Horizontal Velocity Profiles Research Articles

Observations of pockmark flow structure in Belfast Bay, Maine, Part 3: implications for sediment transport

Current observations and sediment characteristics acquired within and along the rim of two pockmarks in Belfast Bay, Maine, were used to characterize periods of sediment transport and to investigate conditions favorable to the settling of suspended sediment. Hourly averaged Shields parameters determined from horizontal current velocity profiles within the center of each pockmark never exceed the critical value (approximated with the theoretical model of Dade et al. 1992). However, Shields parameters estimated at the pockmark rims periodically exceed the critical value, consistent with conditions that support the onset of sediment transport and suspension. Below the rim in the near-center of each pockmark, depth-averaged vertical velocities were less than zero (downward) 60% and 55% of the time in the northern and southern pockmarks, and were often comparable to depth-averaged horizontal velocities. Along the rim, depth-averaged vertical velocities over the lower 8 m of the water column were primarily downward but much less than depth-averaged horizontal velocities indicating that suspended sediment may be moved to distant locations. Maximum grain sizes capable of remaining in suspension under terminal settling flow conditions (ranging 10–170 μm) were typically much greater than the observed median grain diameter (about 7 μm) at the bed. During upwelling flow within the pockmarks, and in the absence of flocculation, suspended sediment would not settle. The greater frequency of predicted periods of sediment transport along the rim of the southern pockmark is consistent with pockmark morphology in Belfast Bay, which transitions from more spherical to more elongated toward the south, suggesting near-bed sediment transport may contribute to post-formation pockmark evolution during typical conditions in Belfast Bay.

Observations of pockmark flow structure in Belfast Bay, Maine, Part 2: evidence for cavity flow

Pockmark flow circulation patterns were investigated through current measurements along the rim and center of two pockmarks in Belfast Bay, Maine. Observed time-varying current profiles have a complex vertical and directional structure that rotates significantly with depth and is strongly dependent on the phase of the tide. Observations of the vertical profiles of horizontal velocities in relation to relative geometric parameters of the pockmark are consistent with circulation patterns described qualitatively by cavity flow models (Ashcroft and Zhang 2005). The time-mean behavior of the shear layer is typically used to characterize cavity flow, and was estimated using vorticity thickness to quantify the growth rate of the shear layer horizontally across the pockmark. Estimated positive vorticity thickness spreading rates are consistent with cavity flow predictions, and occur at largely different rates between the two pockmarks. Previously modeled flow (Brothers et al. 2011) and laboratory measurements (Pau et al. 2014) over pockmarks of similar geometry to those examined herein are also qualitatively consistent with cavity flow circulation, suggesting that cavity flow may be a good first-order flow model for pockmarks in general.

Characterization of buoyant flow stratification behaviors by Richardson (Froude) number in a tunnel fire with complex combination of longitudinal ventilation and ceiling extraction

A series of experiments were carried out in a model-scale tunnel [72m (length)×1.5m (width)×1.3m (height)] to investigate the buoyant flow stratification behaviors in a tunnel fire with complexity of combination of longitudinal ventilation and ceiling extraction, which had not been studied before. The horizontal traveling velocity and vertical temperature profile were measured. The buoyant flow stratification conditions were visualized by a laser-sheet, as well as determined objectively by the vertical temperature profile measured. Buoyancy and inertial force are the two important factors influencing the buoyancy stratification. The interaction between them can be expressed by the Froude number or Richardson number. It was found that the buoyant stratification pattern was divided into three regimes. At regime I (Ri>2.0 or Fr<0.66), the buoyant stratification was stable and with a clear interface between the upper buoyant flow layer and the lower air layer. At regime II (1.4<Ri<2.0 or 0.66<Fr<0.8), the buoyant stratification was basically stable, but some vortexes existed at the interface. At regime III (Ri<1.4 or Fr>0.8), a strong mixing existed between the upper buoyant flow and the lower air flow, that the buoyant flow stratification became unstable.

