An unstructured C-grid based method for 3-D global ocean dynamics: Free-surface formulations and tidal test cases

2009 ◽  
Vol 28 (1-3) ◽  
pp. 97-105 ◽  
Author(s):  
G.R. Stuhne ◽  
W.R. Peltier
Keyword(s):  
Free Surface ◽  
Ocean Dynamics ◽  
Global Ocean ◽  
Test Cases ◽  
Grid Based

Modeling Spray Formation in Gas Turbines: A New Meshless Approach

2012 ◽  
Author(s):  
C. Hoefler ◽  
S. Braun ◽  
R. Koch ◽  
H.-J. Bauer
Keyword(s):  
Surface Tension ◽  
Free Surface ◽  
Gas Turbines ◽  
Multiphase Flows ◽  
Free Surface Flows ◽  
Force Model ◽  
Pressure Jump ◽  
Test Cases ◽  
Spray Formation ◽  
Grid Based

A new meshless Lagrangian particle code has been developed in order to tackle the challenging numerical modeling of primary atomization. In doing so the correct treatment and representation of the interfacial physics are crucial prerequisites. Grid based codes using interface tracking or interface capturing techniques, such as the Volume of Fluid or Level Set method, exhibit some difficulties regarding mass conservation, curvature capturing and interface diffusion. The objective of this work is to overcome these shortcomings of common state-of-the-art grid based FVM approaches. Our multi-dimensional meshless particle code is based on the Smoothed Particle Hydrodynamics method [1] [2]. Various test cases have been conducted, by which the capability of accurately capturing the physics of single and multiphase flows is verified and the future potential of this approach is demonstrated. Compressible as well as incompresssible fluids can be modeled. Surface tension effects are taken into account by two different models, one of them being more suitable for free surface flows and the other for simulating multiphase flows. Solid walls as well as periodic boundary conditions offer a broad variety of numerically modeling technical applications. In a first step, single phase calculations of shear driven liquid flows have been carried out. Furthermore, the disintegration of a gravity driven liquid jet emerging from a generic nozzle has been investigated in free surface simulations. The typical formation of a meniscus due to surface tension is observed. Spray formation is qualitatively in good agreement compared to experiments. Surface tension effects have been taken into account via the cohesive force model. Finally, the results of a two-phase simulation with a fluid density ratio of 1000, which is similar to a fuel-air fluid system as in airblast atomizers, are presented. The surface minimization and pressure jump across the droplet interface due to surface tension can be predicted accurately. The test cases conducted so far demonstrate the accuracy of the existing code and underline the promising potential of this new method for successfully predicting primary atomization.

scholarly journals Global Well-Posedness of the Ocean Primitive Equations with Nonlinear Thermodynamics

2021 ◽  
Vol 23 (3) ◽  
Author(s):  
Peter Korn
Keyword(s):  
Equation Of State ◽  
Equations Of State ◽  
Boussinesq Equations ◽  
Climate Science ◽  
Rational Functions ◽  
Ocean Dynamics ◽  
Global Ocean ◽  
Primitive Equations ◽  
Well Posedness ◽  
Nonlinear Thermodynamics

AbstractWe consider the hydrostatic Boussinesq equations of global ocean dynamics, also known as the “primitive equations”, coupled to advection–diffusion equations for temperature and salt. The system of equations is closed by an equation of state that expresses density as a function of temperature, salinity and pressure. The equation of state TEOS-10, the official description of seawater and ice properties in marine science of the Intergovernmental Oceanographic Commission, is the most accurate equations of state with respect to ocean observation and rests on the firm theoretical foundation of the Gibbs formalism of thermodynamics. We study several specifications of the TEOS-10 equation of state that comply with the assumption underlying the primitive equations. These equations of state take the form of high-order polynomials or rational functions of temperature, salinity and pressure. The ocean primitive equations with a nonlinear equation of state describe richer dynamical phenomena than the system with a linear equation of state. We prove well-posedness for the ocean primitive equations with nonlinear thermodynamics in the Sobolev space $${{\mathcal {H}}^{1}}$$ H 1 . The proof rests upon the fundamental work of Cao and Titi (Ann. Math. 166:245–267, 2007) and also on the results of Kukavica and Ziane (Nonlinearity 20:2739–2753, 2007). Alternative and older nonlinear equations of state are also considered. Our results narrow the gap between the mathematical analysis of the ocean primitive equations and the equations underlying numerical ocean models used in ocean and climate science.

