Buoyancy Layer Research Articles

Universal relative scaling of longitudinal structure functions in shear-dominated turbulence

Shear significantly influences turbulence in the energy-containing range of shear-dominated flows, and the longitudinal structure functions do not have a universal form as they do in homogeneous isotropic turbulence. Despite this, the relative scaling of structure functions exhibits universal sub-Gaussian behaviour in shear-dominated flows, in particular for turbulent boundary layers, channels and Taylor–Couette flows. Our investigation of a turbulent vertical buoyancy layer at $Pr = 0.71$ using direct numerical simulation shows this universality even in moderate-Reynolds-number buoyancy-driven but shear-dominated boundary layers. It is demonstrated that the universality is related to the energy density of the eddies, which attains a hierarchical equilibrium in the energy-containing range of shear-dominated turbulence. We conjecture that the universal sub-Gaussian behaviour of the energy density of the energy-containing range, which was considered to be non-trivial in prior studies, is related to the universal anomalous scaling exponents of the inertial subrange turbulence. Based on this conjecture, we propose a hypothesis that relates large-scale eddies and the intermittent dissipation field in shear-dominated turbulence, highlighting a relationship between large and small scales. A phenomenological model is also developed to predict the scaling, which is verified using data from a turbulent boundary layer, half-channel and vertical buoyancy layer at friction Reynolds numbers spanning four orders of magnitude. Excellent agreement is observed.

Experimental study of buoyancy-driven ventilation with a single opening between two adjacent building zones

In adjacent building zones connected by a single opening, a thermal plume produces a buoyant layer accumulating in the upper space of the experimental zone. The pressure difference between inside and outside the chamber will lead to air flowing in from outside and buoyant fluid flowing out from inside. This study aims to examine the effect of the vertical opening combination on flow regimes in adjacent building zones. The findings indicate that there may be three different flow regimes depending on the relative positions of the opening in the shared wall and the neutral level. The steady flow in two regimes with double stratification formed in the two zones is modeled separately and the theoretical prediction is compared with the experimental results. The flow regime of natural ventilation in the adjacent zones is only related to the height of the outlet, heat source height and effective opening area of the ventilation zones, but not to the buoyancy flux. The interface changes linearly with the height of the heat source at first until the nozzle is immersed in the buoyancy layer, and then the interface height remains constant. The relative size of the openings will also affect the volume flow rate through them, and keeping the areas of the openings along the flow passage equal will maximize the ventilation rate. These research results can provide layout guidelines for building doors and windows and will help designer improve the natural ventilation effect of adjacent building zones.

Instabilities of rotating inclined buoyancy layers.

The boundary layer near a cooled inclined plate, which is immersed in a stably stratified fluid rotating about an axis parallel to the direction of gravity, is a model for katabatic flows at high latitudes. In this paper the base flow of such an inclined buoyancy layer is solved analytically for arbitrary Prandtl numbers. By applying linear stability analyses, five unstable modes are identified for both the fixed temperature and the isoflux boundary conditions, i.e., the stationary longitudinal roll (LR) mode, the oblique roll with low streamwise wave-number (OR-1) and high streamwise wave-number (OR-2) modes, and the Tolmien-Schlichting (TS) wave with low streamwise wave-number (TS-1) and high streamwise wave-number (TS-2) modes. It is indicated that the Coriolis effect induced by the rotation leads the critical modes to be three dimensional, and a larger tilt angle of the plate and stronger Coriolis effect cause both TS wave modes to be more unstable for both thermal boundary conditions. When the Coriolis effect is considered, the OR-1 and OR-2 modes are the most unstable mode at low and high tilt angles, respectively, but the TS-1 wave mode may be the most unstable one when the plate is nearly vertical. In addition, the spanwise phase velocities of the TS wave modes change directions as the tilt angle passes some threshold values for both thermal boundary conditions except for the TS-1 wave mode with a fixed temperature boundary condition, which propagates in the same spanwise direction for all explored tilt angles.