Flow Field and Heat Transfer Investigation of a Confined Laminar Slot Air Jet on a Solid Block

A numerical investigation is carried out to investigate the fluid flow field and heat transfer characteristics of two dimensional laminar incompressible jet flows. Simulations are performed for a single vertical slot jet on a block mounted on the bottom wall and the top wall is confined by a parallel wall surface. The present study reveals the vital impact of the Aspect Ratio (AR) and Reynolds number (Re) on the fluid flow and heat transfer characteristics over a wide range. It is observed that the presence of a solid block in the channel increases the overall unsteadiness in the flow. The correlation between the Reynolds numbers and reattachment length is suggested, for all Aspect Ratios (ARs). The horizontal velocity profile at various downstream locations for all ARs is employed to find out the location where the flow gets fully developed. The primary peak value of the Nusselt number (Nu) occurs at the stagnation point, and the secondary peak is at a downstream location. The average Nusselt number increases with the increase of Reynolds number and decreases with the increase of the distance between the jet and the block. The heat transfer correlations between the Reynolds number and Nusselt number are analyzed for constant wall temperature boundary conditions.

Chemo‐thermo‐mechanically coupled seismic analysis of methane hydrate‐bearing sediments during a predicted Nankai Trough Earthquake

SummaryIn the present study, we have developed a numerical method which can simulate the dynamic behaviour of a seabed ground during gas production from methane hydrate‐bearing sediments. The proposed method can describe the chemo‐thermo‐mechanical‐seismic coupled behaviours, such as phase changes from hydrates to water and gas, temperature changes and ground deformation related to the flow of pore fluids during earthquakes. In the first part of the present study, the governing equations for the proposed method and its discretization are presented. Then, numerical analyses are performed for hydrate‐bearing sediments in order to investigate the dynamic behaviour during gas production. The geological conditions and the material parameters are determined using the data of the seabed ground at Daini‐Atsumi knoll, Eastern Nankai Trough, Japan, where the first offshore production test of methane hydrates was conducted. A predicted earthquake at the site is used in the analyses.Regarding the seismic response to the earthquake which occur during gas production process, the wave profiles of horizontal acceleration and horizontal velocity were not extensively affected by the gas production. Hydrate dissociation behaviour is sensitive to changes in the pore pressure during earthquakes. Methane hydrate dissociation temporarily became active in some areas because of the main motion of the earthquake, then methane hydrate dissociation brought about an increase in the average pressure of the fluids during the earthquake. And, it was this increase in average pore pressure that finally caused the methane hydrate dissociation to cease during the earthquake. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Large Eddy Simulation of Unidirectional and Wave Flows through Vegetation

AbstractMassively parallel large eddy simulation (LES) experiments were conducted to study the flow fields developed by unidirectional flow over submerged vegetation and wave flow-through emergent vegetation. For the submerged vegetation, vertical profiles of mean and turbulent horizontal and vertical velocities were found to be in good agreement with laboratory experiments. Canopy-averaged bulk drag coefficient calculated from the depth-integrated forces on the cylinders compares well with empirical measurements. For the emergent vegetation, wave-induced drag forces were calculated, and the inertia and pressure-drag coefficients were compared with laboratory experiments, which were found to be in good agreement. Vertical variation of forces and moments about the stem base are presented and compared with a single stem case under a variety of wave conditions and Keulegan-Carpenter (KC) numbers. It is seen that at low KC numbers the effect of the inertia force is significant. The vertical variation of the v...

Velocity characteristics in boundary layer flow caused by solitary wave traveling over horizontal bottom

The characteristics of horizontal velocity in the bottom boundary-layer flow induced by a solitary wave propagating over a horizontal bottom are presented experimentally, using high-speed particle image velocimetry (HSPIV). The ratio of wave height to water depth varies from 0.096 to 0.386 and the flow inside the boundary layer is laminar. The results show that the horizontal velocity profiles can be mainly classified into two categories with respect to the passing of the solitary wave-crest at the measuring section: the pre-passing (or acceleration) phases under favorable pressure gradient and post-passing (or deceleration) phases under adverse pressure gradient. For the velocity distributions obtained during the pre-passing phases, a nonlinear regression analysis was used to precisely determine the time-dependent characteristic length and velocity scales underlying these profiles. A similarity profile of the horizontal velocity is established first using the time-dependent free-stream velocity and boundary layer thickness as the characteristic velocity and length scales, respectively. In addition, the displacement thickness, the momentum thickness, and the energy thickness are also considered as alternative length scales. All these four representative thicknesses are closely related to each other, demonstrating that any one amongst them can be regarded as the characteristic length scale. The forms of similarity profiles for the non-dimensional velocity distributions are somewhat analogous to the results of steady boundary layer flow over a thin plate under with pressure gradient, but with different coefficients or powers. While during the post-passing phases, flow reversal which acts like an unsteady wall jet and moves in the opposite direction against the wave propagation occurs after the passage of solitary wave-crest. The thickness of flow reversal layer increases with time. A similarity profile is proposed for the velocity distributions corresponding to occurrence of the extreme value in the maximum negative velocity of flow reversal. Variations of the maximum negative velocity and the thickness of flow reversal with the time right after the start of flow reversal are also discussed in detail. Moreover, the non-dimensional time leads of the horizontal velocities at different heights in the boundary layer over the free-stream velocity are evidenced to be more noticeable toward the bottom, and also in lower ratio of wave height to water depth. A similarity profile for the non-dimensional time lead versus the non-dimensional height above the bottom surface is also presented.

