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Oceanic Engineering, IEEE Journal of

Issue 1 • Date Jan. 2007

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Displaying Results 1 - 25 of 28
  • Table of contents

    Page(s): C1 - C4
    Save to Project icon | Request Permissions | PDF file iconPDF (42 KB)  
    Freely Available from IEEE
  • IEEE Journal of Oceanic Engineering publication information

    Page(s): C2
    Save to Project icon | Request Permissions | PDF file iconPDF (26 KB)  
    Freely Available from IEEE
  • Guest Editorial Special Issue on Mine Burial Processes

    Page(s): 1 - 2
    Save to Project icon | Request Permissions | PDF file iconPDF (388 KB)  
    Freely Available from IEEE
  • Mine Burial Prediction: A Short History and Introduction

    Page(s): 3 - 9
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1165 KB) |  | HTML iconHTML  

    Naval mines have been in use for over 200 years. They are a cheap and effective way to significantly affect naval operations. Bottom mines in shallow water are particularly difficult to find when they are partially or wholly buried. The U.S. Office of Naval Research (Arlington, VA) and the Naval Research Laboratory (Stennis Space Center, MS) sponsored a six-year-long program to upgrade the capability to predict mine burial. The program consisted of laboratory studies, computer modeling, and field observation programs. Results of the studies have been combined into stochastic predictive programs that utilize state of the art process models and incorporate uncertainty in model capability and in our ability to know the correct values of model inputs. View full abstract»

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  • Behavior of a Large Cylinder in Free-Fall Through Water

    Page(s): 10 - 20
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (952 KB) |  | HTML iconHTML  

    This paper presents results of experimental deployment of a large instrumented cylinder of variable nose geometry and center of mass offset (CMO) in free-fall in realistic environment. Data on four tests series in the Gulf of Mexico are presented and analyzed statistically. The stochastic nature of the problem of the cylinder free-falling through water is outlined and described as an input to the subsequent impact burial prediction package. Significance of the CMO on the behavior of the cylinder is underlined. Influence of the release conditions on trajectory is discussed and found to affect the behavior of the cylinders only in the first 3.5 m of free-fall in water. Beyond this depth, quasi-stable (in the mean sense) conditions are achieved. Effects of three different nose shapes-blunt, hemispherical, and chamfered-on cylinder behavior are analyzed and found to have a pronounced influence on the fall trajectory. The blunt nose shape appears to be hydrodynamically most stable in free-fall. Apparent periodicity in motions of all cylinders were noted and were found to be the function of the CMO and nose shape primarily. Implications of these and other findings on modeling and impact burial predictions are discussed. View full abstract»

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  • Deterministic and Stochastic Predictions of Motion Dynamics of Cylindrical Mines Falling Through Water

    Page(s): 21 - 33
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1498 KB) |  | HTML iconHTML  

    A physics-based computational model has been developed that is capable of reliably predicting the motion of a 3-D mine-shaped object impacting the water surface from the air, and subsequently, dropping through the water toward the sea bottom. This deterministic model [mine's six-degree-of-freedom dynamics (MINE6D)] accounts for six-degree-of-freedom motions of the body including unsteady hydrodynamic interaction effects. MINE6D allows for physics-based modeling of other hydrodynamic effects due to water impact, viscous drag associated with flow separation and vortex shedding, air entrainment, and realistic flow environments. To demonstrate the efficacy of the model, we compare deterministic MINE6D predictions with tank drops tests and field measurements. MINE6D captures the myriad of complex 3-D motions of cylindrical mines observed in field and laboratory experiments. For relatively simple straight motions, it obtains quantitative comparisons with the field measurements for the kinematics of mines freely dropping in the water including water impact and air cavity effects. In practical applications, the environments are often quite irregular, and the releasing conditions are also with uncertainties. To provide some guidance in understanding and interpreting statistical characterizations of mine motions in practical environments, we perform Monte Carlo simulation using MINE6D. These statistical results are not only the essential input for stochastic bottom impact and burial predictions of mines but also useful for the design of mines. View full abstract»

