Technical Update and Field Data from the New Generation Microwave Directional Wave Radar

1993 ◽  
pp. 3-17
Author(s):  
S. J. Archer
Keyword(s):  
Field Data ◽  
Wave Radar ◽  
Directional Wave ◽  
New Generation

Parameterization of Directional Spectra and Its Influence on Ship Motion Predictions

1993 ◽  
Vol 37 (02) ◽  
pp. 138-147
Author(s):  
Ross Graham ◽  
Barbara-Ann Juszko
Keyword(s):  
Spectral Data ◽  
Field Data ◽  
Ship Motion ◽  
Flight Operations ◽  
Modeling Accuracy ◽  
Directional Wave ◽  
Made In

An approach to parameterizing directional spectra proposed by Hogben & Cobb based on a combination of the Ochi & Hubble 6-parameter spectrum and the Longuet-Higgins et al cos2p model is adopted for a study of directional parameterizations and their influence on ship motion predictions. Two schemes for evaluating the directional spreading parameters are assessed in terms of their ability to reproduce highly resolved measured directional spectra, and the best approach, termed the 10-parameter spectrum, is adopted. The applicability of the 10-parameter spectrum to hindcast spectra is investigated, and acceptable fits obtained for 93% of the spectra considered. An evaluation of the ability of the hindcast model to reproduce the measured spectral data is also made. In general, it is found that the differences between the hindcast spectra and associated 10-parameter fits are significantly smaller than the differences between the hindcast spectra and the field data, and it is concluded that the 10-parameter spectrum is a suitable basis for developing statistical descriptions of directional wave climates. The effects of directional parameterization on ship motion predictions are investigated by computing the ship responses as a function of heading for sample hindcast spectra, and the associated 10-parameter and Bretschneider 2-parameter spectra. The responses calculated using the 10-parameter spectrum are found to be in better agreement with the hindcast results than those obtained with the Bretschneider 2-parameter spectrum, with a significant improvement in modeling accuracy in the case of bi-modal spectra. The potential advantages of incorporating the 10-parameter spectrum in future operability analyses of flight operations is examined by comparing the head-to-wind roll response computed using hindcast spectra with that predicted using 10-parameter and Bretschneider spectra.

scholarly journals STUDY OF GPM-IMERG RAINFALL DATA PRODUCT FOR GANGOTRI GLACIER

2018 ◽  
Vol XLII-5 ◽  
pp. 383-388
Author(s):  
P. Verma ◽  
S. K. Ghosh
Keyword(s):  
Field Data ◽  
Monsoon Season ◽  
Meteorological Data ◽  
Data Product ◽  
Precipitation Measurement ◽  
Post Monsoon Season ◽  
Gangotri Glacier ◽  
New Generation ◽  
Global Precipitation ◽  
Rainy Days

<p><strong>Abstract.</strong> This study presents a comparison of new generation weather observatory satellites Global Precipitation Measurement (GPM) Integrated Multi-satellite Retrievals for GPM (IMERG) rainfall products with field data collected for Gangotri glacier in India. The meteorological analysis of rainfall estimates has been performed on GPM IMERG Final, Late and Early precipitation products available at daily scale with a spatial resolution of 0.1&amp;deg;<span class="thinspace"></span>&amp;times;<span class="thinspace"></span>0.1&amp;deg; for melting season from May to September for the year 2014 and 2015 respectively. The comparison of satellite products with field data was done using correlation coefficient and standard anomaly. The Late run curve showed a high degree of similarity with final run curve while early run showed variation from them. The satellite meteorological data correctly identified non-rainy days with an average of &amp;sim;86.7%, &amp;sim;67.5% and &amp;sim;95% for pre-monsoon, monsoon and post-monsoon season respectively. The rmse for final run data product for 2014 and 2015 are 4.5, 1.23, 1.55, 1.24, 0.8 and 1.14, 7.1, 1.82, 1.15, 1.52 from May to September respectively. Overall, it has been observed that for medium to heavy rainfall final run estimates are close to field data and for light to medium rainfall late run estimates are close. Similar results have been obtained from both datasets for non-rainy days in the study area.</p>

A new, field-proven, cost-effective solution for MEG regeneration unit issues in offshore Australia gas production

