MEASURING ENERGY DISSIPATION RATES IN A WAVE TANK

2005 ◽  
Vol 2005 (1) ◽  
pp. 183-186 ◽  
Author(s):  
Albert D. Venosa ◽  
Vikram J. Kaku ◽  
Michel C. Boufadel ◽  
Kenneth Lee
Keyword(s):  
Energy Dissipation ◽  
Open Water ◽  
Breaking Waves ◽  
Pilot Scale ◽  
Energy Dissipation Rate ◽  
Breaking Wave ◽  
Field Scale ◽  
Wave Tank ◽  
Dissipation Rates ◽  
Wave Maker

ABSTRACT The effectiveness of dispersants is typically evaluated at various scales ranging from the smallest (10 cm, typical of flask tests in the laboratory) to the largest (10's to 100's of meters, typical of field scale open water dispersion tests). This study aims at evaluating dispersant effectiveness at intermediate or pilot scale. The hypothesis is that the energy dissipation rate per unit mass, ɛ, plays a major role in the effectiveness of a dispersant. Therefore, it is stipulated that in fairly general conditions, conservation of ɛ between the wave tank scale and that of the field scale is sufficient to accurately evaluate the effectiveness of a dispersant to disperse oil droplets. A wave tank measuring 16 m long x 0.6 m wide x 2 m deep was constructed on the premises of the Bedford Institute of Oceanography, Halifax, Nova Scotia. Waves were generated using a flap-type wave maker. Conditions of the breaking waves were created using a dispersive focusing technique in which the wave maker is started at high frequency and then the frequency decreased to create breaking waves. Experiments defining the velocity profile and energy dissipation rates in the wave tank were conducted at 2 different induced breaking-wave energies. Energy in the wave tank was measured with an Acoustic Doppler Velocimeter (ADV) coupled to a data acquisition system. Energy in the lab flasks was measured with a Hot Wire Anemometer.

scholarly journals Spectrally Resolved Energy Dissipation Rate and Momentum Flux of Breaking Waves

2008 ◽  
Vol 38 (6) ◽  
pp. 1296-1312 ◽  
Author(s):  
Johannes R. Gemmrich ◽  
Michael L. Banner ◽  
Chris Garrett
Keyword(s):  
Energy Dissipation ◽  
Wave Field ◽  
Wave Energy ◽  
Dissipation Rate ◽  
Momentum Flux ◽  
Phase Speed ◽  
Breaking Waves ◽  
Energy Dissipation Rate ◽  
Small Scale ◽  
Breaking Wave

Abstract Video observations of the ocean surface taken from aboard the Research Platform FLIP reveal the distribution of the along-crest length and propagation velocity of breaking wave crests that generate visible whitecaps. The key quantity assessed is Λ(c)dc, the average length of breaking crests per unit area propagating with speeds in the range (c, c + dc). Independent of the wave field development, Λ(c) is found to peak at intermediate wave scales and to drop off sharply at larger and smaller scales. In developing seas breakers occur at a wide range of scales corresponding to phase speeds from about 0.1 cp to cp, where cp is the phase speed of the waves at the spectral peak. However, in developed seas, breaking is hardly observed at scales corresponding to phase speeds greater than 0.5 cp. The phase speed of the most frequent breakers shifts from 0.4 cp to 0.2 cp as the wave field develops. The occurrence of breakers at a particular scale as well as the rate of surface turnover are well correlated with the wave saturation. The fourth and fifth moments of Λ(c) are used to estimate breaking-wave-supported momentum fluxes, energy dissipation rate, and the fraction of momentum flux supported by air-entraining breaking waves. No indication of a Kolmogorov-type wave energy cascade was found; that is, there is no evidence that the wave energy dissipation is dominated by small-scale waves. The proportionality factor b linking breaking crest distributions to the energy dissipation rate is found to be (7 ± 3) × 10−5, much smaller than previous estimates.

