Water Velocity Profiles Research Articles

Experimental and numerical study of the gated and ungated ogee spillway

This study was carried out by combining numerical modeling and experimental measurements to investigate the hydraulic characteristics of ungated and gated ogee spillways with high head ratios. The primary objective was to validate the use of a numerical model as a complementary approach to the experimental model for simulating the hydraulic behavior of these spillways, providing a more comprehensive understanding of their hydraulic properties under varying conditions of head ratios and relative gate openings. An Acoustic Doppler Velocimeter (ADV) was used to measure the vertical flow velocity distributions, and ultrasonic sensor wave gauges were used to obtain the time history of the water level. The results of the measurements were compared with the simulation results using a model fitted with three different turbulence models (realizable k-ε, RNG k-ε, k-ω SST). The numerical model was developed using OpenFOAM. With respect to the ungated spillway, three different head ratios ranging from 1.4 to 4.6, which correspond to high head ratios, were investigated. Similarly, three different relative gate openings ranging from 0.5 to 2 were investigated for the gated spillway. The results of water surface profiles and velocity profiles suggest that the numerical and experimental models achieve a good agreement for sections located further away from the spillway. For the ungated spillway, the simulation results for the near-spillway sections are enhanced when the head ratio increases. Considering the velocity profiles and error analysis, the realizable k–ε model was found to best predict the results of the experimental model. A discussion about the discharge equation, velocity fields, pressure fields, and the corner separation zone is also included in this study.

Analysis of particle dispersion and cavity formation during bulk particle water entry using fully coupled CFD-DEM-VOF approach

This paper presents the development and validation of a fully coupled computational fluid dynamics—discrete element method—volume of fluid (CFD-DEM-VOF) model to simulate the complex behavior of particle-laden flows with free surfaces. The coupling between the fluid and particle phases is established through the implemented continuity, momentum, and alpha transport equation. The coupled particle forces such as drag, pressure gradient, dense virtual mass, viscous, and interface forces are also integrated, with drag and dense virtual mass forces being dependent on local porosity. The integrated conservative alpha transport equation ensures phase volume conservation during interactions between particles and water. Additionally, we have implemented a trilinear interpolation method designed to operate on unstructured hexahedral meshes. This method has been tested for its ability to properly resolve the coupling effects in the numerical simulations, particularly in cases with a relatively low cell-size ratio. The model is validated through three distinct test cases: single particle water entry, dam break with particles, and water entry of a group of particles case. The experimental setup is built to study the dynamics of the water entry of a group of particles, where three key flow features are analyzed: the evolution of average particle velocity, cavity shape, and particle dispersion cloud profiles in water. The tests involve four different scenarios, including two different water levels (16.1 and 20.1 cm) and two different particle densities (2650 and 4000 kg/m3). High-speed videometry and particle tracking velocimetry (using ImageJ/TrackMate) methods are employed for experimental data acquisition. It is demonstrated that numerical results are in excellent agreement with theoretical predictions and experimental data. The study highlights the significance of vortices in cavity shaping and particle dispersion. The validated CFD-DEM-VOF model constitutes a robust tool for simulating particle-laden flows, contributing valuable insights into the complex interplay between particles and fluids.

A New Method for Modeling Effects of Surface Ice on Waves

Accurate prediction of ocean surface wave attenuation in polar marginal ice zones remains a challenge. In this article, an alternative approach to the problem is introduced, in which the ice layer is represented with a modified version of the vegetation damping parameterization in a phase-resolved wave model. The new representation is evaluated by comparison to theory and measured data under varied wave and ice conditions. Model-estimated profiles of RMS water velocity and Reynolds stress under ice layers with different drag coefficients are found to be qualitatively comparable to a range of nondimensional profiles computed using viscous layer theory. Modeled profiles appear somewhat vertically “stretched” relative to theoretical results, and in this respect, they more closely resemble measurements obtained during a recent wave–ice laboratory experiment. Estimated values of the wave attenuation coefficient and wavenumber in ice from the adapted model align well with theory and with a range of lab and field datasets. Several additional model ice parameters are available to facilitate a more nuanced representation of surface ice effects and will be investigated further in an upcoming companion study.

