Shear-induced Mixing Research Articles

Ebb-Tide Dynamics and Spreading of a Large River Plume*

Abstract Momentum balances in the near-field region of a large, tidally pulsed river plume are examined. The authors concentrate on a single ebb tide of the Columbia River plume, using the Regional Ocean Modeling System (ROMS) configured to hindcast flow conditions on the Washington and Oregon shelves and in the Columbia River estuary. During ebb, plume-interior streamwise balances are largely between advection, pressure gradient, and frictional forces. Stream-normal balances in this region reduce to centrifugal, cross-stream pressure gradient, and Coriolis terms (i.e., the “gradient wind” balance commonly assumed in river plume bulge investigations). Temporal derivatives are most important at the plume front and as the ebb progresses. Winds were light and contributed little to the force balance. Midebb stress and vertical salt flux were largest at a midplume depth, where stratification and vertical shear were also high, consistent with shear-induced mixing. Internal stress slows the spreading plume considerably. A kinematic description of the spreading process relates lateral spreading to the momentum dynamics and illustrates that plume spreading is largely a competition between the cross-stream pressure gradient and Coriolis forces. However, the very near-field dome of buoyant water is instrumental in setting initial flow pathways.

The diapcynal nutrient flux and shear-induced diapcynal mixing in the seasonally stratified western Irish Sea

We estimate the diapcynal nitrate flux in the seasonally stratified western Irish Sea using the dissipation method. By comparing the divergence of the reported benthic and diapcynal nitrate fluxes, we are able to explain much of the observed annual summer decline in deep-water nitrate at this location. We then show that the new production, fuelled by the diapcynal nitrate flux, is of a similar magnitude to that associated with the spring bloom. This suggests that the physical processes responsible for the diapcynal nitrate flux will set the limit on new production at this location. High-resolution mid-water column ADCP measurements show an average thermocline gradient Richardson number of 1, thus suggesting episodes of enhanced shear could result in shear instability, and therefore mixing within the thermocline. Bulk shear measurements reveal episodes of enhanced shear in the form of spikes, during which time the bulk shear vector takes the form of a clockwise rotating vector which has a period close to the local inertial period. The episodes of shear spikes are correlated to the wind and are consistent with observations made elsewhere. Estimates of profiles of the rate of dissipation of turbulent kinetic energy, based on microstructure velocity measurements, show that during a shear spike the dissipation rate within the thermocline, and therefore the buoyancy (and nitrate) flux, is enhanced by a factor of 4 when compared to periods with no shear spikes. Intermittent shear spikes are, therefore, an important mechanism for enhancing mixing across the shelf sea seasonal thermocline, and therefore delivery of nitrate to the euphotic zone, at this location.

Fluid Mixing in Stratified Gravity Currents: The Prandtl Mixing Length

Shear-induced vertical mixing in a stratified flow is a key ingredient of thermohaline circulation. We experimentally determine the vertical flux of momentum and density of a forced gravity current using high-resolution velocity and density measurements. A constant eddy-viscosity model provides a poor description of the physics of mixing, but a Prandtl mixing length model relating momentum and density fluxes to mean velocity and density gradients works well. For the average gradient Richardson number Ri(g) approximately 0.08 and a Taylor Reynolds number Re(lambda) approximately 100, the mixing lengths are fairly constant, about the same magnitude, comparable to the turbulent shear length.

Quantifying vertical mixing in estuaries

Estuarine turbulence is notable in that both the dissipation rate and the buoyancy frequency extend to much higher values than in other natural environments. The high dissipation rates lead to a distinct inertial subrange in the velocity and scalar spectra, which can be exploited for quantifying the turbulence quantities. However, high buoyancy frequencies lead to small Ozmidov scales, which require high sampling rates and small spatial aperture to resolve the turbulent fluxes. A set of observations in a highly stratified estuary demonstrate the effectiveness of a vessel-mounted turbulence array for resolving turbulent processes, and for relating the turbulence to the forcing by the Reynolds-averaged flow. The observations focus on the ebb, when most of the buoyancy flux occurs. Three stages of mixing are observed: (1) intermittent and localized but intense shear instability during the early ebb; (2) continuous and relatively homogeneous shear-induced mixing during the mid-ebb, and weakly stratified, boundary-layer mixing during the late ebb. The mixing efficiency as quantified by the flux Richardson number Rf was frequently observed to be higher than the canonical value of 0.15 from Osborn (J Phys Oceanogr 10:83–89, 1980). The high efficiency may be linked to the temporal–spatial evolution of shear instabilities.

