In this article we describe the details of an ABLE-LBM (Atmospheric Boundary Layer Environment-Lattice Boltzmann Model) validation study for urban building array turbulent flow simulations. The ABLE-LBM large-eddy simulation results were compared with a set of 3D magnetic resonance image (MRI) velocimetry data. The ABLE-LBM simulations used the same building layout and Reynolds numbers operated in

The quantification of turbulent mixing in nature is predicated by inherent randomness of causal events, and obtaining relevant turbulence statistics requires ensemble averaging of identical realizations that are unachievable in field observations or onerous in laboratory situations. Laboratory modeling is often used to study nonstationary natural processes, but jitters due to intrinsic variability

Air curtains are produced by thin vertical planar air jets and are used to prevent exchange flows between two fluids with a horizontal density gradient. They have been shown to work effectively provided the deflection modulus (DM) is greater than a critical value (DM = 0.14). Herein, results are presented from an experimental and modeling study of the initial transient development of the buoyancy distribution

The simultaneous observations from a Doppler weather radar and an instrumented micrometeorological tower, offer an opportunity to dissect the effects of a gust front on the surface layer turbulence in a tropical convective boundary layer. We present a case study where a sudden drop in temperature was noted at heights within the surface layer during the passage of a gust front in the afternoon time

An internal wave is a propagating disturbance within a stable density-stratified fluid. The internal seiche amplitude is often estimated through theories that describe the amplitude growth based on the Bulk Richardson number (Ri). However, most theoretical formulations neglect secondary effects that may influence the evolution of internal seiches. Since these waves have been pointed out as the most

In this laboratory study, propagation behaviour, particle deposition patterns, and suspension characteristics of non-cohesive particle-driven gravity currents formed under constant-volume release conditions were investigated. The experimental gravity currents were created in a two-dimensional lock exchange type tank using two different particles (silicon carbide and glass beads) with four different

Understanding scalar transport in solvents is important in chemical engineering, pollution control, and water remediation, where the longitudinal dispersion coefficient (LDC) is a key parameter for describing solute transport in fluids. For flow in classic conditions such as in a pipe or a regular open channel, formulas for LDC are derived from adopting the ideas of the advection–diffusion equation

The effects of obstacle-height variability on spatial characteristics of turbulent organized structures were investigated with the use of a large-eddy simulation technique for airflows over roughness obstacles. Two-types simulation cases were considered: one is uniform-height case in which uniform-height obstacles are aligned in streamwise direction, the other is height-variability case with staggered

Local pier scour has been recognized as one of the most significant causes of bridge failures. Despite numerous studies on the subject of local pier scour have been conducted, there remain problems in accurate scour prediction because almost of the past studies have focused only on scour depth around simple shape of a bridge pier with or without considering their time development, even though prototype

The following article addresses the issue of wind conditions around urban building development at pedestrian level. Factors that depend on those issues include wind comfort and air quality within urbanized spaces. The conditions specific of cities located in a temperate climate zone have been taken into account. The article is intended to identify aerodynamic phenomena characteristic of the three basic

In this study, we explore several integral and outer length scales of turbulence which can be formulated by using the dissipation of temperature fluctuations (\(\chi\)) and other relevant variables. Our analyses directly lead to simple yet non-trivial parameterizations for both spatially-averaged \(\overline{\chi }\) and the structure parameter of temperature (\(C_T^2\)). For our purposes, we make

Employing inclined negatively buoyant jets is one of the most advantageous means to discharge brine or waste in coastal environments. However, numerical prediction of mixing parameters for this kind of flow is still a challenge. In this investigation, CFD simulations of \(45^\circ \) inclined dense jets were conducted using realizable k–\(\epsilon \) model with buoyancy corrections and different values

An alluvial-proluvial fan (APF) has heterogeneous characteristics, which result in the development of imbricated gravel channel networks formed by flow erosion. In this type of aquifer, groundwater flow and solute transport are significantly affected by the connectivity of the channels. This paper investigates the 2D connectivity of a heterogeneous APF aquifer based on a case study of the Dali APF

Patches of vegetation in natural water bodies grow close to each other and may affect each other’s wake pattern with significant implications on nutrient uptake and local sediment transport. This experimental study analyzed the wakes of two neighboring circular patches of emergent artificial vegetation with different densities, with the tested solid volume fractions being equal to 0.059, 0.114, and

Bed-load transport is a complex process exhibiting anomalous dynamics, which cannot be efficiently described using the traditional advection–diffusion equation. This study aims at developing and testing a Hausdorff fractal derivative model to characterize scale-dependent, anomalous dynamics of bed-load transport through a heterogeneous gravel-bed. Applications show that the Hausdorff fractal derivative