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  • Mine-Impact Burial Model (IMPACT35) Verification and Improvement Using Sediment Bearing Factor Method

    Page(s): 34 - 48
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2201 KB) |  | HTML iconHTML  

    Recently, a 3-D model (IMPACT35) was developed to predict a falling cylindrical mine's location and orientation in air-water-sediment columns. The model contains the following three components: 1) triple coordinate transform, 2) hydrodynamics of falling rigid object in a single medium (air, water, or sediment) and in multiple media (air-water and water-sediment interfaces), and 3) delta method for sediment resistance with the transient pore pressure. Two mine-impact burial experiments were conducted to detect the mine trajectory in water column [Carderock Division, Naval Surface Warfare Center (NSWC), West Bethesda, MD, on September 10-14, 2001], and to measure the mine burial volume in sediment (Baltic Sea in June 2003). The existing IMPACT35 predicts a mine's location and orientation in the water column, but not in the sediment column. Since sediment resistance largely affects the mine burial depth and orientation in sediment, a new method (bearing factor) is proposed to compute the sediment resistant force and torque. The improvement of IMPACT35 with the bearing factor method is verified using the data collected from the Baltic Sea mine-impact burial experiment. The prediction error satisfies near-Gaussian distribution. The bias of the burial volume (in percent) prediction reduces from 11% using the delta method (old) to 0.1% using the bearing factor method (new). Correspondingly, the root-mean-square error (rmse) reduces from 26.8% to 15.8%. View full abstract»

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  • Effect of Rate-Dependent Soil Strength on Cylinders Penetrating Into Soft Clay

    Page(s): 49 - 56
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1086 KB) |  | HTML iconHTML  

    This paper presents a predictive model for undrained penetration of cylinders into soft seafloor soils. The penetration depth will depend on the velocity of the cylinder as it touches down at the seafloor, and the net deceleration of the cylinder as it is acted on by forces of self-weight, soil buoyancy, and soil-shearing resistance. The soil-shearing resistance force increases as a function of penetration depth and, due to the dependence of undrained shear strength on strain rate, penetration velocity. This paper presents finite element (FE) simulations that quantify both effects and form the basis of a simplified soil-resisting force model. Strain-rate effects are modeled within a framework of rate-dependent plasticity, with shearing resistance increasing semilogarithmically with increasing strain rate above a certain threshold strain rate. With all forces acting on the cylinder, estimated penetration depths are predicted from simple equations of motion for a single particle. Comparisons to laboratory tests involving penetration of cylinders into soft reconstituted marine clay show reasonable agreement between model predictions and measurements. View full abstract»

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  • Seafloor Properties From Penetrometer Tests

    Page(s): 57 - 63
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2605 KB) |  | HTML iconHTML  

    Quasi-static and freely falling dynamic penetrometers are currently in extensive use for measuring the mechanical properties of sediments composing the littoral seafloor. Sediments in this zone are often inhomogeneous both laterally and with depth so that it is difficult to predict burial of mines and other objects when relying on models that assume uniform, homogeneous sediment. The results of penetrometer tests discussed in this paper show that there can be a wide spread in the penetration resistance that is measured depending on the degree of sediment inhomogeneity and the rate of penetration. Moreover, the dilative response of granular strata appears to further complicate matters because of the sudden, large changes in shear strength that can occur. As a result, mine burial models currently in use, which often rely on simple strain-rate factors and shear strength determined from experiments utilizing uniform, reconstituted sediment, do not appear to be adequate to handle real in situ conditions in many cases. The objective of this paper is to obtain a better understanding of in situ properties and how they may be incorporated into various burial models. View full abstract»

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  • An Acoustic-Instrumented Mine for Studying Subsequent Burial

    Page(s): 64 - 77
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3676 KB) |  | HTML iconHTML  

