Shallow water equations: viscous solutions and inviscid limit
Chen, Gui-Qiang; Perepelitsa, Mikhail
2012-12-01
We establish the inviscid limit of the viscous shallow water equations to the Saint-Venant system. For the viscous equations, the viscosity terms are more degenerate when the shallow water is close to the bottom, in comparison with the classical Navier-Stokes equations for barotropic gases; thus, the analysis in our earlier work for the classical Navier-Stokes equations does not apply directly, which require new estimates to deal with the additional degeneracy. We first introduce a notion of entropy solutions to the viscous shallow water equations and develop an approach to establish the global existence of such solutions and their uniform energy-type estimates with respect to the viscosity coefficient. These uniform estimates yield the existence of measure-valued solutions to the Saint-Venant system generated by the viscous solutions. Based on the uniform energy-type estimates and the features of the Saint-Venant system, we further establish that the entropy dissipation measures of the viscous solutions for weak entropy-entropy flux pairs, generated by compactly supported C 2 test-functions, are confined in a compact set in H -1, which yields that the measure-valued solutions are confined by the Tartar-Murat commutator relation. Then, the reduction theorem established in Chen and Perepelitsa [5] for the measure-valued solutions with unbounded support leads to the convergence of the viscous solutions to a finite-energy entropy solution of the Saint-Venant system with finite-energy initial data, which is relative with respect to the different end-states of the bottom topography of the shallow water at infinity. The analysis also applies to the inviscid limit problem for the Saint-Venant system in the presence of friction.
Conditionally invariant solutions of the rotating shallow water wave equations
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Huard, Benoit, E-mail: huard@dms.umontreal.c [Departement de mathematiques et de statistique, CP 6128, Succc. Centre-ville, Montreal, (QC) H3C 3J7 (Canada)
2010-06-11
This paper is devoted to the extension of the recently proposed conditional symmetry method to first-order nonhomogeneous quasilinear systems which are equivalent to homogeneous systems through a locally invertible point transformation. We perform a systematic analysis of the rank-1 and rank-2 solutions admitted by the shallow water wave equations in (2 + 1) dimensions and construct the corresponding solutions of the rotating shallow water wave equations. These solutions involve in general arbitrary functions depending on Riemann invariants, which allow us to construct new interesting classes of solutions.
Assessing Tsunami Vulnerabilities of Geographies with Shallow Water Equations
Aras, Rifat; Shen, Yuzhong
2012-01-01
Tsunami preparedness is crucial for saving human lives in case of disasters that involve massive water movement. In this work, we develop a framework for visual assessment of tsunami preparedness of geographies. Shallow water equations (also called Saint Venant equations) are a set of hyperbolic partial differential equations that are derived by depth-integrating the Navier-Stokes equations and provide a great abstraction of water masses that have lower depths compared to their free surface area. Our specific contribution in this study is to use Microsoft's XNA Game Studio to import underwater and shore line geographies, create different tsunami scenarios, and visualize the propagation of the waves and their impact on the shore line geography. Most importantly, we utilized the computational power of graphical processing units (GPUs) as HLSL based shader files and delegated all of the heavy computations to the GPU. Finally, we also conducted a validation study, in which we have tested our model against a controlled shallow water experiment. We believe that such a framework with an easy to use interface that is based on readily available software libraries, which are widely available and easily distributable, would encourage not only researchers, but also educators to showcase ideas.
Diffusive Wave Approximation to the Shallow Water Equations: Computational Approach
Collier, Nathan
2011-05-14
We discuss the use of time adaptivity applied to the one dimensional diffusive wave approximation to the shallow water equations. A simple and computationally economical error estimator is discussed which enables time-step size adaptivity. This robust adaptive time discretization corrects the initial time step size to achieve a user specified bound on the discretization error and allows time step size variations of several orders of magnitude. In particular, in the one dimensional results presented in this work feature a change of four orders of magnitudes for the time step over the entire simulation.
Symmetry reductions and exact solutions of Shallow water wave equations
Clarkson, P A
1994-01-01
In this paper we study symmetry reductions and exact solutions of the shallow water wave (SWW) equation u_{xxxt} + \\alpha u_x u_{xt} + \\beta u_t u_{xx} - u_{xt} - u_{xx} = 0,\\eqno(1) where \\alpha and \\beta are arbitrary, nonzero, constants, which is derivable using the so-called Boussinesq approximation. Two special cases of this equation, or the equivalent nonlocal equation obtained by setting u_x=U, have been discussed in the literature. The case \\alpha=2\\beta was discussed by Ablowitz, Kaup, Newell and Segur [{\\it Stud.\\ Appl.\\ Math.}, {\\bf53} (1974) 249], who showed that this case was solvable by inverse scattering through a second order linear problem. This case and the case \\alpha=\\beta were studied by Hirota and Satsuma [{\\it J.\\ Phys.\\ Soc.\\ Japan}, {\\bf40} (1976) 611] using Hirota's bi-linear technique. Further the case \\alpha=\\beta is solvable by inverse scattering through a third order linear problem. In this paper a catalogue of symmetry reductions is obtained using the classical Lie method and th...
Modeling rapid mass movements using the shallow water equations
Hergarten, S.; Robl, J.
2014-11-01
We propose a new method to model rapid mass movements on complex topography using the shallow water equations in Cartesian coordinates. These equations are the widely used standard approximation for the flow of water in rivers and shallow lakes, but the main prerequisite for their application - an almost horizontal fluid table - is in general not satisfied for avalanches and debris flows in steep terrain. Therefore, we have developed appropriate correction terms for large topographic gradients. In this study we present the mathematical formulation of these correction terms and their implementation in the open source flow solver GERRIS. This novel approach is evaluated by simulating avalanches on synthetic and finally natural topographies and the widely used Voellmy flow resistance law. The results are tested against analytical solutions and the commercial avalanche model RAMMS. The overall results are in excellent agreement with the reference system RAMMS, and the deviations between the different models are far below the uncertainties in the determination of the relevant fluid parameters and involved avalanche volumes in reality. As this code is freely available and open source, it can be easily extended by additional fluid models or source areas, making this model suitable for simulating several types of rapid mass movements. It therefore provides a valuable tool assisting regional scale natural hazard studies.
SHALLOW WATER EQUATION SOLUTION IN 2D USING FINITE DIFFERENCE METHOD WITH EXPLICIT SCHEME
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Nuraini Nuraini
2017-09-01
Full Text Available Abstract. Modeling the dynamics of seawater typically uses a shallow water model. The shallow water model is derived from the mass conservation equation and the momentum set into shallow water equations. A two-dimensional shallow water equation alongside the model that is integrated with depth is described in numerical form. This equation can be solved by finite different methods either explicitly or implicitly. In this modeling, the two dimensional shallow water equations are described in discrete form using explicit schemes. Keyword: shallow water equation, finite difference and schema explisit. REFERENSI 1. Bunya, S., Westerink, J. J. dan Yoshimura. 2005. Discontinuous Boundary Implementation for the Shallow Water Equations. Int. J. Numer. Meth. Fluids. 47: 1451-1468. 2. Kampf Jochen. 2009. Ocean Modelling For Beginners. Springer Heidelberg Dordrecht. London New York. 3. Rezolla, L 2011. Numerical Methods for the Solution of Partial Diferential Equations. Trieste. International Schoolfor Advanced Studies. 4. Natakussumah, K. D., Kusuma, S. B. M., Darmawan, H., Adityawan, B. M. Dan Farid, M. 2007. Pemodelan Hubungan Hujan dan Aliran Permukaan pada Suatu DAS dengan Metode Beda Hingga. ITB Sain dan Tek. 39: 97-123. 5. Casulli, V. dan Walters, A. R. 2000. An unstructured grid, three-dimensional model based on the shallow water equations. Int. J. Numer. Meth. Fluids. 32: 331-348. 6. Triatmodjo, B. 2002. Metode Numerik Beta Offset. Yogyakarta.
Balance-characteristic scheme as applied to the shallow water equations over a rough bottom
Goloviznin, V. M.; Isakov, V. A.
2017-07-01
The CABARET scheme is used for the numerical solution of the one-dimensional shallow water equations over a rough bottom. The scheme involves conservative and flux variables, whose values at a new time level are calculated by applying the characteristic properties of the shallow water equations. The scheme is verified using a series of test and model problems.
Geyer, Anna
2016-01-01
Following a general principle introduced by Ehrnstr\\"{o}m et.al. we prove that for an equation modeling the free surface evolution of moderate amplitude waves in shallow water, all symmetric waves are traveling waves.
Shiryaeva, E V
2014-01-01
In paper [S.I. Senashov, A. Yakhno. 2012. SIGMA. Vol.8. 071] the variant of the hodograph method based on the conservation laws for two hyperbolic quasilinear equations of the first order is described. Using these results we propose a method which allows to reduce the Cauchy problem for the two quasilinear PDE's to the Cauchy problem for ODE's. The proposed method is actually some similar method of characteristics for a system of two hyperbolic quasilinear equations. The method can be used effectively in all cases, when the linear hyperbolic equation in partial derivatives of the second order with variable coefficients, resulting from the application of the hodograph method, has an explicit expression for the Riemann-Green function. One of the method's features is the possibility to construct a multi-valued solutions. In this paper we present examples of method application for solving the classical shallow water equations.
Traveling wave solutions of a highly nonlinear shallow water equation
Geyer, A.; Quirchmayr, Ronald
2018-01-01
Motivated by the question whether higher-order nonlinear model equations, which go beyond the Camassa-Holm regime of moderate amplitude waves, could point us to new types of waves profiles, we study the traveling wave solutions of a quasilinear evolution equation which models the propagation of
Adaptive Finite Volume Method for the Shallow Water Equations on Triangular Grids
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Sudi Mungkasi
2016-01-01
Full Text Available This paper presents a numerical entropy production (NEP scheme for two-dimensional shallow water equations on unstructured triangular grids. We implement NEP as the error indicator for adaptive mesh refinement or coarsening in solving the shallow water equations using a finite volume method. Numerical simulations show that NEP is successful to be a refinement/coarsening indicator in the adaptive mesh finite volume method, as the method refines the mesh or grids around nonsmooth regions and coarsens them around smooth regions.
Marras, Simone; Suckale, Jenny; Giraldo, Francis X.; Constantinescu, Emil
2016-04-01
We present the solution of the viscous shallow water equations where viscosity is built as a residual-based subgrid scale model originally designed for large eddy simulation of compressible [1] and stratified flows [2]. The necessity of viscosity for a shallow water model not only finds motivation from mathematical analysis [3], but is supported by physical reasoning as can be seen by an analysis of the energetics of the solution. We simulated the flow of an idealized wave as it hits a set of obstacles. The kinetic energy spectrum of this flow shows that, although the inviscid Galerkin solutions -by spectral elements and discontinuous Galerkin [4]- preserve numerical stability in spite of the spurious oscillations in the proximity of the wave fronts, the slope of the energy cascade deviates from the theoretically expected values. We show that only a sufficiently small amount of dynamically adaptive viscosity removes the unwanted high-frequency modes while preserving the overall sharpness of the solution. In addition, it yields a physically plausible energy decay. This work is motivated by a larger interest in the application of a shallow water model to the solution of tsunami triggered coastal flows. In particular, coastal flows in regions around the world where coastal parks made of mitigation hills of different sizes and configurations are considered as a means to deviate the power of the incoming wave. References [1] M. Nazarov and J. Hoffman (2013) "Residual-based artificial viscosity for simulation of turbulent compressible flow using adaptive finite element methods" Int. J. Numer. Methods Fluids, 71:339-357 [2] S. Marras, M. Nazarov, F. X. Giraldo (2015) "Stabilized high-order Galerkin methods based on a parameter-free dynamic SGS model for LES" J. Comput. Phys. 301:77-101 [3] J. F. Gerbeau and B. Perthame (2001) "Derivation of the viscous Saint-Venant system for laminar shallow water; numerical validation" Discrete Contin. Dyn. Syst. Ser. B, 1:89?102 [4] F
Port-Hamiltonian formulation of shallow water equations with Coriolis force and topography
Ramkrishna Pasumarthy, R.P.; Ambati, V.R.; van der Schaft, Arjan
2008-01-01
We look into the problem of approximating the shallow water equations with Coriolis forces and topography. We model the system as an in��?nite-dimensional port-Hamiltonian system which is represented by a non-constant Stokes-Dirac structure. We here employ the idea of using diﬀerent ��?nite elements
Spatial discretization of the shallow water equations in spherical geometryusing Osher's scheme
D. Lanser; J.G. Blom (Joke); J.G. Verwer (Jan)
1999-01-01
textabstractThe shallow water equations in spherical geometry provide a first prototype for developing and testing numerical algorithms for atmospheric circulation models. Since the seventies these models are often solved with spectral methods. Increasing demands on grid resolution combined with
Optimization of ships in shallow water with viscous flow computations and surrogate modeling
Rotteveel, E.; van der Ploeg, A; Hekkenberg, R.G.; Nielsen, U.D.; Jensen et al, J.J.
2016-01-01
Shallow water effects change the flow around a ship significantly which can affect the optimum design of the hull. This paper describes a study into the optimization of the aft ship region for various water depths. The research focuses on variations of the following parameters of a hull form: The
Abramopoulos, Frank
1988-01-01
The conditions under which finite difference schemes for the shallow water equations can conserve both total energy and potential enstrophy are considered. A method of deriving such schemes using operator formalism is developed. Several such schemes are derived for the A-, B- and C-grids. The derived schemes include second-order schemes and pseudo-fourth-order schemes. The simplest B-grid pseudo-fourth-order schemes are presented.
Exploring a Multiresolution Modeling Approach within the Shallow-Water Equations
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Ringler, Todd D.; Jacobsen, Doug; Gunzburger, Max; Ju, Lili; Duda, Michael; Skamarock, William
2011-11-01
The ability to solve the global shallow-water equations with a conforming, variable-resolution mesh is evaluated using standard shallow-water test cases. While the long-term motivation for this study is the creation of a global climate modeling framework capable of resolving different spatial and temporal scales in different regions, the process begins with an analysis of the shallow-water system in order to better understand the strengths and weaknesses of the approach developed herein. The multiresolution meshes are spherical centroidal Voronoi tessellations where a single, user-supplied density function determines the region(s) of fine- and coarsemesh resolution. The shallow-water system is explored with a suite of meshes ranging from quasi-uniform resolution meshes, where the grid spacing is globally uniform, to highly variable resolution meshes, where the grid spacing varies by a factor of 16 between the fine and coarse regions. The potential vorticity is found to be conserved to within machine precision and the total available energy is conserved to within a time-truncation error. This result holds for the full suite of meshes, ranging from quasi-uniform resolution and highly variable resolution meshes. Based on shallow-water test cases 2 and 5, the primary conclusion of this study is that solution error is controlled primarily by the grid resolution in the coarsest part of the model domain. This conclusion is consistent with results obtained by others.When these variable-resolution meshes are used for the simulation of an unstable zonal jet, the core features of the growing instability are found to be largely unchanged as the variation in the mesh resolution increases. The main differences between the simulations occur outside the region of mesh refinement and these differences are attributed to the additional truncation error that accompanies increases in grid spacing. Overall, the results demonstrate support for this approach as a path toward
Clamond, Didier; Dutykh, Denys
2018-02-01
A new regularisation of the shallow water (and isentropic Euler) equations is proposed. The regularised equations are non-dissipative, non-dispersive and posses a variational structure; thus, the mass, the momentum and the energy are conserved. Hence, for instance, regularised hydraulic jumps are smooth and non-oscillatory. Another particularly interesting feature of this regularisation is that smoothed 'shocks' propagates at exactly the same speed as the original discontinuous ones. The performance of the new model is illustrated numerically on some dam-break test cases, which are classical in the hyperbolic realm.
Energy conserving and potential-enstrophy dissipating schemes for the shallow water equations
Arakawa, Akio; Hsu, Yueh-Jiuan G.
1990-01-01
To incorporate potential enstrophy dissipation into discrete shallow water equations with no or arbitrarily small energy dissipation, a family of finite-difference schemes have been derived with which potential enstrophy is guaranteed to decrease while energy is conserved (when the mass flux is nondivergent and time is continuous). Among this family of schemes, there is a member that minimizes the spurious impact of infinite potential vorticities associated with infinitesimal fluid depth. The scheme is, therefore, useful for problems in which the free surface may intersect with the lower boundary.
Time adaptivity in the diffusive wave approximation to the shallow water equations
Collier, Nathan
2013-05-01
We discuss the use of time adaptivity applied to the one dimensional diffusive wave approximation to the shallow water equations. A simple and computationally economical error estimator is discussed which enables time-step size adaptivity. This robust adaptive time discretization corrects the initial time step size to achieve a user specified bound on the discretization error and allows time step size variations of several orders of magnitude. In particular, the one dimensional results presented in this work feature a change of four orders of magnitudes for the time step over the entire simulation. © 2011 Elsevier B.V.
The shallow water equations on the sphere and their Lagrange- Galerkin-solution
Heinze, T
2002-01-01
The shallow water equations are formulated on the sphere in a three- dimensional coordinate system with the aid of tangential velocity components and differential operators. We introduce a modified semi- Lagrangian scheme for the discretization in time. The discretization in space is solved by linear finite elements. The grids we use are regular refinements of a macro triangulation which itself is derived from a highly symmetric polyeder also known as a bucky or soccer ball. The good numerical results show that this combination is a promising approach. The numerical algorithm is stable and its strength is the conservation of mass and energy. (16 refs).
A finite element method for solving the shallow water equations on the sphere
Comblen, Richard; Legrand, Sébastien; Deleersnijder, Eric; Legat, Vincent
Within the framework of ocean general circulation modeling, the present paper describes an efficient way to discretize partial differential equations on curved surfaces by means of the finite element method on triangular meshes. Our approach benefits from the inherent flexibility of the finite element method. The key idea consists in a dialog between a local coordinate system defined for each element in which integration takes place, and a nodal coordinate system in which all local contributions related to a vectorial degree of freedom are assembled. Since each element of the mesh and each degree of freedom are treated in the same way, the so-called pole singularity issue is fully circumvented. Applied to the shallow water equations expressed in primitive variables, this new approach has been validated against the standard test set defined by [Williamson, D.L., Drake, J.B., Hack, J.J., Jakob, R., Swarztrauber, P.N., 1992. A standard test set for numerical approximations to the shallow water equations in spherical geometry. Journal of Computational Physics 102, 211-224]. Optimal rates of convergence for the P1NC-P1 finite element pair are obtained, for both global and local quantities of interest. Finally, the approach can be extended to three-dimensional thin-layer flows in a straightforward manner.
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Williamson, D.L.; Hack, J.J.; Jakob, R.; Swarztrauber, P.N. (National Center for Atmospheric Research, Boulder, CO (United States)); Drake, J.B. (Oak Ridge National Lab., TN (United States))
1991-08-01
A suite of seven test cases is proposed for the evaluation of numerical methods intended for the solution of the shallow water equations in spherical geometry. The shallow water equations exhibit the major difficulties associated with the horizontal dynamical aspects of atmospheric modeling on the spherical earth. These cases are designed for use in the evaluation of numerical methods proposed for climate modeling and to identify the potential trade-offs which must always be made in numerical modeling. Before a proposed scheme is applied to a full baroclinic atmospheric model it must perform well on these problems in comparison with other currently accepted numerical methods. The cases are presented in order of complexity. They consist of advection across the poles, steady state geostrophically balanced flow of both global and local scales, forced nonlinear advection of an isolated low, zonal flow impinging on an isolated mountain, Rossby-Haurwitz waves and observed atmospheric states. One of the cases is also identified as a computer performance/algorithm efficiency benchmark for assessing the performance of algorithms adapted to massively parallel computers. 31 refs.
Directory of Open Access Journals (Sweden)
Ilhan Özgen
2017-10-01
Full Text Available In urban flood modeling, so-called porosity shallow water equations (PSWEs, which conceptually account for unresolved structures, e.g., buildings, are a promising approach to addressing high CPU times associated with state-of-the-art explicit numerical methods. The PSWE can be formulated with a single porosity term, referred to as the single porosity shallow water model (SP model, which accounts for both the reduced storage in the cell and the reduced conveyance, or with two porosity terms: one accounting for the reduced storage in the cell and another accounting for the reduced conveyance. The latter form is referred to as an integral or anisotropic porosity shallow water model (AP model. The aim of this study was to analyze the differences in wave propagation speeds of the SP model and the AP model and the implications of numerical model results. First, augmented Roe-type solutions were used to assess the influence of the source terms appearing in both models. It is shown that different source terms have different influences on the stability of the models. Second, four computational test cases were presented and the numerical models were compared. It is observed in the eigenvalue-based analysis as well as in the computational test cases that the models converge if the conveyance porosity in the AP model is close to the storage porosity. If the porosity values differ significantly, the AP model yields different wave propagation speeds and numerical fluxes from those of the BP model. In this study, the ratio between the conveyance and storage porosities was determined to be the most significant parameter.
Simulations and analysis of asteroid-generated tsunamis using the shallow water equations
Berger, M. J.; LeVeque, R. J.; Weiss, R.
2016-12-01
We discuss tsunami propagation for asteroid-generated air bursts and water impacts. We present simulations for a range of conditions using the GeoClaw simulation software. Examples include meteors that span 5 to 250 MT of kinetic energy, and use bathymetry from the U.S. coastline. We also study radially symmetric one-dimensional equations to better explore the nature and decay rate of waves generated by air burst pressure disturbances traveling at the speed of sound in air, which is much greater than the gravity wave speed of the tsunami generated. One-dimensional simulations along a transect of bathymetry are also used to explore the resolution needed for the full two-dimensional simulations, which are much more expensive even with the use of adaptive mesh refinement due to the short wave lengths of these tsunamis. For this same reason, shallow water equations may be inadequate and we also discuss dispersive effects.
A potential enstrophy and energy conserving scheme for the shallow water equations
Arakawa, A.; Lamb, V. R.
1981-01-01
To improve the simulation of nonlinear aspects of the flow over steep topography, a potential enstrophy and energy conserving scheme for the shallow water equations is derived. It is pointed out that a family of schemes can conserve total energy for general flow and potential enstrophy for flow with no mass flux divergence. The newly derived scheme is a unique member of this family, that conserves both potential enstrophy and energy for general flow. Comparison by means of numerical experiment with a scheme that conserves (potential) enstrophy for purely horizontal nondivergent flow demonstrated the considerable superiority of the newly derived potential enstrophy and energy conserving scheme, not only in suppressing a spurious energy cascade but also in determining the overall flow regime. The potential enstrophy and energy conserving scheme for a spherical grid is also presented.
Central-Upwind Schemes for Two-Layer Shallow Water Equations
Kurganov, Alexander
2009-01-01
We derive a second-order semidiscrete central-upwind scheme for one- and two-dimensional systems of two-layer shallow water equations. We prove that the presented scheme is well-balanced in the sense that stationary steady-state solutions are exactly preserved by the scheme and positivity preserving; that is, the depth of each fluid layer is guaranteed to be nonnegative. We also propose a new technique for the treatment of the nonconservative products describing the momentum exchange between the layers. The performance of the proposed method is illustrated on a number of numerical examples, in which we successfully capture (quasi) steady-state solutions and propagating interfaces. © 2009 Society for Industrial and Applied Mathematics.
George, David L.
2008-03-01
We present a class of augmented approximate Riemann solvers for the shallow water equations in the presence of a variable bottom surface. These belong to the class of simple approximate solvers that use a set of propagating jump discontinuities, or waves, to approximate the true Riemann solution. Typically, a simple solver for a system of m conservation laws uses m such discontinuities. We present a four wave solver for use with the the shallow water equations—a system of two equations in one dimension. The solver is based on a decomposition of an augmented solution vector—the depth, momentum as well as momentum flux and bottom surface. By decomposing these four variables into four waves the solver is endowed with several desirable properties simultaneously. This solver is well-balanced: it maintains a large class of steady states by the use of a properly defined steady state wave—a stationary jump discontinuity in the Riemann solution that acts as a source term. The form of this wave is introduced and described in detail. The solver also maintains depth non-negativity and extends naturally to Riemann problems with an initial dry state. These are important properties for applications with steady states and inundation, such as tsunami and flood modeling. Implementing the solver with LeVeque's wave propagation algorithm [R.J. LeVeque, Wave propagation algorithms for multi-dimensional hyperbolic systems, J. Comput. Phys. 131 (1997) 327-335] is also described. Several numerical simulations are shown, including a test problem for tsunami modeling.
Modelling rapid mass movements using the shallow water equations in Cartesian coordinates
Hergarten, S.; Robl, J.
2015-03-01
We propose a new method to model rapid mass movements on complex topography using the shallow water equations in Cartesian coordinates. These equations are the widely used standard approximation for the flow of water in rivers and shallow lakes, but the main prerequisite for their application - an almost horizontal fluid table - is in general not satisfied for avalanches and debris flows in steep terrain. Therefore, we have developed appropriate correction terms for large topographic gradients. In this study we present the mathematical formulation of these correction terms and their implementation in the open-source flow solver GERRIS. This novel approach is evaluated by simulating avalanches on synthetic and finally natural topographies and the widely used Voellmy flow resistance law. Testing the results against analytical solutions and the proprietary avalanche model RAMMS, we found a very good agreement. As the GERRIS flow solver is freely available and open source, it can be easily extended by additional fluid models or source areas, making this model suitable for simulating several types of rapid mass movements. It therefore provides a valuable tool for assisting regional-scale natural hazard studies.
Large gyres as a shallow-water asymptotic solution of Euler's equation in spherical coordinates.
Constantin, A; Johnson, R S
2017-04-01
Starting from the Euler equation expressed in a rotating frame in spherical coordinates, coupled with the equation of mass conservation and the appropriate boundary conditions, a thin-layer (i.e. shallow water) asymptotic approximation is developed. The analysis is driven by a single, overarching assumption based on the smallness of one parameter: the ratio of the average depth of the oceans to the radius of the Earth. Consistent with this, the magnitude of the vertical velocity component through the layer is necessarily much smaller than the horizontal components along the layer. A choice of the size of this speed ratio is made, which corresponds, roughly, to the observational data for gyres; thus the problem is characterized by, and reduced to an analysis based on, a single small parameter. The nonlinear leading-order problem retains all the rotational contributions of the moving frame, describing motion in a thin spherical shell. There are many solutions of this system, corresponding to different vorticities, all described by a novel vorticity equation: this couples the vorticity generated by the spin of the Earth with the underlying vorticity due to the movement of the oceans. Some explicit solutions are obtained, which exhibit gyre-like flows of any size; indeed, the technique developed here allows for many different choices of the flow field and of any suitable free-surface profile. We comment briefly on the next order problem, which provides the structure through the layer. Some observations about the new vorticity equation are given, and a brief indication of how these results can be extended is offered.
Dehghan, Mehdi; Abbaszadeh, Mostafa
2017-12-01
The main aim of this paper is to develop a fast and efficient local meshless method for solving shallow water equations in one- and two-dimensional cases. The mentioned equation has been classified in category of advection equations. The solutions of advection equations have some shock, thus, especial numerical methods should be employed for example discontinuous Galerkin and finite volume methods. Here, based on the proper orthogonal decomposition approach we want to construct a fast meshless method. To this end, we consider shallow water models and obtain a suitable time-discrete scheme based on the predictor-corrector technique. Then by applying the proper orthogonal decomposition technique a new set of basis functions can be built for the solution space in which the size of new solution space is less than the original problem. Thus, by employing the new bases the CPU time will be reduced. Some examples have been studied to show the efficiency of the present numerical technique.
Hernandez-Walls, R.; Martín-Atienza, B.; Salinas-Matus, M.; Castillo, J.
2017-11-01
When solving the linear inviscid shallow water equations with variable depth in one dimension using finite differences, a tridiagonal system of equations must be solved. Here we present an approach, which is more efficient than the commonly used numerical method, to solve this tridiagonal system of equations using a recursion formula. We illustrate this approach with an example in which we solve for a rectangular channel to find the resonance modes. Our numerical solution agrees very well with the analytical solution. This new method is easy to use and understand by undergraduate students, so it can be implemented in undergraduate courses such as Numerical Methods, Lineal Algebra or Differential Equations.
Karczewska, Anna; Rozmej, Piotr; Infeld, Eryk
2015-11-01
It is well known that the Korteweg-de Vries (KdV) equation has an infinite set of conserved quantities. The first three are often considered to represent mass, momentum, and energy. Here we try to answer the question of how this comes about and also how these KdV quantities relate to those of the Euler shallow-water equations. Here Luke's Lagrangian is helpful. We also consider higher-order extensions of KdV. Though in general not integrable, in some sense they are almost so within the accuracy of the expansion.
Directory of Open Access Journals (Sweden)
Pengfei Zhao
2014-01-01
Full Text Available We consider the shallow water equations (SWE in spherical coordinates solved by Turkel-Zwas (T-Z explicit large time-step scheme. To reduce the dimension of the SWE model, we use a well-known model order reduction method, a proper orthogonal decomposition (POD. As the computational complexity still depends on the number of variables of the full spherical SWE model, we use discrete empirical interpolation method (DEIM proposed by Sorensen to reduce the computational complexity of the reduced-order model. DEIM is very helpful in evaluating quadratically nonlinear terms in the reduced-order model. The numerical results show that POD-DEIM is computationally very efficient for implementing model order reduction for spherical SWE.
Arakawa, A.; Lamb, V. R.
1979-01-01
A three-dimensional finite difference scheme for the solution of the shallow water momentum equations which accounts for the conservation of potential enstrophy in the flow of a homogeneous incompressible shallow atmosphere over steep topography as well as for total energy conservation is presented. The scheme is derived to be consistent with a reasonable scheme for potential vorticity advection in a long-term integration for a general flow with divergent mass flux. Numerical comparisons of the characteristics of the present potential enstrophy-conserving scheme with those of a scheme that conserves potential enstrophy only for purely horizontal nondivergent flow are presented which demonstrate the reduction of computational noise in the wind field with the enstrophy-conserving scheme and its convergence even in relatively coarse grids.
Schlesinger, R. E.; Johnson, D. R.; Uccellini, L. W.
1983-01-01
In the present investigation, a one-dimensional linearized analysis is used to determine the effect of Asselin's (1972) time filter on both the computational stability and phase error of numerical solutions for the shallow water wave equations, in cases with diffusion but without rotation. An attempt has been made to establish the approximate optimal values of the filtering parameter nu for each of the 'lagged', Dufort-Frankel, and Crank-Nicholson diffusion schemes, suppressing the computational wave mode without materially altering the physical wave mode. It is determined that in the presence of diffusion, the optimum filter length depends on whether waves are undergoing significant propagation. When moderate propagation is present, with or without diffusion, the Asselin filter has little effect on the spatial phase lag of the physical mode for the leapfrog advection scheme of the three diffusion schemes considered.
A comparative study of diffraction of shallow-water waves by high-level IGN and GN equations
Energy Technology Data Exchange (ETDEWEB)
Zhao, B.B. [College of Shipbuilding Engineering, Harbin Engineering University, 150001 Harbin (China); Ertekin, R.C. [Department of Ocean and Resources Engineering, University of Hawai' i, Honolulu, HI 96822 (United States); College of Shipbuilding Engineering, Harbin Engineering University, 150001 Harbin (China); Duan, W.Y., E-mail: duanwenyangheu@hotmail.com [College of Shipbuilding Engineering, Harbin Engineering University, 150001 Harbin (China)
2015-02-15
This work is on the nonlinear diffraction analysis of shallow-water waves, impinging on submerged obstacles, by two related theories, namely the classical Green–Naghdi (GN) equations and the Irrotational Green–Naghdi (IGN) equations, both sets of equations being at high levels and derived for incompressible and inviscid flows. Recently, the high-level Green–Naghdi equations have been applied to some wave transformation problems. The high-level IGN equations have also been used in the last decade to study certain wave propagation problems. However, past works on these theories used different numerical methods to solve these nonlinear and unsteady sets of differential equations and at different levels. Moreover, different physical problems have been solved in the past. Therefore, it has not been possible to understand the differences produced by these two sets of theories and their range of applicability so far. We are thus motivated to make a direct comparison of the results produced by these theories by use of the same numerical method to solve physically the same wave diffraction problems. We focus on comparing these two theories by using similar codes; only the equations used are different but other parts of the codes, such as the wave-maker, damping zone, discretion method, matrix solver, etc., are exactly the same. This way, we eliminate many potential sources of differences that could be produced by the solution of different equations. The physical problems include the presence of various submerged obstacles that can be used for example as breakwaters or to represent the continental shelf. A numerical wave tank is created by placing a wavemaker on one end and a wave absorbing beach on the other. The nonlinear and unsteady sets of differential equations are solved by the finite-difference method. The results are compared with different equations as well as with the available experimental data.
Shallow Water Waves and Solitary Waves
Hereman, Willy
2013-01-01
Encyclopedic article covering shallow water wave models used in oceanography and atmospheric science. Sections: Definition of the Subject; Introduction and Historical Perspective; Completely Integrable Shallow Water Wave Equations; Shallow Water Wave Equations of Geophysical Fluid Dynamics; Computation of Solitary Wave Solutions; Numerical Methods; Water Wave Experiments and Observations; Future Directions, and Bibliography.
The Principle of Energetic Consistency: Application to the Shallow-Water Equations
Cohn, Stephen E.
2009-01-01
If the complete state of the earth's atmosphere (e.g., pressure, temperature, winds and humidity, everywhere throughout the atmosphere) were known at any particular initial time, then solving the equations that govern the dynamical behavior of the atmosphere would give the complete state at all subsequent times. Part of the difficulty of weather prediction is that the governing equations can only be solved approximately, which is what weather prediction models do. But weather forecasts would still be far from perfect even if the equations could be solved exactly, because the atmospheric state is not and cannot be known completely at any initial forecast time. Rather, the initial state for a weather forecast can only be estimated from incomplete observations taken near the initial time, through a process known as data assimilation. Weather prediction models carry out their computations on a grid of points covering the earth's atmosphere. The formulation of these models is guided by a mathematical convergence theory which guarantees that, given the exact initial state, the model solution approaches the exact solution of the governing equations as the computational grid is made more fine. For the data assimilation process, however, there does not yet exist a convergence theory. This book chapter represents an effort to begin establishing a convergence theory for data assimilation methods. The main result, which is called the principle of energetic consistency, provides a necessary condition that a convergent method must satisfy. Current methods violate this principle, as shown in earlier work of the author, and therefore are not convergent. The principle is illustrated by showing how to apply it as a simple test of convergence for proposed methods.
Large gyres as a shallow-water asymptotic solution of Euler’s equation in spherical coordinates
Johnson, R. S.
2017-01-01
Starting from the Euler equation expressed in a rotating frame in spherical coordinates, coupled with the equation of mass conservation and the appropriate boundary conditions, a thin-layer (i.e. shallow water) asymptotic approximation is developed. The analysis is driven by a single, overarching assumption based on the smallness of one parameter: the ratio of the average depth of the oceans to the radius of the Earth. Consistent with this, the magnitude of the vertical velocity component through the layer is necessarily much smaller than the horizontal components along the layer. A choice of the size of this speed ratio is made, which corresponds, roughly, to the observational data for gyres; thus the problem is characterized by, and reduced to an analysis based on, a single small parameter. The nonlinear leading-order problem retains all the rotational contributions of the moving frame, describing motion in a thin spherical shell. There are many solutions of this system, corresponding to different vorticities, all described by a novel vorticity equation: this couples the vorticity generated by the spin of the Earth with the underlying vorticity due to the movement of the oceans. Some explicit solutions are obtained, which exhibit gyre-like flows of any size; indeed, the technique developed here allows for many different choices of the flow field and of any suitable free-surface profile. We comment briefly on the next order problem, which provides the structure through the layer. Some observations about the new vorticity equation are given, and a brief indication of how these results can be extended is offered. PMID:28484341
Bauer, Werner; Behrens, Jörn
2017-04-01
We present a locally conservative, low-order finite element (FE) discretization of the covariant 1D linear shallow-water equations written in split form (cf. tet{[1]}). The introduction of additional differential forms (DF) that build pairs with the original ones permits a splitting of these equations into topological momentum and continuity equations and metric-dependent closure equations that apply the Hodge-star. Our novel discretization framework conserves this geometrical structure, in particular it provides for all DFs proper FE spaces such that the differential operators (here gradient and divergence) hold in strong form. The discrete topological equations simply follow by trivial projections onto piecewise constant FE spaces without need to partially integrate. The discrete Hodge-stars operators, representing the discretized metric equations, are realized by nontrivial Galerkin projections (GP). Here they follow by projections onto either a piecewise constant (GP0) or a piecewise linear (GP1) space. Our framework thus provides essentially three different schemes with significantly different behavior. The split scheme using twice GP1 is unstable and shares the same discrete dispersion relation and similar second-order convergence rates as the conventional P1-P1 FE scheme that approximates both velocity and height variables by piecewise linear spaces. The split scheme that applies both GP1 and GP0 is stable and shares the dispersion relation of the conventional P1-P0 FE scheme that approximates the velocity by a piecewise linear and the height by a piecewise constant space with corresponding second- and first-order convergence rates. Exhibiting for both velocity and height fields second-order convergence rates, we might consider the split GP1-GP0 scheme though as stable versions of the conventional P1-P1 FE scheme. For the split scheme applying twice GP0, we are not aware of a corresponding conventional formulation to compare with. Though exhibiting larger
Attractor for a Viscous Coupled Camassa-Holm Equation
Directory of Open Access Journals (Sweden)
Tian Lixin
2010-01-01
Full Text Available The global existence of solution to a viscous coupled Camassa-Holm equation with the periodic boundary condition is investigated. We obtain the compact and bounded absorbing set and the existence of the global attractor for the viscous coupled Camassa-Holm equation in by uniform prior estimate.
Navas-Montilla, A.; Murillo, J.
2017-07-01
When designing a numerical scheme for the resolution of conservation laws, the selection of a particular source term discretization (STD) may seem irrelevant whenever it ensures convergence with mesh refinement, but it has a decisive impact on the solution. In the framework of the Shallow Water Equations (SWE), well-balanced STD based on quiescent equilibrium are unable to converge to physically based solutions, which can be constructed considering energy arguments. Energy based discretizations can be designed assuming dissipation or conservation, but in any case, the STD procedure required should not be merely based on ad hoc approximations. The STD proposed in this work is derived from the Generalized Hugoniot Locus obtained from the Generalized Rankine Hugoniot conditions and the Integral Curve across the contact wave associated to the bed step. In any case, the STD must allow energy-dissipative solutions: steady and unsteady hydraulic jumps, for which some numerical anomalies have been documented in the literature. These anomalies are the incorrect positioning of steady jumps and the presence of a spurious spike of discharge inside the cell containing the jump. The former issue can be addressed by proposing a modification of the energy-conservative STD that ensures a correct dissipation rate across the hydraulic jump, whereas the latter is of greater complexity and cannot be fixed by simply choosing a suitable STD, as there are more variables involved. The problem concerning the spike of discharge is a well-known problem in the scientific community, also known as slowly-moving shock anomaly, it is produced by a nonlinearity of the Hugoniot locus connecting the states at both sides of the jump. However, it seems that this issue is more a feature than a problem when considering steady solutions of the SWE containing hydraulic jumps. The presence of the spurious spike in the discharge has been taken for granted and has become a feature of the solution. Even though
Wintermeyer, Niklas; Winters, Andrew R.; Gassner, Gregor J.; Kopriva, David A.
2017-07-01
We design an arbitrary high-order accurate nodal discontinuous Galerkin spectral element approximation for the non-linear two dimensional shallow water equations with non-constant, possibly discontinuous, bathymetry on unstructured, possibly curved, quadrilateral meshes. The scheme is derived from an equivalent flux differencing formulation of the split form of the equations. We prove that this discretization exactly preserves the local mass and momentum. Furthermore, combined with a special numerical interface flux function, the method exactly preserves the mathematical entropy, which is the total energy for the shallow water equations. By adding a specific form of interface dissipation to the baseline entropy conserving scheme we create a provably entropy stable scheme. That is, the numerical scheme discretely satisfies the second law of thermodynamics. Finally, with a particular discretization of the bathymetry source term we prove that the numerical approximation is well-balanced. We provide numerical examples that verify the theoretical findings and furthermore provide an application of the scheme for a partial break of a curved dam test problem.
Zia, H.; Simpson, G.
2013-12-01
The interaction between flowing surface water and sediment transport has numerous important applications in Earth science, including controls on river patterns, drainage basin evolution and morphological changes induced by extreme events such as tsunamis and dam breaks. Many of these problems can be investigated with the mathematical model of the shallow water equations coupled to conservation of sediment concentration and empirical functions for bed friction, substrate erosion and deposition. However, this system of equations is highly nonlinear, requiring fast and robust numerical methods. In this study, we investigate the solution of the shallow water equations coupled to sediment transports via the Non-oscillatory Central Differencing (NOC ) method, a second order scheme based on a predictor-corrector method. The scheme is chosen for its relative stability and robustness. The NOC scheme is especially favorable in situations where the water depth approaches zero and for steady flow conditions, both of which cause problems with more naive schemes. The model is verified by comparing computed results with documented solutions. We are currently using the model to investigate coupling between flow and sediment transport in alluvial rivers.
Pelinovsky, Efim; Chaikovskaia, Natalya; Rodin, Artem
2015-04-01
The paper presents the analysis of the formation and evolution of shock wave in shallow water with no restrictions on its amplitude in the framework of the nonlinear shallow water equations. It is shown that in the case of large-amplitude waves appears a new nonlinear effect of reflection from the shock front of incident wave. These results are important for the assessment of coastal flooding by tsunami waves and storm surges. Very often the largest number of victims was observed on the coastline where the wave moved breaking. Many people, instead of running away, were just looking at the movement of the "raging wall" and lost time. This fact highlights the importance of researching the problem of security and optimal behavior of people in situations with increased risk. Usually there is uncertainty about the exact time, when rogue waves will impact. This fact limits the ability of people to adjust their behavior psychologically to the stressful situations. It concerns specialists, who are busy both in the field of flying activity and marine service as well as adults, young people and children, who live on the coastal zone. The rogue wave research is very important and it demands cooperation of different scientists - mathematicians and physicists, as well as sociologists and psychologists, because the final goal of efforts of all scientists is minimization of the harm, brought by rogue waves to humanity.
Hof, Bas van ’t; Veldman, Arthur E.P.
2012-01-01
The paper explains a method by which discretizations of the continuity and momentum equations can be designed, such that they can be combined with an equation of state into a discrete energy equation. The resulting 'MaMEC' discretizations conserve mass, momentum as well as energy, although no
Null controllability of the viscous Camassa–Holm equation with ...
Indian Academy of Sciences (India)
In this paper, we study the null controllability of the viscous Camassa–Holm equation on the one-dimensional torus. By using a moving distributed control, we obtain that the system is null controllable for a given data with certain regularity. Author Affiliations. Peng Gao1. School of Mathematics and Statistics, and Center for ...
Null controllability of the viscous Camassa–Holm equation with ...
Indian Academy of Sciences (India)
Indian Acad. Sci. (Math. Sci.) Vol. 126, No. 1, February 2016, pp. 99–108. c Indian Academy of Sciences. Null controllability of the viscous Camassa–Holm equation with moving control. PENG GAO. School of Mathematics and Statistics, and Center for Mathematics and. Interdisciplinary Sciences, Northeast Normal University ...
Viscous Regularization of the Euler Equations and Entropy Principles
Guermond, Jean-Luc
2014-03-11
This paper investigates a general class of viscous regularizations of the compressible Euler equations. A unique regularization is identified that is compatible with all the generalized entropies, à la [Harten et al., SIAM J. Numer. Anal., 35 (1998), pp. 2117-2127], and satisfies the minimum entropy principle. A connection with a recently proposed phenomenological model by [H. Brenner, Phys. A, 370 (2006), pp. 190-224] is made. © 2014 Society for Industrial and Applied Mathematics.
Ersoy, Mehmet; Lakkis, Omar; Townsend, Philip
2016-04-01
The flow of water in rivers and oceans can, under general assumptions, be efficiently modelled using Saint-Venant's shallow water system of equations (SWE). SWE is a hyperbolic system of conservation laws (HSCL) which can be derived from a starting point of incompressible Navier-Stokes. A common difficulty in the numerical simulation of HSCLs is the conservation of physical entropy. Work by Audusse, Bristeau, Perthame (2000) and Perthame, Simeoni (2001), proposed numerical SWE solvers known as kinetic schemes (KSs), which can be shown to have desirable entropy-consistent properties, and are thus called well-balanced schemes. A KS is derived from kinetic equations that can be integrated into the SWE. In flood risk assessment models the SWE must be coupled with other equations describing interacting meteorological and hydrogeological phenomena such as rain and groundwater flows. The SWE must therefore be appropriately modified to accommodate source and sink terms, so kinetic schemes are no longer valid. While modifications of SWE in this direction have been recently proposed, e.g., Delestre (2010), we depart from the extant literature by proposing a novel model that is "entropy-consistent" and naturally extends the SWE by respecting its kinetic formulation connections. This allows us to derive a system of partial differential equations modelling flow of a one-dimensional river with both a precipitation term and a groundwater flow model to account for potential infiltration and recharge. We exhibit numerical simulations of the corresponding kinetic schemes. These simulations can be applied to both real world flood prediction and the tackling of wider issues on how climate and societal change are affecting flood risk.
Anuga Software for Numerical Simulations of Shallow Water Flows
Mungkasi, Sudi; Roberts, Stephen Gwyn
2012-01-01
Shallow water flows are governed by the shallow water wave equations, also known as the Saint-Venant system. This paper presents a finite volume method used to solve the two-dimensional shallow water wave equations and how the finite volume method is implemented in ANUGA software. This finite volume method is the numerical method underlying the software. ANUGA is open source software developed by Australian National University (ANU) and Geoscience Australia (GA). This software uses the finite...
ANUGA SOFTWARE FOR NUMERICAL SIMULATIONS OF SHALLOW WATER FLOWS
Sudi Mungkasi; Stephen Gwyn Roberts
2012-01-01
Shallow water flows are governed by the shallow water wave equations, also known as the Saint-Venant system. This paper presents a finite volume method used to solve the two-dimensional shallow water wave equations and how the finite volume method is implemented in ANUGA software. This finite volume method is the numerical method underlying the software. ANUGA is open source software developed by Australian National University (ANU) and Geoscience Australia (GA). This software uses the finite...
