Surface Flow Interaction Research Articles

Nonhydrostatic model for free surface flow interaction with structures

AbstractSimulating fluid–structure interactions is important in many engineering applications. Navier–Stokes based models can accurately simulate free surface flows and efficiency is improved by transforming the equations into the sigma‐coordinate system in which the grid follows the free surface and bottom. This approach lacks the ability to simulate wave overturning and splashing, but it has been demonstrated to accurately simulate breaking waves. Incorporating structures in a free surface flow model is challenging. Many existing techniques require complex grids and cumbersome interpolation. The immersed boundary method avoids complicated grids by overlaying the object on the grid. Interpolation is still required at the object boundary, which may not conserve mass. It is also difficult to compute the force acting on the body. Conservation may be reclaimed by embedding the object into the mesh. However, this may result in small (cut) cells and numerical instability unless they are merged with neighboring cells. In this article, a new model is proposed and constructed using a modified sigma coordinate transformation. This limits the model to simulating objects that can be represented by upper and lower surfaces that are functions of x and y, but still allows for many simulations of engineering interest. In exchange for this compromise, several advantages are gained including: efficiency, mass conservation, and easy estimation of force. Model accuracy is demonstrated by comparing numerical predictions with analytical solutions and laboratory measurements for free surface flows interacting with a horizontal cylinder and NACA 0012 foil.

A dynamic bidirectional coupled surface flow model for flood inundation simulation

Abstract. Flood disasters frequently threaten people and property all over the world. Therefore, an effective numerical model is required to predict the impacts of floods. In this study, a dynamic bidirectional coupled hydrologic–hydrodynamic model (DBCM) is developed with the implementation of characteristic wave theory, in which the boundary between these two models can dynamically adapt according to local flow conditions. The proposed model accounts for both mass and momentum transfer on the coupling boundary and was validated via several benchmark tests. The results show that the DBCM can effectively reproduce the process of flood propagation and also account for surface flow interaction between non-inundation and inundation regions. The DBCM was implemented for the floods simulation that occurred at Helin Town located in Chongqing, China, which shows the capability of the model for flood risk early warning and future management.

Volumetric flow characterisation of a rectangular orifice impinging synthetic jet with single-camera light-field PIV

The formation and evolution of volumetric flow structures from a rectangular orifice synthetic jet (AR=10, Re=550, Sr=0.0117, and Lo=0.0855m) impinging on a flat plate is investigated using phase-locked single-camera light-field particle image velocimetry (LF-PIV). An impinging plate is located 24 orifice widths away from the rectangle orifice and this volumetric flow data is used to capture the mechanisms involved in the interaction. Flow statistics and structure information obtained by time-averaging and phase-averaging the volumetric data reveal the formation and evolution of three-dimensional vortical structures and sweeping vortex that characterise the flow-surface interaction.

벽면의 형상 변화에 의한 난류 드래그 관련 Pocket Length Scale 저감연구

The flow-surface interaction and resulting pockets is the case of a turbulence boundary layer. Conditionally sampled hot-wire measurements within the wall region show that a strong vortex forms within the pocket, bordering the upstream portion, which stay in the wall region. This vortex is the result of the rearrangement of existing sublayer vorticity and its amplification. The work in this area has been applied to the prediction and reduction of drag. The study is focused on determining change in the length scale of the pockets. An important relationship between pocket and modified wall has been found. By changing the upstream boundary condition at the wall, the length scale of pockets were decreased.

Tillage Condition Effects on Soil/Plow-breast Flow Interaction of a Horizontally Reversible Plow

The horizontally reversible plow (HRP) is commonly utilized because of higher performances than the regular mold-board plow. Soil/plow surface flow interaction during HRP tillage trends to incur so severe pressure on the plow-breast as to reduce the plow life. This paper numerically characterized the soil/plow-breast flow interaction and subsequently assessed tillage-condition effects on the plow-breast surface. These tillage conditions herein involved tool speed and operation-al depth. The simulations showed that for either tool speed or operational depth the maximum pressure appeared at the plow-shank of the plow-breast and that the soil pressures were increased with them. The computational fluid dynamics (CFD) based predictions qualitatively agreed with the preliminary experimental results at the identified settings with scanning electronic microscopy. Once again, CFD analysis is demonstrated to be feasible and effective enough to provide insight into improve the horizontally reversible plow by predicting real soil behaviors.