A large set of experimental solute tracer breakthrough data (corresponding to more than 350 individual tracer breakthrough curves) in eight granular filter materials, were used to investigate the links between solute dispersivity and the shape of the pore velocity—relative pore area distributions for the materials. Solute dispersivity values and the shape of the pore velocity—relative pore area distributions

A series of experiments were conducted to quantify the dynamics of a filling box driven by a line plume that spans the full width of the enclosure. Three configurations were tested namely symmetric (centrally located plume), wall-bounded (plume attached to an end wall), and asymmetric. The front movement for the symmetric and wall-bounded configurations was well described by the standard filling box

The dispersion (transport and breakup) of oil droplets under breaking waves is essential for evaluating the impact of oil spills on the environment, and for designing countermeasures. In this part of the work (Part I), the hydrodynamics of a wave breaker in a 1.0 m deep tank obtained experimentally by Rapp and Melville (Philos Trans R Soc Lond A Math Phys Eng Sci 331(1622):735–800, 1990) using the

This paper aims at addressing issues related to the misrepresentation of the turbulent stratified flow for sand wave simulation using the continuum coupled flow and morphodynamics modeling approach. continuum flow and morphodynamics frameworks often consider the contributions of (i) suspended sediment-load in the sediment mass-balance equation and (ii) stratification in the equations of fluid motion

The water waves resulting from the collapse of a dam are important unsteady free surface flows in civil and environmental engineering. Considering the basic case of ideal dam break waves in a horizontal and rectangular channel the wave patterns observed experimentally depends on the initial depths downstream (hd) and upstream (ho) of the dam. For r = hd/ho above the transition domain 0.4–0.55, the

We report upon a series of laboratory experiments and complementary (two-dimensional) direct numerical simulations that explore the lock release of a fixed volume of dense fluid into a two-layer density-stratified ambient. By initial condition, the lock release experiments/simulations fall into one of two categories: full-depth and partial-depth. Our particular focus is on the “tailwaters” limiting

The complex three-dimensional flow that develops around an inclined flat solar panel near the ground is investigated using Computational Fluid Dynamics. The early stage evolution of the flow and the interaction of the shear layers emanating from the sides of the panel, the large separation region behind the panel and the boundary layers on the panel and ground are captured using Delayed Detached-Eddy

The influence of channel side slope on flow in strongly curved channel bends is studied numerically. The performances of five different turbulence models are investigated. Comparison to experimental measurements demonstrates that the fully 3D numerical model can reliably simulate a channel bend flow field. Among the tested turbulence models, the realizable k − ε model performed best. The present study

This paper proposes a model for predicting the longitudinal profiles of streamwise velocities in an open channel with a model patch of vegetation. The governing equation was derived from the momentum equation and flow continuity equation. The model can estimate the longitudinal profiles of velocities both inside and outside a vegetation patch. Laboratory experiments indicate that the longitudinal profiles

In this work, a summary of Leonardo da Vinci’s contribution in the field of fluid mechanics is reported. Some theoretical laws or fluid flows analyzed or drawn by Leonardo are highlighted, such as vortices, flow fields with obstacles, the continuity law, waves, velocity profiles in open channels, as well as some ingenious contributions in the field of hydraulic constructions and machines.

The results of an experimental study on the turbulence characteristics in flow over and downstream of an isolated bedform are presented. The vertical profiles of time-averaged streamwise velocity, Reynolds stresses and turbulent kinetic energy (TKE) fluxes at different horizontal locations over and downstream of a bedform are shown to demonstrate their variations. The experimental results signify a

Transport of air pollutants emitted from urban valleys can be strongly restricted by interactions between static and dynamic factors including topographic forcing, low-level atmospheric stability related to temperature inversions, and urban heat island-induced circulations. Interplay between these processes has a complex and dynamic nature, and is determinant for the evolution of different ventilation

In plunging jets and at hydraulic jumps, large amounts of air bubbles are entrained at the impingement of the liquid jet into the receiving body. Air is entrapped and advected into a turbulent shear layer with strong interactions between the air bubble advection process and momentum shear flow. In this new physical study, air–water flow measurements were systematically repeated with identical inflow

A compression wave is an unsteady rapidly-varied open channel flow motion, characterised by an increase in water depth. A detailed investigation was conducted in a prismatic asymmetrical channel, to better understand the physical processes observed in tidal/tsunami-bore affected estuaries with irregular topography. The prismatic channel was equipped with a 1 V:5H transverse slope across the full channel

Modern turbulence models allow for detailed numerical solutions, involving millions of data points and numerous degrees of freedom; these solutions have the potential to provide notable insights into the flows past hydraulic structures. In this paper, we present new analyses of a Detached-eddy simulation of the flow past stepped spillways in three dimensions, in order to investigate the coherent structures