The Dynamics of the Oceanic Air-Sea Boundary Layer

This paper presents a model for the similarity structure of the velocity profiles in air and water in the wave boundary layer, which provides predictions in terms of two parameters, F and R, of all its important properties, including the Charnock parameter, the surface drift velocity and the condition for the cancellation of the surface Stokes velocity by the surface current. The parameter, F, arises from the fetch variability of the wave field, and the parameter, R, arises from the duration variability of the wave field. In the analysis two regimes emerge, namely the Ekman regime and the Hasselmann regime. In the Ekman regime, which occurs for R > ½(1 + F), there is a net loss of energy from the wave field to the deep ocean, and in the Hasselmann regime which occurs for R < ½(1 + F), there is a net gain of energy from the atmosphere to the wave field. The predictions are compared with observations from classical wave formulae, wind-wave studies, and also ROMS and SWAN modelling in the South Australian Basin. A general conclusion is that the condition, F = 1, which was used in the original inertial coupling model of Bye [1], is a good approximation for large scale theoretical ocean studies, and hence the wind-wave interaction is determined principally by R.

Temporal dynamics of lateral carbon export from an onshore aquaculture farm

Many coastal areas are hotspots of aquaculture expansion, where the overuse of artificial feeds results in the accumulation of organic carbon in nearshore aquaculture ponds. In rural areas, wastewater from the aquaculture ponds is discharged to the nearshore waters through artificial ditches causing lateral carbon export from the land to the ocean. Such flux may be meaningful in coastal carbon budgets since aquaculture is the hotspot of carbon sequestration and storage. To quantify the magnitude and temporal dynamics of lateral carbon export from aquaculture ponds, we used high-frequency in-situ monitoring of turbidity, fluorescent dissolved organic matter, etc. across different temporal scales. We measured water levels and velocity profiles in a ditch cross-section to obtain year-round water exchange. Carbon export was integrated from water fluxes and organic carbon concentrations. Our results suggested that aquaculture ponds were a source of particular organic carbon (POC) and dissolved organic carbon (DOC). The net lateral flux of POC and DOC was 148 ± 38 kg yr−1 and 296 ± 18 kg yr−1. Temporally, the export of POC and DOC is influenced by both tides and wastewater discharge. Under the disturbance with aquaculture wastewater discharge, the mean DOC export in the ditch increased by 497 kg, which was 1.5 times that of the undisturbed; the mean POC export increased by 190 kg, which was 1.8 times that of the undisturbed. Thus, aquaculture activities can considerably disturb the coastal carbon balance by facilitating carbon-rich fluid exchange from onshore farms to nearshore estuaries. As aquaculture expands across Asia and the globe, this study provides important insights into the impacts of aquaculture on coastal carbon budgets.

Molecular dynamics analysis of water flow through a multiply connected carbon nanotube channel

The filling process of nanoconduits is an active research topic. In this study, we use molecular dynamics simulations to identify the filling process of water molecules in a multiply connected carbon nanotube (MCCNT). For water permeation, a local change in the channel cross-section affects the water filling of MCCNTs because it may lead to irregularities in the permeation profile. A decrease in hydrogen bonds at the junctions of the structure characterizes the permeability of MCCNTs. In contrast to pristine CNTs, the complex nanochannel exhibits a different imbibition profile due to the energy changes at the junction. Next, we examine the local water density and velocity patterns in MCCNT channels to understand how junction regions affect steady-state water transport. We find that there is congestion and irregularities in steady water flow density and velocity profiles. Through this study, we expect to develop effective channels with more complex geometries for water purification and drug delivery.

Manyetik Alan Altinda Nanoakişkanlarin Akiş Karakteristiklerinin İncelenmesi

The existence/application of an externally induced magnetic field, like in satellite cooling applications, causes a decrement in heat transfer when used with nanofluids. This study investigates the flow characteristics and velocity profile of distilled water, alumina nanofluid, and cobalt ferrite ferrofluid in a horizontal cylindrical heat pipe flowing in a laminar regime and being exposed to an external magnetic field. All of the simulations were performed with ANSYS Fluent MHD module, for a concentration of 2%, Reynolds number of 10, and Hartmann numbers of 25, 50, and 150. The velocity profiles, pressure drops, and flow characteristics are examined by varying the magnetic field intensity while keeping all other parameters constant. It is concluded that an external magnetic field causes a deterioration in the velocity profiles of the nanofluid, especially in cobalt ferrite, while it does not have a significant effect on water. When the magnitude of the magnetic field is increased by 2 times, it is seen that the velocity of the fluid decreases by 6% and increasing the magnetic field from 0 to 50 Tesla causes a deceleration rate of 9%, which leads to the conclusion that application of a magnetic field for the first time has a more significant slowing effect when comparing it to increasing the magnetic field. In addition, when a magnetic field of 50 Tesla is considered, the maximum velocity of alumina is lower than that of water by 5.10%, and the maximum velocity of cobalt ferrite is lower by 28.57%.