Sloshing in Rectangular and Cylindrical Tanks

2002 ◽  
Vol 46 (03) ◽  
pp. 186-200 ◽  
Author(s):  
Pierre C. Sames ◽  
Delphine Marcouly ◽  
Thomas E. Schellin
Keyword(s):  
Free Surface ◽  
Finite Volume ◽  
Temporal Evolution ◽  
Numerical Study ◽  
Computational Method ◽  
Test Cases ◽  
Grid Refinement ◽  
Cylindrical Tank ◽  
Excitation Period ◽  
Cylindrical Tanks

To validate an existing finite volume computational method, featuring a novel scheme to capture the temporal evolution of the free surface, fluid motions in partially filled tanks were simulated. The purpose was to compare computational and experimental results for test cases where measurements were available. Investigations comprised sloshing in a rectangular tank with a baffle at 60% filling level and in a cylindrical tank at 50% filling level. The numerical study started with examining effects of systematic grid refinement and concluded with examining effects of three-dimensionality and effects of variation of excitation period and amplitude. Predicted time traces of pressures and forces compared favorably with measurements.

scholarly journals Dake Chen: unraveling the secrets of ocean–climate interaction

2017 ◽  
Vol 4 (1) ◽  
pp. 136-139 ◽  
Author(s):  
Ling Wang
Keyword(s):  
Ocean Dynamics ◽  
Global Ocean ◽  
Practical Applications ◽  
Ocean Climate ◽  
Ocean Science ◽  
National Strategic Plan ◽  
Ocean Atmosphere Interaction ◽  
Atmosphere Interaction ◽  
Academy Of Sciences ◽  
Ocean Observing

Abstract The ocean is a complex and mysterious system that attracts scientists around the world to unravel its secrets. Dake Chen, a distinguished physical oceanographer and an academician of the Chinese Academy of Sciences, is one of them. Since the mid-1980s, he has been studying ocean dynamics and ocean–atmosphere interaction, and has made seminal contributions to the understanding and prediction of short-term climate variability, especially the El Niño phenomenon. In a recent interview with NSR, Professor Dake Chen says that China has made significant progress in recent years in ocean research, but, in order to make breakthroughs in the field of oceanography, China needs to further expand the scope of research programs from coastal seas to open oceans, to greatly increase the investment in global ocean-observing systems and to pay more attention to fundamental scientific problems in addition to practical applications. He also calls for a better-defined national strategic plan for ocean science and technology.

scholarly journals Multi-grid algorithm for passive tracer transport in the NEMO ocean circulation model: a case study with the NEMO OGCM (version 3.6)

2020 ◽  
Vol 13 (11) ◽  
pp. 5465-5483
Author(s):  
Clément Bricaud ◽  
Julien Le Sommer ◽  
Gurvan Madec ◽  
Christophe Calone ◽  
Julie Deshayes ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Ocean Circulation ◽  
Circulation Model ◽  
Ocean Model ◽  
Ocean Dynamics ◽  
Global Ocean ◽  
Passive Tracer ◽  
Tracer Transport ◽  
Ocean Circulation Model ◽  
Grid Algorithm

Abstract. Ocean biogeochemical models are key tools for both scientific and operational applications. Nevertheless the cost of these models is often expensive because of the large number of biogeochemical tracers. This has motivated the development of multi-grid approaches where ocean dynamics and tracer transport are computed on grids of different spatial resolution. However, existing multi-grid approaches to tracer transport in ocean modelling do not allow the computation of ocean dynamics and tracer transport simultaneously. This paper describes a new multi-grid approach developed for accelerating the computation of passive tracer transport in the Nucleus for European Modelling of the Ocean (NEMO) ocean circulation model. In practice, passive tracer transport is computed at runtime on a grid with coarser spatial resolution than the hydrodynamics, which reduces the CPU cost of computing the evolution of tracers. We describe the multi-grid algorithm, its practical implementation in the NEMO ocean model, and discuss its performance on the basis of a series of sensitivity experiments with global ocean model configurations. Our experiments confirm that the spatial resolution of hydrodynamical fields can be coarsened by a factor of 3 in both horizontal directions without significantly affecting the resolved passive tracer fields. Overall, the proposed algorithm yields a reduction by a factor of 7 of the overhead associated with running a full biogeochemical model like PISCES (with 24 passive tracers). Propositions for further reducing this cost without affecting the resolved solution are discussed.

scholarly journals Beaching patterns of plastic debris along the Indian Ocean rim

2020 ◽  
Author(s):  
Mirjam van der Mheen ◽  
Erik van Sebille ◽  
Charitha Pattiaratchi
Keyword(s):  
Indian Ocean ◽  
Bay Of Bengal ◽  
Plastic Material ◽  
Monsoon Season ◽  
Southwest Monsoon ◽  
Plastic Waste ◽  
Ocean Dynamics ◽  
Global Ocean ◽  
The Indian Ocean ◽  
Southwest Monsoon Season

