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The freshwater transport (FWT) by the Labrador Current (LC) around the Grand Banks of Newfoundland (GBN) is diagnosed with the 26-year Global Ocean Physical Reanalysis 1/12° data (GLORYS12v1) during 1993 - 2018. The time-mean FWT of the LC above the 1027.25 kg/m3 isopycnal surface is 83.6 mSv (1 mSv = 103m3/s) southward through the Flemish Pass. Among this 83.6 mSv, 42% (35.2 mSv) is exported into the interior of the North Atlantic along the whole pathway of the LC from the Flemish Pass to the Tail of the GBN, with 25.5 mSv by the mean advection and 7.2 mSv by the mesoscale eddy transport. The seasonal and inter-annual variations of the FWT in the east of the GBN are mainly caused by the variation of the horizontal velocity of the LC, and the variation of salinity makes a nontrivial contribution to the variation of the FWT to the north of 45°N. Around the Tail of the GBN, the mesoscale eddies make significant contributions to the time-mean FWT and the seasonal and inter-annual variations of the FWT.

In this paper, we present the results of numerical simulations matched to laboratory experiments of tidal, starting-jet vortices forming at idealized, barotropic inlets. The laboratory experiments are for sinusoidally varying inflow/outflow along a wide, flat basin. Inlet configurations include simple inlets with negligible channel length as well as a longer inlet channels through a long barrier island and jettied inlet. Laboratory observations are made using particle image velocimetry, and we analyze the laboratory and numerical model velocity fields to compare starting-jet trajectory, diameter, and total circulation. The numerical simulations use the Fine Resolution Environmental Hydrodynamic model, solving the three-dimensional, hydrostatic, barotropic equations of motion. Our goal is to identify the minimum model attributes necessary to match the vortex properties. This is accomplished using a third-order upwind scheme for advection, a constant bottom friction drag coefficient, and a one-equation turbulence model for transport of turbulent kinetic energy. The optimal value of the bottom drag coefficient matches the time-average value at the basin inflow/outflow boundaries, and the optimal dissipation coefficient, $$C_{me}$$, was an order of magnitude smaller than literature values for a steady open-channel flow. We show that the drag coefficient mainly affects the advection speeds of the outer coastal waters, which control the penetration of the tidal vortices away from the inlet, and the lower turbulence dissipation rate results from the low turbulent dissipation in the large, shallow starting-jet vortices.

We developed an integral plume model to simulate the behavior of bubble plumes generated from line-source geometry in stratified ambient reservoirs by adapting the double-plume integral mod...

This paper presents a set of stereoscopic particle image velocimetry (SPIV) measurements of a turbulent round water jet (jet exit Reynolds number $$Re = 2679$$ and turbulent Reynolds number $$Re_T = 113$$ ) discharged into an initially stationary ambient. The data were taken on the jet centerplane and at non-dimensional downstream distances $$x/D = 27{-}37$$ ( $$x =$$ axial coordinate and $$D =$$ orifice diameter), where the jet turbulence had evolved into a self-preserving state. Budgets of turbulent kinetic energy k and individual components of the Reynolds stress tensor $$R_{ij}$$ are extracted from the velocity measurements and compared to recent experimental data of an air jet ( $$x/D = 30, Re = 140{,}000$$ ) and direct numerical simulation data ( $$x/D = 15, Re = 2000$$ ). The comparison reveals that the datasets are consistent with each other but that the turbulent transport of energy $$\overline{u^2_i}$$ appears to differ between the present low-Re water jet and the high-Re air jet. Nonetheless, the non-dimensional profile of turbulent dissipation rate $${\overline{\epsilon }}$$ , obtained as the closing term (balance) of the k-budget, is very similar in all studies. The commonly used Lumley’s model for pressure–velocity correlation (pressure transport term in k-budget) is evaluated using the instantaneous pressure field computed from the time-resolved planar velocity data. We find that Lumley’s model is deficient in the jet core $$|r/b_g| < 0.3$$ ( $$r =$$ radial coordinate and $$b_g =$$ Guassian half-width), while performing adequately away from it. Finally, the present data are used to compute terms appearing in the exact transport equation of $${\overline{\epsilon }}$$ . Combining both the k and $${\overline{\epsilon }}$$ budgets, model coefficients in the commonly used two-equation $$k-{\overline{\epsilon }}$$ turbulence closure model are evaluated from the present data. If a fixed set of model coefficients is to be employed in a jet simulation, the following values of the model coefficients are recommended to optimize predictions for the mean flow field, for k, and for $${\overline{\epsilon }}$$ : $$C_{1\epsilon } = 1.2, C_{2\epsilon } = 1.6, C_{\mu } = 0.11, \sigma _k = 1.0$$ and $$\sigma _\epsilon = 1.3$$ .