Numerical study of sediment scour at meander flume outlet of boxed culvert diversion work.

BackgroundSediment scour at downstream of hydraulic structures is one of the main reasons threatening its stability. Several soil properties and initial input data have been studied to investigate its influence on scour hole geometry by both physical and numerical models. However, parameters of resistance affecting sedimentation and erosion phenomena have not been carried out in the literature. Besides, the auxiliary-like wing walls prevalently used in many real applications have been rarely addressed for their effect on morphological change.ResultsIn this study, a 3D Computational Fluid Dynamics model is utilized to calibrate the hydraulic characteristics of steady flow going through the culvert by comparison with experimental data, showing good agreement between water depth, velocity, and pressure profiles at the bottom of the boxed culvert. The results show that a grid cell of 0.015 m gave minimum NRMSE and MAE values in test cases. Another approach is numerical testing sediment scour at a meander flume outlet with a variety of roughness/d50 ratio (cs) and diversion wall types. The findings include the following: cs = 2.5 indicates the close agreement between the numerical and analytical results of maximum scour depth after the culvert; the influence of four types of wing wall on the geometrical deformation including erosion at the concave bank and deposition at the convex bank of the meander flume outlet; and two short headwalls represent the best solution that accounts for small morphological changes.ConclusionsThe influence of the roughness parameter of soil material and headwall types on sediment scour at the meander exit channel of hydraulic structure can be estimated by the numerical model.

Heat transfer of pulsating water flow through aluminum-foam channel under asymmetric constant heat flux boundary condition

In the present study, the effect of pulsating inlet velocity condition on heat transfer in metal foam was investigated experimentally. Square wave shaped water velocity profiles with different amplitudes and frequencies were applied to the inlet of a rectangular channel filled with aluminum foam having 20 pores per inch and a porosity of 91.8%. A constant heat flux (12787 W/m2) was applied to one side of the porous channel. The non-heated surfaces were insulated. The surface temperatures, water inlet and outlet temperatures and volumetric flow rates were measured and recorded. The dimensionless flow frequency parameter (M) and dimensionless flow amplitude (Rem) parameter were changed in the ranges 4.8–7.3 and 492–1388, respectively. The results showed that there was a strong relationship between average Nusselt number and flow velocity amplitude. Generally, average Nusselt number was seen to increase with increasing frequency parameter and/or amplitude parameter. Correlations for the local time-averaged and surface-averaged Nusselt numbers are proposed. A meaningful comparison between steady-state and pulsating heat transfer is provided. It showed that heat transfer advantages of pulsating flow were only present for a certain low range of Reynolds number, beyond which pulsating flow heat transfer approached that of steady state.

Field observations of stratification in stormwater wet ponds

Stratification is one of the fundamental physical processes that may have a significant impact on water quality in stormwater wet ponds. However, the role of thermal and chemical stratifications in governing water quality processes is not fully understood. This is in part due to the lack of detailed field measurements of sufficient governing parameters over time periods that span a wide range of environmental conditions. To fill this gap, a comprehensive 2-year field program was undertaken in two stormwater wet ponds in Calgary, Alberta, Canada, during the ice-free season from May to November in 2018 and 2019. At different locations in each pond, thermal and chemical stratifications were observed, thermocline depth and strength were determined, and continuous water velocity profiles were measured. In addition, the effect of local weather conditions on stratification, thermocline, and hydrodynamics was investigated. The results showed that the ponds had vertical water temperature differences >1 °C for 99% of the time, May to August. In addition, salt-laden inflows from road deicing salts led to strong chemical stratification up to five times stronger in the sediment forebays than in the main cells in spring. Wind-induced surface currents were insignificant, scaling at 0.3% of the wind speed with negligible impact on vertical mixing in the ponds. Our results demonstrate that the ponds' strong and prolonged stratification decreased pollutant retention capacity and caused the water at depth to become anoxic, degrading the quality of the water discharged downstream. Hence, additional consideration of stratification is required when designing new stormwater ponds.