Approximate factorization in shallow water applications
P.J. van der Houwen; B.P. Sommeijer (Ben)
1998-01-01
textabstractWe consider the numerical integration of problems modelling phenomena in shallow water in 3 spatial dimensions. If the governing partial differential equations for such problems are spatially discretized, then the righthand side of the resulting system of ordinary differential equations
Shallow water cnoidal wave interactions
Directory of Open Access Journals (Sweden)
A. R. Osborne
1994-01-01
Full Text Available The nonlinear dynamics of cnoidal waves, within the context of the general N-cnoidal wave solutions of the periodic Korteweg-de Vries (KdV and Kadomtsev-Petvishvilli (KP equations, are considered. These equations are important for describing the propagation of small-but-finite amplitude waves in shallow water; the solutions to KdV are unidirectional while those of KP are directionally spread. Herein solutions are constructed from the 0-function representation of their appropriate inverse scattering transform formulations. To this end a general theorem is employed in the construction process: All solutions to the KdV and KP equations can be written as the linear superposition of cnoidal waves plus their nonlinear interactions. The approach presented here is viewed as significant because it allows the exact construction of N degree-of-freedom cnoidal wave trains under rather general conditions.
On the viscous Burgers equation in unbounded domain
Directory of Open Access Journals (Sweden)
J. Limaco
2010-04-01
Full Text Available In this paper we investigate the existence and uniqueness of global solutions, and a rate stability for the energy related with a Cauchy problem to the viscous Burgers equation in unbounded domain $\\mathbb{R}\\times(0,\\infty$. Some aspects associated with a Cauchy problem are presented in order to employ the approximations of Faedo-Galerkin in whole real line $\\mathbb{R}$. This becomes possible due to the introduction of weight Sobolev spaces which allow us to use arguments of compactness in the Sobolev spaces.
Mostafa M.A. Khater; Dipankar Kumar
2017-01-01
The aim of the article is to construct exact solutions for the time fractional coupled Boussinesq–Burger and approximate long water wave equations by using the generalized Kudryashov method. The fractional differential equation is converted into ordinary differential equations with the help of fractional complex transform and the modified Riemann–Liouville derivative sense. Applying the generalized Kudryashov method through with symbolic computer maple package, numerous new exact solutions ar...
Directory of Open Access Journals (Sweden)
Mostafa M.A. Khater
2017-09-01
Full Text Available The aim of the article is to construct exact solutions for the time fractional coupled Boussinesq–Burger and approximate long water wave equations by using the generalized Kudryashov method. The fractional differential equation is converted into ordinary differential equations with the help of fractional complex transform and the modified Riemann–Liouville derivative sense. Applying the generalized Kudryashov method through with symbolic computer maple package, numerous new exact solutions are successfully obtained. All calculations in this study have been established and verified back with the aid of the Maple package program. The executed method is powerful, effective and straightforward for solving nonlinear partial differential equations to obtain more and new solutions with the integer and fractional order.
Global existence of solutions for a viscous Cahn–Hilliard equation ...
Indian Academy of Sciences (India)
Home; Journals; Proceedings – Mathematical Sciences; Volume 123; Issue 4. Global Existence of Solutions for a Viscous Cahn-Hilliard Equation with Gradient Dependent Potentials and Sources. Chengyuan Qu Yang Cao ... Keywords. Global solution; viscous Cahn–Hilliard equation; initial boundary value problem ...
Global existence of solutions for a viscous Cahn–Hilliard equation ...
Indian Academy of Sciences (India)
We consider a class of nonlinear viscous Cahn–Hilliard equations with gradient dependent potentials and sources. By a Galerkin approximation scheme combined with the potential well method, we prove the global existence of weak solutions. Keywords. Global solution; viscous Cahn–Hilliard equation; initial boundary ...
Exact unsteady solutions to the Navier-Stokes and viscous MHD equations
Energy Technology Data Exchange (ETDEWEB)
Bogoyavlenskij, Oleg I
2003-02-10
Infinite-dimensional families of exact solutions that depend on all four variables t,x,y,z are derived for the Navier-Stokes equations and for viscous magnetohydrodynamics equations. Soliton-like solutions--viscons--are introduced.
Fundamentals of Shallow Water Acoustics
Katsnelson, Boris; Lynch, James
2012-01-01
Shallow water acoustics (SWA), the study of how low and medium frequency sound propagates and scatters on the continental shelves of the world's oceans, has both technical interest and a large number of practical applications. Technically, shallow water poses an interesting medium for the study of acoustic scattering, inverse theory, and propagation physics in a complicated oceanic waveguide. Practically, shallow water acoustics has interest for geophysical exploration, marine mammal studies, and naval applications. Additionally, one notes the very interdisciplinary nature of shallow water acoustics, including acoustical physics, physical oceanography, marine geology, and marine biology. In this specialized volume, the authors, all of whom have extensive at-sea experience in U.S. and Russian research efforts, have tried to summarize the main experimental, theoretical, and computational results in shallow water acoustics, with an emphasis on providing physical insight into the topics presented.
A Boundary Control Problem for the Viscous Cahn–Hilliard Equation with Dynamic Boundary Conditions
Energy Technology Data Exchange (ETDEWEB)
Colli, Pierluigi, E-mail: pierluigi.colli@unipv.it; Gilardi, Gianni, E-mail: gianni.gilardi@unipv.it [Universitá di Pavia and Research Associate at the IMATI – C.N.R. PAVIA, Dipartimento di Matematica “F. Casorati” (Italy); Sprekels, Jürgen, E-mail: juergen.sprekels@wias-berlin.de [Weierstrass Institute (Germany)
2016-04-15
A boundary control problem for the viscous Cahn–Hilliard equations with possibly singular potentials and dynamic boundary conditions is studied and first order necessary conditions for optimality are proved.
Shallow water sponges of Jamaica
Lehnert, Helmut; Soest, van Rob W.M.
1998-01-01
An annotated comprehensive list is provided of all shallow-water sponges (down to 60 m) recently collected and previously recorded from Jamaica. Five new species are described, Plakina jamaicensis, Melophlus ruber, Agelas repens, Stylissa caribica and Hyrtios tubulatus, two of which belong to genera
Saha Ray, S.; Sahoo, S.
2017-01-01
In the present paper, we construct the analytical exact solutions of some nonlinear evolution equations in mathematical physics; namely time fractional modified Kawahara equations by using the ( G^'/G)-expansion method via fractional complex transform. As a result, new types of exact analytical solutions are obtained.
2015-09-30
1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Shallow-Water Mud Acoustics William L. Siegmann...models and methods that explain observed material and acoustic properties of different physical types of shallow-ocean mud sediments. Other goals...are to assess prior data relating to the acoustic properties of mud and to provide guidance in the development and interpretation of experiments. A
2010 Hudson River Shallow Water Sediment Cores
National Oceanic and Atmospheric Administration, Department of Commerce — The Hudson River Shallow Water Mapping project characterizes the bottom of the Hudson River Estuary in shallow water (<3 m). The characterization includes...
2010 Hudson River Shallow Water Sediment Grabs
National Oceanic and Atmospheric Administration, Department of Commerce — The Hudson River Shallow Water Mapping project characterizes the bottom of the Hudson River Estuary in shallow water (<3 m). The characterization includes...
Zakharov equations for viscous flow and their use in the blood clot ...
Indian Academy of Sciences (India)
Ai-Ping Zhou
2017-11-14
Nov 14, 2017 ... Abstract. For theoretical study, blood can be regarded as a viscous electrically conducting fluid of negative ions and protons. Zakharov equations including viscosity are relevant for describing the behaviour of blood plasma. The dispersion formula is derived from the perturbation method and is solved ...
Zakharov equations for viscous flow and their use in the blood clot ...
Indian Academy of Sciences (India)
For theoretical study, blood can be regarded as a viscous electrically conducting fluid of negative ions and protons. Zakharov equations including viscosity are relevant for describing the behaviour of blood plasma. The dispersion formula is derived from the perturbation method and is solved numerically. It turns out that the ...
Improvements to the Solution of the Viscous Shock Layer Equations
1979-08-01
tD ~ L .[- 39 A EDC-TR-79-25 PW 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 I I I I I FULL LAYER... tD o o ts ,-t ,~ II oq ¢N II 0 I o o I I Q o II Ii I ~ | < I G i 0 | o I ~q o m I o II El ~ ~ c...b4 + + tn) = d 4 (F6) + (b41Un 2Vn b43P n b44 Equations (F1) to (F6) in this arranged form, represent a system of block tridiagonal equations.
Zakharov equations for viscous flow and their use in the blood clot formation
Zhou, Ai-Ping; Li, Xiao-Qing
2017-12-01
For theoretical study, blood can be regarded as a viscous electrically conducting fluid of negative ions and protons. Zakharov equations including viscosity are relevant for describing the behaviour of blood plasma. The dispersion formula is derived from the perturbation method and is solved numerically. It turns out that the imaginary part of one root of the perturbation frequency is greater than zero, and modulation instability occurs. This would lead to the formation of blood clot. The viscous force can suppress the occurrence of instability and prevent thrombosis. One can find that the chaotic state of blood signals human health.
Directory of Open Access Journals (Sweden)
Vineet K. Srivastava
2013-12-01
Full Text Available This article describes a new implicit finite-difference method: an implicit logarithmic finite-difference method (I-LFDM, for the numerical solution of two dimensional time-dependent coupled viscous Burgers’ equation on the uniform grid points. As the Burgers’ equation is nonlinear, the proposed technique leads to a system of nonlinear systems, which is solved by Newton's iterative method at each time step. Computed solutions are compared with the analytical solutions and those already available in the literature and it is clearly shown that the results obtained using the method is precise and reliable for solving Burgers’ equation.
Valery Ivanovich ELFIMOV; Hamid KHAKZAD
2014-01-01
In this study, the performance of the extended shallow water model (ESWM) in evaluation of the flow regime of turbidity currents entering the Dez Reservoir was investigated. The continuity equations for fluid and particles and the Navier-Stokes equations govern the entire flow of turbidity currents. The shallow water equations governing the flow of the depositing phase of turbidity currents are derived from these equations. A case study was conducted on the flow regime of turbidity currents e...
Estimation of freak wave occurrence in shallow water regions
Kashima, Hiroaki
2014-05-01
In the last two decades, freak waves have become an important topic in engineering and science and are sometimes featured by a single and steep crest causing severe damage to offshore structures and vessels. An accurate estimation of maximum wave height and prediction of freak wave occurrence frequency is important for marine safety and ocean developments. According to several studies on freak waves, the deep-water third-order nonlinearity (quasi-resonant four-wave interactions) can lead to a significant enhancement of freak wave occurrence from normality. However, it is not clear the behavior of offshore generated freak waves shoaling to shallow water regions. In general, a numerical simulation based on Boussinesq model has been frequently and widely used to estimate wave transformation in shallow water regions and has high-level performance in the design of coast and harbor structures in Japan. However, it is difficult to describe the freak wave occurrence from deep to shallow water regions by the Boussinesq model because it can express only up to the second-order nonlinear interactions. There is a gap of governing equation between deep and shallow water regions from the extreme wave modeling point of view. It is necessary to investigate the aftereffects of generated freak waves by the third-order nonlinear interactions in deep water regions and their propagation to shallow water regions using the Boussinesq model. In this study, the model experiments in a wave tank and numerical simulations based on the Boussinesq model were conducted to estimate the freak wave occurrence from deep to shallow water regions. In the model experiments, the maximum wave height increases with an increase in kurtosis by the third-order nonlinear interactions in deep water regions. The dependence of kurtosis on freak wave occurrence weakens by the second-order nonlinear interactions associated with wave shoaling if dimensionless water depth kph becomes shallower than 1.363, which kp
Shallow water reverberation measurement and prediction
Muggleworth, Charles E.
1994-01-01
Approved for public release; distribution is unlimited Low frequency active sonar performance in shallow water is often limited by reverberation. Reverberation modeling in shallow water has been difficult due to the complexity of the multipath acoustic propagation problem inherent in shallow environments. In August 1992, a shallow water, low-frequency reverberation measurement was made in the Barents Sea utilizing explosive signal, underwater sound (SUS) charges as sound sources and a 16-e...
Evaluation of Surface Ducts in Shallow Water.
1982-03-29
to determine optimum freouency domains for sound propagation at those sites. 1.2 Background Ten shallow water stations were occupied during the FASOR ...selected two of the FASOR shallow water stations for an optimum frequency study. Results for a downward refraction profile were compared to optimum...and Reverberation from the Shallow-Water FASOR Areas with Comparisons to Propagation Loss Models, J. A. Whitney, Naval Ocean Systems Center TR 400
ANUGA SOFTWARE FOR NUMERICAL SIMULATIONS OF SHALLOW WATER FLOWS
Directory of Open Access Journals (Sweden)
Sudi Mungkasi
2012-07-01
Full Text Available Shallow water flows are governed by the shallow water wave equations, also known as the Saint-Venant system. This paper presents a finite volume method used to solve the two-dimensional shallow water wave equations and how the finite volume method is implemented in ANUGA software. This finite volume method is the numerical method underlying the software. ANUGA is open source software developed by Australian National University (ANU and Geoscience Australia (GA. This software uses the finite volume method with triangular domain discretisation for the computation. Four test cases are considered in order to evaluate the performance of the software. Overall, ANUGA is a robust software to simulate two-dimensional shallow water flows. Arus air dangkal diatur dalam persamaan gelombang air dangkal, dikenal sebagai sistem Saint-Venant. Penelitian ini menyajikan metode finite volumeyang digunakan untuk menyelesaikan persamaan gelombang air dangkal dua dimensi dan bagaimana metode finite volumediimplementasikan dalam perangkat lunak ANUGA. Metode finite volumeadalah metode numerik yang mendasari perangkat lunakANUGA. ANUGA sendiri adalah perangkat lunak open source yang dikembangkan oleh Australian National University(ANU dan Geoscience Australia (GA. Perangkat lunak ini menggunakan metode finite volumedengan diskritisasi domain segitiga dalam proseskomputasi. Empat uji kasus digunakan untuk mengevaluasi kinerja perangkat lunak. Secara keseluruhan, ANUGA adalah perangkat lunak yang robust untuk mensimulasikan dua dimensi aliran arus air dangkal.
Competing turbulent cascades and eddy-wave interactions in shallow water equilibria
Weichman, Peter B.
2017-03-01
In recent work, Renaud, Venaille, and Bouchet (RVB) [Renaud et al., J. Stat. Phys. 163, 784 (2016), 10.1007/s10955-016-1496-x] revisit the equilibrium statistical mechanics theory of the shallow water equations, within a microcanonical approach, focusing on a more careful treatment of the energy partition between inertial gravity wave and eddy motions in the equilibrium state and deriving joint probability distributions for the corresponding dynamical degrees of freedom. The authors derive a Liouville theorem that determines the underlying phase space statistical measure, but then, through some physical arguments, actually compute the equilibrium statistics using a measure that violates this theorem, choosing equal volume vs equal area fluid parcels. Here, using a more convenient, but essentially equivalent, grand canonical approach, the full statistical theory consistent with the Liouville theorem is derived. The results reveal several significant differences from the previous results (1) The microscale wave motions lead to a strongly fluctuating thermodynamics, including long-range correlations, in contrast to the mean-field-like behavior found by RVB. The final effective model is equivalent to that of an elastic membrane with a nonlinear wave-renormalized surface tension. (2) Even when a mean-field approximation is made, a rather more complex joint probability distribution is revealed. Alternative physical arguments fully support the consistency of the results. Of course, the true fluid final steady state relies on dissipative processes not included in the shallow water equations, such as wave breaking and viscous effects, but it is argued that the current theory provides a more mathematically consistent starting point for future work aimed at assessing their impacts.
Acoustics of Shallow Water: A Status Report
1984-09-13
loss tend to have high reverberation. Figure 11, based on data from the four shallow water stations of FASOR 1 (25], shows the general correlation...derived from the FASOR program [241. Values of scattering strength for various angles are shown 24 ’% . .% % - . *.. ’ . ... ~. .. . - a...34.-. ..% . . -.. ’ 24. J. A. Whitney, "Propagation Losses and Reverberation from the Shallow- Water Fasor Areas with Comparisons to Propagation Loss
Dual integral porosity shallow water model for urban flood modelling
Guinot, Vincent; Sanders, Brett F.; Schubert, Jochen E.
2017-05-01
With CPU times 2 to 3 orders of magnitude smaller than classical shallow water-based models, the shallow water equations with porosity are a promising tool for large-scale modelling of urban floods. In this paper, a new model formulation called the Dual Integral Porosity (DIP) model is presented and examined analytically and computationally with a series of benchmark tests. The DIP model is established from an integral mass and momentum balance whereby both porosity and flow variables are defined separately for control volumes and boundaries, and a closure scheme is introduced to link control volume- and boundary-based flow variables. Previously developed Integral Porosity (IP) models were limited to a single set of flow variables. A new transient momentum dissipation model is also introduced to account for the effects of sub-grid scale wave action on porosity model solutions, effects which are validated by fine-grid solutions of the classical shallow-water equations and shown to be important for achieving similarity in dam-break solutions. One-dimensional numerical test cases show that the proposed DIP model outperforms the IP model, with significantly improved wave propagation speeds, water depths and discharge calculations. A two-dimensional field scale test case shows that the DIP model performs better than the IP model in mapping the floods extent and is slightly better in reproducing the anisotropy of the flow field when momentum dissipation parameters are calibrated.
Di Pietro, Daniele,; Marche, Fabien,
2017-01-01
In this paper, we further investigate the use of a fully discontinuous Finite Element discrete formulation for the study of shallow water free surface flows in the fully nonlinear and weakly dis-persive flow regime. We consider a decoupling strategy in which we approximate the solutions of the classical shallow water equations supplemented with a source term globally accounting for the non-hydrostatic effects. This source term can be computed through the resolution of elliptic second-order li...
Generalized solutions to linearized equations of thermoelastic solid and viscous thermofluid
Directory of Open Access Journals (Sweden)
Anvarbek M. Meirmanov
2007-03-01
Full Text Available Within the framework of continuum mechanics, the full description of joint motion of elastic bodies and compressible viscous fluids with taking into account thermal effects is given by the system consisting of the mass, momentum, and energy balance equations, the first and the second laws of thermodynamics, and an additional set of thermomechanical state laws. The present paper is devoted to the investigation of this system. Assuming that variations of the physical characteristics of the thermomechanical system of the fluid and the solid are small about some rest state, we derive the linearized non-stationary dynamical model, prove its well-posedness, establish additional refined global integral bounds for solutions, and further deduce the linearized incompressible models and models incorporating absolutely rigid skeleton, as asymptotic limits.
Three-dimensional shallow water system: A relaxation approach
Liu, Xin; Mohammadian, Abdolmajid; Infante Sedano, Julio Ángel; Kurganov, Alexander
2017-03-01
We study a three-dimensional shallow water system, which is obtained from the three-dimensional Navier-Stokes equations after Reynolds averaging and under the simplifying hydrostatic pressure assumption. Since the three-dimensional shallow water system is generically not hyperbolic, it cannot be numerically solved using hyperbolic shock capturing schemes. At the same time, existing simple finite-difference and finite-volume methods may fail in simulations of unsteady flows with sharp gradients, such as dam-break and flood flows. To overcome this limitation, we propose a novel numerical method, which is based on a relaxation approach utilized to ;hyperbolize; the three-dimensional shallow water system. The extended relaxation system is hyperbolic and we develop a second-order semi-discrete central-upwind scheme for it. The proposed numerical method can preserve ;lake at rest; steady states and positivity of water depth over irregular bottom topography. The accuracy, stability and robustness of the developed numerical method is verified on five numerical experiments.
Three-Dimensional Shallow Water Acoustics
2016-03-30
13-1-0026 entitled "Three- Dimensional Shallow Water Acoustics ," Principal Investigator Dr. Ying-Tsong Lin. Sincerely, ;l1,J-Ju1 ~{hjM1...30/03/2016 01/01/2013-12/31/2015 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBERS Three-Dimensional Shallow Water Acoustics 5b, GRANT NUMBER N0001 4-13-1...effects. The long-term goals of this project are targeted on understanding the 3-D acoustic effects, and their temporal and spatial variability, caused
Shallow water sound propagation with surface waves.
Tindle, Chris T; Deane, Grant B
2005-05-01
The theory of wavefront modeling in underwater acoustics is extended to allow rapid range dependence of the boundaries such as occurs in shallow water with surface waves. The theory allows for multiple reflections at surface and bottom as well as focusing and defocusing due to reflection from surface waves. The phase and amplitude of the field are calculated directly and used to model pulse propagation in the time domain. Pulse waveforms are obtained directly for all wavefront arrivals including both insonified and shadow regions near caustics. Calculated waveforms agree well with a reference solution and data obtained in a near-shore shallow water experiment with surface waves over a sloping bottom.
Cagnetti, Filippo
2015-01-01
We investigate large-time asymptotics for viscous Hamilton-Jacobi equations with possibly degenerate diffusion terms. We establish new results on the convergence, which are the first general ones concerning equations which are neither uniformly parabolic nor first order. Our method is based on the nonlinear adjoint method and the derivation of new estimates on long time averaging effects. It also extends to the case of weakly coupled systems.
Floating offshore wind turbines for shallow waters
Bulder, B.H.; Henderson, A.; Huijsmans, R.H.M.; Peeringa, J.M.; Pierik, J.T.G.; Snijders, E.J.B.; Hees, M.Th. van; Wijnants, G.H.; Wolf, M.J.
2003-01-01
Bottom mounted Offshore wind turbines seem to have a promising future but they are restricted to shallow waters of Northern Europe. Many projects are planned or are in the phase of construction on the North Sea and the Baltic Sea. All projects that are planned have a water depth up to approximately
Viscous-inviscid interaction using the parabolized Navier-Stokes equations
DEFF Research Database (Denmark)
Filippone, Antonino; Sørensen, Jens Nørkær
1997-01-01
A numerical model for the calculation of incompressible viscous flows past airfoils andwings has been developed. The approach is based on a strong viscous-inviscid coupling of aboundary element method with the Navier-Stokesequations in vorticity-streamfunction formulation.A semi-adaptive or fully...
Validation of ANUGA hydraulic model using exact solutions to shallow water wave problems
Mungkasi, S.; Roberts, S. G.
2013-04-01
ANUGA is an open source and free software developed by the Australian National University (ANU) and Geoscience Australia (GA). This software is a hydraulic numerical model used to solve the two-dimensional shallow water equations. The numerical method underlying it is a finite volume method. This paper presents some validation results of ANUGA with respect to exact solutions to shallow water flow problems. We identify the strengths of ANUGA and comment on future work that may be taken into account for ANUGA development.
Solitary and cnoidal wave scattering by a submerged horizontal plate in shallow water
Directory of Open Access Journals (Sweden)
Masoud Hayatdavoodi
2017-06-01
Full Text Available Solitary and cnoidal wave transformation over a submerged, fixed, horizontal rigid plate is studied by use of the nonlinear, shallow-water Level I Green-Naghdi (GN equations. Reflection and transmission coefficients are defined for cnoidal and solitary waves to quantify the nonlinear wave scattering. Results of the GN equations are compared with the laboratory experiments and other theoretical solutions for linear and nonlinear waves in intermediate and deep waters. The GN equations are then used to study the nonlinear wave scattering by a plate in shallow water. It is shown that in deep and intermediate depths, the wave-scattering varies nonlinearly by both the wavelength over the plate length ratio, and the submergence depth. In shallow water, however, and for long-waves, only the submergence depth appear to play a significant role on wave scattering. It is possible to define the plate submergence depth and length such that certain wave conditions are optimized above, below, or downwave of the plate for different applications. A submerged plate in shallow water can be used as a means to attenuate energy, such as in wave breakers, or used for energy focusing, and in wave energy devices.
Pothanna, N.; Aparna, P.; Gorla, R. S. R.
2017-12-01
In this paper we present numerical solutions to coupled non-linear governing equations of thermo-viscous fluid flow in cylindrical geometry using MATHEMATICA software solver. The numerical results are presented in terms of velocity, temperature and pressure distribution for various values of the material parameters such as the thermo-mechanical stress coefficient, thermal conductivity coefficient, Reiner Rivlin cross viscosity coefficient and the Prandtl number in the form of tables and graphs. Also, the solutions to governing equations for slow steady motion of a fluid have been obtained numerically and compared with the existing analytical results and are found to be in excellent agreement. The results of the present study will hopefully enable a better understanding applications of the flow under consideration.
Directory of Open Access Journals (Sweden)
Pothanna N.
2017-12-01
Full Text Available In this paper we present numerical solutions to coupled non-linear governing equations of thermo-viscous fluid flow in cylindrical geometry using MATHEMATICA software solver. The numerical results are presented in terms of velocity, temperature and pressure distribution for various values of the material parameters such as the thermo-mechanical stress coefficient, thermal conductivity coefficient, Reiner Rivlin cross viscosity coefficient and the Prandtl number in the form of tables and graphs. Also, the solutions to governing equations for slow steady motion of a fluid have been obtained numerically and compared with the existing analytical results and are found to be in excellent agreement. The results of the present study will hopefully enable a better understanding applications of the flow under consideration.
Shallow-water spinal injuries – devastating but preventable | Vlok ...
African Journals Online (AJOL)
Shallow-water spinal injuries – devastating but preventable. AJ Vlok, I Petersen, RN Dunn, J Stander. Abstract. Background. Shallow-water diving injuries have devastating consequences for patients and their families, requiring intensive use of resources in both the acute and rehabilitative phases of injury. With the final ...
Shallow-water loading tides in Japan from superconducting gravimetry
DEFF Research Database (Denmark)
Khan, Shfaqat Abbas; Hoyer, J.L.
2004-01-01
Gravity observations from superconducting gravimeters are used to observe loading effects from shallow-water tides on the Japanese cast and west coasts. Non-linear third-diurnal and higher-frequency shallow-water tides are identified in the tide-gauge observations from these coastal areas. The mo...
Shallow water currents during Hurricane Andrew
Keen, Timothy R.; Glenn, Scott M.
1999-10-01
Oceanographic measurements are used in combination with a numerical model to examine the influence of stratification on shallow water currents during the directly forced stage of a tropical cyclone (Hurricane Andrew) on the continental shelf. The following stratification-dependent coastal processes are examined: (1) turbulent mixing, (2) coastally trapped waves, (3) near-inertial oscillations, and (4) upwelling and downwelling. Turbulent mixing was strong within 1 Rw (radius of maximum winds) of the storm track, and stratification was nearly destroyed. Turbulent mixing was weak at distances greater than 2 Rw. The dominant coastal wave was a barotropic Kelvin wave generated as the storm surge relaxed after landfall. Baroclinic near-inertial oscillations were dominant at the shelf break and occurred along with a barotropic response on the middle shelf. Downwelling-favorable flow developed east of the track prior to the storm peak, and upwelling-favorable flow evolved west of the track as the eye crossed the shelf. The idealized storm flow was modified by local barotropic and baroclinic pressure gradients on the shelf. Ocean circulation during Hurricane Andrew was hindcast using both stratified and unstratified three-dimensional numerical models. For areas within 1 Rw of the storm track, the unstratified model matched the observed currents better than the stratified model, partly because of errors in the initial stratification. At distances greater than 2 Rw the influence of stratification increases, and the unstratified model does not reproduce the observed upwelling-favorable flow.
Floating offshore wind turbines for shallow waters
Energy Technology Data Exchange (ETDEWEB)
Bulder, B.H.; Peeringa, J.M.; Pierik, J.T.G. [ECN Wind Energy, Petten (Netherlands); Henderson, A. [Section Wind Energy, Delft University of Technology, Delft (Netherlands); Huijsmans, R.H.M.; Van Hees, M.Th. [Maritime Research Institute Netherlands, MARIN, Wageningen (Netherlands); Snijders, E.J.B. [Marine Structure Consultants MSC, Schiedam (Netherlands); Wijnants, G.H.; Wolf, M.J. [TNO, Delft (Netherlands)
2003-06-01
Bottom mounted Offshore wind turbines seem to have a promising future but they are restricted to shallow waters such as in Northern Europe. Many projects are planned or are in the phase of construction in the North Sea and the Baltic Sea. All projects planned to date are in water depths of up to approximately 25 m. The research project reported in this paper investigated the technical and economical feasibility of floating wind energy systems in deeper waters, of approximately 50 m and deeper. It is assumed that at a certain water depth floating wind turbines will have better economics than bottom mounted wind turbines. Floating wind energy systems seem to have some advantages over bottom mounted wind energy systems, such as: lower cost installation (in a harbour); lower maintenance cost; lower removal cost. But floating wind energy systems have their own technical challenges, such as dynamic interactions between floater and wind turbine; floater conceptual design including mooring system, taking into account restriction w.rt. stability of floater and wind turbine, minimizing wave induced motion, water depth, etc. This paper summarises the activities undertaken within the FloatWind feasibility study carried out during 2001-2002. Full details are to be found in the Final Report, also available from ECN or any of the authors.
A two-dimensional cell-centred finite volume model for quadrilateral grids is presented. The solution methodology of the depth-averaged shallow water equations is based upon a Godunov-type upwind finite volume formulation, whereby the inviscid fluxes of the system of equations are obtained using the...
Estimating the Strength of Superrotation with a Simplified Shallow-Water Model
Wang, H.; Wordsworth, R. D.
2016-12-01
Synchronously rotating close-in exoplanets, based on three-dimensional general circulation models, are usually expected to exhibit strong eastward equatorial jets (equatorial superrotation). The strength of equatorial superrotation greatly influences important observables, such as the day-night temperature difference and hottest region phase shift from the substellar point. Yet the strength of equatorial jets cannot be quantitatively predicted by current theories. We try to estimate the strength of superrotation with a simplified analytical model, which is based on a one-and-a-half-layer shallow water model. In our model, an active layer is governed by the shallow water equation, and a quiescent layer exchanges mass and momentum with the active layer. This shallow water model, originally proposed by Shell and Held (2004) to study superrotation, allows us to test different approximations that aid our estimation of the jet speed. In addition, by varying the interaction between the active layer and the immobile layer, we study how the lower atmosphere influences the dynamics and day-night gradient in the upper atmosphere and investigate the possibility of gathering information on the lower atmosphere by analyzing the observables of the upper atmosphere. We also compare our shallow-water model with an idealized three-dimensional general circulation model to assess the limitations of our model and theory.
Ashmawy, E. A.
2017-03-01
In this paper, we investigate the translational motion of a slip sphere with time-dependent velocity in an incompressible viscous fluid. The modified Navier-Stokes equation with fractional order time derivative is used. The linear slip boundary condition is applied on the spherical boundary. The integral Laplace transform technique is employed to solve the problem. The solution in the physical domain is obtained analytically by inverting the Laplace transform using the complex inversion formula together with contour integration. An exact formula for the drag force exerted by the fluid on the spherical object is deduced. This formula is applied to some flows, namely damping oscillation, sine oscillation and sudden motion. The numerical results showed that the order of the fractional derivative contributes considerably to the drag force. The increase in this parameter resulted in an increase in the drag force. In addition, the values of the drag force increased with the increase in the slip parameter.
Factorization in block-triangularly implicit methods for shallow water applications
P.J. van der Houwen; B.P. Sommeijer (Ben)
1999-01-01
textabstractThe system of first-order ordinary differential equations obtained by spatial discretization of the initial-boundary value problems modelling phenomena in shallow water in 3 spatial dimensions have righthand sides of the form f(t,y) := f1(t,y) + f2(t,y) + f3(t,y) + f4(t,y), where f1, f2
Dynamically adaptive Lattice Boltzmann simulation of shallow water flows with the Peano framework
Neumann, Philipp
2015-09-01
© 2014 Elsevier Inc. All rights reserved. We present a dynamically adaptive Lattice Boltzmann (LB) implementation for solving the shallow water equations (SWEs). Our implementation extends an existing LB component of the Peano framework. We revise the modular design with respect to the incorporation of new simulation aspects and LB models. The basic SWE-LB implementation is validated in different breaking dam scenarios. We further provide a numerical study on stability of the MRT collision operator used in our simulations.
Shallow Water Optical Water Quality Buoy
Bostater, Charles
1998-01-01
This NASA grant was funded as a result of an unsolicited proposal submission to Kennedy Space Center. The proposal proposed the development and testing of a shallow water optical water quality buoy. The buoy is meant to work in shallow aquatic systems (ponds, rivers, lagoons, and semi-enclosed water areas where strong wind wave action is not a major environmental During the project period of three years, a demonstration of the buoy was conducted. The last demonstration during the project period was held in November, 1996 when the buoy was demonstrated as being totally operational with no tethered communications line. During the last year of the project the buoy was made to be solar operated by large gel cell batteries. Fund limitations did not permit the batteries in metal enclosures as hoped for higher wind conditions, however the system used to date has worked continuously for in- situ operation of over 18 months continuous deployment. The system needs to have maintenance and somewhat continuous operational attention since various components have limited lifetime ages. For example, within the last six months the onboard computer has had to be repaired as it did approximately 6 months after deployment. The spectrograph had to be repaired and costs for repairs was covered by KB Science since no ftmds were available for this purpose after the grant expired. Most recently the computer web page server failed and it is currently being repaired by KB Science. In addition, the cell phone operation is currently being ftmded by Dr. Bostater in order to maintain the system's operation. The above points need to be made to allow NASA to understand that like any sophisticated measuring system in a lab or in the field, necessary funding and maintenance is needed to insure the system's operational state and to obtain quality factor. The proposal stated that the project was based upon the integration of a proprietary and confidential sensor and probe design that was developed by
Solving global shallow water equations on heterogeneous supercomputers.
Directory of Open Access Journals (Sweden)
Haohuan Fu
Full Text Available The scientific demand for more accurate modeling of the climate system calls for more computing power to support higher resolutions, inclusion of more component models, more complicated physics schemes, and larger ensembles. As the recent improvements in computing power mostly come from the increasing number of nodes in a system and the integration of heterogeneous accelerators, how to scale the computing problems onto more nodes and various kinds of accelerators has become a challenge for the model development. This paper describes our efforts on developing a highly scalable framework for performing global atmospheric modeling on heterogeneous supercomputers equipped with various accelerators, such as GPU (Graphic Processing Unit, MIC (Many Integrated Core, and FPGA (Field Programmable Gate Arrays cards. We propose a generalized partition scheme of the problem domain, so as to keep a balanced utilization of both CPU resources and accelerator resources. With optimizations on both computing and memory access patterns, we manage to achieve around 8 to 20 times speedup when comparing one hybrid GPU or MIC node with one CPU node with 12 cores. Using a customized FPGA-based data-flow engines, we see the potential to gain another 5 to 8 times improvement on performance. On heterogeneous supercomputers, such as Tianhe-1A and Tianhe-2, our framework is capable of achieving ideally linear scaling efficiency, and sustained double-precision performances of 581 Tflops on Tianhe-1A (using 3750 nodes and 3.74 Pflops on Tianhe-2 (using 8644 nodes. Our study also provides an evaluation on the programming paradigm of various accelerator architectures (GPU, MIC, FPGA for performing global atmospheric simulation, to form a picture about both the potential performance benefits and the programming efforts involved.
Shallow-Water Benthic Habitats of Southwest Puerto Rico
National Oceanic and Atmospheric Administration, Department of Commerce — Shallow-water (<30m) benthic habitat maps of the nearshore marine environment of two areas in Southwest Puerto Rico (PR), including the Guanica Bay/La Parguera...
Shallow-water Benthic Habitats in Jobos Bay
National Oceanic and Atmospheric Administration, Department of Commerce — Shallow-water (<30m) benthic habitat maps of the nearshore marine environment of Jobos Bay, Puerto Rico were mapped and characterized using visual interpretation...
Conservation laws and LETKF with 2D Shallow Water Model
Zeng, Yuefei; Janjic, Tijana
2016-04-01
Numerous approaches have been proposed to maintain physical conservation laws in the numerical weather prediction models. However, to achieve a reliable prediction, adequate initial conditions are also necessary, which are produced by a data assimilation algorithm. If an ensemble Kalman filters (EnKF) is used for this purpose, it has been shown that it could yield unphysical analysis ensemble that for example violates principles of mass conservation and positivity preservation (e.g. Janjic et al 2014) . In this presentation, we discuss the selection of conservation criteria for the analysis step, and start with testing the conservation of mass, energy and enstrophy. The simple experiments deal with nonlinear shallow water equations and simulated observations that are assimilated with LETKF (Localized Ensemble Transform Kalman Filter, Hunt et al. 2007). The model is discretized in a specific way to conserve mass, angular momentum, energy and enstrophy. The effects of the data assimilation on the conserved quantities (of mass, energy and enstrophy) depend on observation covarage, localization radius, observed variable and observation operator. Having in mind that Arakawa (1966) and Arakawa and Lamb (1977) showed that the conservation of both kinetic energy and enstrophy by momentum advection schemes in the case of nondivergent flow prevents systematic and unrealistic energy cascade towards high wave numbers, a cause of excessive numerical noise and possible eventual nonlinear instability, we test the effects on prediction depending on the type of errors in the initial condition. The performance with respect to nonlinear energy cascade is assessed as well.
Shallow water modeling of Jovian polar cyclone and vortices
Li, Cheng; Tabataba-Vakili, Fachreddin; Ingersoll, Andrew P.
2017-10-01
Jupiter’s polar atmosphere was observed for the first time by the Juno visible spectrum camera (JunoCAM) and Juno Infrared Auroral Mapper (JIRAM). Both the visible and infrared images show active vortices and weather systems that are unlike any polar regions previously seen or modeled on any of the planets in our solar system. We developed a global shallow water model on a sphere with poles rotated to the equator to investigate the formation, maintenance and dynamic regimes controlling the morphology of polar cyclones and vortices. Passive Lagrangian particles with finite life time are included to represent the clouds. We verified that a westward barotropically unstable jet can spontaneously break the axial symmetry into a polygon-shaped figure rotating rigidly around the rotation axis as reported by previous laboratory experiments. The number of sides of the polygon depends on the deformation radius and is insensitive to the initial condition. Why Jupiter’s pole is different from Saturn’s is still under investigation.
Modelling Shallow Water Wakes Using a Hybrid Turbulence Model
Directory of Open Access Journals (Sweden)
Clemente Rodriguez-Cuevas
2014-01-01
Full Text Available A numerical research with different turbulence models for shallow water equations was carried out. This was done in order to investigate which model has the ability to reproduce more accurately the wakes produced by the shock of the water hitting a submerged island inside a canal. The study of this phenomenon is important for the numerical methods application advancement in the simulation of free surface flows since these models involve a number of simplifications and assumptions that can have a significant impact on the numerical solutions quality and thus can not reproduce correctly the physical phenomenon. The numerical experiments were carried out on an experimental case under controlled conditions, consisting of a channel with a submerged conical island. The numerical scheme is based on the Eulerian-Lagrangian finite volume method with four turbulence models, three mixing lengths (ml, and one joining k-ϵ on the horizontal axis with a mixing-length model (ml on the vertical axis. The experimental results show that a k-ϵ with ml turbulence model makes it possible to approach the experimental results in a more qualitative manner. We found that when using only a k-ϵ model in the vertical and horizontal direction, the numerical results overestimate the experimental data. Additionally the computing time is reduced by simplifying the turbulence model.
Siewert, C. E.
2003-06-01
A polynomial expansion procedure and an analytical discrete-ordinates method are used to evaluate the viscous-slip coefficient, the thermal-slip coefficient, and the temperature-jump coefficient as defined by a rigorous version of the linearized Boltzmann equation for rigid-sphere interactions and the Cercignani-Lampis boundary condition.
Czech Academy of Sciences Publication Activity Database
Penel, P.; Straškraba, Ivan
2010-01-01
Roč. 134, č. 3 (2010), s. 278-294 ISSN 0007-4497 R&D Projects: GA ČR GA201/08/0012 Institutional research plan: CEZ:AV0Z10190503 Keywords : compressible fluid * Navier-Stokes equations * asymptotic behavior Subject RIV: BA - General Mathematics Impact factor: 0.722, year: 2010 http://www.sciencedirect.com/science/article/pii/S0007449709000153
Shallow Water Wave Models with and without Singular Kernel: Existence, Uniqueness, and Similarities
Directory of Open Access Journals (Sweden)
Emile Franc Doungmo Goufo
2017-01-01
Full Text Available After the recent introduction of the Caputo-Fabrizio derivative by authors of the same names, the question was raised about an eventual comparison with the old version, namely, the Caputo derivative. Unlike Caputo derivative, the newly introduced Caputo-Fabrizio derivative has no singular kernel and the concern was about the real impact of this nonsingularity on real life nonlinear phenomena like those found in shallow water waves. In this paper, a nonlinear Sawada-Kotera equation, suitable in describing the behavior of shallow water waves, is comprehensively analyzed with both types of derivative. In the investigations, various fixed-point theories are exploited together with the concept of Piccard K-stability. We are then able to obtain the existence and uniqueness results for the models with both versions of derivatives. We conclude the analysis by performing some numerical approximations with both derivatives and graphical simulations being presented for some values of the derivative order γ. Similar behaviors are pointed out and they concur with the expected multisoliton solutions well known for the Sawada-Kotera equation. This great observation means either of both derivatives is suitable to describe the motion of shallow water waves.
Shallow Water Simulations of the Three Last Saturn's Giant Storms
Garcia-Melendo, Enrique; Sanchez-Lavega, Agustin
2015-11-01
Shallow Water (SW) simulations are used to present a unified study of the polar (1960), equatorial (1990), and mid-latitude (2010) major storms in Saturn nicknamed as Great White Spots (GWS). The 2010 GWS appeared at +40, moved at -30 m s-1 where the Coriolis force is predominant producing an open anticyclone with a high speed peripheral circulation and a cloud front around the convective source; a long-lived anticyclone; and strong zonal advection on the south part of the storm forming a turbulent region. The 1990 GWS onset took place near the equator, between +12 and +5, on the broad prograde equatorial jet (450 m s-1) where equatorial dynamics dominated producing a storm nucleus, with rapid expansion to the west of a Kelvin-Helmholtz instability on the north side of the perturbation due to advection, and trapped equatorial waves which also expanded the storm to the east around the equator. The 1960 GWS appeared at high latitudes (+56) where Coriolis force is predominant in a region where zonal wind velocity is 0 m s-1. SW simulations predict a strong injection of relative vorticity which may produce large anticyclones on the anticyclonic side of the zonal profile, and a quick turbulent expansion on the background cyclonic regions at mid and high latitudes. In general, simulations indicate that negative relative vorticity injected by the storms also defines the natural interaction with the zonal winds at latitudes where the Coriolis force is dominant dictating its large scale dynamical behavior. Numerical experiments on the 1990 storm indicate that the onset of the storm can only be reproduced if the Voyager era background zonal flow is used, which suggests that it dominated the circulation dynamics at the storm’s outbreak region at that time. They also reproduce its most important morphological features, and show the production of planetary waves and turbulence. We discuss possible mechanism for the observed equatorial jet alterations during the storm
Di Pietro, Daniele A.; Marche, Fabien
2018-02-01
In this paper, we further investigate the use of a fully discontinuous Finite Element discrete formulation for the study of shallow water free surface flows in the fully nonlinear and weakly dispersive flow regime. We consider a decoupling strategy in which we approximate the solutions of the classical shallow water equations supplemented with a source term globally accounting for the non-hydrostatic effects. This source term can be computed through the resolution of elliptic second-order linear sub-problems, which only involve second order partial derivatives in space. We then introduce an associated Symmetric Weighted Internal Penalty discrete bilinear form, allowing to deal with the discontinuous nature of the elliptic problem's coefficients in a stable and consistent way. Similar discrete formulations are also introduced for several recent optimized fully nonlinear and weakly dispersive models. These formulations are validated again several benchmarks involving h-convergence, p-convergence and comparisons with experimental data, showing optimal convergence properties.
Retrieval of Inherent Optical Property in Optically Shallow Waters
Garcia, R. A.; Lee, Z.
2016-02-01
Standard ocean color algorithms for the retrieval of inherent optical properties (IOPs) either utilize spectral band ratios or inversion models tuned for the open ocean. However, such algorithms are known to fail in optically shallow waters, where bottom reflected light can contribute significantly to the water leaving radiance. Recently the SWIM algorithm was developed for improved retrievals of IOPs in optically shallow waters. This algorithm requires as input known bathymetric and substrate reflectance data that are often unknown and temporally variable for a region of interest. Here, we extend the applicability of the HOPE shallow water inversion model for the retrieval of IOPs in optically shallow waters with MODIS Aqua imagery. We investigate two approaches: (1) the use of coincident MERIS-derived bathymetry as a known input parameter to HOPE, and; (2) the inclusion the 469-, 555- and 645-nm MODIS bands without fixing any HOPE parameters to known values. With a MODIS Aqua image of the Great Bahamas Bank as an example, we compare the retrievals of aphy(443), adg(443) and bbp(443) from HOPE, SWIM and the GIOP and show that both aforementioned approaches provide temporal and spatial consistency within optically shallow water regions and between adjacent optically deep waters. Although both methods provide similar results the second approach is favored due to its independence from MERIS data.
Directory of Open Access Journals (Sweden)
Ahmed M. Elsayed
2013-01-01
Full Text Available Film cooling is vital to gas turbine blades to protect them from high temperatures and hence high thermal stresses. In the current work, optimization of film cooling parameters on a flat plate is investigated numerically. The effect of film cooling parameters such as inlet velocity direction, lateral and forward diffusion angles, blowing ratio, and streamwise angle on the cooling effectiveness is studied, and optimum cooling parameters are selected. The numerical simulation of the coolant flow through flat plate hole system is carried out using the “CFDRC package” coupled with the optimization algorithm “simplex” to maximize overall film cooling effectiveness. Unstructured finite volume technique is used to solve the steady, three-dimensional and compressible Navier-Stokes equations. The results are compared with the published numerical and experimental data of a cylindrically round-simple hole, and the results show good agreement. In addition, the results indicate that the average overall film cooling effectiveness is enhanced by decreasing the streamwise angle for high blowing ratio and by increasing the lateral and forward diffusion angles. Optimum geometry of the cooling hole on a flat plate is determined. In addition, numerical simulations of film cooling on actual turbine blade are performed using the flat plate optimal hole geometry.
