Bottom Flow Research Articles

Exploring subaqueous bedforms and its relation to hydrodynamics in the Rio Grande Rise, Southwestern Atlantic

This study investigates the interplay between hydrodynamics, sediment dynamics, and topography in the Rio Grande Rise (RGR) area. It addresses bedforms found in five different regions, attributing their formation to the interaction between unconsolidated carbonatic substrate and bottom currents, particularly the M2 tidal flow, the primary lunar semidiurnal constituent. The bedforms are shaped by the interplay of the M2 tidal current and local topography, with the bottom mean flow also contributing to specific areas. Generally, bedforms are classified as subaqueous dunes/tidal banks. The environmental sectorization within the RGR, driven by variations in bottom velocities related to flow-topography interaction, delineates deposition and non-deposition areas. Bathymetric data reveal that bedforms are present in shallower, lower-flow energy zones, whereas FeMn crusts are located in more profound, higher-flow energy areas. They indicate that carbonate sediments are either being transported away from the crust regions or remobilized, leading to accumulation in the areas with bedforms. The flow velocity in FeMn crust areas is able to cause sediment bypassing, resulting in areas where deposition does not occur. Furthermore, these velocities exceed the optimal flow conditions for FeMn crust precipitation and could be eroding the previously formed FeMn crusts. These findings imply that FeMn crusts lie beneath the subaqueous dunes to some extent. This study highlights the complexity of the interaction of oceanic flow with the RGR substrate and its morphology, emphasizing the importance of local hydrodynamics and topography when analyzing these features.

Analysis of the influence of bottom flow holes in control rod guide tubes on flow field and control rod displacement

During the operation of pressurized water reactors, flow-induced vibration issues are commonly encountered, where control rod components vibrate due to the impact of coolant flow, leading to wear, thereby posing a threat to the safe operation of the reactor. This paper conducts a detailed numerical simulation of the flow field and force distribution inside a full-scale lower control rod guide tube based on the CFD method. The fluid–structure interaction analysis is performed to reveal the influence of cross-flow under various operating conditions on the vibration and displacement of control rods. The research subject consists of 24 control rods, one continuous guide section, and six control rod guide cards. The lower part of the guide tube has two flow holes on each surface, with one assumed to be a cross-flow inlet and the others as outlets. The results indicate that when considering the cross-flow effect at the flow holes, 90 % of the coolant flows out from other flow holes at the bottom of the guide tube, resulting in increased transverse velocity at the bottom and the presence of numerous vortices. The magnitude and location of the force exerted on the control rod by coolant impact are correlated. The control rod closest to the inlet of the flow hole experiences the greatest force, approximately 5.35 times the average at other positions. At a cross-flow velocity of 0.4 m/s and a low frequency of 10 Hz, the maximum displacement of the control rod is 0.3355 mm.

Along-Slope Bottom Current and Sediment Resuspension and Transport Induced by Internal Tides on a Continental Slope

Abstract Moored observations on a critical continental slope in the northeastern South China Sea (SCS) are presented to reveal along-slope bottom current and sediment resuspension and transport caused by internal tides. During spring tides, the bottom-intensified diurnal internal tides were observed, and their breaking generated an along-slope bottom current toward the southwest direction, with a clear ∼14-day spring–neap cycle and a maximum low-frequency velocity exceeding 0.25 m s−1. The diurnal internal tides and along-slope bottom currents showed the same seasonal variations. There were larger near-bottom along-slope velocities in winter (∼9.0 cm s−1) and summer (∼8.9 cm s−1) than in spring (6.3 cm s−1) and autumn (7.4 cm s−1). The previous theory based on radiation stress caused by wave breaking is used to reproduce the observed along-slope bottom current velocity. Strong bottom flows caused by internal tides on the critical slope inhibit deposition of fine-grained sediments and may erode bottom coarse-grained sediments, leading to the generation of near-bottom nepheloid layer with a thickness H > 130 m, as demonstrated by the fact that seafloor sediments on the critical slope are dominated by coarse-grained sediments (sands). The suspended sediments can be southwest transported by the persistent along-slope bottom current generated by internal tide breaking. It was estimated that approximately three million tons of sediments during the observation were carried along the slope to the south of the SCS. Our observations suggest that internal tide-induced sediment resuspension/deposition and along-slope transport could be important for seafloor sediment distribution of the SCS.

