Authors:A. M. Razmi; U. Lemmin; D. Bouffard; A. Wüest; R. E. Uittenbogaard; D. A. Barry Pages: 415 - 428 Abstract: Numerical simulations were carried out to investigate gyres within open lacustrine embayments subjected to parallel-to-shore currents. In such embayments, gyre formation occurs due to flow separation at the embayment’s upstream edge. High momentum fluid from the mixing layer between the embayment and offshore flows into the embayment and produces recirculating flow. Systematic numerical experiments using different synthetic embayment configurations were used to examine the impact of embayment geometry. Geometries included embayments with different aspect ratios, depths and embayment corner angles. The magnitudes of the recirculation and turbulent kinetic energy (TKE) in the embayment vary significantly for angles in the range 40°–55°. Embayments with corner angles less than 50° have much stronger recirculation and TKE, other parameters remaining the same. The numerical findings are consistent with gyre formation observed in two embayments located in Lake Geneva, Switzerland, and thus help explain flow patterns recorded in lacustrine shoreline regions. PubDate: 2017-06-01 DOI: 10.1007/s10652-016-9494-8 Issue No:Vol. 17, No. 3 (2017)

Authors:Emmanuel Mignot; Wei Cai; Juan Ignacio Polanco; Cristian Escauriaza; Nicolas Riviere Pages: 429 - 448 Abstract: Lateral cavities are major storage zones in riverine environments for which the mass exchanges with the main stream strongly impact the characteristics of the habitat in these dead zones. An experimental work is presented here with a controlled main stream and a connected open-channel lateral cavity to assess the processes responsible for these exchanges and to quantify the exchange capacities. In a first step, the measurements of passive scalar transport allow us to identify the physical processes involved in the exchange of mass from the main stream and its spreading within the cavity. In a second step, the quantitative mass exchange coefficient, representative of the exchange capacity, is measured for 28 flow and cavity configurations. The sensibility analysis to the governing parameters proposed by the dimensional analysis then reveals that changing the geometric aspect ratio of the cavity does not affect the exchange coefficient while increasing the normalized water depth or decreasing the Reynolds number of the main stream tend to increase this coefficient. Indeed, these parameters modify both the growth rate of the mixing layer width at the interface and the amplitude of the alternating transverse velocity across the interface, thus affecting the exchange capacities from the main stream to the cavity. PubDate: 2017-06-01 DOI: 10.1007/s10652-016-9495-7 Issue No:Vol. 17, No. 3 (2017)

Authors:Snehasis Kundu; Koeli Ghoshal Pages: 449 - 472 Abstract: This paper presents a mathematical model to investigate type II profile of suspension concentration distribution (i.e., the concentration profile where the maximum concentration appears at some distance above the bed surface) in a steady, uniform turbulent flow through open-channels. Starting from the mass and momentum conservation equations of two-phase flow, a theoretical model has been derived. The distribution equation is derived considering the effects of fluid lift force, drag force, particle inertia, particle–particle interactions, particle velocity fluctuations and drift diffusion. The equation is solved numerically and is compared with available experimental data as well as with other models existing in the literature. Good agreement between the observed value and computed result, and minimum error in comparison to other models indicate that the present model can be applied in predicting particle concentration distribution for type II profile for a wide range of flow conditions. The proposed model is also able to show the transition from type I profile to type II profile. PubDate: 2017-06-01 DOI: 10.1007/s10652-016-9498-4 Issue No:Vol. 17, No. 3 (2017)

Authors:Michael R. Allshouse; Gregory N. Ivey; Ryan J. Lowe; Nicole L. Jones; C. J. Beegle-Krause; Jiangtao Xu; Thomas Peacock Pages: 473 - 483 Abstract: Windage, the additional direct, wind-induced drift of material floating at the free surface of the ocean, plays a crucial role in the surface transport of biological and contaminant material. Lagrangian coherent structures (LCS) uncover the hidden organizing structures that underlie material transport by fluid flows. Despite numerous studies in which LCS ideas have been applied to ocean surface transport scenarios, such as oil spills, debris fields and biological material, there has been no consideration of the influence of windage on LCS. Here we investigate and demonstrate the impact of windage on ocean surface LCS via a case study of the ocean surrounding the UNESCO World Heritage Ningaloo coral reef coast in Western Australia. We demonstrate that the inclusion of windage is necessary when applying LCS to the study of surface transport of any floating material in the ocean. PubDate: 2017-06-01 DOI: 10.1007/s10652-016-9499-3 Issue No:Vol. 17, No. 3 (2017)