Flexible riser global analysis for very shallow water
Karegar, Sadjad
2013-01-01
Master's thesis in Offshore technology Flexible risers are widely used for a range of water depths and can accommodate large floater motions when using a buoyant system. A wide range of buoyancy solutions have been developed for very shallow water (e.g. 30-50 m), shallow water (e.g. 90-110 m) and semi-deep water (e.g. 300-400 m) and in the ranges between these depths. Flexible risers can have different configurations. These different solutions have different characteristics which influe...
Energy Technology Data Exchange (ETDEWEB)
Klimachkov, D.A., E-mail: klimachkovdmitry@gmail.com [Space Research Institute of Russian Academy of Science, 84/32, Profsoyuznaya str., Moscow, 117997 (Russian Federation); Petrosyan, A.S. [Space Research Institute of Russian Academy of Science, 84/32, Profsoyuznaya str., Moscow, 117997 (Russian Federation); Moscow Institute of Physics and Technology (State University), 9 Institutskyi per., Dolgoprudny, Moscow Region, 141700 (Russian Federation)
2017-01-15
This article deals with magnetohydrodynamic (MHD) flows of a thin rotating layer of astrophysical plasma in external magnetic field. We use the shallow water approximation to describe thin rotating plasma layer with a free surface in a vertical external magnetic field. The MHD shallow water equations with external vertical magnetic field are revised by supplementing them with the equations that are consequences of the magnetic field divergence-free conditions and reveal the existence of third component of the magnetic field in such approximation providing its relation with the horizontal magnetic field. It is shown that the presence of a vertical magnetic field significantly changes the dynamics of the wave processes in astrophysical plasma compared to the neutral fluid and plasma layer in a toroidal magnetic field. The equations for the nonlinear wave packets interactions are derived using the asymptotic multiscale method. The equations for three magneto-Poincare waves interactions, for three magnetostrophic waves interactions, for the interactions of two magneto-Poincare waves and for one magnetostrophic wave and two magnetostrophic wave and one magneto-Poincare wave interactions are obtained. The existence of parametric decay and parametric amplifications is predicted. We found following four types of parametric decay instabilities: magneto-Poincare wave decays into two magneto-Poincare waves, magnetostrophic wave decays into two magnetostrophic waves, magneto-Poincare wave decays into one magneto-Poincare wave and one magnetostrophic wave, magnetostrophic wave decays into one magnetostrophic wave and one magneto-Poincare wave. Following mechanisms of parametric amplifications are found: parametric amplification of magneto-Poincare waves, parametric amplification of magnetostrophic waves, magneto-Poincare wave amplification in magnetostrophic wave presence and magnetostrophic wave amplification in magneto-Poincare wave presence. The instabilities growth rates
Directory of Open Access Journals (Sweden)
Valery Ivanovich ELFIMOV
2014-07-01
Full Text Available In this study, the performance of the extended shallow water model (ESWM in evaluation of the flow regime of turbidity currents entering the Dez Reservoir was investigated. The continuity equations for fluid and particles and the Navier-Stokes equations govern the entire flow of turbidity currents. The shallow water equations governing the flow of the depositing phase of turbidity currents are derived from these equations. A case study was conducted on the flow regime of turbidity currents entering the Dez Reservoir in Iran from January 2002 to July 2003. Facing a serious sedimentation problem, the dead storage of the Dez Reservoir will be full in the coming 10 years, and the inflowing water in the hydropower conduit system is now becoming turbid. Based on the values of the dimensionless friction number ( and dimensionless entrainment number ( of turbidity currents, and the coefficient of determination between the observed and predicted deposit depths (R2 = 0.86 for the flow regime of negligible friction and negligible entrainment (NFNE, the flow regime of turbidity currents coming into the Dez Reservoir is considered to be NFNE. The results suggest that the ESWM is an appropriate approach for evaluation of the flow regime of turbidity currents in dam reservoirs where the characteristics of turbidity currents, such as the deposit depth, must be evaluated.
Sediment distribution and composition on the shallow water ...
African Journals Online (AJOL)
Sediments of the shallow water carbonate basin in Zanzibar channel were investigated for composition and grain size distribution. The surface sediment composition was dominated by carbonate sands (with CaCO3 > 30%), except in the area adjacent to mainland coastline and a thin lobe which projects from Ruvu River to ...
Tactical operations in confined and shallow waters (TOPICS)
Kos, J.; Vermeulen, J.F.J.
1996-01-01
The tasks of navies have shifted towards crisis management and surveillance operations. Searching for a conventional submarine in confined and shallow waters in times of crisis becomes more and more important, The Operations Research model TOPICS should provide the Royal Netherlands Navy (RNLN with
Stochastic simulation of acoustic communication in turbulent shallow water
DEFF Research Database (Denmark)
Bjerrum-Niese, Christian; Lutzen, R.
2000-01-01
This paper presents a stochastic model of a turbulent shallow-water acoustic channel. The model utilizes a Monte Carlo realization method to predict signal transmission conditions. The main output from the model are statistical descriptions of the signal-to-multipath ratio (SMR) and signal fading...
Mode Colouration in Shallow-Water Ambient Noise,
The spectrum of ambient noise observed in the shallow waters of the Bristol Channel shows a series of characteristic peaks, e.g. at 10, 28, 47 Hz etc...and the presence of gas at the sea-bed. The significance is discussed for theories of ambient noise, microseisms and acoustic transmission. (Author)
Analysis of humpback whale sounds in shallow waters of the ...
Indian Academy of Sciences (India)
The primary objective of this work was to present the acoustical identification of humpback whales, detected by using an autonomous ambient noise measurement system, deployed in the shallow waters of the Southeastern Arabian Sea (SEAS) during the period January to May 2011. Seven types of sounds were detected.
Using Hough harmonics to validate and assess nonlinear shallow-water models
Dee, Dick P.; Moraes Da Silva, Arlindo
1986-01-01
The implementation of a technique for locating programming errors in shallow-water codes, establishing the correctness of the code, and assessing the performance of the numerical model under various flow conditions is described. The right-hand side of the differential equations is modified in such a way that the exact solution of the nonlinear initial-value problem is known, so that the truncation errors of the numerical scheme can be studied in detail. The exact solution is prescribed to be any linear combination of Hough harmonics which propagate in time according to their natural frequencies.
Preliminary Computational Fluid Dynamics (CFD) Simulation of EIIB Push Barge in Shallow Water
Beneš, Petr; Kollárik, Róbert
2011-12-01
This study presents preliminary CFD simulation of EIIb push barge in inland conditions using CFD software Ansys Fluent. The RANSE (Reynolds Averaged Navier-Stokes Equation) methods are used for the viscosity solution of turbulent flow around the ship hull. Different RANSE methods are used for the comparison of their results in ship resistance calculations, for selecting the appropriate and removing inappropriate methods. This study further familiarizes on the creation of geometrical model which considers exact water depth to vessel draft ratio in shallow water conditions, grid generation, setting mathematical model in Fluent and evaluation of the simulations results.
Shallow water simulations of Saturn's giant storms at different latitudes
García-Melendo, E.; Sánchez-Lavega, A.
2017-04-01
Shallow water simulations are used to present a unified study of three major storms on Saturn (nicknamed as Great White Spots, GWS) at different latitudes, polar (1960), equatorial (1990), and mid-latitude (2010) (Sánchez-Lavega, 2004; Sánchez-Lavega et al., 2011). In our model, the three GWS are initiated by introducing a Gaussian function pulse at the latitude of the observed phenomena with controlled horizontal size and amplitude. This function represents the convective source that has been observed to trigger the storm. A growing disturbance forms when the pulse reacts to ambient winds, expanding zonally along the latitude band of the considered domain. We then compare the modeled potential vorticity with the cloud field, adjusting the model parameters to visually get the closest aspect between simulations and observations. Simulations of the 2010 GWS (planetographic latitude ∼+40º, zonal velocity of the source ∼-30 m s-1) indicate that the Coriolis forces and the wind profile structure shape the disturbance generating, as observed, a long region to the east of the convective source with a high speed peripheral anticyclonic circulation, and a long-lived anticyclonic compact vortex accompanied by strong zonal advection on the southern part of the storm forming a turbulent region. Simulations of the equatorial 1990 GWS (planetographic latitude +12º-+5º, zonal velocity of the source 365-400 m s-1) show a different behavior because of the intense eastward jet, meridional shear at the equatorial region, and low latitude dynamics. A round shaped source forms as observed, with the rapid growth of a Kelvin-Helmholtz instability on the north side of the source due to advection and to the strong meridional wind shear, whereas at the storm latitude the disturbance grows and propagates eastward. The storm nucleus is the manifestation of a Rossby wave, while the eastward propagating planetary-scale disturbance is a gravity-Rossby wave trapped around the equator
Properties of underwater acoustic communication channels in shallow water.
Yang, T C
2012-01-01
Underwater acoustic channels are band-limited and reverberant, posing many obstacles to reliable, phase-coherent acoustic communications. While many high frequency communication experiments have been conducted in shallow water, few have carried out systematic studies on the channel properties at a time scale relevant for communications. To aid communication system design, this paper analyzes at-sea data collected in shallow water under various conditions to illustrate how the ocean environments (sea surface waves and random ocean medium) can affect the signal properties. Channel properties studied include amplitude and phase variations, and temporal coherence of individual paths as well as the temporal and spatial coherence of multipaths at different time scales. Reasons for the coherence loss are hypothesized. © 2012 Acoustical Society of America.
What now for shallow water. [Off Louisiana and Texas
Energy Technology Data Exchange (ETDEWEB)
Mosby, R.C.
1976-11-01
Improved prices and technological advances in well productivity prompt a fresh appraisal of bypassed reserves in some 20,000 sq miles of tidelands lying under 20--80 ft of water off the coasts of Louisiana and Texas. The resulting shallow-water drilling could bring new life to the ''obsolete'' submersible rig. The 25 existing drill rigs could drill an average of 175 exploratory wells per year if they were all available. Furthermore, well-designed submersible rigs and jackups can be built economically and are economical to operate and maintain. The new tradeoffs available with shallow-water operations should encourage operators to reevaluate the worked areas and explore the areas still open in water depths to 80 ft.
Fluctuations of Broadband Acoustic Signals in Shallow Water
2014-09-30
C. Development of time-reversal acoustic modem Digital-signal- processor ( DSP ) implementations of a low-complexity high-frequency underwater...shallow water We use model analysis to predict the performance of the time reversal processor . Equivalent to the matched-filtering operation, the...Song, M. Badiey, " DSP Implementation of Time-Reversal Receivers", (In Preparation), Marine Technology Society Journal, 2014. 16
Energy Technology Data Exchange (ETDEWEB)
Klimachkov, D. A., E-mail: klimchakovdmitry@gmail.com; Petrosyan, A. S., E-mail: apetrosy@iki.rssi.ru [Russian Academy of Sciences, Space Research Institute (Russian Federation)
2016-09-15
Shallow water magnetohydrodynamic (MHD) theory describing incompressible flows of plasma is generalized to the case of compressible flows. A system of MHD equations is obtained that describes the flow of a thin layer of compressible rotating plasma in a gravitational field in the shallow water approximation. The system of quasilinear hyperbolic equations obtained admits a complete simple wave analysis and a solution to the initial discontinuity decay problem in the simplest version of nonrotating flows. In the new equations, sound waves are filtered out, and the dependence of density on pressure on large scales is taken into account that describes static compressibility phenomena. In the equations obtained, the mass conservation law is formulated for a variable that nontrivially depends on the shape of the lower boundary, the characteristic vertical scale of the flow, and the scale of heights at which the variation of density becomes significant. A simple wave theory is developed for the system of equations obtained. All self-similar discontinuous solutions and all continuous centered self-similar solutions of the system are obtained. The initial discontinuity decay problem is solved explicitly for compressible MHD equations in the shallow water approximation. It is shown that there exist five different configurations that provide a solution to the initial discontinuity decay problem. For each configuration, conditions are found that are necessary and sufficient for its implementation. Differences between incompressible and compressible cases are analyzed. In spite of the formal similarity between the solutions in the classical case of MHD flows of an incompressible and compressible fluids, the nonlinear dynamics described by the solutions are essentially different due to the difference in the expressions for the squared propagation velocity of weak perturbations. In addition, the solutions obtained describe new physical phenomena related to the dependence of the
Lidocaine viscous, a local anesthetic, is used to treat the pain of a sore or irritated mouth ... associated with cancer chemotherapy and certain medical procedures. Lidocaine viscous is not normally used for sore throats ...
Critical speed for capillary-gravity surface flows in the dispersive shallow water limit
Pham, Chi-Tuong; Nore, Caroline; Brachet, Marc-Étienne
2005-06-01
The stability of perfect-fluid capillary-gravity surface flows past a cylindrical obstacle is studied in the shallow water limit, using the two-dimensional compressible Euler equations, with leading-order dispersive corrections. Stationary solutions with different contact angles are obtained by Newton branch following, based on Fourier pseudospectral methods, using mapped Chebychev polynomials. Stable and unstable branches are found to meet, through a saddle-node bifurcation, at a critical speed beyond which no stationary solution exists. For large obstacles, the stable branch is compared with the stationary solutions of the compressible Euler equation without dispersion. Boundary layers are investigated. In this regime, the unstable dynamics are shown to lead to a finite-time dewetting singularity.
On shallow water waves in a medium with time-dependent
Directory of Open Access Journals (Sweden)
Hamdy I. Abdel-Gawad
2015-07-01
Full Text Available In this paper, we studied the progression of shallow water waves relevant to the variable coefficient Korteweg–de Vries (vcKdV equation. We investigated two kinds of cases: when the dispersion and nonlinearity coefficients are proportional, and when they are not linearly dependent. In the first case, it was shown that the progressive waves have some geometric structures as in the case of KdV equation with constant coefficients but the waves travel with time dependent speed. In the second case, the wave structure is maintained when the nonlinearity balances the dispersion. Otherwise, water waves collapse. The objectives of the study are to find a wide class of exact solutions by using the extended unified method and to present a new algorithm for treating the coupled nonlinear PDE’s.
Shallow-water models with anisotropic porosity and merging for flood modelling on Cartesian grids
Bruwier, M.; Archambeau, P.; Erpicum, S.; Pirotton, M.; Dewals, B.
2017-11-01
Shallow-water models with porosity are used to compute floods at a relatively coarse resolution while accounting indirectly for detailed topographic data through porosity parameters. In many practical applications, these models enable a significant reduction of the computational time while maintaining an acceptable level of accuracy. In this paper, we improve the use of porosity models on Cartesian grids by three original contributions. First, a merging technique is used to handle cells with low porosity values which tend otherwise to seriously hamper computational efficiency. Next, we show that the optimal method for the determination of the porosity parameters depends on the modelling scale, i.e. the grid resolution compared to the characteristic size of obstacles and flow ways. Finally, we investigate the potential benefit of using a different porosity parameter in each term of the shallow-water equations. Five test cases, two of them being original, are used to validate the model and assess each contribution. In particular, we obtained speedup values between 10 and 100 while the errors on water depths remain around few percent.
Borisov, A. V.; Kuznetsov, S. P.; Mamaev, I. S.; Tenenev, V. A.
2016-09-01
From analysis of time series obtained on the numerical solution of a plane problem on the motion of a body with an elliptic cross section under the action of gravity force in an incompressible viscous fluid, a system of ordinary differential equations approximately describing the dynamics of the body is reconstructed. To this end, coefficients responsible for the added mass, the force caused by the circulation of the velocity field, and the resisting force are found by the least square adjustment. The agreement between the finitedimensional description and the simulation on the basis of the Navier-Stokes equations is illustrated by images of attractors in regular and chaotic modes. The coefficients found make it possible to estimate the actual contribution of different effects to the dynamics of the body.
Energy Technology Data Exchange (ETDEWEB)
Tautz, R. C., E-mail: robert.c.tautz@gmail.com [Zentrum für Astronomie und Astrophysik, Technische Universität Berlin, Hardenbergstraße 36, D-10623 Berlin (Germany); Lerche, I., E-mail: lercheian@yahoo.com [Institut für Geowissenschaften, Naturwissenschaftliche Fakultät III, Martin-Luther-Universität Halle, D-06099 Halle (Germany)
2015-11-15
This note considers the evolution of steady isothermal flow across a uniform magnetic field from an analytic standpoint. This problem is of concern in developments of magnetic fields in the solar corona and for prominence dynamics. Limiting behaviors are obtained to the nonlinear equation describing the flow depending on the value of a single parameter. For the situation where the viscous drag is a small correction to the inviscid flow limiting structures are also outlined. The purpose of the note is to show how one can evaluate some of the analytic properties of the highly nonlinear equation that are of use in considering the numerical evolution as done in Low and Egan [Phys. Plasmas 21, 062105 (2014)].
Nonlinear dynamics of rotating shallow water methods and advances
Zeitlin, Vladimir
2007-01-01
The rotating shallow water (RSW) model is of wide use as a conceptual tool in geophysical fluid dynamics (GFD), because, in spite of its simplicity, it contains all essential ingredients of atmosphere and ocean dynamics at the synoptic scale, especially in its two- (or multi-) layer version. The book describes recent advances in understanding (in the framework of RSW and related models) of some fundamental GFD problems, such as existence of the slow manifold, dynamical splitting of fast (inertia-gravity waves) and slow (vortices, Rossby waves) motions, nonlinear geostrophic adjustment and wa
Multipeakedness and groupiness of shallow water waves along Indian coast
Digital Repository Service at National Institute of Oceanography (India)
SanilKumar, V.; Anand, N.M.; AshokKumar, K.; Mandal, S.
and amplitudes of sea waves. JDurnal of GeDphysical Re search, 80(18), 2688-2694. MASSON, D. and CHAro.lJLER, P., 1993. Wave groups, a closer look at spectral methods. CDastal Engineering, 20, 249-275. MATHEW, J.; BABA. M., and KURIAN, N.P., 1995. Mudbanks... Research 1052-1065 West Palm Beach, Florida Fall 2003 Multipeakedness a,nd Groupiness of Shallow Water Waves Along Indian Coast v. Sanil Kumar, N.M. Anand, K. Ashok Kumar, and S. MandaI Ocean Engineering Division National Institute of Oceanography Goa-403...
Ray tracing in a turbulent, shallow-water channel
DEFF Research Database (Denmark)
Bjerrum-Niese, Christian; Lützen, René; Jensen, Leif Bjørnø
1998-01-01
A ray tracing model can be used to simulate sound (10–100 kHz) transmitted through shallow water. The phase of the ray arrivals, primarily given by travel time, may be mutually independent in such a multipath transmission. Consequently, the transmission loss in a receiving point is randomly valued...... due to the coherent interference of the multipath arrivals. This problem can be overcome by incoherent summation of the multipath arrivals. However, knowing that nature behaves coherently, this method is not preferred. Instead, the channel can be regarded as dynamic by allowing microfluctuations...
An Oil Fate Model for Shallow-Waters
Directory of Open Access Journals (Sweden)
Juan M. Restrepo
2015-12-01
Full Text Available We introduce a model for the dynamics of oil in suspension, appropriate for shallow waters, including the nearshore environment. This model is capable of oil mass conservation and does so by evolving the oil on the sea surface as well as the oil in the subsurface. The shallower portion of the continental shelf poses compounding unique modeling challenges. Many of these relate to the complex nature of advection and dispersion of oil in an environment in which wind, waves, as well as currents all play a role, as does the complex bathymetry and the nearshore geography. In this study we present an overview of the model as well as derive the most fundamental of processes, namely, the shallow water advectiion and dispersion processes. With regard to this basic transport, we superate several fundamental challenges associated with creating a transport model for oil and other buoyant pollutants, capable of capturing the dynamics at the large spatio-temporal scales demanded by environmental and hazard mitigation studies. Some of the strategies are related to dimension reduction and upscaling, and leave discussion of these to companion papers. Here we focus on wave-filtering, ensemble and depth-averaging. Integral to the model is the proposal of an ocean dynamics model that is consistent with the transport. This ocean dynamics model is detailed here. The ocean/oil transport model is applied to a couple of physically-inspired oil-spill problems in demonstrate its specialized capabilities.
This paper presents a depth-averaged two-dimensional shallow water model for simulating long waves in vegetated water bodies under breaking and non-breaking conditions. The effects of rigid vegetation are modelled in the form of drag and inertia forces as sink terms in the momentum equations. The dr...
A viscous compressible model of soap film flow and its equivalence with the Navier-Stokes equations
Fast, Petri
2005-01-01
We present a quasi-two dimensional model of flowing soap films that bears striking similarity to the compressible Navier-Stokes equations. The variation in soap film thickness that is commonly used for flow visualization in experiments is analogous to density variations in the Navier-Stokes equations. When the soap film flow velocity is comparable to the Marangoni elastic wave velocity we recover the compressible Navier-Stokes equations and the soap film behaves like a two-dimensional isother...
Directory of Open Access Journals (Sweden)
Sergey S. Khrapov
2013-01-01
Full Text Available The results of the numerical simulations of the dynamics of shallow waters for Volga-Akhtuba Floodplain are discussed. The mathematical model is based on the system of Saint-Venant equations. Numerical solution applies a combined Lagrangian-Eulerian (cSPH-TVD algorithm. We have investigated the features of the spring flood in 2011 and found the inapplicability of the hydrodynamical model with the constant roughness coefficient nM. We have found a good agreement between the results of numerical simulations and the observational data at gauging stations which allows us to estimate nM in low water nMmin=0.02 and the maximum water level in the river Volga nMmax= 0.06–0.07.
Turbulence modeling of transverse flow on ship hulls in shallow water
Energy Technology Data Exchange (ETDEWEB)
Jakobsen, Ken-Robert Gjelstad
2010-09-15
The hydrodynamic forces acting on a ship that travels in restricted water vary greatly with water depth and the geometry of the ship hull. This will affect the ship maneuverability in terms of various flow effects like for instance squat, when the ship is sucked down towards the seabed due to a pressure drop on the hull at forward speed. It is, thus, important to gain detailed knowledge on these aspects of marine engineering. The problem is in the present work addressed through a numerical investigation of turbulent transverse flow on two-dimensional ship sections in shallow water. The numerical code is validated against traditional flow problems in the literature. Namely, the Backward-facing step (BFS) and the Smoothly-contoured ramp (SCR). 2D and 3D laminar flows and 2D low Reynolds number turbulent flows are calculated, and the results are found to be in good agreement with the previous numerical and experimental comparison data. The turbulence model used in the calculations is the one-equation Spalart-Allmaras model. The overall goal of achieving more efficient and accurate numerical schemes will always be in focus of code development. Adaptive mesh refinement (AMR) is then a very helpful tool to save both time for grid generation prior to the calculations in question and the CPU hours needed to solve the governing equations. The latter is even more evident in a parallel environment. These aspects are included in the present investigation as part of the process to adapt and investigate a CFD tool suitable to handle turbulent flows on a ship hull in shallow water. Several physical and numerical parameters are included in the present study and the Plackett-Burman screening design is utilized to efficiently analyze the results. With the latter method, a simple function for calculating the drag force on a two-dimensional ship section as function of the given parameters has been obtained. (Author)
Modeling of SAR signatures of shallow water ocean topography
Shuchman, R. A.; Kozma, A.; Kasischke, E. S.; Lyzenga, D. R.
1984-01-01
A hydrodynamic/electromagnetic model was developed to explain and quantify the relationship between the SEASAT synthetic aperture radar (SAR) observed signatures and the bottom topography of the ocean in the English Channel region of the North Sea. The model uses environmental data and radar system parameters as inputs and predicts SAR-observed backscatter changes over topographic changes in the ocean floor. The model results compare favorably with the actual SEASAT SAR observed backscatter values. The developed model is valid for only relatively shallow water areas (i.e., less than 50 meters in depth) and suggests that for bottom features to be visible on SAR imagery, a moderate to high velocity current and a moderate wind must be present.
Manipulating Effective Gravity and Trapping Shallow Water Waves
Zareei, Ahmad; Alam, Mohammad-Reza
2017-11-01
A perfect manipulation of water waves in shallow water using transformation media methods usually requires changes in both water depth and gravitational acceleration as medium properties; however gravitational acceleration is always a physical constant. Reduced models and conformal transformations are used to keep the gravitational acceleration as a constant at the cost of performance and restriction of use. Here we present a novel method of changing effective gravitational acceleration using a visco-elastic bottom topography. This method of manipulating effective gravitational acceleration, beside changes in bottom topography, opens new applications toward controlling surface waves and enables perfect manipulation of water waves in a broad range of frequencies. Using the visco-elastic bottom topography, we present a GRIN-lens based wave-guide that traps water waves in a region along the axis of the lens. The presented method of manipulating effective gravitational acceleration can as well be applied to perfectly focus and rotate the waves for energy harvesting applications.
Instrumentation Suite for Acoustic Propagation Measurements in Complex Shallow Water Environments
Federal Laboratory Consortium — FUNCTION: Obtain at-sea measurements to test theoretical and modeling predictions of acoustic propagation in dynamic, inhomogeneous, and nonisotropic shallow water...
Viscous, Resistive Magnetorotational Modes
DEFF Research Database (Denmark)
Pessah, Martin Elias; Chan, Chi-kwan
2008-01-01
We carry out a comprehensive analysis of the behavior of the magnetorotational instability (MRI) in viscous, resistive plasmas. We find exact, non-linear solutions of the non-ideal magnetohydrodynamic (MHD) equations describing the local dynamics of an incompressible, differentially rotating back...
Kazama, Yoriko; Yamamoto, Tomonori
2017-10-01
Bathymetry at shallow water especially shallower than 15m is an important area for environmental monitoring and national defense. Because the depth of shallow water is changeable by the sediment deposition and the ocean waves, the periodic monitoring at shoe area is needed. Utilization of satellite images are well matched for widely and repeatedly monitoring at sea area. Sea bottom terrain model using by remote sensing data have been developed and these methods based on the radiative transfer model of the sun irradiance which is affected by the atmosphere, water, and sea bottom. We adopted that general method of the sea depth extraction to the satellite imagery, WorldView-2; which has very fine spatial resolution (50cm/pix) and eight bands at visible to near-infrared wavelengths. From high-spatial resolution satellite images, there is possibility to know the coral reefs and the rock area's detail terrain model which offers important information for the amphibious landing. In addition, the WorldView-2 satellite sensor has the band at near the ultraviolet wavelength that is transmitted through the water. On the other hand, the previous study showed that the estimation error by the satellite imagery was related to the sea bottom materials such as sand, coral reef, sea alga, and rocks. Therefore, in this study, we focused on sea bottom materials, and tried to improve the depth estimation accuracy. First, we classified the sea bottom materials by the SVM method, which used the depth data acquired by multi-beam sonar as supervised data. Then correction values in the depth estimation equation were calculated applying the classification results. As a result, the classification accuracy of sea bottom materials was 93%, and the depth estimation error using the correction by the classification result was within 1.2m.
Dippner, Joachim W.
1998-01-01
The mesoscale variability of the circulation of the German Bight is investigated for selected wind forcing situations with an eddy resolving model. A vorticity equation is derived which considers explicitly both mass distribution and tides. Different shallow water eddy regimes are identified in the German Bight. Using the vorticity equation, the statistical steady state eddy fields are analyzed with respect to the production mechanisms of the gyres and shallow water eddies. The large German Bight gyre is affected by the joint effect of baroclinicity and topography. It is demonstrated that all shallow water eddies which appear at the East-Friesian coast are affected by the interaction between wind stress and the gradient of bottom topography. Small shallow water eddies at the North-Friesian coast formed from the baroclinic forcing, the vortex squeezing and the interaction between wind stress and the gradient of bottom topography. The results further suggest that the contribution of advection or of tidal stress to the vorticity production is of minor relevance.
Dimitrov, D.
2012-10-01
We continue the series of papers, devoted to the investigation and simplification of the dynamical equation, governing the structure of the stationary elliptical accretion discs. These studies are in the frameworks, specified according to the model of Lyubarskij et al. [7]. In addition to the previous examinations, we find one more linear relation between the coefficients of this second order ordinary differential equation, which enables us to eliminate effectively at least four of them. This is in the course of our approach to reduce the number of these functions, depending on the eccentricity, its derivative and the power n in the viscosity law η = β Σ n. They appear in the equation during the process of averaging (i.e. integrating) over the azimuthal angle of the elliptical orbits. At the present stage of the investigations, there still remain three integrals of the indicated type. Except the case of integer values of n, their analytical solutions are not known. In connection with the linear dependence or independence of these functions (this is a subject of our future studies), the dynamical equation of the elliptical accretion discs may be split into a system of corresponding number of more simple equations about the unknown eccentricities of the particle orbits. Such an approach is in accordance with our base line, carried out through the referred series of papers, to make a progress, as much as possible, into the solving of the task by means of purely analytical methods. And only when the further advance in this way (if the final solution is not already attained) is so complicated, that it is impasse, to use numerical simulations.
Sprague, Mark W; Luczkovich, Joseph J
2016-01-01
This finite-difference time domain (FDTD) model for sound propagation in very shallow water uses pressure and velocity grids with both 3-dimensional Cartesian and 2-dimensional cylindrical implementations. Parameters, including water and sediment properties, can vary in each dimension. Steady-state and transient signals from discrete and distributed sources, such as the surface of a vibrating pile, can be used. The cylindrical implementation uses less computation but requires axial symmetry. The Cartesian implementation allows asymmetry. FDTD calculations compare well with those of a split-step parabolic equation. Applications include modeling the propagation of individual fish sounds, fish aggregation sounds, and distributed sources.
Müller, Hans-Georg
1992-01-01
MÜLLER, HANS-GEORG. Shallow-water Pycnogonida from Barbados, Lesser Antilles with description of Anoplodactylus Justi N. Sp., Studies Nat. Hist. Caribbean Region 71, Amsterdam 1992: 42-52. Eleven species of shallow-water Pycnogonida, one of which ( Anoplodactylus justi n. sp.) new to science, are
3D RANS simulations of shallow water effects on rudder hydrodynamic characteristics
Liu, J.; Hekkenberg, R.G.
2016-01-01
An accurate estimation of the rudder forces and moments is essential for manoeuvrability prediction. Previous research has shown that ships have different manoeuvring performance in deep and shallow water. Before considering the rudder’s contribution to shallow water manoeuvring, it is meaningful to
High Resolution Marine Magnetic Survey of Shallow Water Littoral Area
Directory of Open Access Journals (Sweden)
Jacob Sharvit
2007-09-01
Full Text Available The purpose of this paper is to present a system developed for detection andaccurate mapping of ferro-metallic objects buried below the seabed in shallow waters. Thesystem comprises a precise magnetic gradiometer and navigation subsystem, both installedon a non-magnetic catamaran towed by a low-magnetic interfering boat. In addition wepresent the results of a marine survey of a near-shore area in the vicinity of Atlit, a townsituated on the Mediterranean coast of Israel, about 15 km south of Haifa. The primarypurpose of the survey was to search for a Harvard airplane that crashed into the sea in 1960.A magnetic map of the survey area (3.5 km2 on a 0.5 m grid was created revealing theanomalies at sub-meter accuracy. For each investigated target location a correspondingferro-metallic item was dug out, one of which turned to be very similar to a part of thecrashed airplane. The accuracy of location was confirmed by matching the position of theactual dug artifacts with the magnetic map within a range of Ã‚Â± 1 m, in a water depth of 9 m.
Theoretical Model of Acoustic Wave Propagation in Shallow Water
Directory of Open Access Journals (Sweden)
Kozaczka Eugeniusz
2017-06-01
Full Text Available The work is devoted to the propagation of low frequency waves in a shallow sea. As a source of acoustic waves, underwater disturbances generated by ships were adopted. A specific feature of the propagation of acoustic waves in shallow water is the proximity of boundaries of the limiting media characterised by different impedance properties, which affects the acoustic field coming from a source situated in the water layer “deformed” by different phenomena. The acoustic field distribution in the real shallow sea is affected not only by multiple reflections, but also by stochastic changes in the free surface shape, and statistical changes in the seabed shape and impedance. The paper discusses fundamental problems of modal sound propagation in the water layer over different types of bottom sediments. The basic task in this case was to determine the acoustic pressure level as a function of distance and depth. The results of the conducted investigation can be useful in indirect determination of the type of bottom.
Caribbean Shallow-water Black Corals (Cnidaria: Anthozoa: Antipatharia)
Energy Technology Data Exchange (ETDEWEB)
Opresko, Dennis M [ORNL; Sanchez, Juan Armando [Universidad de los Andes
2005-01-01
Our aim is to provide a complete key and guide to the species of black corals from the Caribbean reefs at depths shallower than about 100 m. The key to the species is mostly based on colonial features that are recognized in the field, although some closely related species can only be differentiated by microscopic skeletal features. Each species is illustrated with one or more photos showing the size and shape of the colony; many photos were taken in the natural environment to facilitate underwater identification. Additionally, a short description is provided of each species and their microscopic diagnostic characters are illustrated with the aid of the Scanning Electron Microscope (SEM). Fifteen black coral species are found in relatively shallow-water in the Caribbean, Gulf of Mexico, and other parts of the tropical western Atlantic; these belong to the families Myriopathidae [Tanacetipathes hirta (Gray), T. tanacetum (Pourtales), T. barbadensis (Brook), T. thamnea (Warner), and Plumapathes pennacea (Pallas)]; Antipathidae [Antipathes lenta Pourtales, A. rubusifonnis Warner and Opresko, A. furcata Gray, A. umbratica Opresko, A. atlantica Gray, A. gracilis Gray, A. caribbeana Opresko, Stichopathes lutkeni Brook, and S. accidentalis (Gray)]; and Aphanipathidae [Rhipidipathes colombiana (Opresko and Sinchez)]. We hope that this guide will facilitate research on black corals on Caribbean reefs, where population surveys are urgently needed to evaluate or modify conservation policies.
Multiple-array passive acoustic source localization in shallow water.
Tollefsen, Dag; Gerstoft, Peter; Hodgkiss, William S
2017-03-01
This paper considers concurrent matched-field processing of data from multiple, spatially-separated acoustic arrays with application to towed-source data received on two bottom-moored horizontal line arrays from the SWellEx-96 shallow water experiment. Matched-field processors are derived for multiple arrays and multiple-snapshot data using maximum-likelihood estimates for unknown complex-valued source strengths and unknown error variances. Starting from a coherent processor where phase and amplitude is known between all arrays, likelihood expressions are derived for various assumptions on relative source spectral information (amplitude and phase at different frequencies) between arrays and from snapshot to snapshot. Processing the two arrays with a coherent-array processor (with inter-array amplitude and phase known) or with an incoherent-array processor (no inter-array spectral information) both yield improvements in localization over processing the arrays individually. The best results with this data set were obtained with a processor that exploits relative amplitude information but not relative phase between arrays. The localization performance improvement is retained when the multiple-array processors are applied to short arrays that individually yield poor performance.
Progress in the development of shallow-water mapping systems
Bergeron, E.; Worley, C.R.; O'Brien, T.
2007-01-01
The USGS (US Geological Survey) Coastal and Marine Geology has deployed an advance autonomous shallow-draft robotic vehicle, Iris, for shallow-water mapping in Apalachicola Bay, Florida. The vehicle incorporates a side scan sonar system, seismic-reflection profiler, single-beam echosounder, and global positioning system (GPS) navigation. It is equipped with an onboard microprocessor-based motor controller, delivering signals for speed and steering to hull-mounted brushless direct-current thrusters. An onboard motion sensor in the Sea Robotics vehicle control system enclosure has been integrated in the vehicle to measure the vehicle heave, pitch, roll, and heading. Three water-tight enclosures are mounted along the vehicle axis for the Edgetech computer and electronics system including the Sea Robotics computer, a control and wireless communications system, and a Thales ZXW real-time kinematic (RTK) GPS receiver. The vehicle has resulted in producing high-quality seismic reflection and side scan sonar data, which will help in developing the baseline oyster habitat maps.
Malkov, M A
1996-01-01
The asymptotic travelling wave solution of the KdV-Burgers equation driven by the long scale periodic driver is constructed. The solution represents a shock-train in which the quasi-periodic sequence of dispersive shocks or soliton chains is interspersed by smoothly varying regions. It is shown that the periodic solution which has the spatial driver period undergoes period doublings as the governing parameter changes. Two types of chaotic behavior are considered. The first type is a weak chaos, where only a small chaotic deviation from the periodic solution occurs. The second type corresponds to the developed chaos where the solution ``ignores'' the driver period and represents a random sequence of uncorrelated shocks. In the case of weak chaos the shock coordinate being repeatedly mapped over the driver period moves on a chaotic attractor, while in the case of developed chaos it moves on a repellor. Both solutions depend on a parameter indicating the reference shock position in the shock-train. The structure...
Directory of Open Access Journals (Sweden)
Tatiana Petrova
2016-08-01
Full Text Available An extremely interesting problem in aero-hydrodynamics is the sound radiation of a single vortical structure. Currently, this type of problem is mainly considered for an incompressible medium. In this paper a method was developed to take into account the viscosity and thermal conductivity of gas. The acoustic radiation frequency of a cylindrical vortex on a flat wall in viscous heat-conducting gas (air has been investigated. The problem is solved on the basis of the Navier–Stokes equations using the small initial vorticity approach. The power expansion of unknown functions in a series with a small parameter (vorticity is used. It is shown that there are high-frequency oscillations modulated by a low-frequency signal. The value of the high frequency remains constant for a long period of time. Thus the high frequency can be considered a natural frequency of the vortex radiation. The value of the natural frequency depends only on the initial radius of the cylindrical vortex, and does not depend on the intensity of the initial vorticity. As expected from physical considerations, the natural frequency decreases exponentially as the initial radius of the cylinder increases. Furthermore, the natural frequency differs from that of the oscillations inside the initial cylinder and in the outer domain. The results of the paper may be of interest for aeroacoustics and tornado modeling.
From Offshore to Onshore: Multiple Origins of Shallow-Water Corals from Deep-Sea Ancestors
Lindner, Alberto; Cairns, Stephen D.; Cunningham, Clifford W.
2008-01-01
Shallow-water tropical reefs and the deep sea represent the two most diverse marine environments. Understanding the origin and diversification of this biodiversity is a major quest in ecology and evolution. The most prominent and well-supported explanation, articulated since the first explorations of the deep sea, holds that benthic marine fauna originated in shallow, onshore environments, and diversified into deeper waters. In contrast, evidence that groups of marine organisms originated in the deep sea is limited, and the possibility that deep-water taxa have contributed to the formation of shallow-water communities remains untested with phylogenetic methods. Here we show that stylasterid corals (Cnidaria: Hydrozoa: Stylasteridae)—the second most diverse group of hard corals—originated and diversified extensively in the deep sea, and subsequently invaded shallow waters. Our phylogenetic results show that deep-water stylasterid corals have invaded the shallow-water tropics three times, with one additional invasion of the shallow-water temperate zone. Our results also show that anti-predatory innovations arose in the deep sea, but were not involved in the shallow-water invasions. These findings are the first robust evidence that an important group of tropical shallow-water marine animals evolved from deep-water ancestors. PMID:18560569
Calculations of Asteroid Impacts into Deep and Shallow Water
Gisler, Galen; Weaver, Robert; Gittings, Michael
2011-06-01
. There is some indication that near-field effects are more severe if the impact occurs in shallow water.
Model Based Predictive Control of AUVs for Station Keeping in a Shallow Water Wave Environment
National Research Council Canada - National Science Library
Riedel, Jeffery s; Healey, Anthony J
2005-01-01
.... In shallow water AUV operations, where large hydrodynamic forces are developed due to waves, knowledge of the sea is critical to allow for the design of a control system that will enable the vehicle...
Shallow-Water Benthic Habitats of Southwest Puerto Rico: Accuracy Assessment Site Locations
National Oceanic and Atmospheric Administration, Department of Commerce — Shallow-water (<30m) benthic habitat maps of the nearshore marine environment of two areas in Southwest Puerto Rico (PR), including the Guanica Bay/La Parguera...
Shallow-Water Benthic Habitats of Southwest Puerto Rico: GeoEye Image po_483895_PS
National Oceanic and Atmospheric Administration, Department of Commerce — Shallow-water (<30m) benthic habitat maps of the nearshore marine environment of two areas in Southwest Puerto Rico (PR), including the Guanica Bay/La Parguera...
Shallow-Water Benthic Habitats of Southwest Puerto Rico: GeoEye Image po_1700252_PS
National Oceanic and Atmospheric Administration, Department of Commerce — Shallow-water (<30m) benthic habitat maps of the nearshore marine environment of two areas in Southwest Puerto Rico (PR), including the Guanica Bay/La Parguera...
Shallow-Water Benthic Habitats of Southwest Puerto Rico: GeoEye Image po_0100092_PS
National Oceanic and Atmospheric Administration, Department of Commerce — Shallow-water (<30m) benthic habitat maps of the nearshore marine environment of two areas in Southwest Puerto Rico (PR), including the Guanica Bay/La Parguera...
Shallow-Water Benthic Habitats of Southwest Puerto Rico: GeoEye Image po_0900172_PS
National Oceanic and Atmospheric Administration, Department of Commerce — Shallow-water (<30m) benthic habitat maps of the nearshore marine environment of two areas in Southwest Puerto Rico (PR), including the Guanica Bay/La Parguera...
Shallow-Water Benthic Habitats of Southwest Puerto Rico: GeoEye Image po_0072610_PS
National Oceanic and Atmospheric Administration, Department of Commerce — Shallow-water (<30m) benthic habitat maps of the nearshore marine environment of two areas in Southwest Puerto Rico (PR), including the Guanica Bay/La Parguera...
Shallow-Water Benthic Habitats of Southwest Puerto Rico: GeoEye Image po_502736_PS
National Oceanic and Atmospheric Administration, Department of Commerce — Shallow-water (<30m) benthic habitat maps of the nearshore marine environment of two areas in Southwest Puerto Rico (PR), including the Guanica Bay/La Parguera...
Insights into Europa's Shallow Water Mobility from Thrace and Thera Macula
Schmidt, B. E.; Blankenship, D. D.; Patterson, G. W.; Schenk, P. M.
2012-03-01
Comparison of Thera and Thrace Macula shows evidence for shallow water mobility within Europa’s crust and places constraints on the timescales and direction of hydraulic water flow, as well as the material properties of the ice.
Shallow-Water Benthic Habitats of Southwest Puerto Rico: Ground Validation Site Locations
National Oceanic and Atmospheric Administration, Department of Commerce — Shallow-water (<30m) benthic habitat maps of the nearshore marine environment of two areas in Southwest Puerto Rico (PR), including the Guanica Bay/La Parguera...
Shallow-water Benthic Habitat Map (2013) for Coral Bay, St. John
National Oceanic and Atmospheric Administration, Department of Commerce — This shapefile contains information about the shallow-water (<40 meters) geology and biology of the seafloor in Coral Bay, St. John in the U.S. Virgin Islands...
ANALYTICAL MODELS OF EXOPLANETARY ATMOSPHERES. I. ATMOSPHERIC DYNAMICS VIA THE SHALLOW WATER SYSTEM
Energy Technology Data Exchange (ETDEWEB)
Heng, Kevin [Center for Space and Habitability, University of Bern, Sidlerstrasse 5, CH-3012 Bern (Switzerland); Workman, Jared, E-mail: kevin.heng@csh.unibe.ch, E-mail: jworkman@coloradomesa.edu [Colorado Mesa University, 1260 Kennedy Avenue, Grand Junction, CO 81501 (United States)
2014-08-01
Within the context of exoplanetary atmospheres, we present a comprehensive linear analysis of forced, damped, magnetized shallow water systems, exploring the effects of dimensionality, geometry (Cartesian, pseudo-spherical, and spherical), rotation, magnetic tension, and hydrodynamic and magnetic sources of friction. Across a broad range of conditions, we find that the key governing equation for atmospheres and quantum harmonic oscillators are identical, even when forcing (stellar irradiation), sources of friction (molecular viscosity, Rayleigh drag, and magnetic drag), and magnetic tension are included. The global atmospheric structure is largely controlled by a single key parameter that involves the Rossby and Prandtl numbers. This near-universality breaks down when either molecular viscosity or magnetic drag acts non-uniformly across latitude or a poloidal magnetic field is present, suggesting that these effects will introduce qualitative changes to the familiar chevron-shaped feature witnessed in simulations of atmospheric circulation. We also find that hydrodynamic and magnetic sources of friction have dissimilar phase signatures and affect the flow in fundamentally different ways, implying that using Rayleigh drag to mimic magnetic drag is inaccurate. We exhaustively lay down the theoretical formalism (dispersion relations, governing equations, and time-dependent wave solutions) for a broad suite of models. In all situations, we derive the steady state of an atmosphere, which is relevant to interpreting infrared phase and eclipse maps of exoplanetary atmospheres. We elucidate a pinching effect that confines the atmospheric structure to be near the equator. Our suite of analytical models may be used to develop decisively physical intuition and as a reference point for three-dimensional magnetohydrodynamic simulations of atmospheric circulation.
Guinot, Vincent
2017-09-01
The Integral Porosity and Dual Integral Porosity two-dimensional shallow water models have been proposed recently as efficient upscaled models for urban floods. Very little is known so far about their consistency and wave propagation properties. Simple numerical experiments show that both models are unusually sensitive to the computational grid. In the present paper, a two-dimensional consistency and characteristic analysis is carried out for these two models. The following results are obtained: (i) the models are almost insensitive to grid design when the porosity is isotropic, (ii) anisotropic porosity fields induce an artificial polarization of the mass/momentum fluxes along preferential directions when triangular meshes are used and (iii) extra first-order derivatives appear in the governing equations when regular, quadrangular cells are used. The hyperbolic system is thus mesh-dependent, and with it the wave propagation properties of the model solutions. Criteria are derived to make the solution less mesh-dependent, but it is not certain that these criteria can be satisfied at all computational points when real-world situations are dealt with.