Effect of rigid, bank vegetation on velocity distribution and water surface profile in open channel

Abstract The effects of rigid ditch bank vegetation on velocity distribution and water surface profile in trapezoidal open channels were investigated. Forty-eight tests were used to study the impacts of different vegetation densities. Tests were run for three vegetation densities (1,600, 400, and 178 stems/m2) along a fixed, 4.00 m reach, against four different discharges, each with three different depths. The measured water levels and velocities were analyzed and it was found that increasing the vegetation density increased the water depth upstream of the vegetated reach. while lowering it within it, when compared to the unvegetated case. The water's velocity profile as a ratio to the unvegetated case (V/u) is sigmoid, i.e., the maximum velocity (V/u) max occurs in the lower half of the water column, increasing shear stress near the bed, and, in turn, the likelihood of bed erosion along the vegetated channel's centerline. V/u increased with increasing vegetation density and Fro. A multiple regression analysis was done to assess the impact of ditch bank vegetation density on flow parameters.

Numerical Study of The Effect of Penstock Dimensions on a Micro-hydro System using a Computational Fluid Dynamics Approach

The performance of a micro-hydro system needs always to be improved so that the electrical power produced can be more optimal. This article aims to study numerically the effect of penstock dimensions on the potential of electrical energy in a micro-hydro system using a computational fluid dynamics (CFD) approach. The study of the effect of dimensions on the performance of a hydropower system is still quite rare. In this paper, the impact of dimensions on the micro-hydro system has been analysed by constructing thirty simulations of water flow in the penstock consisting of five variations of penstock slope ( and ) for six penstock diameter variations ( m, m, m, m, m, and m). The simulation was built using the open-source CFD software OpenFOAM which applies the finite volume method to solve the Navier-Stokes equation as a flow model. The simulated water velocity profile is then validated against the velocity profile of the analytical solution (power-law) for turbulent flow in the pipe. Energy loss analysis on the penstock has been carried out to determine the cause of the energy loss in the penstock characterised by loss coefficient . An enormous value will impact the decrease in the electric power potential of a micro-hydro system. The total length of the penstock induces the variation of the which affects the changes in the electrical power of the micro-hydro system. The shorter will increase the electric power potential of a micro-hydro system. With a high flow velocity of water in the penstock ( m/s), the electric power increases linearly with increasing the diameter value of the penstock. The analysis results show that the penstock dimensions can affect the changes in the electric power of the micro-hydro system. In addition, the work presented in this article has shown that the CFD approach can be used as a low-cost initial step in building an actual micro-hydro system

Numerical investigation of the effect of geometric parameters on discharge coefficients for broad-crested weirs with sloped upstream and downstream faces

Weirs are structures that are important for measuring flow and controlling water levels. Research has shown that the discharge coefficient is not constant and depends on the crest length, the height of the weir, the upstream head, and the upstream and downstream slopes. In this study, the effect of these parameters on the discharge coefficient (Cd) is investigated by numerical simulation. The current study present numerical simulation using the ANSYS FLUENT software. The total number of simulations is 432 which includes: 4 upstream slopes, 4 downstream slopes, 3 weir heights, 3 upstream heads (h1) and 3 weir crest lengths. It was found that the downstream face slope has little effect on Cd. For 0.1 < H1/w < 0.4 by decreasing the upstream slope, Cd increases, where H1 is the water head on the weir crest and w is the length of the crest. Also, for the same range, by decreasing the height of the weir (p), the Cd increases. For 0.16 < H1/p < 2, as the length of the crest decreases, the Cd increases. By comparing the numerical simulation results to physical measurements, multi-variable regression equations for estimating Cd are presented. In addition to Cd, extraction of other more detailed information such as water level profiles and velocity profiles at different locations is provided.