2011 ◽  
Vol 51 (1) ◽  
pp. 193 ◽  
Author(s):  
Elizabeth Sanford ◽  
Rama Alapati
Keyword(s):  
Ethylene Glycol ◽  
Field Data ◽  
Cost Effective ◽  
Gas Production ◽  
Effective Solution ◽  
Regeneration Unit ◽  
High System ◽  
Gas Fields ◽  
New Generation ◽  
Low Dosage

Several gas fields are being developed off the coast of Western Australia. The risk for hydrate blockages in these fields is high and presents several challenges for hydrate inhibition, including high subcoolings, low water salinities, and high system temperatures. The current strategy is to use mono-ethylene glycol (MEG) for hydrate inhibition, which includes MEG regeneration units (MRUs) in the design of the facilities. The installation and maintenance of MRUs capable of handling the large required volumes of MEG is costly and other issues such as scale, foaming, and accumulation are a concern when using an MRU. Therefore, the use of a low dosage hydrate inhibitor (LDHI) is being considered for some developments. Kinetic hydrate inhibitors (KHIs) are typically considered for gas fields, not anti-agglomerate low dosage hydrate inhibitors (AA-LDHIs). KHIs, however, are not effective at high subcoolings and can become unstable when subjected to the high temperatures of the MRUs. Instead, a new generation of AA-LDHI chemistry can be considered for Australian gas fields. Field data will be presented supporting the new AA-LDHI’s effectiveness in inhibiting hydrate blockages in a gas/condensate field, eliminating the need for MEG and the MRU. The new AA-LDHI chemistry is being evaluated for several Australia projects, and data supporting the chemistry’s stability at temperatures greater than 150°C and its effectiveness with low-water salinities will also be presented. The new AA-LDHI chemistry could eliminate the need for MEG or greatly reduce the volume of MEG required for inhibition, which would reduce CAPEX and OPEX.

Real Time Local Sea State Measurement using Wave Radar and Ship Motions

2010 ◽  
Author(s):  
E. M. Thornhill ◽  
D. C. Stredulinsky
Keyword(s):  
Real Time ◽  
Wave Height ◽  
Ship Motions ◽  
Sea State ◽  
State Measurement ◽  
Wave Radar ◽  
Directional Wave ◽  
Radar Measurements ◽  
Real Time Information ◽  
Canadian Navy

The Canadian Navy is exploring operator guidance systems designed to promote safer and more efficient operations in a seaway. These systems require accurate real time information on the local sea state. Recent sea trials with a wave radar system, which can produce directional wave spectra from the back scatter produced by conventional navigational radar, have generated good direction and frequency measurements, but wave height was found to be less reliable. However, by combining the wave radar measurements with ship motions, these wave height measurements are greatly improved. This paper presents some background of at-sea wave measurement, a description of the combined wave radar / ship motions procedure, and the results from several sea trials.

scholarly journals VERIFICATION OF A MODIFIED BAYESIAN METHOD FOR ESTIMATING DIRECTIONAL WAVE SPECTRA FROM HF RADAR

2011 ◽  
Vol 1 (32) ◽  
pp. 65 ◽  
Author(s):  
Lukijanto Lukijanto ◽  
Noriaki Hashimoto ◽  
Masaru Yamashiro
Keyword(s):  
Field Data ◽  
Bayesian Method ◽  
Wave Spectrum ◽  
Coastal Engineering ◽  
Hf Radar ◽  
Ocean Wave ◽  
Wave Spectra ◽  
Directional Spectrum ◽  
Radio Science ◽  
Directional Wave