Numerical study of natural convection characteristics of nanofluids in an enclosure using multiphase model

The natural convective heat transfer and flow characteristics of nanofluids in an enclosure are numerically simulated using the multiphase-flow model and single phase model respectively. The simulated results are compared with the experimental results from the published papers to investigate the applicability of these models for nanofluids from a macro standpoint. The effects of Rayleigh number, Grashof number and volume concentration of nanoparticles on the heat transfer and flow characteristics are investigated and discussed. Comparisons of the horizontal and vertical central dimensionless velocity profiles between nanofluid and water for various Grashof numbers are studied. In addition, both streamline contours and isotherms lines for different volume concentrations of nanofluids are analyzed as well. The study results show that a great deviation exists between the simulated result of the single phase model and the experimental data on the relation of Nusselt number and Rayleigh number, which indicates that the single phase model cannot reflect the heat transfer characteristic of nanofluid. While the simulated results using the multiphase-flow model show a good agreement with the experimental data of nanofluid, which means that the multiphase-flow model is more suitable for the numerical study of nanofluid. For the natural convection, the present study holds the point that using Grashof numbers as the benchmark would be more appropriate to describe the heat transfer characteristics of nanofluid. Moreover, the simulated results demonstrate that adding nanoparticles into the base fluid can enhance both the motion of fluid and convection in the enclosure significantly.

Effect of Structure of Internal Waves on Energy Transfer and Flow Control Between South and Middle Basins of Caspian Sea

In this study, role of internal waves in controlling stratified exchange flows between south and middle basins of Caspian Sea and energy transfer have been studied. The studies have been conducted based on field and theoretical studies based on numerical calculations. In this investigation, Caspian Sea has been considered as stratified and Boussinesq approximation has been considered. In equations governing the movement, cohesion and compressibility have been neglected. In the field studies, investigation of density profiles indicate signs of stratified structure which so far has been attributed to dual distribution convection phenomenon, but by considering density ratio profile and values of density ratio which are mostly negative numbers, the factor causing stratified structure of Caspian Sea can be attributed to existence of internal waves. Density field in these two basins indicate that the middle basin has higher average density compared to the south basin, this fact can cause creation of a gravity exchange flow. This exchange flow causes creation of internal waves in this sea that can have a modal structure towards vertical direction. In theoretical studies, the two middle and south basins of Caspian Sea are networked in two dimension x-z systems and equations governing movement are solved through a numerical method by using finite difference method and the vertical velocity values obtained in 290 points of the network was almost 10&lt;sup&gt;-6&lt;/sup&gt; to 10&lt;sup&gt;-4&lt;/sup&gt; m/s, meaning that vertical movements are much smaller. Values obtained for horizontal velocity are almost 10&lt;sup&gt;-3&lt;/sup&gt; to 10&lt;sup&gt;-1&lt;/sup&gt; m/s. Vertical and horizontal velocity profiles obtained from solution of these equations and also density profile obtained in four integration periods indicate that as a result of passage of gravity flow between the two basins, density in various points of the two basins change. The structure created from internal waves on the crest causes creation of shear strata observed. This structure can be effective in exchange of the two basins. Therefore, in transfer and energy conversion, identification of the created strata is of a high importance.