OIL DROPLET SIZE DISTRIBUTION AS A FUNCTION OF ENERGY DISSIPATION RATE IN AN EXPERIMENTAL WAVE TANK

2008 ◽  
Vol 2008 (1) ◽  
pp. 621-626 ◽  
Author(s):  
Zhengkai Li ◽  
Kenneth Lee ◽  
Thomas King ◽  
Michel C. Boufadel ◽  
Albert D. Venosa
Keyword(s):  
Energy Dissipation ◽  
Size Distribution ◽  
Dissipation Rate ◽  
Droplet Size Distribution ◽  
Breaking Waves ◽  
Energy Dissipation Rate ◽  
Wave Tank ◽  
Chemical Dispersant ◽  
Dispersed Oil ◽  
Dispersant Effectiveness

ABSTRACT The U.S. National Research Council (NRC) Committee on Understanding Oil Spill Dispersants: Efficacy and Effects (2005) identified two factors that require further investigation in chemical oil dispersant efficacy studies: 1) quantification of mixing energy at sea as energy dissipation rate and 2) dispersed particle size distribution. To fully evaluate the significance of these factors, a wave tank facility was designed and constructed to conduct controlled oil dispersion studies. A factorial experimental design was used to study the dispersant effectiveness as a function of energy dissipation rate for two oils and two dispersants under three different wave conditions, namely regular non-breaking waves, spilling breakers, and plunging breakers. The oils tested were weathered MESA and fresh ANS crude. The dispersants tested were Corexit 9500 and SPC 1000 plus water for no-dispersant control. The wave tank surface energy dissipatation rates of the three waves were determined to be 0.005, 0.1, and 1 m2/s3, respectively. The dispersed oil concentrations and droplet size distribution, measured by in-situ laser diffraction, were compared to quantify the chemical dispersant effectiveness as a function of energy dissipation rate. The results indicate that high energy dissipation rate of breaking waves enhanced chemical dispersant effectiveness by significantly increasing dispersed oil concentration and reducing droplet sizes in the water column (p <0.05). The presence of dispersants and breaking waves stimulated the oil dispersion kinetics. The findings of this research are expected to provide guidance to disperant application on oil spill responses.

DISPERSANT EFFECTIVENESS AS A FUNCTION OF ENERGY DISSIPATION RATE IN AN EXPERIMENTAL WAVE TANK

2008 ◽  
Vol 2008 (1) ◽  
pp. 777-783 ◽  
Author(s):  
A.D. Venosa ◽  
K. Lee ◽  
M. Boufadel ◽  
Z. Li ◽  
E. Wickley-Olsen ◽  
...  
Keyword(s):  
Particle Size ◽  
Energy Dissipation ◽  
Particle Size Distribution ◽  
Water Column ◽  
Size Distribution ◽  
Dissipation Rate ◽  
Breaking Waves ◽  
Energy Dissipation Rate ◽  
Wave Tank ◽  
Effective Dispersion

ABSTRACT In 2005, the National Research Council (NRC) published a comprehensive treatise on oil spill dispersants. Among other things, it concluded that research on dispersion effectiveness as a function of energy dissipation rate and particle size distribution was a high priority. Energy dissipation rate (turbulence and existence of breaking waves) is important to initiate and promote effective dispersion, and the particle size distribution of dispersed oil droplets affects dispersion and the ultimate fate of oil in the water column. In this paper, we discuss the use of a wave tank built on the premises of the Bedford Institute of Oceanography, Dartmouth, Nova Scotia, Canada as part of collaborative research begun in 2003 by the U.S. Environmental Protection Agency (EPA) and Fisheries and Oceans Canada (DFO). This tank is able to produce breaking waves of various energy levels at precise locations in the tank. We studied the effects of 2 commercial dispersants (Corexit 9500 and SPC 1000) and a no dispersant control on two different crude oils (unweathered Alaska North Slope and weathered MESA Light) at 3 different energy dissipation rates (regular non-breaking waves, spilling breakers, and plunging breakers), amounting to 18 different treatments. We quantified the energy dissipation rates under those 3 wave conditions and measured oil dispersion in a factorial experiment involving 3 replicates of the 18 treatments over the course of the summer of 2006. Results clearly showed the importance of wave energy and the presence of a chemical dispersant on the ability to produce effective dispersion of oil into the water column. The presence of dispersants at increasing wave energies produced significantly better dispersion (p <0.05) than the no-dispersant controls. This study was conducted under batch conditions. Future work will be done under continuous flow conditions.