Analysis of water velocity changes in time-lapse ocean bottom acquisitions - A synthetic 2D study in Santos Basin, offshore Brazil

Time-lapse seismic is an important tool for reservoir management. As seismic data quality improves, there is a drive for moving towards quantitative interpretation, which demands data of higher repeatability. In deep water time-lapse projects, the changes in the speed of sound of the water layer between baseline and monitor acquisitions play a significant role in the data processing. In this work, we study the effects of these water velocity changes, in a scenario of ocean bottom nodes (OBN) acquisition. We perform 2D elastic seismic modeling with high-resolution property models for two distinct survey dates. In each date, different water velocity profiles, measured in field experiments in a Brazilian Pre-salt area, are considered. To incorporate source and receiver non-repeatability, some differences in the acquisition geometries are also tested for each vintage. The synthetic data are compared in terms of time-lapse amplitudes, and repeatability is quantified via the normalized root mean squared attribute (NRMS). For the parameters considered in our study, the deterioration of NRMS seems to be dominated by the non-repeatability of the receivers and by water velocity variations, with source non-repeatability having a lower contribution. We believe the results presented in this work are a first step towards a more robust methodology for time-lapse feasibility studies, which incorporates imaging uncertainties and allows us to understand the contribution of each element that could affect the 4D seismic image quality.

Experimental study on wave-in-deck loading under focused wave conditions

This paper presents experimental results related to the wave-in-deck phenomena caused by focused waves. A series of experiments were conducted in a two-dimensional wave flume using varying deck clearances and focused waves with varying wave crest heights to measure the water velocity profiles, vertical forces, and pressure distributions under the deck. The velocity fields of the water under the deck were obtained using the particle image velocimetry (PIV) system, which was synchronized with the force and pressure measurement systems. The linear momentum and kinetic energy with and without the deck were calculated from the PIV velocity maps. The velocity profiles, linear momentum, and kinetic energy of the water under the deck were compared with those of the incident focused waves to investigate the effect of the deck on the water kinematics in relation to the force and pressure measurements recorded during the loading process. Meanwhile, the forces and pressure caused by the focused waves were compared with those caused by regular waves, and the results indicated that the upward vertical force and pressure caused by the focused waves were larger than those caused by the regular waves but that the downward force exhibited an opposite behavior. Based on the force measurements, the peak and impulse of the vertical force indicated negative linear relationships with the deck clearance, whereas the wave crest height was found to have a less significant effect on the vertical force than the deck clearance. The distribution of the peak pressure along the deck was analyzed in terms of the corresponding impulsiveness and pressure impulse to evaluate the severity of the local wave loads, and the results indicated that the region near the leading edge would likely experience a greater structural damage due to the wave-in-deck load compared with the region near the trailing edge.

Hydrodynamic Modeling of Oil–Water Stratified Smooth Two-Phase Turbulent Flow in Horizontal Circular Pipes

In the petrochemical industry, multiphase flow, including oil–water two-phase stratified laminar flow, is more common and can be easily obtained through mathematical analysis. However, there is limited mathematical analytical model for the simulation of oil–water flow under turbulent flow. This paper introduces a two-dimensional (2D) numerical simulation method to investigate the pressure gradient, flow field, and oil–water interface height of a pipeline cross-section of horizontal tube in an oil–water stratified smooth flow. Three Reynolds average N–S equation models (k−ε, k−ω, SST k−ω) are involved to simulate oil–water stratified smooth flow according to the finite volume method. The pressure gradient and oil–water interface height can be computed according to the given volume flow rate using the iteration method. The predicted result of oil–water interface height and velocity profile by the model fit well with several published experimental data, except that there is a large error in pressure gradient. The SST k−ω turbulence model appears higher accuracy for simulating oil–water two-phase stratified flow in a horizontal pipe.

Prediction of velocity profile of water based copper nanofluid in a heated porous tube using CFD and genetic algorithm