    The U.S. Navy is supporting the research to develop and validate stochastic, time-dependent, mine burial prediction models to aid the tactical decision making process. This research requires continuous monitoring of both mine behavior during burial, and the near-field processes responsible for burial. A new instrumented mine has been developed that far exceeds the capabilities of the earlier optically instrumented mine in terms of the burial processes that can be measured. The acoustic-instrumented mine (AIM) utilizes acoustic transducers to measure burial and scour, localized flow rates, and sediment size and concentration in the water column. The AIM also includes sensors for measuring mine orientation and movement, as well as oceanographic information such as significant waveheights, wave period, and water temperature. Four AIMs were constructed and deployed during the Indian Rocks Beach (IRB, FL) and Martha's Vineyard Coastal Observatory (MVCO, Edgartown, MA) mine burial experiments. The results from the field experiments have proven that the sensor suite is viable in providing a wealth of data that are critical in understanding and modeling the complex subsequent burial process. View full abstract»

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  • Scour and Burial Mechanics of Objects in the Nearshore

    Page(s): 78 - 90
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1253 KB) |  | HTML iconHTML  

    A process-based, numerical, hydrodynamic vortex lattice mine scour/burial model (VORTEX) is presented that simulates scour and burial of objects of arbitrary shape resting on a granular bed in the nearshore. There are two domains in the model formulation: a far-field where burial and exposure occur due to changes in the elevation of the seabed and a near-field involving scour and transport of sediment by the vortices shed from the object. The far-field burial mechanisms are based on changes in the equilibrium bottom profiles in response to seasonal changes in wave climate and accretion/erosion waves spawned by fluxes of sediment into the littoral cell. The near-field domain consists of one grid cell extracted from the far-field that is subdivided into a rectangular lattice of panels having sufficient resolution to define the shape of the object. The vortex field induced by the object is constructed from an assemblage of horseshoe vortices excited by local pressure gradients and shear over the lattice panels. The horseshoe vortices of each lattice panel release a pair of vortex filaments into the neighboring flow. The induced velocity of these trailing vortex filaments causes scour of the neighboring seabed and induces hydrodynamic forces on the object. Scour around the object and its subsequent movement into the scour depression contribute to burial, while far-field changes in local sand level may increase burial depth or expose the object. Scour and burial predictions of mines and mine-like objects were tested in field experiments conducted in the nearshore waters off the Pacific coast of California at Scripps Pier, the Gulf Coast of Florida at Indian Rocks, and off the Atlantic coast of Massachusetts at Martha's Vineyard. Model predictions of mine scour and burial are in reasonable agreement with field measurements and underwater photographs. View full abstract»

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  • Measured and Predicted Burial of Cylinders During the Indian Rocks Beach Experiment

    Page(s): 91 - 102
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1696 KB) |  | HTML iconHTML  

    Burial of instrumented mine-like cylinders as a result of wave-induced scour was measured during experiments conducted in shallow water (15-16 m) with fine-sand (133-mum) and coarse-sand (566-mum) sediments off Indian rocks beach (IRB), FL. scour pits developed around the instrumented cylinders in the fine-sand site when significant waveheights exceeded 2 m, causing the cylinders to pitch, then roll into the developing scour pits, often changing heading to align parallel with the wave crest. Final cylinder burial was nearly 40 cm (about 70%-80% mine diameter) relative to the sediment-water interface, but only 20%-50% relative to surface area covered. The difference was caused by the lack of complete infilling of scour pits. Little development of scour pits and burial was noted on the coarse-sand site and the cylinders buried to only 20%-40% of the cylinder diameter below the sediment surface. Burial results, although variable, are in general agreement with the wave-induced scour model developed by Trembanis et al. (2007) for the fine sand, but not for the coarse sand where measured burial was much less than predicted. View full abstract»

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  • Multibeam Observations of Mine Burial Near Clearwater, FL, Including Comparisons to Predictions of Wave-Induced Burial

    Page(s): 103 - 118
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2152 KB) |  | HTML iconHTML  