A Modified Bayesian Method (MBM) for estimating directional wave spectra from Doppler spectra obtained by HF radar is examined using field data which were employed in the verification of Bayesian Method (BM). Applicability, validity and accuracy of the MBM are demonstrated compared with the directional wave spectra estimated by BM and observed by buoy acquired from the reliable field data obtained from Surface Current and Wave Variability Experiments (SCAWVEX) project. The necessary conditions of the Doppler spectral components to be used to estimate a reliable directional spectrum are correspondingly estimated by BM. The results clearly demonstrate that directional wave spectra can be estimated by MBM on the basis of Doppler spectra. In addition, though BM shows very time consuming in computations, BM is more robust against the presence of noise than MBM. References Akaike, H. (1980). Likelihood and Bayesian procedure, Bayesian statistics. In J.M. Bernardo, M.H. De Groot, D.U. Lindley, and A.F.M. Smith (Eds.), 143-166. Valencia: University Press. PMid:6252024 Barrick, D. E. (1972a). First order theory and analysis of MF/HF/VHF scatter from sea. IEEE Trans., Antennas Propagation, 20, 2-10. http://dx.doi.org/10.1109/TAP.1972.1140123 Barrick, D. E. (1977). Extraction of wave parameters from measured HF radar sea-echo Doppler spectra. Radio Science, 12(3), 415–424. http://dx.doi.org/10.1029/RS012i003p00415 Crombie, D. (1955). Doppler spectrum of sea echo at 13.56Mc/s. Nature, 175, 681-682. http://dx.doi.org/10.1038/175681a0 Hashimoto, N. and Kobune, K. (1986). Estimation of directional spectra from the maximum entropy principle. Proceedings of 5th International Offshore Mechanics and Arctic Engineering Symposium, 1, 80-85. Hashimoto, N., Kobune, K., and Kameyama, Y. (1987). Estimation of directional spectrum using the Bayesian approach, and its application to field data analysis. Report of P.H.R.I., 26(5), 57-100. Hashimoto N., and Tokuda M., (1999): A Bayesian Method Approach for Estimation of Directional Wave Spectra with HF radar, Coastal Engineering Journal, vol. 41, 137-147. http://dx.doi.org/10.1142/S0578563499000097 Hashimoto, N., Wyatt, L and Kojima, S. (2003): Verification of Bayesian Method for Estimating Directional Spectra from HF Radar Surface. Coastal Engineering Journal, 45(2), 255-274. http://dx.doi.org/10.1142/S0578563403000725 Hashimoto, N., Lukijanto, and Yamashiro, M. (2008). Development of a practical method for estimating directional spectrum from HF radar backscatter. Annual Journal of Coastal Engineering (in Japanese), 55(1), 1451-1455. http://dx.doi.org/10.2208/proce1989.55.1451 Hisaki, Y. (1996). Nonlinear inversion of the integral equation to estimate ocean wave spectra from HF radar. Radio science, 31(1), 25-39. http://dx.doi.org/10.1029/95RS02439 Howell, R., and Walsh, J. (1993). Measurement of ocean wave spectra using a ship mounted HF radar. IEEE Journal of Oceanic Engineering, 18(3), 306-310. http://dx.doi.org/10.1109/JOE.1993.236369 Lipa, B. J. and Barrick, D.E. (1982) : Analysis Methods for Narrow-Beam High-Frequency Radar Sea Echo, NOAA Technical Report ERL 420-WPL 56, 1-55. Lukijanto, Hashimoto, N., and Yamashiro, M. (2009a). Further modification practical method for estimating directional wave spectrum by HF radar. Proc. of 19 th ISOPE, 898-905. Lukijanto, Hashimoto, N., and Yamashiro, M. (2009b). An improvement of Modified Bayesian Method for estimating directional wave spectra from HF radar backscatter. Proceedings of 5 th APAC (Asian and Pacific Coasts), 105-111. Lukijanto, Hashimoto, N., and Yamashiro, M. (2009c). A comparison of analysis methods for estimating directional wave spectrum from HF ocean radar. Journal of Memoirs of the Faculty of Engineering, 69(4). Kyushu University, 163-185. Wyatt, L.R. (1990). A relaxation method for integral inversion applied to HF radar measurement of the ocean wave directional spectrum. International Journal Remote Sensing, 11(8), 1481-1494. http://dx.doi.org/10.1080/01431169008955106 Wyatt, L. R. Gurgel, K.W., Peters, H.C., Prandle, D., Krogstad, H.E., Haug, O., Gerritsen, H., Wensink, G.J. (1997b). The SCAWVEX Project. Proceedings of WAVES97, ASCE.