Authors:Elizabeth Smith; Evgeni Fedorovich; Alan Shapiro Pages: 485 - 495 Abstract: This study focuses on the inertial oscillation aspect of the nocturnal low-level jet (NLLJ). In the context of the Ekman model solutions, conceptual NLLJ inertial oscillation analytical frameworks proposed by Blackadar in 1957 and Shapiro and Fedorovich and van de Wiel et al. in 2010 are compared. Considering a NLLJ produced via direct numerical simulation over flat terrain with no baroclinic influence as a reference case, the deficiencies of each framework in representing a realistic NLLJ are assessed. The Blackadar theory results in unrealistic wind profiles near the surface. While extensions of Blackadar’s framework by Shapiro and Fedorovich and van de Wiel et al. produce more realistic NLLJs, the simpler approach taken by van de Wiel et al. does not describe the NLLJ wind hodograph at later times sufficiently in qualitative terms. PubDate: 2017-06-01 DOI: 10.1007/s10652-016-9502-z Issue No:Vol. 17, No. 3 (2017)

Authors:Chao Yan; Heidi M. Nepf; Wei-Xi Huang; Gui-Xiang Cui Pages: 497 - 519 Abstract: Predicting flow and mass transport in vegetated regions has a broad range of applications in ecology and engineering practice. This paper presents large eddy simulation (LES) of turbulent flow and scalar transport within a fully developed open-channel with submerged vegetation. To properly represent the scalar transport, an additional diffusivity was introduced within the canopy to account for the contribution of stem wakes, which were not resolved by the LES, to turbulent diffusion. The LES produced good agreement with the velocity and concentration fields measured in a flume experiment. The simulation revealed a secondary flow distributed symmetrically about the channel centerline, which differed significantly from the circulation in a bare channel. The secondary circulation accelerated the vertical spread of the plume both within and above the canopy layer. Quadrant analysis was used to identify the form and shape of canopy-scale turbulent structures within and above the vegetation canopy. Within the canopy, sweep events contributed more to momentum transfer than ejection events, whereas the opposite occurred above the canopy. The coherent structures were similar to those observed in terrestrial canopies, but smaller in scale due to the constraint of the water surface. PubDate: 2017-06-01 DOI: 10.1007/s10652-016-9503-y Issue No:Vol. 17, No. 3 (2017)

Authors:Denise Hertwig; Gopal Patnaik; Bernd Leitl Pages: 521 - 550 Abstract: Essential prerequisites for a thorough model evaluation are the availability of problem-specific, quality-controlled reference data and the use of model-specific comparison methods. The work presented here is motivated by the striking lack of proportion between the increasing use of large-eddy simulation (LES) as a standard technique in micro-meteorology and wind engineering and the level of scrutiny that is commonly applied to assess the quality of results obtained. We propose and apply an in-depth, multi-level validation concept that is specifically targeted at the time-dependency of mechanically induced shear-layer turbulence. Near-surface isothermal turbulent flow in a densely built-up city serves as the test scenario for the approach. High-resolution LES data are evaluated based on a comprehensive database of boundary-layer wind-tunnel measurements. From an exploratory data analysis of mean flow and turbulence statistics, a high level of agreement between simulation and experiment is apparent. Inspecting frequency distributions of the underlying instantaneous data proves to be necessary for a more rigorous assessment of the overall prediction quality. From velocity histograms local accuracy limitations due to a comparatively coarse building representation as well as particular strengths of the model to capture complex urban flow features with sufficient accuracy are readily determined. However, the analysis shows that further crucial information about the physical validity of the LES needs to be obtained through the comparison of eddy statistics, which is focused on in part II. Compared with methods that rely on single figures of merit, the multi-level validation strategy presented here supports conclusions about the simulation quality and the model’s fitness for its intended range of application through a deeper understanding of the unsteady structure of the flow. PubDate: 2017-06-01 DOI: 10.1007/s10652-016-9507-7 Issue No:Vol. 17, No. 3 (2017)