Loop Current Response to Hurricanes Isidore and Lili

Abstract Recent hurricane activity over the Gulf of Mexico basin has underscored the importance of the Loop Current (LC) and its deep, warm thermal structure on hurricane intensity. During Hurricanes Isidore and Lili in 2002, research flights were conducted from both National Oceanic and Atmospheric Administration (NOAA) WP-3D aircraft to observe pre-, in- and poststorm ocean conditions using airborne expendable ocean profilers to measure temperature, salinity, and current structure. Atmospheric thermodynamic and wind profiles and remotely sensed surface winds were concurrently acquired as each storm moved over the LC. Observed upper-ocean cooling was about 1°C as Isidore moved across the Yucatan Straits at a speed of 4 m s−1. Given prestorm ocean heat content (OHC) levels exceeding 100 kJ cm−2 in the LC (current velocities >1 m s−1), significant cooling and deepening of the ocean mixed layer (OML) did not occur in the straits. Estimated surface enthalpy flux at Isidore’s eyewall was 1.8 kW m−2, where the maximum observed wind was 49 m s−1. Spatially integrating these surface enthalpy fluxes suggested a maximum surface heat loss of 9.5 kJ cm−2 at the eyewall. Over the Yucatan Shelf, observed ocean cooling of 4.5°C was caused by upwelling processes induced by wind stress and an offshore wind-driven transport. During Hurricane Lili, ocean cooling in the LC was ∼1°C but more than 2°C in the Gulf Common Water, where the maximum estimated surface enthalpy flux was 1.4 kW m−2, associated with peak surface winds of 51 m s−1. Because of Lili’s asymmetric structure and rapid translational speed of 7 m s−1, the maximum surface heat loss resulting from the surface enthalpy flux was less than 5 kJ cm−2. In both hurricanes, the weak ocean thermal response in the LC was primarily due to the lack of energetic near-inertial current shears that develop across the thin OML observed in quiescent regimes. Bulk Richardson numbers remained well above criticality because of the strength of the upper-ocean horizontal pressure gradient that forces northward current and thermal advection of warm water distributed over deep layers. As these oceanic regimes are resistive to shear-induced mixing, hurricanes experience a more sustained surface enthalpy flux compared to storms moving over shallow quiescent mixed layers. Because ocean cooling levels induced by hurricane force winds depend on the underlying oceanic regimes, features must be accurately initialized in coupled forecast models.

Process-Oriented Analysis of Environmental Conditions Associated with Precipitation Fog Events in the New York City Region

Abstract An analysis of the environmental conditions associated with precipitation fog events is presented using 20 yr of historical observations taken in a region centered on New York, New York. The objective is to determine the preferred weather scenarios and identify physical processes influencing the formation of fog during precipitation. Salient synoptic-scale features are identified using NCEP–NCAR reanalyses. Local environmental parameters, such as wind speed and direction, temperature, and humidity, are analyzed using surface observations, while the vertical structure of the lower atmosphere is examined using available rawinsonde data. The analysis reveals that precipitation fog mostly occurs as a result of the gradual lowering of cloud bases as continuous light rain or light drizzle is observed. Such scenarios occur under various synoptic weather patterns in areas characterized by large-scale uplift, differential temperature advection, and positive moisture advection. Precipitation fog onset typically occurs with winds from the northeast at inland locations and onshore flow at coastal locations, with flows from the south to southwest aloft. A majority of the cases showed the presence of a sharp low-level temperature inversion resulting from differential temperature advection or through the interaction of warm air flowing over a cold surface in onshore flow conditions. This suggests a common scenario of fog formation under moistening conditions resulting from precipitation evaporating into colder air near the surface. A smaller number of events formed with cooling of the near-saturated or saturated air. Evidence is also presented of the possible role of shear-induced turbulent mixing in the production of supersaturation and fog formation during precipitation.