    A Kongsberg Simrad EM 3000 multibeam sonar (Kongsberg Simrad, Kongsberg, Norway) was used to conduct a set of six repeat high-resolution bathymetric surveys west of Indian Rocks Beach (IRB), just to the south of Clearwater, FL, between January and March 2003, to observe in situ scour and burial of instrumented inert mines and mine-like cylinders. Three closely located study sites were chosen: two fine-sand sites, a shallow one located in 13 m of water depth and a deep site located in 14 m of water depth; and a coarse-sand site in 13 m. Results from these surveys indicate that mines deployed in fine sand are nearly buried within two months of deployment (i.e., they sunk 74.5% or more below the ambient seafloor depth). Mines deployed in coarse sand showed a lesser amount of scour, burying until they present roughly the same hydrodynamic roughness as the surrounding rippled bedforms. These data were also used to test the validity of the Virginia Institute of Marine Science (VIMS, Gloucester Point, VA) 2-D burial model. The model worked well in areas of fine sand, sufficiently predicting burial over the course of the experiment. In the area of coarse sand, the model greatly overpredicted the amount of burial. This is believed to be due to the presence of rippled bedforms around the mines, which affect local bottom morphodynamics and are not accounted for in the model, an issue currently being addressed by the modelers. This paper focuses specifically on two instrumented mines: an acoustic mine located in fine sand and an optical instrumented mine located in coarse sand. View full abstract»

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  • Full-Scale Mine Burial Experiments in Wave and Current Environments and Comparison With Models

    Page(s): 119 - 132
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    A mine burial field experiment was carried out on two sandy seafloors between January and April 2004 in the Bay of Brest, France. Burial recording mines (BRMs) were used to measure burial and mine orientation at 15-min intervals. Sonar and bottom photographs were also used to characterize sediment morphology and mine burial. These observations are compared with the predictions of mine burial using the following three models: a momentary liquefaction model, a current-induced scour model, and a wave-induced scour model. Analysis combines mine burial data, sediment data, seabed observations, and hydrodynamic measurements. At the first site, ldquoRascas,rdquo the seabed dynamics are dominated by tides and river runoff. Almost no mine burial was measured during the experiment which is in agreement with predictions of mine burial models (current-induced scour and liquefaction). Dynamics at the second site, ldquoBertheaume,rdquo are driven by tides and ocean waves. A long storm (one week) and several swell events were experienced and significant mine burial was observed in conjunction with high significant waveheights. Mine burial models suggest that burial at ldquoBertheaumerdquo was dominated by wave-induced scour rather than current-induced scour or momentary liquefaction. View full abstract»

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  • High-Resolution Mapping of Mines and Ripples at the Martha's Vineyard Coastal Observatory

    Page(s): 133 - 149
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4063 KB) |  | HTML iconHTML  

