry. The diversity of the test cases help with an educated choice of wave models for different scenarios.

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Section: Reef3d::cfdmentioning

confidence: 99%

A Comparison of Different Wave Modelling Techniques in An Open-Source Hydrodynamic Framework

Wang¹,

Kamath²,

Pákozdi³

et al. 2020

JMSE

Self Cite

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“…With a gradual increase in the standoff distance (from 5 to 90 mm), the observed erosion regimes were observed in terms of micro-pitting action, crack and crater formation, and material folding and upheaving. Despite the research on solid-liquid two-phase flow erosion wear has made certain progress [34][35][36], experimental findings about the wear of hydraulic rotating machinery is limited, and the wear law caused by the rotation of solid components (such as turbine runner) needs further study. Therefore, this paper seeks to explain the development of the erosion and wear of rotating parts in the context of the physical properties of the particles.…”

Section: Introductionmentioning

confidence: 99%

Multicomponent Water Effects on Rotating Machines Disk Erosion

Yang

Hou

et al. 2020

Water

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When sand particles are entrained into carrier flow, such as liquid, a strong interaction occurs with the surface of the metallic material, resulting in serious erosion damage. However, the effect of the physical properties of particles and materials on erosion characteristics has not been well studied. In this paper, the erosion-wear behavior of a rotating disc surface under the action of solid–liquid two-phase flow was studied by using the discrete particle model (DPM). The wear effects on the surface of sample due to particle diameter (d = 0.1 mm, d = 0.2 mm, d = 0.3 mm, d = 0.4 mm), particle volume fraction (CV = 2%, CV = 3%, CV = 4%, CV = 5%), and particle inlet velocity (v = 1.05 m/s, v = 2.05 m/s, v = 3.05 m/s, v = 4.05 m/s) were analyzed using representative values of operating conditions of rotating machines. The results show that the wear amount increases exponentially with the radius, whilst the maximum wear amount increases faster than the average wear amount with the particle volume fraction. The surface wear grows inversely with the particle diameter but slightly with the particle inlet velocity. A case study of stainless steel samples at different radius positions on the surface of rotating disc is carried out using a mixed velocity of sand and water of 2.05 m/s, an average particle size of 0.1 mm, and a concentration of CV = 2.5%. The experiments show the wear amount increases with the radius on the surface of the rotating disc, just as predicted by the numerical simulation. Two important findings emerge from the study: (1) the wear morphology of the specimen surface develops from two to three regions; (2) when the basal body is rotating at high speed, the wear degree is influenced more by the circumferential than particle inlet velocity. The wear morphology was observed by using a scanning electron microscope (SEM). It exhibited a mixture of fine and coarse scratches and pits, and the distribution of these varied according to the radial distance of the disc.

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“…In case of the LSM, the interface is explicitly defined by using a signed level set function in every computational node, defining the closest distance from the free surface. The LSM based CFD toolbox REEF3D [19] has been successfully used to simulate complex flows around various hydraulic engineering structures [20,21].…”

Section: Introductionmentioning

confidence: 99%

“…In spite of the encouraging results of the above mentioned studies, a major problem with standard RANS turbulence models is that in two-phase simulations, the effect of the free surface is neglected and high turbulence production occurs due to the high gradient in fluid density. Kamath et al [21] investigated free surface turbulence damping in several different case studies to validate the applicability of their apparatus. They used RANS equations with k-ω turbulence closure and LSM for capturing free surface.…”

Section: Introductionmentioning

confidence: 99%

Assessment of CFD Model Performance for Flows around a Hydraulic Structure of Complex Geometry

Grivalszki

Fleit

Baranya

et al. 2020

Period. Polytech. Civil Eng.

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Computational Fluid Dynamics (CFD) modeling has become a widely used research tool in the hydraulic engineering community, however, for many problems the numerical model setup and even the selection of the suitable hydrodynamic solver is still a challenging task. This is the case for fine scale analysis of flow features around hydraulic structures of complex geometry, where generation of the 3D grid, application of the correct turbulence modeling approach, or modeling of the free surface all require extensive experience and knowledge. The aim of this paper is to perform a numerical hydrodynamic experiment for a hydraulic structure with complex geometry to assess the model performance, in terms of grid resolution, grid refinement methods as well as turbulence modeling. The open source modeling environment of OpenFOAM is tested and validated against laboratory measurements, moreover, practical recommendations are made for future applications of the numerical solver.

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Investigation of Free Surface Turbulence Damping in RANS Simulations for Complex Free Surface Flows

Cited by 34 publications

References 33 publications

A Comparison of Different Wave Modelling Techniques in An Open-Source Hydrodynamic Framework

A Comparison of Different Wave Modelling Techniques in An Open-Source Hydrodynamic Framework

Multicomponent Water Effects on Rotating Machines Disk Erosion

Assessment of CFD Model Performance for Flows around a Hydraulic Structure of Complex Geometry

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