Instabilities of the buoyancy layer for the Carreau fluid in thermally stratified medium

Instabilities of the buoyancy layer for the Carreau fluid in thermally stratified medium

Large-scale motions in a turbulent natural convection boundary layer immersed in a stably stratified environment

This study investigates the coherence of turbulent fluctuations in a turbulent vertical natural convection boundary layer immersed in a stably stratified medium (turbulent buoyancy layer). A turbulent buoyancy layer of a fluid having a Prandtl number of $0.71$ at a Reynolds number of $800$ is numerically simulated using direct numerical simulation. The two-point correlations reveal that the streamwise velocity fluctuations are coherent over large streamwise distances, with the length scale of the streamwise coherence being greater than the boundary layer thickness. This is due to large-scale motions (LSMs), similar to the LSMs observed in canonical wall-bounded turbulence despite the stark differences in flow dynamics. Both high-speed (positive) and low-speed (negative) streamwise velocity fluctuations form LSMs, with their streamwise length scales increasing with increasing wall-normal distance. High-speed LSMs are composed of upwash flow with high temperatures, while low-speed LSMs are composed of downwash flow with low temperatures. Both high-speed and low-speed LSMs meander appreciably in the streamwise direction, with the degree of meandering being correlated with the sign of the spanwise velocity fluctuations. The LSMs exhibit coherence across significant wall-normal distances and contribute significantly to the turbulence production in the outer layer. Examining the one-dimensional energy spectra of the turbulent buoyancy layer shows that the LSMs are the dominant energy-containing motions, implying that the length scale of the energy-containing range is of the order of boundary layer thickness. Notably, wall-normal velocity, spanwise velocity and buoyancy fluctuations do not form LSMs with streamwise length scales comparable to streamwise velocity fluctuations.

Oblique-mode breakdown of the vertical buoyancy layer

The O-type transition caused by a pair of small-amplitude oblique waves in a vertical buoyancy layer of a fluid with Prandtl number $0.71$ at a Reynolds number of $200$ is investigated using linear stability analysis and three-dimensional direct numerical simulation. The small-amplitude oblique waves experience linear growth and undergo nonlinear interactions to generate streamwise vortices/streaks, two-dimensional streamwise waves and harmonic oblique waves. The streamwise vortices/streaks and two-dimensional streamwise waves have twice the spanwise or streamwise wavenumber of the original perturbation, respectively. Unlike the O-type transition in isothermal flat-plate incompressible and compressible boundary layers where streaks dominate the transition, in the vertical buoyancy layer, either streaks or two-dimensional streamwise waves can dominate the flow field during the early stages of oblique transition. The growth rates of streaks and two-dimensional waves are dependent on the wavenumber of the initial oblique waves. Streaks dominate the flow for high streamwise wavenumbers, while two-dimensional streamwise waves dominate the flow for low streamwise wavenumbers. Analysis of the turbulent kinetic energy production and the Reynolds stresses reveals that the early stages of the transition differ depending on the wavenumber of the oblique waves. An increase in the initial amplitude of the oblique waves causes a faster transition from laminar flow; however, the growth rates of the streaks and two-dimensional streamwise waves are independent of the initial amplitude. Even though different modes are dominant during the early stages of the O-type transition, the onset of chaotic flow is caused by the breakdown of streak modes.

Convective and absolute instabilities in inclined buoyancy layers

The linear instability of the buoyancy-driven flow adjacent to an inclined heated wall immersed in a thermally stratified medium is studied theoretically and numerically. For the temporally unstable system, spatiotemporal stability analysis is carried out to delineate the parameter space (Grashof number, Prandtl number, and tile angle) for convective/absolute instability. We provide an example of an absolute instability of the buoyancy layer on an inclined buoyancy layer. It is shown that the tile angle and Prandtl number have a dramatic influence on the spatial-temporal properties of the flow. For fixed Pr = 6.7, increasing tile angle decreases the domain of absolute instability, and when tile angle is greater than 20°, the absolute instability disappears. The flow will change from convectively unstable to absolutely unstable with the increase of Pr. Results from the direct numerical simulation are in agreement with the predictions of the linear temporal and spatial-temporal instabilities. These encouraging results should be helpful for understanding such a buoyancy-driven flow system.

Entropy analysis of MHD flow of Jeffrey fluid in an inclined channel

AbstractThis study is aimed at investigating the influence of entropy analysis of magnetohydrodynamic flow of Jeffrey fluid in an inclined micro‐channel in the presence of thermal radiation and field suction/injection. We have improved the mathematical model of the physical problem under consideration. The designed equations have been solved by applying the shooting‐based fourth‐order, Runge–Kutta method with the boundary conditions, which describe velocity slip and temperature jump conditions at the fluid–wall inter‐face. Numerical efforts are described graphically and mentioned quantitatively concerning different parameters such as Jeffery parameter, Bejan number, and entropy generation embedded in the problem. The numerical results for the expression of the irreversibility ratio are obtained. It is observed that the wall inclination strengthens the entropy production rate in the micro‐channel, and the thermal buoyancy layer induces an increase in fluid velocity as suction.