    High-resolution multibeam sonar and state-of-the-art data processing and visualization techniques have been used to quantify the evolution of seafloor morphology and the degree of burial of instrumented mines and mine-shapes as part of the U.S. Office of Naval Research (ONR, Arlington, VA) mine burial experiment at the Martha's Vineyard Coastal Observatory (MVCO, Edgartown, MA). Four surveys were conducted over two years at the experiment site with a 455-kHz, Reson 8125 dynamically focused multibeam sonar. The region is characterized by shore-perpendicular alternating zones of coarse-grained sand with 5-25-cm-high, wave orbital-scale ripples, and zones of finer grained sands with smaller (2-5-cm-high) anorbital ripples and, on occasion, medium scale 10-20-cm-high, chaotic or hummocky bedforms. The boundaries between the zones appear to respond over periods of days to months to the predominant wave direction and energy. Smoothing and small shifts of the boundaries to the northeast take place during fair-weather wave conditions while erosion (scalloping of the boundary) and shifts to the north-northwest occur during storm conditions. The multibeam sonar was also able to resolve changes in the orientation and height of fields of ripples that were directly related to the differences in the prevailing wave direction and energy. The alignment of the small scale bedforms with the prevailing wave conditions appears to occur rapidly (on the order of hours or days) when the wave conditions exceed the threshold of sediment motion (most of the time for the fine sands) and particularly during moderate storm conditions. During storm events, erosional ldquowindowsrdquo to the coarse layer below appear in the fine-grained sands. These ldquowindowrdquo features are oriented parallel to the prevailing wave direction and reveal orbital-scale ripples that are oriented perpendicular to the prevailing wave direction. The resolution of the multibeam sonar combined with 3-D visualization - techniques provided realistic looking images of both instrumented and noninstrumented mines and mine-like objects (including bomb, Manta, and Rockan shapes) that were dimensionally correct and enabled unambiguous identification of the mine type. In two of the surveys (October and December 2004), the mines in the fine-grained sands scoured into local pits but were still perfectly visible and identifiable with the multibeam sonar. In the April 2004 survey, the mines were not visible and apparently were completely buried. In the coarse-grained sand zone, the mines were extremely difficult to detect after initial scour burial as the mines bury until they present the same hydrodynamic roughness as the orbital-scale bedforms and thus blend into the ambient ripple field. Given the relatively large, 3-D, spatial coverage of the multibeam sonar along with its ability to measure the depth of the seafloor and the depth and dimensions of the mine, it is possible to measure directly, the burial by depth and burial by surface area of the mines. The 3-D nature of the multibeam sonar data also allows the direct determination of the volume of material removed from a scour pit. View full abstract»

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  • Mine Burial Experiments at the Martha's Vineyard Coastal Observatory

    Page(s): 150 - 166
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2069 KB) |  | HTML iconHTML  

    Several experiments to measure postimpact burial of seafloor mines by scour and fill have been conducted near the Woods Hole Oceanographic Institution's Martha's Vineyard Coastal Observatory (MVCO, Edgartown, MA). The sedimentary environment at MVCO consists of a series of rippled scour depressions (RSDs), which are large scale bedforms with alternating areas of coarse and fine sand. This allows simultaneous mine burial experiments in both coarse and fine sand under almost identical hydrodynamic forcing conditions. Two preliminary sets of mine scour burial experiments were conducted during winters 2001-2002 in fine sand and 2002-2003 in coarse sand with a single optically instrumented mine in the field of view of a rotary sidescan sonar. From October 2003 to April of 2004, ten instrumented mines were deployed along with several sonar systems to image mine behavior and to characterize bedform and oceanographic processes. In fine sand, the sonar imagery of the mines revealed that large scour pits form around the mines during energetic wave events. Mines fell into their own scour pits, aligned with the dominant wave crests and became level with the ambient seafloor after several energetic wave events. In quiescent periods, after the energetic wave events, the scour pits episodically infilled with mud. After several scour and infilling events, the scour pits were completely filled and a layer of fine sand covered both the mines and the scour pits, leaving no visible evidence of the mines. In the coarse sand, mines were observed to bury until the exposed height above the ripple crests was approximately the same as the large wave orbital ripple height (wavelengths of 50-125 cm and heights of 10-20 cm). A hypothesis for the physical mechanism responsible for this partial burial in the presence of large bedforms is that the mines bury until they present roughly the same hydrodynamic roughness as the orbital-scale bedforms present in coarse sand. View full abstract»

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  • Predicting Seabed Burial of Cylinders by Wave-Induced Scour: Application to the Sandy Inner Shelf Off Florida and Massachusetts

    Page(s): 167 - 183
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2997 KB) |  | HTML iconHTML  

