A Sea State–Dependent Spume Generation Function

2009 ◽  
Vol 39 (9) ◽  
pp. 2363-2372 ◽  
Author(s):  
James A. Mueller ◽  
Fabrice Veron
Keyword(s):  
Wind Forcing ◽  
Limited Data ◽  
Sea State ◽  
Generation Function ◽  
Scalar Fluxes ◽  
Droplet Distribution ◽  
State Dependent ◽  
Constant Form ◽  
New Generation ◽  
Good Agreement

Abstract The uncertainty of the sea spray generation function continues to obscure spray-mediated momentum and scalar fluxes, especially for intense wind conditions. Most previous studies assume a constant form (spectral shape) for the droplet distribution, even though a shift to smaller drops with increased wind forcing is expected. In this paper, a new generation function for spume drops is derived, but unlike previous studies, both its form and magnitude change with wind forcing. Fairly good agreement is found between this spume generation function and the limited data available. A potential explanation for the vast size differences among previous spume generation studies is also provided by distinguishing the drops formed at the surface from the drops transported vertically where measurements are routinely made.

scholarly journals Capability of Jason-2 Subwaveform Retrackers for Significant Wave Height in the Calm Semi-Enclosed Celebes Sea

2020 ◽  
Vol 12 (20) ◽  
pp. 3367
Author(s):  
Kaoru Ichikawa ◽  
Xi-Feng Wang ◽  
Hitoshi Tamura
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Leading Edge ◽  
Sea State ◽  
Significant Wave ◽  
Contamination Sources ◽  
The Pacific ◽  
Unique System ◽  
Calm Water ◽  
Good Agreement

Satellite altimetry is a unique system that provides repeated observations of significant wave height (SWH) globally, but its measurements could be contaminated by lands, slicks, or calm water with smooth surface. In this study, capability of subwaveform retrackers against 20 Hz Jason-2 measurements is examined in the calm Celebes Sea. Distances between contamination sources and Jason-2 observation points can be determined using sequentially assembled adjacent waveforms (radargram). When no contamination sources are present within a Jason-2 footprint, subwaveform retrackers are in excellent agreement with the Sensor Geophysical Data Records (SGDR) MLE4 retracker that uses full-length waveforms, except that Adaptive Leading Edge Subwaveform (ALES) retracker has a positive bias in a calm sea state (SWH < 1 m), which is not unusual in the Celebes Sea. Meanwhile, when contamination sources exist within 4.5 km from Jason-2 observation points, SGDR occasionally estimates unrealistically large SWH values, although they could be partly eliminated by sigma0 filters. These datasets are then compared with WAVEWATCH III model, resulting in good agreement. The agreement becomes worse if swells from the Pacific is excluded in the model, suggesting constant presence of swells despite the semi-enclosed nature. In addition, outliers are found related with locally-confined SWH events, which could be inadequately represented in the model.

Hydrodynamic Verification on the Motion Characteristics of FPSO Based on the Full Scale Measurement Data Features of Current and Wind

2010 ◽  
Author(s):  
Wenhua Zhao ◽  
Jianmin Yang ◽  
Zhiqiang Hu ◽  
Yuefeng Wei
Keyword(s):  
Time Domain ◽  
Measurement Data ◽  
Full Scale ◽  
Motion Prediction ◽  
Mooring System ◽  
Wind Force ◽  
Sea State ◽  
Hydrodynamic Analysis ◽  
Motion Characteristics ◽  
Good Agreement