REGULAR AND BREAKING WAVES IN WAVE TANK FOR DISPERSION EFFECTIVENESS TESTING

2008 ◽  
Vol 2008 (1) ◽  
pp. 499-508 ◽  
Author(s):  
Erik Wickley-Olsen ◽  
Michel C. Boufadel ◽  
Tom King ◽  
Zhengkai Li ◽  
Ken Lee ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Water Column ◽  
Water Waves ◽  
Dissipation Rate ◽  
Breaking Waves ◽  
Energy Dissipation Rate ◽  
Regular Waves ◽  
Wave Tank ◽  
Plunging Breaker ◽  
Water Profile

ABSTRACT The wave tank (32 m long × 2.0 m high × 0.6 m wide) at the Bedford Institute of Oceanography in Nova Scotia was used to simulate the propagation and breaking of deep water waves using a flap-type wavemaker. The water profile and velocity were measured using a wave gauge and an Acoustic Doppler Velocimeter (ADV). The wave periods of interest ranged between 1.18 and 2.08 seconds. A technique for generating breaking waves at the same location in the tank was used to obtain a spilling and a plunging breaker. We evaluated the energy dissipation rate at various depths in the tank for regular and breaking waves. Plunging breaking waves had heights of 0.25m. For the breaking experiments, the energy dissipation rate decreased from around 1.0 10−2 watts/kg a few centimeters below the surface to less than 5.0 10−4 watt/kg 20 cm deep in the water column. The regular waves had, on the average, an energy dissipation rate of 5.0 10−6 watt/kg deep in the water column. This indicates that breaking plays an important role in the dispersion of oil at sea.

Remote sensing of energy dissipation by individual oceanic whitecaps using above-water digital imagery

2021 ◽  
Author(s):  
Adrian Callaghan
Keyword(s):  
Remote Sensing ◽  
Energy Dissipation ◽  
Breaking Strength ◽  
Ocean Surface ◽  
Field Studies ◽  
Breaking Waves ◽  
Energy Dissipation Rate ◽  
Strength Parameter ◽  
Wave Crest ◽  
Breaking Wave

<p>Breaking waves are an important physical feature of the ocean surface and play a fundamental role in many air-sea interaction processes. Sufficiently energetic breaking waves can entrain enough air that they appear as whitecaps on the ocean surface and these are the focus of this work. Phillips (1985) presents a statistical description of the length of breaking wave crest per unit area within a breaking speed interval Λ(c), often referred to as the “lambda distribution”. Many field studies have measured Λ(c) using digital image remote sensing of the ocean surface, corroborating the theoretical work of Phillips. In conjunction with the so-called breaking strength parameter, b, defined by Duncan (1981), the fifth moment of Λ(c) has been used to quantify the energy dissipation rate of the surface breaking wave field. Within the Duncan framework, many numerical and experimental laboratory studies have shown that b is not constant but depends on the spectral and physical slope of the breaking waves, and it can vary by several orders of magnitude.</p><p>Significant effort has been made to estimate the average value of the breaking strength parameter for populations of breaking waves observed in the field, <b>. This can be achieved with measurements of Λ(c), an estimate of the wind to wave energy flux and assumptions of a stationary wave field. While several recent field studies have estimated <b> to be O(1 X 10<sup>-3</sup>), independent estimates of <b> derived from averaging values of b estimated for individual whitecaps in a given sea state have not yet been reported.</p><p>Here digital images of the sea surface are analysed and the volume-time-integral (VTI) method presented in Callaghan et al (2016) is used to estimate b on a whitecap-by-whitecap basis. The VTI method uses the time-evolving surface foam area of a whitecap together with a laboratory-determined average turbulence intensity inside a breaking wave crest, to estimate the total energy dissipated by an individual whitecap. This total energy loss can then be used to calculate the average energy dissipation rate of an individual whitecap, from which b can be estimated.</p><p>The dataset presented here consists of approximately 500 whitecaps and the range of b values estimated is distributed between 1 X 10<sup>-4</sup> to 1 X 10<sup>-2</sup>, with average values lying close to 1-2 X 10<sup>-3</sup>. This range of b values agrees well with laboratory results amassed over decades of experimental research. Furthermore, the average values of 1-2 X 10<sup>-3 </sup>agree very well with two recent <b> values reported in Zappa et al. (2016) and Korinenko et al. (2020). These results suggest that the VTI method can be a useful tool to remotely estimate the energy dissipation, and its rate, of individual whitecaps in the field using above-water digital image remote sensing.</p>

scholarly journals Observations of Breaking Waves and Energy Dissipation in Modulated Wave Groups

2018 ◽  
Vol 48 (12) ◽  
pp. 2937-2948 ◽  
Author(s):  
David W. Wang ◽  
Hemantha W. Wijesekera
Keyword(s):  
Energy Dissipation ◽  
Wave Height ◽  
Wave Breaking ◽  
Dissipation Rate ◽  
Breaking Waves ◽  
Wave Groups ◽  
Dissipation Rates ◽  
Local Wave ◽  
Tke Dissipation Rate ◽  
The Impact