Shipboard Measurement of Ocean Waves

2011 ◽  
Author(s):  
Thomas C. Fu ◽  
Anne M. Fullerton ◽  
Erin E. Hackett ◽  
Craig Merrill
Keyword(s):  
Field Tests ◽  
Ocean Waves ◽  
Naval Research ◽  
Wave Spectra ◽  
Individual Measurement ◽  
Office Of Naval Research ◽  
Wave Radar ◽  
New Instrumentation ◽  
Directional Wave ◽  
Commercial Off The Shelf

Over the past several years a number of techniques have been utilized for the measurement of ocean waves from shipboard platforms. These systems have ranged from commercial off the shelf (COTS) navigation radar and Light Detection and Ranging (LIDAR) systems to specially developed in-house instrumentation systems. Most of these systems have been utilized to measure the directional wave spectra around the ship. More recently, the Naval Surface Warfare Center, Carderock Division (NSWCCD) and others have begun to utilize these techniques for shipboard measurement of individual ship generated waves as well as open ocean waves. NSWCCD has used a number of these methods on various Office of Naval Research (ONR) and Naval Sea Systems (NAVSEA) sponsored field tests. These field tests were performed on a variety of naval platforms over a range of sizes, including some fixed platforms, for various sea states. While each of these tests has had individual measurement goals and objectives, the series of tests has also provided an environment for testing and developing new instrumentation and exploring their capabilities. As a result of these efforts, instrumentation has grown in sophistication from qualitative video-based observations of the wave field around an underway vessel to laser and radar based imaging and ranging measurements of free surface dynamics. This work has led to higher fidelity data, as well as data that were previously unobtainable. In this paper we provide an overview of these systems and techniques and summarize the basic capabilities of each method by providing measurement examples/applications. These systems include a shipboard array of ultrasonic distance sensors for measuring directional wave spectra, a COTS wave radar system, and a COTS scanning LIDAR system. While not intending to be exhaustive, this paper seeks to highlight the insights gained from the recent applications of these techniques, as well as the difficulties and issues associated with shipboard measurements such as ship motion and logistical constraints.

Topics in Development of Naval Architecture Software Applications

2013 ◽  
Author(s):  
Kevin McTaggart ◽  
David Heath ◽  
James Nickerson ◽  
Shawn Oakey ◽  
James Van Spengen
Keyword(s):  
Human Resources ◽  
Programming Languages ◽  
Ship Motion ◽  
Motion Prediction ◽  
Naval Architecture ◽  
Software Applications ◽  
Software Documentation ◽  
Wave Radar ◽  
Directional Wave ◽  
Replenishment At Sea

Software applications are used extensively in the practice of contemporary naval architecture. This paper describes several naval architecture applications, including ship motion prediction, simulation of replenishment at sea, simulation of launch and recovery, ship operator guidance, and measurement of directional wave spectra using wave radar. Within this context, this paper describes relevant technologies and programming languages that are effective for development of naval architecture software applications. Due to the complexity of naval architecture software, discussion is given on matching of human resources to software development tasks. Software documentation, which can take several forms, is addressed. Verification and validation of software is the final major topic.

Finding the Right Problems: Some HREM Applications to Interfaces

1984 ◽  
Vol 42 ◽  
pp. 376-379
Author(s):  
D. Cherns
Keyword(s):  
Grain Boundaries ◽  
High Resolution Electron Microscopy ◽  
Boundary Structure ◽  
Atomic Structures ◽  
Grain Boundary Structure ◽  
Resolution Electron ◽  
Point To Point ◽  
The Right ◽  
New Generation ◽  
Better Than

The use of high resolution electron microscopy (HREM) to determine the atomic structure of grain boundaries and interfaces is a topic of great current interest. Grain boundary structure has been considered for many years as central to an understanding of the mechanical and transport properties of materials. Some more recent attention has focussed on the atomic structures of metalsemiconductor interfaces which are believed to control electrical properties of contacts. The atomic structures of interfaces in semiconductor or metal multilayers is an area of growing interest for understanding the unusual electrical or mechanical properties which these new materials possess. However, although the point-to-point resolutions of currently available HREMs, ∼2-3Å, appear sufficient to solve many of these problems, few atomic models of grain boundaries and interfaces have been derived. Moreover, with a new generation of 300-400kV instruments promising resolutions in the 1.6-2.0 Å range, and resolutions better than 1.5Å expected from specialist instruments, it is an appropriate time to consider the usefulness of HREM for interface studies.

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