Solvent quality as a key factor for shear-induced mixing in biopolymer emulsions

A rheo-optical methodology, based on small-angle light-scattering and transmitted-light-intensity measurements, has been used to perform an in situ and time-resolved investigation of the shear-induced mixing in ternary two-phase biopolymer emulsions. Aqueous emulsions on the basis of two proteins, two polysaccharides, protein and polysaccharide were chosen to elucidate the role of the solvent quality, composition of emulsion and phase viscosity ratio (PVR) on the phase behavior and emulsion morphology. The solvent quality has been quantified by determining the activity of the biopolymer in its saturated solution. It is shown that the level of activity of both biopolymers is a key factor in determining the capacity of the emulsion to undergo shear-induced mixing, while the interfacial tension and PVR of emulsions effect on the shear-induced phase behavior have a smaller effect. If the mean apparent activity of the biopolymer pair expressed as Log C biopol is equal and higher than −0.15 a shear-induced mixing in biopolymer emulsions is observed at a very low shear rates (1 s −1 and less). If the mean activity of the biopolymer pair is in the range from −0.4 to 0.9 a shear-induced mixing is registered at a higher shear rates (from 40 to 100 s −1 accordingly), while at a lower the mean activity, the phase transition is not observed at any shear rate studied (up to 200 s −1).

Phase morphological evolution and rheological properties of polypropylene/ethylene–octene copolymer blends

The morphological evolution during extrusion and rheological properties of polypropylene (PP) and ethylene–octene copolymer (EOC) blends were studied. The phase morphology of the blends at different locations along the extruder length was investigated by scanning electron microscopy (SEM). The PP/EOC (70/30) blends has already formed a well-established droplet/matrix morphology at Valve 3, and an elongation of particles was observed from Valve 3 to extruder die. The phase-separated PP/EOC blends within the linear viscoelastic regime display higher than expected values of storage modulus at low frequencies. The effect of the deformation of phase domain on the rheological properties of the blends, the small constant strain amplitude within the linear viscoelastic regime does not substantially alter the droplet shape of the dispersed phase and yields a linear viscoelastic response, but the large strain amplitude destroys the dispersed phase domains, and eventually results in shear-induced mixing or homogenization.

Air–Sea Exchange in Hurricanes: Synthesis of Observations from the Coupled Boundary Layer Air–Sea Transfer Experiment

The Coupled Boundary Layer Air–Sea Transfer (CBLAST) field program, conducted from 2002 to 2004, has provided a wealth of new air–sea interaction observations in hurricanes. The wind speed range for which turbulent momentum and moisture exchange coefficients have been derived based upon direct flux measurements has been extended by 30% and 60%, respectively, from airborne observations in Hurricanes Fabian and Isabel in 2003. The drag coefficient (CD) values derived from CBLAST momentum flux measurements show CD becoming invariant with wind speed near a 23 m s−1 threshold rather than a hurricane-force threshold near 33 m s−1 . Values above 23 m s−1 are lower than previous open-ocean measurements. The Dalton number estimates (CE) derived from CBLAST moisture flux measurements are shown to be invariant with wind speeds up to 30 m s −1 which is in approximate agreement with previous measurements at lower winds. These observations imply a CE/CD ratio of approximately 0.7, suggesting that additional energy sources are necessary for hurricanes to achieve their maximum potential intensity. One such additional mechanism for augmented moisture flux in the boundary layer might be “roll vortex” or linear coherent features, observed by CBLAST 2002 measurements to have wavelengths of 0.9–1.2 km. Linear features of the same wavelength range were observed in nearly concurrent RADARSAT Synthetic Aperture Radar (SAR) imagery. As a complement to the aircraft measurement program, arrays of drifting buoys and subsurface floats were successfully deployed ahead of Hurricanes Fabian (2003) and Frances (2004) [16 (6) and 38 (14) drifters (floats), respectively, in the two storms]. An unprecedented set of observations was obtained, providing a four-dimensional view of the ocean response to a hurricane for the first time ever. Two types of surface drifters and three types of floats provided observations of surface and subsurface oceanic currents, temperature, salinity, gas exchange, bubble concentrations, and surface wave spectra to a depth of 200 m on a continuous basis before, during, and after storm passage, as well as surface atmospheric observations of wind speed (via acoustic hydrophone) and direction, rain rate, and pressure. Float observations in Frances (2004) indicated a deepening of the mixed layer from 40 to 120 m in approximately 8 h, with a corresponding decrease in SST in the right-rear quadrant of 3.2°C in 11 h, roughly one-third of an inertial period. Strong inertial currents with a peak amplitude of 1.5 m s−1 were observed. Vertical structure showed that the critical Richardson number was reached sporadically during the mixed-layer deepening event, suggesting shear-induced mixing as a prominent mechanism during storm passage. Peak significant waves of 11 m were observed from the floats to complement the aircraft-measured directional wave spectra.