Calculation Method for Bottomhole Flow Pressure in Co-layer Development of Multilayer Sandstone Reservoir

Abstract Accurately calculating the bottom hole flow pressure of a multi-layer stacked sandstone reservoir (hereinafter referred to as a multi-layer reservoir) is the basis for production splitting, oil well dynamic analysis, and reasonable work system determination in the development of multi-layer reservoirs. The bottomhole flow pressure model for single-layer oil reservoirs does not consider interlayer interference and the pressure drop caused by fluid flow in the wellbore, which doesn’t comply with the characteristics of multi-layer combined production, and the use of the maximum bottomhole flow pressure of the oil layer as the bottomhole flow pressure of each oil layer to adjust the production system of each oil layer doesn’t meet the requirements of other oil layer regulation. Firstly, starting from fluid mechanics, the frictional effect generated by fluid flow in the wellbore is systematically considered, and the relationship between wellbore frictional pressure drop and flow distance is established. The pressure drop formula generated by fluid flow in the wellbore is derived; Secondly, from the perspective of seepage mechanics, a formula for the bottom hole flow pressure of a single-layer reservoir was obtained. Combined with the expression for the difference in bottom hole flow pressure of each oil layer in the development of a multi-layer reservoir and the pressure drop expression for fluid flow in the wellbore, a bottom hole flow pressure model for each oil layer in the development of a multi-layer reservoir was established (hereinafter referred to as the multi-layer reservoir bottom hole flow pressure model). Substitute various parameters into the bottomhole flow pressure model of multi-layer oil reservoirs, and the error between the calculated values and the actual test values in the field is 0.10%~1.30%, with an average error of 0.82%, meeting the actual needs of the site. There is a significant difference in the bottom hole flow pressure values of each oil layer in the co production reservoir. The multi layer reservoir bottom hole flow pressure model can accurately calculate the bottom hole flow pressure of each oil layer, avoiding the inability to accurately adjust the production system of multiple oil layers for the same bottom hole flow pressure. It can provide technical support for the development of a reasonable drainage system for on-site co production oil wells and the realization of high and stable production.

Numerical study on flow field characteristics and performance of a Mach 10 internal injection kerosene-fueled oblique detonation engine

Oblique detonation engines (ODE) have significant potential for hypersonic propulsion, yet there is a paucity of research investigating internal injection ODEs. In this study, a numerical simulation of the internal flow field of a Mach 10 internal injection kerosene-fueled ODE is conducted. The fuel mixing, pre-combustion, and combustor wave structure in the flow field are analyzed in a situation closer to the real flow field conditions. Further studies have demonstrated that alterations to the upper wall initiation position of nozzle can influence the separation zone, flow field stability and the engine performance. An upper wall initiation position that is too far forward will increase the separation zone area and reduce the engine thrust. Conversely, an upper wall initiation position that is too far back will lead to flow field destabilization and eventually thermal choking. Finally, the effects of increasing the equivalent ratio on the flow field structure and engine performance for a certain configuration are analyzed. The results demonstrate that when the equivalent ratio is elevated, an increase in either the bottom or top incoming flow equivalent ratio results in a transformation of the wave structure within the combustor due to the presence of the incoming boundary layer and the subsonic zone. A large-scale separation zone will form at the bottom of the combustor, resulting in a reduction in nozzle thrust. However, the wedge drag is reduced more, thereby increasing the engine's specific impulse.