Hybrid ensemble 4DVar assimilation of stratospheric ozone using a global shallow water model
Directory of Open Access Journals (Sweden)
D. R. Allen
2016-07-01
Full Text Available Wind extraction from stratospheric ozone (O3 assimilation is examined using a hybrid ensemble 4-D variational assimilation (4DVar shallow water model (SWM system coupled to the tracer advection equation. Stratospheric radiance observations are simulated using global observations of the SWM fluid height (Z, while O3 observations represent sampling by a typical polar-orbiting satellite. Four ensemble sizes were examined (25, 50, 100, and 1518 members, with the largest ensemble equal to the number of dynamical state variables. The optimal length scale for ensemble localization was found by tuning an ensemble Kalman filter (EnKF. This scale was then used for localizing the ensemble covariances that were blended with conventional covariances in the hybrid 4DVar experiments. Both optimal length scale and optimal blending coefficient increase with ensemble size, with optimal blending coefficients varying from 0.2–0.5 for small ensembles to 0.5–1.0 for large ensembles. The hybrid system outperforms conventional 4DVar for all ensemble sizes, while for large ensembles the hybrid produces similar results to the offline EnKF. Assimilating O3 in addition to Z benefits the winds in the hybrid system, with the fractional improvement in global vector wind increasing from ∼ 35 % with 25 and 50 members to ∼ 50 % with 1518 members. For the smallest ensembles (25 and 50 members, the hybrid 4DVar assimilation improves the zonal wind analysis over conventional 4DVar in the Northern Hemisphere (winter-like region and also at the Equator, where Z observations alone have difficulty constraining winds due to lack of geostrophy. For larger ensembles (100 and 1518 members, the hybrid system results in both zonal and meridional wind error reductions, relative to 4DVar, across the globe.
Directory of Open Access Journals (Sweden)
C. T. Duba
2012-05-01
Full Text Available Using the shallow water equations for a rotating layer of fluid, the wave and dispersion equations for Rossby waves are developed for the cases of both the standard β-plane approximation for the latitudinal variation of the Coriolis parameter f and a zonal variation of the shallow water speed. It is well known that the wave normal diagram for the standard (mid-latitude Rossby wave on a β-plane is a circle in wave number (ky,kx space, whose centre is displaced −β/2 ω units along the negative kx axis, and whose radius is less than this displacement, which means that phase propagation is entirely westward. This form of anisotropy (arising from the latitudinal y variation of f, combined with the highly dispersive nature of the wave, gives rise to a group velocity diagram which permits eastward as well as westward propagation. It is shown that the group velocity diagram is an ellipse, whose centre is displaced westward, and whose major and minor axes give the maximum westward, eastward and northward (southward group speeds as functions of the frequency and a parameter m which measures the ratio of the low frequency-long wavelength Rossby wave speed to the shallow water speed. We believe these properties of group velocity diagram have not been elucidated in this way before. We present a similar derivation of the wave normal diagram and its associated group velocity curve for the case of a zonal (x variation of the shallow water speed, which may arise when the depth of an ocean varies zonally from a continental shelf.
Rostami, M.; Zeitlin, V.
2017-12-01
We show how the properties of the Mars polar vortex can be understood in the framework of a simple shallow-water type model obtained by vertical averaging of the adiabatic “primitive” equations, and “improved” by inclusion of thermal relaxation and convective fluxes due to the phase transitions of CO 2, the major constituent of the Martian atmosphere. We perform stability analysis of the vortex, show that corresponding mean zonal flow is unstable, and simulate numerically non-linear saturation of the instability. We show in this way that, while non-linear adiabatic saturation of the instability tends to reorganize the vortex, the diabatic effects prevent this, and thus provide an explanation of the vortex form and longevity.
On the Simulation of Shallow Water Tides in the Vicinity of the Taiwan Banks
Directory of Open Access Journals (Sweden)
Ming-Da Chiou
2010-01-01
Full Text Available The Taiwan Banks (Formosa Shoals, a large NE-SW oriented bathymetric feature near the southern end (23°N, 118 - 119°E of the Taiwan Strait, is a region of extremely shallow water that exerts a profound effect on the propagation of tidal waves. As such waves propagate over the Taiwan Banks, they become distorted and asymmetric due to bottom friction and contribute to the generation of shallow water tides. The POM model was used in present study to simulate the tides in the Taiwan Strait region. Shallow water tidal dynamics in the area of Taiwan Banks are focused. The numerical model was validated against sea level observations from 34 tidal stations located on the coast of Mainland China and Taiwan. Trajectory records from two SVP drifters are used to be compared with the simulations using wavelet-based rotary spectral analysis.
The "shallow-waterness" of the wave climate in European coastal regions
Håkon Christensen, Kai; Carrasco, Ana; Bidlot, Jean-Raymond; Breivik, Øyvind
2017-07-01
In contrast to deep water waves, shallow water waves are influenced by bottom topography, which has consequences for the propagation of wave energy as well as for the energy and momentum exchange between the waves and the mean flow. The ERA-Interim reanalysis is used to assess the fraction of wave energy associated with shallow water waves in coastal regions in Europe. We show maps of the distribution of this fraction as well as time series statistics from eight selected stations. There is a strong seasonal dependence and high values are typically associated with winter storms, indicating that shallow water wave effects can occasionally be important even in the deeper parts of the shelf seas otherwise dominated by deep water waves.
Directory of Open Access Journals (Sweden)
Alexander V. Perig
2017-01-01
Full Text Available The present article is focused on a phenomenological description of a polymer workpiece Equal Channel Angular Extrusion (ECAE through 2θ-dies of Segal and Iwahashi geometries with a channel intersection angle 2θ = 105° with fixed and movable external inlet and outlet die walls. The local flow dynamics, including the formation of macroscopic rotation and a dead zone appearance during the flow of plasticine, paraffin, and wax workpiece models through the subject die configuration was studied using physical simulation techniques. The present article utilizes a Computational Fluid Dynamics (CFD numerical approach to a theoretical description of 2D viscous flow of incompressible Newtonian continuum through the stated die geometries. The boundary value problem for the Navier-Stokes equations in the curl transfer form for the local viscous flow was formulated and numerically solved with a finite-difference method. Theoretical CFD-derived plots with computational flow lines, dimensionless flow and curl functions, flow velocities, and tangential stresses for viscous material flow through the stated die geometries have been generated and described. As a first rheological approximation the derived computational results provide the theoretical description of physical simulation experiments and visualize the formation of ECAE-induced rotational modes of large deformations like macroscopic rotation and rotational inhomogeneity.
Conservation properties of smoothed particle hydrodynamics applied to the shallow water equations
J.E. Frank (Jason); S. Reich
2001-01-01
textabstractConservation of potential vorticity (PV) and Kelvin's circulation theorem express two of the fundamental concepts in ideal fluid dynamics. In this note, we discuss these two concepts in the context of the Smoothed Particle Hydrodynamics (SPH) method. We show that, if interpreted in an
Modelling the Shallow Water Equations in Curvilinear Coordinates with Physical Application
Energy Technology Data Exchange (ETDEWEB)
Wingenter, Suzanne [San Diego State Univ., CA (United States)
2005-01-12
The goal of this project is to provide the capability for simulating fluid flow on complicated geometries, such as in the Bahia de Todos Santos. The Bahia de Todos Santos is a bay situated in the northwest corner of Mexico, off the coast of Ensenada and south of San Diego, California, USA. Figure 1.1 shows the Bahia de Todos Santos. It is part of an image taken from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors on the Aqua and Terra satellites in late June and early July 2003 [8]. Roughly 200 square kilometers in size, the bay also contains two islands off the peninsula of Punta Banda. Characteristics of flow in this bay are driven by the moon tide (M2) and wind forcing [9].
Guinot, Vincent
2017-11-01
The validity of flux and source term formulae used in shallow water models with porosity for urban flood simulations is assessed by solving the two-dimensional shallow water equations over computational domains representing periodic building layouts. The models under assessment are the Single Porosity (SP), the Integral Porosity (IP) and the Dual Integral Porosity (DIP) models. 9 different geometries are considered. 18 two-dimensional initial value problems and 6 two-dimensional boundary value problems are defined. This results in a set of 96 fine grid simulations. Analysing the simulation results leads to the following conclusions: (i) the DIP flux and source term models outperform those of the SP and IP models when the Riemann problem is aligned with the main street directions, (ii) all models give erroneous flux closures when is the Riemann problem is not aligned with one of the main street directions or when the main street directions are not orthogonal, (iii) the solution of the Riemann problem is self-similar in space-time when the street directions are orthogonal and the Riemann problem is aligned with one of them, (iv) a momentum balance confirms the existence of the transient momentum dissipation model presented in the DIP model, (v) none of the source term models presented so far in the literature allows all flow configurations to be accounted for(vi) future laboratory experiments aiming at the validation of flux and source term closures should focus on the high-resolution, two-dimensional monitoring of both water depth and flow velocity fields.
A Three Dimensional Sea Facility for Deep and Shallow Water Waves
DEFF Research Database (Denmark)
Burcharth, Hans F.; Nielsen, Søren R.K.; Schaarup-Jensen, Kjeld
1986-01-01
The paper describes a low-cost wave tank for the testing of structures in short crested seas and current. The paddle system is of the snake type and used for the generation of both deep and shallow water waves. The quality of the waves and scale problems related to small scale tests are discussed...
Spread of Composite Pollutants in Shallow Waters of the Niger Delta ...
African Journals Online (AJOL)
Spread of Composite Pollutants in Shallow Waters of the Niger Delta. TM Abbey, O Anyalebechi, LA Akonye. Abstract. No Abstract. Full Text: EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. Article Metrics. Metrics Loading ... Metrics powered by PLOS ALM
Impacts of Ocean Acidification on Sediment Processes in Shallow Waters of the Arctic Ocean
Gazeau, F.; van Rijswijk, P.; Pozzato, L.; Middelburg, J.J.
2014-01-01
Despite the important roles of shallow-water sediments in global biogeochemical cycling, the effects of ocean acidification on sedimentary processes have received relatively little attention. As high-latitude cold waters can absorb more CO2 and usually have a lower buffering capacity than warmer
Impacts of ocean acidification on sediment processes in shallow waters of the Arctic Ocean
Gazeau, F.; van Rijswijk, P.; Pozzato, L.; Middelburg, J.J.|info:eu-repo/dai/nl/079665373
Despite the important roles of shallow-water sediments in global biogeochemical cycling, the effects of ocean acidification on sedimentary processes have received relatively little attention. As high-latitude cold waters can absorb more CO2 and usually have a lower buffering capacity than warmer
A new carnivorous shallow-water sponge from McMurdo Sound, Antarctica (Porifera, Poecilosclerida)
van Soest, R.W.M.; Baker, B.J.
2011-01-01
A new shallow-water representative of the carnviorous sponge genus Asbestopluma is described from the southernmost Antarctic region of McMurdo Sound. Asbestopluma (Asbestopluma) vaceleti n.sp. is a white, thin, sparingly branched sponge fringed by filaments along its entire length, with a slight
A revision of the Shallow-water Azooxanthellate Scleractinia of the Western Atlantic
Cairns, Stephen D.
2000-01-01
CAIRNS, S. D., 2000. A revision of the shallow-water azooxanthellate Scleractinia of the western Atlantic. Studies Nat. Hist. Caribbean Region 75, Amsterdam, 2000: 1-231. This paper constitutes the second of a two part revision of the western Atlantic azooxanthellate Scleractinia — this part
NEKTON HABITAT QUALITY AT SHALLOW-WATER SITES IN TWO RHODE ISLAND COASTAL SYSTEMS
We evaluated nekton habitat quality at five shallow-water sites in two Rhode Island systems by comparing nekton densities and biomass, number of species, prey availability and feeding, and abundance of winter flounder Pseudopleuronectes americanus. Nekton density and biomass wer...
SWIM: A Semi-Analytical Ocean Color Inversion Algorithm for Optically Shallow Waters
McKinna, Lachlan I. W.; Werdell, P. Jeremy; Fearns, Peter R. C. S.; Weeks, Scarla J.; Reichstetter, Martina; Franz, Bryan A.; Shea, Donald M.; Feldman, Gene C.
2014-01-01
Ocean color remote sensing provides synoptic-scale, near-daily observations of marine inherent optical properties (IOPs). Whilst contemporary ocean color algorithms are known to perform well in deep oceanic waters, they have difficulty operating in optically clear, shallow marine environments where light reflected from the seafloor contributes to the water-leaving radiance. The effect of benthic reflectance in optically shallow waters is known to adversely affect algorithms developed for optically deep waters [1, 2]. Whilst adapted versions of optically deep ocean color algorithms have been applied to optically shallow regions with reasonable success [3], there is presently no approach that directly corrects for bottom reflectance using existing knowledge of bathymetry and benthic albedo.To address the issue of optically shallow waters, we have developed a semi-analytical ocean color inversion algorithm: the Shallow Water Inversion Model (SWIM). SWIM uses existing bathymetry and a derived benthic albedo map to correct for bottom reflectance using the semi-analytical model of Lee et al [4]. The algorithm was incorporated into the NASA Ocean Biology Processing Groups L2GEN program and tested in optically shallow waters of the Great Barrier Reef, Australia. In-lieu of readily available in situ matchup data, we present a comparison between SWIM and two contemporary ocean color algorithms, the Generalized Inherent Optical Property Algorithm (GIOP) and the Quasi-Analytical Algorithm (QAA).
Importance of shallow-water bay biotopes as nurseries for Caribbean reef fishes
Nagelkerken, I.A.
2000-01-01
Mangroves and seagrass beds can harbour high densities of mostly juvenile fishes. It has therefore long been assumed that these habitats function as nursery areas. In the present thesis the nursery function of mangroves, seagrass beds and other shallow-water biotopes, located in sheltered inland
Questions Student Ask: Why Is It Harder to Paddle a Canoe in Shallow Water?
Physics Teacher, 1985
1985-01-01
Explains the effect that depth of water has on the speed of Olympic-style racing canoes and kayaks. Indicates that canoes are harder to paddle in shallow water because the skin friction drag increases appreciable when the water depth decreases. (DH)
Metabolic and Cardiovascular Response to Shallow Water Exercise in Young and Older Women.
Campbell, Jennifer A.; D'Acquisto, Leo J.; D'Acquisto, Debra M.; Cline, Michael G.
2003-01-01
Compared the metabolic and cardiovascular responses of young and older women while performing shallow water exercise (SWE). Overall, SWE elicited metabolic and cardiovascular responses that met American College of Sports Medicine's guidelines for establishing health benefits. Older females self-selected a greater relative exercise intensity during…
Spatial and temporal variation of surface waves in shallow waters along the eastern Arabian Sea.
Digital Repository Service at National Institute of Oceanography (India)
Anoop, T.R.; SanilKumar, V.; Shanas, P.R.
We studied the spatial and temporal variation of surface waves along the eastern Arabian Sea during 2011 and 2012. Measured directional wave data at two shallow water locations and re-analysis datasets (ERA-Interim) at 0.751 intervals at four...
Shallow-water Mysidacea from the Lesser Antilles and other Caribbean regions
Brattegard, Torleiv
1975-01-01
This report is the seventh in a series of papers dealing with Mysidacea (Crustacea) from shallow water in the tropical and warm-temperate areas of the western Atlantic (BRATTEGARD 1969, 1970a, 1970b, 1973, 1974a, 1974b). Five of these are dealing with material collected by the author in southern
The effect of sound speed profile on shallow water shipping sound maps
Sertlek, H.Ö.; Binnerts, B.; Ainslie, M.A.
2016-01-01
Sound mapping over large areas can be computationally expensive because of the large number of sources and large source-receiver separations involved. In order to facilitate computation, a simplifying assumption sometimes made is to neglect the sound speed gradient in shallow water. The accuracy of
Latitudinal trends in habitat quality of shallow-water flatfish nurseries
Freitas, V.; Kooijman, S.A.L.M.; van der Veer, H.W.
2012-01-01
The habitat quality of European shallow-water nurseries was studied for 3 common flatfish species based on juvenile growth conditions. Field growth of 0-group plaice Pleuronectes platessa, flounder Platichthys flesus and sole Solea solea, from both published and unpublished studies, was compared
Evaluation of 2D shallow-water model for spillway flow with a complex geometry
Although the two-dimensional (2D) shallow water model is formulated based on several assumptions such as hydrostatic pressure distribution and vertical velocity is negligible, as a simple alternative to the complex 3D model, it has been used to compute water flows in which these assumptions may be ...
Conservative arbitrary order finite difference schemes for shallow-water flows
Skiba, Yuri N.; Filatov, Denis M.
2008-09-01
The classical nonlinear shallow-water model (SWM) of an ideal fluid is considered. For the model, a new method for the construction of mass and total energy conserving finite difference schemes is suggested. In fact, it produces an infinite family of finite difference schemes, which are either linear or nonlinear depending on the choice of certain parameters. The developed schemes can be applied in a variety of domains on the plane and on the sphere. The method essentially involves splitting of the model operator by geometric coordinates and by physical processes, which provides substantial benefits in the computational cost of solution. Besides, in case of the whole sphere it allows applying the same algorithms as in a doubly periodic domain on the plane and constructing finite difference schemes of arbitrary approximation order in space. Results of numerical experiments illustrate the skillfulness of the schemes in describing the shallow-water dynamics.
Bottom depth and type for shallow waters: Hyperspectral observations from a blimp
Energy Technology Data Exchange (ETDEWEB)
Lee, ZhongPing; Carder, K.; Steward, R. [Univ. of South Florida, St. Petersburg, FL (United States)] [and others
1997-08-01
In a study of a blimp transect over Tampa Bay (Florida), hyperspectral upwelling radiance over the sand and seagrass bottoms was measured. These measurements were converted to hyperspectral remote-sensing reflectances. Using a shallow-water remote-sensing-reflectance model, in-water optical properties, bottom depths and bottom albedos were derived analytically and simultaneously by an optimization procedure. In the process, curvatures of sand and seagrass albedos were used. Also used was a model of absorption spectrum of phytoplankton pigments. The derived bottom depths were compared with bathymetry charts and found to agree well. This study suggests that a low-flying blimp is a useful platform for the study and mapping of coastal water environments. The optical model as well as the data-reduction procedure used are practical for the retrieval of shallow water optical properties.
Directory of Open Access Journals (Sweden)
Brenda Lía Doti
2005-12-01
Full Text Available The shallow-water Asellota from the Beagle Channel were investigated, based on material collected at four localities in 2001-2002. A total of 3,124 asellotes were sorted, and three new species and 12 new records of distribution were reported. The Paramunnidae showed the highest species diversity and abundance (11 species and 1,463 specimens. The present research raises the number of species known from the Beagle Channel to 23; of these, 16 were previously reported from the Magellan Straits, representing 69% of similarity. Based on the present results and published data, the faunistic affinities for the shallow-water Asellota was 30% between the Magellan region and the Scotia Arc, and 26% between the Magellan region and the Antarctic Peninsula.
New records for the shallow-water chiton fauna (Mollusca, Polyplacophora of the Azores (NE Atlantic
Directory of Open Access Journals (Sweden)
Sérgio Ávila
2013-06-01
Full Text Available Published records, original data from recent field work on all of the islands of the Azores (NE Atlantic, and a revision of the entire mollusc collection deposited in the Department of Biology of the University of the Azores (DBUA were used to compile a checklist of the shallow-water Polyplacophora of the Azores. Lepidochitona cf. canariensis and Tonicella rubra are reported for the first time for this archipelago, increasing the recorded Azorean fauna to seven species.
Avila, Sérgio P; Sigwart, Julia
2013-01-01
Published records, original data from recent field work on all of the islands of the Azores (NE Atlantic), and a revision of the entire mollusc collection deposited in the Department of Biology of the University of the Azores (DBUA) were used to compile a checklist of the shallow-water Polyplacophora of the Azores. Lepidochitona cf. canariensis and Tonicella rubra are reported for the first time for this archipelago, increasing the recorded Azorean fauna to seven species.
Sérgio Ávila; Julia Sigwart
2013-01-01
Published records, original data from recent field work on all of the islands of the Azores (NE Atlantic), and a revision of the entire mollusc collection deposited in the Department of Biology of the University of the Azores (DBUA) were used to compile a checklist of the shallow-water Polyplacophora of the Azores. Lepidochitona cf. canariensis and Tonicella rubra are reported for the first time for this archipelago, increasing the recorded Azorean fauna to seven species.
New records of Ophiuroidea (Echinodermata) from shallow waters off Maceió, State of Alagoas, Brazil
Manso, Cynthia Lara de Castro; Lima, Maria Lilian F.; Correia, Monica D.; Sovierzoski, Hilda H.
2011-01-01
Aspects of the distribution and ecology of ophiuroids from shallow waters off Maceió, State of Alagoas in north-eastern Brazil were characterized. The ophiuroid fauna comprised 16 species in nine genera and seven families, including three endemic species from Brazil, Ophiocnida loveni, Ophiactis brasiliensis and Amphiura kinbergi, and also four new records for the coastal reef system off north-eastern Brazil. On coral reefs 15 species were found and Ophiothrix angulata was the most abundant s...
Biological implications of the hydrodynamics of swimming at or near the surface and in shallow water
Energy Technology Data Exchange (ETDEWEB)
Blake, R W [Department of Zoology, University of British Columbia, Vancouver, British Columbia V6T 1Z4 (Canada)], E-mail: blake@zoology.ubc.ca
2009-03-01
The origins and effects of wave drag at and near the surface and in shallow water are discussed in terms of the dispersive waves generated by streamlined technical bodies of revolution and by semi-aquatic and aquatic animals with a view to bearing on issues regarding the design and function of autonomous surface and underwater vehicles. A simple two-dimensional model based on energy flux, allowing assessment of drag and its associated wave amplitude, is applied to surface swimming in Lesser Scaup ducks and is in good agreement with measured values. It is argued that hydrodynamic limitations to swimming at speeds associated with the critical Froude number ({approx}0.5) and hull speed do not necessarily set biological limitations as most behaviours occur well below the hull speed. From a comparative standpoint, the need for studies on the hull displacement of different forms is emphasized. For forms in surface proximity, drag is a function of both Froude and Reynolds numbers. Whilst the depth dependence of wave drag is not particularly sensitive to Reynolds number, its magnitude is, with smaller and slower forms subject to relatively less drag augmentation than larger, faster forms that generate additional resistance due to ventilation and spray. A quasi-steady approach to the hydrodynamics of swimming in shallow water identifies substantial drag increases relative to the deeply submerged case at Froude numbers of about 0.9 that could limit the performance of semi-aquatic and aquatic animals and autonomous vehicles. A comparative assessment of fast-starting trout and upside down catfish shows that the energy losses of fast-starting fish are likely to be less for fish in surface proximity in deep water than for those in shallow water. Further work on unsteady swimming in both circumstances is encouraged. Finally, perspectives are offered as to how autonomous surface and underwater vehicles in surface proximity and shallow water could function to avoid prohibitive
Effects of internal waves on sound propagation in the shallow waters of the continental shelves
Ong, Ming Yi
2016-01-01
Approved for public release; distribution is unlimited Sound waves propagating through the oceans are refracted by internal waves. In the shallow waters of the continental shelves, an additional downward refraction of sound waves due to internal waves can cause them to interact more often with the seabed, resulting in additional energy from the sound waves being dissipated into the seabed. This study investigates how internal waves affect sound propagation on the continental shelves. It fi...
Directional characteristics of shallow water waves along southwestern Bay of Bengal
Digital Repository Service at National Institute of Oceanography (India)
Johnson, G.; SanilKumar, V.; Anoop, T.R.; Joseph, J.
. Effect of directional spreading and spectral bandwidth on the nonlinearity of the irregular waves, Proceedings of the Eighth International Offshore and Polar Engineering Conference, Montréal, Canada, May24-29, 1998. Sanil Kumar, V., 2006. Variation...: Ocean Eng., vol.121; 2016; 546-558 Directional characteristics of shallow water waves along southwestern Bay of Bengal Johnson Glejin, V. Sanil Kumar*, T.R.Anoop, Jofia Joseph Ocean Engineering Division, CSIR-National Institute of Oceanography...
2015-09-30
environment such as the time -varying sea surface and sloping bathymetry. The objective necessarily involves measurements from Targets and... Reverberation Experiment (TREX13) conducted in spring 2013. APPROACH Our approach revolves around the field measurement geometry we used for TREX13 which is...shown (Fig. 1) for reference. TREX13 consisted of a series of shallow water reverberation measurements made of over a 5 km long track, detailed
Remote sensing estimation of colored dissolved organic matter (CDOM) in optically shallow waters
Li, Jiwei; Yu, Qian; Tian, Yong Q.; Becker, Brian L.
2017-06-01
It is not well understood how bottom reflectance of optically shallow waters affects the algorithm performance of colored dissolved organic matters (CDOM) retrieval. This study proposes a new algorithm that considers bottom reflectance in estimating CDOM absorption from optically shallow inland or coastal waters. The field sampling was conducted during four research cruises within the Saginaw River, Kawkawlin River and Saginaw Bay of Lake Huron. A stratified field sampling campaign collected water samples, determined the depth at each sampling location and measured optical properties. The sampled CDOM absorption at 440 nm broadly ranged from 0.12 to 8.46 m-1. Field sample analysis revealed that bottom reflectance does significantly change water apparent optical properties. We developed a CDOM retrieval algorithm (Shallow water Bio-Optical Properties algorithm, SBOP) that effectively reduces uncertainty by considering bottom reflectance in shallow waters. By incorporating the bottom contribution in upwelling radiances, the SBOP algorithm was able to explain 74% of the variance of CDOM values (RMSE = 0.22 and R2 = 0.74). The bottom effect index (BEI) was introduced to efficiently separate optically shallow and optically deep waters. Based on the BEI, an adaptive approach was proposed that references the amount of bottom effect in order to identify the most suitable algorithm (optically shallow water algorithm [SBOP] or optically deep water algorithm [QAA-CDOM]) to improve CDOM estimation (RMSE = 0.22 and R2 = 0.81). Our results potentially help to advance the capability of remote sensing in monitoring carbon pools at the land-water interface.
Bathymetry Prediction in Shallow Water by the Satellite Altimetry-Derived Gravity Anomalies
Kim, Kwang Bae; Yun, Hong Sik
2017-04-01
The satellite altimetry-derived free-air gravity anomalies (SAFAGAs) are correlated with undulations of crustal density variations under the seafloor. In this study, shipborne bathymetry from the Korea Rural Community Corporation (KRC) and the SAFAGAs from Scripps Institution of Oceanography were combined to predict bathymetry in shallow water. Density contrast of 5.0 g/cm3 estimated by the check points method of the gravity-geologic method (GGM) between seawater and the seafloor topographic mass was applied to predict bathymetry in shallow water areas outside of the Saemangeum Seawall located on the southwest coast of the Korean peninsula. Bathymetry predicted by the GGM was compared with depth measurements on the shipborne locations to analyze the bathymetry accuracy. The root mean square error (RMSE) of the differences of bathymetry between GGM and KRC on the KRC shipborne tracks in shallow water around the Saemangeum Seawall is 0.55 m. The topographic effects in off-tracks extracted from SAFAGAs in the GGM can be effectively utilized to predict bathymetry by combining with shipborne depth data in shallow water where shipborne depth data are limited. In addition, bathymetry and the SAFAGAs have a linear correlation in the 20 160 km wavelength. The coherency analysis was performed by computing the cross-spectral coherence between satellite altimetry derived bathymetry and the SAFAGAs. Acknowledgement This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2016R1A6A3A11931032).
Latitudinal trends in habitat quality of shallow-water flatfish nurseries
Freitas, V.; Kooijman, S A L M; van der Veer, H.W.
2012-01-01
The habitat quality of European shallow-water nurseries was studied for 3 common flatfish species based on juvenile growth conditions. Field growth of 0-group plaice Pleuronectes platessa, flounder Platichthys flesus and sole Solea solea, from both published and unpublished studies, was compared with maximum growth predicted by a bioenergetics model based on the dynamic energy budget theory. In plaice and flounder, realized growth ratio decreased consistently during the growing season in most...
The Role of Shallow Waters in the Life Cycle of the Bahrain Penaeid Shrimps
Abdulqader, E. A. A.
1999-08-01
Tubli Bay and shallow areas south of 'Fasht Al-Adhom' are known for their importance to Bahrain penaeid shrimps. The role of these shallow waters in the Bahrain penaeid shrimp life cycle was studied in Tubli Bay. Plankton, beam and otter trawl samples were collected on a biweekly basis from May 1991 to June 1992. Otter trawl sampling was extended to June 1993. Four penaeid species were found in the area. Ranked by decreasing abundance, these species are Penaeus semisulcatus De Haan 1844, Metapenaeus stebbingi Nobili 1904, M. kutchensisGeorge, George & Rao, 1963, and P. latisulcatus Kishinouye 1896. The presence of two egg types in the plankton collection, and mature females of both M. stebbingi and M. kutchensis indicate that both species spawned in these shallow waters. Tubli Bay is an important nursery ground for both P. semisulcatus and M. stebbingi. However, this bay does not support the entire stock of P. semisulcatus. Post-spawning return migration to shallow waters is noted for P. semisulcatus. Tubli Bay is of minor importance as a nursery ground for both P. latisulcatus and M. kutchensis. Other penaeid species found in Bahrain waters are not dependent on Tubli Bay during their life cycles. These species include, Trachypenaeus curvirostris Stimpson (1860), Metapenaeopsis stridulans Alcock (1905), and M. mogiensis Rathbun (1902).
Taylor, James S., Jr.; Davis, P. S.; Wolff, Lawrence B.
2003-09-01
Research has shown that naturally occurring light outdoors and underwater is partially linearly polarized. The polarized components can be combined to form an image that describes the polarization of the light in the scene. This image is known as the degree of linear polarization (DOLP) image or partial polarization image. These naturally occurring polarization signatures can provide a diver or an unmanned underwater vehicle (UUV) with more information to detect, classify, and identify threats such as obstacles and/or mines in the shallow water environment. The SHallow water Real-time IMaging Polarimeter (SHRIMP), recently developed under sponsorship of Dr. Tom Swean at the Office of Naval Research (Code 321OE), can measure underwater partial polarization imagery. This sensor is a passive, three-channel device that simultaneously measures the three components of the Stokes vector needed to determine the partial linear polarization of the scene. The testing of this sensor has been completed and the data has been analyzed. This paper presents performance results from the field-testing and quantifies the gain provided by the partial polarization signature of targets in the Very Shallow Water (VSW) and Surf Zone (SZ) regions.
Dimitrov, D.
2012-10-01
We consider a model of elliptical stationary accretion discs developed by Lyubarskij et al. [4], which have derived a second order ordinary differential equation, describing the spatial structure of these objects. This dynamical equation contains seven integrals, arising from the azimuthal averaging along the elliptical disc particle orbits. They are functions on the unknown eccentricity distribution e(u), its derivative dot{e}(u) ≡ de(u)/du and the power n in the viscosity low η = β Σ n, where u ≡ ln p, p is the focal parameter of the concrete elliptical particle orbit. In the present paper, we derive linear relations between these unknown integrals, which may be useful to eliminate three of these quantities. It is also possible to eliminate even one more integral, but proving of this statement will be postponed in a forthcoming paper. The considered approach is maintained with a view to split the dynamical equation into a system of more simple differential equations.
National Oceanic and Atmospheric Administration, Department of Commerce — Shallow-water (generally, less than 30 meters) bank areas in the Northwestern Hawaiian Islands were identified using semi-automated image analysis of Landsat 7 ETM+...
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Lili Lei
2012-05-01
Full Text Available A hybrid nudging-ensemble Kalman filter (HNEnKF data assimilation approach, explored in the Lorenz three-variable system in Part I, is tested in a two-dimensional shallow-water model for dynamic analysis and numerical weather prediction. The HNEnKF effectively combines the advantages of the ensemble Kalman filter (EnKF and the observation nudging to achieve more gradual and continuous data assimilation by computing the nudging coefficients from the flow-dependent, time-varying error covariances of the EnKF. It can also transform the gain matrix of the EnKF into additional terms in the model's predictive equations to assist the data assimilation process. The HNEnKF is tested for both a wave case and a vortex case with different observation frequencies and observation networks. The HNEnKF generally produces smaller root mean square (RMS errors than either nudging or EnKF alone. It also has better temporal smoothness than the EnKF and lagged ensemble Kalman smoother (EnKS. The HNEnKF allows the gain matrix of the EnKF to be applied gradually in time, reducing the error spikes commonly found around the analysis times when using intermittent data assimilation methods. Therefore, the HNEnKF produces a seamless analysis with better inter-variable consistency and dynamic balance than the intermittent EnKF.
Tiffan, Kenneth F.; Connor, William P.
2012-01-01
The U.S. Army Corps of Engineers (COE) is preparing a long term management plan for sediments that affect the authorized project purposes of the Lower Granite, Little Goose, Lower Monumental, and Ice Harbor reservoirs (hereafter, the lower Snake River reservoirs), and the area from the mouth of the Snake River to Ice Harbor Dam. We conducted a study from spring 2010 through winter 2011 to describe the habitat use by juvenile Chinook salmon within a selected group of shallow water habitat complexes (deep) in the lower Snake River reservoirs to help inform the long-term plan. Natural fry and parr were present within all four shallow water habitat complexes that we studied from early spring through early summer, and parr ( = 40,345 ± 18,800 [error bound]) were more abundant than fry ( = 24,615 ± 5,701). Water deep was highly used for rearing by natural fall Chinook salmon subyearlings (fry and parr combined; hereafter natural subyearlings) based on duration of use and relative group abundances during spring and summer, whereas the 2–6 m depth interval was more highly used by migratory hatchery fall Chinook salmon subyearlings and spring, summer, and fall Chinook salmon yearlings. Overall mean spring-summer apparent density of natural subyearlings was 15.5 times higher within the use of shallow water habitat by reservoir-type juveniles was limited during our study. We only collected 38 reservoir-type juveniles in shallow water habitat sites in beach and lampara seines during the fall. Radiotelemetry data revealed that though many tagged fish passed shallow water habitat sites, relatively few fish entered them and the median time fish spent within a given site was less than 1.4 h. Fish located by mobile tracking away from study sites were pelagically oriented, and generally not found over shallow water or close to shore. The findings in this report: (1) support the selection of natural fall Chinook subyearlings as the indicator group for determining the potential
Mineralogy, early marine diagenesis, and the chemistry of shallow-water carbonate sediments
Higgins, J. A.; Blättler, C. L.; Lundstrom, E. A.; Santiago-Ramos, D. P.; Akhtar, A. A.; Crüger Ahm, A.-S.; Bialik, O.; Holmden, C.; Bradbury, H.; Murray, S. T.; Swart, P. K.
2018-01-01
Shallow-water carbonate sediments constitute the bulk of sedimentary carbonates in the geologic record and are widely used archives of Earth's chemical and climatic history. One of the main limitations in interpreting the geochemistry of ancient carbonate sediments is the potential for post-depositional diagenetic alteration. In this study, we use paired measurements of calcium (44Ca/40Ca or δ44Ca) and magnesium (26Mg/24Mg or δ26Mg) isotope ratios in sedimentary carbonates and associated pore-fluids as a tool to understand the mineralogical and diagenetic history of Neogene shallow-water carbonate sediments from the Bahamas and southwest Australia. We find that the Ca and Mg isotopic composition of bulk carbonate sediments at these sites exhibits systematic stratigraphic variability that is related to both mineralogy and early marine diagenesis. The observed variability in bulk sediment Ca isotopes is best explained by changes in the extent and style of early marine diagenesis from one where the composition of the diagenetic carbonate mineral is determined by the chemistry of the fluid (fluid-buffered) to one where the composition of the diagenetic carbonate mineral is determined by the chemistry of the precursor sediment (sediment-buffered). Our results indicate that this process, together with variations in carbonate mineralogy (aragonite, calcite, and dolomite), plays a fundamental and underappreciated role in determining the regional and global stratigraphic expressions of geochemical tracers (δ13C, δ18O, major, minor, and trace elements) in shallow-water carbonate sediments in the geologic record. Our results also provide evidence that a large shallow-water carbonate sink that is enriched in 44Ca can explain the mismatch between the δ44/40Ca value of rivers and deep-sea carbonate sediments and call into question the hypothesis that the δ44/40Ca value of seawater depends on the mineralogy of primary carbonate precipitations (e.g. 'aragonite seas' and
High-order Boussinesq-type modelling of nonlinear wave phenomena in deep and shallow water
DEFF Research Database (Denmark)
Madsen, Per A.; Fuhrman, David R.
2010-01-01
In this work, we start with a review of the development of Boussinesq theory for water waves covering the period from 1872 to date. Previous reviews have been given by Dingemans,1 Kirby,2,3 and Madsen & Schäffer.4 Next, we present our most recent high-order Boussinesq-type formulation valid...... for fully nonlinear and highly dispersive waves traveling over a rapidly varying bathymetry. Finally, we cover applications of this Boussinesq model, and we study a number of nonlinear wave phenomena in deep and shallow water. These include (1) Kinematics in highly nonlinear progressive deep-water waves; (2...
Structural elements of collapses in shallow water flows with horizontally nonuniform density
Energy Technology Data Exchange (ETDEWEB)
Goncharov, V. P., E-mail: v.goncharov@rambler.ru [Russian Academy of Sciences, Obukhov Institute of Atmospheric Physics (Russian Federation); Pavlov, V. I., E-mail: Vadim.Pavlov@univ-lille1.fr [Universite de Lille 1, UFR de Mathematiques Pures et Appliquees-LML UMR 8107 (France)
2013-10-15
The mechanisms and structural elements of instability whose evolution results in the occurrence of the collapse are studied in the scope of the rotating shallow water model with a horizontally nonuniform density. The diagram stability based on the integral collapse criterion is suggested to explain system behavior in the space of constants of motion. Analysis of the instability shows that two collapse scenarios are possible. One scenario implies anisotropic collapse during which the contact area of a collapsing drop-like fragment with the bottom contracts into a rotating segment. The other implies isotropic contraction of the area into a point.
Controlled laboratory experiments and modeling of vegetative filter strips with shallow water tables
Fox, Garey A.; Muñoz-Carpena, Rafael; Purvis, Rebecca A.
2018-01-01
Natural or planted vegetation at the edge of fields or adjacent to streams, also known as vegetative filter strips (VFS), are commonly used as an environmental mitigation practice for runoff pollution and agrochemical spray drift. The VFS position in lowlands near water bodies often implies the presence of a seasonal shallow water table (WT). In spite of its potential importance, there is limited experimental work that systematically studies the effect of shallow WTs on VFS efficacy. Previous research recently coupled a new physically based algorithm describing infiltration into soils bounded by a water table into the VFS numerical overland flow and transport model, VFSMOD, to simulate VFS dynamics under shallow WT conditions. In this study, we tested the performance of the model against laboratory mesoscale data under controlled conditions. A laboratory soil box (1.0 m wide, 2.0 m long, and 0.7 m deep) was used to simulate a VFS and quantify the influence of shallow WTs on runoff. Experiments included planted Bermuda grass on repacked silt loam and sandy loam soils. A series of experiments were performed including a free drainage case (no WT) and a static shallow water table (0.3-0.4 m below ground surface). For each soil type, this research first calibrated VFSMOD to the observed outflow hydrograph for the free drainage experiments to parameterize the soil hydraulic and vegetation parameters, and then evaluated the model based on outflow hydrographs for the shallow WT experiments. This research used several statistical metrics and a new approach based on hypothesis testing of the Nash-Sutcliffe model efficiency coefficient (NSE) to evaluate model performance. The new VFSMOD routines successfully simulated the outflow hydrographs under both free drainage and shallow WT conditions. Statistical metrics considered the model performance valid with greater than 99.5% probability across all scenarios. This research also simulated the shallow water table experiments with
Waves of pressure in viscous incompressible fluid
Prosviryakov, E. Yu.
2017-12-01
A three-dimensional non-stationary flow of a viscous incompressible fluid in the infinite space is examined. The description of possible shapes of pressure is based on the equation for the axial component of velocity, which is an exact consequence of the basic equations. New analytical exact solutions to the Navier-Stokes equations for periodic and localized traveling waves have been found.
Species Diversity of Shallow Water Zoanthids (Cnidaria: Anthozoa: Hexacorallia in Florida
Directory of Open Access Journals (Sweden)
James Davis Reimer
2012-01-01
Full Text Available Shallow water zooxanthellate zoanthids are a common component of the coral reef ecosystems of the Caribbean. Despite this, their species diversity remains poorly understood. In this study, collected Palythoa, Zoanthus, Isaurus, and Terrazoanthus specimens from the waters of Florida were phylogenetically examined to obtain a better understanding of zoanthid species diversity in the Caribbean. Surprisingly, the results from analyses utilizing three DNA markers (mitochondrial 16S ribosomal DNA, cytochrome oxidase subunit I, and the internal transcribed spacer of ribosomal DNA showed the presence of at least eleven species, of which up to four appear undescribed. Additionally, the presence of the genus Terrazoanthus in the Caribbean was confirmed for the first time. Attempts to match phylogenetic species or clades with original literature were hampered by vague and short original descriptions, and it is clear that for Atlantic Palythoa and Zoanthus species an in-depth and multidisciplinary investigation is needed to reconcile recent phylogenetic results such as in this study with traditional taxonomy. Furthermore, most shallow water zoanthid species from Florida were observed to have close, sister-species relationships with previously investigated species in the Pacific Ocean. These results indicate that many brachycnemic zoanthid species likely had a Caribbean-Pacific distribution until the formation of the Isthmus of Panama. However, due to inadvertent redescriptions, overall species diversity in these two common genera is likely much lower than literature indicates.
Benthic trophic status and nutrient fluxes in shallow-water sediments
Engelsen, Anna; Hulth, Stefan; Pihl, Leif; Sundbäck, Kristina
2008-07-01
Proliferation of fast-growing ephemeral macroalgae in shallow-water embayments constitutes a large-scale environmental change of coastal marine ecosystems. Since inorganic nutrients essential for the initiation and maintenance of macroalgal growth may be supplied from the underlying sediment, we investigated the coupling between benthic inorganic nutrient (mainly N and P) fluxes and sediment properties in 6 bays representing a wide gradient of sediment characteristics (grain size, organic matter content, solid phase C and N). The initial characterization of bays was made in June and also included measurements of oxygen flux and microphytobenthic and macrofaunal biomass. In September, still within the growth season of the macroalgae, complementary experiments with sediment-water incubations for benthic flux measurements of oxygen and nutrients focused on trophic status (balance between auto- and heterotrophy) as a controlling factor for rates of measured benthic nutrient fluxes. Generally, sediments rendered autotrophic by microphytobenthic photosynthesis removed nutrients from the overlying water, while heterotrophic sediments supplied nutrients to the overlying bottom water. Estimations of the green-algal nutrient demand suggested that late in the growth season, net heterotrophic sediments could cover 20% of the N-demand and 70% of the P demand. As the benthic trophic status is a functional variable more closely coupled to nutrient fluxes than the comparably conservative structural parameter organic matter content, we suggest that the trophic status is a more viable parameter to classify sediments and predict benthic nutrient fluxes in shallow-water environments.
Cruise observation of shallow water response to typhoon Damrey 2012 in the Yellow Sea
Yang, Guang-Bing; Lü, Lian-Gang; Zhuang, Zhan-Peng; Xiong, Xue-Jun; Wang, Guan-Suo; Guo, Yan-Liang; Yu, Long; Ma, De-Jing
2017-09-01
Typhoon Damrey 2012 has been the strongest typhoon to strike the area north of the Yangtze River since 1949. Two cruise observations to examine the shallow water response to typhoon were carried out just before and after the passage of Damrey in the shallow water near the Jiaozhou Bay on 1 and 5 August 2012. The observation results indicate that, after the passage of Damrey, the thermocline was deepened and weakened significantly. The water temperature below the surface increased by about 4-10 °C. A significant temperature gradient was generated at the bottom of the water column. The salinity decreased throughout the water column. The surface heat flux and precipitation data indicate that the temperature increase and salinity decrease of the bottom water were mainly caused by the intrusion of warm, low-salinity water from the surface (depth salinity surface water was driven by wind and flowed onshore, accumulated and sank as it encountered the coast, which forced the cold bottom water of the Yellow Sea Cold Water Mass (YSCWM) to flow offshore.
Directory of Open Access Journals (Sweden)
Benny Kwok Kan Chan
Full Text Available Hydrothermal vents represent a unique habitat in the marine ecosystem characterized with high water temperature and toxic acidic chemistry. Vents are distributed at depths ranging from a few meters to several thousand meters. The biological communities of shallow-water vents have, however, been insufficiently studied in most biogeographic areas. We attempted to characterize the macrofauna and macroflora community inhabiting the shallow-water vents off Kueishan Island, Taiwan, to identify the main abiotic factors shaping the community structure and the species distribution. We determined that positively buoyant vent fluid exhibits a more pronounced negative impact to species on the surface water than on the bottom layer. Species richness increased with horizontal distance from the vent, and continuing for a distance of 2000 m, indicating that the vent fluid may exert a negative impact over several kilometers. The community structure off Kueishan Island displayed numerous transitions along the horizontal gradient, which were broadly congruent with changes in environmental conditions. Combination of variation in Ca2+, Cl-, temperature, pH and depth were revealed to show the strongest correlation with the change in benthic community structure, suggesting multiple factors of vent fluid were influencing the associated fauna. Only the vent crabs of Kueishan Island may have an obligated relationship with vents and inhabit the vent mouths because other fauna found nearby are opportunistic taxa that are more tolerant to acidic and toxic environments.
Tools to Perform Local Dense 3D Reconstruction of Shallow Water Seabed
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Loïca Avanthey
2016-05-01
Full Text Available Tasks such as distinguishing or identifying individual objects of interest require the production of dense local clouds at the scale of these individual objects of interest. Due to the physical and dynamic properties of an underwater environment, the usual dense matching algorithms must be rethought in order to be adaptive. These properties also imply that the scene must be observed at close range. Classic robotized acquisition systems are oversized for local studies in shallow water while the systematic acquisition of data is not guaranteed with divers. We address these two major issues through a multidisciplinary approach. To efficiently acquire on-demand stereoscopic pairs using simple logistics in small areas of shallow water, we devised an agile light-weight dedicated system which is easy to reproduce. To densely match two views in a reliable way, we devised a reconstruction algorithm that automatically accounts for the dynamics, variability and light absorption of the underwater environment. Field experiments in the Mediterranean Sea were used to assess the results.
Shallow water benthic imaging and substrate characterization using recreational-grade sidescan-sonar
Buscombe, Daniel D.