Abstract. A large percentage of global ocean plastic waste enters the northern hemisphere Indian Ocean (NIO). Despite this, it is unclear what happens to buoyant plastics in the NIO. Because the subtropics in the NIO is blocked by landmass, there is no subtropical gyre and no associated subtropical garbage patch in this region. We therefore hypothesise that plastics "beach" and end up on coastlines along the Indian Ocean rim. In this paper, we determine the influence of beaching plastics by applying different beaching conditions to Lagrangian particle tracking simulation results. Our results show that a large amount of plastic likely ends up on coastlines in the NIO, while some crosses the equator into the southern hemisphere Indian Ocean (SIO). In the NIO, the transport of plastics is dominated by seasonally reversing monsoonal currents, which transport plastics back and forth between the Arabian Sea and the Bay of Bengal. All buoyant plastic material in this region beaches within a few years in our simulations. Countries bordering the Bay of Bengal are particularly heavily affected by plastics beaching on coastlines. This is a result of both the large sources of plastic waste in the region, as well as ocean dynamics which concentrate plastics in the Bay of Bengal. During the intermonsoon period following the southwest monsoon season (September, October, November), plastics can cross the equator on the eastern side of the NIO basin into the SIO. Plastics that escape from the NIO into the SIO beach on eastern African coastlines and islands in the SIO or enter the subtropical SIO garbage patch.

On the use of idealised test cases for ocean model development

2021 ◽  
Author(s):  
Julie Deshayes
Keyword(s):  
Boundary Conditions ◽  
General Circulation ◽  
Model Development ◽  
General Circulation Models ◽  
Ocean Model ◽  
Ocean Dynamics ◽  
Test Cases ◽  
Training Tool ◽  
Research Activities ◽  
Historical Progress

<p>When comparing realistic simulations produced by two ocean general circulation models, differences may emerge from alternative choices in boundary conditions and forcings, which alters our capacity to identify the actual differences between the two models (in the equations solved, the discretization schemes employed and/or the parameterizations introduced). The use of idealised test cases (idealized configurations with analytical boundary conditions and forcings, resolving a given set of equations) has proven efficient to reveal numerical bugs, determine advantages and pitfalls of certain numerical choices, and highlight remaining challenges. I propose to review historical progress enabled by the use of idealised test cases, and promote their utilization when assessing ocean dynamics as represented by an ocean model. For the latter, I would illustrate my talk using illustrations from my own research activities using NEMO in various contexts. I also see idealised test cases as a promising training tool for inexperienced ocean modellers, and an efficient solution to enlarge collaboration with experts in adjacent disciplines, such as mathematics, fluid dynamics and computer sciences.</p>

scholarly journals Significant Wave Height Estimation from Space-Borne Cyclone-GNSS Reflectometry

2019 ◽  
Vol 11 (5) ◽  
pp. 584 ◽  
Author(s):  
Qin Peng ◽  
Shuanggen Jin
Keyword(s):  
Standard Deviation ◽  
Correlation Coefficient ◽  
Wave Height ◽  
Significant Wave Height ◽  
Satellite System ◽  
Measurement Range ◽  
Ocean Dynamics ◽  
Global Ocean ◽  
Physical Parameters ◽  
Significant Wave

The significant wave height (SWH) of the sea is an important parameter and plays an important role in the prediction of waves and ocean dynamics. However, traditional methods, e.g., buoys or traditional remote sensing techniques such as X-band radar image have small measurement range and high cost. Recently, Global Navigation Satellite System-Reflectometry (GNSS-R) has provided a new opportunity to estimate the SWH, especially the space-borne Cyclone-GNSS (CYGNSS) launched on December 15, 2016. The GNSS-R uses the GNSS-reflected signal received by the receiver to invert ground physical parameters with all-weather, global fast coverage, high resolution, high precision, high long-term stability, rich signal sources, passive detection, and strong concealment. In this paper, the global ocean significant wave height is estimated using space-borne CYGNSS GNSS-R data for the first time though the relationship between the square root of the signal-to-noise ratio (SNR) data of CYGNSS delayed Doppler map (DDM) and the SWH. Then, the estimated significant wave height is compared with the satellite altimeter and buoy data. Compared with the AVISO SWH observation, the standard deviation value reaches 0.3080 m and the correlation coefficient reaches 0.9473 m. The correlation coefficient with the buoy SWH observation is 0.9539 m and the standard deviation is 0.2761 m. The SWH estimations from CYGNSS can provide important support in ocean shipping development, marine environmental protection, marine disaster warning and forecasting.

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