Propagation and Separation of Downslope Gravity Currents over Rigid and Emergent Vegetation Patches in Linearly Stratified Environments

Large eddy simulation (combined with the mixture model) and laboratory experiment were used to investigate the impact of emergent and rigid vegetation on the dynamics of downslope gravity currents in stratified environments. The reliability of the numerical model was assessed with the corresponding laboratory measurements. The results show that the vegetation cylinders lead to severe lateral non-uniformity of the current front, causing more evident lobe and cleft structures. In stratified environments, the smaller driving force leads to less propagating velocity until the current separates from the slope. The transition point (from acceleration to deceleration phases) of current velocity appears earlier as the vegetation becomes denser. The peak value of the bulk entrainment coefficient Ebuik is inversely proportional to the vegetation density, while the final converged value of Ebuik is proportional to the vegetation density. Vegetation patches make the degree of fluctuation of the instantaneous entrainment coefficient Einst more intense, and even negative values appear locally, indicating that the gravity current is detrained into the ambient fluid. The velocity profiles of gravity current develop multi-peak patterns in stratified environments due to fingering intrusive patterns. Our analysis reveals that as the vegetation density increases, the generated wakes behind vegetation cylinders increase local entrainment and mixing, causing the density of current flow from vegetation to decrease and reach the neutral buoyancy layer of ambient fluids earlier, finally leading to a smaller separation depth.

Natural convection in air-filled differentially heated isoflux cavities: Scalings and transition to unsteadiness, a long story made short

We investigate numerically the transition to unsteadiness of natural convection in air filled differentially heated cavities heated and cooled with uniform flux at their vertical boundaries. This is done using both time integration of the nonlinear equations and of the linearized equations around a steady solution and computation of the leading eigenvalues of the Jacobian of steady solutions. Results are given for values of the vertical aspect ratio ranging from 0.2 to 8. In the square air filled cavity the transition occurs at a value of the flux Rayleigh number very close to 4.5×1012. We characterize different groups of eigenmodes of the Jacobian. We show that the modes responsible for the transition are characterized by a wavelike structure of constant wavelength whose amplitude increases exponentially with height in the upward boundary layer along the heated wall. We show that, at criticality, the wave characteristics are in fair agreement with values of the linear stability analysis of the buoyancy layer. We also discuss the evolution of the eigenvalues layout with the aspect ratio.

An experimental study on the flow and heat transfer of an impinging synthetic jet

This study experimentally investigated the combined effects of the wall temperature (Tw0) and the orifice-to-wall distance (H/D) on the flow and heat transfer characteristics of an impinging synthetic jet. Thermographic phosphor thermometry (TPT) was used to measure the wall surface temperature, and the quantitative flow velocity was obtained using time-resolved particle image velocimetry (PIV). A cavity-diaphragm actuator was employed to generate a round synthetic jet to impinge onto a heated wall that was coated with Mg4FGeO6:Mn (MFG) for use as a temperature sensor. Three orifice-to-wall distances (H/D = 10, 15, and 20) and three wall temperatures (Tw0 = 60 °C, 90 °C, and 120 °C) were tested for comparison, whereas the the operating conditions of the incident synthetic jet were kept constant. It was found that the maximum temperature drop at the stagnation point could reach approximately 50°C although the orifice-to-wall distance was relatively large in this study, which indicated a good cooling performance of the synthetic jet. The penetration of the wall shear layer played an important role on the cooling performance of the impinging synthetic jet. For a heated wall with high Tw0, the enhanced buoyancy and thermal boundary layer resulted in the formation of a strong wall shear layer, which was more difficult for the impinging synthetic jet to affect or penetrate. For a large H/D, the vortex rings of the synthetic jet lose coherence completely before impacting the wall. Thus, they have no ability to penetrate the wall’s shear layer to interact with it directly. As a result, the cooling performance of the impinging synthetic jet gradually decreased as both Tw0 and H/D increased. In particular, the maximum cooling effect by the synthetic jet impingement can achieve 64% of the theoretical maximum.