2017-01-01
In recent years, lightweight, inexpensive, vessel-mounted ‘recreational grade’ sonar systems have rapidly grown in popularity among aquatic scientists, for swath imaging of benthic substrates. To promote an ongoing ‘democratization’ of acoustical imaging of shallow water environments, methods to carry out geometric and radiometric correction and georectification of sonar echograms are presented, based on simplified models for sonar-target geometry and acoustic backscattering and attenuation in shallow water. Procedures are described for automated removal of the acoustic shadows, identification of bed-water interface for situations when the water is too turbid or turbulent for reliable depth echosounding, and for automated bed substrate classification based on singlebeam full-waveform analysis. These methods are encoded in an open-source and freely-available software package, which should further facilitate use of recreational-grade sidescan sonar, in a fully automated and objective manner. The sequential correction, mapping, and analysis steps are demonstrated using a data set from a shallow freshwater environment.
Unknown object localization and identification in shallow water environment at Lake Balaton
Kiss, Balint; Bostater, Charles R., Jr.; Vajda, Ferenc; Vajta, Laszlo; Vogel, Miklos
2004-11-01
This paper addresses a particular detection problem related to the largest freshwater lake of Central and Western Europe, namely the Lake Balaton. The bed-silt of this shallow water lake (its average depth is 3.3 meters) contains several type of objects: industrial debris, historical vestiges, and in particular, an unknown quantity of unexploded ordnance from the second World War. It is important to localize and classify these objects for precise risk assessment and eventual later removal (not addressed in the paper). The bed-silt of the lake can be characterized as a mud having a light and constantly changing structure. It follows that the shallow water is almost always mixed with the mud. This admixture is constantly maintained by winds and navigating boats, hence the underwater visibility is close to zero during the most part of the year, especially in the depth range close to the bottom. Since the climate makes it possible, the authors propose a special way to explore the bed-silt of the lake, namely the use an autonomous vehicle on the frozen lake. Note that the ice prevents the wind and navigating boats to generate water movement and thus the mud is sedimented. This autonomous vehicle is equipped with a GPS based onboard localization system, with multiple sensor and recording equipment, and with a radio link to its command post. More details about the nature of objects to be detected as well as about the architecture of the detection and localization system are presented in the paper.
Li, Zhenglin; Zhang, Renhe; Li, Fenghua
2010-09-01
Ocean reverberation in shallow water is often the predominant background interference in active sonar applications. It is still an open problem in underwater acoustics. In recent years, an oscillation phenomenon of the reverberation intensity, due to the interference of the normal modes, has been observed in many experiments. A coherent reverberation theory has been developed and used to explain this oscillation phenomenon [F. Li et al., Journal of Sound and Vibration, 252(3), 457-468, 2002]. However, the published coherent reverberation theory is for the range independent environment. Following the derivations by F. Li and Ellis [D. D. Ellis, J. Acoust. Soc. Am., 97(5), 2804-2814, 1995], a general reverberation model based on the adiabatic normal mode theory in a range dependent shallow water environment is presented. From this theory the coherent or incoherent reverberation field caused by sediment inhomogeneity and surface roughness can be predicted. Observations of reverberation from the 2001 Asian Sea International Acoustic Experiment (ASIAEX) in the East China Sea are used to test the model. Model/data comparison shows that the coherent reverberation model can predict the experimental oscillation phenomenon of reverberation intensity and the vertical correlation of reverberation very well.
Effects of once-weekly shallow water aerobic exercise on functional performance in elderly women
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Veronika Kramperová
2016-12-01
Full Text Available The purpose of this study was to examine the effects of 24-week shallow-water aerobic exercise on functional performance in postmenopausal women. Thirty-seven women aged 60+ (mean age 67.2 ± 4.8 years were self-selected to a water exercise group (n = 21 or to a comparison group (n = 16. The training consisted of a 24-week (60 min.day−1, 1 d.wk−1 supervised and guided exercise programme that included aerobic and strength training using an aquatic noodle in shallow water (1.2 m. Outcome measures were 30-s chair stand and 30-s arm curl tests, assessed at baseline and 24 weeks. Significant differences between groups were analyzed using Fisher’s exact test. At 24 weeks there was a significantly (p < 0.05 greater improvement in measure of upper-body strength in the water exercise group. Arm curling improved by 15.8 versus 14.3% in the water exercise and comparison groups, respectively.
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ARIF MOHAMMAD SIDDIQ
2016-04-01
Full Text Available Abstract. Siddiq AM, Atmowidi T, Qayim I. 2015. The diversity and distribution of Holothuroidea in shallow waters of Baluran National Park, Indonesia. Biodiversitas 17: 55-60. A study of the diversity and distribution of sea cucumber (Holothuroidea in shallow waters at Baluran National Park, East Java, Indonesia was carried out from July until September 2015. The method used in this study was systematic transect in low tide condition. Samples were collected by hands at intertidal sites. Identification of sea cucumber species based on morphological ossicles. Twenty one species of Holothuroidea belonging two orders and four families were found in this study. The most dominant family found was Holothuriidae (16 species, followed by Stichopodidae (2 species, Synaptidae (2 species, and Chiridotidae (1 spesies. Four species (Holothuria olivacea, H. verrucosa, Labidodemas rugosum, and Chiridota smirnovi are new record for Java waters and one species (H. papillifera is a new record for Indonesian waters. Two morphospecies (H. aff. macroperona and Stichopus cf. monotuberculatus need reconfirmation to species level. The highest abundance species of Holothuroidea was found at under rock with 15 species. Whereas, the highest number of individuals was found in seagrass areas with 5457 individuals. H. atra has extensive habitat distribution, such as seagrass, macroalgae, coral reef, dead coral, sand, and under rock.
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Alejandro Acevedo-Malavé
2013-06-01
Full Text Available Smoothed Particle Hydrodynamics (SPH is a Lagrangian mesh-free formalism and has been useful to model continuous fluid. This formalism is employed to resolve the Navier-Stokes equations by replacing the fluid with a set of particles. These particles are interpolation points from which properties of the fluid can be determined. In this study, the SPH method is applied to simulate the multiple hydrodynamics collisions and the formation of clusters of equally sized liquid drops in three-dimensional space. Ranges of value for the collision velocity droplets are chosen, giving rise to different results for the collision: fragmentation and formation of clusters of liquid drops. The velocity vector fields formed inside the drops during the collision process are shown.
Shallow-Water Piscivore-Prey Dynamics in California's Sacramento–San Joaquin Delta
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Matthew L. Nobriga
2007-05-01
Full Text Available Predation is one mechanism that could lead to low native fish abundance in macrophyte dominated shallow-water habitats in the Sacramento-San Joaquin Delta. We used beach seine and gill net sampling to identify and compare the distribution and feeding ecology of three piscivores (striped bass, Morone saxatilis, largemouth bass, Micropterus salmoides, and Sacramento pikeminnow, Ptychocheilus grandis at five nearshore sites in the Sacramento-San Joaquin Delta. Sampling was conducted March-October 2001 and 2003. We addressed the following questions. What are the spatial and temporal distributions of age-1 and older striped bass, largemouth bass, and Sacramento pikeminnow? What prey are eaten by these predators? What is the relative importance of predator size versus seasonal prey availability on incidence of piscivory for these predators? What is the likely per capita impact of each piscivore on prey fishes, particularly native fishes? All 76 of our individual station visits yielded at least one of the three species, suggesting that piscivorous fishes frequently occur in Delta shallow-water habitats. All three piscivores had diverse diets.There were noticeable seasonal shifts in prey fish for each of the three piscivores. In general, most native fish were consumed during spring (March-May and the highest prey species richness occurred during summer (June-August. Largemouth bass likely have the highest per capita impact on nearshore fishes, including native fishes. Largemouth bass preyed on a greater diversity of native fishes than the other two piscivores and consumed native fishes farther into the season (July versus May. Based on binomial generalized additive models, incidence of piscivory was predominantly a function of size for largemouth bass and Sacramento pikeminnow. Largemouth bass became predominantly piscivorous at smaller sizes than Sacramento pikeminnow; about 115 mm versus about 190 mm respectively. In contrast, incidence of piscivory
Nagle, Elizabeth F; Sanders, Mary E; Shafer, Alex; Barone Gibbs, Bethany; Nagle, Jacquelyn A; Deldin, Anthony R; Franklin, Barry A; Robertson, Robert J
2013-09-01
Aquatic exercise (AE) is a popular form of physical activity, yet few studies have assessed the individual's energy expenditure (EE) associated with a continuous bout of AE. Studies using indirect calorimetry to measure EE have reported limitations associated with test methodology and the ability to control individual's exercise intensity or tempo. To evaluate EE and cardiorespiratory (CR) responses during a 40-minute shallow-water AE session in young adult women. Twenty-one healthy women (aged 21.7 ± 3.4 years) completed an orientation practice session and a 40-minute shallow-water AE session using a traditional exercise class format and the SWEAT video-based instructional cuing program. The high-intensity interval format included the following segments: 1) warm-up (3 minutes); 2) CR segment ( 22 minutes); 3) muscular endurance segment (ME; 10 minutes); and 4) cool-down (5 minutes). Subject oxygen consumption (VO2; mL/kg/min), heart rate (HR) and OMNI overall ratings of perceived exertion (RPE-O) were assessed each minute. Average kcal/min1, metabolic equivalents (METs; 1 MET = 3.5 mL/kg/min), and total kcals per segment and for the overall session were calculated. The total subject EE throughout the 40-minute trial (including warm-up and cool-down segments) was 264 kcals, with an overall average of 6.3 kcals/min (5.6 METs).The average kcals/min expended throughout CR segments 2 through 6 was 8.05 (7.1 METs), with the Hoverjog segment producing the greatest average kcals/min at 8.3 (7.3 METs). The CR portion (22 min) contributed 65% of the total EE (171 kcals) of the 40-minute AE trial. For the overall AE trial, the highest and average subject VO2 achieved were 33.3 and 19.7 mL/kg/min, respectively. The average highest subject heart rate achieved was 177 beats per minute (bpm), equivalent to 90% of the participant's age-predicted HRmax. Energy expenditure during a 40-minute AE session met national recommendations for a daily moderate-to-vigorous bout of physical
On the errors of spectral shallow-water limited-area model simulations using an extension technique
Energy Technology Data Exchange (ETDEWEB)
Simmel, M.; Harlander, U. [Leipzig Univ. (Germany). Inst. fuer Meteorologie (LIM)
1999-08-01
Although the spectral technique is frequently used for the horizontal discretization in global atmospheric models, it is not common in limited area models (LAMs) because of the nonperiodic boundary conditions. We apply the Haugen-Machenhauer extension technique to a regional three-layer shallow-water model based on double Fourier series. The method extends the time-dependent boundary fields into a zone outside the integration area in a way that periodic fields are obtained. The boundary fields necessary for the regional model simulations are calculated in advance by a global simulation performed. In contrast to other studies, we use exactly the same numerical model for the global and the regional simulation, respectively. The only difference between these simulations is the model domain. Therefore, a relatively objective measure for errors associated with the extension technique can be obtained. First, we compare an analytic stationary nonlinear and nonperiodic solution of the governing model equations with the spectral LAM solution. Secondly, we compare the time evolution of pressure and flow structures during a westerly flow across an asymmetric large-scale topography in the global and regional model domains. Both simulations show a good agreement between the regional and the global solutions. The rms-errors amount to about 2 m for the layer heights and 0.2 m s{sup -1} for the velocity components in the mountain flow case after a 48 h integration period. Finally, we repeat this simulation with models based on 2nd and 4th order finite differences, respectively, and compare the errors of the spectral model version with the errors of the grid point versions. We demonstrate that the high accuracy of global spectral methods can also be realized in the regional model by using the Haugen-Machenhauer extension technique. (orig.) 21 refs.
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Daniel eWagner
2015-05-01
Full Text Available The shallow-water (<150 m antipatharian fauna of the Hawaiian Archipelago is described and illustrated based on a systematic examination of skeletal spine morphology, polyp morphology, colony branching pattern and in situ photographs. A total of 172 black coral specimens were examined, including all available type material of species previously reported from shallow waters off Hawaiʻi. The examined specimens were assigned to three families (Antipathidae, Aphanipathidae and Myriopathidae, six genera (Antipathes, Cirrhipathes, Stichopathes, Aphanipathes, Acanthopathes and Myriopathes, and eight species: Antipathes griggi Opresko, 2009, Antipathes grandis Verrill, 1928, Cirrhipathes cf. anguina (Dana, 1846, Stichopathes echinulata Brook, 1889, Stichopathes? sp., Aphanipathes verticillata mauiensis Opresko et al., 2012, Acanthopathes undulata (Van Pesch 1914 andMyriopathes cf. ulex (Ellis and Solander 1786. The biogeographical distribution of Hawaiian shallow-water black corals is presented and discussed.
Hadanny, Amir; Tal, Sigal; Fishlev, Gregori; Bechor, Yair; Efrati, Shai
2015-06-01
A 22-year-old diver presented to our emergency room complaining of headaches and left side numbness three days after diving to a depth of 6 metres for 25 minutes. On examination, he had left-sided hypaesthesia, and a post-contrast FLAIR brain MRI sequence revealed signiﬁcant diffuse meningeal enhancement, indicating blood-brain-barrier (BBB) disruption. The patient was treated with hyperbaric oxygen; the initial four sessions resulted in only partial symptom improvement correlating with partial improvement in the MRI ﬁndings. Ten additional hyperbaric treatments resulted in complete resolution of the symptoms and normalization of MRI ﬁndings. The main aim of this case report is to present a probable, atypical, delayed-onset case of shallow-water decompression sickness culminating in signiﬁcant BBB damage, which was demonstrated by special MRI techniques.
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Alper Bereketli
2015-01-01
Full Text Available We study the performances of several computationally efficient and simple techniques for estimating direction of arrival (DOA of an underwater acoustic source using a single acoustic vector sensor (AVS in shallow water. Underwater AVS is a compact device, which consists of one hydrophone and three accelerometers in a packaged form, measuring scalar pressure and three-dimensional acceleration simultaneously at a single position. A very controlled experimental setup is prepared to test how well-known techniques, namely, arctan-based, intensity-based, time domain beamforming, and frequency domain beamforming methods, perform in estimating DOA of a source in different circumstances. Experimental results reveal that for almost all cases beamforming techniques perform best. Moreover, arctan-based method, which is the simplest of all, provides satisfactory results for practical purposes.
Thermal adaptations in deep-sea hydrothermal vent and shallow-water shrimp
Smith, Felix; Brown, Alastair; Mestre, Nélia C.; Reed, Adam J.; Thatje, Sven
2013-08-01
The hydrothermal vent shrimp Mirocaris fortunata is commonly exposed to acute thermal gradients and rapid fluctuations in water temperature. The shallow-water shrimp Palaemonetes varians experiences less acute but similar magnitude fluctuations in its thermal regime. Acute respiratory response to temperature shock, and temperature preference was assessed for both species. Oxygen consumption rates were assessed across the natural temperature range reported for M. fortunata. Rates increased with temperature for both species. P. varians had a significantly higher rate of oxygen consumption than M. fortunata at all temperatures except 4 °C. The rate of increase in oxygen consumption with increasing temperature was also significantly greater for P. varians. M. fortunata selected a significantly higher temperature than P. varians. Mirocaris fortunata maintains its metabolism at a more stable rate, which is likely an adaptation to acute changes in temperatures occurring at hydrothermal vents.
Novel Slope Source Term Treatment for Preservation of Quiescent Steady States in Shallow Water Flows
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Khawar Rehman
2016-10-01
Full Text Available This paper proposes a robust method for modeling shallow-water flows and near shore tsunami propagation, applicable for both simple and complex geometries with uneven beds. The novel aspect of the model includes the introduction of a new method for slope source terms treatment to preserve quiescent equilibrium over uneven topographies, applicable to both structured and unstructured mesh systems with equal accuracy. Our model is based on the Godunov-type finite volume numerical approximation. Second-order spatial and temporal accuracy is achieved through high resolution gradient reconstruction and the predictor-corrector method, respectively. The approximate Riemann solver of Harten, Lax, and van Leer with contact wave restoration (HLLC is used to compute fluxes. Comparisons of the model’s results with analytical, experimental, and published numerical solutions show that the proposed method is capable of accurately predicting experimental and real-time tsunami propagation/inundation, and dam-break flows over varying topographies.
Molecular phylogeny of the benthic shallow-water octopuses (Cephalopoda: Octopodinae).
Guzik, Michelle T; Norman, Mark D; Crozier, Ross H
2005-10-01
Octopus has been regarded as a "catch all" genus, yet its monophyly is questionable and has been untested. We inferred a broad-scale phylogeny of the benthic shallow-water octopuses (subfamily Octopodinae) using amino acid sequences of two mitochondrial DNA genes: Cytochrome oxidase subunit III and Cytochrome b apoenzyme, and the nuclear DNA gene Elongation Factor-1alpha. Sequence data were obtained from 26 Octopus species and from four related genera. Maximum likelihood and Bayesian approaches were implemented to estimate the phylogeny, and non-parametric bootstrapping was used to verify confidence for Bayesian topologies. Phylogenetic relationships between closely related species were generally well resolved, and groups delineated, but the genes did not resolve deep divergences well. The phylogenies indicated strongly that Octopus is not monophyletic, but several monophyletic groups were identified within the genus. It is therefore clear that octopodid systematics requires major revision.
Stability Analysis of Numerical Methods for a 1.5-Layer Shallow-Water Ocean Model
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Guang-an Zou
2013-01-01
Full Text Available A 1.5-layer reduced-gravity shallow-water ocean model in spherical coordinates is described and discretized in a staggered grid (standard Arakawa C-grid with the forward-time central-space (FTCS method and the Leap-frog finite difference scheme. The discrete Fourier analysis method combined with the Gershgorin circle theorem is used to study the stability of these two finite difference numerical models. A series of necessary conditions of selection criteria for the time-space step sizes and model parameters are obtained. It is showed that these stability conditions are more accurate than the Courant-Friedrichs-Lewy (CFL condition and other two criterions (Blumberg and Mellor, 1987; Casulli, 1990, 1992. Numerical experiments are proposed to test our stability results, and numerical model that is designed is also used to simulate the ocean current.
Deslauriers, David; Heironimus, Laura B.; Chipps, Steven R.
2016-01-01
We evaluated temperature tolerance in age-0 pallid and shovelnose sturgeon (Scaphirhynchus albus and Scaphirhynchus platorynchus), two species that occur sympatrically in the Missouri and Mississippi Rivers. Fish (0.04–18 g) were acclimated to water temperatures of 13, 18 or 24 °C to quantify temperatures associated with lethal thermal maxima (LTM). The results show that no difference in thermal tolerance existed between the two sturgeon species, but that LTM was significantly related to body mass and acclimation temperature. Multiple linear regression analysis was used to estimate LTM, and outputs from the model were compared with water temperatures measured in the shallow water habitat (SWH) of the Missouri River. Observed SWH temperatures were not found to yield LTM conditions. The model developed here is to serve as a general guideline in the development of future SWH.
A Kalman filter for a two-dimensional shallow-water model
Parrish, D. F.; Cohn, S. E.
1985-01-01
A two-dimensional Kalman filter is described for data assimilation for making weather forecasts. The filter is regarded as superior to the optimal interpolation method because the filter determines the forecast error covariance matrix exactly instead of using an approximation. A generalized time step is defined which includes expressions for one time step of the forecast model, the error covariance matrix, the gain matrix, and the evolution of the covariance matrix. Subsequent time steps are achieved by quantifying the forecast variables or employing a linear extrapolation from a current variable set, assuming the forecast dynamics are linear. Calculations for the evolution of the error covariance matrix are banded, i.e., are performed only with the elements significantly different from zero. Experimental results are provided from an application of the filter to a shallow-water simulation covering a 6000 x 6000 km grid.
A note on relative equilibria in a rotating shallow water layer
Ait Abderrahmane, Hamid
2013-05-08
Relative equilibria of two and three satellite vortices in a rotating shallow water layer have been recorded via particle image velocimetry (PIV) and their autorotation speed was estimated. This study shows that these equilibria retain the fundamental characteristics of Kelvin\\'s equilibria, and could be adequately described by the classical idealized point vortex theory. The same conclusion can also be inferred using the experimental dataset of Bergmann etÂ al.Â (J.Â FluidÂ Mech., vol. 679, 2011, pp. 415-431; J. Fluid Mech., vol. 691, 2012, pp. 605-606) if the assigned field\\'s contribution to pattern rotation is included. © 2013 Cambridge University Press.
A local time stepping algorithm for GPU-accelerated 2D shallow water models
Dazzi, Susanna; Vacondio, Renato; Dal Palù, Alessandro; Mignosa, Paolo
2018-01-01
In the simulation of flooding events, mesh refinement is often required to capture local bathymetric features and/or to detail areas of interest; however, if an explicit finite volume scheme is adopted, the presence of small cells in the domain can restrict the allowable time step due to the stability condition, thus reducing the computational efficiency. With the aim of overcoming this problem, the paper proposes the application of a Local Time Stepping (LTS) strategy to a GPU-accelerated 2D shallow water numerical model able to handle non-uniform structured meshes. The algorithm is specifically designed to exploit the computational capability of GPUs, minimizing the overheads associated with the LTS implementation. The results of theoretical and field-scale test cases show that the LTS model guarantees appreciable reductions in the execution time compared to the traditional Global Time Stepping strategy, without compromising the solution accuracy.
Probing the thermal character of analogue Hawking radiation for shallow water waves?
Michel, Florent
2014-01-01
We numerically compute the scattering coefficients of shallow water waves blocked by a stationary counterflow. When the flow is transcritical, these coefficients closely follow Hawking's prediction according to which black holes should emit a thermal spectrum. We then study how the spectrum deviates from thermality when reducing the maximal flow velocity, with a particular attention to subcritical flows since these have been recently used to test Hawking's prediction. For low frequencies, we show, first, that the scattering coefficients are dominated by hydrodynamical channels and, second, that the Planckianity of the spectrum is completely lost. Our numerical results reproduce rather well the observations made by S. Weinfurtner et al. in the Vancouver experiment. Nevertheless, we propose a new interpretation of what has been observed, as well as new experimental tests to validate our findings.
Mapping nonlinear shallow-water tides: a look at the past and future
DEFF Research Database (Denmark)
Andersen, Ole Baltazar; Egbert, G.D.; Erofeeva, S.Y.
2006-01-01
Overtides and compound tides are generated by nonlinear mechanisms operative primarily in shallow waters. Their presence complicates tidal analysis owing to the multitude of new constituents and their possible frequency overlap with astronomical tides. The science of nonlinear tides was greatly...... advanced by the pioneering researches of Christian Le Provost who employed analytical theory, physical modeling, and numerical modeling in many extensive studies, especially of the tides of the English Channel. Le Provost's complementary work with satellite altimetry motivates our attempts to merge...... these two interests. After a brief review, we describe initial steps toward the assimilation of altimetry into models of nonlinear tides via generalized inverse methods. A series of barotropic inverse solutions is computed for the M-4 tide over the northwest European Shelf. Future applications of altimetry...
Multimission empirical ocean tide modeling for shallow waters and polar seas
DEFF Research Database (Denmark)
Cheng, Yongcun; Andersen, Ole Baltazar
2011-01-01
A new global ocean tide model named DTU10 (developed at Technical University of Denmark) representing all major diurnal and semidiurnal tidal constituents is proposed based on an empirical correction to the global tide model FES2004 (Finite Element Solutions), with residual tides determined using...... to recover twice the spatial variations of the tidal signal which is particularly important in shallow waters where the spatial scale of the tidal signal is scaled down. Outside the +/- 66 degrees parallel combined Envisat, GEOSAT Follow-On, and ERS-2, data sets have been included to solve for the tides up...... to the +/- 82 degrees parallel. A new approach to removing the annual sea level variations prior to estimating the residual tides significantly improved tidal determination of diurnal constituents from the Sun-synchronous satellites (e. g., ERS-2 and Envisat) in the polar seas. Extensive evaluations with six...
Barkman, A.; Wagner, D.
2016-02-01
Mesophotic Reef Ecosystems (MCEs) are predicted to be an important refuge for shallow-water species in response to climate change. This has led to an increasing amount of research on MCEs in recent years. The Papahānaumokuākea Marine National Monument (PMNM) surrounding the Northwestern Hawaiian Islands (NWHI) represents one of the largest marine protected areas in the world. There has been an increased emphasis on characterizing the biodiversity of the NWHI since the establishment of the PMNM in 2006. The fauna of this remote region has previously been surveyed extensively in shallow-water depths (200 m) through the use of trawling, manned submersibles, and remotely operated vehicles. However, little is known about the MCEs found in the intermediate depth ranges. Since 2009, annual research expeditions have surveyed the biodiversity of MCEs within the PMNM using mixed-gas technical diving. Coral Point Count software was used to analyze photoquadrat images taken at shallow-water reefs and MCEs along transects near Midway Atoll, Lisianski Island, Pearl and Hermes Atoll, and French Frigate Shoals. A multivariate analysis of these communities showed a spatial segregation between shallow-water and mesophotic reefs. There was a significantly higher percentage of coral cover at shallow water reefs than mesophotic reefs (p=<0.0024). There was also a significantly higher cover of green, red, and brown macroalgae at MCEs than shallow-water reefs (p<0.01, p<0.0023, p<0.0004). It is important to understand the composition of these ecosystems in order to predict their role in the changing ocean.
Quantitative Diagnostics of Mixing in a Shallow Water Model of the Stratosphere.
Sobel, Adam H.; Plumb, R. Alan
1999-08-01
Two different approaches are applied to quantify mixing in a shallow water model of the stratosphere. These are modified Lagrangian mean (MLM) theory and a technique referred to as `reverse domain filling with local gradient reversal' (RDF-LGR). The latter is similar to a previously existing technique using contour advection and contour surgery.It is first proved that in an inviscid shallow water atmosphere subject to mass sources and sinks, if the mass enclosed by a potential vorticity (PV) contour is steady in time, then the integral of the mass source over the area enclosed by the contour must be zero. Next, the MLM and RDF-LGR approaches are used to diagnose the time-averaged transport across PV contours in the model simulations.The model includes a sixth-order hyperdiffusion on the vorticity field. Except in a thin outer `entrainment zone,' the hyperdiffusion term has only a very weak effect on the MLM mass budget of the polar vortex. In the entrainment zone, the hyperdiffusion term has a significant effect. The RDF-LGR results capture this behavior, providing good quantitative estimates of the hyperdiffusion term, which is equivalent to the degree of radiative disequilibrium at a PV contour. This agreement shows that the main role of the hyperdiffusion is to `mop up' the filaments that are produced by the essentially inviscid large-scale dynamics. All calculations are repeated for two values of the hyperdiffusion coefficient that differ by a factor of 50, with little difference in the results. This suggests that the amount of material entrained from the vortex edge into the surf zone does not depend on the details of the small-scale dissipation, as long as it is sufficiently weak and has some degree of scale selectivity.
AIRBORNE LASER BATHYMETRY FOR DOCUMENTATION OF SUBMERGED ARCHAEOLOGICAL SITES IN SHALLOW WATER
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M. Doneus
2015-04-01
Full Text Available Knowledge of underwater topography is essential to the understanding of the organisation and distribution of archaeological sites along and in water bodies. Special attention has to be paid to intertidal and inshore zones where, due to sea-level rise, coastlines have changed and many former coastal sites are now submerged in shallow water. Mapping the detailed inshore topography is therefore important to reconstruct former coastlines, identify sunken archaeological structures and locate potential former harbour sites. However, until recently archaeology has lacked suitable methods to provide the required topographical data of shallow underwater bodies. Our research shows that airborne topo-bathymetric laser scanner systems are able to measure surfaces above and below the water table over large areas in high detail using very short and narrow green laser pulses, even revealing sunken archaeological structures in shallow water. Using an airborne laser scanner operating at a wavelength in the green visible spectrum (532 nm two case study areas in different environmental settings (Kolone, Croatia, with clear sea water; Lake Keutschach, Austria, with turbid water were scanned. In both cases, a digital model of the underwater topography with a planimetric resolution of a few decimeters was measured. While in the clear waters of Kolone penetration depth was up to 11 meters, turbid Lake Keutschach allowed only to document the upper 1.6 meters of its underwater topography. Our results demonstrate the potential of this technique to map submerged archaeological structures over large areas in high detail providing the possibility for systematic, large scale archaeological investigation of this environment.
Higgins, J. A.; Blättler, C. L.; Swart, P. K.; Santiago Ramos, D. P.; Akhtar, A.
2016-12-01
The geochemistry of shallow water carbonate sediments has been used to reconstruct the temperature and isotopic composition of seawater as well as the global carbon and oxygen cycles over >3 billion years of Earth history. An underlying and heavily debated assumption in most studies utilizing the chemistry of carbonate minerals is that the chemical composition of the sample accurately preserves a record of the fluid from which it precipitated. Diagenetic or post-depositional alteration of the geochemistry by either meteoric or marine fluids is a widespread phenomenon in modern and recent shallow and deep-sea carbonate sediments. Diagenetic alteration is observed at all scales, from micron, to thin section, to stratigraphic units, making it difficult to quantify its effects on the geochemistry of carbonate sediments in the geologic record. Here we explore the possibility of using the Ca isotopic composition of sedimentary carbonates as a diageneitc tool using a large data set of Neogene carbonate sediments and associated pore fluids from the Bahamas. We find that the δ44/40Ca values of bulk carbonate sediments at these sites exhibits systematic stratigraphic variability that is related to both mineralogy and diagenesis (marine and meteoric). The observed variability in bulk sediment Ca isotopes requires large-scale fluid-dominated early marine diagenesis in significant water depths (up to 650 mbsl) and suggests that fluid-dominated early marine diagenesis plays a fundamental role in determining the geochemistry (δ13C, δ18O, and trace elements) of shallow water carbonate sediments in the geologic record.
Roy-Leveillee, Pascale; Burn, Christopher R.
2017-05-01
It is generally assumed that permafrost is preserved beneath shallow lakes and ponds in the Western North American Arctic where water depth is less than about two thirds of the late-winter lake ice thickness. Here we present field observations of talik development beneath water as shallow as 0.2 m despite a lake ice thickness of 1.5 m, in Old Crow Flats (OCF), YT. Conditions leading to the initiation and development of taliks beneath shallow water were investigated with field measurements of shore erosion rates, bathymetry, ice thickness, snow accumulation, and lake bottom temperature near the shores of two expanding lakes in OCF. The sensitivity of talik development to variations in lake bottom thermal regime was then investigated numerically. Where ice reached the lake bottom, talik development was controlled by the ratio of freezing degree days to thawing degree days at the lake bottom (FDDlb/TDDlb). In some cases, spatial variations in on-ice snow depth had a minimal effect on annual mean lake bottom temperature (Tlb) but caused sufficient variations in FDDlb/TDDlb to influence talik development. Where Tlb was close to but greater than 0°C simulations indicated that the thermal offset allowed permafrost aggradation to occur under certain conditions, resulting in irregular near-shore talik geometries. The results highlight the sensitivity of permafrost to small changes in lake bottom thermal conditions where the water column freezes through in early winter and indicate the occurrence of permafrost degradation beneath very shallow water in the near-shore zone of Arctic ponds and lakes.
Reuter, Markus; Piller, Werner E; Brandano, Marco; Harzhauser, Mathias
2013-12-01
Shallow-marine sediment records have the strong potential to display sensitive environmental changes in sedimentary geometries and skeletal content. However, the time resolution of most neritic carbonate records is not high enough to be compared with climatic events as recorded in the deep-sea sediment archives. In order to resolve the paleoceanographic and paleoclimatic changes during the Oligocene-Miocene transition in the Mediterranean shallow water carbonate systems with the best possible time resolution, we re-evaluated the Decontra section on the Maiella Platform (central Apennines, Italy), which acts as a reference for the correlation of Oligocene-Miocene shallow water deposits in the Mediterranean region. The 120-m-thick late Oligocene-late Miocene carbonate succession is composed of larger foraminiferal, bryozoan and corallinacean limestones interlayered with distinct planktonic foraminiferal carbonates representing a mostly outer neritic setting. Integrated multi-proxy and facies analyses indicate that CaCO3 and total organic carbon contents as well as gamma-ray display only local to regional processes on the carbonate platform and are not suited for stratigraphic correlation on a wider scale. In contrast, new biostratigraphic data correlate the Decontra stable carbon isotope record to the global deep-sea carbon isotope record. This links relative sea level fluctuations, which are reflected by facies and magnetic susceptibility changes, to third-order eustatic cycles. The new integrated bio-, chemo-, and sequence stratigraphic framework enables a more precise timing of environmental changes within the studied time interval and identifies Decontra as an important locality for correlating not only shallow and deep water sediments of the Mediterranean region but also on a global scale.
Reuter, Markus; Piller, Werner E.; Brandano, Marco; Harzhauser, Mathias
2013-01-01
Shallow-marine sediment records have the strong potential to display sensitive environmental changes in sedimentary geometries and skeletal content. However, the time resolution of most neritic carbonate records is not high enough to be compared with climatic events as recorded in the deep-sea sediment archives. In order to resolve the paleoceanographic and paleoclimatic changes during the Oligocene–Miocene transition in the Mediterranean shallow water carbonate systems with the best possible time resolution, we re-evaluated the Decontra section on the Maiella Platform (central Apennines, Italy), which acts as a reference for the correlation of Oligocene–Miocene shallow water deposits in the Mediterranean region. The 120-m-thick late Oligocene–late Miocene carbonate succession is composed of larger foraminiferal, bryozoan and corallinacean limestones interlayered with distinct planktonic foraminiferal carbonates representing a mostly outer neritic setting. Integrated multi-proxy and facies analyses indicate that CaCO3 and total organic carbon contents as well as gamma-ray display only local to regional processes on the carbonate platform and are not suited for stratigraphic correlation on a wider scale. In contrast, new biostratigraphic data correlate the Decontra stable carbon isotope record to the global deep-sea carbon isotope record. This links relative sea level fluctuations, which are reflected by facies and magnetic susceptibility changes, to third-order eustatic cycles. The new integrated bio-, chemo-, and sequence stratigraphic framework enables a more precise timing of environmental changes within the studied time interval and identifies Decontra as an important locality for correlating not only shallow and deep water sediments of the Mediterranean region but also on a global scale. PMID:25844021
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Dag Myrhaug
2017-04-01
Full Text Available The paper provides a simple and analytical method which can be used to give estimates of the wave-induced bottom shear stress for very rough beds and mud beds in shallow water based on wind statistics in deep water. This is exemplified by using long-term wind statistics from the northern North Sea, and by providing examples representing realistic field conditions. Based on, for example, global wind statistics, the present results can be used to make estimates of the bottom shear stress in shallow water.
Ten themes of viscous liquid dynamics
DEFF Research Database (Denmark)
Dyre, J. C.
2007-01-01
simplifies the theory by allowing for an ultra-local Hamiltonian (free energy), but also explains the observed general independence of chemistry. Whereas there are no long-ranged static (i.e., equal-time) correlations in the model, there are important long-ranged dynamic correlations on the alpha timescale.......Ten ‘themes' of viscous liquid physics are discussed with a focus on how they point to a general description of equilibrium viscous liquid dynamics (i.e., fluctuations) at a given temperature. This description is based on standard time-dependent Ginzburg-Landau equations for the density fields...
Viscous computations using a direct solver
Venkatakrishnan, V.
1990-01-01
Laminar viscous flows over airfoils are investigated analytically, applying the flux-difference splitting scheme of Roe (1986) to solve the thin-layer Navier-Stokes equations. Central-difference discretization is used for the viscous terms, and a fully implicit implementation is employed to minimize the Reynolds-number effect on convergence. Results for flows at freestream Mach number 0.5 and Reynolds number 5000 over NACA0012 airfoils at angles of attack 0 and 3 deg are presented graphically and discussed in detail. Good agreement with previous calculations is obtained, with accurate reproduction of essential features despite the use of coarser meshes.
2015-04-01
Stokes flow, overland flow, as well as two-dimensional (2D) shallow water flow. As part of the natural progression of ADH, a three-dimensional (3D...Willmott, C. J. 1982. Some comments on the evaluation of model performance. Bulletin of American Meteorological Society 63(11): 1309–1313. Willmott
Boekschoten, G.J.; Borel Best, M.
1988-01-01
Miocene hermatypic corals are listed from Madeira and Porto Santo. Pleistocene and recent shallow water corals are described from the Cape Verde archipelago. The Miocene fauna was part of the Western Tethyan reef association, which went nearly completely extinct by the development of a cool water
2015-09-30
of Acoustic Field Statistics for Deep ...00303 LONG-TERM GOALS The long-term goals of this research are to understand the statistics of acoustic fields in both deep and shallow water ocean...environments. OBJECTIVES The primary objective of this work is the development of accurate, and computationally efficient, reduced-physics acoustic
Li, Zhiyong; Wang, Yuezhu; Li, Jinlong; Liu, Fang; He, Liming; He, Ying; Wang, Shenyue
2016-12-01
Sponges host complex symbiotic communities, but to date, the whole picture of the metabolic potential of sponge microbiota remains unclear, particularly the difference between the shallow-water and deep-sea sponge holobionts. In this study, two completely different sponges, shallow-water sponge Theonella swinhoei from the South China Sea and deep-sea sponge Neamphius huxleyi from the Indian Ocean, were selected to compare their whole symbiotic communities and metabolic potential, particularly in element transformation. Phylogenetically diverse bacteria, archaea, fungi, and algae were detected in both shallow-water sponge T. swinhoei and deep-sea sponge N. huxleyi, and different microbial community structures were indicated between these two sponges. Metagenome-based gene abundance analysis indicated that, though the two sponge microbiota have similar core functions, they showed different potential strategies in detailed metabolic processes, e.g., in the transformation and utilization of carbon, nitrogen, phosphorus, and sulfur by corresponding microbial symbionts. This study provides insight into the putative metabolic potentials of the microbiota associated with the shallow-water and deep-sea sponges at the whole community level, extending our knowledge of the sponge microbiota's functions, the association of sponge- microbes, as well as the adaption of sponge microbiota to the marine environment.
Energy Technology Data Exchange (ETDEWEB)
Hong, Woo Pyo [Catholic Univ. of Taegy-Hyosung Hayang, Kyongsan, Kyungbuk (Korea). Dept. of Physics
1999-07-01
It is showed that the application of the truncated Painleve' expansion and symbolic computation leads to a new class of analytical solitonic solutions to general fifth-order shallow-water wave models. The previously published solutions turn out to be the special cases here with the restricted model parameters.
Shallow water mud-mounds of the Early Devonian Buchan Group, East Gippsland, Australia
Tosolini, A.-M. P.; Wallace, M. W.; Gallagher, S. J.
2012-12-01
The Lower Devonian Rocky Camp Member of the Murrindal Limestone, Buchan Group of southeastern Australia consists of a series of carbonate mud-mounds and smaller lagoonal bioherms. The Rocky Camp mound is the best exposed of the mud-mounds and has many characteristics in common with Waulsortian (Carboniferous) mounds. Detailed paleoecological and sedimentological studies indicate that the mound initially accumulated in the photic zone, in contrast to most of the previously recorded mud-mounds. Five facies are present in the mud-mound: a Dasycladacean Wackestone Facies at the base of the mound represents a moderate energy, shallow water bank environment within the photic zone. A Crinioidal Wackestone Facies was deposited in a laterally equivalent foreslope setting. A Poriferan-Crinoidal Mudstone Facies developed in a quiet, deeper water, lee-side mound setting associated with a minor relative sea-level rise. A Stromatoporoid-Coralline Packstone Facies in the upper part of the mound deposited in a high-energy, fair-weather wave base, mound-front environment. The crest of the mound is represented by a Crinoidal-Receptaculitid Packstone Facies indicative of a moderate-energy mound-top environment in the photic zone, sheltered by the mound-front stromatoporoid-coral communities. A mound flank facies is present on the southern side of the mound and this consists of high-energy crinoidal grainstones. Mud-mound deposition was terminated by a transgression that deposited dark gray, fossil-poor marl of the overlying Taravale Formation. The Rocky Camp mound appears to have originated in shallow water photic zone conditions and grew into a high-energy environment, with the mound being eventually colonized by corals and stromatoporoids. The indications of a high-energy environment during later mound growth (growth form of colonial metazoans and grainstones of the flanking facies) suggest that the micrite in the mound was autochthonous and implies the presence of an energy
Letellier, T.; Le Provost, C.; Lyard, F.
2003-04-01
Ocean tides have been intensively studied at the global scale during the last decade. Their knowledge has been greatly improved thanks to satellite altimetry and assimilation of these data in new hydrodynamic models. Over the continental shelves and coastal areas, however, larger uncertainties remains in the description of the tides. The accuracy of the main constituents (M2, S2, N2, ...) is still limited to a ten of cm, by contrast to the cm level reached for the deep ocean. For the non linear constituents, only a few studies have addressed the question: how spatial altimetry data can be used to improve our knowledge over the major shallow water areas of the world ocean? Our aim is here to investigate these questions by focusing on the European shelf. We have now more than ten years of Topex/Poseidon data, followed by JASON1, and ERS+ENVISAT altimetric mission. From these data sets, we have performed along track and cross over analyses to investigate the accuracy of the tidal constituents, especially non linear constituents. It has been demonstrated, among other things, how this accuracy can be improved by using more elaborated "inverse barometer" correction based on a hydrodynamic model simulating the response of the sea level to high frequency atmospheric forcing. Over the shallow water areas, the horizontal scales of the non linear tidal components are greatly reduced, as the square root of the depth in relation with their propagation speed, and proportionally to their time period for the higher constituents (M4, MS4, ...). The spatial resolution of the altimetric mission is then a limiting factor for precise description of these constituents. Hence the interest of assimilating these data in a hydrodynamic model. Following the approach developed by our group for the global ocean (the "FES" Finite Element ocean tide Solutions series, that have been produced over the recent years), such assimilation exercises have been performed and qualified. The portability of
Directory of Open Access Journals (Sweden)
Line Hermannsen
Full Text Available Airguns used in seismic surveys are among the most prevalent and powerful anthropogenic noise sources in marine habitats. They are designed to produce most energy below 100 Hz, but the pulses have also been reported to contain medium-to-high frequency components with the potential to affect small marine mammals, which have their best hearing sensitivity at higher frequencies. In shallow water environments, inhabited by many of such species, the impact of airgun noise may be particularly challenging to assess due to complex propagation conditions. To alleviate the current lack of knowledge on the characteristics and propagation of airgun pulses in shallow water with implications for effects on small marine mammals, we recorded pulses from a single airgun with three operating volumes (10 in3, 25 in3 and 40 in3 at six ranges (6, 120, 200, 400, 800 and 1300 m in a uniform shallow water habitat using two calibrated Reson 4014 hydrophones and four DSG-Ocean acoustic data recorders. We show that airgun pulses in this shallow habitat propagated out to 1300 meters in a way that can be approximated by a 18log(r geometric transmission loss model, but with a high pass filter effect from the shallow water depth. Source levels were back-calculated to 192 dB re µPa2s (sound exposure level and 200 dB re 1 µPa dB Leq-fast (rms over 125 ms duration, and the pulses contained substantial energy up to 10 kHz, even at the furthest recording station at 1300 meters. We conclude that the risk of causing hearing damage when using single airguns in shallow waters is small for both pinnipeds and porpoises. However, there is substantial potential for significant behavioral responses out to several km from the airgun, well beyond the commonly used shut-down zone of 500 meters.
Starks, Trevor A.; Long, James M.; Dzialowski, Andrew R.
2016-01-01
Anthropogenic alterations to aquatic ecosystems have greatly reduced and homogenized riverine habitat, especially those used by larval and juvenile fishes. Creation of shallow-water habitats is used as a restoration technique in response to altered conditions in several studies globally, but only recently in the USA. In the summer of 2012, the U.S. Army Corps of Engineers sampled larval and juvenile fishes at six paired sites (mainstem and constructed chute shallow-water habitats) along a section of the Missouri River between Rulo, NE and St. Louis, MO, USA. From those samples, we enumerated and identified a total of 7622 fishes representing 12 families. Community responses of fishes to created shallow-water habitats were assessed by comparisons of species richness and diversity measures between paired sites and among sampling events. Shannon entropy measures were transformed, and gamma diversity (total diversity) was partitioned into two components, alpha (within community) and beta (between community) diversity using a multiplicative decomposition method. Mantel test results suggest site location, time of sampling event and habitat type were drivers of larval and juvenile community structure. Paired t-test results indicated little to no differences in beta diversity between habitat types; however, chute habitats had significantly higher alpha and gamma diversity as well as increased abundances of Asian carp larvae when compared with mainstem shallow-water habitat. Our results not only show the importance of created shallow-water habitat in promoting stream fish diversity but also highlight the role space and time may play in future restoration and management efforts.
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Ziliang Liu
Full Text Available A large, shallow braided river delta sedimentary system developed in the Yanchang Formation during the Triassic in the southwest of the Ordos basin. In this braided delta system, abundant oil and gas resources have been observed, and the area is a hotspot for oil and gas resource exploration. Through extensive field work on outcrops and cores and analyses of geophysical data, it was determined that developments in the Late Triassic produced favorable geological conditions for the development of shallow water braided river deltas. Such conditions included a large basin, flat terrain, and wide and shallow water areas; wet and dry cyclical climate changes; ancient water turbulence; dramatic depth cycle changes; ancient uplift development; strong weathering of parent rock; and abundant supply. The shallow water braided river delta showed grain sediment granularity, plastic debris, and sediment with mature composition and structure that reflected the strong hydrodynamic environment of large tabular cross-bedding, wedge cross-bedding, and multiple positive rhythms superimposed to form a thick sand body layer. The branch river bifurcation developed underwater, and the thickness of the sand body increased further, indicating that the slope was slow and located in shallow water. The seismic responses of the braided river delta reflected strong shallow water performance, indicated by a progradation seismic reflection phase axis that was relatively flat; in addition, the seismic reflection amplitude was strong and continuous with a low angle and extended over considerable distances (up to 50 km. The sedimentary center was close to the provenance, the width of the river was large, and a shallow sedimentary structure and a sedimentary rhythm were developed. The development of the delta was primarily controlled by tectonic activity and changes in the lake level; as a result, the river delta sedimentary system eventually presented a "small plain, big front
Liu, Ziliang; Shen, Fang; Zhu, Xiaomin; Li, Fengjie; Tan, Mengqi
2015-01-01
A large, shallow braided river delta sedimentary system developed in the Yanchang Formation during the Triassic in the southwest of the Ordos basin. In this braided delta system, abundant oil and gas resources have been observed, and the area is a hotspot for oil and gas resource exploration. Through extensive field work on outcrops and cores and analyses of geophysical data, it was determined that developments in the Late Triassic produced favorable geological conditions for the development of shallow water braided river deltas. Such conditions included a large basin, flat terrain, and wide and shallow water areas; wet and dry cyclical climate changes; ancient water turbulence; dramatic depth cycle changes; ancient uplift development; strong weathering of parent rock; and abundant supply. The shallow water braided river delta showed grain sediment granularity, plastic debris, and sediment with mature composition and structure that reflected the strong hydrodynamic environment of large tabular cross-bedding, wedge cross-bedding, and multiple positive rhythms superimposed to form a thick sand body layer. The branch river bifurcation developed underwater, and the thickness of the sand body increased further, indicating that the slope was slow and located in shallow water. The seismic responses of the braided river delta reflected strong shallow water performance, indicated by a progradation seismic reflection phase axis that was relatively flat; in addition, the seismic reflection amplitude was strong and continuous with a low angle and extended over considerable distances (up to 50 km). The sedimentary center was close to the provenance, the width of the river was large, and a shallow sedimentary structure and a sedimentary rhythm were developed. The development of the delta was primarily controlled by tectonic activity and changes in the lake level; as a result, the river delta sedimentary system eventually presented a "small plain, big front" character.