Numerical Investigation on Visualizations of Confined Air Flow in a Slot Jet Inside a Rectangular Channel

In the present numerical investigation, the flow field of confined slot air jet in a rectangular computational domain is reported. In the present work the flow field parameters like reattachment length, vortex center and horizontal velocity profiles for various Reynolds numbers and for various aspect ratios are presented .The present study reveals that the vortex centers are moving in a downstream direction with increase in Reynolds number. The reattachment length is directly dependent on the Reynolds numbers. In case of vortex dynamics, the vortex size is indirectly dependent on the inlet jet width. In the present investigation, SIMPLE algorithm is used to solve the governing equations. It is concluded that the aspect ratio and the Reynolds number are playing dominant roles in flow field of the present computational domain.

Experimental investigation of the impact of macroalgal mats on the wave and current dynamics

Macroalgal mats of Ulva intestinalis are becoming increasingly common in many coastal and estuarine intertidal habitats, thus it is important to determine whether they increase flow resistance, promote bed stability and therefore reduce the risk of erosion favoring tidal flooding or degradation of coastal lagoons. Venier et al. (2012) [6] studied the impact of macroalgal mats of Ulva intestinalis on flow dynamics and sediment stability for uniform flow. Here we extend their experimental work to the case of vegetation under the combined action of waves and currents. These hydrodynamic conditions are very common in many shallow coastal environments and lagoons. The experimental facility employed in the present study and the series of flow runs are the same as that used by Venier et al. (2012)[6]. However, waves have been superposed to uniform current flowing firstly over a mobile sediment bed covered with U. intestinalis, then over a bare sediment surface. For the depth, wave and current conditions considered in the experiments, the time-averaged vertical profile of horizontal velocity for the case of coexisting waves and current turns out to be very close to that observed for a pure current, both with and without vegetation. However, contrary to what was observed in the case of a unidirectional current, in the presence of waves the time averaged velocity profile is only weakly influenced by the vegetation, whose main effect is to attenuate velocity oscillations induced by waves and to slightly increase the overall bed roughness.

Turbulent Rayleigh–Bénard convection in spherical shells

We simulate numerically Boussinesq convection in non-rotating spherical shells for a fluid with a Prandtl number of unity and for Rayleigh numbers up to $10^{9}$. In this geometry, curvature and radial variations of the gravitational acceleration yield asymmetric boundary layers. A systematic parameter study for various radius ratios (from ${\it\eta}=r_{i}/r_{o}=0.2$ to ${\it\eta}=0.95$) and gravity profiles allows us to explore the dependence of the asymmetry on these parameters. We find that the average plume spacing is comparable between the spherical inner and outer bounding surfaces. An estimate of the average plume separation allows us to accurately predict the boundary layer asymmetry for the various spherical shell configurations explored here. The mean temperature and horizontal velocity profiles are in good agreement with classical Prandtl–Blasius laminar boundary layer profiles, provided the boundary layers are analysed in a dynamical frame that fluctuates with the local and instantaneous boundary layer thicknesses. The scaling properties of the Nusselt and Reynolds numbers are investigated by separating the bulk and boundary layer contributions to the thermal and viscous dissipation rates using numerical models with ${\it\eta}=0.6$ and with gravity proportional to $1/r^{2}$. We show that our spherical models are consistent with the predictions of Grossmann &amp; Lohse’s (J. Fluid Mech., vol. 407, 2000, pp. 27–56) theory and that $\mathit{Nu}(\mathit{Ra})$ and $\mathit{Re}(\mathit{Ra})$ scalings are in good agreement with plane layer results.

Effects of variable viscosity and thermal conductivity on MHD flow and heat transfer of a dusty fluid

Abstract The problem of magnetohydrodynamic flow and heat transfer of a viscous, incompressible and electrically conducting dusty fluid over an unsteady stretching sheet is analyzed numerically. The fluid viscosity and thermal conductivity are assumed to vary as an exponential function of temperature. The governing fundamental equations are approximated by a system of nonlinear ordinary differential equations using similarity transformations. The obtained similarity equations are solved numerically using RKF-45 method. Numerical computation has been carried out for horizontal velocity profiles, temperature, Nusselt number and skin friction coefficient for various values of the flow parameters that are presented for both VWT and VHF respectively. A comparison with previously published work is performed and the results are found to be in good agreement.