    A simple parameterized model for wave-induced burial of mine-like cylinders as a function of grain-size, time-varying, wave orbital velocity and mine diameter was implemented and assessed against results from inert instrumented mines placed off the Indian Rocks Beach (IRB, FL), and off the Martha's vineyard coastal observatory (MVCO, Edgartown, MA). The steady flow scour parameters provided by Whitehouse (1998) for self-settling cylinders worked well for predicting burial by depth below the ambient seabed for (0.5 m) diameter mines in fine sand at both sites. By including or excluding scour pit infilling, a range of percent burial by surface area was predicted that was also consistent with observations. Rapid scour pit infilling was often seen at MVCO but never at IRB, suggesting that the environmental presence of fine sediment plays a key role in promoting infilling. Overprediction of mine scour in coarse sand was corrected by assuming a mine within a field of large ripples buries only until it generates no more turbulence than that produced by surrounding bedforms. The feasibility of using a regional wave model to predict mine burial in both hindcast and real-time forecast mode was tested using the National Oceanic and Atmospheric Administration (NOAA, Washington, DC) WaveWatch 3 (WW3) model. Hindcast waves were adequate for useful operational forcing of mine burial predictions, but five-day wave forecasts introduced large errors. This investigation was part of a larger effort to develop simple yet reliable predictions of mine burial suitable for addressing the operational needs of the U.S. Navy. View full abstract»

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  • Mine Burial Observations During the 2003–2004 U.S. Office of Naval Research Experiment

    Page(s): 184 - 190
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1559 KB) |  | HTML iconHTML  

    During the 2003-2004 winter season, the U.S. Office of Naval Research (ONR, Arlington, VA), sponsored a detailed in situ study of the mine burial process resulting from wave-seafloor-mine interaction at Martha's Vineyard Coastal Observatory (MVCO, Edgartown, MA). In total, 16 mine shapes were deployed. Six were the Forschungsanstalt der Bundeswehr fur Wasserschall und Geophysik (FWG, Kiel, Germany) burial registration mines using optical sensors, four others were equipped with acoustical sensors, and six were simple shapes. Repeated acoustic surveys and detailed sediment sampling were conducted to characterize the site and the burial status of all objects. This paper focuses on data from three recovered optical systems. The records show three roll events at all three registration mines, which are necessary for scour burial. Two systems experienced a fourth roll event. Results from earlier experiments suggest only three (four) stages of progressively increasing burial despite frequent successive burial and exposure cycles (some as short as 1 h). During these burial-exposure cycles changes of buried mine volume reached up to 80%. The only reasonable explanation is a change of sediment height of up to 40 cm relative to the stably lying mines. This requires new concepts. Cyclic burial changes that were observed simultaneously at different positions cannot be explained with existing models. The least difficult explanation is ldquounderwater sand stormsrdquo which are characterized by a high sediment suspension. View full abstract»

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  • Self-Burial of Short Cylinders Under Oscillatory Flows and Combined Waves Plus Currents

    Page(s): 191 - 203
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1451 KB) |  | HTML iconHTML  

    Self-burial processes of finite-length cylinders under oscillatory flows and waves plus currents were examined with the following two different experimental facilities: a large oscillating water-sediment tunnel (LOWST) and a large wave-current tank. More than 130 experiments, with different model cylinders, were conducted within both facilities. The burial mechanisms studied include burial due to local scour and bedform migration. Burial due to fluidization in the tunnel was also explored, but only in a qualitative way. In the case of experiments with LOWST, the equilibrium burial depth was found to be a power function of the shields parameter (thetas). In the wave-current tank, the equilibrium burial depth was also found to be a function of the Shields parameter, albeit with larger scatter. The experimental observations made in both facilities have similar trends but different magnitudes. For equivalent values of the Shields parameter, smaller equilibrium burial depths were observed in the wave flume when compared to the ones in LOWST. After burial induced by local scour takes place, bedform (ripples and sandwaves) formation and evolution play a strong and, in some cases, dominant role on the equilibrium burial depth of the cylinders. Depending on how the vertical dimensions of bedforms compare to the specimen's diameter, cyclical covering and uncovering of the object may take place due to the passage of the migrating sandwaves. In such case, burial depth Bd no longer coincides with the vertical displacement (Vd) of the object as in the case when the burial process is dominated by local scour. View full abstract»