Hypolimnetic oxygenation is an increasingly common lake management strategy for mitigating hypoxia/anoxia and associated deleterious effects on water quality. A common effect of oxygenation is increased oxygen consumption in the hypolimnion and predicting the magnitude of this increase is the crux of effective oxygenation system design. Simultaneous measurements of sediment oxygen flux (JO2) and turbulence in the bottom boundary layer of two oxygenated lakes were used to investigate the impact of oxygenation on JO2. Oxygenation increased JO2 in both lakes by increasing the bulk oxygen concentration, which in turn steepens the diffusive gradient across the diffusive boundary layer. At high flow rates, the diffusive boundary layer thickness decreased as well. A transect along one of the lakes showed JO2 to be spatially quite variable, with near-field and far-field JO2 differing by a factor of 4. Using these in situ measurements, physical models of interfacial flux were compared to microprofile-derived JO2 to determine which models adequately predict JO2 in oxygenated lakes. Models based on friction velocity, turbulence dissipation rate, and the integral scale of turbulence agreed with microprofile-derived JO2 in both lakes. These models could potentially be used to predict oxygenation-induced oxygen flux and improve oxygenation system design methods for a broad range of reservoir systems.

Following the 2010 Deepwater Horizon accident of a massive blow-out in the Gulf of Mexico, scientists from government, industry, and academia collaborated to advance oil spill modeling and share best practices in model algorithms, parameterizations, and application protocols. This synergy was greatly enhanced by research funded under the Gulf of Mexico Research Initiative (GoMRI), a 10-year enterprise that allowed unprecedented collection of observations and data products, novel experiments, and international collaborations that focused on the Gulf of Mexico, but resulted in the generation of scientific findings and tools of broader value. Operational oil spill modeling greatly benefited from research during the GoMRI decade. This paper provides a comprehensive synthesis of the related scientific advances, remaining challenges, and future outlook. Two main modeling components are discussed: Ocean circulation and oil spill models, to provide details on all attributes that contribute to the success and limitations of the integrated oil spill forecasts. These forecasts are discussed in tandem with uncertainty factors and methods to mitigate them. The paper focuses on operational aspects of oil spill modeling and forecasting, including examples of international operational center practices, observational needs, communication protocols, and promising new methodologies.

Laboratory studies of tidal vortex formation and propagation through an idealized inlet configuration are presented for various water depths over flat bathymetry. Using surface particle ima...

We present the development and validation of a numerical modeling suite for bubble and droplet dynamics of multiphase plumes in the environment. This modeling suite includes real-fluid equations of state, Lagrangian particle tracking, and two different integral plume models: an Eulerian model for a double-plume integral model in quiescent stratification and a Lagrangian integral model for multiphase plumes in stratified crossflows. Here, we report a particle tracking algorithm for dispersed-phase particles within the Lagrangian integral plume model and a comprehensive validation of the Lagrangian plume model for single- and multiphase buoyant jets. The model utilizes literature values for all entrainment and spreading coefficients and has one remaining calibration parameter $$ \kappa $$ , which reduces the buoyant force of dispersed phase particles as they approach the edge of a Lagrangian plume element, eventually separating from the plume as it bends over in a crossflow. We report the calibrated form $$ \kappa = [(b - r) / b]^4 $$ , where b is the plume half-width, and r is the distance of a particle from the plume centerline. We apply the validated modeling suite to simulate two test cases of a subsea oil well blowout in a stratification-dominated crossflow. These tests confirm that errors from overlapping plume elements in the Lagrangian integral model during intrusion formation for a weak crossflow are negligible for predicting intrusion depth and the fate of oil droplets in the plume. The Lagrangian integral model has the added advantages of being able to account for entrainment from an arbitrary crossflow, predict the intrusion of small gas bubbles and oil droplets when appropriate, and track the pathways of individual bubbles and droplets after they separate from the main plume or intrusion layer.