AbstractIt has been recognized that modulated wave groups trigger wave breaking and generate energy dissipation events on the ocean surface. Quantitative examination of wave-breaking events and associated turbulent kinetic energy (TKE) dissipation rates within a modulated wave group in the open ocean is not a trivial task. To address this challenging topic, a set of laboratory experiments was carried out in an outdoor facility, the Oil and Hazardous Material Simulated Environment Test Tank (203 m long, 20 m wide, 3.5 m deep). TKE dissipation rates at multiple depths were estimated directly while moving the sensor platform at a speed of about 0.53 m s−1 toward incoming wave groups generated by the wave maker. The largest TKE dissipation rates and significant whitecaps were found at or near the center of wave groups where steepening waves approached the geometric limit of waves. The TKE dissipation rate was O(10−2) W kg−1 during wave breaking, which is two to three orders of magnitude larger than before and after wave breaking. The enhanced TKE dissipation rate was limited to a layer of half the wave height in depth. Observations indicate that the impact of wave breaking was not significant at depths deeper than one wave height from the surface. The TKE dissipation rate of breaking waves within wave groups can be parameterized by local wave phase speed with a proportionality breaking strength coefficient dependent on local steepness. The characterization of energy dissipation in wave groups from local wave properties will enable a better determination of near-surface TKE dissipation of breaking waves.

scholarly journals Estimating Energy Dissipation Rate from Breaking Waves Using Polarimetric SAR Images

Sensors ◽  
2020 ◽  
Vol 20 (22) ◽  
pp. 6540
Author(s):  
Rafael D. Viana ◽  
João A. Lorenzzetti ◽  
Jonas T. Carvalho ◽  
Ferdinando Nunziata
Keyword(s):  
Energy Dissipation ◽  
Total Energy ◽  
Dissipation Rate ◽  
Temporal Distribution ◽  
Wave Model ◽  
Breaking Waves ◽  
Fast Response ◽  
Energy Dissipation Rate ◽  
Sar Data ◽  
Total Energy Dissipation

The total energy dissipation rate on the ocean surface, ϵt (W m−2), provides a first-order estimation of the kinetic energy input rate at the ocean–atmosphere interface. Studies on the spatial and temporal distribution of the energy dissipation rate are important for the improvement of climate and wave models. Traditional oceanographic research normally uses remote measurements (airborne and platforms sensors) and in situ data acquisition to estimate ϵt; however, those methods cover small areas over time and are difficult to reproduce especially in the open oceans. Satellite remote sensing has proven the potential to estimate some parameters related to breaking waves on a synoptic scale, including the energy dissipation rate. In this paper, we use polarimetric Synthetic Aperture Radar (SAR) data to estimate ϵt under different wind and sea conditions. The used methodology consisted of decomposing the backscatter SAR return in terms of two contributions: a polarized contribution, associated with the fast response of the local wind (Bragg backscattering), and a non-polarized (NP) contribution, associated with wave breaking (Non-Bragg backscattering). Wind and wave parameters were estimated from the NP contribution and used to calculate ϵt from a parametric model dependent of these parameters. The results were analyzed using wave model outputs (WAVEWATCH III) and previous measurements documented in the literature. For the prevailing wind seas conditions, the ϵt estimated from pol-SAR data showed good agreement with dissipation associated with breaking waves when compared to numerical simulations. Under prevailing swell conditions, the total energy dissipation rate was higher than expected. The methodology adopted proved to be satisfactory to estimate the total energy dissipation rate for light to moderate wind conditions (winds below 10 m s−1), an environmental condition for which the current SAR polarimetric methods do not estimate ϵt properly.

Modelling Multiphase Jet Flows for High Velocity Emulsification

2011 ◽  
Author(s):  
David Ryan ◽  
Mark Simmons ◽  
Mike Baker
Keyword(s):  
Energy Dissipation ◽  
Turbulent Energy ◽  
Energy Dissipation Rate ◽  
Jet Flows ◽  
Nozzle Orifice ◽  
Multiphase Mixture ◽  
Dissipation Rates ◽  
Mass Flow Rates ◽  
Recirculation Zones ◽  
Drop Size Distributions