Experimental studies and modeling of surface bubble behaviour in froth flotation

Froth flotation is a versatile, widely used beneficiation technique employing air bubbles to selectively pick up certain particles in aqueous medium. The performance of the flotation process is significantly affected by froth stability and mobility, posing the need for precise control of the froth phase. The present paper aims to understand the motion of bubbles entering the froth phase from the pulp phase at different locations. The horizontal velocities of air bubbles across the top surface of the froth containing fine coal particles were measured. The results showed that at the region farthest from the froth discharge lip, no horizontal movement of the surface bubbles could be observed, and when approaching the lip there would be an increase in the horizontal velocity. The measured velocity profile was fitted to a froth model that considers the cumulative air recovery as a function of location. Six different types of cumulative air recovery functions were tested. The coefficient of determination (R2) and the Akaike information criterion were applied to select the cumulative air recovery function with best fit to describe the horizontal velocity profile. The selected cumulative air recovery function was in a simple power-law form.

Numerical Modeling of Waves in the Port of Manzanillo, Mexico by Cnoidal Theory

This paper presents the application of one computer program developed to calculate the physical characteristics of the progressive water waves using cnoidaltheory of Keulegan and Patterson: profile of water surface, wave length, horizontal and vertical orbital velocities, horizontal and vertical orbital accelerations, period, and under water surface pressure. The Turbo-Pascal programming language was used. CNOIDAL program requires the following data to be introduced: depth, height and phase angle of waves, as the depth ‘z’ of the particle to be analyzed. In the first part of the program, the Newton-Raphsonmethod is used to determine the wave length. In its second part, the nine physical characteristics of waves, providing of equations with elliptic Jacobeans functions, are calculated: profile of water surface, celerity, wave length, horizontal and vertical orbital velocity, horizontal and vertical orbital acceleration, under water surface pressure,and period. A measurement of some characteristics of the waves in the port of Manzanillo was realized by twelve months in the year of 2013 and 2014 using the dates obtained by the Transportation Mexican Institute (TMI) in this port. Results after application this computer program validate the application region proposal by Littman and Struik and the experimental works of LéMehauté, Divoky and Lyn in the Tetra Tech wave tank, of 32 meters of length, square across section of 1.219 meters and waves generator with a speed control in a rank from 1 to 12seconds of period and with waves ranks 0.244 m/s2≥ d/T2≥ 0.015 m/s2. These results were compared with the calculus of the program proposed in this work for the free surface profile, speeds and accelerations of the particles and it was observed a very good accurate by the Keulegan and Patterson cnoidal theory.

Numerical Investigation on the Fluid Flow Characteristics of a Laminar Slot Jet on Solid Block Mounted on a Horizontal Surface

Numerical simulation is carried out to investigate the flow characteristics of two-dimensional laminar incompressible slot jet flows. Simulations are done for a vertical slot jet on a block at the bottom wall, and the top wall is confined by the parallel surface. The reattachment length, detachment length, vortex center and the coefficient of friction (Cf) are analyzed for different types of flow patterns. The correlation between the Reynolds number (Re) with vortex center and reattachment length is recommended. A detailed study is reported on the horizontal velocity profiles at various downstream locations by varying the aspect ratio (AR) (2 ≤ AR ≤ 5), block width (0.25 ≤ w/Dh ≤ 1.75), block height (0.25 ≤ h/Dh ≤ 1.0) and the jet exit Reynolds numbers (100 ≤ Re ≤ 300). The critical Reynolds number for the formation of the secondary vortex is obtained. The numerical results indicated that the Cf value increases while decreasing the distance between the jet and the impingement block. It is found that the effects of AR and Re are more influencing on the fluid flow field, compared to the block width and the block height.

On the nonequivalent barotropic structure of the Antarctic Circumpolar Current: An observational perspective

AbstractWe examine the vertical structure of the horizontal flow and diagnose vertical velocities in the Antarctic Circumpolar Current (ACC) near the Kerguelen Plateau using EM‐APEX profiling floats. Eight floats measured horizontal velocity, temperature, and salinity profiles to 1600 dbar, with a vertical spacing of 3–5 dbar four times per day over a period of approximately 3 months. Horizontal velocity profiles show a complex vertical structure with strong rotation of the velocity vector through the water column. The distribution of rotation angles from 1247 profiles is approximately Gaussian and rotations of either sign are equally likely. Forty percent of profiles with speed greater than 5 cm s−1 have a depth‐integrated rotation of less than 15 degrees over 1300 dbar, while the other 60% demonstrate significantly stronger rotation. Consequently, most profiles do not conform to the equivalent barotropic model (deep flow parallel and proportional to the surface flow) used in simplified dynamical models and in Gravest Empirical Mode climatologies of the ACC. Nevertheless, since we find the mean rotation to be zero, an equivalent barotropic assumption is valid to first order. Vertical velocities inferred using conservation of mass and a gradient wind balance in natural coordinates have magnitudes on the order of 100 m/day. We find robust patterns of upwelling and downwelling phase‐locked to meanders in the flow, as found in earlier studies. With the advent of high‐resolution observations such as those presented here, and high‐resolution models, we can advance to a more complete understanding of the rich variability in ACC structure that is neglected in the equivalent barotropic model.