This paper presents laboratory experiments of wave-driven hydrodynamics in a three-dimensional laboratory model of constructed coastal wetlands. The simulated wetland plants were placed on the tops of conically-shaped mounds, such that the laboratory model was dynamically similar to marsh mounds constructed in Dalehite Cove in Galveston Bay, Texas. Three marsh mounds were placed in the three-dimensional wave basin of the Haynes Coastal Engineering Laboratory at Texas A&M University, with the center of the central wetland mound located in the center of the tank along a plane of symmetry in the alongshore direction. The experiments included two water depths, corresponding to emergent and submerged vegetation, and four wave conditions, typical of wind-driven waves and ocean swell. The wave conditions were designed so that the waves would break on the offshore slope of the wetland mounds, sending a strong swash current through the vegetated patches. Three different spacings between the wetland mounds were tested. To understand the effects of vegetation, all experiments were repeated with and without simulated plants. Measurements were made throughout the nearshore region surrounding the wetland mounds using a dense array of acoustic Doppler velocimeters and capacitance wave gauges. These data were analyzed to quantify the significant wave height, phase average wave field and phase lags, wave energy dissipation over the vegetated patches, mean surface water levels, and the near-bottom current field. The significant wave height and energy dissipation results demonstrated that the bathymetry is the dominant mechanism for wave attenuation for this design. The presence of plants primarily increases the rate of wave attenuation through the vegetation and causes a blockage effect on flow through the vegetation. The nearshore circulation is most evident in the water level and velocity data. In the narrowest mound spacing, flow is obstructed in the channel between mounds by the mound slope and forced over the wetlands. The close mound spacing also retains water in the nearshore, resulting in a large setup and lower flows through the channel. As the spacing increases, flow is less obstructed in the channel. This allows for more refraction of waves off the mounds and deflection of flow around the plant patches, yielding higher recirculating flow through the channel between mounds. An optimal balance of unobstructed flow in the channel, wave dissipation over the mounds, and modest setup in the nearshore results when the edge-to-edge plant spacing is equal to the mound base diameter.

Tidal vortices play an important role in the flushing of coastal regions. At the mouth of a tidal inlet, the input of circulation by the ebb tide may force the formation of a starting-jet dipole vortex. The continuous ebb jet current also creates a periodic sequence of secondary vortices shed from the inlet mouth. In each case, these tidal vortices have a shallow aspect ratio, with a lateral extent much greater than the water depth. These shallow vortices affect the transport of passive tracers, such as nutrients and sediment from the estuary to the ocean and vice versa. Field observation of tidal vortices primarily relies on ensemble averaging over several vortex events that are repeatable in space and can be sampled by a fixed Eulerian measurement grid. This paper presents an adaptive approach for locating and measuring within tidal vortices that propagate offshore near inlets and advect along variable trajectories set by the wind-driven currents. A field experiment was conducted at Aransas Pass, Texas to measure these large-scale vortices. Locations of the vortices produced during ebb tide were determined using near real-time updates from surface drifters deployed near or within the inlet during ebb tide, and the paths of towed acoustic Doppler current profiler (ADCP) transects were selected by analysis of the drifter observations. This method allowed ADCP transects to be collected within ebb generated tidal vortices, and the paths of the drifters indicated the presence of both the starting-jet dipole and the secondary vortices of the unstable ebb tidal jet. Drifter trajectories were also used to estimate the size of each observed vortex as well as the statistics of relative diffusion offshore of Aransas Pass. The field data confirmed the starting-jet spin-up time (time until the vortex dipole begins to propagate offshore) measured in the laboratory by Bryant et al. [6] and that the Strouhal condition of $$St=0.2$$ predicts the shedding of secondary vortices from the inlet mouth. The size of the rotational core of the vortex is also shown to be approximated physically by the inlet width or by $$0.02UT$$ , where U is the maximum velocity through the inlet channel and T is the tidal period, and confirms results found in laboratory experiments by Nicolau del Roure et al. [23]. Additionally, the scale of diffusion was approximately 1–15 km and the apparent diffusivity was between 2–130 $$m^2/s$$ following Richardsons law.

