Applied Turbulence Modelling in Marine Waters

Applied Turbulence Modelling in Marine Waters
Author: Hans Burchard
Publisher: Springer
Total Pages: 224
Release: 2007-08-15
Genre: Science
ISBN: 3540454195

The simulation of turbulent mixing processes in marine waters is one of the most pressing tasks in oceanography. It is rendered difficult by the various complex phenomena occurring in these waters like strong stratification, ex ternal and internal waves, wind generated turbulence, Langmuir circulation etc. The need for simulation methods is especially great in this area because the physical processes cannot be investigated in the laboratory. Tradition ally, empirical bulk type models were used in oceanography, which, however, cannot account for many of the complex physical phenomena occurring. In engineering, statistical turbulence models describing locally the turbulence mixing processes were introduced in the early seventies, such as the k E model which is still one of the most widely used models in Computational Fluid Dy namics. Soon after, turbulence models were applied more and more also in the atmospheric sciences, and here the k kL model of Mellor and Yamada became particularly popular. In oceanography, statistical turbulence mod els were introduced rather late, i. e. in the eighties, and mainly models were taken over from the fields mentioned above, with some adjustments to the problems occurring in marine waters. In the literature on turbulence model applications to oceanography problems controversial findings and claims are reported about the various models, creating also an uncertainty on how well the models work in marine water problems.

A Three Platform Experiment on Optical Turbulence in the Marine Boundary Layer

A Three Platform Experiment on Optical Turbulence in the Marine Boundary Layer
Author: Richard Henry Paine
Publisher:
Total Pages: 65
Release: 1977
Genre: Meteorology
ISBN:

An observational experiment was conducted in the marine boundary layer off the California coast involving optical turbulence measurements. The measurements were made from a ship, a tethered kite and two C-135 aircraft. Measured values of C(n) squared from the surface to levels above the marine inversion were related to the synoptic weather situation. C(n) squared values were observed to be maximum in the inversion. Near surface C(n) squared values, measured from two levels on the ship, exhibited expected diurnal changes. Overall, C(n) squared values measured optically (scintillation) and meteorologically (from C(T) squared measurements) compared satisfactorily. C(n) squared profiles estimated from surface observed values using a z to the -413 power assumed distribution appeared to define the mean measured profile.

Oceanic Whitecaps

Oceanic Whitecaps
Author: E.C. Monahan
Publisher: Springer Science & Business Media
Total Pages: 299
Release: 2012-12-06
Genre: Science
ISBN: 9400946686

Advanced Numerical Modeling and Data Assimilation Techniques for Tropical Cyclone Predictions

Advanced Numerical Modeling and Data Assimilation Techniques for Tropical Cyclone Predictions
Author: U.C. Mohanty
Publisher: Springer
Total Pages: 762
Release: 2016-11-21
Genre: Science
ISBN: 9402408967

This book deals primarily with monitoring, prediction and understanding of Tropical Cyclones (TCs). It was envisioned to serve as a teaching and reference resource at universities and academic institutions for researchers and post-graduate students. It has been designed to provide a broad outlook on recent advances in observations, assimilation and modeling of TCs with detailed and advanced information on genesis, intensification, movement and storm surge prediction. Specifically, it focuses on (i) state-of-the-art observations for advancing TC research, (ii) advances in numerical weather prediction for TCs, (iii) advanced assimilation and vortex initialization techniques, (iv) ocean coupling, (v) current capabilities to predict TCs, and (vi) advanced research in physical and dynamical processes in TCs. The chapters in the book are authored by leading international experts from academic, research and operational environments. The book is also expected to stimulate critical thinking for cyclone forecasters and researchers, managers, policy makers, and graduate and post-graduate students to carry out future research in the field of TCs.

A Machine-learning Model for Prediction of Optical Turbulence in Near-maritime Environments

A Machine-learning Model for Prediction of Optical Turbulence in Near-maritime Environments
Author: Christopher D. Jellen
Publisher:
Total Pages: 95
Release: 2020
Genre: Atmospheric turbulence
ISBN:

"As a beam propagates, it is subject to fluctuations in the refractive index of air. These effects can be modeled as optical turbulence. Optical turbulence limits the effectiveness of laser-based weapons and communication systems employed by the United States Navy. Models developed to predict optical turbulence through the structure constant Cn2 are sensitive to absolute air temperature. Existing models have, however, failed to accurately predict the rapid beam attenuation and corresponding high values of Cn2 observed in maritime and near-maritime environments. In response, data-driven machine learning models were developed to predict the refractive index structure parameter Cn2, and to explore the importance of various environmental factors on its prediction. The current study uses 15 months of Cn2 field measurements collected along an 890 m scintillometer link over the Severn River at the United States Naval Academy. Measures of optical turbulence are complemented by corresponding measurements of 12 environmental parameters. Fully data-driven models were trained, developed, and tested to enhance Cn2 prediction accuracy in the near-maritime environment. Analysis of these models resulted in better understanding of the relative importance of each environmental parameter in accurately predicting Cn2. To our knowledge, this is the first application of purely data-driven machine learning models for predicting Cn2 in the near-maritime environment." -- Report Documentation Page [Standard Form 298 (Rev. 8-98)].