Authors:Denise Hertwig; Gopal Patnaik; Bernd Leitl Pages: 551 - 578 Abstract: Time-dependent three-dimensional numerical simulations such as large-eddy simulation (LES) play an important role in fundamental research and practical applications in meteorology and wind engineering. Whether these simulations provide a sufficiently accurate picture of the time-dependent structure of the flow, however, is often not determined in enough detail. We propose an application-specific validation procedure for LES that focuses on the time dependent nature of mechanically induced shear-layer turbulence to derive information about strengths and limitations of the model. The validation procedure is tested for LES of turbulent flow in a complex city, for which reference data from wind-tunnel experiments are available. An initial comparison of mean flow statistics and frequency distributions was presented in part I. Part II focuses on comparing eddy statistics and flow structures. Analyses of integral time scales and auto-spectral energy densities show that the tested LES reproduces the temporal characteristics of energy-dominant and flux-carrying eddies accurately. Quadrant analysis of the vertical turbulent momentum flux reveals strong similarities between instantaneous ejection-sweep patterns in the LES and the laboratory flow, also showing comparable occurrence statistics of rare but strong flux events. A further comparison of wavelet-coefficient frequency distributions and associated high-order statistics reveals a strong agreement of location-dependent intermittency patterns induced by resolved eddies in the energy-production range. The validation concept enables wide-ranging conclusions to be drawn about the skill of turbulence-resolving simulations than the traditional approach of comparing only mean flow and turbulence statistics. Based on the accuracy levels determined, it can be stated that the tested LES is sufficiently accurate for its purpose of generating realistic urban wind fields that can be used to drive simpler dispersion models. PubDate: 2017-06-01 DOI: 10.1007/s10652-016-9504-x Issue No:Vol. 17, No. 3 (2017)

Authors:Cynthia E. Bluteau; Roger Pieters; Gregory A. Lawrence Pages: 579 - 590 Abstract: Laboratory experiments have been performed to investigate the effects of salt exclusion on the behaviour of lakes with salinities up to 8 g L−1. At these salinities the freezing temperature is less than the temperature of maximum density and, unlike sea-ice, a reverse temperature stratification forms beneath the ice that can support at least some of the excluded salt. Temperature time series at four depths showed that salt exclusion drives cascades of localised overturning, while the persistence of reverse temperature stratification indicated that mixing was not complete. While our array of temperature sensors had insufficient spatial resolution to provide full details of the flow, we hypothesize that: at salinities of 1 and 2 g L−1 salt is released relatively uniformly and forms a layer of elevated salinity immediately below the ice, which supports double-diffusive salt-fingering; and at salinities of 4 and 8 g L−1, salt plumes penetrate the reverse stratification. After the ice melted, a relatively fresh surface layer formed above a more saline layer, sufficient to suppress spring turnover. Our measurements compare favourably with field observations from lakes, and highlight the importance of salt exclusion on biogeochemical processes in lakes. PubDate: 2017-06-01 DOI: 10.1007/s10652-016-9508-6 Issue No:Vol. 17, No. 3 (2017)

Authors:Debasish Pal; Koeli Ghoshal Pages: 591 - 613 Abstract: Here we propose a theoretical model to compute the suspended grain-size distribution in fluvial environment. We derive the model based on the Reynolds averaged Navier–Stokes equation and the continuity equation of sediment phase. The model includes the effects of secondary current and stratification which are the cause of complex interaction between turbulence and grain-size distribution in the sediment-laden flow. Due to an immense importance of particle–particle and particle-turbulence interactions near the channel bed, we include their impacts in the boundary condition of the model. The present model has noteworthy contribution to demonstrate the phenomena of suspended grain-size distribution in the real world. Reported experimental data in literature shows well agreement with the numerical solution computed from the suggested model. The better computational accuracy of the present model is ascertained when the upper bound of calculated error between observed experimental data and computed values is found to be lowest for our model in comparison to a large number of existing models developed from different mathematical viewpoints. PubDate: 2017-06-01 DOI: 10.1007/s10652-017-9510-7 Issue No:Vol. 17, No. 3 (2017)

Authors:P. Angelidis; D. Kalpakis; V. Gyrikis; N. Kotsovinos Pages: 615 - 628 Abstract: We consider the problem of the vertically upwards disposal of heavy brine sewage from a two-dimensional diffuser in a lighter, homogeneous, motionless and shallow ambient sea. The rejected high salinity water of seawater desalination plants for urban and agricultural uses is such a case of a two dimensional fountain. The disposal of brine sewage produces a negative buoyant jet due to its initial momentum, which impinges on the free surface, spreads laterally on it and then sinks downwards, because of the negative buoyancy. Laboratory experiments and dimensional considerations are used in this paper in order to investigate the spreading behavior (width) of the vertical fountain which impinges on the free surface of the shallow ambient fluid. The experimental results have been used to derive an equation relating the width at the free surface with the initial parameters of the flow. In addition, the experimentally measured dilution of the heavier brine sewage on the recipient’s surface is compared with the dilution which was calculated by a numerical simulation of a well-known commercial software package, CORJET (a CORMIX sub model). PubDate: 2017-06-01 DOI: 10.1007/s10652-017-9511-6 Issue No:Vol. 17, No. 3 (2017)