Dolomite formation in the Miocene Kardiva platform, Maldives archipelago: a tale of closed-system and open-system dolomitization by current pumping of seawater

Dolomites from two IODP Expedition 359 sites on the northeastern margin of the Miocene Kardiva platform, Maldives archipelago, were examined to explore the question of open versus closed system dolomitization in a drowned carbonate platform. The uppermost approx. 130 m of platform margin carbonate at site U1465 contains less than or equal to 12% dolomite except for five, meters-thick intervals with up to 65% dolomite. All U1465 dolomites consists of decimicron-sized euhedral cement crystals and mimetically replaced peloids and coralline red algal clasts. The abundance and the petrographic features of these dolomites are similar to periplatform and slope dolomite in many other settings that have been interpreted as the product of hydrologically closed-system diagenesis. In contrast, the recovered platform margin deposits at site U1469 are greater than 99% dolomite. Those dolomites are partially fabric retentive with fine-to-medium crystalline, planar subhedral to euhedral crystal mosaics of replacive dolomite and dolomite cement, all with Sr contents that average 256 ppm. Their characteristics are comparable to Neogene platform carbonates universally interpreted to signify hydrologically open-system dolomitization. Sr-isotope ages indicate Miocene dolomitization at both sites after platform drowning, and 18Odolomite values are compatible with dolomitization by cold (10⁰ to 15⁰ C) seawater when the platform margin was, on average, approx..400 m below sea level (mbsl). A current pumping mechanism for the advection of seawater into the top of the platform at site U1469 is proposed and tested with a computational fluid-flow simulation. Current pumping occurs when strong ocean bottom currents flow over sedimentary bedforms and generate lateral pressure differences along the sediment-water interface. The pressure differentials drive seawater through the underlying sediments. The flow simulation shows that the ocean currents that swept large sediment sand waves over and off the drowned Kardiva platform for many millions of years could have vigorously pumped Miocene seawater to sub-seafloor depths of many tens of meters . Mass balance considerations suggest complete dolomitization of the upper 20 m of the platform within 500 Ky or less. The current pumping mechanism could drive dolomitization and mineralogical stabilization below hiatal surfaces, or very slowly accumulating sediments, in any marine setting characterized by strong bottom currents. The greater acidity of Mioc ene seawater relative to younger seawater possibly made the pumping, by any means, of Miocene seawater of normal salinity an effective dolomitizing agent at site U1469 and in undrowned Miocene platforms globally.

Mapping Ocean Gateways from 3D Seismic Data Using Color Processing and Analogues from Seismic Data

Mapping sedimentary features to delineate ancient ocean gateways from 3D seismic data has long been a challenge due to their limited vertical resolution. We present the technique of color processing of seismic data which improves the vertical resolution to very few seismic samples corresponding to 5–10 m. The result is a representation of the seismic impedance contrast correlation in Red-Green-Blue (RGB) colors, which creates images similar to satellite images that assist the geological interpretation because the RGB colors can be associated with mud-rich and sand-rich sediments. Using this approach, we have extracted six different sedimentary bedforms from different bottom flow settings and correlated these with the bedform-velocity matrix by Stow et al. (2009). Then we studied bedform assemblies in their regional context for the area covered by the 3D seismic data set. We conclude with comparing a modern and an ancient analogue – both from 3D seismic data – and infer paleo flow direction and velocity using oceanographic measurements available for the modern analogue. The method provides insights into ocean bottom currents and their impact on the formation of contourite depositional systems in modern and ancient ocean gateways which contribute to the reconstruction of the paleoclimate as an input to present day climate change models.

Numerical simulation of depressurization exploitation in class 1 hydrate reservoirs under different development factors in Shenhu area, South China sea

Most of the implemented marine gas hydrate test exploitation in the world adopt the depressurization method to break down the hydrate in the reservoir into natural gas and then extract it, but because the gas production results are still a certain distance away from the commercial exploitation, and it mainly stays in the stage of theoretical research and trial exploitation. Based on two trial productions in the Shenhu area of the South China Sea, this study established a model for hydrate exploitation and investigated the impact of different well types on the recovery rates of hydrates and free gas in different development layers during depressurization. For the Class 1 hydrate reservoirs, horizontal wells are the optimal solution to extract hydrate and free gas simultaneously when exploiting the hydrate three-phase layer. Meanwhile, the effect of different well spacing in vertical wells on the recovery rate of hydrate and free gas was studied. It is found that the best recovery efficiency is achieved when the spacing between two wells is 80 m. The lower the bottom flow pressure of the well, the higher the production capacity, but its influence is limited.