Most studies on sediment transport and bedforms migration consider unlimited sediment supply conditions. However, areas where the sediment supply is limited are common in coastal and fluvial environments. The present paper, based on physical modelling in a flume and on a re-analysis of field data obtained in the Eastern English Channel by Ferret (Morphodynamique des dunes sous-marines en contexte de

The dispersion of surface jets in crossflows such as rivers or channels can cause critical environmental problems in the form of chemical or thermal pollution of these water bodies. The turbulent flow structures occurring in such crossflows play an important role in the mixing of surface jets with the surrounding water bodies. In this study, experimental measurements of the time history of the 3-D

We present results from water-channel experiments on neutrally-stable turbulent flows over staggered arrays of cubical obstacles modelling idealised urban canopies. Attention is concentrated on the vertical profiles of the Eulerian (TE) and Lagrangian (TL) time scales of the turbulence above three canopies with different plan area fractions (λP = 0.1, 0.25 and 0.4). The results show that both the streamwise

A comprehensive investigation of velocity distribution is presented, and the log law is re-examined using experimental data from a smooth uniform open channel flow. It is widely reported that the coefficients of the log law in channel flows deviate from those obtained from circular pipe flows by Nikuradse (Laws of flow in rough pipes, 1933), but the mechanism is not clear and no theoretical formulae

During the application of semi-theoretical models to predict peak discharges for breached embankment dams, it is often encountered to be lack of necessary model parameters such as breach height. In order to solve this deficiency and improve the application of the semi-theoretical models for estimating the peak discharge, a mathematical relation is proposed to predict the breach height (Hb) using the

The present paper analyses the advantages and limitations of using numerical modelling to simulate hydraulic jumps at high Froude numbers. Two hydraulic jumps of the same Froude number (7.5) but different Reynolds numbers were simulated using Improved Delayed Detached Eddy Simulation. The free surface was captured using the Volume of Fluid multiphase model with a High-Resolution Interface-Capturing

The accurate simulation of wetting–drying processes in floodplains and coastal zones is a challenge for hydrodynamic modelling, especially for long time simulations. Indeed, dedicated numerical procedures are generally time-consuming, instabilities can occur at the wet/dry front, rapid transition of wet/dry interface and mass conservation are not always ensured. We present the extension of an existing

Near-bed flows in rough-bed open-channels are of relevance to river engineering, freshwater ecology and hydraulic design. Detailed measurements of near-bed flow velocity and turbulence distributions are rarely available. This paper aims to improve our understanding of near-bed flow characteristics. We performed experiments of turbulent open-channel flow over roughness elements, and made fine-scale

The influence of turbulence on the settling velocity of small particles remains an inconclusive research subject. Both enhanced and retarded particle settling compared to quiescent settling have been reported in previous literature, and several theories have been proposed. Among the mechanisms that account for reduced settling velocities in turbulence, the loitering effect is an important one that

Wood is recognized as a key element of river ecosystem for a large number of positive feedbacks with biotic and abiotic components, both when it is present as large wood deposit or as live vegetation on the riparian zone. Despite the positive impacts of wood, when considering the high flow events, the presence of woody riparian vegetation within the channel can increase the potential risk related to

Spatial dimensions of bedforms relative to the flow depth are of great interest for both engineers and geoscientists, and continue to be an active area of research. These morphological features are of significant consequence for critical hydrodynamic parameters, which in turn has an impact on sediment and solute transport through the river system. In this study, we present results from three-dimensional

The ocean boundary layer (OBL) is forced by atmosphere-ocean and sea ice-ocean momentum fluxes, wave dynamics, and buoyancy; in coastal zones, OBL dynamics are further complicated by additional shear from the seafloor. Among numerous other phenomena, coastal mixing affects dispersion of anthropogenic quantities, erosion and turbidity, and benthic sequestration. In the OBL, interaction of wind-induced

Stratification effects induced by density differences between the incoming flows are investigated at a medium-size stream confluence with a highly discordant bed. The relatively large temperature difference ΔT = 4.7 °C between the main, high-discharge tributary and the low-discharge tributary together with the relatively small velocity of the flow in the main channel translate in a very high Richardson

The characteristics of large- and small-scale turbulent motions at roof-level in a street canyon flow were experimentally investigated along with their spatio-temporal organization and their mutual interaction in this region. Quadrant analysis was conducted to identify sweep and ejection events, whilst a spanwise spatial filter was used to identify the large-scale motions in the flow. The present analysis