Assessment of High-Velocity Free Surface Flow Interaction with a Bridge Pier in A Curved Channel

Assessment of High-Velocity Free Surface Flow Interaction with a Bridge Pier in A Curved Channel

Violent transient sloshing-wave interaction with a baffle in a three-dimensional numerical tank

A finite difference model for solving Navier Stokes equations with turbulence taken into account is used to investigate viscous liquid sloshing-wave interaction with baffles in a tank. The volume-of-fluid and virtual boundary force methods are employed to simulate free surface flow interaction with structures. A liquid sloshing experimental apparatus was established to evaluate the accuracy of the proposed model, as well as to study nonlinear sloshing in a prismatic tank with the baffles. Damping effects of sloshing in a rectangular tank with bottom-mounted vertical baffles and vertical baffles touching the free surface are studied numerically and experimentally. Good agreement is obtained between the present numerical results and experimental data. The numerical results match well with the current experimental data for strong nonlinear sloshing with large free surface slopes. The reduction in sloshing-wave elevation and impact pressure induced by the bottom-mounted vertical baffle and the vertical baffle touching the free surface is estimated by varying the external excitation frequency and the location and height of the vertical baffle under horizontal excitation.

Analysis of High Velocity Free Surface Flow Interaction with a Bridge Pier in a Trapezoidal Channel using CFD

This study uses the computational fluid dynamics (CFD) code ANSYS-CFX-12, to simulate 3D flow through a straight trapezoidal cross section channel containing a single bridge pier. The fluid flow condition is assumed to be steady state, isothermal and incompressible, with symmetry along the centerline of the channel, and the simulation uses the k - ε turbulence model. The study investigates the impact of variations of aspect ratio (channel bed width/flow depth), bed and side slopes of the channel, discharge (represented by a Froude number), and the length and thickness of the bridge pier on the free surface flow profile, both along the centerline and the on the wall of the channel. The code is based on the finite volume method, and uses the volume of fluid (VOF) approach to predict the free surface flow profile. Prediction of the free surface flow profile is essential for the design of high velocity channels. Prior prediction of flow profiles can inform and improve the design of expensive structures, such as high velocity channels and bridges, in particular the height of channel walls and bridge decks. Firstly, the code was validated against the numerical and experimental work of Stockstill (1996) for a channel containing three piers, and found to agree well. Then, the method was applied to the design test case, and mesh convergence tests to establish the required mesh size were carried out. The simulations were conducted in parallel over 32 cores on the Plymouth University High Performance Computer Cluster (HPCC). Finally, a parametric study was carried out and analytical expressions derived for maximum flow depth at the centre-line and at the side wall of the channel. Useful non-dimensional curves and equations derived from regressions of the study data are provided, which can be used as a guideline for the design of high velocity channels containing a bridge pier. For data regressions the statistical package software Statistical Product and Service Solutions (SPSS) was used.

Numerical study on the pressure drop of fluid flow in rough microchannels via the lattice Boltzmann method