Exploring the Importance of the Mindoro‐Sibutu Pathway to the Upper‐Layer Circulation of the South China Sea and the Indonesian Throughflow

AbstractUsing a high‐resolution (0.1° × 0.1°) regional ocean model, this study investigates the impact of strait transport variability on the South China Sea (SCS) circulation and Indonesian throughflow, with a focus on the Mindoro‐Sibutu pathway via the Sulu Sea, upon closing various straits within the Maritime Continent. Closing the Sibutu Strait reduces the Luzon Strait throughflow into the SCS by 75%, and the Mindoro–Sibutu deep exchange is reversed, thus flowing into the SCS. No significant change occurs over the shallow Sunda Shelf of the southern SCS, which is primarily driven by local monsoon winds. The impact of closing the Karimata Strait is limited to the Sunda Shelf and the Java Sea. The Sibutu Strait throughflow is fundamental in governing the SCS's low salinity, buoyancy, and upper layer injection into the Makassar Strait, which is the primary component of the Indonesian throughflow, thus inhibiting the transport within the upper 200 m of the throughflow. Closing both the Sibutu and Karimata Straits increases the southward Makassar Strait throughflow transport by ~3 Sv, which is derived entirely from the Mindanao Current.

Statistical state dynamics analysis of buoyancy layer formation via the Phillips mechanism in two-dimensional stratified turbulence

Horizontal density layers are commonly observed in stratified turbulence. Recent work (e.g. Taylor & Zhou, J. Fluid Mech., vol. 823, 2017, R5) has reinvigorated interest in the Phillips instability (PI), by which density layers form via negative diffusion if the turbulent buoyancy flux weakens as stratification increases. Theoretical understanding of PI is incomplete, in part because it remains unclear whether and by what mechanism the flux-gradient relationship for a given example of turbulence has the required negative-diffusion property. Furthermore, the difficulty of analysing the flux-gradient relation in evolving turbulence obscures the operating mechanism when layering is observed. These considerations motivate the search for an example of PI that can be analysed clearly. Here PI is shown to occur in two-dimensional Boussinesq sheared stratified turbulence maintained by stochastic excitation. PI is analysed using the second-order S3T closure of statistical state dynamics, in which the dynamics is written directly for statistical variables of the turbulence. The predictions of S3T are verified using nonlinear simulations. This analysis provides theoretical underpinning of PI based on the fundamental equations of motion that complements previous analyses based on phenomenological models of turbulence.

Dynamic Interaction and Mixing of Two Turbulent Forced Plumes in Linearly Stratified Ambience

The hydrodynamics of a two-vent turbulent forced plume propagating in a linear stratification has been studied by a series of laboratory experiments using the two-tank method and the particle image velocimetry (PIV) technique. The velocity fields and turbulence characteristics of a two-vent plume under different source buoyancy flux, ambient stratification, and nozzle distance are analyzed quantitatively. The increase of maximum penetration of a two-vent plume is mainly due to the attenuation of buoyancy gradient caused by less entrainment of ambient fluid in the region between the two vents. The energy spectra do not exhibit a sizable range of the Kolmogorov −5/3 slope, indicating that no substantial inertial subrange is present in this small-scale plume in a linear stratification generated in the laboratory. Both turbulent kinetic energy and dissipation increase with the decrease of distance between the two plumes, indicating that the interaction, entrainment, and mixing in a two-vent plume stem greatly enhance energy production and dissipation. The maximum turbulent viscosity in a two-vent plume, however, presents a three-stage variation. An increase of viscosity in the second stage appears in the mixing region of the neutral buoyancy layer between the two plumes when the normalized distance L/Zmax is in the range of 0.3–0.6; this increase is attributed to flow rebound after overshooting and a strong entrainment and mixing in this region due to lateral flow convection. A new semiempirical formula for the maximum penetration and new scaling relationships for the maximum turbulent viscosity of a two-vent plume are proposed and verified by the PIV experimental data.