Authors:Sayed Mahdi Zandi; Amin Rafizadeh; Ahamd Shanehsazzadeh Abstract: A meshless method based on exponential basis functions (EBFs) is developed to simulate the propagation of solitary waves and run-up on the slope. The presented method is a boundary-type meshless method applying the exponential basis functions with complex exponents. The solution of governing equations is considered as a series of these basis functions. Boundary conditions are satisfied through a point-wise collocation approach. Based on the presented EBF meshless method, a new formula is introduced for the maximum run-up height on different slopes, valuable for engineering applications. The results obtained through the numerical method in the prediction of solitary wave propagation and estimation of run-up are verified through the comparison with experimental data. The comparison with 159 experimental data indicates that this new formula is more accurate than the preceding formulas in predicting the maximum run-up of non-breaking solitary waves. Minimum calculation time and convenient performances are the other advantages of this method. PubDate: 2017-06-01 DOI: 10.1007/s10652-017-9533-0

Authors:Feng Wu; Wan-Xie Zhong Abstract: The primary purpose of this paper is to develop an efficient numerical scheme for solving the shallow water wave problem with a sloping water bottom and wet-dry interface. For this purpose, the Lagrange method and the constrained Hamilton variational principle are used to solve the shallow water wave problem. According to the constrained Hamilton variational principle, a shallow water equation based on the displacement and pressure (SWE-DP) is derived. Based on the discretized constrained Hamilton variational principle, a numerical scheme is developed for solving the SWE-DP. The proposed scheme combines the finite element method for spatial discretization and the simplectic Zu-class method for time integration. The correctness of the SWE-DP and the effectiveness of the proposed scheme are verified by three classical numerical examples. Numerical examples show that the proposed method performs well in the simulation of the shallow water problem with a sloping water bottom and wet-dry interface. PubDate: 2017-05-31 DOI: 10.1007/s10652-017-9538-8

Authors:Quentin Rendu; Emmanuel Mignot; Nicolas Riviere; Barbara Lamberti-Raverot; Sara Puijalon; Florence Piola Abstract: Seed and fruit dispersal along watercourses favours the long-distance migration of invasive species, not only for aquatic or wetland species, but also for terrestrial wind-dispersed plants, like the Japanese knotweed. The present paper aims at investigating the role of watercourses in the dispersal of the knotweed due to its frequent occurrence on riverbanks and production of fertile achenes (type of fruit of the Japanese knotweed). This dispersal occurs along two steps after the fruits deposit on the water surface: floatation first and then sinking towards the bottom of the watercourse. Regarding the first step, the effects of agitation of the water, temperature, surface tension and luminosity on the achenes floatability are experimentally studied. While no influence of luminosity is observed, an increase of temperature greatly decreases the floating time. Floating time also decreases as the contact between water and the fruit is enhanced (through submersion of achenes, agitation of the water or lower surface tension). Regarding the second step, the fall velocity of the fruits in water at rest is measured and appears to be independent of the seed history (floating time). 3D helical motions are systematically observed with constant tangential velocity with respect to the falling velocity. The trajectory of the fruits in a shear flow is then measured and the evolution of their velocity components along the sinking process is discussed. Finally, the contribution of both steps to the long-distance migration of the seeds is estimated. PubDate: 2017-05-29 DOI: 10.1007/s10652-017-9537-9