Ventilation performance study of a high-speed train cabin based on displacement ventilation and mixed ventilation

Indoor ventilation systems play an important role in controlling energy consumption, thermal comfort, and airborne pollutants. This work is concerned with whether the combination of displacement and mixed ventilation can overcome these systems' respective shortcomings to improve the ventilation performance of high-speed train cabins. This work is based on computational fluid dynamics. The results show that when more fresh airflow enters the compartment from the top vents, the flow field is mainly driven by mechanical forces, and two vortices are formed. When more fresh airflow enters the compartment from the bottom vents, the flow field is mainly driven by thermal buoyancy. Meanwhile, the airflow mainly spreads upward, with lower cooling energy consumption, lower wind speed, higher ventilation efficiency, and smaller longitudinal diffusion of pollutants, but increased temperature difference. When the ratio of top and bottom supply air flow is 75%/25%, thermal comfort can be improved, while balancing energy consumption and air quality. If there was a disease outbreak, the flow rate of the bottom air supply could be increased appropriately. To further improve the ventilation performance, on the one hand, it is necessary to appropriately increase the temperature of the bottom air supply, and on the other hand, it is necessary to avoid short-circuiting of the airflow, due to the lack of synergy between thermal buoyancy and mechanical force. The results of the study can provide a reference for safeguarding passengers and improving the ventilation design of high-speed trains.

Labrador Coastal Current and productivity variations offshore Nain (Nunatsiavut) during the late Holocene

The Labrador Coastal Current (LCC) transports cold and fresh waters of Arctic origin towards the North Atlantic and has a strong influence on the coastal ecosystems and climate of eastern Canada. Here, we present a multi-decadally resolved record of changes in sea-surface and near-bottom conditions of the LCC during the last 3000 years based on the analysis of biogenic tracers (organic-walled dinoflagellate cysts, carbon, and nitrogen geochemistry) and sedimentary content (sortable silt, magnetic susceptibility, elemental ratios) in the upper 2 m of sediments in a core retrieved offshore Nain, Nunatsiavut. Our data reveal multi-centennial bottom flow strength variability in the LCC, with strong linkages to changes in regional ocean circulation patterns. At about 2100- and 550-years BP, the sedimentological and biogenic tracer data suggest changes in the LCC bottom current intensity (decline and strengthening, respectively) that coincide with shifts in the persistent mode of the North Atlantic Oscillation. Our proxy data suggests increased biological production during the last 500 years compared to the preceding 2500 years, possibly reflecting a gradual decrease length of the sea-ice season. The data show a decline in the LCC strength during periods of increased polar water influence identified in previous palaeoceanographic studies conducted further north, which may be attributed to the trapping of freshwater in sea ice during these periods. Our results highlight the dynamical oceanographic and atmospheric factors that influence the LCC and the coastal ecosystems along its path and confirm that the processes in Baffin Bay impact the Labrador Shelf oceanography.

CFD–DEM method is used to study the multi-phase coupling slag discharge flow field of gas-lift reverse circulation in drilling shaft sinking

To elucidate the distribution law of the multiphase coupling slag discharge flow field in gas-lift reverse circulation during drilling shaft sinking, a numerical analysis model of gas–liquid–solid multiphase coupling slag discharge was established by CFD–DEM (Coupling of computational fluid dynamics and discrete element method) method, taking the drilling of North Wind well in Taohutu Coal Mine as an example. This model presented the distribution of the multiphase flow field in the slag discharge pipe and at the bottom hole, and was validated through experimentation and theoretical analysis. Finally, the impact of factors, including bit rotation speed, gas injection rate, air duct submergence ratio, and mud viscosity on the slag discharge flow field was clarified. The results indicated that the migration of rock slag at the bottom of the well was characterized by “slip, convergence, suspension, adsorption, and lifting”. The slag flow in the discharge pipe exhibited the states of “high density, low flow rate” and “low density, high flow rate”, respectively. The multiphase fluid flow patterns in the well bottom and slag discharge pipe were horizontal and axial flows, respectively. The model test of the gas lift reversed circulation slag discharge and the theoretical model of the bottom hole fluid velocity distribution confirmed the accuracy of the multiphase coupling slag discharge flow field distribution model. The rotation speed of the drill bit had the most significant impact on the bottom hole flow field. Increasing the rotation speed of the drill bit can significantly enhance the tangential velocity of the bottom hole fluid, increase the pressure difference between the bottom hole and annular mud column, and improve the adsorption capacity of the slag suction port. These findings can provide valuable insights for gas lift reverse circulation well washing in western drilling shaft sinking.