This paper presents a surface particle image velocimetry study to investigate the dynamics of shallow starting-jet dipoles formed by tidal flow through inlets and their interaction with vorticity formed at the inlet channel lateral boundaries. Vortical structure in the flow field is identified using a local swirl strength criterion evaluated from the two-dimensional flow field. The starting jet dipole vortices and vortices formed as the lateral boundary layers are expelled during flow reversal are characterized by their trajectory, size, and circulation. Using these quantities, a model is developed to predict the size and strength of the expelled lateral boundary layer vortices based on the inlet velocity, channel length, and width of the lateral boundary layer. The expelled boundary layer vortices are found to disrupt the formation of the primary tidal jet dipole through two mechanisms. First, because the boundary layer vortices themselves form a dipole with each half of the starting-jet dipole, the starting-jet vortices are pulled apart and advected away from the inlet mouth early in the tidal cycle, resulting in a reduction in the spin-up time and the amount of vorticity input during starting-jet vortex formation. Second, the advection of each dipole away from the inlet disconnects each starting-jet vortex from the starting jet; hence, the vortices are not fed by fluid in the jet or energized by shear in the jet boundary layers. These influences of the lateral boundary layer on the starting-jet vortices’ formation and propagation are found to be a function of the channel length L, maximum velocity U, and tidal period T, resulting in a predictive value to characterize their trajectory, strength, and evolution.

Flow properties of a bubble plume in density-stratified conditions are studied using planar laser-induced fluorescence (PLIF) flow visualization. Entrained ambient fluid is identified by applying an image intensity threshold to the PLIF images of passive dye tracer injected at the bubble diffuser. The density stratification gradually arrests the entrained ambient fluid, causing detrainment, or peeling, of the continuous phase fluid from the bubble plume core and intrusion of the detrained fluid at a level of neutral buoyancy; bubbles continue to rise above each detrainment zone. The peel and intrusion heights for the first detrainment event above the diffuser are measured from the thresholded PLIF images. The nondimensional frequency of fluctuations in the detrainment and intrusion heights fz/ us is measured as 0.35 (where f =frequency; z =height above the diffuser; and us =terminal rise velocity of the bubbles in a quiescent fluid), and this value compares well to the plume wandering frequency for simila...

A method to identify and track rainfall structures using 1-h accumulated NEXt generation RADar (NEXRAD) rainfall data is presented and used to analyze the dynamics of storm features over an area in Texas. Storm features are identified from a Gaussian mixture model using the expectation maximization algorithm. The method assigns NEXRAD pixels to storm features, simultaneously producing a smooth fitted function to the rainfall intensity distribution. Once the storm features are identified, they are tracked using inverse cost functions and using the fact that continuous features overlap each other from frame to frame in the accumulated data. The inverse cost functions also account for storm feature merging, splitting, birth, and death. Application of this storm identification and tracking algorithm for Brazos County (1,500 km2 ) in southeastern Texas distinguishes several characteristics of the storm feature dynamics. From September through April, storm features are predominantly of a frontal nature, with st...

We present the results of a double-plume integral model for a positively buoyant multiphase plume of liquid carbon dioxide injected at mid-depths (500–2000 m) in the ocean. In addition to the relevant plume physics, the model accounts for dissolution of the carbon dioxide droplets, the effect on dissolution of clathrate hydrate films, and the increase in seawater density due to enrichment by dissolved carbon dioxide. Due to the creation of negative buoyancy in the entrained fluid through dissolution of carbon dioxide, the near-field mixing exhibits a complex set of energetic descending outer plume structures that do not converge to a steady state. The unsteady near field is shown to be inherent in the plume physics, resulting in enhanced distribution of the dissolved carbon dioxide over the plume height and formation of multiple, unsteady intrusion layers. Despite the complex plume near field, we demonstrate that the height of maximum plume rise has a steady solution. A general empirical design equation f...