Perturbation theory and numerical modelling of weakly and moderately nonlinear dynamics of the incompressible Richtmyer–Meshkov instability

AbstractA study of incompressible two-dimensional (2D) Richtmyer–Meshkov instability (RMI) by means of high-order perturbation theory and numerical simulations is reported. Nonlinear corrections to Richtmyer’s impulsive formula for the RMI bubble and spike growth rates have been calculated for arbitrary Atwood number and an explicit formula has been obtained for it in the Boussinesq limit. Conditions for early-time acceleration and deceleration of the bubble and the spike have been elucidated. Theoretical time histories of the interface curvature at the bubble and spike tip and the profiles of vertical and horizontal velocities have been calculated and favourably compared to simulation results. In our simulations we have solved 2D unsteady Navier–Stokes equations for immiscible incompressible fluids using the finite volume fractional step flow solver NGA developed by Desjardins et al. (J. Comput. Phys., vol. 227, 2008, pp. 7125–7159) coupled to the level set based interface solver LIT (Herrmann, J. Comput. Phys., vol. 227, 2008, pp. 2674–2706). We study the impact of small amounts of viscosity on the flow dynamics and compare simulation results to theory to discuss the influence of the theory’s ideal inviscid flow assumption.

Ground-Based Remote Sensing of the ABL Structure in Moscow and Its Use to Estimate Pollutant Surface Emission Rates

AbstractCurrently used methods to estimate surface pollutant emissions require a set of specific air-sampling surveys. Data from a network of ground-based sodars and a network of air-quality stations in Moscow, Russia, are used to estimate the emission rates of carbon monoxide (CO) and nitric oxide (NO). The sodar network, consisting of three “LATAN-3” Doppler sodars and three “MTP-5” microwave temperature profilers, is used to measure the vertical profiles of vertical and horizontal wind velocity, wind direction, and temperature, which are used to determine the average mixing-layer height. The network of ground-based air-quality stations, consisting of 17 automated stations distributed uniformly across Moscow, continuously measured the CO and NO concentrations. This study focuses on an anticyclonic episode of high surface pressure over Moscow during 30 July–1 August 2012. After sunrise, the solar-induced convection effectively moderated the pollutant levels in the lowest 100–200 m. After sunset, convective mixing stopped and the wind weakened, which allowed CO and NO to reach hazardous levels. With an assumption of an average mixing-layer height of 150 m, the resulting estimate of surface emission of CO is ~6 μg m−2 s−1, whereas that for NO is ~0.6 μg m−2 s−1.

Phased-array Doppler sonar measurements at the equator: Currents or swimming?

A 64-channel 200 kHz phased array Doppler sonar (PADS) was deployed on the Equator at 140 W, sampling a vertical slice of the ocean, from 9 m to 200 m depth by 100 degrees, twice per second. The instrument was operated for two nearly continuous time-series, Oct. 10–20 and Oct.24 to Nov. 3, 2012. While the PADS was operated off the Starboard side of the R/V Revelle, a “Fast-CTD” (FCTD) was simultaneously operated off the port stern, sampling to 250 m every 2.5 min. Headway was maintained at less than 1 m/s relative to the surface flow (which was small, in contrast to the ~1.5 m/s undercurrent at 100 to 130 m depth). Because of this slow headway, motile scatterers were able to develop ship-centric swimming patterns, particularly at night. This, in turn, introduced some subtly non-physical characteristics in the estimated vertical velocities in particular. Animations of the backscatter intensity reveal a variety of scales and speeds of the scatterers. Visual nighttime inspection revealed a preponderance of small squid (&amp;lt; 30 cm) with the occasional large predator passing rapidly through (not identified). In spite of this biological interference, reasonable profiles of horizontal velocity were produced via a simple de-spiking selector.