The heat transfer improvements by simultaneous usage of the nanofluids and metallic porous foams are still an attractive research area. The Computational fluid dynamics (CFD) methods are widely used for thermal and hydrodynamic investigations of the nanofluids flow inside the porous media. Almost all studies dedicated to the accurate prediction of the CFD approach. However, there are not sufficient investigations on the CFD approach optimization. The mesh increment in the CFD approach is one of the challenging concepts especially in turbulent flows and complex geometries. This study, for the first time, introduces a type of artificial intelligence algorithm (AIA) as a supplementary tool for helping the CFD. According to the idea of this study, the CFD simulation is done for a case with low mesh density. The artificial intelligence algorithm uses learns the CFD driven data. After the intelligence achievement, the AIA could predict the fluid parameters for the infinite number of nodes or dense mesh without any limitations. So, there is no need to solve the CFD models for further nodes. This study is specifically focused on the genetic algorithm-based fuzzy inference system (GAFIS) to predict the velocity profile of the water-based copper nanofluid turbulent flow in a porous tube. The most intelligent GAFIS could perform the most accurate prediction of the velocity. Hence, the intelligence of GAFIS is tested for different values of cluster influence range (CIR), squash factor(SF), accept ratio (AR) and reject ratio (RR), the population size (PS), and the percentage of crossover (PC). The maximum coefficient of determination (~ 0.97) was related to the PS of 30, the AR of 0.6, the PC of 0.4, CIR of 0.15, the SF 1.15, and the RR of 0.05. The GAFIS prediction of the fluid velocity was in great agreement with the CFD. In the most intelligent condition, the velocity profile predicted by GAFIS was similar to the CFD. The nodes increment from 537 to 7671 was made by the GAFIS. The new predictions of the GAFIS covered all CFD results.

Numerical Study of Discharge-Head Relationship of Piano Key Weirs for Low Heads

Piano Key Weirs (PKW) is a free-flowing weir, and an improvement over the labyrinth weir family. PKW has higher discharge for the same head as compared to other types of weirs. They tend to reduce the upstream submergence in reservoirs or other flow systems and can be effectively used for flood risk mitigation. CFD studies have been carried out earlier but mostly for H/P (Total head to height ratio) greater than 0.1. The present paper investigates the use and validation of Computational Fluid Dynamics (CFD) for modeling Open Channel flows over common hydraulic structures such as PKW for small discharges with the entire range of head to height ratio h/P from 0.035 to 0.1, where h is not the total head upstream of PKW but the head measured at the crest of PKW. The numerical results have been validated with experimental results. Since the discharge is minimal surface tension force has been incorporated in the numerical model. The numerical model is a half PKW unit model with the same geometrical parameters as the experimental setup from Literature. The results show that CFD simulations can reproduce flow depths near PKW with reasonably good accuracy. The present paper compares the head obtained from CFD with that of empirical formula in the Literature but with head measured at the crest of PKW. Investigation of water surface profile and velocity profile near the upstream of PKW has also been carried out.

A Study on the accuracy of finite volume numerical models with non-rectangular mesh

During numerical simulation of complex geometries and flow depth variations, non-rectangular computational cells are to be generated. However, application of this kind of mesh cause numerical errors. A 3-D model, which was verified and validated before, was used to illustrate the problem in a simple open channel flow. A zigzag computational mesh was used to study the effect of non-rectangular cells on the accuracy of the model. Results showed that water surface and velocity profiles oscillated around the correct answer. Investigating the reason for this oscillation showed that assuming constant velocity at non-rectangular computational cell surfaces, which is a usual practice in all numerical schemes, cause this error. Variation of velocity at mesh surfaces was then added to the computation model and as a result, the oscillations in velocity profiles and water surface were eliminated. Further analysis showed that this is a general problem in any finite volume model with non-rectangular mesh.

The sedimentation datasets of Keuliling reservoir.

Sedimentation is commonly found as one of the problems affecting the function of reservoirs in Indonesia. High risk soil erosion leads to the increase in sediment production which negatively influencing the capacity or functional age of the reservoir. Generally, several reservoirs in Indonesia are experiencing the operational problem due to the increasing of sedimentation throughout the year. The data presented in this article was obtained from the measurement of sediment in the area of Keuliling reservoir, including: The data of suspended sediment at every Keulling reservoir water inlet, the data of bedload sediment at the bottom of the Keuliling reservoir, the hydrometric data, including the water velocity and channel profile, where the sampling of bedload and suspended sediment sampling was conducted at each inlet. the data sediment volume at the dam reservoir. The data of suspended and bedload sediment were obtained by taking the samples and analyzed in a laboratory. The measurement was conducted three times in five months. The data of water velocity was also generated based on the measurement using a currentmeter. Meanwhile, the sediment volume data in the water storage of reservoir was gathered by conducting a bathymetry and topographic survey at the dam reservoir location and then comparing it with the pre-existing bathymetry and topographic data.