ENVIRONMENTAL NICHE MODELLING OF FIVE GORGONIAN SPECIES WITHIN THE SHALLOW ROCKY HABITAT OF THE FRENCH MEDITERRANEAN COAST

Engineer species, such as gorgonians, provide several ecosystem services and play a significant role in the maintenance of biodiversity. We tested an ecological niche modelling an approach using a unique dataset of spatialized inventories on a regular grid (< 800 m) replicated in 2013 and 2020 along 450 km of coastline for five gorgonian species commonly found in the Mediterranean shallow habitats (10-50 m deep). Ten non-correlated environmental predictors derived from the most advanced geomorphological and hydrological data were used to assess the ecological niche of the five species using maximum entropy (Maxent). The model confirmed that different combinations of depth, rugosity, sea surface and bottom temperature, bottom flow speed and turbidity explain the different gorgonian’s distribution. The reduction of the number of presence observations did not alter the quality of the prediction as long as the observation points were spread over the entire variability range of predictors. The latter can be achieved by only including presence observations from highly protected zones of the marine protected areas of the region. Our results provide a greater understanding of the factors shaping the distribution of five gorgnian species commonly found in Mediterranean shallow areas.

Hydrodynamic analysis of the inner part of the Gulf of Nicoya, Costa Rica: Updating field measurements for coastal users

Although extensively studied, the inner region of the gulf of Nicoya (one of the main estuaries of Costa Rica) has a relatively low amount of research focused on its hydrodynamic. This represents a limitation for establishing hydrodynamical models and doing complex analysis of the water movement, which are vital for the proper management of the multiple economic, social, and ecological actors present at the estuary. The aim of this study is to generate and update hydrodynamic and bathymetric data of the inner region of the Gulf of Nicoya, with measurement periods and temporal resolutions that could be used for better understanding the hydrodynamic patterns and the development of future numerical models. Water level, current velocity, and bathymetry were measured in two separate field surveys, almost two weeks each, during dry and rainy seasons. Time series of each variable were collected with temporal resolutions of 20 min or less. Pressure and acoustic gauges were used for measuring the variables in representative sites of the hydrodynamics of the estuary. The measured data supports the hydrodynamic pattern described in previous studies, but shows some differences derived from the longer and finer data series. The most inner part of the estuary presents a time lag of up to 25 min and 30% amplification of the tide wave in comparison to the estuary’s entrance. Maximum currents show values of 1.3 m/s, and mostly around the change of tides, there are moments in which bottom and superficial currents flow in almost opposite direction with velocities less than 0.2 m/s. Bathymetry shows various areas where the new and historical data do not coincide. The present study contributes to update and extend the available data on hydrodynamic related variables, delivering updated time series with higher temporal resolution for future numerical models and general analysis from other coastal users.

Validation of a CFD model for cell culture bioreactors at large scale and its application in scale-up

Among all the operating parameters that control the cell culture environment inside bioreactors, appropriate mixing and aeration are crucial to ensure sufficient oxygen supply, homogeneous mixing, and CO2 stripping. A model-based manufacturing facility fit approach was applied to define agitation and bottom air flow rates during the process scale-up from laboratory to manufacturing, of which computational fluid dynamics (CFD) was the core modeling tool. The realizable k-ε turbulent dispersed Eulerian gas-liquid flow model was established and validated using experimental values for the volumetric oxygen transfer coefficient (kLa). Model validation defined the process operating parameter ranges for application of the model, identified mixing issues (e.g., impeller flooding, dissolved oxygen gradients, etc.) and the impact of antifoam on kLa. Using the CFD simulation results as inputs to the models for oxygen demand, gas entrance velocity, and CO2 stripping aided in the design of the agitation and bottom air flow rates needed to meet cellular oxygen demand, control CO2 levels, mitigate risks for cell damage due to shear, foaming, as well as fire hazards due to high O2 levels in the bioreactor gas outlet. The recommended operating conditions led to the completion of five manufacturing runs with a 100% success rate. This model-based approach achieved a seamless scale-up and reduced the required number of at-scale development batches, resulting in cost and time savings of a cell culture commercialization process.