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  • Mine Burial in the Shoaling Zone: Scaling of Laboratory Results to Oceanic Situations

    Page(s): 204 - 213
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (644 KB) |  | HTML iconHTML  

    During the past several years, the Environmental Fluid Dynamics Group at Arizona State University (ASU, Tempe, AZ) conducted a comprehensive laboratory-based research program to elucidate the mechanisms and dynamics of mine burial in noncohesive sediments under shoaling waves on coastal slopes. This paper presents a brief description of this program as well as salient observations and quantitative parameterizations for scour, ripples, and burial that resulted from it (which constitute the ASU mine burial model). Improvements to mine burial predictive capabilities offered by the ASU model are demonstrated by evaluating it vis-a-vis the (legacy) mine burial models that are in common use [Defense Research Agency mine burial environment (DRAMBUIE), Industrie Anlagen Bau Gesellschaft (NBURY, Munchen, Germany), and wave-induced spreadsheet prediction (WISSP)]. To this end, both the legacy and ASU models are discussed briefly and compared with field experimental data obtained during the 2003 Indian Rocks Beach (IRB, FL) experiment. The scour/burial data collected during the IRB campaign, using instrumented mines and diver observations, show that the predictions of the mostly laboratory-based ASU model agree satisfactorily with field observations, both qualitatively and quantitatively. View full abstract»

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  • Evolution of the Nearshore Bed Envelope

    Page(s): 214 - 224
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (635 KB) |  | HTML iconHTML  

    The temporal growth of the envelope of bed motion owing to the migration of bedforms, which can be considered a proxy for maximum object burial depth, is examined using five different data sets. These data sets support the hypothesis that the envelope of bed motion will grow as an exponential taper, quickly at first, tapering off and approaching an asymptotic value. This growth is largest and fastest in the surf zone where wave and current flows are strong. Within the surf zone, envelopes owing solely to the migration of megaripples (bedforms with heights from 20 to 40 cm and lengths from 1 to 5 m) grow for about 8 d and reach an asymptote of about 40 cm. When wave energy becomes larger ( 1 m), bed envelopes are dominated by migrating sand bars and approach an asymptote of 3-4 m, but only after 2-12 years (depending on the beach). In addition, the frequency of object burial (the percentage of time that an object would be buried by the crests of migrating bedforms) is highest in the surf zone and grows rapidly with time. View full abstract»

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  • A Comparison of Near-Bed Acoustic Backscatter and Laser Diffraction Measurements of Suspended Sediments

    Page(s): 225 - 235
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (708 KB) |  | HTML iconHTML  

    As part of the U.S. Office of Naval Research (ONR, Arlington, VA) mine burial program, an experiment was conducted off the pier at Santa Cruz, CA, to measure the near-bed suspended sediment reference concentration under waves and currents. Two tripods were deployed to carry out the measurements; one consisting mainly of acoustical instrumentation and the other solely of optical instruments. The tripods were located within 15 m of one another on a sandy bed and measurements of the suspended sediment were made using acoustics and optics. Although the experiment was not primarily designed to conduct an intercomparison of acoustical and optical measurements, it was considered interesting to take advantage of the situation and to examine if these two techniques gave comparable results. In particular, measurements of particle size and concentration, obtained using a triple frequency acoustic backscatter system (ABS) have been compared with the commercially available laser miniature scattering and transmissometry instrument (MSCAT). It was found that the mean grain size estimated by the two methods was consistent; however, in contrast, the concentration time series showed differences, both in magnitude and form. View full abstract»

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  • Progress on Nonlinear-Wave-Forced Sediment Transport Simulation

    Page(s): 236 - 248
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1683 KB) |  | HTML iconHTML  