Viscous Flow over Nonlinearly Stretching Sheet with Effects of Viscous Dissipation
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Javad Alinejad
2012-01-01
Full Text Available The flow and heat transfer characteristics of incompressible viscous flow over a nonlinearly stretching sheet with the presence of viscous dissipation is investigated numerically. The similarity transformation reduces the time-independent boundary layer equations for momentum and thermal energy into a set of coupled ordinary differential equations. The obtained equations, including nonlinear equation for the velocity field and differential equation by variable coefficient for the temperature field , are solved numerically by using the fourth order of Runge-Kutta integration scheme accompanied by shooting technique with Newton-Raphson iteration method. The effect of various values of Prandtl number, Eckert number and nonlinear stretching parameter are studied. The results presented graphically show some behaviors such as decrease in dimensionless temperature due to increase in Pr number, and curve relocations are observed when heat dissipation is considered.
Block Fusion on Dynamically Adaptive Spacetree Grids for Shallow Water Waves
Weinzierl, Tobias
2014-09-01
© 2014 World Scientific Publishing Company. Spacetrees are a popular formalism to describe dynamically adaptive Cartesian grids. Even though they directly yield a mesh, it is often computationally reasonable to embed regular Cartesian blocks into their leaves. This promotes stencils working on homogeneous data chunks. The choice of a proper block size is sensitive. While large block sizes foster loop parallelism and vectorisation, they restrict the adaptivity\\'s granularity and hence increase the memory footprint and lower the numerical accuracy per byte. In the present paper, we therefore use a multiscale spacetree-block coupling admitting blocks on all spacetree nodes. We propose to find sets of blocks on the finest scale throughout the simulation and to replace them by fused big blocks. Such a replacement strategy can pick up hardware characteristics, i.e. which block size yields the highest throughput, while the dynamic adaptivity of the fine grid mesh is not constrained - applications can work with fine granular blocks. We study the fusion with a state-of-the-art shallow water solver at hands of an Intel Sandy Bridge and a Xeon Phi processor where we anticipate their reaction to selected block optimisation and vectorisation.
Hannak, Judith S; Kompatscher, Sarah; Stachowitsch, Michael; Herler, Jürgen
2011-10-01
Shallow reefs (reef flats tourism that includes swimmers, snorkellers and reef walkers but have largely been neglected in past studies. We selected a fringing reef along the lagoon of Dahab (Sinai, Egypt) as a model for a management strategy. Point-intercept line transects were used to determine substrate composition, coral community and condition, and the coral damage index (CDI) was applied. Approximately 84% of the coral colonies showed signs of damage such as breakage, partial mortality or algal overgrowth, especially affecting the most frequent coral genus Acropora. Questionnaires were used to determine the visitors' socio-economic background and personal attitudes regarding snorkelling, SCUBA-diving and interest in visiting a prospective snorkelling trail. Experiencing nature (97%) was by far the strongest motivation, and interest in further education about reef ecology and skill training was high. Less experienced snorkellers and divers--the target group for further education and skill training--were those most prepared to financially support such a trail. We therefore recommend a guided underwater snorkelling trail and restricting recreational use to a less sensitive 'ecotourism zone' while protecting the shallow reef flat. Artificial structures can complete the trail and offer the opportunity to snorkel over deeper areas at unfavourable tide or wind conditions. This approach provides a strategy for the management and conservation of shallow-water reefs, which are facing increasing human impact here and elsewhere. Copyright © 2011 Elsevier Ltd. All rights reserved.
HYDROACOUSTIC OBSERVATIONS OF WEAK EARTHQUAKES IN SHALLOW WATERS OF THE SOUTHERN KURIL ISLANDS
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Alexander S. Borisov
2012-01-01
Full Text Available Results of hydroacoustic observations of signals from weak earthquakes in natural conditions in the region of the Southern Kuril Islands are presented. Some earthquakes were registered by the the Yuzhno-Kurilsk Seismic Station, other were only recorded by hydrophone stations. The observations were specific as seismic signals were recorded in shallow waters, i.e. in high noise level conditions. Hydrophones were installed in Lake Lagunnoe (Kunashir and Khromovaya Bay (Shikotan. Our analysis of hydroacoustic records received from the hydrophone stations revealed no evident precursory response of the geological medium to weak distant events. This means that neither before the period of earthquake preparation nor during the earthquake preparation period, any geoacoustic emission was not detected. It is shown that despite the unfavourable noise level conditions, even distant weak earthquakes can be confidently registered by hydrophone stations, and pending application of proper signal processing techniques, it can be possible to determine arrival times of seismic waves and to measure parameters of seismic waves. It is also established that the frequency spectrum of acoustic signals from the weak earthquakes recordable by the hydrophone stations is continuous and of noise type in the frequency range up to 90–100 Hz. It is revealed that in some cases, weak earthquakes and microearthquakes may be forerun by low frequency signals.
Deb Roy, Gauranga; Fazlul Karim, Md.; Ismail, Ahmad Izani M.
2007-01-01
A nonlinear shallow water model in cylindrical polar coordinate system is developed, using an explicit finite difference scheme with a very fine resolution, to compute different aspects of tsunami at North Sumatra and the adjacent island Simeulue in Indonesia, and the Penang Island in Peninsular Malaysia. The pole of the frame is placed on the mainland of Penang (100.5°E) and the model area extends up to the west of Sumatra (87.5°E). The model is applied to simulate the propagation of tsunami wave towards North Sumatra, Simeulue and Penang Islands associated with Indonesian tsunami of 26 December 2004. The model is also applied to compute water levels along the coastal belts of those islands. Computed and observed water level data are found to be in good agreement and North Sumatra is found to be vulnerable for very high surges. The computed and observed arrival times of high surges are also in reasonable agreement everywhere. Further studies are carried out to investigate the effect of convective terms and it is found that their effects are insignificant in tsunami propagation and weakly significant for wave amplitude very near to the coast.
Research on characteristics of radiated noise of large cargo ship in shallow water
Liu, Yongdong; Zhang, Liang
2017-01-01
With the rapid development of the shipping industry, the number of the world's ship is gradually increasing. The characteristics of the radiated noise of the ship are also of concern. Since the noise source characteristics of multichannel interference, the surface wave and the sea temperature microstructure and other reasons, the sound signal received in the time-frequency domain has varying characteristics. The signal of the radiated noise of the large cargo ship JOCHOH from horizontal hydrophone array in some shallow water of China is processed and analyzed in the summer of 2015, and the results show that a large cargo ship JOCHOH has a number of noise sources in the direction of the ship's bow and stern lines, such as host, auxiliary and propellers. The radiating sound waves generated by these sources do not meet the spherical wave law at lower frequency in the ocean, and its radiated noise has inherent spatial distribution, the variation characteristics of the radiated noise the large cargo ship in time and frequency domain are given. The research method and results are of particular importance.
Eythorsdottir, Arnheidur; Omarsdottir, Sesselja; Einarsson, Hjorleifur
2016-06-01
Marine sponges and other sessile macro-organisms were collected at a shallow water hydrothermal site in Eyjafjörður, Iceland. Bacteria were isolated from the organisms using selective media for actinomycetes, and the isolates were screened for antimicrobial activity. A total of 111 isolates revealed antimicrobial activity displaying different antimicrobial patterns which indicates production of various compounds. Known test strains were grown in the presence of ethyl acetate extracts from one selected isolate, and a clear growth inhibition of Staphylococcus aureus was observed down to 0.1 % extract concentration in the medium. Identification of isolates shows different species of Actinobacteria with Streptomyces sp. playing the largest role, but also members of Bacilli, Alphaproteobacteria and Gammaproteobacteria. Sponges have an excellent record regarding production of bioactive compounds, often involving microbial symbionts. At the hydrothermal vents, however, the majority of active isolates originated from other invertebrates such as sea anemones or algae. The results indicate that antimicrobial assays involving isolates in full growth can detect activity not visible by other methods. The macro-organisms inhabiting the Eyjafjörður hydrothermal vent area host diverse microbial species in the phylum Actinobacteria with antimicrobial activity, and the compounds responsible for the activity will be subject to further research.
A New Approach to Quantify Shallow Water Hydrologic Exchanges in a Large Regulated River Reach
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Tian Zhou
2017-09-01
Full Text Available Hydrologic exchange is a crucial component of the water cycle. The strength of the exchange directly affects the biogeochemical and ecological processes that occur in the hyporheic zone and aquifer from micro to reach scales. Hydrologic exchange fluxes (HEFs can be quantified using many field measurement approaches, however, in a relatively large river (scale > 103 m, these approaches are limited by site accessibility, the difficulty of performing representative sampling, and the complexity of geomorphologic features and subsurface properties. In rivers regulated by hydroelectric dams, quantifying HEF rates becomes more challenging because of frequent hydropeaking events, featuring hourly to daily variations in flow and river stages created by dam operations. In this study, we developed and validated a new approach based on field measurements to estimate shallow water HEF rates across the river bed along the shoreline of the Columbia River, USA. Vertical thermal profiles measured by self-recording thermistors were combined with time series of hydraulic gradients derived from river stages and inland water levels to estimate the HEF rates. The results suggest that the HEF rates had high spatial and temporal heterogeneities over the riverbed, with predicted flux rates varied from +1 × 10−6 m s−1 to −1.5 × 10−6 m s−1 under different flow conditions.
Relative Pigment Composition and Remote Sensing Reflectance of Caribbean Shallow-Water Corals.
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Juan L Torres-Pérez
Full Text Available Reef corals typically contain a number of pigments, mostly due to their symbiotic relationship with photosynthetic dinoflagellates. These pigments usually vary in presence and concentration and influence the spectral characteristics of corals. We studied the variations in pigment composition among seven Caribbean shallow-water Scleractinian corals by means of High Performance Liquid Chromatography (HPLC analysis to further resolve the discrimination of corals. We found a total of 27 different pigments among the coral species, including some alteration products of the main pigments. Additionally, pigments typically found in endolithic algae were also identified. A Principal Components Analysis and a Hierarchical Cluster Analysis showed the separation of coral species based on pigment composition. All the corals were collected under the same physical environmental conditions. This suggests that pigment in the coral's symbionts might be more genetically-determined than influenced by prevailing physical conditions of the reef. We further investigated the use of remote sensing reflectance (Rrs as a tool for estimating the total pigment concentration of reef corals. Depending on the coral species, the Rrs and the total symbiont pigment concentration per coral tissue area correlation showed 79.5-98.5% confidence levels demonstrating its use as a non-invasive robust technique to estimate pigment concentration in studies of coral reef biodiversity and health.
Relative Pigment Composition and Remote Sensing Reflectance of Caribbean Shallow-Water Corals.
Torres-Pérez, Juan L; Guild, Liane S; Armstrong, Roy A; Corredor, Jorge; Zuluaga-Montero, Anabella; Polanco, Ramón
2015-01-01
Reef corals typically contain a number of pigments, mostly due to their symbiotic relationship with photosynthetic dinoflagellates. These pigments usually vary in presence and concentration and influence the spectral characteristics of corals. We studied the variations in pigment composition among seven Caribbean shallow-water Scleractinian corals by means of High Performance Liquid Chromatography (HPLC) analysis to further resolve the discrimination of corals. We found a total of 27 different pigments among the coral species, including some alteration products of the main pigments. Additionally, pigments typically found in endolithic algae were also identified. A Principal Components Analysis and a Hierarchical Cluster Analysis showed the separation of coral species based on pigment composition. All the corals were collected under the same physical environmental conditions. This suggests that pigment in the coral's symbionts might be more genetically-determined than influenced by prevailing physical conditions of the reef. We further investigated the use of remote sensing reflectance (Rrs) as a tool for estimating the total pigment concentration of reef corals. Depending on the coral species, the Rrs and the total symbiont pigment concentration per coral tissue area correlation showed 79.5-98.5% confidence levels demonstrating its use as a non-invasive robust technique to estimate pigment concentration in studies of coral reef biodiversity and health.
Directory of Open Access Journals (Sweden)
Francisco Eugenio
2017-11-01
Full Text Available Remote multispectral data can provide valuable information for monitoring coastal water ecosystems. Specifically, high-resolution satellite-based imaging systems, as WorldView-2 (WV-2, can generate information at spatial scales needed to implement conservation actions for protected littoral zones. However, coastal water-leaving radiance arriving at the space-based sensor is often small as compared to reflected radiance. In this work, complex approaches, which usually use an accurate radiative transfer code to correct the atmospheric effects, such as FLAASH, ATCOR and 6S, have been implemented for high-resolution imagery. They have been assessed in real scenarios using field spectroradiometer data. In this context, the three approaches have achieved excellent results and a slightly superior performance of 6S model-based algorithm has been observed. Finally, for the mapping of benthic habitats in shallow-waters marine protected environments, a relevant application of the proposed atmospheric correction combined with an automatic deglinting procedure is presented. This approach is based on the integration of a linear mixing model of benthic classes within the radiative transfer model of the water. The complete methodology has been applied to selected ecosystems in the Canary Islands (Spain but the obtained results allow the robust mapping of the spatial distribution and density of seagrass in coastal waters and the analysis of multitemporal variations related to the human activity and climate change in littoral zones.
Eugenio, Francisco; Marcello, Javier; Martin, Javier; Rodríguez-Esparragón, Dionisio
2017-11-16
Remote multispectral data can provide valuable information for monitoring coastal water ecosystems. Specifically, high-resolution satellite-based imaging systems, as WorldView-2 (WV-2), can generate information at spatial scales needed to implement conservation actions for protected littoral zones. However, coastal water-leaving radiance arriving at the space-based sensor is often small as compared to reflected radiance. In this work, complex approaches, which usually use an accurate radiative transfer code to correct the atmospheric effects, such as FLAASH, ATCOR and 6S, have been implemented for high-resolution imagery. They have been assessed in real scenarios using field spectroradiometer data. In this context, the three approaches have achieved excellent results and a slightly superior performance of 6S model-based algorithm has been observed. Finally, for the mapping of benthic habitats in shallow-waters marine protected environments, a relevant application of the proposed atmospheric correction combined with an automatic deglinting procedure is presented. This approach is based on the integration of a linear mixing model of benthic classes within the radiative transfer model of the water. The complete methodology has been applied to selected ecosystems in the Canary Islands (Spain) but the obtained results allow the robust mapping of the spatial distribution and density of seagrass in coastal waters and the analysis of multitemporal variations related to the human activity and climate change in littoral zones.
Integrating Sensors into a Marine Drone for Bathymetric 3D Surveys in Shallow Waters
Directory of Open Access Journals (Sweden)
Francesco Giordano
2015-12-01
Full Text Available This paper demonstrates that accurate data concerning bathymetry as well as environmental conditions in shallow waters can be acquired using sensors that are integrated into the same marine vehicle. An open prototype of an unmanned surface vessel (USV named MicroVeGA is described. The focus is on the main instruments installed on-board: a differential Global Position System (GPS system and single beam echo sounder; inertial platform for attitude control; ultrasound obstacle-detection system with temperature control system; emerged and submerged video acquisition system. The results of two cases study are presented, both concerning areas (Sorrento Marina Grande and Marechiaro Harbour, both in the Gulf of Naples characterized by a coastal physiography that impedes the execution of a bathymetric survey with traditional boats. In addition, those areas are critical because of the presence of submerged archaeological remains that produce rapid changes in depth values. The experiments confirm that the integration of the sensors improves the instruments’ performance and survey accuracy.
Integrating Sensors into a Marine Drone for Bathymetric 3D Surveys in Shallow Waters.
Giordano, Francesco; Mattei, Gaia; Parente, Claudio; Peluso, Francesco; Santamaria, Raffaele
2015-12-29
This paper demonstrates that accurate data concerning bathymetry as well as environmental conditions in shallow waters can be acquired using sensors that are integrated into the same marine vehicle. An open prototype of an unmanned surface vessel (USV) named MicroVeGA is described. The focus is on the main instruments installed on-board: a differential Global Position System (GPS) system and single beam echo sounder; inertial platform for attitude control; ultrasound obstacle-detection system with temperature control system; emerged and submerged video acquisition system. The results of two cases study are presented, both concerning areas (Sorrento Marina Grande and Marechiaro Harbour, both in the Gulf of Naples) characterized by a coastal physiography that impedes the execution of a bathymetric survey with traditional boats. In addition, those areas are critical because of the presence of submerged archaeological remains that produce rapid changes in depth values. The experiments confirm that the integration of the sensors improves the instruments' performance and survey accuracy.
High-Resolution Wave Energy Assessment in Shallow Water Accounting for Tides
Directory of Open Access Journals (Sweden)
Dina Silva
2016-09-01
Full Text Available The wave energy in a shallow water location is evaluated considering the influence of the local tide and wind on the wave propagation. The target is the coastal area just north of the Portuguese city of Peniche, where a wave energy converter operates on the sea bottom. A wave modelling system based on SWAN has been implemented and focused on this coastal environment in a multilevel computational scheme. The first three SWAN computational belonging to this wave prediction system were defined using the spherical coordinates. In the highest resolution computational domain, Cartesian coordinates have been considered, with a resolution of 25 m in both directions. An in-depth analysis of the main characteristics of the environmental matrix has been performed. This is based on the results of eight-year model system simulations (2005–2012. New simulations have been carried out in the last two computational domains with the most relevant wave and wind patterns, considering also the tide effect. The results show that the tide level, together with the wind intensity and direction, may influence to a significant degree the wave characteristics. This especially concerns the wave power in the location where the wave converter operates.
HYDROACOUSTIC OBSERVATIONS OF WEAK EARTHQUAKES IN SHALLOW WATERS OF THE SOUTHERN KURIL ISLANDS
Directory of Open Access Journals (Sweden)
Alexander S. Borisov
2015-09-01
Full Text Available Results of hydroacoustic observations of signals from weak earthquakes in natural conditions in the region of the Southern Kuril Islands are presented. Some earthquakes were registered by the the Yuzhno-Kurilsk Seismic Station, other were only recorded by hydrophone stations. The observations were specific as seismic signals were recorded in shallow waters, i.e. in high noise level conditions. Hydrophones were installed in Lake Lagunnoe (Kunashir and Khromovaya Bay (Shikotan. Our analysis of hydroacoustic records received from the hydrophone stations revealed no evident precursory response of the geological medium to weak distant events. This means that neither before the period of earthquake preparation nor during the earthquake preparation period, any geoacoustic emission was not detected. It is shown that despite the unfavourable noise level conditions, even distant weak earthquakes can be confidently registered by hydrophone stations, and pending application of proper signal processing techniques, it can be possible to determine arrival times of seismic waves and to measure parameters of seismic waves. It is also established that the frequency spectrum of acoustic signals from the weak earthquakes recordable by the hydrophone stations is continuous and of noise type in the frequency range up to 90–100 Hz. It is revealed that in some cases, weak earthquakes and microearthquakes may be forerun by low frequency signals.
Integrating Sensors into a Marine Drone for Bathymetric 3D Surveys in Shallow Waters
Giordano, Francesco; Mattei, Gaia; Parente, Claudio; Peluso, Francesco; Santamaria, Raffaele
2015-01-01
This paper demonstrates that accurate data concerning bathymetry as well as environmental conditions in shallow waters can be acquired using sensors that are integrated into the same marine vehicle. An open prototype of an unmanned surface vessel (USV) named MicroVeGA is described. The focus is on the main instruments installed on-board: a differential Global Position System (GPS) system and single beam echo sounder; inertial platform for attitude control; ultrasound obstacle-detection system with temperature control system; emerged and submerged video acquisition system. The results of two cases study are presented, both concerning areas (Sorrento Marina Grande and Marechiaro Harbour, both in the Gulf of Naples) characterized by a coastal physiography that impedes the execution of a bathymetric survey with traditional boats. In addition, those areas are critical because of the presence of submerged archaeological remains that produce rapid changes in depth values. The experiments confirm that the integration of the sensors improves the instruments’ performance and survey accuracy. PMID:26729117
Wormholes in viscous cosmology
Wang, Deng
2016-01-01
We study the wormhole spacetime configurations in bulk viscosity cosmology. Considering three classes of viscous models, i.e., bulk viscosity as a function of Hubble parameter $H$, temperature $T$ and dark energy density $\\rho$, respectively, we obtain nine wormhole solutions. Through the analysis for the anisotropic solutions, we conclude that, to some extent, these three classes of viscous models have very high degeneracy with each other. Subsequently, without the loss of generality, to investigate the traversabilities, energy conditions and stability for the wormhole solution, we study the wormhole solution of the constant redshift function of the viscous $\\omega$CDM model with a constant bulk viscosity coefficient. We obtain the following conclusions: the value of traversal velocity decreases for decreasing bulk viscosity, and the traversal velocity for a traveler depends on not only the wormhole geometry but also the effects of cosmological background evolution; the null energy condition will be violated...
Domenech, John
Due to increasing atmospheric CO2 concentration and its effect on global climates, the United States Environmental Protection Agency (EPA) proposes a Clean Power Plan (CPP) mandating CO2 reductions which will likely force the early retirement of inefficient, aging power plants. Consequentially, removing these plants equates to a shortfall of approximately 66 GW of electricity. These factors add to the looming resource problems of choosing whether to build large replacement power plants or consider alternative energy sources as a means to help close the gap between electricity supply and demand in a given region. One energy source, shallow water tidal currents, represents opportunities to convert kinetic energy to mechanical forms and provide electricity to homes and businesses. Nearly 2,000 National Oceanic Atmospheric Administration (NOAA) tidal current data points from Maine to Texas are considered. This paper, based on systems engineering thinking, provides key attributes (e.g. turbine efficiency, array size, transmission losses) for consideration as decision makers seek to identify where to site Marine Hydrokinetic (MHK) systems and the number of homes powered by the practical harvest of electricity from tidal currents at those locations with given attributes. A systems engineering process model is proposed for consideration as is a regression based equation to estimate MHK machine parameters needed for power a given number of homes.
A new mini box corer for sampling muddy bottoms in antarctic shallow waters
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Carlos Alejandro Echeverría
2009-06-01
Full Text Available A new Mini Box Corer (MBC-GEAMB was developed for bottom sampling in Antarctic shallow waters down to 100 m depth from a small vessel. It consists of a detachable stainless steel box with a total sampling area of 0.0625 m², and a closing arm with a detachable blade without an external frame. MBC allowed stratified bottom sampling and good quality samples comparable to those obtained through diving. A comparison between the MBC-GEAMB and a 0.056 m²van Veen grab (VV was undertaken for the benthic macrofaunal composition in Admiralty Bay, King George Island (Antarctica. MBC and VV samples were taken from three depths (20, 30 and 60m in two sites. Total densities sampled with the MBC were up to 10 times higher than those obtained with van Veen grab. VV samples might lead to faunistic abundance underestimation compared to the MBC samples. Besides, MBC showed a higher performance on discriminating different sites as regards total macrofaunal density. It is suggested that MBC could be employed as an efficient remote sampling device for shallow-waters where direct sampling by SCUBA was not advisable.Um novo Mini Box Corer (MBC-GEAMB foi desenvolvido para amostragens de fundo em águas rasas antárticas até 100 metros de profundidade, a partir de embarcações pequenas. Consiste em uma caixa de aço inox destacável com uma área total de amostragem de 0,0625 m², e um braço de fechamento com uma lâmina destacável, sem um suporte externo. MBC permite a amostragem estratificada do sedimento de fundo com amostras de qualidade comparáveis àquelas obtidas através de mergulho autônomo. Uma comparação entre o MBC-GEAMB e um van Veen de área 0,056 m²(VV foi realizada utilizando a composição da macrofauna bentônica na Baía do Almirantado, (Ilha Rei George, Antarctica. Amostragens com MBC e VV foram realizadas em três profundidades (20, 30 e 60m em dois locais. As densidades totais obtidas com o MBC foram até 10 vezes maiores que as obtidas
Energy Technology Data Exchange (ETDEWEB)
Verma, Devendra; Tomar, Vikas, E-mail: tomar@purdue.edu
2014-11-01
The present investigation focuses on understanding the influence of change from wet to dry environment on nanomechanical properties of shallow water shrimp exoskeleton. Scanning Electron Microscopy (SEM) based measurements suggest that the shrimp exoskeleton has Bouligand structure, a key characteristic of the crustaceans. As expected, wet samples are found to be softer than dry samples. Reduced modulus values of dry samples are found to be 24.90 ± 1.14 GPa as compared to the corresponding values of 3.79 ± 0.69 GPa in the case of wet samples. Hardness values are found to be 0.86 ± 0.06 GPa in the case of dry samples as compared to the corresponding values of 0.17 ± 0.02 GPa in the case of wet samples. In order to simulate the influence of underwater pressure on the exoskeleton strength, constant load creep experiments as a function of wet and dry environments are performed. The switch in deformation mechanism as a function of environment is explained based on the role played by water molecules in assisting interface slip and increased ductility of matrix material in wet environment in comparison to the dry environment. - Highlights: • Environment dependent (dry-wet) properties of shrimp exoskeleton are analyzed. • Mechanical properties are correlated with the structure and composition. • Presence of water leads to lower reduced modulus and hardness. • SEM images shows the Bouligand pattern based structure. • Creep-relaxation of polymer chains, interface slip is high in presence of water.
Impacts of ocean acidification on sediment processes in shallow waters of the Arctic Ocean.
Gazeau, Frédéric; van Rijswijk, Pieter; Pozzato, Lara; Middelburg, Jack J
2014-01-01
Despite the important roles of shallow-water sediments in global biogeochemical cycling, the effects of ocean acidification on sedimentary processes have received relatively little attention. As high-latitude cold waters can absorb more CO2 and usually have a lower buffering capacity than warmer waters, acidification rates in these areas are faster than those in sub-tropical regions. The present study investigates the effects of ocean acidification on sediment composition, processes and sediment-water fluxes in an Arctic coastal system. Undisturbed sediment cores, exempt of large dwelling organisms, were collected, incubated for a period of 14 days, and subject to a gradient of pCO2 covering the range of values projected for the end of the century. On five occasions during the experimental period, the sediment cores were isolated for flux measurements (oxygen, alkalinity, dissolved inorganic carbon, ammonium, nitrate, nitrite, phosphate and silicate). At the end of the experimental period, denitrification rates were measured and sediment samples were taken at several depth intervals for solid-phase analyses. Most of the parameters and processes (i.e. mineralization, denitrification) investigated showed no relationship with the overlying seawater pH, suggesting that ocean acidification will have limited impacts on the microbial activity and associated sediment-water fluxes on Arctic shelves, in the absence of active bio-irrigating organisms. Only following a pH decrease of 1 pH unit, not foreseen in the coming 300 years, significant enhancements of calcium carbonate dissolution and anammox rates were observed. Longer-term experiments on different sediment types are still required to confirm the limited impact of ocean acidification on shallow Arctic sediment processes as observed in this study.
Impacts of ocean acidification on sediment processes in shallow waters of the Arctic Ocean.
Directory of Open Access Journals (Sweden)
Frédéric Gazeau
Full Text Available Despite the important roles of shallow-water sediments in global biogeochemical cycling, the effects of ocean acidification on sedimentary processes have received relatively little attention. As high-latitude cold waters can absorb more CO2 and usually have a lower buffering capacity than warmer waters, acidification rates in these areas are faster than those in sub-tropical regions. The present study investigates the effects of ocean acidification on sediment composition, processes and sediment-water fluxes in an Arctic coastal system. Undisturbed sediment cores, exempt of large dwelling organisms, were collected, incubated for a period of 14 days, and subject to a gradient of pCO2 covering the range of values projected for the end of the century. On five occasions during the experimental period, the sediment cores were isolated for flux measurements (oxygen, alkalinity, dissolved inorganic carbon, ammonium, nitrate, nitrite, phosphate and silicate. At the end of the experimental period, denitrification rates were measured and sediment samples were taken at several depth intervals for solid-phase analyses. Most of the parameters and processes (i.e. mineralization, denitrification investigated showed no relationship with the overlying seawater pH, suggesting that ocean acidification will have limited impacts on the microbial activity and associated sediment-water fluxes on Arctic shelves, in the absence of active bio-irrigating organisms. Only following a pH decrease of 1 pH unit, not foreseen in the coming 300 years, significant enhancements of calcium carbonate dissolution and anammox rates were observed. Longer-term experiments on different sediment types are still required to confirm the limited impact of ocean acidification on shallow Arctic sediment processes as observed in this study.
A numerical shallow-water model for gravity currents for a wide range of density differences
Shimizu, Hiroyuki A.; Koyaguchi, Takehiro; Suzuki, Yujiro J.
2017-12-01
Gravity currents with various contrasting densities play a role in mass transport in a number of geophysical situations. The ratio of the density of the current, ρ c, to the density of the ambient fluid, ρ a, can vary between 100 and 103. In this paper, we present a numerical method of simulating gravity currents for a wide range of ρ c/ ρ a using a shallow-water model. In the model, the effects of varying ρ c/ ρ a are taken into account via the front condition (i.e., factors describing the balance between the driving pressure and the ambient resistance pressure at the flow front). Previously, two types of numerical models have been proposed to solve the front condition. These are referred to here as the Boundary Condition (BC) model and the Artificial Bed (AB) model. The front condition is calculated as a boundary condition at each time step in the BC model, whereas it is calculated by setting a thin artificial bed ahead of the front in the AB model. We assessed the BC and AB models by comparing their numerical results with the analytical results for a simple case of homogeneous currents. The results from the BC model agree well with the analytical results when ρ c/ ρ a≲102, but the model tends to overestimate the speed of the front position when ρ c/ρ a≳102. In contrast, the AB model generates good approximations of the analytical results for ρ c/ρ a≳ 102, given a sufficiently small artificial bed thickness, but fails to reproduce the analytical results when ρ c/ ρ a≲102. Therefore, we propose a numerical method in which the BC model is used for currents with ρ c/ ρ a≲102 and the AB model is used for currents with ρ c/ρ a≳ 102.
Couderc, F.; Duran, A.; Vila, J.-P.
2017-08-01
We present an explicit scheme for a two-dimensional multilayer shallow water model with density stratification, for general meshes and collocated variables. The proposed strategy is based on a regularized model where the transport velocity in the advective fluxes is shifted proportionally to the pressure potential gradient. Using a similar strategy for the potential forces, we show the stability of the method in the sense of a discrete dissipation of the mechanical energy, in general multilayer and non-linear frames. These results are obtained at first-order in space and time and extended using a second-order MUSCL extension in space and a Heun's method in time. With the objective of minimizing the diffusive losses in realistic contexts, sufficient conditions are exhibited on the regularizing terms to ensure the scheme's linear stability at first and second-order in time and space. The other main result stands in the consistency with respect to the asymptotics reached at small and large time scales in low Froude regimes, which governs large-scale oceanic circulation. Additionally, robustness and well-balanced results for motionless steady states are also ensured. These stability properties tend to provide a very robust and efficient approach, easy to implement and particularly well suited for large-scale simulations. Some numerical experiments are proposed to highlight the scheme efficiency: an experiment of fast gravitational modes, a smooth surface wave propagation, an initial propagating surface water elevation jump considering a non-trivial topography, and a last experiment of slow Rossby modes simulating the displacement of a baroclinic vortex subject to the Coriolis force.
Methods for Quantifying Shallow-Water Habitat Availability in the Missouri River
Energy Technology Data Exchange (ETDEWEB)
Hanrahan, Timothy P.; Larson, Kyle B.
2012-04-09
As part of regulatory requirements for shallow-water habitat (SWH) restoration, the U.S. Army Corps of Engineers (USACE) completes periodic estimates of the quantity of SWH available throughout the lower 752 mi of the Missouri River. To date, these estimates have been made by various methods that consider only the water depth criterion for SWH. The USACE has completed estimates of SWH availability based on both depth and velocity criteria at four river bends (hereafter called reference bends), encompassing approximately 8 river miles within the lower 752 mi of the Missouri River. These estimates were made from the results of hydraulic modeling of water depth and velocity throughout each bend. Hydraulic modeling of additional river bends is not expected to be completed for deriving estimates of available SWH. Instead, future estimates of SWH will be based on the water depth criterion. The objective of this project, conducted by the Pacific Northwest National Laboratory for the USACE Omaha District, was to develop geographic information system methods for estimating the quantity of available SWH based on water depth only. Knowing that only a limited amount of water depth and channel geometry data would be available for all the remaining bends within the lower 752 mi of the Missouri River, the intent was to determine what information, if any, from the four reference bends could be used to develop methods for estimating SWH at the remaining bends. Specifically, we examined the relationship between cross-section channel morphology and relative differences between SWH estimates based on combined depth and velocity criteria and the depth-only criterion to determine if a correction factor could be applied to estimates of SWH based on the depth-only criterion. In developing these methods, we also explored the applicability of two commonly used geographic information system interpolation methods (TIN and ANUDEM) for estimating SWH using four different elevation data
Observation of Tropical Cyclone-Induced Shallow Water Currents in Taiwan Strait
Shen, Junqiang; Qiu, Yun; Zhang, Shanwu; Kuang, Fangfang
2017-06-01
The data from three stations equipped with Acoustic Doppler Current Profilers (ADCPs) deployed in the shallow water of the Taiwan Strait (TWS) were used to study the shallow coastal ocean response to five quasi-continuous tropical cyclone (TC) events in the late summer 2006. We revealed that, in the forced stage, when the large and strong TC (Bilis) transited, the geostrophic currents were formed which dominated the whole event, while the strong but relatively small one (Saomai) or the weak one (Bopha) primarily leaded to the generation of Ekman currents. In the relaxation stage, the barotropic subinertial waves and/or the baroclinic near-inertial oscillations (NIOs) were triggered. Typically, during the transit of the Saomai, subinertial waves were induced which demonstrated a period of 2.8-4.1 days and a mean alongshore phase velocity of 14.9 ± 3.2 m/s in the form of free-barotropic continental shelf waves. However, the NIOs are only notable in the area in which the water column is stably stratified and also where the wind stress is dominated by the clockwise component and accompanied by high-frequency (near-inertial) variations. We also demonstrated that, due to the damping effects, the nonlinear wave-wave interaction (e.g., between NIO and semidiurnal tide in our case), together with the well-known bottom friction, led to the rapid decay of the observed TC-induced near-inertial currents, giving a typical e-folding time scale of 1-3 inertial periods. Moreover, such nonlinear wave-wave interaction was even found to play a major role during the spring tide in TWS.
A new approach to macroalgal bloom control in eutrophic, shallow-water, coastal areas.
Lenzi, Mauro; Salvaterra, Giulia; Gennaro, Paola; Mercatali, Isabel; Persia, Emma; Porrello, Salvatore; Sorce, Carlo
2015-03-01
In summer 2012, an experiment was conducted in a shallow eutrophic lagoon with poor water exchange to determine the consequences of harvesting algae on the algal mat itself, which was traversed and repeatedly disturbed by large harvester boats. Four areas with high macroalgal density, measuring half a hectare each, were selected. Two were subjected to frequent disturbance of the algal mat and sediment (12 two-hour operations over a 38-day period) and the other two were left undisturbed as control. The following variables were determined: 1) water column physical chemistry and nutrients; 2) redox potential, nutrients and organic load in sediments; 3) C, N and P content of algal thalli; 4) macroalgal biomass. In 2013, a further experiment was conducted on a larger scale. Biomass was estimated in a high-density mat measuring 235 ha, where macroalgae were harvested and stirred up by four harvesting boats, and in two high-density mats measuring 150 and 120 ha, left undisturbed as control (9.15, 9.92 and 3.68 kg/m(2), respectively). In the first experiment, no significant changes were observed in the water column. In sediment the main variation was a significant reduction in labile organic matter in the disturbed areas and a significant increase mainly in refractory organic matter in the undisturbed areas. Biomass showed a significant drastic reduction in disturbed areas and substantial stability in undisturbed areas. In the large-scale experiment, the biomass of the disturbed mat declined by about 63%, only 6.5% of which was due to harvesting. On the other hand, the undisturbed mat with higher density underwent a natural decline in biomass of about 23% and the other increased by about 50%. These results demonstrate that disturbance of high-density mat in shallow water by boats can cause decay of the mat. Copyright © 2014 Elsevier Ltd. All rights reserved.
The Thermal Phase Curve Offset on Tidally and Nontidally Locked Exoplanets: A Shallow Water Model
Penn, James; Vallis, Geoffrey K.
2017-06-01
Using a shallow water model with time-dependent forcing, we show that the peak of an exoplanet thermal phase curve is, in general, offset from the secondary eclipse when the planet is rotating. That is, the planetary hot spot is offset from the point of maximal heating (the substellar point) and may lead or lag the forcing; the extent and sign of the offset are functions of both the rotation rate and orbital period of the planet. We also find that the system reaches a steady state in the reference frame of the moving forcing. The model is an extension of the well-studied Matsuno-Gill model into a full spherical geometry and with a planetary-scale translating forcing representing the insolation received on an exoplanet from a host star. The speed of the gravity waves in the model is shown to be a key metric in evaluating the phase curve offset. If the velocity of the substellar point (relative to the planet’s surface) exceeds that of the gravity waves, then the hot spot will lag the substellar point, as might be expected by consideration of forced gravity wave dynamics. However, when the substellar point is moving slower than the internal wave speed of the system, the hottest point may lead the passage of the forcing. We provide an interpretation of this result by consideration of the Rossby and Kelvin wave dynamics, as well as, in the very slowly rotating case, a one-dimensional model that yields an analytic solution. Finally, we consider the inverse problem of constraining planetary rotation rate from an observed phase curve.
Grigorev, Valery A; Katsnelson, Boris G; Lynch, James F
2016-11-01
Analyses of fluctuations of low frequency signals (300 ± 30 Hz) propagating in shallow water in the presence of nonlinear internal waves (NIWs) in the Shallow Water 2006 experiment are carried out. Signals were received by a vertical line array at a distance of ∼20 km from the source. A NIW train was moving totally inside of the acoustic track, and the angle between the wave front of the NIW and the acoustic track in the horizontal plane was ∼10°. It is shown that the spectrum of the sound intensity fluctuations contains peaks corresponding to the coupling of pairs of propagating modes. Analysis of spectra at different hydrophone depths, and also summed over depth allows the authors to estimate attenuation in the bottom sediments.
Caiti, A.; Jesus, S.M.; Kristensen, Age
1996-01-01
Acoustic propagation in shallow water is greatly dependent on the geoacoustic properties of the seabottom. This paper exploits this dependence for estimating geoacoustic sediment properties from the bottom acoustic returns of known signals received on a hydrophone line array. There are two major issues in this approach: one is the feasibility of acoustic inversion with a limited aperture line array, the other is related to the knowledge of the geometry of the experimental...
Johnson, Vivienne R.; Colin Brownlee; Marco Milazzo; Hall-Spencer, Jason M.
2015-01-01
Predicting the effects of anthropogenic CO2 emissions on coastal ecosystems requires an understanding of the responses of algae, since these are a vital functional component of shallow-water habitats. We investigated microphytobenthic assemblages on rock and sandy habitats along a shallow subtidal pCO2 gradient near volcanic seeps in the Mediterranean Sea. Field studies of natural pCO2 gradients help us understand the likely effects of ocean acidification because entire communities are subjec...
Brown, Alastair; Wright, Roseanna; Mevenkamp, Lisa; Hauton, Chris
2017-10-01
Exploration of deep-sea mineral resources is burgeoning, raising concerns regarding ecotoxicological impacts on deep-sea fauna. Assessing toxicity in deep-sea species is technologically challenging, which promotes interest in establishing shallow-water ecotoxicological proxy species. However, the effects of temperature and hydrostatic pressure on toxicity, and how adaptation to deep-sea environmental conditions might moderate these effects, are unknown. To address these uncertainties we assessed behavioural and physiological (antioxidant enzyme activity) responses to exposure to copper-spiked artificial sediments in a laboratory experiment using a shallow-water holothurian (Holothuria forskali), and in an in situ experiment using a deep-sea holothurian (Amperima sp.). Both species demonstrated sustained avoidance behaviour, evading contact with contaminated artificial sediment. However, A. sp. demonstrated sustained avoidance of 5mgl -1 copper-contaminated artificial sediment whereas H. forskali demonstrated only temporary avoidance of 5mgl -1 copper-contaminated artificial sediment, suggesting that H. forskali may be more tolerant of metal exposure over 96h. Nonetheless, the acute behavioural response appears consistent between the shallow-water species and the deep-sea species, suggesting that H. forskali may be a suitable ecotoxicological proxy for A. sp. in acute (≤24h) exposures, which may be representative of deep-sea mining impacts. No antioxidant response was observed in either species, which was interpreted to be the consequence of avoiding copper exposure. Although these data suggest that shallow-water taxa may be suitable ecotoxicological proxies for deep-sea taxa, differences in methodological and analytical approaches, and in sex and reproductive stage of experimental subjects, require caution in assessing the suitability of H. forskali as an ecotoxicological proxy for A. sp. Nonetheless, avoidance behaviour may have bioenergetic consequences that
Masoumeh Soflaei; Paeiz Azmi
2014-01-01
One of the most important problems of reliable communications in shallow water channels is intersymbol interference (ISI) which is due to scattering from surface and reflecting from bottom. Using adaptive equalizers in receiver is one of the best suggested ways for overcoming this problem. In this paper, we apply the family of selective regressor affine projection algorithms (SR-APA) and the family of selective partial update APA (SPU-APA) which have low computational complexity that is one ...
Castillo-López, Elena; Dominguez, Jose Antonio; Pereda, Raúl; de Luis, Julio Manuel; Pérez, Ruben; Piña, Felipe
2017-10-01
Accurate determination of water depth is indispensable in multiple aspects of civil engineering (dock construction, dikes, submarines outfalls, trench control, etc.). To determine the type of atmospheric correction most appropriate for the depth estimation, different accuracies are required. Accuracy in bathymetric information is highly dependent on the atmospheric correction made to the imagery. The reduction of effects such as glint and cross-track illumination in homogeneous shallow-water areas improves the results of the depth estimations. The aim of this work is to assess the best atmospheric correction method for the estimation of depth in shallow waters, considering that reflectance values cannot be greater than 1.5 % because otherwise the background would not be seen. This paper addresses the use of hyperspectral imagery to quantitative bathymetric mapping and explores one of the most common problems when attempting to extract depth information in conditions of variable water types and bottom reflectances. The current work assesses the accuracy of some classical bathymetric algorithms (Polcyn-Lyzenga, Philpot, Benny-Dawson, Hamilton, principal component analysis) when four different atmospheric correction methods are applied and water depth is derived. No atmospheric correction is valid for all type of coastal waters, but in heterogeneous shallow water the model of atmospheric correction 6S offers good results.
Causal viscous cosmology without singularities
Laciana, Carlos E
2016-01-01
An isotropic and homogeneous cosmological model with a source of dark energy is studied. That source is simulated with a viscous relativistic fluid with minimal causal correction. In this model the restrictions on the parameters coming from the following conditions are analized: a) energy density without singularities along time, b) scale factor increasing with time, c) universe accelerated at present time, d) state equation for dark energy with "w" bounded and close to -1. It is found that those conditions are satified for the following two cases. i) When the transport coefficient ({\\tau}_{{\\Pi}}), associated to the causal correction, is negative, with the aditional restriction {\\zeta}|{\\tau}_{{\\Pi}}|>2/3, where {\\zeta} is the relativistic bulk viscosity coefficient. The state equation is in the "phantom" energy sector. ii) For {\\tau}_{{\\Pi}} positive, in the "k-essence" sector. It is performed an exact calculation for the case where the equation of state is constant, finding that option (ii) is favored in r...