Dispersion and fate of methane emissions from cold seeps on Hikurangi Margin, New Zealand

The influence of cold seep methane on the surrounding benthos is well-documented but the fate of dissolved methane and its impact on water column biogeochemistry remains less understood. To address this, the distribution of dissolved methane was determined around three seeps on the south-east Hikurangi Margin, south-east of New Zealand, by combining data from discrete water column sampling and a towed methane sensor. Integrating this with bottom water current flow data in a dynamic Gerris model determined an annual methane flux of 3 x 105 kg at the main seep. This source was then applied in a Regional Ocean Modelling System (ROMS) simulation to visualize lateral transport of the dissolved methane plume, which dispersed over ∼100 km in bottom water within 1 year. Extrapolation of this approach to four other regional seeps identified a combined plume volume of 3,500 km3 and annual methane emission of 0.4–3.2 x 106 kg CH4 y-1. This suggests a regional methane flux of 1.1–10.9 x 107 kg CH4 y-1 for the entire Hikurangi Margin, which is lower than previous hydroacoustic estimates. Carbon stable isotope values in dissolved methane indicated that lateral mixing was the primary determinant of methane in bottom water, with potential methane oxidation rates orders of magnitude lower than the dilution rate. Calculations indicate that oxidation of the annual total methane emitted from the five seeps would not significantly alter bottom water dissolved carbon dioxide, oxygen or pH; however, superimposition of methane plumes from different seeps, which was evident in the ROMS simulation, may have localized impacts. These findings highlight the value of characterizing methane release from multiple seeps within a hydrodynamic model framework to determine the biogeochemical impact, climate feedbacks and connectivity of cold seeps on continental shelf margins.

Coherence analysis of geophysical wakes in flow past a three-dimensional hill

Wakes generated by topographies are ubiquitous in nature. The formation and evolution mechanism of wake-generated eddies is essential to understanding the effect of topography on oceanic bottom flow. In this study, we analyze the temporally resolved numerical database [1] of stratified wakes past an isolated three-dimensional hill, via proper orthogonal decomposition (POD) of the vertical vorticity field. We study the dynamics of the near wake (x/D < 3) and the far wake (x/D ≥ 3) separately, where x is the downstream distance from the center of the hill. The aim is to understand how rotation influences the change of coherence from the near to the far wake and also the coherence across heights.

Numerical simulation investigating the impact of regulated underflow rate on the performance of a cyclone with split flow

A novel cyclone design called enhanced cyclone with split flow (ECSF) incorporates bypass flow and underflow to eliminate or suppress localized secondary flow observed in conventional cyclones. The present study aims to investigate the mechanism of ECSF in suppressing localized secondary flow and explore methods for regulating the bottom flow rate. The turbulent characteristics within the ECSF are obtained using Reynolds stress model, while the trajectory of particles is predicted using discrete phase model to derive the separation performance. The accuracy of the simulation model has been validated through experimental verification. The results demonstrated that the full separation efficiency of ECSF for PM10 and PM2.5 remained above 90 % and 70 %, respectively. Moreover, it exhibited an increasing trend with the rise in the full split ratio, eventually stabilizing at approximately 95 % and 77 %, correspondingly, when the full split ratio reached 20 %. The bypass flow and underflow effectively eliminated or suppressed the upper ash ring and processing vortex core (PVC) phenomenon, respectively. However, the exacerbation of the short-circuit flow phenomenon hindered further improvement in separation efficiency beyond a full diversion ratio of 20 %. When the full split ratio is relatively small, particles may accumulate in the discharge pipe, which can be resolved by introducing auxiliary airflow; however, it is crucial to ensure that the flow rate of auxiliary flow does not exceed 14.29 % of that of feed flow to avoid compromising the separation efficiency. Furthermore, the split flow induces an additional reversed vortex within the ECSF, which extends from the overflow pipe to conical section. Its structural characteristics are influenced by both back pressure of discharge outlet and diameter of underflow pipe. To ensure optimal performance of the ECSF, it is recommended that the underflow pipe diameter should not be smaller than that of the outlet in conical section.