Observations and modeling of shelf-slope front seasonal variability between 75°and 50°W

Abstract The shelf-slope front (SSF) located off the northeastern United States and Canada is an oceanographic front separating colder and less-saline continental shelf waters from generally warmer and more-saline slope waters over the continental slope. The surface expression of the SSF is visible year-round using sea-surface temperature (SST) data obtained from satellite-based infrared radiometers. Availability of 20 years (1973–1992) of SSF positions, digitized from weekly satellite-derived SST charts between 75 ∘ and 50 ∘ W longitude, allows a detailed spatial analysis of the seasonal variability of the SSF position between Cape Hatteras and the Tail of the Grand Banks. Results show an overall maximum seaward (shoreward) extent during winter (summer), consistent with earlier work. However, our more detailed spatial analysis shows that the eastern-most and western-most monthly SSF anomalies, relative to the long-term (1973–1992) mean, are 180 ∘ out of phase, with maximum seasonal SSF variability of O ( ± 50 km ) occurring generally east of 58 ∘ W . Furthermore, seasonal westward propagation of the seaward-most (landward-most) SSF position is evident between 50 ∘ and 58 ∘ W from November to April (May–October), decreasing in amplitude towards the west. A simple Ekman coastal plume model incorporating gridded wind-stress anomalies and a constant plume depth ( h c = 25 m ) reproduces the general seasonal cycle of the SSF along with the east-west phase shift, except in easternmost regions where SSF positional variability is maximal. The east-west phase shift results from interaction between the slowly varying (in space) wind-stress anomalies and the abrupt change in orientation of the mean along-SSF direction, from a mean of 81 . 8 ∘ ± 14 . 3 ∘ T between 50 . 5 ∘ and 70 . 5 ∘ W , to a mean of 51 . 3 ∘ ± 24 . 0 ∘ T between 70 . 5 ∘ and 74 . 5 ∘ W . A more complex Ekman coastal plume model that allows the upper layer to evolve to a uniform thickness through shear-induced mixing and a critical Richardson number criterion ( h c = variable ), overestimates onshore movement of the SSF south of Nantucket Shoals by a factor of 2–3 compared to August–October observations. While clearly not locally wind-forced, we speculate that a possible source of the seasonal, westward-propagating SSF meander is due to seasonal variability in the volume of shelf waters within this eastern-most region resulting from Labrador Current transport that is maximum (minimum) during fall (spring) upstream of the Tail of the Grand Banks and within the Labrador Sea. Comparisons of the seasonal movements of the satellite-derived surface SSF position with previously published sub-surface expressions of the SSF and shelf water volumes derived from hydrographic data collected within the Middle Atlantic Bight section of our domain, demonstrate decoupling of the surface wind-forced SSF from the sub-surface thermohaline-forced SSF over seasonal timescales for this westernmost region.

Large eddy simulation of stratified mixing in two-dimensional dam-break problem in a rectangular enclosed domain

Mixing in both coastal and deep ocean emerges as one of the important processes that determines the transport of pollutants, sediments and biological species, as well as the details of the global thermohaline circulation. Both the observations, due to their lack in space and time resolution, and most coastal and general circulation models due to inadequate physics, can only provide partial information about oceanic mixing processes. A new class of nonhydrostatic models supplemented with physically based subgrid-scale (SGS) closures, or so-called large eddy simulation ( LES), is put forth as another tool of investigation to complement observational and large-scale modeling efforts. However, SGS models have been developed primarily for homogeneous, isotropic flows. Here, four SGS models based on Smagorinsky eddy viscosity and diffusivity are tested for stratified flows in the context of 2D dam-break problem in a rectangular enclosed domain. This idealized testbed leads to a number of simplifications about the initial conditions, boundary conditions and geometry, while exhibiting the dynamically complex characteristics of stratified flows involving the interaction of shear-induced mixing and internal waves. Direct numerical simulations ( DNS) at high resolutions are taken as benchmark solutions. Under-resolved simulations without SGS terms (so-called DNS ∗) are used to quantify the impact of SGS stresses. The performance of LES is assessed by using the time evolution of the volume fraction of intermediate density water masses generated by mixing. The simulations are conducted using a nonhydrostatic high-order spectral element model Nek5000 developed to exhibit minimal numerical dissipation and dispersion errors, which is advantageous to quantify accurately the impact of SGS stresses. It is found that all tested SGS models lead to improved results with respect to those from DNS ∗. Also, SGS models allow for simulations with coarse resolutions that blow up in DNS ∗ due to lack of adequate dissipation where needed. The SGS model in which the vertical eddy diffusion is modulated via a function that depends on the Richardson number Ri shows the most faithful reproduction of mixed water masses at all resolutions tested. The sensitivity of the results to the tunable parameter of the SGS model, to changes in the Ri-dependent function and resolution of the turbulent overturning scales is shown.