A review of contemporary patterns of endemism for shallow water reef fauna in the Red Sea
DiBattista, Joseph
2015-11-03
Aim The Red Sea is characterised by a unique fauna and historical periods of desiccation, hypersalinity and intermittent isolation. The origin and contemporary composition of reef-associated taxa in this region can illuminate biogeographical principles about vicariance and the establishment (or local extirpation) of existing species. Here we aim to: (1) outline the distribution of shallow water fauna between the Red Sea and adjacent regions, (2) explore mechanisms for maintaining these distributions and (3) propose hypotheses to test these mechanisms. Location Red Sea, Gulf of Aden, Arabian Sea, Arabian Gulf and Indian Ocean. Methods Updated checklists for scleractinian corals, fishes and non-coral invertebrates were used to determine species richness in the Red Sea and the rest of the Arabian Peninsula and assess levels of endemism. Fine-scale diversity and abundance of reef fishes within the Red Sea were explored using ecological survey data. Results Within the Red Sea, we recorded 346 zooxanthellate and azooxanthellate scleractinian coral species of which 19 are endemic (5.5%). Currently 635 species of polychaetes, 211 echinoderms and 79 ascidians have been documented, with endemism rates of 12.6%, 8.1% and 16.5% respectively. A preliminary compilation of 231 species of crustaceans and 137 species of molluscs include 10.0% and 6.6% endemism respectively. We documented 1071 shallow fish species, with 12.9% endemic in the entire Red Sea and 14.1% endemic in the Red Sea and Gulf of Aden. Based on ecological survey data of endemic fishes, there were no major changes in species richness or abundance across 1100 km of Saudi Arabian coastline. Main conclusions The Red Sea biota appears resilient to major environmental fluctuations and is characterized by high rates of endemism with variable degrees of incursion into the Gulf of Aden. The nearby Omani and Arabian Gulfs also have variable environments and high levels of endemism, but these are not consistently distinct
How propeller suction is the dominant factor for ship accidents at shallow water conditions
Acar, Dursun; Alpar, Bedri; Ozeren, Sinan
2017-04-01
The laminar flow comes to the fore with the disappearance of the several other directions in the internal displacements in the water current. Due to the dominant speed direction during the straightforward motion of the ship, the underwater hull is associated with the continuous flow of laminar currents. The open marine environment acts as a compressible liquid medium because of the presence of many variables about water volume overflow boundaries where the ship is associated. Layers of water rising over the sea surface due to ship's body and the propeller's water push provides loss of liquid lifting force for the ship. These situations change the well-known sea-floor morphology and reliable depth limits, and lead to probable accidents. If the ship block coefficient for the front side is 0.7 or higher, the "squat" will be more on the bow, because the associated factor "displacement volume" causes to the low-pressure environment due to large and rapid turbulence. Thus, the bow sinks further, which faced with liquid's weaker lift force. The vessels Gerardus Mercator, Queen Elizabeth and Costa Concordia had accidents because of unified reasons of squat, fast water mass displacement by hull push and propeller suction interaction. In the case of water mass displacement from the bow side away, that accident occurred in 2005 by the vessel Gerardus Mercator with excessive longitudinal trim angularity in the shallow water. The vessel Costa Concordia (2012), voluminous water displaced from the rear left side was an important factor because of the sharp manoeuvre of that the captain made before the accident. Observations before the accident indicate that full-speed sharp turn provided listed position for the ship from left (port side) in the direction of travel before colliding and then strike a rock on the sloping side of the seabed. The reason why the ship drifted to the left depends mainly the water discharge occurred at the left side of the hull during left-hand rudder
National Oceanic and Atmospheric Administration, Department of Commerce — Detailed, shallow-water coral reef ecosystem maps were generated by rule-based, semi-automated image analysis of high-resolution satellite imagery for nine locations...
National Oceanic and Atmospheric Administration, Department of Commerce — Shallow-water, aggregated cover maps were produced by combining as many as four or more detailed habitat types into general cover categories. The original detailed...
Digital Repository Service at National Institute of Oceanography (India)
Raghukumar, C.; Mohandass, C.; Cardigos, F.; De; Santos, R.S.; Colaco, A.
The shallow-water hydrothermal vent of D. Joao de Castro Seamount in the North Atlantic, between the Azorean islands Sao Miguel and Terceira, is characterized by yellow and white zones which are distinct in physical and chemical characteristics...
National Oceanic and Atmospheric Administration, Department of Commerce — Near-shore shallow water Conductivity-Temperature-Depth (CTD) surveys provided vertical profiles of temperature, salinity, and turbidity providing indications for...
National Oceanic and Atmospheric Administration, Department of Commerce — Near-shore shallow water Conductivity-Temperature-Depth (CTD) surveys provided vertical profiles of temperature, salinity, and turbidity providing indications for...
National Oceanic and Atmospheric Administration, Department of Commerce — Near-shore shallow water Conductivity-Temperature-Depth (CTD) surveys provided vertical profiles of temperature, salinity, and turbidity providing indications for...
National Oceanic and Atmospheric Administration, Department of Commerce — Near-shore shallow water Conductivity-Temperature-Depth (CTD) surveys provided vertical profiles of temperature, salinity, and turbidity providing indications for...
National Oceanic and Atmospheric Administration, Department of Commerce — Near-shore shallow water Conductivity-Temperature-Depth (CTD) surveys provided vertical profiles of temperature, salinity, and turbidity providing indications for...
National Oceanic and Atmospheric Administration, Department of Commerce — Shallow-water, aggregated cover maps were produced by combining as many as four or more detailed habitat types into general cover categories. The original detailed...
Green, T. E.; Bramley, A.; Lue, L.; Grassia, P.
2006-11-01
Microscale models of foam structure traditionally incorporate a balance between bubble pressures and surface tension forces associated with curvature of bubble films. In particular, models for flowing foam microrheology have assumed this balance is maintained under the action of some externally imposed motion. Recently, however, a dynamic model for foam structure has been proposed, the viscous froth model, which balances the net effect of bubble pressures and surface tension to viscous dissipation forces: this permits the description of fast-flowing foam. This contribution examines the behavior of the viscous froth model when applied to a paradigm problem with a particularly simple geometry: namely, a two-dimensional bubble “lens.” The lens consists of a channel partly filled by a bubble (known as the “lens bubble”) which contacts one channel wall. An additional film (known as the “spanning film”) connects to this bubble spanning the distance from the opposite channel wall. This simple structure can be set in motion and deformed out of equilibrium by applying a pressure across the spanning film: a rich dynamical behavior results. Solutions for the lens structure steadily propagating along the channel can be computed by the viscous froth model. Perturbation solutions are obtained in the limit of a lens structure with weak applied pressures, while numerical solutions are available for higher pressures. These steadily propagating solutions suggest that small lenses move faster than large ones, while both small and large lens bubbles are quite resistant to deformation, at least for weak applied back pressures. As the applied back pressure grows, the structure with the small lens bubble remains relatively stiff, while that with the large lens bubble becomes much more compliant. However, with even further increases in the applied back pressure, a critical pressure appears to exist for which the steady-state structure loses stability and unsteady
Soliton equations and Hamiltonian systems
Dickey, L A
2002-01-01
The theory of soliton equations and integrable systems has developed rapidly during the last 30 years with numerous applications in mechanics and physics. For a long time, books in this field have not been written but the flood of papers was overwhelming: many hundreds, maybe thousands of them. All this output followed one single work by Gardner, Green, Kruskal, and Mizura on the Korteweg-de Vries equation (KdV), which had seemed to be merely an unassuming equation of mathematical physics describing waves in shallow water. Besides its obvious practical use, this theory is attractive also becau
A preliminary evaluation of shallow-water rhodolith beds in Bahia Magdalena, Mexico
Directory of Open Access Journals (Sweden)
Enrique Ávila
2011-12-01
Full Text Available The aim of the present study was to describe the structure of shallow-water rhodolith beds from Bahia Magdalena, one of the most productive estuarine systems of the Mexican Pacific coasts. From September 2008 to May 2009 four rhodolith beds were found (between 1 and 3 m depth and population descriptors such as rhodolith density, size classes, branch density, volume and weight were determined. The dominant rhodolith forming species was Lithophyllum margaritae. The size of beds ranged from 7,600 to 17,800 m2 approximately with densities from 42.2 to 215.9 ind.m-2. In these beds, L. margaritae shows fruticose and foliose growth forms, from which spherical forms were predominant (81-99%. Branch density (from 3.0 to 13.3 branches.cm-2 varied significantly (p O objetivo do presente estudo foi descrever a estrutura de bancos de rodolitos de áreas rasas da Bahia Magdalena, um dos sistemas estuarinos mais produtivos da costa pacífica mexicana. Quatro bancos de rodolitos situados entre 1 e 3m de profundidade foram avaliados em relação a densidade, classes de tamanho, densidade dos ramos, volume e peso no período de setembro de 2008 a maio de 2009. A espécie dominante no local foi Lithophyllum margaritae. O tamanho dos bancos variou de 7,600 a 17,800 m² aproximadamente, com densidades de 42.2-215.9 ind.m-2 . Foram observadas formas de crescimento fruticosa e folhosa em L. margaritae, sendo a forma esférica predominante (81-99%. A densidade dos ramos (3.0-13.3 ramos.cm-2 variou significativamente (p < 0.05 entre os bancos. O volume médio (2.0-400 ml e o peso úmido (32.4-84.8 g não tiveram diferenças significativas entre os locais, mas uma correlação positiva significativa (r = 0.95, p < 0.05 foi encontrada entre os parâmetros. O tamanho das plantas variou de 2.0 a 11.5 centímetros predominando o padrão entre 40.1-60 mm. As diferenças na densidade de rodolitos, densidade dos ramos e a esfericidade foram atribuídas às condições hidrodin
Kobayashi, Tetsuo; Yokoyama, Daisuke; Ebohara, Kenji; Sonoda, Yasutaka; Sakata, Yoshinobu; Urayama, Kazuki; Cho, Hiroyuki; Yoshikoshi, Hisashi; Kitano, Masaharu
2008-01-01
Two column experiments on the relation between soil texture and salinization in soil profiles with a shallow water table were conducted under rainless conditions using the concept of ECSAT. The buildup of salts due to evaporation from bare soil was confined within the superficial layer and its amount during a period could be assumed to equal the product of the total of evaporation during the period and the salinity of water supplied into the soil profile, such as irrigation water and/or groun...
1991-08-01
Environmental Guide for ASW in Eawrrem Canadian Shallow Waters PW I - An AssemanW of the Suam oc Knowledge By Capt Dsniel Ncramid Accet, ic;i For NTIS C?&I...presented. 3 I Chapter 2 Bottom Features Bottom characteristics such as bathymetry and surficial geology , are crit- ical parameters whcn dealing with the...chart clutter. 2.2.4 Data Set Data source The information on sediment types is contained in a series of surficial geology charts produced jointly by the
Digital Repository Service at National Institute of Oceanography (India)
Mohandass, C.; Rajasabapathy, R.; Ravindran, C.; Colaco, A.; Santos, R.S.; Meena, R.M.
of the Biosphere, 15: 327–345. Bolton D.J., Kelly C.T. & Fogarty W.M. 1997. Purification and characterization of the α-amylase of Bacillus flavothermus. Enzyme and Microbial Technology, 20: 340–343. Cardigos F., Colaco A., Dando P.R., Avila S.P., Sarradin P.... Biol. Mar., vol.53; 2012; 65-76 Bacterial diversity and their adaptations in the shallow water hydrothermal vent at D. João de Castro Seamount (DJCS), Azores, Portugal Chellandi MOHANDASS 1 , Raju RAJASABAPATHY 1 , Chinnarajan RAVINDRAN 1 , Ana...
Numerical solution of boundary layer MHD flow with viscous dissipation.
Mishra, S R; Jena, S
2014-01-01
The present paper deals with a steady two-dimensional laminar flow of a viscous incompressible electrically conducting fluid over a shrinking sheet in the presence of uniform transverse magnetic field with viscous dissipation. Using suitable similarity transformations the governing partial differential equations are transformed into ordinary differential equations and then solved numerically by fourth-order Runge-Kutta method with shooting technique. Results for velocity and temperature profiles for different values of the governing parameters have been discussed in detail with graphical representation. The numerical evaluation of skin friction and Nusselt number are also given in this paper.
Investigation of Boundary Effects on the Natural Cavitating Flow around a 2D Wedge in Shallow Water
Directory of Open Access Journals (Sweden)
Xin Chen
2011-01-01
Full Text Available When a cavitated body moves in shallow water, both flexible free surface and rigid bottom wall will produce great influence on the cavity pattern and hydrodynamics to change the motion attitude and stability of the body. In this paper, a single-fluid multiphase flow method coupled with a natural cavitation model was employed to study the effects of two kinds of boundaries on the natural cavitating flow around a two-dimensional symmetry wedge in shallow water. Within the range of the cavitation number for computation (0.05 ~ 2.04, the cavity pattern would be divided into three types, namely, stable type, transition type and wake-vortex type. The shape of the free surface is fairly similar to that of the cavity's upper surface with well right-and-left symmetry. However, when the immersion depth and the cavitation number are decreasing, the symmetry of the cavity shape is destroyed due to the influence of bottom wall effects. When the cavitation number is less than about 0.1, with the immersion depth going down, free surface effects exerts a stronger influence on the drag coefficient of this 2D wedge, whereas wall effects bring a stronger influence on the lift coefficient.
Haxel, Joseph H; Dziak, Robert P; Matsumoto, Haru
2013-05-01
A year-long experiment (March 2010 to April 2011) measuring ambient sound at a shallow water site (50 m) on the central OR coast near the Port of Newport provides important baseline information for comparisons with future measurements associated with resource development along the inner continental shelf of the Pacific Northwest. Ambient levels in frequencies affected by surf-generated noise (f < 100 Hz) characterize the site as a high-energy end member within the spectrum of shallow water coastal areas influenced by breaking waves. Dominant sound sources include locally generated ship noise (66% of total hours contain local ship noise), breaking surf, wind induced wave breaking and baleen whale vocalizations. Additionally, an increase in spectral levels for frequencies ranging from 35 to 100 Hz is attributed to noise radiated from distant commercial ship commerce. One-second root mean square (rms) sound pressure level (SPLrms) estimates calculated across the 10-840 Hz frequency band for the entire year long deployment show minimum, mean, and maximum values of 84 dB, 101 dB, and 152 dB re 1 μPa.
Directory of Open Access Journals (Sweden)
Masoumeh Soflaei
2014-01-01
Full Text Available One of the most important problems of reliable communications in shallow water channels is intersymbol interference (ISI which is due to scattering from surface and reflecting from bottom. Using adaptive equalizers in receiver is one of the best suggested ways for overcoming this problem. In this paper, we apply the family of selective regressor affine projection algorithms (SR-APA and the family of selective partial update APA (SPU-APA which have low computational complexity that is one of the important factors that influences adaptive equalizer performance. We apply experimental data from Strait of Hormuz for examining the efficiency of the proposed methods over shallow water channel. We observe that the values of the steady-state mean square error (MSE of SR-APA and SPU-APA decrease by 5.8 (dB and 5.5 (dB, respectively, in comparison with least mean square (LMS algorithm. Also the families of SPU-APA and SR-APA have better convergence speed than LMS type algorithm.
Conde, Daniel; Canelas, Ricardo B.; Ferreira, Rui M. L.
2017-04-01
One of the most common challenges in hydrodynamic modelling is the trade off one must make between highly resolved simulations and the time required for their computation. In the particular case of urban floods, modelers are often forced to simplify the complex geometries of the problem, or to implicitly include some of its hydrodynamic effects, due to the typically very large spatial scales involved and limited computational resources. At CEris - Instituto Superior Técnico, Universidade de Lisboa - the STAV-2D shallow-water model, particularly suited for strong transient flows in complex and dynamic geometries, has been under development for the past recent years (Canelas et al., 2013 & Conde et al., 2013). The model is based on an explicit, first-order 2DH finite-volume discretization scheme for unstructured triangular meshes, in which a flux-splitting technique is paired with a reviewed Roe-Riemann solver, yielding a model applicable to discontinuous flows over time-evolving geometries. STAV-2D features solid transport in both Euleran and Lagrangian forms, with the first aiming at describing the transport of fine natural sediments and the latter aimed at large individual debris. The model has been validated with theoretical solutions and laboratory experiments (Canelas et al., 2013 & Conde et al., 2015). This work presents our most recent effort in STAV-2D: the re-design of the code in a modern Object-Oriented parallel framework for heterogeneous computations in CPUs and GPUs. The programming language of choice for this re-design was C++, due to its wide support of established and emerging parallel programming interfaces. The current implementation of STAV-2D provides two different levels of parallel granularity: inter-node and intra-node. Inter-node parallelism is achieved by distributing a simulation across a set of worker nodes, with communication between nodes being explicitly managed through MPI. At this level, the main difficulty is associated with the
Solitons of shallow-water models from energy-dependent spectral problems
Haberlin, Jack; Lyons, Tony
2018-01-01
The current work investigates the soliton solutions of the Kaup-Boussinesq equation using the inverse scattering transform method. We outline the construction of the Riemann-Hilbert problem for a pair of energy-dependent spectral problems for the system, which we then use to construct the solution of this hydrodynamic system.
Three-Dimensional Shallow Water Adaptive Hydraulics (ADH-SW3): Turbulence Closure
2015-06-01
CH3D, TABS-MDS) exist. These models solve some form of the Reynolds-averaged Navier- Stokes equations using the hydrostatic assumption. The governing...American Meteorological Society 34: 693–698. Mellor, G. L., and T. Yamada. 1982. Development of a turbulence closure model for geophysical fluid
Agglomeration multigrid for viscous turbulent flows
Mavriplis, D. J.; Venkatakrishnan, V.
1994-01-01
Agglomeration multigrid, which has been demonstrated as an efficient and automatic technique for the solution of the Euler equations on unstructured meshes, is extended to viscous turbulent flows. For diffusion terms, coarse grid discretizations are not possible, and more accurate grid transfer operators are required as well. A Galerkin coarse grid operator construction and an implicit prolongation operator are proposed. Their suitability is evaluated by examining their effect on the solution of Laplace's equation. The resulting strategy is employed to solve the Reynolds-averaged Navier-Stokes equations for aerodynamic flows. Convergence rates comparable to those obtained by a previously developed non-nested mesh multigrid approach are demonstrated, and suggestions for further improvements are given.
Boussinesq evolution equations
DEFF Research Database (Denmark)
Bredmose, Henrik; Schaffer, H.; Madsen, Per A.
2004-01-01
This paper deals with the possibility of using methods and ideas from time domain Boussinesq formulations in the corresponding frequency domain formulations. We term such frequency domain models "evolution equations". First, we demonstrate that the numerical efficiency of the deterministic...... Boussinesq evolution equations of Madsen and Sorensen [Madsen, P.A., Sorensen, O.R., 1993. Bound waves and triad interactions in shallow water. Ocean Eng. 20 359-388] can be improved by using Fast Fourier Transforms to evaluate the nonlinear terms. For a practical example of irregular waves propagating over...... a submerged bar, it is demonstrated that evolution equations utilising FFT can be solved around 100 times faster than the corresponding time domain model. Use of FFT provides an efficient bridge between the frequency domain and the time domain. We utilise this by adapting the surface roller model for wave...
2010-10-01
Space Sciences University of Washington 63 Johnson Hall Box 351310 Seattle, WA 98195 Robert I. Odom Applied Physics Laboratory University of Washington...general cubic equation (first published by the Italian mathematician Girolamo Cardano in 1545, English translation published by M.I.T. Press, 1968), it...Soukup, Darin J., Earth and Space Sciences Dept, Univ. of Washington; Odom, Robert I., Applied Physics Laboratory, Univ. of Washington; Park
Langlois, William E
2014-01-01
Leonardo wrote, 'Mechanics is the paradise of the mathematical sciences, because by means of it one comes to the fruits of mathematics' ; replace 'Mechanics' by 'Fluid mechanics' and here we are." - from the Preface to the Second Edition Although the exponential growth of computer power has advanced the importance of simulations and visualization tools for elaborating new models, designs and technologies, the discipline of fluid mechanics is still large, and turbulence in flows remains a challenging problem in classical physics. Like its predecessor, the revised and expanded Second Edition of this book addresses the basic principles of fluid mechanics and solves fluid flow problems where viscous effects are the dominant physical phenomena. Much progress has occurred in the nearly half a century that has passed since the edition of 1964. As predicted, aspects of hydrodynamics once considered offbeat have risen to importance. For example, the authors have worked on problems where variations in viscosity a...
Viscous flows the practical use of theory
Brenner, Howard
1988-01-01
Representing a unique approach to the study of fluid flows, Viscous Flows demonstrates the utility of theoretical concepts and solutions for interpreting and predicting fluid flow in practical applications. By critically comparing all relevant classes of theoretical solutions with experimental data and/or general numerical solutions, it focuses on the range of validity of theoretical expressions rather than on their intrinsic character.This book features extensive use of dimensional analysis on both models and variables, and extensive development of theoretically based correlating equations.
Shallow Water Acoustic Experiments and Preliminary Planning for FY06 Fieldwork
2011-03-21
H. Levine and J. Schwinger, "On the radiation of sound from an unflanged circular pipe," J. Acoust. Soc. Am. 73, 383-405 (1948). I5F. B. Jensen ...Theory of Wave Propagation (Prentice-Hall, Englewood Cliffs, NJ, 1994). I7R. H. Hardin and F. D. Tappert, "Applications of the split-step Fourier...dimensional para- bolic equation acoustical propagation code," Woods Hole Oceanogr. Inst., Woods Hole, MA, Tech. Rep. WHOI-2006-041, 2006. [21] R. H. Hardin
Axially Symmetric Bianchi Type-I Bulk-Viscous Cosmological ...
Indian Academy of Sciences (India)
Abstract. The present study deals with spatially homogeneous and anisotropic axially symmetric Bianchi type-I cosmological model with time variable cosmological term in the presence of bulk viscous fluid. The Einstein's field equations are solved explicitly by time varying decel- eration parameter q. Consequences of the ...
A simple interaction law for viscous-inviscid interaction
Veldman, Arthur E. P.
2009-01-01
The viscous-inviscid interaction (VII) philosophy for modelling aerodynamic boundary layers is discussed. 'Traditionally' the shear-layer equations are solved with pressure prescribed by the inviscid flow, but then the solution breaks down in a singularity related to flow separation. In the
Second law analysis of a reacting temperature dependent viscous ...
African Journals Online (AJOL)
In this paper, entropy generation during the flow of a reacting viscous fluid through an inclined Channel with isothermal walls are investigated. The coupled energy and momentum equations were solved numerically. Previous results in literature (Adesanya et al 2006 [[17]) showed both velocity and temperature have two ...
Accounting For Compressibility In Viscous Flow In Pipes
Steinle, Frank W.; Gee, Ken; Murthy, Sreedhara V.
1991-01-01
Method developed to account for effects of compressibility in viscous flows through long, circular pipes of uniform diameter. Based on approximation of variations in density and velocity across pipe cross section by profile equations developed for boundary-layer flow between flat plates.
Thermosolutal MHD flow and radiative heat transfer with viscous ...
African Journals Online (AJOL)
This paper investigates double diffusive convection MHD flow past a vertical porous plate in a chemically active fluid with radiative heat transfer in the presence of viscous work and heat source. The resulting nonlinear dimensionless equations are solved by asymptotic analysis technique giving approximate analytic ...
An update on projection methods for transient incompressible viscous flow
Energy Technology Data Exchange (ETDEWEB)
Gresho, P.M.; Chan, S.T.
1995-07-01
Introduced in 1990 was the biharmonic equation (for the pressure) and the concomitant biharmonic miracle when transient incompressible viscous flow is solved approximately by a projection method. Herein is introduced the biharmonic catastrophe that sometimes occurs with these same projection methods.
Thermosolutal MHD flow and radiative heat transfer with viscous ...
African Journals Online (AJOL)
porous plate in a chemically active fluid with radiative heat transfer in the presence of viscous work and heat source. The resulting nonlinear dimensionless equations are solved by asymptotic analysis technique giving approximate analytic solutions for the steady velocity, temperature and concentration. The parameters ...
Directory of Open Access Journals (Sweden)
Carmelo Nasello
2016-01-01
Full Text Available A new small drifter prototype for measuring current immediately below the free surface in a water basin is proposed in this paper. The drifter dimensions make it useful for shallow water applications. The drifter transmits its GPS location via GSM phone network. The drifter was used to study the trajectory of the surface current in the Muggia bay, the latter containing the industrial harbor of the city of Trieste (Italy. The analysis has been carried out under a wide variety of wind conditions. As regards the behavior of the drifter, the analysis has shown that it is well suited to detect the water current since its motion is marginally affected by the wind. The study has allowed detecting the main features of the surface circulation within the Muggia bay under different meteorological conditions. Also, the study has shown that the trajectory of the surface current within the bay is weakly affected by the Coriolis force.
Nonlinear-dispersive mechanism of the freak wave formation in shallow water
Pelinovsky, Efim; Talipova, Tatiana; Kharif, Christian
2000-12-01
The mechanism of the freak wave formation related to the spatial-temporal focusing is studied within the framework of the Korteweg-de Vries equation. A method to find the wave trains whose evolution leads to the freak wave formation is proposed. It is based on the solution of the Korteweg-de Vries equation with an initial condition corresponding to the expected freak wave. All solutions of this Cauchy problem by the reversal of abscissa represent the possible forms of wave trains which evolve into the freak wave. It is found that freak waves are almost linear waves, and their characteristic Ursell parameter is small. The freak wave formation is possible also from the random wave field and the numerical simulation describes the details of this phenomenon. It is shown that freak waves can be generated not only for specific conditions, but also for relative wide classes of the wave trains. This mechanism explains the rare and short-lived character of the freak wave.
Zhao, Dehua; Wang, Penghe; Zuo, Jie; Zhang, Hui; An, Shuqing; Ramesh, Reddy K
2017-08-01
Numerous drought indices have been developed over the past several decades. However, few studies have focused on the suitability of indices for studies of ephemeral wetlands. The objective is to answer the following question: can the traditional large-scale drought indices characterize drought severity in shallow water wetlands such as the Everglades? The question was approached from two perspectives: the available water quantity and the response of wetland ecosystems to drought. The results showed the unsuitability of traditional large-scale drought indices for characterizing the actual available water quantity based on two findings. (1) Large spatial variations in precipitation (P), potential evapotranspiration (PE), water table depth (WTD) and the monthly water storage change (SC) were observed in the Everglades; notably, the spatial variation in SC, which reflects the monthly water balance, was 1.86 and 1.62 times larger than the temporal variation between seasons and between years, respectively. (2) The large-scale water balance measured based on the water storage variation had an average indicating efficiency (IE) of only 60.01% due to the redistribution of interior water. The spatial distribution of variations in the Normalized Different Vegetation Index (NDVI) in the 2011 dry season showed significantly positive, significantly negative and weak correlations with the minimum WTD in wet prairies, graminoid prairies and sawgrass wetlands, respectively. The significant and opposite correlations imply the unsuitability of the traditional large-scale drought indices in evaluating the effect of drought on shallow water wetlands. Copyright © 2017 Elsevier Ltd. All rights reserved.
Medvedev, Kirill E; Alemasov, Nikolay A; Vorobjev, Yuri N; Boldyreva, Elena V; Kolchanov, Nikolay A; Afonnikov, Dmitry A
2014-10-15
The identification of the mechanisms of adaptation of protein structures to extreme environmental conditions is a challenging task of structural biology. We performed molecular dynamics (MD) simulations of the Nip7 protein involved in RNA processing from the shallow-water (P. furiosus) and the deep-water (P. abyssi) marine hyperthermophylic archaea at different temperatures (300 and 373 K) and pressures (0.1, 50 and 100 MPa). The aim was to disclose similarities and differences between the deep- and shallow-sea protein models at different temperatures and pressures. The current results demonstrate that the 3D models of the two proteins at all the examined values of pressures and temperatures are compact, stable and similar to the known crystal structure of the P. abyssi Nip7. The structural deviations and fluctuations in the polypeptide chain during the MD simulations were the most pronounced in the loop regions, their magnitude being larger for the C-terminal domain in both proteins. A number of highly mobile segments the protein globule presumably involved in protein-protein interactions were identified. Regions of the polypeptide chain with significant difference in conformational dynamics between the deep- and shallow-water proteins were identified. The results of our analysis demonstrated that in the examined ranges of temperatures and pressures, increase in temperature has a stronger effect on change in the dynamic properties of the protein globule than the increase in pressure. The conformational changes of both the deep- and shallow-sea protein models under increasing temperature and pressure are non-uniform. Our current results indicate that amino acid substitutions between shallow- and deep-water proteins only slightly affect overall stability of two proteins. Rather, they may affect the interactions of the Nip7 protein with its protein or RNA partners.
Viscous dissipation effects on heat transfer in flow past a continuous moving plate
Digital Repository Service at National Institute of Oceanography (India)
Soundalgekar, V.M.; Murty, T.V.R.
The study of thermal boundary layer on taking into account the viscous dissipative heat, on a continuously moving semi-infinite flat plate is presented here.Similarity solutions are derived and the resulting equations are integrated numerically...
Al Sawaf, Mohamad Basel; Kawanisi, Kiyosi; Kagami, Junya; Bahreinimotlagh, Masoud; Danial, Mochammad Meddy
2017-10-01
The aim of this study is to investigate the scaling exponent properties of mountainous river flow fluctuations by detrended fluctuation analysis (DFA). Streamflow data were collected continuously using Fluvial Acoustic Tomography System (FATS), which is a novel system for measuring continuous streamflow at high-frequency scales. The results revealed that river discharge fluctuations have two scaling regimes and scaling break. In contrast to the Ranting Curve method (RC), the small-scale exponent detected by the FATS is estimated to be 1.02 ± 0.42% less than that estimated by RC. More importantly, the crossover times evaluated from the FATS delayed approximately by 42 ± 21 hr ≈2-3 days than their counterparts estimated by RC. The power spectral density analysis assists our findings. We found that scaling characteristics information evaluated for a river using flux data obtained by RC approach might not be accurately detected, because this classical method assumes that flow in river is steady and depends on constructing a relationship between discharge and water level, while the discharge obtained by the FATS decomposes velocity and depth into two ratings according to the continuity equation. Generally, this work highlights the performance of FATS as a powerful and effective approach for continuous streamflow measurements at high-frequency levels.
FLRW viscous cosmological models
Khadekar, G S; Meng, X -H
2016-01-01
In this paper we solve Friedmann equations by considering a universal media as a non-perfect fluid with bulk viscosity and is described by a general "gamma law" equation of state of the form $p= (\\gamma -1) \\rho + \\Lambda(t)$, where the adiabatic parameter $\\gamma$ varies with scale factor $R$ of the metric and $\\Lambda$ is the time dependent cosmological constant. A unified description of the early evolution of the universe is presented by assuming the bulk viscosity and cosmological parameter in a linear combination of two terms of the form: $\\Lambda(t)=\\Lambda_{0} + \\Lambda_{1}\\frac{\\dot{R}}{R}$ and $\\zeta = \\zeta_{0} + \\zeta_{1} \\frac{\\dot{R}}{R}$, where $\\Lambda_{0},\\;\\Lambda_{1},\\, \\zeta_{0}$ and $ \\zeta_{1}$ are constants, in which an inflationary phase is followed by the radiation dominated phase. For this general gamma law equation of state, an entirely integrable dynamical equation to the scale factor $R$ is obtained along with its exact solutions. In this framework we demonstrate that the model can...
Wang, Li; Cheung, Man Kit; Liu, Rulong; Wong, Chong Kim; Kwan, Hoi Shan; Hwang, Jiang-Shiou
2017-04-01
Shallow-water hydrothermal vents (HTVs) are an ecologically important habitat with a geographic origin similar to that of deep-sea HTVs. Studies on shallow-water HTVs have not only facilitated understanding of the influences of vents on local ecosystems but also helped to extend the knowledge on deep-sea vents. In this study, the diversity of bacterial communities in the sediments of shallow-water HTVs off Kueishan Island, Taiwan, was investigated by examining the 16S ribosomal RNA gene as well as key functional genes involved in chemoautotrophic carbon fixation (aclB, cbbL and cbbM). In the vent area, Sulfurovum and Sulfurimonas of Epsilonproteobacteria appeared to dominate the benthic bacterial community. Results of aclB gene analysis also suggested involvement of these bacteria in carbon fixation using the reductive tricarboxylic acid (rTCA) cycle. Analysis of the cbbM gene showed that Alphaproteobacterial members such as the purple non-sulfur bacteria were the major chemoautotrophic bacteria involving in carbon fixation via the Calvin-Benson-Bassham (CBB) cycle. However, they only accounted for cycle is the major chemoautotrophic carbon fixation pathway in sediments of the shallow-water HTVs off Kueishan Island.
Fontijn, H.L.
1975-01-01
This report gives information about the hydrodynamic coefficients of a box-shaped ship with zero speed of advance in case of pure swaying and yawing on shallow water. In the horizontal plane a harmonically oscillating motion is imposed on the ship; the hydrodynamic coefficients for the modes of
Morris, J P; Thatje, S; Ravaux, J; Shillito, B; Fernando, D; Hauton, C
2015-03-01
Little is known about the ecological and physiological processes governing depth distribution limits in species. Temperature and hydrostatic pressure are considered to be two dominant factors. Research has shown that some marine ectotherms are shifting their bathymetric distributions in response to rapid anthropogenic ocean surface warming. Shallow-water species unable to undergo latitudinal range shifts may depend on bathymetric range shifts to seek refuge from warming surface waters. As a first step in constraining the molecular basis of pressure tolerance in shallow water crustaceans, we examined differential gene expression in response to acute pressure and temperature exposures in juveniles of the shallow-water shrimp Palaemonetes varians. Significant increases in the transcription of genes coding for an NMDA receptor-regulated protein, an ADP ribosylation factor, β-actin, two heat shock protein 70 kDa isoforms (HSP70), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were found in response to elevated pressure. NMDA receptors have been implicated in pathways of excitotoxic damage to neurons and the onset of high pressure neurological syndrome (HPNS) in mammals. These data indicate that the sub-lethal effects of acute barotrauma are associated with transcriptional disturbances within the nervous tissue of crustaceans, and cellular macromolecular damage. Such transcriptional changes lead to the onset of symptoms similar to that described as HPNS in mammals, and may act as a limit to shallow water organisms' prolonged survival at depth. Copyright © 2014 Elsevier Inc. All rights reserved.
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S Emil Ruff
2016-03-01
Full Text Available The anaerobic oxidation of methane (AOM is a key biogeochemical process regulating methane emission from marine sediments into the hydrosphere. AOM is largely mediated by consortia of anaerobic methanotrophic archaea (ANME and sulfate-reducing bacteria (SRB, and has mainly been investigated in deep-sea sediments. Here we studied methane seepage at four spots located at 12 m water depth in coastal, organic-carbon depleted permeable sands off the Island of Elba (Italy. We combined biogeochemical measurements, sequencing-based community analyses and in situ hybridization to investigate the microbial communities of this environment. Increased alkalinity, formation of free sulfide and nearly stoichiometric methane oxidation and sulfate reduction rates up to 200 nmol g-1 day-1 indicated the predominance of sulfate-coupled AOM. With up to 40 cm thickness the zones of AOM activity were unusually large and occurred in deeper sediment horizons (20–50 cm below seafloor as compared to diffusion-dominated deep-sea seeps, which is likely caused by advective flow of pore water due to the shallow water depth and permeability of the sands. Hydrodynamic forces also may be responsible for the substantial phylogenetic and unprecedented morphological diversity of AOM consortia inhabiting these sands, including the clades ANME-1a/b, ANME-2a/b/c, ANME-3 and their partner bacteria SEEP-SRB1a and SEEP-SRB2. High microbial dispersal, the availability of diverse energy sources and high habitat heterogeneity might explain that the emission spots shared few microbial taxa, despite their physical proximity. Although the biogeochemistry of this shallow methane seep was very different to that of deep-sea seeps, their key functional taxa were very closely related, which supports the global dispersal of key taxa and underlines strong selection by methane as the predominant energy source. Mesophilic, methane-fueled ecosystems in shallow-water permeable sediments may comprise
Taboada, Sergi; Riesgo, Ana; Bas, Maria; Arnedo, Miquel A; Cristobo, Javier; Rouse, Greg W; Avila, Conxita
2015-01-01
Osedax, commonly known as bone-eating worms, are unusual marine annelids belonging to Siboglinidae and represent a remarkable example of evolutionary adaptation to a specialized habitat, namely sunken vertebrate bones. Usually, females of these animals live anchored inside bone owing to a ramified root system from an ovisac, and obtain nutrition via symbiosis with Oceanospirillales gamma-proteobacteria. Since their discovery, 26 Osedax operational taxonomic units (OTUs) have been reported from a wide bathymetric range in the Pacific, the North Atlantic, and the Southern Ocean. Using experimentally deployed and naturally occurring bones we report here the presence of Osedax deceptionensis at very shallow-waters in Deception Island (type locality; Antarctica) and at moderate depths near South Georgia Island (Subantarctic). We present molecular evidence in a new phylogenetic analysis based on five concatenated genes (28S rDNA, Histone H3, 18S rDNA, 16S rDNA, and cytochrome c oxidase I-COI-), using Maximum Likelihood and Bayesian inference, supporting the placement of O. deceptionensis as a separate lineage (Clade VI) although its position still remains uncertain. This phylogenetic analysis includes a new unnamed species (O. 'mediterranea') recently discovered in the shallow-water Mediterranean Sea belonging to Osedax Clade I. A timeframe of the diversification of Osedax inferred using a Bayesian framework further suggests that Osedax diverged from other siboglinids during the Middle Cretaceous (ca. 108 Ma) and also indicates that the most recent common ancestor of Osedax extant lineages dates to the Late Cretaceous (ca. 74.8 Ma) concomitantly with large marine reptiles and teleost fishes. We also provide a phylogenetic framework that assigns newly-sequenced Osedax endosymbionts of O. deceptionensis and O. 'mediterranea' to ribospecies Rs1. Molecular analysis for O. deceptionensis also includes a COI-based haplotype network indicating that individuals from Deception
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Sergi Taboada
Full Text Available Osedax, commonly known as bone-eating worms, are unusual marine annelids belonging to Siboglinidae and represent a remarkable example of evolutionary adaptation to a specialized habitat, namely sunken vertebrate bones. Usually, females of these animals live anchored inside bone owing to a ramified root system from an ovisac, and obtain nutrition via symbiosis with Oceanospirillales gamma-proteobacteria. Since their discovery, 26 Osedax operational taxonomic units (OTUs have been reported from a wide bathymetric range in the Pacific, the North Atlantic, and the Southern Ocean. Using experimentally deployed and naturally occurring bones we report here the presence of Osedax deceptionensis at very shallow-waters in Deception Island (type locality; Antarctica and at moderate depths near South Georgia Island (Subantarctic. We present molecular evidence in a new phylogenetic analysis based on five concatenated genes (28S rDNA, Histone H3, 18S rDNA, 16S rDNA, and cytochrome c oxidase I-COI-, using Maximum Likelihood and Bayesian inference, supporting the placement of O. deceptionensis as a separate lineage (Clade VI although its position still remains uncertain. This phylogenetic analysis includes a new unnamed species (O. 'mediterranea' recently discovered in the shallow-water Mediterranean Sea belonging to Osedax Clade I. A timeframe of the diversification of Osedax inferred using a Bayesian framework further suggests that Osedax diverged from other siboglinids during the Middle Cretaceous (ca. 108 Ma and also indicates that the most recent common ancestor of Osedax extant lineages dates to the Late Cretaceous (ca. 74.8 Ma concomitantly with large marine reptiles and teleost fishes. We also provide a phylogenetic framework that assigns newly-sequenced Osedax endosymbionts of O. deceptionensis and O. 'mediterranea' to ribospecies Rs1. Molecular analysis for O. deceptionensis also includes a COI-based haplotype network indicating that individuals from
Taboada, Sergi; Riesgo, Ana; Bas, Maria; Arnedo, Miquel A.; Cristobo, Javier; Rouse, Greg W.; Avila, Conxita
2015-01-01
Osedax, commonly known as bone-eating worms, are unusual marine annelids belonging to Siboglinidae and represent a remarkable example of evolutionary adaptation to a specialized habitat, namely sunken vertebrate bones. Usually, females of these animals live anchored inside bone owing to a ramified root system from an ovisac, and obtain nutrition via symbiosis with Oceanospirillales gamma-proteobacteria. Since their discovery, 26 Osedax operational taxonomic units (OTUs) have been reported from a wide bathymetric range in the Pacific, the North Atlantic, and the Southern Ocean. Using experimentally deployed and naturally occurring bones we report here the presence of Osedax deceptionensis at very shallow-waters in Deception Island (type locality; Antarctica) and at moderate depths near South Georgia Island (Subantarctic). We present molecular evidence in a new phylogenetic analysis based on five concatenated genes (28S rDNA, Histone H3, 18S rDNA, 16S rDNA, and cytochrome c oxidase I–COI–), using Maximum Likelihood and Bayesian inference, supporting the placement of O. deceptionensis as a separate lineage (Clade VI) although its position still remains uncertain. This phylogenetic analysis includes a new unnamed species (O. ‘mediterranea’) recently discovered in the shallow-water Mediterranean Sea belonging to Osedax Clade I. A timeframe of the diversification of Osedax inferred using a Bayesian framework further suggests that Osedax diverged from other siboglinids during the Middle Cretaceous (ca. 108 Ma) and also indicates that the most recent common ancestor of Osedax extant lineages dates to the Late Cretaceous (ca. 74.8 Ma) concomitantly with large marine reptiles and teleost fishes. We also provide a phylogenetic framework that assigns newly-sequenced Osedax endosymbionts of O. deceptionensis and O. ‘mediterranea’ to ribospecies Rs1. Molecular analysis for O. deceptionensis also includes a COI-based haplotype network indicating that individuals from
Guerra, Melania
Sound in the ocean originates from multiple mechanisms, both natural and anthropogenic. Collectively, underwater ambient noise accumulates valuable information about both its sources and the oceanic environment that propagates this noise. Characterizing the features of ambient noise source mechanisms is challenging, but essential, for properly describing an acoustic environment. Disturbances to a local acoustic environment may affect many aquatic species that have adapted to be heavily dependent on this particular sense for survival functions. In the case of marine mammals, which are federally protected, demand exists for understanding such potential impacts, which drives important scientific efforts that utilize passive acoustic monitoring (PAM) tools to inform regulatory decisions. This dissertation presents two independent studies that use PAM data to investigate the characteristics of source mechanisms that dominate ambient noise in two diverse shallow water environments. The study in Chapter 2 directly addresses the concern of how anthropogenic activities can degrade the effectiveness of PAM. In the Alaskan Beaufort Sea, an environment where ambient noise is normally dominated by natural causes, seismic surveys create impulsive sounds to map the composition of the bottom. By inspecting single-sensor PAM data, the spectral characteristics of seismic survey airgun reverberation are measured, and their contribution to the overall ambient noise is quantified. This work is relevant to multiple ongoing mitigation protocols that rely on PAM to acoustically detect marine mammal presence during industrial operations. Meanwhile, Chapter 3 demonstrates that by analyzing data from multiple PAM sensors, features embedded in both directional and omnidirectional ambient noise can be used to develop new time-synchronization processing techniques for aligning autonomous elements of an acoustic array, a tool commonly used in PAM for detecting and tracking marine mammals. Using
Nakata, Haruhiko; Kannan, Kurunthachalam; Nasu, Tetsuya; Cho, Hyeon-Seo; Sinclair, Ewan; Takemurai, Akira
2006-08-15
Perfluorinated compounds (PFCs), such as perfluorooctane sulfonate (PFOS), perfluorooctanoate (PFOA), perfluorononanoate (PFNA), perfluorohexane sulfonate (PFHS), and perfluorooctane sulfonamide (PFOSA) are widely distributed in aquatic ecosystems. Despite studies reporting the occurrence of PFCs in aquatic organisms, the fate of PFCs in tidal flat and marine coastal ecosystems is not known. In this study, we determined concentrations of PFOS, PFOA, PFNA, PFHS, and PFOSA in sediments; benthic organisms, including lugworm, mussel, crab, clam, oyster, and mudskipper fish from tidal flat; and shallow water species, such as filefish, bream, flounder, shark, finless porpoise, gull, and mallard collected from the Ariake Sea, Japan. PFOS and PFOA were detected in most of the samples analyzed, followed by PFNA, PFOSA, and PFHS. In shallow water species, PFOS was the dominant contaminant, and elevated concentrations were found in higher trophic level species, such as marine mammals and omnivorous birds. These results suggest biomagnification of PFOS through the coastal food chain. In contrast, PFOA was the most abundant compound in tidal flat organisms and sediments. PFOA concentrations in sediments, lugworms, and omnivorous mudskippers in tidal flat were approximately 1 order of magnitude greater than the levels of PFOS. This indicates differences in exposure pattern and bioavailability of PFOS and PFOA between shallow water and tidal flat organisms. The accumulation profiles of PFCs were compared with those of organochlorines (polychlorinated biphenyls, PCB), organotin (tributyltin,TBT), and polycyclic aromatic hydrocarbons (PAHs) in tidal flat and shallow water samples collected from the Ariake Sea. Concentrations of PFCs in sediments and in tidal flat organisms were significantly lower than that found for PCBs, TBT, and PAHs. Nevertheless, PFOS concentrations in shallow water species were comparable to and/or significantly greater than those of other classes of
Johnson-Segalman -- Saint-Venant equations for viscoelastic shallow flows in the elastic limit
Boyaval, Sébastien
2016-01-01
The shallow-water equations of Saint-Venant, often used to model the long-wave dynamics of free-surface flows driven by inertia and hydrostatic pressure, can be generalized to account for the elongational rheology of non-Newtonian fluids too. We consider here the $4 \\times 4$ shallow-water equations generalized to viscoelastic fluids using the Johnson-Segalman model in the elastic limit (i.e. at infinitely-large Deborah number, when source terms vanish). The system of nonlinear first-order eq...
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Vivienne R. Johnson
2015-12-01
Full Text Available Predicting the effects of anthropogenic CO2 emissions on coastal ecosystems requires an understanding of the responses of algae, since these are a vital functional component of shallow-water habitats. We investigated microphytobenthic assemblages on rock and sandy habitats along a shallow subtidal pCO2 gradient near volcanic seeps in the Mediterranean Sea. Field studies of natural pCO2 gradients help us understand the likely effects of ocean acidification because entire communities are subjected to a realistic suite of environmental stressors such as over-fishing and coastal pollution. Temperature, total alkalinity, salinity, light levels and sediment properties were similar at our study sites. On sand and on rock, benthic diatom abundance and the photosynthetic standing crop of biofilms increased significantly with increasing pCO2. There were also marked shifts in diatom community composition as pCO2 levels increased. Cyanobacterial abundance was only elevated at extremely high levels of pCO2 (>1400 μatm. This is the first demonstration of the tolerance of natural marine benthic microalgae assemblages to elevated CO2 in an ecosystem subjected to multiple environmental stressors. Our observations indicate that Mediterranean coastal systems will alter as pCO2 levels continue to rise, with increased photosynthetic standing crop and taxonomic shifts in microalgal assemblages.