Purpose – The purpose of this paper is to provide a quantitative assessment on the effect of wall roughness on the pressure drop of fluid flow in microchannels. Design/methodology/approach – The wall roughness is generated by the method of random midpoint displacement (RMD) and the lattice Boltzmann BGK model is applied. The influences of Reynolds number, relative roughness and the Hurst exponent of roughness profile on the Poiseuille number are investigated. Findings – Unlike the smooth channel flow, Reynolds number, relative roughness and the Hurst exponent of roughness profiles play critical roles on the Poiseuille number Po in rough microchannels. Modeling results indicate that, in rough microchannels, the rough surface configuration intensifies the flow-surface interactions and the wall conditions turn to dominate the flow characteristics. The perturbance of the local flows near the channel wall and the formation of recirculation regions are two main features of the flow-surface interactions. Research limitations/implications – The fluid flow in parallel planes with surface roughness is considered in the current study. In other words, only two-dimensional fluid flow is investigated. Practical implications – The LBM is a very useful tool to investigate the microscale flows. Originality/value – A new method (RMD) is applied to generate the wall roughness in parallel plane and LBM is conducted to investigate the pressure drop characteristics in rough microchannels.

An improved incompressible SPH model for simulation of wave–structure interaction

An improved two-dimensional Incompressible Smoothed Particle Hydrodynamics (ISPH) model is developed to simulate free surface flow interaction with structures. In this model, the improved mirror particle treatment for solid boundaries is developed, in which the mirror parameters and mirroring rules are redefined. The proposed mirror particle treatment is more accurate with less artificial oscillations of pressure. The improvement of pressure computations is verified by a benchmark test of dam break flow and the comparisons with the documented data showed satisfactory agreement. A series of numerical simulations have been conducted to further verify the applicability of the model for simulations of wave interaction with coastal structures of various shapes. These include linear wave reflection from an impermeable breakwater, solitary wave passing a rectangular obstacle and periodic wave train decompositions over a submerged shelf. In these simulations, the total particle number employed is up to 150,000 and rather good agreement has been obtained when the numerical results are compared to available analytical, experimental, and other numerical data found in literatures.

A coupled FDM–FEM method for free surface flow interaction with thin elastic plate

A partitioned approach by the coupling finite difference method (FDM) and the finite element method (FEM) is developed for simulating the interaction between free surface flow and a thin elastic plate. The FDM, in which the constraint interpolation profile method is applied, is used for solving the flow field in a regular fixed Cartesian grid, and the tangent of the hyperbola for interface capturing with the slope weighting scheme is used for capturing free surface. The FEM is used for solving structural deformation of the thin plate. A conservative momentum-exchange method, based on the immersed boundary method, is adopted to couple the FDM and the FEM. Background grid resolution of the thin plate in a regular fixed Cartesian grid is important to the computational accuracy by using this method. A virtual structure method is proposed to improve the background grid resolution of the thin plate. Both of the flow solver and the structural solver are carefully tested and extensive validations of the coupled FDM–FEM method are carried out on a benchmark experiment, a rolling tank sloshing with a thin elastic plate.

PRODUCTION OF SOUND BY UNSTEADY THROTTLING OF FLOW INTO A RESONANT CAVITY, WITH APPLICATION TO VOICED SPEECH.

An analysis is made of the sound generated by the time-dependent throttling of a nominally steady stream of air through a small orifice into a flow-through resonant cavity. This is exemplified by the production of voiced speech, where air from the lungs enters the vocal tract through the glottis at a time variable volume flow rate Q(t) controlled by oscillations of the glottis cross-section. Voicing theory has hitherto determined Q from a heuristic, reduced complexity 'Fant' differential equation (G. Fant, Acoustic Theory of Speech Production, 1960). A new self-consistent, integro-differential form of this equation is derived in this paper using the theory of aerodynamic sound, with full account taken of the back-reaction of the resonant tract on the glottal flux Q. The theory involves an aeroacoustic Green's function (G) for flow-surface interactions in a time-dependent glottis, so making the problem non-self-adjoint. In complex problems of this type it is not usually possible to obtain G in an explicit analytic form. The principal objective of the paper is to show how the Fant equation can still be derived in such cases from a consideration of the equation of aerodynamic sound and from the adjoint of the equation governing G in the neighbourhood of the 'throttle'. The theory is illustrated by application to the canonical problem of throttled flow into a Helmholtz resonator.