FPSO is subjected to complex sea loads during its service life. Series of coupled hydrodynamic analysis in time domain for FPSO and its mooring system have been conducted within the recent ten years. Among these analyses, the coefficients of wind force and current force for FPSO hull were calculated by the empirical formulae mostly. It is known that these coefficients are of great importance in the motion predictions of the FPSO in the analysis. The verification of the feasibility of these formulae is necessary. In this paper, the feasibility and the accuracy of these empirical formulae are verified through the comparison between the results of hydrodynamic analysis and those of full scale measurement data. A full scale measurement project sponsored by CNOOC for Nanhai Fenjin, an FPSO operating in South China Sea, has been carrying out by Shanghai Jiao Tong University since Oct 2007. Large amount of valuable data of the six-degree motions for the FPSO has been obtained. To do the comparison, a typical serious sea state is selected out to be the objective course. In the course, the response spectrums for heave, roll and pitch motions are calculated based on the measurement data. Besides, a series of coupled hydrodynamic analysis for the FPSO are conducted, using the code DeepC. The response spectrums of the motions for heave, roll and pitch in the same sea state are also obtained through the spectrum analysis. Using these motion spectrums, comparisons between the results of hydrodynamic analysis and those of full scale measurement are fulfilled. With the comparisons, the feasibility of the empirical formulae of the coefficients for wind force and current force are verified. The correction coefficients are added to the empirical formulae and new hydrodynamic analysis based on the new formulae are conducted. It is shown that the new analysis results are in good agreement with those of the full scale measurement, which validated the practicability and feasibility of the modified formulae on the motion prediction of FPSO.

scholarly journals Unidirectional water pumping in zeta-potential modulated Nafion nanostructures

2021 ◽  
Author(s):  
Maria Jose Esplandiu ◽  
David Reguera ◽  
Daniel Romero-Guzmán ◽  
Amparo Maria Gallardo-Moreno ◽  
Jordi Fraxedas
Keyword(s):  
Electric Fields ◽  
Fluid Flows ◽  
Chemical Gradients ◽  
Zeta Potentials ◽  
Water Pumping ◽  
Wide Range ◽  
Micro Array ◽  
New Generation ◽  
Fine Tune ◽  
Good Agreement

Abstract We report on a new and versatile self-driven polymer micropump fueled by salt which can trigger both radial recirculating and unidirectional fluid flows. The micropump is based on the ion-exchanger Nafion, which produces chemical gradients with the consequent local generation of electric fields capable to trigger interfacial electro-osmotic flows. By combining new nanofabrication strategies for Nafion structuring in microarrays with a fine tune modulation of the surface zeta potentials it was possible to redirect electro-osmotic flows into unidirectional pumping. The experimental data have been contrasted with numerical simulations accomplishing good agreement. Nafion micropumps work in a wide range of salt concentrations covering more than four orders of magnitude, from micromolar to the millimolar range, and can be regenerated for reusability. This novel micro-array of chemically powered Nafion pumps constitutes a very appealing proof of concept for a new generation of wireless micro/nanofluidic networks.

scholarly journals Разработка технологических принципов создания системы микрофокусных рентгеновских трубок на основе кремниевых автоэмиссионных нанокатодов

2019 ◽  
Vol 89 (12) ◽  
pp. 1836
Author(s):  
Н.А. Дюжев ◽  
Г.Д. Демин ◽  
Н.А. Филиппов ◽  
И.Д. Евсиков ◽  
П.Ю. Глаголев ◽  
...  
Keyword(s):  
Field Emission ◽  
Emission Current ◽  
Field Emission Cathode ◽  
X Ray ◽  
Field Emission Current ◽  
Current Voltage ◽  
The Matrix ◽  
New Generation ◽  
Emission Cathode ◽  
Good Agreement

Abstract The technological prospects for the creation of a system of microfocus X-ray tubes with the use of silicon field emission of nanocathodes have been discussed. A numerical analysis of the field-emission current from a nanoscale semiconductor cathode regulated by voltage on a grid electrode has been carried out on the basis of which a scheme for controlling the elements of the matrix of field-emission cathode assemblies has been proposed. The current–voltage characteristics of silicon field emission nanocathodes have been measured. They are in good agreement with the theoretical estimates of the field-emission current. A full technological cycle of the development of elements of microfocus X-ray tubes (a set of field-emission cathode assemblies and a set of anode assemblies) has been performed. The results can be used to create systems of microfocus X-ray tubes for nanolithographic equipment of a new generation.

scholarly journals X-Band Radar for the Monitoring of Sea Waves and Currents: A Comparison between Medium and Short Radar Pulses

2017 ◽  
Author(s):  
Giovanni Ludeno ◽  
Francesco Raffa ◽  
Francesco Soldovieri ◽  
Francesco Serafino
Keyword(s):  
Surface Current ◽  
Parameters Estimation ◽  
Sea Waves ◽  
State Monitoring ◽  
Sea State ◽  
Experimental Campaign ◽  
X Band ◽  
Waves And Currents ◽  
Marine Radar ◽  
Good Agreement