Authors:Marius Ungarish Abstract: We present a brief review of the recent investigations on gravity currents in horizontal channels with non-rectangular cross-section area (such as triangle, \(\bigvee \) -valley, circle/semi-circle, trapezoid) which occur in nature (e.g., rivers) and constructed environment (tunnels, reservoirs, canals). To be specific, we discuss the propagation of a gravity current (GC) in a horizontal channel along the horizontal coordinate x, with gravity g acting in the \(-z\) direction, and y the horizontal–lateral coordinate. The bottom and top of the channel are at \(z=0,H\) . The “standard” problem is concerned with 2D flow in a channel with rectangular (or laterally unbounded) cross-section area (CSA). Recent investigations have successfully extended the standard knowledge to the channels of CSA given by the quite general \(-f_1(z)\le y \le f_2(z)\) for \(0 \le z \le H\) . This includes the practical \(\bigvee \) -valley, triangle, circle/semi-circle and trapezoid; these geometries may be in “up” or “down” setting with respect to gravity, e.g., \(\bigtriangleup \) and \(\bigtriangledown \) . The major objective of the extended theory is to predict the height of the interface \(z=h(x,t)\) and the velocity (averaged over the CSA) u(x, t), where t is time; the prediction includes the speed and position of the nose \(u_N(t), x_N(t)\) . We show that the motion is governed by a set of simplified equations, called “model,” that provides versatile and insightful solutions and trends. The emphasis in on a high-Reynolds-number current whose motion is dominated by buoyancy–inertia balance; in particular a GC released from a lock, which also contains general effects such as front and internal jumps (shocks), and reflected bore. We discuss two-layer, one-layer, and box models; Boussinesq and non-Boussinesq systems; compositional and particle-driven cases; and the effect of stratification of the ambient fluid. The models are self-contained, and admit realistic initial and boundary conditions. The governing equations are amenable to analytical solutions in some special circumstances. Some salient features of the buoyancy-viscous regime, and the estimate for the length at which transition to this regime takes place, are also presented. Some experimental support to the theory, and open questions for further investigations, are also mentioned. The major conclusions are (1) The CSA geometry has significant influence on the motion of the GC; and (2) The new theory is a useful, very significant, extension of the standard two-dimensional GC problem. The standard current is just a particular case, \(f_{1,2} =\) constants, among many other covered by the new theory . PubDate: 2017-05-29 DOI: 10.1007/s10652-017-9535-y

Authors:Xiaoguang Liu; Yuhong Zeng Abstract: Drag coefficient has been commonly used as a quantifying parameter to represent the vegetative drag, i.e., resistance to the flow by vegetation. In this study, the measured data on the drag coefficient for rigid vegetation in subcritical open-channel flow reported in previous studies are collected and preprocessed for multi-parameter analysis. The effect of Froude number (Fr) on the drag coefficient for rigid vegetation in subcritical flow cannot be ignored, especially when \(Fr < 0.12\) . The drag coefficient is observed to exponentially decrease with the stem Reynolds number (R d ) and logarithmically decreased with the vegetation density (λ) when \(0.012 < \lambda < 0.12\) . The relative submergence (h * ) has a significant effect on the drag coefficient, and a positive logarithmic relationship is summarized. A simplified three-stage empirical formula is obtained based on the divisions of Fr. Laboratory tests (with \(Fr < 0.02\) ) prove that the present empirical model has higher precision compared with existing models. PubDate: 2017-05-17 DOI: 10.1007/s10652-017-9534-z

Authors:Alberto de la Fuente; Carolina Meruane Abstract: The influence of sediments in the heat budget of water bodies has been reported to be determinant in shallow lakes and wetlands, whereas it is usually neglected in larger water bodies. In this article, we address the question of whether or not sediments should be considered in the computation of water temperature, by defining two dimensionless numbers that describe the thermodynamics regimes of shallow lakes and wetlands. These dimensionless numbers rise from the analysis of the role of periodic heat exchanges at the sediment–water interface (SWI) on the water temperature of shallow lakes and wetlands. The analysis was based on the derivation of an analytic solution that adopts the solution for the second Stokes problem for computing the sediment temperature, when the system is forced by periodic (diurnal, seasonal, decadal) heat exchanges with the atmosphere. The first dimensionless number is the ratio between the thermal inertia of the active sediments and the thermal inertia of the water column, and quantifies the role of sediments on the heat budget. The second dimensionless number, on the other hand, is defined as the ratio between the timescale of changes in the external forcing and the timescale required to reach the heat equilibrium at the SWI, and characterizes the influence of turbulence on the water column on heat exchanges across the SWI. We complemented the analysis with field observations conducted in shallow lakes of 5–15 cm depth, whose thermodynamics is controlled by heat exchanges between the water column and the sediments. As the dimensionless numbers defined here are frequency dependent, we show that one particular process can be neglected for one specific frequency, while it cannot be neglected for other frequencies. In the case of lakes and deep wetlands, sediments could be neglected in a diurnal time-scale, while they should be included for seasonal or decadal time-scales. The relevance of this frequency-dependence is that it suggests that sediments should always be considered in long-term climatic simulations. PubDate: 2017-05-16 DOI: 10.1007/s10652-017-9536-x