An entropy-based measure of mixing at the tropopause

Qualitative analysis of tracer correlations is now a well established technique for investigating mixing in the tropopause transition layer. Generally, these studies rely on in situ data retrieved over short distances and time-scales. Using satellite data from HALOE, we introduce a simple quantitative analysis technique, based on entropy, to provide a climatology of mixing, from H2O:O3 tracer correlations. Results compare well with previous studies using Lagrangian-based estimates of effective diffusivity and equivalent lengths and also climatologies of tropopause folding. Further analysis techniques reveal characteristics of the transition layer, including its depth and position, leading to the distinction of three primary forms of mixing. Within our analysis domain, we estimate that half of total entropy can be attributed to subtropical ‘Rossby-driven’ tropopause folding events. The majority of the remaining entropy is associated with tropical convective mixing and a third form, possibly linked to shear-induced mixing at subtropical jet streaks. Copyright © 2006 Royal Meteorological Society

The flow generated in a continuously stratified rotating fluid by the differential rotation of a plane horizontal disc

Results are presented from a modelling investigation into the response of a rotating, linearly stratified fluid to local forcing induced by a differentially rotating smooth, horizontal disc. Attention was directed at cases in which the disc forcing is relatively strong, with Rossby number ε = ω / 2 Ω of order 1 or greater; here ω and Ω are the disc and background rotation frequencies, respectively. The principal flow dynamics resulting in the mixing and deformation of the initially stable density distribution were identified as (i) shear-induced mixing due to the local increase in fluid vorticity above the disc and (ii) meridional circulations produced by Ekman processes and the constraint of the container sidewall. Laboratory experiments revealed the growth of a mixed layer adjacent to the disc and the subsequent development of layers within the mixed region. Furthermore, the experiments showed that, even at relatively large ε , Ekman processes associated with background rotation constituted the dominant mechanism controlling development and evolution of the primary interface between mixed and unmixed fluid regions. Theoretical, energy-based scalings are derived to describe the growth rate of the interfacial region for ε ≳ O ( 1 ) which are consistent with the ε → ∞ limit corresponding to the Ω = 0 case. These scalings are shown to describe well the development of the density field within the forced flow.

Effect of molecular weight and shear on phase diagram of PS/PVME blend

The molecular weight dependence of the lower critical solution temperature of polystyrene (PS) and poly(vinyl methyl ether) blends was studied by laser light transmission. The temperature of phase separation was found to decrease with increasing PS molecular weight. In the steady shear flow conditions and near the critical temperature, shear was found to enhance fluctuations of concentration at relatively small shear rates, whereas it suppresses such fluctuations at high shear rates. The shift in Flory-interaction parameter Δχ was calculated from experimental data and its sign was used to predict shear-induced mixing or shear-induced demixing under flow field. The obtained experimental results were compared to Criado-Sancho et al. and Clarke-Mcleish models.

Phase Behavior of Aqueous Solutions of Bovine Serum Albumin in the Presence of Dextran, at Rest, and under Shear

The demixing conditions for aqueous solutions of bovine serum albumin (BSA, fraction V) and for joint solutions of BSA plus dextran (DEX, M(w) = 2000 kg/mol) were determined by turbidimetric measurements as a function of composition, temperature, and shear rate. Aqueous solutions of BSA phase separate upon heating. Within the region of BSA concentrations between 0.05 and 32 wt %, the demixing temperature, T1, falls from ca. 65 degrees C to an almost constant value of 45 degrees C. Adding DEX to the BSA solutions reduces the homogeneous region of the mixture drastically where the amount of DEX required to lower T1 to 25 degrees C decreases rapidly as the concentration of BSA is raised. Experiments concerning the influences of shear have been performed for the ternary system up to 500 s(-1). They demonstrate that the content of dextran determines the sign of the effect. At low DEX concentrations, the mechanical field favors the homogeneous state (shear-induced mixing), whereas the opposite effect (shear-induced demixing) is observed at high DEX concentrations. Possible reasons for this observation are discussed.