A New Mechanism for Mode Water Formation Involving Cabbeling and Frontogenetic Strain at Thermohaline Fronts. Part II: Numerical Simulations

AbstractSubmesoscale-resolving numerical simulations are used to investigate a mechanism for sustained mode water formation via cabbeling at thermohaline fronts subject to a confluent strain flow. The simulations serve to further elucidate the mechanism and refine the predictions of the analytical model of Thomas and Shakespeare. Unlike other proposed mechanisms involving air–sea fluxes, the cabbeling mechanism, in addition to driving significant mode water formation, uniquely determines the thermohaline properties of the mode water given knowledge of the source water masses on either side of the front. The process of mode water formation in the simulations is as follows: Confluent flow associated with idealized mesoscale eddies forces water horizontally toward the front. The frontogenetic circulation draws this water near adiabatically from the full depth of the thermohaline front up to the surface 25 m, where resolved submesoscale instabilities drive intense mixing across the thermohaline front, creating the mode water. The mode water is denser than the surrounding stratified fluid and sinks to fill its neutral buoyancy layer at depth. This layer gradually expands up to the surface, and eddies composed entirely of this mode water detach from the front and accumulate in the diffluent regions of the domain. The process continues until the source water masses are exhausted. The temperature–salinity (T–S) relation of the resulting mode water is biased to the properties of the source water that has the larger isopycnal T–S anomaly. This mechanism has the potential to drive O(1) Sv (1 Sv ≡ 106 m3 s−1) mode water formation and may be important in determining the properties of mode water in the global oceans.

Lower bound for transient growth of inclined buoyancy layer

The relationship between stabilities of the buoyancy boundary layers along an inclined plate and a vertical plate immersed in a stratified medium is studied theoretically and numerically. The eigenvalue problem of energy stability is solved with the method of descending exponentials. The disturbance energy is found to be able to grow to 11.62 times as large as the initial disturbance energy for Pr = 0.72 when the Grashof number is between the critical Grashof numbers of the energy stability and the linear stability. We prove that, with a weighted energy method, the basic flow of the vertical buoyancy boundary layer is stable to finite-amplitude streamwise-independent disturbances.

On the sensitivity of the diurnal cycle in the Amazon to convective intensity.

Climate and reanalysis models contain large water and energy budget errors over tropical land related to the misrepresentation of diurnally forced moist convection. Motivated by recent work suggesting that the water and energy budget is influenced by the sensitivity of the convective diurnal cycle to atmospheric state, this study investigates the relationship between convective intensity, the convective diurnal cycle, and atmospheric state in a region of frequent convection—the Amazon. Daily, 3‐hourly satellite observations of top of atmosphere (TOA) fluxes from Clouds and the Earth's Radiant Energy System Ed3a SYN1DEG and precipitation from Tropical Rainfall Measuring Mission 3B42 data sets are collocated with twice daily Integrated Global Radiosonde Archive observations from 2002 to 2012 and hourly flux tower observations. Percentiles of daily minimum outgoing longwave radiation are used to define convective intensity regimes. The results indicate a significant increase in the convective diurnal cycle amplitude with increased convective intensity. The TOA flux diurnal phase exhibits 1–3 h shifts with convective intensity, and precipitation phase is less sensitive. However, the timing of precipitation onset occurs 2–3 h earlier and the duration lasts 3–5 h longer on very convective compared to stable days. While statistically significant changes are found between morning atmospheric state and convective intensity, variations in upper and lower tropospheric humidity exhibit the strongest relationships with convective intensity and diurnal cycle characteristics. Lastly, convective available potential energy (CAPE) is found to vary with convective intensity but does not explain the variations in Amazonian convection, suggesting that a CAPE‐based convective parameterization will not capture the observed behavior without incorporating the sensitivity of convection to column humidity.

Seismic processes and migration of magma during the Great Tolbachik Fissure Eruption of 1975–1976 and Tolbachik Fissure Eruption of 2012–2013, Kamchatka Peninsula