Authors:Soumen Maji; Debasish Pal; Prashanth R. Hanmaiahgari; Umesh P. Gupta Abstract: This present study reports the results of an experimental study characterizing thorough variation of turbulent hydrodynamics and flow distribution in emergent and sparsely vegetated open channel flow. An emergent and rigid sparse vegetation patch with regular spacing between stems along the flow and transverse directions was fixed in the central region of the cross-section of open channel. Experiments were conducted in subcritical flow conditions and velocity measurements were obtained with an acoustic Doppler Velocimetry system. Large variations of the turbulence intensities, Reynolds shear stress, turbulent kinetic energy and vortical motions are found in and around the vegetation patch. At any cross-section through the interior of the vegetation patch, streamwise velocity decreases with increase in streamwise length and the velocity profiles converge from the log-law to a linear profile with increasing slope. Time-averaged lateral and vertical velocities inside the vegetation patch increase with increasing streamwise distance and converge from negative values to positive values. Turbulence intensities interior of the sparse vegetation patch are more than those of without the vegetation patch. Similar to the trend of streamwise velocity profiles inside the vegetation, turbulence intensities and longitudinal-normal Reynolds shear stress profile decreases with streamwise direction. In the interior of the vegetation patch and downstream of the trailing edge, turbulent kinetic energy profiles are exhibiting irregular fluctuations and the maximum values are occurring in the outer layer. Analysis of flow distribution confirms sparse vegetation patch is inducing a serpentine flow pattern in its vicinity. At the leading edge, flow is rushing towards the right hand sidewall, and at the trailing edge, flow is turning to the left hand sidewall. In between the leading and trailing edges, the streamlines are following a zig-zag fashion at varied degree along the streamwise and lateral directions. Immediate upstream of the leading edge and in the interior of the vegetation patch, vortex motion is clearly visible and the vortices are stretched along the width of the channel with streamwise direction. PubDate: 2017-05-12 DOI: 10.1007/s10652-017-9531-2

Authors:Olivier Oldrini; Patrick Armand; Christophe Duchenne; Christophe Olry; Jacques Moussafir; Gianni Tinarelli Abstract: Noxious atmospheric releases may originate from both accidents and malicious activities. They are a major concern for public authorities or first responders who may wish to have the most accurate situational awareness. Nonetheless, it is difficult to reliably and accurately model the flow, transport, and dispersion processes in large complex built-up environments in a limited amount of time and resources compatible with operational needs. The parallel version of Micro-SWIFT-SPRAY (PMSS) is an attempt to propose a physically sound and fast response modelling system applicable to complicated industrial or urban sites in case of a hazardous release. This paper presents and justifies the choice of the diagnostic flow and Lagrangian dispersion models in PMSS. Then, it documents in detail the development of the parallel algorithms used to reduce the computational time of the models. Finally, the paper emphasizes the preliminary model validation and parallel performances of PMSS based on data from both wind tunnel (Evaluation of Model Uncertainty) and in-field reduced-scale (Mock Urban Setting Test) and real-scale (Oklahoma City) experimental campaigns. PubDate: 2017-05-08 DOI: 10.1007/s10652-017-9532-1

Authors:Ting Zhang; Fangxin Fang; Ping Feng Abstract: Dam failures usually cause huge economic and life losses , especially in urban areas where there is a high concentration of inhabitants and economic actors. In order to understand the physical mechanisms of the formation and development of dam-break flooding, lots of efforts have been put into different types of modelling techniques. However, most of existing models are 1D (one-dimensional) or 2D models based on the shallow water equations. In this paper, we present a 3D numerical modelling investigation of dam-break flow hydrodynamics in an open L-shape channel. A newly developed 3D unstructured mesh finite element model is used here. An absorption-like term is introduced to the Navier–Stokes equations in order to control the conditioning of the matrix equation in the numerical solution process and thus improve the stability. A wetting and drying algorithm is used here to allow the free surface height to be treated with a high level of implicitness and stability. The 3D model has been validated by comparing the results with the published experimental data. Good agreement has been achieved at six selected locations. This study shows that the 3D unstructured mesh model is capable of capturing the 3D hydraulic aspects and complicated local flows around structures in simulation of dam-break flows. PubDate: 2017-04-21 DOI: 10.1007/s10652-017-9530-3