Vegetation acts as a natural protection measure as it reduces inundation depth downstream of it and dissipates the energy of flow like flood and tsunami. The present study performed a series of laboratory experiments in which the flow variations and energy dissipation around discontinuous and vertically double layered vegetation (VDLV) were investigated with changing the vegetation density and water

From the viewpoint of improving the visibility of water in small lakes and ponds, in a previous study, we treated turbidity-causing (TC) particles and adsorption agents. Brownian dynamics simulations were conducted for particles with a spherical shape in order to elucidate the adsorption performance of the agents in the gravitational field. The technique for the adsorption is based on the use of the

A numerical procedure is proposed to estimate the velocity distribution in open channel flow, for engineering applications. A method based on the mixing length model and sub-division of the wetted surface, is modified to easily integrate a lateral distribution of roughness. Several friction models for vegetated or rough flows can be added, two of which have been tested. The numerical procedure was

This paper investigates the influence of near-bank vegetation patches on the bed morphological adjustment in open channel flow systems. The 2D depth-averaged hydro-morphological model is adopted for this investigation, which is first validated by laboratory experimental data measured in an open channel with a single near-bank vegetation patch. The validated model is then applied for extensive numerical

Bridges with and without piers are prone to large wood (LW) accumulations during floods, possibly resulting in an upstream backwater rise, local scour, or destabilization of the structure. To reduce the flood hazard, measures are required that decrease the accumulation probability p of LW. This paper presents a literature review on existing measures to reduce p at bridges. In addition, a series of

A round jet entering a counterflow with different jet-to-current velocity ratios and different offset ratios was experimentally investigated using particle image velocimetry. Turbulence characteristics, including axial and radial turbulence intensity, Reynolds stress, and skewness in the radial direction, were analyzed based on the measured data. When a round free jet enters a counterflow, the axial

The performance of a rake for large wood retention has been analysed in clean water and for the case of a slit check dam. An experimental investigation was conducted in a steep rectangular flume, by employing regular cylinders at different rates and rake geometry. The effects of the inclination and distance of the rake from the check dam have been analysed in terms of the trapping efficiency and backwater

Pedestrian level wind comfort, natural ventilation and pollutant dispersion are strongly influenced by building shape and orientation. In the recent years, the trend of building shape is not restricted to basic square and rectangular cross-section, and various unconventional shapes are also considered. Considering this fact, the present study is focused on the investigation of different building shape

The present study examines the turbulent flow characteristics in the vicinity of the leading edge of a vertical retaining wall structure embedded in a gravel bed. Conditions before and during the initial stages of local scour development were considered. To that end, three laboratory experiments were carried out: one with fixed boundaries as a reference case, a second one with an erodible bed, but

The paper addresses the influence of intense sediment transport (bed load and debris flow) on the efficiency of the structures aimed at the interception of wood logs. In the literature different devices designed to intercept woods are proposed: steel barriers, net barriers, check dam with steel bars positioned in the opening. In this paper we firstly define some fundamental dimensionless parameter

Numerical experiments of plane jets are performed to investigate their behaviour into a still ambient and into a flow field of regular waves. SPH simulations are obtained by a pseudo-compressible XSPH scheme with pressure smoothing; turbulent stresses are represented by a two-equation k-ε model. The SPH model is validated by comparing the obtained results with experimental measurements and analytical

The presence of floaters should be taken into account when dealing with hydraulic analyses, e.g. when boats are moored along the river banks or large wood is expected to be conveyed by the river flow during floods. Many approaches have been proposed so far in order to consider the effects of floaters upon the flow features. Usually, they rely on the numerical resolution of the governing equation for

Predicting the motion of driftwood around hydraulic structures such as bridge piers and spur dikes is important. We propose a numerical model for simulating driftwood motion that is based on coupling an Eulerian-type three-dimensional flow model and a Lagrangian-type two-dimensional driftwood model. Laboratory tests were carried out on the driftwood motion in a curved channel and around obstacles to

The blockage of weirs or bridges by in-stream wood can reduce the flood discharge capacity, leading to hazardous situations. To assess the related risk, blocking probabilities quantifications are needed. However, large wood has a random behaviour and it is challenging to accurately evaluate the blockage process and the influence of different large wood or hydraulic parameters properly. Investigations

In this note, Richards’ equation for two layered soils is considered in a two-dimensional spatial domain. It is endowed by pressure gradient and pressure condition at the top of domain, and no condition is posed at the bottom of domain. An existence and uniqueness result of strong solutions is obtained for such a problem assuming constant pressure gradient.

Turbulent flow through and over vegetation continues to draw significant research attention given its relevance to a plethora of applications in earth and environmental science. Canopy flows are characterized by three-dimensional coherent vortical motions not directly accessible from single-point measurements, which pose a challenge to formalizing links between vegetation structure and turbulent motion