Seismic and volcanic processes in the area of the northern group of volcanoes (NGV) in Kamchatka Peninsula that accompanied the Great Tolbachik Fissure Eruption (GTFE) of 1975–1976 and the Tolbachik Fissure Eruption (TFE, or “50 let IViS” due to anniversary of the Institute of Volcanology and Seismology, Far East Branch, Russian Academy of Sciences) of 2012–2013 and the seismic activity between these events are considered. The features of evolution of seismic processes of the major NGV volcanoes (Ploskii Tolbachik, Klyuchevskoy, Bezymannyi, and Shiveluch) are revealed. The distribution of earthquakes along depth, their spatial and temporal migration, and the relation of seismic and volcanic activity are discussed. The major features of seismic activity during the GTFE preparation and evolution and a development of earthquake series preceding the origin of the northern and southern breaks are described. The character of seismic activity between the GTFE and TFE is shown. The major peculiarities of evolution of seismic activity preceding and accompanying the TFE are described. The major magma sources and conduits of the NGV volcanoes are identified, as is the existence of a main conduit in the mantle and a common intermediate source for the entire NGV, the depth of which is 25–35 km according to seismic data. The depth of a neutral buoyancy layer below the NGV is 15–20 km and the source of areal volcanism of magnesian basalts northeast of the Klyuchevskoy volcano is located at depth of ~20 km. These data support the major properties of a 2010 geophysical model of magmatic feeding system of the Klyuchevskoy group of volcanoes. The present paper covers a wider NGV area and is based on the real experimental observations.

Development and Comparative Assessment of Hydrocolloid Based Against Wax Based Gastro Retentive Bilayered Floating Tablet Designs of Atorvastatin Calcium Using Qbd Approach

Development and Comparative Assessment of Hydrocolloid Based Against Wax Based Gastro Retentive Bilayered Floating Tablet Designs of Atorvastatin Calcium Using Qbd Approach Atorvastatin calcium is one of the most widely prescribed lipid lowering drug and due to its acidic degradation properties the bioavailability reported is only 12-14% when administered orally. The gastro retentive floating tablets of Atorvastatin calcium had shown enhanced bioavailability compared to conventional immediate release dosage forms. The study presented here was focused on comparing the physicochemical properties of two different bilayered controlled release gastro retentive buoyant formulation designs of Atorvastatin calcium tablets. The buoyancy layer for first formulation was swelling hydrocolloid based (HPMC) against the second formulation design which was non swellable wax (HCO) based. The drug release characteristics, kinetic models, buoyancy characteristics and stability were compared between the two formulation designs. Apart the DoE (22 factorial design) studies were carried out to understand the impact and range of release controlling agents in drug layer against the dissolution profile in pH 4.5 acetate buffer. The buoyancy properties were observed to be consistent and stable in case of HPMC based buoyancy system, where as the wax based formulation design had shown tendencies for layer seperation at higher agitation speeds.

Investigation of saline water intrusions into the Curonian Lagoon (Lithuania) and two-layer flow in the Klaipėda Strait using finite element hydrodynamic model

Abstract. This work is focused on the application of a modelling system to simulate 3-D interaction between the Curonian Lagoon and the Baltic Sea coastal waters and to reflect spatiotemporal dynamics of marine waters in the Curonian Lagoon. The model system is based on the finite element programme package SHYFEM which can be used to resolve the hydrodynamic equations in lagoons, coastal seas, estuaries and lakes. The results of a one year (2009) 3-D model simulation with real weather and hydrological forcing show that the saline water intrusions from the sea through Klaipėda Strait are gradually decreasing with distance from the sea and become negligible (average annual salinity about 0.57‰) at a distance of about 20 km to the south of Kiaulės Nugara island. Analyses of the simulation results also show this area to be highly heterogeneous according to the vertical salinity distribution. While in the deeper Klaipėda Strait (harbour waterway) differences in average salinity between near bottom and surface layers varies in the range 2–2.5‰, in the rest of the Curonian Lagoon it is less than 0.5‰. The exchange flow showed vertical structure, but was horizontally uniform with the presence of a two-directional flow that from time to time changes to either saline water one-directional flow to the Curonian Lagoon or fresh water one-directional flow to the sea. Two-directional flow duration decreases with a distance from sea entrance in Klaipėda Strait from around 180 days yr−1 close to the sea entrance to 50 days yr−1 just behind Kiaulės Nugara island. One-directional outflow duration is increasing with a distance from the sea entrance from 100 to 225 days yr−1. One-directional inflow duration occurs in the range of 70–100 days yr−1. The analysis of the ratio of buoyancy layer thickness to water depth (hb/H) and the Wedderburn number identified the main importance of wind action on the flow structure. Strong winds from the North and NW determine a barotropic inflow which is mostly responsible for the salt water intrusion into the Curonian Lagoon. Absence of wind or cross-strait wind regimes allows the maintenance of a two-layer flow typical of estuarine dynamics.