Towards a numerical hydrodynamics laboratory by developing an overlapping mesh solver based on a moving mesh solver; verification and application

Simple extension of an available finite volume moving mesh algorithm to an overlapping mesh solver is discussed. The resultant solver can then overcome difficulties with relative/large motions as well as mesh generation in comparison to those when using a moving mesh. However, it handles hydrodynamic problems including viscous free surface flow interaction with a free rigid body. Changes arise from using more than a mesh in the computational domain by an overlapping mesh system which accompanies data transfer and solving discrete sets of equations. By developing a two-dimensional code, different aspects of the proposed solver have been discussed by simulating a cavity flow, an unsymmetrical current around a cylinder in a channel, wave generation using an analytical solution and a wedge-type wavemaker and finally, free falling of a cylinder into calm water. Comparison of results to available data shows the capabilities of the solver in spite of its simplicity, as well.

A finite volume algorithm based on overlapping meshes for simulation of hydrodynamic problems

A finite volume algorithm was established in order to investigate two-dimensional hydrodynamic problems. These include viscous free surface flow interaction with free rigid bodies in the case of large and/or relative motions. Two-phase flow with complex deformations at the interface was simulated using a fractional step-volume of fluid algorithm. In addition, body motions were captured by an overlapping mesh system. Here, flow variables are transferred using a simple fully implicit non-conservative interpolation scheme which maintains the second-order accuracy of implemented spatial discretisation. Code was developed and an appropriate set of problems investigated. Results show good potential for development of a virtual hydrodynamics laboratory.

Application of Overlapping Mesh in Numerical Hydrodynamics

Application of Overlapping Mesh in Numerical Hydrodynamics A Finite Volume (FV) algorithm is presented to investigate two-dimensional hydrodynamic problems including viscous free surface flow interaction with free rigid bodies in the case of large and/or relative motions. Two-phase flow with complex deformations at the interface is simulated using a fractional stepvolume of fluid algorithm while it is also capable of representing a high quality wave tank, according to implemented temporal discretisation. Rigid body motions are also captured using two overset meshes. Flow variables are transferred using a simple fully implicit non-conservative interpolation scheme which maintains the second-order accuracy of implemented spatial discretisation. A code is developed and an appropriate set of problems are investigated. Results show a good potential to develop a virtual hydrodynamics laboratory.

Further comments on the equilibrium height of neutral and stable planetary boundary layers

AbstractThe height of the neutrally and stably stratified turbulent planetary boundary layers (PBLs) in the atmosphere and hydrosphere is controlled by numerous factors of different natures. The PBL deepening is facilitated by turbulent mixing caused, first of all, by the velocity shear at the surface, and prevented by the Earth's rotation and the negative buoyancy forces caused by the flow–surface interaction and the stable static stability in the free atmosphere above the PBL. The balance between these factors is often complicated by the baroclinic shears and large‐scale vertical motions (usually disregarded in field experiments), not to mention temporal and horizontal variability of natural PBL flow. It is not surprising that until now many alternative (sometimes contradictory) formulations for the stable PBL height have been proposed and no consensus achieved. To the authors' opinion, the most natural way to investigate this complex problem is to consider step by step the PBL height in comparatively simple, basic equilibrium regimes (controlled by limited factors), to develop and to validate theoretical models for these regimes, and only afterwards to switch to general diagnostic (equilibrium) and prognostic (non‐steady) equations. In the present paper, we briefly summarize recent investigations following the above strategy, and present new data supporting our earlier theoretical conclusions and recommendations. We would not recommend using PBL height equations inconsistent with firmly established basic‐regime formulations. Copyright © 2007 Royal Meteorological Society

Numerical treatment of free surface problems in ferrohydrodynamics

The numerical treatment of free surface problems in ferrohydrodynamics is considered.Starting from the general model, special attention is paid to field–surface and flow–surfaceinteractions. Since in some situations these feedback interactions can be partly or even fullyneglected, simpler models can be derived. The application of such models to the numericalsimulation of dissipative systems, rotary shaft seals, equilibrium shapes of ferrofluid drops,and pattern formation in the normal-field instability of ferrofluid layers is given. Ournumerical strategy is able to recover solitary surface patterns which were discoveredrecently in experiments.