We present a generalized integral model for multiphase plumes in stratified ambient conditions based on the double-plume approach, where the plume is composed of a rising, multiphase core plume surrounded by a counterflowing outer ring plume of dense fluid. The generalized model captures as limiting cases the current approaches in the literature, including two-fluid and mixed-fluid equations, continuous and discrete detrainment, dispersed-phase mass transfer, and two models for entrainment in the counterflow region. These modeling approaches are compared and validated against both laboratory and field-scale data. In unstratified conditions, all model formulations perform equally well. In stratification, entrainment in the counterflow region is best represented by correlation to the inner plume velocity instead of the difference between the inner and outer plume velocities. The vertical distribution of the exchange between the inner and outer plumes in the models differs from that measured in the prototype due to enhanced entrainment at the detrainment zone and forced entrainment from the collapsing intrusion layer. Nonetheless, the models predict well the length scales and volume fluxes at the detrainment zone and intrusion layer. Applications are demonstrated for reservoir air bubble plumes. The mass transfer and near-field mixing in the double-plume integral model prove sufficiently accurate to predict the depth of maximum plume rise (both the locations of total dissolution of the bubbles and the maximum height of the decelerating plume) and the volume flux, dissolved constituent mass flux, and trap height of the intrusion.

A method to disaggregate daily rainfall into hourly precipitation is evaluated across Texas. Based on measured precipitation data, the method generates disaggregated hourly hyetographs that match measured daily totals by selecting storm intensity patterns from measured hourly databases using a one parameter selection method. The model is applied across Texas using historic data measured at hourly precipitation gauges; performance is evaluated by the model's ability to reproduce the measured hourly rainfall statistics at each gauge. Initially, each hourly precipitation gauge is evaluated in its performance as a disaggregation database. Based on a cluster analysis of the results to determine which precipitation databases should be used for general disaggregation, no preferences in space or among gauge characteristics e.g., period of record, precipitation statistics were identified. As a result, a Texas state database that contains all of the measured hourly data in Texas is proposed for use by the disaggregation algorithm. The state database is verified for a selection of gauges across Texas and performed as well at a given station as using that station's measured rainfall for the disaggregation. The method is further applied to estimate intensity-duration curves, which show that the disaggregation algorithm captures the majority of the storm intensities well and diverges by less than 17% from the measured intensities for the extreme runoff-generating events.

Laboratory experiments are presented that model the exchange processes between a river and dead-water zones created by groin fields. The measurement methods include particle image velocimetry (PIV) at the water surface to capture the dynamics of the flow field as well as planar concentration analysis (PCA) to determine the depth integrated mass fluxes of dissolved tracer. Idealized groins with variable length-to-width ratios and inclination angles relative to the flow direction are investigated. Two-dimensional large coherent structures (2DLCS) are found in the mixing layer between the groin field and the river, and these flow structures control the majority of mixing with the main stream. The PIV data allow quantification of the turbulence intensity distribution in these structures throughout the groin field and mixing region. The PCA data provide measurements of the exchange rate between the groin field and the main stream. Both methods give comparable measures of the entrainment coefficient for the exchange flow. The entrainment coefficient is found to depend on the groin field hydraulic radius (a measure of the average size of 2DLCS in the mixing layer) and the water depth (a parameter controlling the stability of the shallow water flow). These data provide a link between the exchange parameter in groin field dead zones and the river properties that can be used to efficiently develop river alarm models to predict contaminant transport without requiring a large amount of field dye studies for calibration.

This paper presents direct measurements of multiphase plumes in stratification and correlates characteristic plume properties with the nondimensional slip velocity UN . UN is defined as the ratio of the bubble slip velocity us to a characteristic plume fluid rise velocity (BN)1∕4 ; B is the total kinematic buoyancy flux, and N is the buoyancy frequency. UN is derived by dimensional analysis and is compared to other nondimensional parameters for multiphase plumes in the literature. To investigate correlations of the nondimensional numbers with plume properties, laboratory experiments were conducted in linear stratification using dispersed phases of air, oil, and glass beads (creating an inverted plume). A new type of plume behavior is identified, called Type 1* , in which the horizontal motion in the first detrainment event disperses the relatively weak bubbles, creating a diffuse bubble plume that forms out of the intrusion. Measurements from these and previous experiments for type behavior, trap height, ...