Experimental Analysis of the Influence of the Cross-Section Coefficient on the Ship Squat While the Ship Exits the Shiplift Chamber

Due to the small cross-section coefficient of a shiplift chamber, the hydraulics problem becomes a complex water flow problem in ship operation. To prevent the ship from touching the bottom and ensure the safety of ship navigation and the docking of the chamber, a generalized physical model was used to study the ship squat of a 1000 t ship leaving the chamber. Throughout the experiment, the law of variation law in the ship squat under different chamber widths, water depths, chamber lengths, ship speeds and ship starting acceleration was obtained. In this study, the flow pattern of the ship leaving the chamber was divided into two parts: backflow and bottom flow. According to sensitivity analysis, when the shipping speed was less than 0.9 m/s, the influence of the width of the chamber on the squat was greater than that of the depth of the chamber; when the speed is greater than 0.9 m/s, the influence of the depth of the chamber on the squat was slightly greater than that of the width of the chamber. Based on our theoretical analysis, the basic expression of a ship squat was established.

Vortices over bathymetry

There are numerous examples of long-lived, surface-intensified anticyclones over submarine depressions and troughs in the ocean. These often co-exist with a large-scale cyclonic circulation. The latter is predicted by existing barotropic theory but the anticyclone is not. We extend one such theory, which minimizes enstrophy while conserving energy, to two fluid layers. This yields a bottom-intensified flow with cyclonic circulation over a depression. The solution is steady, an enstrophy minimum and stable. When the Lagrange multiplier, $\lambda$ , is near zero, the total potential vorticity (PV) becomes homogenized, in both layers. For positive $\lambda$ , the surface PV is anticyclonic and strongest at intermediate energies. In quasi-geostrophic numerical simulations with a random initial perturbation PV, the bottom-intensified cyclonic flow always emerges. Vortices evolve independently in the layers and vortex mergers are asymmetric over the depression; cyclones are preferentially strained out at depth while only anticyclones merge at the surface. Both asymmetries are linked to the topographic flow. The deep cyclones feed the bottom-intensified cyclonic circulation while the asymmetry at the surface is only apparent after that circulation has spun up. The result of the surface merger asymmetry is often a lone anticyclone above the depression. This occurs primarily at intermediate energies, when the surface PV predicted by the theory is strongest. Similar results obtain in a full complexity ocean model but with a more pronounced asymmetry in surface vortex mergers and, with bottom friction, significant bottom flow beneath the central anticyclone.

Bioreactor Culture to Create Adipose Tissue from Human Mesenchymal Stromal Cells.

Adipose tissue is a complex and multifaceted endocrine organ located throughout the body. The dysfunction of adipose tissue is known to induce a wide variety of comorbidities that can negatively impact one's health and quality of life. In addition to behavioral changes, drugs that target dysfunctional adipose tissue to treat associated diseases are clinically needed. Regarding drug-testing platforms, animal models are the most popular models, limited by known differences from humans in genetics and physiology. Two-dimensional and static three-dimensional (3D) cell cultures are also used. Still, these in vitro models with static culture fail to recapitulate the phenotype and function of adipocytes seen in vivo. To combat this, our lab has developed an adipose tissue microphysiological system. A perfusion bioreactor with dual-flow chambers is 3D printed, which enables individualized top and bottom medium flows after adipose tissues are inserted as a barrier. Human progenitor cells, such as human mesenchymal stem cells, are embedded within a gelatin scaffold and in situ adipogenic differentiation within the bioreactor. Medium flow is established via a syringe pump system, allowing in vivo-like conditions to be maintained. The novel bioreactor-cultured adipose tissues represent a versatile disease modeling and drug-testing system. Here, we present the step-by-step methods to generate the bioreactors and adipose tissues. We also show the process of collecting and analyzing samples. In addition, we highlight the critical steps that require particular attention in notes.