Single phase steady-state Computational Fluid Dynamics (CFD) simulations are presented for turbulent flow inside a Sonolator (an industrial static mixer). Methodology is given for obtaining high quality, converged, mesh-independent results. Pressures, velocities and local specific turbulent energy dissipation rates throughout the fluid domain are obtained for three industrially-relevant mass flow rates at a fixed nozzle orifice size. Discharge coefficients calculated at the orifice are compared to literature values and to pilot plant experiments for initial validation. Streamlines in the flow are used to illustrate the presence of recirculation zones after the nozzle. Thus, residence time and peak local specific turbulent energy dissipation rates are calculated from streamline data as a function of inlet position. Values of local specific turbulent energy dissipation rate obtained are used to infer drop sizes for emulsification of a multiphase mixture under dilute, homogeneous flow conditions. The results show that different drop size distributions may be produced depending on the inlet condition of the multiphase mixture.

scholarly journals The Influence of Whitecapping Waves on the Vertical Structure of Turbulence in a Shallow Estuarine Embayment

2008 ◽  
Vol 38 (7) ◽  
pp. 1563-1580 ◽  
Author(s):  
Nicole L. Jones ◽  
Stephen G. Monismith
Keyword(s):  
Energy Dissipation ◽  
Kinetic Energy ◽  
Water Column ◽  
Turbulent Kinetic Energy ◽  
San Francisco ◽  
Dissipation Rate ◽  
Energy Dissipation Rate ◽  
Wall Layer ◽  
Breaking Wave ◽  
Bottom Boundary Layers

Abstract The vertical distribution of the turbulent kinetic energy dissipation rate was measured using an array of four acoustic Doppler velocimeters in the shallow embayment of Grizzly Bay, San Francisco Bay, California. Owing to the combination of wind and tide forcing in this shallow system, the surface and bottom boundary layers overlapped. Whitecapping waves were generated for a significant spectral peak steepness greater than 0.05 or above a wind speed of 3 m s−1. Under conditions of whitecapping waves, the turbulent kinetic energy dissipation rate in the upper portion of the water column was greatly enhanced, relative to the predictions of wind stress wall-layer theory. Instead, the dissipation followed a modified deep-water breaking-wave scaling. Near the bed (bottom 10% of the water column), the dissipation measurements were either equal to or less than that predicted by wall-layer theory. Stratification due to concentration gradients in suspended sediment was identified as the likely cause for these periods of production–dissipation imbalance close to the bed. During 50% of the well-mixed conditions experienced in the month-long experiment, whitecapping waves provided the dominant source of turbulent kinetic energy over 90% or more of the water column.

Breaking Wave Impact on a Platform Column: An Introductory CFD Study

2011 ◽  
Author(s):  
Csaba Pakozdi ◽  
Timothy E. Kendon ◽  
Carl-Trygve Stansberg
Keyword(s):  
Model Test ◽  
Breaking Waves ◽  
Wave Profile ◽  
Scale Model ◽  
Computational Time ◽  
Breaking Wave ◽  
Wave Impact ◽  
Time Step ◽  
Test Setup ◽  
Wave Maker

The slamming of breaking waves on the legs of large volume offshore platforms has received increased attention over recent years. To investigate this problem, MARINTEK’s Wave Impact Loads JIP has, in one of its sub-tasks, focused towards an idealised model test setup of a rectangular cylinder in breaking waves. The model consists of a vertical column with a fragment of a horizontal deck attached. The model is fixed at a distance L ahead of the wave maker. Physical scale model test experiments of the block in regular waves and in wave groups have been carried out in Phase 1 of the JIP (2008). The objective of this study is the CFD simulation of a long crested breaking wave and its impact on the aforementioned cylinder and deck structure in order to find out the feasibility of the numerical reconstruction of such events. The commercial CFD tool Star-CCM+ V5.03.0056 (www.cd-adapco.com) is used in this study. This paper considers results from the test setup, and compares the measured wave elevation against results from the CFD code. The position of the cylinder in relation to the breaking wave front is investigated in the numerical simulation in order to analyze its effect on the slamming force. Use of an unsteady wave boundary condition, matching the exact motion history of the wave-maker with the measured free surface elevation at the wave maker gives an almost exact matching between the computed wave profile and the measured wave profile. The improvement in the numerical tool of Star-CCM+ which makes it possible to use higher order time integration scheme for VOF significantly decreases the numerical diffusion of the wave propagation. This new scheme also enables the use of a time step 10 times larger than the first order scheme which reduces the computational time. Because a large time step can be chosen it is important that the time step is small enough to capture the correct time evolution of the physical phenomena of interest. Capturing the pressure evolution at a slamming event demands very high spatial resolution. Spatially averaged slamming pressures look fairly similar to the model test observations, while further work is needed for a more detailed comparison.

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