A fixed-grid model for simulation of a moving body in free surface flows

A two-dimensional computer model is developed to simulate free surface flow interaction with a moving body. The model is based on the cut-cell technique in a fixed-grid system. In this model, a body is approximated by the partial cell treatment (PCT), in which an irregular body is represented by the volumetric fraction of solid in Cartesian cells. The body motion is tracked by Lagrangian method whereas the fluid motion around the body is solved by Eulerian method. The concept of “locally relative stationary (LRS)” is introduced in this study. In the LRS method, a source term is added locally to the conventional continuity equation on body surfaces to take account of body motions, which subsequently affects the computational results of fluid pressure and flow velocity around the body. The LRS method is incorporated into an earlier Reynolds averaged Navier–Stokes (RANS) equations model developed by Lin and Liu [A numerical study of breaking waves in the surf zone. J Fluid Mech 1998;359:239–64]. The new model is capable of simulating generic turbulent free surface flows and their interaction with a moving body or multiple moving bodies. A series of numerical experiments have been conducted to verify the accuracy of the model for simulation of moving body interaction with a free surface flow. These tests include the generation of a solitary wave with the prescribed wave paddle movements, water exit and water impact and entry of a horizontal circular cylinder, fluid sloshing in a horizontally excited tank, and the acceleration/deceleration of an elliptical cylinder near a water surface. Excellent agreements are obtained when numerical results are compared to available analytical, experimental, and other numerical results. The model is a simple-to-implement computational tool for simulating a moving body in turbulent free surface flows.

A mixed finite–element finite–difference method for nonlinear fluid–structure interaction dynamics. I. Fluid–rigid structure interaction