    In this paper, we report on the use of a numerical wave tank (NWT), based on fully nonlinear potential flow (FNPF) equations, in driving simulations of flow and sediment transport around partially buried obstacles. The suspended sediment transport is modeled in the near-field in a Navier-Stokes (NS) model using an immersed-boundary method and an attached sediment transport simulation module. Turbulence is represented by large eddy simulation (LES). The NWT is based on a higher order boundary element method (BEM), with an explicit second-order time stepping. Hence, only the NWT boundary is discretized. The solution for the velocity potential and its derivatives along the boundary is obtained in the BEM, which subsequently provides a solution at any required internal point within the domain. At initial time, the NS-LES model domain is initialized with the 3-D velocity field provided by the NWT and driven for later time by the pressure gradient field obtained in the NWT. Incident wave fields, as specified in the NWT to drive sediment transport, can be arbitrary. Applications are presented here for single frequency waves, such as produced by a harmonic piston wavemaker in the laboratory, and modulated frequency wave groups. The feasibility of coupling the irrotational flow and NS solutions is demonstrated. View full abstract»

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  • Numerical Simulations of the Flow and Sediment Transport Regimes Surrounding a Short Cylinder

    Page(s): 249 - 259
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1445 KB) |  | HTML iconHTML  

    The 3-D flow field and bed stress surrounding a short cylinder in response to combined wave and mean-flow forcing events is examined. Model simulations are performed with a 3-D nonhydrostatic computational fluid dynamics model, FLOW-3D. The model is forced with a range of characteristic tidal and wave velocities as observed in 12-15 m of water at the Martha's Vineyard Coastal Observatory (MVCO, Edgartown, MA). The 2.4-m-long and 0.5-m diameter cylinder is buried 10% of the diameter on a flat, fixed bed. Regions of incipient motion are identified through local estimates of the Shields parameter exceeding the critical value. Potential areas of sediment deposition are identified with local estimates of the Rouse parameter exceeding ten. The model predictions of sediment response are in general in agreement with field observations of seabed morphology obtained over a one-week period during the 2003-2004 MVCO mine burial experiment. Both observations and simulations show potential transport occurring at the ends of the mine in wave-dominated events. Mean flows greater than 10 cm/s lead to the formation of larger scour pits upstream of the cylinder. Deposition in both cases tends to occur along the sides, near the center of mass of the mine. However, the fixed-bed assumption prohibits the prediction of full perimeter scour as is observed in nature. Predicted scour and burial regimes for a range of wave and mean-flow combinations are established. View full abstract»

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  • A Probabilistic Expert System Approach for Sea Mine Burial Prediction

    Page(s): 260 - 272
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    Knowledge of the extent of burial of bottom sitting sea mines is critical to mine detection due to the significantly degraded capabilities of mine-hunting systems when the mines are buried. To provide an enhanced capability for predicting mine burial in support of U.S. Navy mine countermeasure (MCM) operations, an expert system approach to predicting sea mine burial has been developed. This expert system serves as a means to synthesize previous and current research on sea mine burial due to impact upon deployment and subsequently due to scour, the two dominant burial mechanisms in littoral waters. Prediction systems for impact and scour burial have been implemented as simple Bayesian networks whose probabilistic basis provides means of accounting for the inherent uncertainties associated with mine deployment methods, simplified physics-based burial models, and environmental variability. Examples of burial predictions and comparisons to results from field experiments are illustrated. In addition, a proposed risk metric is developed and applied to provide a geospatial mapping of mine burial probability. View full abstract»

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Aims & Scope

The IEEE Journal of Oceanic Engineering (ISSN 0364-9059) is published quarterly by the IEEE Oceanic Engineering Society (IEEE OES). The scope of the Journal is the field of interest of the IEEE OES, which encompasses all aspects of science, engineering, and technology that address research, development, and operations pertaining to all bodies of water. This includes the creation of new capabilities and technologies from concept design through prototypes, testing, and operational systems to sense, explore, understand, develop, use, and responsibly manage natural resources.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
N. Ross Chapman
School of Earth & Ocean Sciences
University of Victoria
3800 Finnerty Road
Victoria, BC V8P 5C2 Canada
chapman@uvic.ca