Shear-induced convective mixing in bottom boundary layers on slopes

Field data from a stratified lake demonstrate that buoyancy-driven convective mixing can be an important mechanism for the formation of well-mixed bottom boundary layers (BBLs) on slopes. Convective turbulence is caused by differential transport of stratified water masses along the slope of a basin. Because the current velocity usually decreases toward the sediment, water at some distance from the bottom is transported faster than is water below. During upslope flow, this process leads to transport of heavier water on top of lighter water and hence to unstable stratification within the BBLs. Analogously, strong BBL stratification occurs during downslope flow. High-frequency acoustic Doppler current profiler (ADCP) and temperature measurements in the BBLs of a lake revealed the cyclic occurrence of convective turbulence driven by periodic across-slope currents of internal seiching. The estimated maximum buoyancy flux within the BBLs was in good agreement with the highest observed dissipation rates of turbulent kinetic energy. This suggests that, in our specific case, classical bottom shear production and the mentioned buoyancy-driven (convective) production contributed by similar amounts to the turbulent kinetic energy.

Turbulent patches in a stratified shear flow

Turbulence measurements within an artificially generated turbulent patch embedded in a stratified shear flow are presented. The results indicate that the enhanced patch growth that has been observed at background gradient Richardson numbers on the order unity can be attributed to the onset of shear-induced mixing at the patch boundaries rather than enhanced interaction between turbulence and shear that causes increased turbulence levels within the patch.

Shear-induced mixing and transport from a rectangular cavity

Measurements were conducted in the vicinity and downstream of two-dimensional cavities filled with a dense miscible fluid subjected to purging by an overlying wall-bounded turbulent shear flow. Two cavities with aspect ratios 1 and 2 were used, based on previous observations that the mechanism for entraining dense fluid into the flow above is different for these cases. Scaling for the downstream variation of the vertical concentration (buoyancy) distribution of dense fluid is advanced based on dimensional arguments and tested using laser-induced fluorescence measurements, The mean flow and turbulent statistics in the vicinity and downstream of the cavity were also measured. A notable increase of shear stress and turbulent intensities was observed above the higher aspect ratio cavity due to intense vertical exchange between the cavity and the flow above. The influence of the cavity could be detected for several cavity widths, or distances equal to several eddy turnover times. However, the flow above the lower aspect ratio cavity exhibits dramatically less vertical exchange between the cavity and the flow above, as indicated by subtle wisps of fluid transported downstream by the free-stream flow. The shear stress and turbulent intensities for this case have only a minor influence of the cavity.

Ground‐Based Diffusion Experiments on Liquid Sn‐In Systems Using the Shear Cell Technique of the Satellite Mission Foton‐M1

This study reported in this paper was aimed at testing the shear cell that was developed for the satellite mission Foton-M1 to measure diffusion coefficients in liquid metals under microgravity (microg)-conditions. Thick Layer diffusion experiments were performed in the system Sn90In10 versus Sn under 1 g-conditions. For this system several microg-diffusion results are available as reference data. This combination provides a low, but sufficiently stable, density layering throughout the entire experiment, which is important to avoid buoyancy-driven convection. The experimental results were corrected for the influences of the shear-induced convection and mixing after the final shearing, both of which are typical for the shear cell technique. As the result, the reproducibility and the reliability of the diffusion coefficients in the ground-based experiments were within the limits of error of microg-data. Based on our results we discuss the necessary conditions to avoid buoyancy-driven convection.

Effect of shear flow on the phase behavior of an aqueous gelatin-dextran emulsion.

A rheo-optical methodology, based on small angle light scattering and transmitted light intensity measurements, has been used to study in situ and on a time resolved basis the shear induced morphology in ternary two-phase water-gelatin-dextran mixtures. Emulsions close to the binodal line as well as far from it have been investigated. It is shown that above a critical shear rate, shear-induced mixing occurs at the length scales probed by the laser light. It is hypothesized that the shear-induced homogenization is due to the shear forces that exceed the intermolecular forces of the self-association process of the gelatin. The isothermal phase diagram at a fixed shear rate has been determined. In addition, the structure evolution after cessation of flow has been studied. When flow is stopped after homogenization, phase separation occurs almost instantaneously. When subsequently applying a low shear rate, the structure coarsens due to coalescence of the dispersed droplets. The kinetics of this coalescence process is strain controlled.