Restricted accessMoreSectionsView PDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmail Cite this article Xing J. T., Price W. G. and Chen Y. G. 2003A mixed finite–element finite–difference method for nonlinear fluid–structure interaction dynamics. I. Fluid–rigid structure interactionProc. R. Soc. Lond. A.4592399–2430http://doi.org/10.1098/rspa.2002.1110SectionRestricted accessA mixed finite–element finite–difference method for nonlinear fluid–structure interaction dynamics. I. Fluid–rigid structure interaction J. T. Xing J. T. Xing Ship Science, School of Engineering Sciences, University of Southampton, Highfield, Southampton SO17 1BJ, UK Google Scholar Find this author on PubMed Search for more papers by this author , W. G. Price W. G. Price Ship Science, School of Engineering Sciences, University of Southampton, Highfield, Southampton SO17 1BJ, UK Google Scholar Find this author on PubMed Search for more papers by this author and Y. G. Chen Y. G. Chen Ship Science, School of Engineering Sciences, University of Southampton, Highfield, Southampton SO17 1BJ, UK Google Scholar Find this author on PubMed Search for more papers by this author J. T. Xing J. T. Xing Ship Science, School of Engineering Sciences, University of Southampton, Highfield, Southampton SO17 1BJ, UK Google Scholar Find this author on PubMed Search for more papers by this author , W. G. Price W. G. Price Ship Science, School of Engineering Sciences, University of Southampton, Highfield, Southampton SO17 1BJ, UK Google Scholar Find this author on PubMed Search for more papers by this author and Y. G. Chen Y. G. Chen Ship Science, School of Engineering Sciences, University of Southampton, Highfield, Southampton SO17 1BJ, UK Google Scholar Find this author on PubMed Search for more papers by this author Published:08 October 2003https://doi.org/10.1098/rspa.2002.1110AbstractA mixed finite–element finite–difference numerical method is developed to calculate nonlinear fluid–solid interaction problems. In this study, the structure is assumed to be rigid with large motion and the fluid flow is governed by nonlinear, viscous or non–viscous, field equations with nonlinear boundary conditions applied to the free surface and fluid–solid interaction interfaces. A moving coordinate system fixed at a point in the structure is used to describe the fluid flow, and for numerical analysis purposes, an arbitrary Lagrangian–Eulerian mesh system is constructed relative to this moving system. This provides a convenient method of overcoming the difficulties of matching fluid meshes with large solid motion. Nonlinear numerical equations describing nonlinear fluid–solid interaction dynamics are derived through a numerical discretization scheme of study. A coupling iteration process is used to solve these numerical equations. A selection of numerical examples illustrates the developed mathematical model and through numerical simulations it is shown that the proposed approach is practical and useful. Previous ArticleNext Article VIEW FULL TEXT DOWNLOAD PDF FiguresRelatedReferencesDetailsCited by (2019) Bibliography Fluid-Solid Interaction Dynamics, 10.1016/B978-0-12-819352-5.00029-X, (627-649), . Abou-Dina M and Ghaleb A (2016) Multiple wave scattering by submerged obstacles in an infinite channel of finite depth. I. Streamlines, European Journal of Mechanics - B/Fluids, 10.1016/j.euromechflu.2016.04.005, 59, (37-51), Online publication date: 1-Sep-2016. Wei K and Yuan W (2013) Seismic Analysis of Deep Water Pile Foundation Based on Three-Dimensional Potential-Based Fluid Elements, Journal of Construction Engineering, 10.1155/2013/874180, 2013, (1-10), Online publication date: 11-Apr-2013. Liao K and Hu C (2012) A coupled FDM–FEM method for free surface flow interaction with thin elastic plate, Journal of Marine Science and Technology, 10.1007/s00773-012-0191-0, 18:1, (1-11), Online publication date: 1-Mar-2013. Li Y, Li Z and Wu Q (2017) Experiment and Calculation Method of the Dynamic Response of Deep Water Bridge in Earthquake, Latin American Journal of Solids and Structures, 10.1590/1679-78253872, 14:13, (2518-2533) This Issue08 October 2003Volume 459Issue 2038 Article InformationDOI:https://doi.org/10.1098/rspa.2002.1110Published by:Royal SocietyPrint ISSN:1364-5021Online ISSN:1471-2946History: Published online08/10/2003Published in print08/10/2003 License: Citations and impact KeywordsALE numerical modelnonlinear free surface wavesfluid–rigid structure interactionspartitioned solution procedurenonlinear dynamics

Nonlinear stability of a fluid-loaded elastic plate with mean flow

It has been known for some time that the unsteady interaction between a simple elastic plate and a mean flow has a number of interesting features, which include, but are not limited to, the existence of negative-energy waves (NEWs) which are destabilized by the introduction of dashpot dissipation, and convective instabilities associated with the flow–surface interaction. In this paper we consider the nonlinear evolution of these two types of waves in uniform mean flow. It is shown that the NEW can become saturated at weakly nonlinear amplitude. For general parameter values this saturation can be achieved for wavenumber k corresponding to low-frequency oscillations, but in the realistic case in which the coefficient of the nonlinear tension term (in our normalization proportional to the square of the solid–fluid density ratio) is large, saturation is achieved for all k in the NEW range. In both cases the nonlinearities act so as increase the restorative stiffness in the plate, the oscillation frequency of the dashpots driving the NEW instability decreases, and the system approaches a state of static deflection (in agreement with the results of the numerical simulations of Lucey et al. 1997). With regard to the marginal convective instability, we show that the wave-train evolution is described by the defocusing form of the nonlinear Schrödinger (NLS) equation, suggesting (at least for wave trains with compact support) that in the long-time limit the marginal convective instability decays to zero. In contrast, expansion about a range of other points on the neutral curve yields the focusing form of the NLS equation, allowing the existence of isolated soliton solutions, whose amplitude is shown to be potentially significant for realistic parameter values. Moreover, when slow spanwise modulation is included, it turns out that even the marginal convective instability can exhibit solitary-wave behaviour for modulation directions lying outside broad wedges about the flow direction.