This paper presents an optimization scheme to estimate the internal entrained fluid fluxes for multiphase plumes in stratification from indirect experimental measurements and applies the results to field-scale plumes. Experiments were conducted in linear stratification using dispersed phases of air bubbles and glass beads (the latter creating an inverted plume). Comparison of pre- and postexperiment salinity profiles provided direct measurements of the net liquid fluxes in the plume; fluorescence profiles provided direct measurements of the fluxes of passive tracer. To separate the net flux measurements into upward and downward flows this paper applies a constrained Bayesian estimation technique based on a conceptual model of the plume. This method provides estimates of the ambient and counterflowing entrained fluid fluxes, the peeling efficiency (percent of entrained fluid that detrains) and the buoyancy flux continuing above the first peel. These quantities correlate with the non-dimensional slip veloci...

Laboratory experiments of multiphase plumes in uniform and stratified crossflows are presented. In uniform crossflow, multi-phase plumes behave as mixed single-phase plumes up to a critical height, h s, where the entrained fluid separates from the dominant dispersed phase. From the experimental results, an empirical relationship for h s was calibrated giving u ∞ /(B/s ) 1/3 =6.3(us/(B/hs )1/3)-2.4, where u ∞ is the crossflow velocity, B is the total kinematic buoyancy flux of the mixed plume, and u s is the slip velocity. Above h s the separated continuous-phase plume behaves like a momentum jet and the bubble column follows the trajectory of the vector sum of u s and u ∞ In stratified crossflow. the trap height in quiescent water, h T, was compared to h s. For h T « h s, the plumes are stratification-dominated and separation occurs at h T = (2.8-0.27 u s/(B/N)1/4)(B/N 3)1/4, where N is the Brunt- Vaisala buoyancy frequency. For h T, » h s. the plumes are crossflow-dominated, and separation occurs at h s....

A daily rainfall disaggregation method, yielding regional hourly rainfall estimates, is presented with application to continuous-simulation watershed models. The disaggregation method estimates the number and volume of rain events each day and selects measured intensity patterns from a nearby station to simulate the hourly rainfall trace for each storm. No partial events are allowed, and start times are taken from a uniform probability distribution. A single calibration parameter, designating the smallest event threshold, must be estimated for each season. Comparing with hourly recorded data, the method reproduces well the variance, lag-1 autocovariance, and probability of zero rainfall. Application of the method in the upper Charles River watershed in eastern Massachusetts demonstrates that the method greatly improves the river flow simulation capability of the hydrologic model over alternate simulations using hourly rainfall outside the watershed. It is concluded that this disaggregation method provides...

[1] We present laboratory experiments for tidal starting jet vortices forming at idealized barotropic inlets using dye visualization and particle image velocimetry (PIV) of the surface velocity field. Vortices are identified in the PIV data using the local swirl strength, and metrics are calculated for each identified vortex, including position, equivalent circular diameter, maximum vorticity, circulation, and upwelling potential. These quantitative metrics are presented for four different inlet layouts, including narrow and wide barrier islands and short and long jetties. In each case, starting jet eddies initially form attached to the inlet mouth, with a rapid increase in vorticity, circulation, and size as water exiting the inlet flows directly into the starting jet dipole. Once the vortices reach a critical size, they are entrained into the tidal jet and detach from the inlet. As they advect away from the inlet, their size remains steady while the maximum vorticity and circulation gradually decrease because of the effect of bottom friction and the reduction of input to the vortices from the tidal flow as a result of their advection within the tidal jet. Secondary vortices shed from the inlet during the quasi-steady tidal jet are also entrained into the starting jet vortices, decreasing the overall rate at which their vorticity and circulation decay downstream of the inlet. The quantitative results indicate that the starting jet eddies grow, detach from the inlet mouth, and decay at predictable non-dimensional rates and times.