Abstract. This letter presents the monitoring results of the sea waves and the surface currents obtained by analyzing data acquired by a X-band marine radar in two different operative conditions, namely the short and medium pulse modes. In particular, we investigated the feasibility to use a medium radar pulse for sea state monitoring by comparing the performance in both the radar modes. The comparison was carried out by means of an experimental campaign and we observed a good agreement for surface current and sea state parameters estimation.

scholarly journals The Copernicus Surface Velocity Platform drifter with Barometer and Reference Sensor for Temperature (SVP-BRST): Genesis, design, and initial results

2018 ◽  
Author(s):  
Paul Poli ◽  
Marc Lucas ◽  
Anne O'Carroll ◽  
Marc Le Menn ◽  
Arnaud David ◽  
...  
Keyword(s):  
Statistical Significance ◽  
Calibration Procedure ◽  
Immersion Depth ◽  
Surface Velocity ◽  
Small Scale ◽  
Pressure Probe ◽  
Sea State ◽  
Calm Water ◽  
Minute Interval ◽  
New Generation

Abstract. To support calibration and validation of satellite Sea-Surface Temperature (SST) retrievals, over 60 High Resolution SST (HRSST) drifting buoys were deployed at sea between 2012 and 2017. Their data record is reviewed here. It is confirmed that sea-state and immersion depth play an important role in understanding the data collected by such buoys and that the SST sensors need adequate insulation. In addition, calibration verification of three recovered drifters suggests that the sensor drift is low, albeit negative at around −0.01 K/year. However, the statistical significance of these results is limited, and the calibration procedure could not be exactly reproduced, introducing additional uncertainties into this drift assessment. Based on lessons learnt from these initial buoys, a new-generation drifter was designed to serve calibration of SST retrievals by European Union's Copernicus satellites. The novel drifter includes an HRSST sensor calibrated by a metrology laboratory. The sensor includes a pressure probe to monitor immersion depth in calm water, and acquires SST data at 1 Hz over a 5-minute interval every hour. This enables the derivation of mean SST as well as several percentiles of the SST distribution. The HRSST sensor is calibrated with an uncertainty better than 0.01 K. Analysis of the data collected by two prototypes deployed in the Mediterranean Sea shows that the buoys are able to capture small-scale SST variations. These variations are found to be smaller when the sea-state is well-mixed, and when the buoys are located within eddy cores. This affects the drifter SST data representativeness, which is an aspect of importance for optimal use of these data.

scholarly journals A NEW STRATEGIC WAVE MEASUREMENT STATION OFF NAPLES PORT MAIN BREAKWATER

2017 ◽  
pp. 36 ◽  
Author(s):  
Luca Centurioni ◽  
Lance Braasch ◽  
Enrico Di Lauro ◽  
Pasquale Contestabile ◽  
Francesco De Leo ◽  
...  
Keyword(s):  
Wave Energy ◽  
Low Cost ◽  
Acoustic Doppler Current Profiler ◽  
Wave Spectra ◽  
Sea State ◽  
Gulf Of Naples ◽  
Current Profiler ◽  
Directional Wave ◽  
Low Costs ◽  
Good Agreement

The accuracy of directional wave spectra sensors is crucial for obtaining accurate forecasts of ocean and coastal wave conditions for scientific and engineering applications. In this paper, a newly designed, low-cost GPS-based wave buoy, called the Directional Wave Spectra Drifter (DWSD), is presented. A field test campaign was conducted at the Gulf of Naples, Italy with the goal of comparing the directional wave properties obtained with the DWSD and with a nearly co-located bottom-mounted Acoustic Doppler Current Profiler (ADCP) from Teledyne RD-Instruments. The comparison shows a very good agreement between the two methodologies. The reliability of this innovative instrument and its low costs allow a large variety of applications, including the implementation of a global, satellite-linked, real-time open-ocean network of drifting directional wave spectra sensors and monitoring the sea-state in harbors to aid ship transit and for planning coastal and offshore constructions. The DWSD is currently in use to better constrain the wave energy climatology with the goal of optimizing the design of a full-scale prototype Wave Energy Converter (WEC) in the port of Naples, Italy.

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