Terraneo, Tullia Isotta
2017-05-19
Scleractinian corals ascribed to the family Agariciidae represent an important component of Red Sea coral reef fauna, though little genetic data are currently available for this group, and existing information shows polyphyly in the examined mesophotic taxa from the Pacific Ocean. In this work, we provide a first genetic survey of Agariciidae from the Saudi Arabian Red Sea, based on a collection of shallow-water material (<30 m) from the Gulf of Aqaba to the Farasan Islands. Two molecular markers were sequenced to infer morphospecies monophyly and relationships, the intergenic region between COI and 16S rRNA from mitochondrial DNA and the ribosomal ITS1 region from nuclear DNA. A total of 20 morphospecies were identified based on classical macromorphological characters. Six, namely Gardineroseris planulata, Pavona maldivensis, Pavona clavus, Pavona decussata, Leptoseris fragilis, and Leptoseris yabei, were resolved with both DNA loci. The molecular boundaries among the remaining 14 species remain unclear. Our results further confirm that the morphology-based taxonomy of most agariciid species is in disagreement with genetics. In order to disentangle the systematics of these taxa, the inclusion of more sampling locations, additional variable loci, and a micromophological approach are likely needed. Our genetic data represent a first step towards the comparison of biodiversity and connectivity between the Red Sea and the rest of the Indo-Pacific.
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Jeffrey A. Sibaja-Cordero
2012-11-01
Full Text Available Geographic Information Systems (GIS applications used in marine habitats are powerful tools for management and monitoring of marine reserves and resources. Here, we present a series of maps of the soft and hard substrates in the shallow waters (>80 m depth of Parque Nacional Isla del Coco (PNIC= Isla del Coco National Park. We use bathymetry data and field data as input for a GIS, GAM, and kriging methods to generate a series of maps that describe the bottom characteristics. Eight types of bottom were found in the PNIC by composition and grain size. The shore of the island and islets consisted of rocky formations (mainly basalts, with coral reefs in the subtidal of some areas. Rhodolith beds had a dispersing distribution. The bottom on the southern and southwestern region is hard substrate, while sediments cover the northern and northeastern zones. Slightly gravelly sand dominated the bays, while gravelly sand (with more coarse grains was frequent offshore. The inner areas of Chatham and Wafer bays have mud and organic matter. The sediments in the area are mostly carbonates, except in Bahía Yglesias where clastic sediments (from the erosion of basalts are presented. The information generated in this study could be a valuable input for future monitoring in the PNIC.
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Byoung-Joo Jung
2014-10-01
Full Text Available A representer-based variational data assimilation system is newly developed for the spectral element shallow water model in the High Order Method Modeling Environment. This study includes the development of tangent linear and adjoint codes and a background error covariance model. The correctness of the developed codes were checked by various ways such as linearity tests for tangent linear codes, adjoint tests for adjoint codes and symmetric tests for representer functions, which are four-dimensional covariance functions in observation-space. Then, direct and indirect representer-based data assimilation systems were constructed and evaluated by performing a series of identical twin experiments, where synthetic data were obtained from a reference run (nature run and assimilated to correct initial conditions. The characteristics of the covariance model according to the different horizontal scales were evaluated by a suite of single-observation experiments. The results show satisfactory behaviours for both direct and indirect representer-based variational data assimilation methods, which indicates that they are ready to be further developed as a full-fledged four-dimensional variational data assimilation system as next step.
Robertson, Darrel; Wheeler, Lorien; Mathias, Donovan
2017-01-01
If an asteroid is discovered to be on a collision course with Earth and there is insufficient time for a deflection effort to make it miss Earth completely, should it be redirected to a land or ocean impact? While distance from densely populated areas should obviously be maximized, the differing ability of air blast, seismic waves, and tsunami waves to cause damage at distance does not make the choice between land and ocean impacts an immediately obvious one. More broadly this work is a step towards improving damage models from asteroid impacts. This extended abstract follows the hypothetical scenario of the 2017 IAA Planetary Defense Conference where a 100-250m diameter asteroid is on a potential impact course with Earth. A hydrocode was used to simulate impacts into the most sparsely populated areas along the eastern end of the hypothetical impact corridor- specifically in the Gobi Desert, in the shallow waters of the Sea of Japan, and in the deep waters of the Japan Trench in the Pacific Ocean.
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Imane SEBARI
2016-03-01
Full Text Available Morocco is a water-scarce country confronted with a severe dependence on rain-fed agriculture and dwindling groundwater reserves. Since 1995, new water regulation laws and management strategies have been promulgated providing a comprehensive framework for an integrated management. Moreover, water managers should have precise data on the current state of water tables depth in strategic aquifers. Unfortunately, the main source of these data are sporadic wells with no automated monitoring systems making the assessment of water table dynamics, costly, time consuming and out-phased with decision maker needs. In this respect, this paper focuses on the capability of Ground Penetrating Radar to determine the depth of shallow water table in Mnasra region, located in the Gharb region of Morocco as a pilot study to generalize its use in the future for groundwater dynamic monitoring purposes in Morocco. The experiment was undertaken using Mala 800 MHz shielded antennas and was able to probe the depth of the upper fresh water table at 3.75 m deep in the Mnasra aquifer in semi-arid conditions. Data collected by GPR can be used as substitute for well logs to enhance the monitoring of water tables in stressed areas during droughts and excessive recharges during rainy season.
Ren, Shaoran; Liu, Yanmin; Gong, Zhiwu; Yuan, Yujie; Yu, Lu; Wang, Yanyong; Xu, Yan; Deng, Junyu
2018-02-01
In this study, we applied a two-phase flow model to simulate water and sand blowout processes when penetrating shallow water flow (SWF) formations during deepwater drilling. We define `sand' as a pseudo-component with high density and viscosity, which can begin to flow with water when a critical pressure difference is attained. We calculated the water and sand blowout rates and analyzed the influencing factors from them, including overpressure of the SWF formation, as well as its zone size, porosity and permeability, and drilling speed (penetration rate). The obtained data can be used for the quantitative assessment of the potential severity of SWF hazards. The results indicate that overpressure of the SWF formation and its zone size have significant effects on SWF blowout. A 10% increase in the SWF formation overpressure can result in a more than 90% increase in the cumulative water blowout and a 150% increase in the sand blowout when a typical SWF sediment is drilled. Along with the conventional methods of well flow and pressure control, chemical plugging, and the application of multi-layer casing, water and sand blowouts can be effectively reduced by increasing the penetration rate. As such, increasing the penetration rate can be a useful measure for controlling SWF hazards during deepwater drilling.
Pettit, Laura R; Smart, Christopher W; Hart, Malcolm B; Milazzo, Marco; Hall-Spencer, Jason M
2015-05-01
Ocean acidification causes biodiversity loss, alters ecosystems, and may impact food security, as shells of small organisms dissolve easily in corrosive waters. There is a suggestion that photosynthetic organisms could mitigate ocean acidification on a local scale, through seagrass protection or seaweed cultivation, as net ecosystem organic production raises the saturation state of calcium carbonate making seawater less corrosive. Here, we used a natural gradient in calcium carbonate saturation, caused by shallow-water CO2 seeps in the Mediterranean Sea, to assess whether seaweed that is resistant to acidification (Padina pavonica) could prevent adverse effects of acidification on epiphytic foraminifera. We found a reduction in the number of species of foraminifera as calcium carbonate saturation state fell and that the assemblage shifted from one dominated by calcareous species at reference sites (pH ∼8.19) to one dominated by agglutinated foraminifera at elevated levels of CO2 (pH ∼7.71). It is expected that ocean acidification will result in changes in foraminiferal assemblage composition and agglutinated forms may become more prevalent. Although Padina did not prevent adverse effects of ocean acidification, high biomass stands of seagrass or seaweed farms might be more successful in protecting epiphytic foraminifera.
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Michael Delpopi
2015-03-01
Full Text Available Black-band disease (BBD is a persistent disease that cause the decline of the coral reef ecosystems, which is still slightly recorded in Indonesia, including in Pari Island, Thousand Islands. The objectives of this study were to determine progression, prevalence and incidence BBD on Montipora spp in shallow water of Pari Islands. Coral cover were estimated using line intercept transect (LIT whereas the prevalence and incidence of BBD were carried out by using belt transect method with 1 m left and right of tape as long 20 m with 3 replications recorded approximately every two months. BBD progression was documented with a digital photograph method, the photograph of affected area of each coral was taken each day for 2 weeks. BBD was found to be spread in the surveyed area. The result show that prevalence and incidence of BBD showed a positive exponential relationship with water temperature. During the observation Both prevalence and incidence increased on May transitional season (wet-dry. The highest prevalence was found at 5,96 percent and whereas the maximum disease progression found at 0,46 cm/day.
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Carlos E. Paz-Ríos
Full Text Available Tropical coral reefs are known to exhibit high levels of biodiversity. Amphipod crustaceans are successfully adapted to a wide range of marine habitats in coral reefs, but some regions, such as the Campeche Bank in southern Gulf of Mexico, are poorly studied or even unsurveyed for amphipods. To begin to address this paucity of information, the present study records amphipod species from Isla Pérez, an island of the Alacranes Reef National Park, southern Gulf of Mexico. Twenty sites were sampled in the intertidal zone and shallow water adjacent to the island. Thirty-one species of amphipod were identified, 15 of which represented a geographical range extension to the northern Yucatan Peninsula, with four new records for the Mexican south-east sector of the Gulf of Mexico; nine for the Gulf Coast of Mexico; and two for the entire Gulf of Mexico. Significantly, a difference in faunal composition between windward and leeward areas of the intertidal zone was found.
Schmessane, Andrea; Laboratory of matter out equilibrium Team
2012-11-01
Wave localization explains how a perturbation is trapped by the randomness present in a propagation medium. As it propagates, the localized wave amplitude decreases strongly by multiple internal reflections with randomly positioned scatterers, effectively trapping the perturbation inside the random region. The characteristic length where a localized wave is propagated before being extinguish by randomness is called localization length. We carried experiments in a quasi-onedimensional channel with random bottom in a shallow water regime for surface gravity water waves, using a Perfilometry Fourier Transform method, which enables us to obtain global surface measurements. We discuss keys aspects of the control of variables, the experimental setup and the implementation of the measurement method. Thus, we can control, measure and evaluate fundamental variables present in the localization phenomenon such as the type of randomness, scattering intensity and sample length, which allows us to characterize wave localization. We use the scattering matrix method to compare the experimental measurements with theoretical and numerical predictions, using the Lyapunov exponent of the scattering matrix, and discuss their agreement. Conicyt
Ishibashi, Jun-ichiro; Nakaseama, Miwako; Seguchi, Mariko; Yamashita, Toru; Doi, Shinsuke; Sakamoto, Takeaki; Shimada, Kazuhiko; Shimada, Nobutaka; Noguchi, Takuroh; Oomori, Tamotsu; Kusakabe, Minoru; Yamanaka, Toshiro
2008-06-01
Submarine hydrothermal fluid emanation from a small sediment mound associated with bubbling gas was observed in the Wakamiko crater that is located 5 km offshore at 200 m depth in Kagoshima bay, southern Kyushu, Japan. In 2003 and 2005, surface sediments (up to 30 cm) from inside and outside of the hydrothermal mound were sampled using the submersible ROV Hyper-Dolphine (JAMSTEC). Chemistry of pore fluids inside the mound showed a clear difference from those collected from outside the mound, which is explained by mixing of the ascending hydrothermal component and seawater. Estimated chemical composition of the hydrothermal end member suggests that the fluid experienced hydrothermal interaction at a temperature range of about 175 to 200 °C. This is consistent with the observed mound temperature of 137 °C. Hydrothermal minerals such as barite, stibnite, and realgar were identified in the mound sediment, suggesting their precipitation due to mixing of the ascending hydrothermal fluid with seawater. Isotopic composition of the hydrothermal endmember can be explained by mixing product of seawater, magmatic water and meteoric water. The marine shallow-water hydrothermal system in the Wakamiko crater is considered to be driven by a magmatic heat source beneath the crater, which also contributes elements such as arsenic, antimony, mercury and magmatic water to the hydrothermal fluid.
Cea, L; Garrido, M; Puertas, J; Jácome, A; Del Río, H; Suárez, J
2010-01-01
This paper presents the experimental validation and the application to a real industrial catchment of a two-dimensional depth-averaged shallow water model used for the computation of rainfall-runoff transformation from direct precipitation data. Instead of using the common approach in flood inundation modelling, which consists in computing the water depth and velocity fields given the water discharge, in this study the rainfall intensity is imposed directly in the model, the surface runoff being generated automatically. The model considers infiltration losses simultaneously with flow simulation. Gullies are also included in the model, although the coupling between the surface runoff and the sewer network is not considered. Experimental validation of the model is presented in several simplified laboratory configurations of urban catchments, in which the surface runoff has been measured for different hyetographs. The application to a real industrial catchment includes a sewer network flow component, which is solved with the SWMM model. The numerical predictions of the discharge hydrograph generated by a 12 hours storm event are compared with field measurements, providing encouraging results.
Armonies, W.
1989-03-01
Field studies on the occurrence of meiobenthos in the water column above intertidal sandflats have been performed near the Island of Sylt in the northern Wadden Sea. Swimming meiobenthos was strongly dominated by harpacticoid copepods. Many of them have a semiplanktonic life-style. They rest in superficial sediment layers at low tide and swin in the water column at high tide. Swimming activity correlated negatively with light. The abundance in the water column was one order of magnitude higher during the night. Strong currents caused by storm tides significantly decreased meiobenthic abundance in the water column. Light and flow being constant, no significant changes of meiobenthic abundance per unit area occurred over a tidal cycle. Since holoplankton and meroplankton abundances correlated positively with the height of the water column, semiplanktonic meiobenthos may dominate the mesozooplankton in shallow waters. On an average, emergence of meiobenthos increased the mesozooplanktonic biomass by about 2% during diurnal high tides over the entire tidal cycle, and by about 50% during nocturnal high tides. Because of seasonal cycles of the dominant harpacticoids, this high contribution to planktonic biomass may be a summer phenomenon.
Mahanty, Madan M; Latha, G; Thirunavukkarasu, A
2015-06-01
The primary objective of this work was to present the acoustical identification of humpback whales, detected by using an autonomous ambient noise measurement system, deployed in the shallow waters of the Southeastern Arabian Sea (SEAS) during the period January to May 2011. Seven types of sounds were detected. These were characteristically upsweeps and downsweeps along with harmonics. Sounds produced repeatedly in a specific pattern were referred to as phrases (PQRS and ABC). Repeated phrases in a particular pattern were referred to as themes, and from the spectrographic analysis, two themes (I and II) were identified. The variation in the acoustic characteristics such as fundamental frequency, range, duration of the sound unit, and the structure of the phrases and themes are discussed. Sound units were recorded from mid-January to mid-March, with a peak in February, when the mean SST is approx. 28 degree C, and no presence was recorded after mid-March. The temporal and thematic structures strongly determine the functions of the humpback whale song form. Given the use of song in the SEAS, this area is possibly used as an active breeding habitat by humpback whales during the winter season.
Viscous flow and heat transfer over an unsteady stretching surface
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Ene Remus-Daniel
2016-01-01
Full Text Available In this paper we have studied the flow and heat transfer of a horizontal sheet in a viscous fluid. The stretching rate and temperature of the sheet vary with time. The governing equations for momentum and thermal energy are reduced to ordinary differential equations by means of similarity transformation. These equations are solved approximately by means of the Optimal Homotopy Asymptotic Method (OHAM which provides us with a convenient way to control the convergence of approximation solutions and adjust convergence rigorously when necessary. Some examples are given and the results obtained reveal that the proposed method is effective and easy to use.
Adams, Jordan M.; Gasparini, Nicole M.; Hobley, Daniel E. J.; Tucker, Gregory E.; Hutton, Eric W. H.; Nudurupati, Sai S.; Istanbulluoglu, Erkan
2017-04-01
Representation of flowing water in landscape evolution models (LEMs) is often simplified compared to hydrodynamic models, as LEMs make assumptions reducing physical complexity in favor of computational efficiency. The Landlab modeling framework can be used to bridge the divide between complex runoff models and more traditional LEMs, creating a new type of framework not commonly used in the geomorphology or hydrology communities. Landlab is a Python-language library that includes tools and process components that can be used to create models of Earth-surface dynamics over a range of temporal and spatial scales. The Landlab OverlandFlow component is based on a simplified inertial approximation of the shallow water equations, following the solution of de Almeida et al.(2012). This explicit two-dimensional hydrodynamic algorithm simulates a flood wave across a model domain, where water discharge and flow depth are calculated at all locations within a structured (raster) grid. Here, we illustrate how the OverlandFlow component contained within Landlab can be applied as a simplified event-based runoff model and how to couple the runoff model with an incision model operating on decadal timescales. Examples of flow routing on both real and synthetic landscapes are shown. Hydrographs from a single storm at multiple locations in the Spring Creek watershed, Colorado, USA, are illustrated, along with a map of shear stress applied on the land surface by flowing water. The OverlandFlow component can also be coupled with the Landlab DetachmentLtdErosion component to illustrate how the non-steady flow routing regime impacts incision across a watershed. The hydrograph and incision results are compared to simulations driven by steady-state runoff. Results from the coupled runoff and incision model indicate that runoff dynamics can impact landscape relief and channel concavity, suggesting that, on landscape evolution timescales, the OverlandFlow model may lead to differences in
Quasiadiabatic modes from viscous inhomogeneities
Giovannini, Massimo
2016-04-20
The viscous inhomogeneities of a relativistic plasma determine a further class of entropic modes whose amplitude must be sufficiently small since curvature perturbations are observed to be predominantly adiabatic and Gaussian over large scales. When the viscous coefficients only depend on the energy density of the fluid the corresponding curvature fluctuations are shown to be almost adiabatic. After addressing the problem in a gauge-invariant perturbative expansion, the same analysis is repeated at a non-perturbative level by investigating the nonlinear curvature inhomogeneities induced by the spatial variation of the viscous coefficients. It is demonstrated that the quasiadiabatic modes are suppressed in comparison with a bona fide adiabatic solution. Because of its anomalously large tensor to scalar ratio the quasiadiabatic mode cannot be a substitute for the conventional adiabatic paradigm so that, ultimately, the present findings seems to exclude the possibility of a successful accelerated dynamics solely...
The viscous slip coefficient for a binary gas mixture
Energy Technology Data Exchange (ETDEWEB)
Knackfuss, Rosenei F. [Universidade Federal de Santa Maria (UFSM), RS (Brazil). Centro de Ciencias Naturais e Exatas. Dept. de Matematica], e-mail: rfknackfuss@gmail.com
2009-07-01
For a moderately small rarefaction, the Navier-Stokes equations are associated with of the slip boundary condition, i e the velocity of the gas on the surface is different from zero at the surface, but its tangential component, depends on the profile distribution of velocity and temperature near the surface. The slip for the velocity profile near the surface is determined by the viscous slip coefficient. The viscous slip coefficient can be determined solving the equation of the Boltzmann or the kinetic equations which are simplified forms of Boltzmann equation with respect to the operator of collision. For this reason, in this work is presented the derivation of the solution of the viscous-slip problem for the mixtures of two noble gases, based on the McCormack model that is developed in terms of an analytical version of the discrete ordinates method has been applied with excellent results, to derive solutions to several problems in rarefied gas dynamics. To complete the problem, include the gas-surface interaction, based on the model of Cercignani-Lampis, which, unlike the model of Maxwell, has two accommodation coefficients: the coefficient of accommodation of tangential moment and the energy accommodation coefficient kinetics due to normal component of velocity. (author)
Lectures on Mathematical Foundation of Turbulent Viscous Flows
Miyakawa, Tetsuro
2006-01-01
Five leading specialists reflect on different and complementary approaches to fundamental questions in the study of the Fluid Mechanics and Gas Dynamics equations. Constantin presents the Euler equations of ideal incompressible fluids and discusses the blow-up problem for the Navier-Stokes equations of viscous fluids, describing some of the major mathematical questions of turbulence theory. These questions are connected to the Caffarelli-Kohn-Nirenberg theory of singularities for the incompressible Navier-Stokes equations that is explained in Gallavotti's lectures. Kazhikhov introduces the theory of strong approximation of weak limits via the method of averaging, applied to Navier-Stokes equations. Y. Meyer focuses on several nonlinear evolution equations - in particular Navier-Stokes - and some related unexpected cancellation properties, either imposed on the initial condition, or satisfied by the solution itself, whenever it is localized in space or in time variable. Ukai presents the asymptotic analysis th...
Giovannini, Massimo
2005-01-01
Gravitational and hydrodynamical perturbations are analysed in a relativistic plasma containing a mixture of interacting fluids characterized by a non-negligible bulk viscosity coefficient. The energy-momentum transfer between the cosmological fluids, as well as the fluctuations of the bulk viscosity coefficients, are analyzed simultaneously with the aim of deriving a generalized set of evolution equations for the entropy and curvature fluctuations. For typical length scales larger than the Hubble radius, the fluctuations of the bulk viscosity coefficients and of the decay rate provide source terms for the evolution of both the curvature and the entropy fluctuations. According to the functional dependence of the bulk viscosity coefficient on the energy densities of the fluids composing the system, the mixing of entropy and curvature perturbations is scrutinized both analytically and numerically.
Energy Technology Data Exchange (ETDEWEB)
Giovannini, Massimo [Centro ' Enrico Fermi' , Compendio del Viminale, Via Panisperna 89/A, 00184 Rome (Italy) and Department of Physics, Theory Division, CERN, 1211 Geneva 23 (Switzerland)]. E-mail: massimo.giovannini@cern.ch
2005-09-01
Gravitational and hydrodynamical perturbations are analysed in a relativistic plasma containing a mixture of interacting fluids characterized by a non-negligible bulk viscosity coefficient. The energy-momentum transfer between the cosmological fluids, as well as the fluctuations of the bulk viscosity coefficients, are analyzed simultaneously with the aim of deriving a generalized set of evolution equations for the entropy and curvature fluctuations. For typical length scales larger than the Hubble radius, the fluctuations of the bulk viscosity coefficients and of the decay rate provide source terms for the evolution of both the curvature and the entropy fluctuations. According to the functional dependence of the bulk viscosity coefficient on the energy densities of the fluids composing the system, the mixing of entropy and curvature perturbations is scrutinized both analytically and numerically.
Finite Element Based Viscous Numerical Wave Flume
Directory of Open Access Journals (Sweden)
Jianmin Qin
2013-01-01
Full Text Available A two-dimensional numerical wave flume (NWF for viscous fluid flows with free surface is developed in this work. It is based on the upwind finite element solutions of Navier-Stokes equations, CLEAR-volume of fluid method for free surface capture, internal wave maker for wave generation, and sponge layer for wave absorbing. The wave generation and absorption by prescribing velocity boundary conditions along inlet and radiation boundary condition along outlet are also incorporated. The numerical model is validated against several benchmarks, including dam-breaking flow, liquid sloshing in baffled tank, linear water wave propagation and reflection from vertical wall, nonlinear solitary wave fission over sharp step, and wave-induced fluid resonance in narrow gap confined by floating structures. The comparisons with available experimental data, numerical results, and theoretical solutions confirm that the present numerical wave flume has good performance in dealing with complex interface flows and water wave interaction with structures.
Digital Repository Service at National Institute of Oceanography (India)
Unnikrishnan, A.S.
stream_size 3 stream_content_type text/plain stream_name Trg_Calculat_Water_Depth_Chart_Datum_1991_22.pdf.txt stream_source_info Trg_Calculat_Water_Depth_Chart_Datum_1991_22.pdf.txt Content-Encoding ISO-8859-1 Content-Type text.../plain; charset=ISO-8859-1 ...
Shallow Water Acoustic Laboratory
Federal Laboratory Consortium — FUNCTION: Supports experimental research where high-frequency acoustic scattering and surface vibration measurements of fluid-loaded and non-fluid-loaded structures...
Solidity of viscous liquids. III
DEFF Research Database (Denmark)
Dyre, Jeppe
2005-01-01
is much larger than estimated from the alpha relaxation time. This is shown to follow from the solidity of viscous liquids in an argument which, utilizing the irrelevance of momentum conservation at high viscosity, predicts that at high viscosity the coherent diffusion constant is much larger than...
Directory of Open Access Journals (Sweden)
LH. Sipaúba-Tavares
Full Text Available Plankton communities and macrofauna associated to aquatic macrophyte stands in a shallow water-supply reservoir (21°14′09″S; 48°18′38″W on an aquaculture farm were compared to evaluate the relationship between organism densities and some abiotic features of the reservoir. Water and communities associated were sampled at two sites, one in an area with the predominance of Eichhornia azurea (Sw. Kunth and the other with the predominance of Salvinia auriculata Aublet. Communities associated with macrophytes were sampled with floating quadrants (0.5 m2; the macrophytes were washed and plankton and macrofauna were fixated with 4% formalin and 1% lugol iodine; the specimens were then identified and counted. Plankton and macrofauna communities associated with S. auriculata and E. azurea had a similar diversity of species but different (p<0.05 in the abundance of associated organisms. Eichhornia azurea had the highest contents in dry and wet weight, total phosphorus, total nitrogen and organic matter. Planktonic algae were directly correlated with biomass of E. azurea. The taxa with highest densities were Rotifera and Zygnematophyceae. Results showed that the environmental variables associated with macrophytes presence in the shallow reservoir is a strong predictor of favourable conditions to maintain great diversity plankton community and macrofauna associated with plants. The role of macrophytes is important for not only stabilising the clear-water state and maintaining high diversity of organisms associated, but also it seems to be a good alternative to maintaining desirable water-supply quality for aquaculture farms.
Domeneghetti, Stefania; Varotto, Laura; Civettini, Michele; Rosani, Umberto; Stauder, Monica; Pretto, Tobia; Pezzati, Elisabetta; Arcangeli, Giuseppe; Turolla, Edoardo; Pallavicini, Alberto; Venier, Paola
2014-11-01
The complex interactions occurring between farmed bivalves and their potential pathogens in the circumstances of global climate changes are current matter of study, owing to the recurrent production breakdowns reported in Europe and other regions of the world. In the frame of Project FP7-KBBE-2010-4 BIVALIFE, we investigated the occurrence of mortality and potential pathogens during the Spring-Summer transition in Crassostrea gigas and Mytilus galloprovincialis cohabiting in the shallow waters of one northern Italian lagoon (Sacca di Goro, Adriatic Sea) and regarded as susceptible and resistant species, respectively. In 2011, limited bivalve mortality was detected in the open-field trial performed with 6-12 month old spat whereas subsequent trials with 2-3 month old spat produced almost complete (2012) and considerable (2013) oyster mortality. Macroscopical examination and histology excluded the presence of notifiable pathogens but, in the sampling preceding the massive oyster spat mortality of 2012, a μdeleted variant of OsHV-1 DNA was found in wide-ranging amounts in all analyzed oysters in conjunction with substantial levels of Vibrio splendidus and Vibrio aestuarianus. The large oyster spat mortality with borderline OsHV-1 positivity recorded in 2013 supports the multi-factorial etiology of the syndrome. This is the first report of a OsHV-1 (under a form interpreted as the variant μVar) in the Goro lagoon. Transcriptional host footprints are under investigation to better understand the bivalve response to environmental factors, included viral and bacterial pathogens, in relation to the observed mortalities. Copyright © 2014 Elsevier Ltd. All rights reserved.
Lomovasky, Betina J.; Gamero, Patricia A.; Romero, Leonardo; Firstater, Fausto N.; Gamarra Salazar, Alex; Hidalgo, Fernando; Tarazona, Juan; Iribarne, Oscar O.
2015-12-01
Accumulation of Argopecten purpuratus shells often occurs after El Niño events in shallow waters of Independencia Bay (14°17‧S-76°10‧W; Pisco, Peru). Here we experimentally investigate the effects of their shell accumulation on macrobenthos assemblages in soft bottom, shallow areas of the bay. A field experiment (from May 2006 to May 2007), including four treatments with different coverage levels of empty shells of A. purpuratus, were randomly arranged in: (1) areas devoid of shells ("Empty" treatment: experimental control), (2) 50% of the plot area covered with shells haphazardly distributed over the bottom ("medium" treatment), (3) 100% of the plot area covered with shells, forming a 10 cm valve layer ("full" treatment) and (4) "natural control". We found a total of 124 taxa throughout the experiment. Polychaetes, crustaceans and mollusks were the most abundant groups in "natural controls", dominated by the gastropod Nassarius gayi and the polychaetes Prionospio peruana, Platynereis bicanaliculata and Mediomastus branchiferus. The abundance of individuals (N) and the species richness (S) were higher in the "medium" treatment, but only in one month under positive sea bottom thermal anomalies. Similarity analysis (Bray-Curtis) showed that "natural control", "empty" and "full" treatments were more similar among them than the "medium" treatment. Multidimensional analysis showed no clear species association among treatments and a higher grouping among the samplings of Jun-06, Aug-06 and Nov-06. Our results also showed that the commercial crab Romaleon polyodon and the polyplacophora Tonicia elegans were positively affected by shell accumulations ("medium" treatment), while the limpet Fissurella crassa was negatively affected. Our study shows that directly by changing habitat structure or indirectly by changing sediment characteristics, the addition of scallop shells to the soft bottom can modify the macrobenthic assemblage; however, the seasonal oceanographic
Bertotti, Giovanni; Bisdom, Kevin; Bezerra, Hilario; Reijmer, John; Cazarin, Carol
2016-04-01
Despite the scarcity of major deformation structures such as folds and faults, the flat-lying, post-rift shallow water carbonates of the Jandaira Formation (Potiguar Basin, NE Brazil) display well-organized fracture systems distributed of tens of km2. Structures observed in the outcropping carbonates are sub-vertical, generally N-S trending mode I and hybrid veins and barren fractures, sub-vertical roughly E-W trending stylolites and sub-horizontal stylolites. These features developed during subsidence in a simple and constant stress field characterized by, beside gravity, a significant horizontal stress probably of tectonic origin. The corresponding depth curves have different origin and slopes and, therefore, cross each other resulting in position of the principal stresses which change with depth. As a result, the type and amount of fractures affecting subsiding rocks change despite the fact that the far-field stresses remain constant. Following early diagenesis and porosity elimination in the first 100-200m depth, Jandaira carbonates experienced wholesale fracturing at depths of 400-800m resulting in a network of NNW-NE trending fractures partly organized in conjugate sets with a low interfault angle and a sub-vertical intersection, and sub-vertical stylolites roughly perpendicular to the fractures. Intense fluid circulation was activated as a consequence through the carbonates. With increasing subsidence, sub-horizontal stylolites formed providing calcite which precipitated in the open fractures transforming them in veins. The Jandaira formation lost thereby the permeability it had reached during the previous stage. Because of the lack of major deformation, the outcrops of the Jandaira Formation is an excellent analog for carbonate reservoirs in the Middle East, South Atlantic and elsewhere.
Leal-Acosta, María Luisa; Shumilin, Evgueni; Mirlean, Nicolai; Delgadillo-Hinojosa, Francisco; Sánchez-Rodríguez, Ignacio
2013-02-01
The influence of hydrothermal venting activity on arsenic (As) and mercury (Hg) accumulation was investigated in the shallow-water marine ecosystem of Concepcion Bay in the western Gulf of California. Geochemical data indicate that the marine shallow-water hydrothermal system of the Mapachitos site is a source of As and Hg for the water, sediment and algae collected along a transect moving across the western region of the bay. Although a small proportion of As and Hg precipitates close to the hydrothermal vent, both elements remain largely in the dissolved fraction, spreading a long distance from the source. The brown seaweed Sargassum sinicola thriving near the area of hydrothermal venting accumulates large quantities of As (above 600 mg kg (-1)), surpassing its typical concentration in the genus Sargassum by an order of magnitude. In contrast to As, the seaweed does not significantly accumulate Hg.
Jung, Seom-Kyu; Choi, Bok Kyoung; Kim, Bong-Chae; Kim, Byoung-Nam; Kim, Seong Hyeon; Park, Yosup; Lee, Yong-Kuk
2012-07-01
The seawater temperature and wind dependences and diurnal variation of the ambient noise at the snapping shrimp colony in shallow water of the southern sea of Korea were investigated. The ambient noise levels are significantly affected by the snapping shrimp sound, when the bottom seawater temperature increases and the wind speed decreases. However, they are not exceptively almost affected by the snapping shrimp sound when the wind speed decreases at low seawater temperatures (shrimp sound in the morning and night time zones. This study shows that the activity of the snapping shrimp affecting the variation in ambient noise level in shallow water can be related to the wind speed as well as the seawater temperature. This study also shows that the snapping shrimp in diurnal activity can be more active in the morning and night time zones.
Nanoconfined ionic liquids: Disentangling electrostatic and viscous forces
Lhermerout, Romain; Perkin, Susan
2018-01-01
Recent reports of surface forces across nanoconfined ionic liquids have revealed the existence of an anomalously long-ranged interaction apparently of electrostatic origin. Ionic liquids are viscous, and therefore it is important to inspect rigorously whether the observed repulsive forces are indeed equilibrium forces or, rather, arise from the viscous force during drainage of the fluid between two confining surfaces. In this paper we present our direct measurements of surface forces between mica sheets approaching in the ionic liquid [C2C1Im ] [NTf2] , exploring three orders of magnitude in approach velocity. Trajectories are systematically fitted by solving the equation of motion, allowing us to disentangle the viscous and equilibrium contributions. First, we find that the drainage obeys classical hydrodynamics with a negative slip boundary condition in the range of the structural force, implying that a nanometer -thick portion of the liquid in the vicinity of the solid surface is composed of ordered molecules that do not contribute to the flow. Second, we show that a long-range static force must indeed be invoked, in addition to the viscous force, in order to describe the data quantitatively. This equilibrium interaction decays exponentially and with decay length in agreement with the screening length reported for the same system in previous studies. In those studies the decay was simply checked to be independent of velocity and measured at a low approach rate, rather than explicitly taking account of viscous effects: we explain why this gives indistinguishable outcomes for the screening length by noting that the viscous force is linear to very good approximation over a wide range of distances.
R. Gangstø; Gehlen, M; Schneider, B.; L. Bopp; O. Aumont; Joos, F.
2008-01-01
International audience; The marine aragonite cycle has been included in the global biogeochemical model PISCES to study the role of aragonite in shallow water CaCO3 dissolution. Aragonite production is parameterized as a function of mesozooplankton biomass and aragonite saturation state of ambient waters. Observation-based estimates of marine carbonate production and dissolution are well reproduced by the model and about 60% of the combined CaCO3 water column dissolution from aragonite and ca...
Stability of axisymmetric swirl flows of viscous incompressible fluid
Aktershev, S. P.; Kuibin, P. A.
2013-09-01
A new method of solution to the problem of stability of the swirl flow of viscous incompressible fluid is developed. The method based on expansion of the required function into power series of radial coordinate allows an avoidance of difficulties related to numerical integration of the system of differential equations with a singular point. Stability of the Poiseuille flow in a rotating pipe is considered as an example.
Parente, Mariano; Frijia, Gianluca; di Lucia, Matteo; Jenkyns, Hugh C.; Woodfine, Richard G.; Baroncini, Francesco
2008-09-01
A two-step pattern in the extinction of larger foraminifersis recorded in the upper Cenomanian shallow-water carbonatesof the southern Apennines (Italy). The first step eliminatedthe alveolinids, the most extreme oligotrophs, and reduced dramaticallythe diversity of larger foraminifers. The second step wipedout the few survivors, seemingly able to tolerate mesotrophicconditions, leaving a disaster fauna dominated by small heterotrophs.This pattern of extinction parallels the ecological successionof shallow-water benthic foraminiferal assemblages along a gradientof increasing nutrient availability. High-resolution carbonisotope stratigraphy shows that the extinction of alveolinidswas contemporaneous with the extinction of rotaliporid plankticforaminifers, the drowning of certain Tethyan carbonate platforms,and an episode of thermal instability recorded in sea-surfacetemperature in the open ocean. Ocean stratification, duringthe first phase of Oceanic Anoxic Event 2, would have promotedoligotrophic conditions in surface tropical waters and maximumdiversity of larger foraminifers. Following this, ocean overturningcaused by surface-water cooling is credited with deliveringto shallow-water environments the excess nutrient loads previouslystored at depth, triggering the environmental changes leadingto stepwise extinction of larger foraminifers.
Nonlinear Gravity-Capillary Waves on a Compressible Viscous Fluid with Edge Constraints.
1983-05-01
Rc is positive and finite and m 3 < 0 when R > Rc . Then the Surgers equation is ill-posed for R > Rc and we define R < Rc as a criterion for the...8217 block number) Gravity-Capillary waves, compressible viscous fluid, edge constraints, Surgers equation S. LOIST RIACY (Cone Mu. an tgve* side it naava sod
Approximate equations at breaking for nearshore wave transformation coefficients
Digital Repository Service at National Institute of Oceanography (India)
Chandramohan, P.; Nayak, B.U.; SanilKumar, V.
Based on small amplitude wave theory approximate equations are evaluated for determining the coefficients of shoaling, refraction, bottom friction, bottom percolation and viscous dissipation at breaking. The results obtainEd. by these equations...
Relativistic shocks and mach cones in viscous gluon matter
Energy Technology Data Exchange (ETDEWEB)
Bouras, Ioannis; Xu, Zhe; El, Andrej; Fochler, Oliver; Lauciello, Francesco; Greiner, Carsten [Institut fuer Theoretische Physik, Johann Wolfgang Goethe Universitaet, Frankfurt am Main (Germany); Molnar, Etele; Niemi, Harri [Frankfurt Institute for Advanced Studies, Frankfurt am Main (Germany); Rischke, Dirk [Institut fuer Theoretische Physik, Johann Wolfgang Goethe Universitaet, Frankfurt am Main (Germany); Frankfurt Institute for Advanced Studies, Frankfurt am Main (Germany)
2010-07-01
We solve the relativistic Riemann problem in a viscous and heat conducting gluon matter employing a microscopic parton cascade and compare it to the relativistic causal dissipative fluid dynamical model of Israel and Stewart. We demonstrate the transition from ideal to viscous shocks by varying the shear viscosity to entropy density ratio {eta}/s from zero to infinity and compare different dissipative quantities. We show the behaviour and the break down of viscous hydrodynamics for an out of equilibrium state using the local Knudsen number. Employing the microscopic parton cascade we investigate the evolution of mach cones in a viscous gluonic matter. We see that for {eta}/s=1/4{pi} a collective behaviour of the medium is observed, resulting in cone structure and diffusion wake of the energy density profile. The mach cone vanish very fast when increasing the shear viscosity in the medium. As comparison to experiments two-particle correlations are shown. We have derived third-order corrections to the Israel-Stewart theory using the entropy principle. This new equation is solved for one-dimensional Bjorken boost-invariant expansion. The scaling solutions for various values of {eta}/s are shown to be in very good agreement with those obtained from kinetic transport calculations.
Modeling and Simulation of Viscous Electro-Active Polymers.
Vogel, Franziska; Göktepe, Serdar; Steinmann, Paul; Kuhl, Ellen
2014-11-01
Electro-active materials are capable of undergoing large deformation when stimulated by an electric field. They can be divided into electronic and ionic electro-active polymers (EAPs) depending on their actuation mechanism based on their composition. We consider electronic EAPs, for which attractive Coulomb forces or local re-orientation of polar groups cause a bulk deformation. Many of these materials exhibit pronounced visco-elastic behavior. Here we show the development and implementation of a constitutive model, which captures the influence of the electric field on the visco-elastic response within a geometrically non-linear finite element framework. The electric field affects not only the equilibrium part of the strain energy function, but also the viscous part. To adopt the familiar additive split of the strain from the small strain setting, we formulate the governing equations in the logarithmic strain space and additively decompose the logarithmic strain into elastic and viscous parts. We show that the incorporation of the electric field in the viscous response significantly alters the relaxation and hysteresis behavior of the model. Our parametric study demonstrates that the model is sensitive to the choice of the electro-viscous coupling parameters. We simulate several actuator structures to illustrate the performance of the method in typical relaxation and creep scenarios. Our model could serve as a design tool for micro-electro-mechanical systems, microfluidic devices, and stimuli-responsive gels such as artificial skin, tactile displays, or artificial muscle.
Shannon, Lee H.
Most studies investigating the effects of military-associated anthropogenic noise concentrate on deep sea or open ocean propagation of sonar and its effect on marine mammals. In littoral waters, U.S. military special operations units regularly conduct shallow water explosives training, yet relatively little attention has been given to the potential impact on nearshore marine ecosystems from these underwater detonations. This dissertation research focused on the Pu'uloa Underwater Detonation Range off the coast of O`ahu, and examined multiple aspects of the surrounding marine ecosystem and the effects of detonations using acoustic monitoring techniques. The soundscape of a nearshore reef ecosystem adjacent to the UNDET range was characterized through analysis of passive acoustic recordings collected over the span of 6 years. Snapping shrimp were the predominant source of noise, and a diel pattern was present, with increased sound energy during the night hours. Results revealed a difference of up to 7dB between two Ecological Acoustic Recorder locations 2.5km apart along the 60ft isobath. Passive acoustic recording files were searched visually and aurally for odontocete whistles. Whistles were detected in only 0.6% of files analyzed, indicating this area is not frequently transited by coastal odontocete emitting social sounds. The study also opportunistically captured a humpback whale singing during a detonation event, during which the animal showed no obvious alteration of its singing behavior. Four separate underwater detonation events were recorded using a surface deployed F-42C transducer, and the resulting analysis showed no measurable drop in the biologically produced acoustic energy in reaction to the explosive events. Coral reef fishes were recorded visually and acoustically during detonation events at a known distance and bearing from a known explosive sound source. Individual fish behavioral responses to the explosion varied, and a sharp uptick in fish
Wimmer, Michael; Mandlburger, Gottfried; Ressl, Camillo; Pfeifer, Norbert
2016-04-01
In our contribution, a photogrammetric approach for water depth estimation of a shallow water body is developed and applied to a gravel-bed river in order to evaluate the possibilities of passive optical remote sensing for high resolution bathymetry. While 2-media (air and water) photogrammetry has been described before, it was concentrated on reconstruction of individual points. Here, we take a different approach and aim at a dense surface description of the river bed as seen from the aerial image through the water column. In a first step, the influence of light refraction at the boundary between two media for photogrammetric point retrieval is assessed. The effect is theoretically investigated under varying conditions, i.e. the 3D point displacement caused by refraction is related to parameters such as water depth, image geometry et cetera. Especially the assumption of a plain, horizontal water surface does not hold in practice. Therefore, also the limitations of the theoretical model are determined by investigating, how water surface waves and the corresponding deviation of the surface normal vectors from vertical direction distort the results. In the second, practical part of the work, a refraction correction procedure is derived from the prior investigations and is embedded into the photogrammetric workflow. A full photogrammetric processing chain is applied to a set of aerial images of the pre-Alpine Pielach River in Lower Austria. The RGB images were taken simultaneously to an Airborne Laser Bathymetry (ALB) campaign providing high resolution reference data. Based on these images, a Digital Terrain Model is derived for the open as well as the submerged areas. Running through the procedure gives important insights about the possibilities of influencing the processing pipeline of commercial photogrammetric software packages in order to apply the developed refraction correction. Especially, the deviation from the epipolar constraint caused by refraction and the
Computation of Viscous Incompressible Flows
Kwak, Dochan
2011-01-01
This monograph is intended as a concise and self-contained guide to practitioners and graduate students for applying approaches in computational fluid dynamics (CFD) to real-world problems that require a quantification of viscous incompressible flows. In various projects related to NASA missions, the authors have gained CFD expertise over many years by developing and utilizing tools especially related to viscous incompressible flows. They are looking at CFD from an engineering perspective, which is especially useful when working on real-world applications. From that point of view, CFD requires two major elements, namely methods/algorithm and engineering/physical modeling. As for the methods, CFD research has been performed with great successes. In terms of modeling/simulation, mission applications require a deeper understanding of CFD and flow physics, which has only been debated in technical conferences and to a limited scope. This monograph fills the gap by offering in-depth examples for students and engine...
Modelling of nonlinear shoaling based on stochastic evolution equations
DEFF Research Database (Denmark)
Kofoed-Hansen, Henrik; Rasmussen, Jørgen Hvenekær
1998-01-01
A one-dimensional stochastic model is derived to simulate the transformation of wave spectra in shallow water including generation of bound sub- and super-harmonics, near-resonant triad wave interaction and wave breaking. Boussinesq type equations with improved linear dispersion characteristics...... are recast into evolution equations for the complex amplitudes, and serve as the underlying deterministic model. Next, a set of evolution equations for the cumulants is derived. By formally introducing the well-known Gaussian closure hypothesis, nonlinear evolution equations for the power spectrum...
Singular limits in thermodynamics of viscous fluids
Feireisl, Eduard
2017-01-01
This book is about singular limits of systems of partial differential equations governing the motion of thermally conducting compressible viscous fluids. "The main aim is to provide mathematically rigorous arguments how to get from the compressible Navier-Stokes-Fourier system several less complex systems of partial differential equations used e.g. in meteorology or astrophysics. However, the book contains also a detailed introduction to the modelling in mechanics and thermodynamics of fluids from the viewpoint of continuum physics. The book is very interesting and important. It can be recommended not only to specialists in the field, but it can also be used for doctoral students and young researches who want to start to work in the mathematical theory of compressible fluids and their asymptotic limits." Milan Pokorný (zbMATH) "This book is of the highest quality from every point of view. It presents, in a unified way, recent research material of fundament al importance. It is self-contained, thanks to Chapt...
Nonlinear waves in bipolar complex viscous astroclouds
Karmakar, P. K.; Haloi, A.
2017-05-01
A theoretical evolutionary model to analyze the dynamics of strongly nonlinear waves in inhomogeneous complex astrophysical viscous clouds on the gravito-electrostatic scales of space and time is procedurally set up. It compositionally consists of warm lighter electrons and ions (Boltzmanian); and cold massive bi-polar dust grains (inertial fluids) alongside vigorous neutral dynamics in quasi-neutral hydrodynamic equilibrium. Application of the Sagdeev pseudo-potential method reduces the inter-coupled structure equations into a pair of intermixed forced Korteweg-de Vries-Burgers (f-KdVB) equations. The force-terms are self-consistently sourced by inhomogeneous gravito-electrostatic interplay. A numerical illustrative shape-analysis based on judicious astronomical parametric platform shows the electrostatic waves evolving as compressive dispersive shock-like eigen-modes. A unique transition from quasi-monotonic to non-monotonic oscillatory compressive shock-like patterns is found to exist. In contrast, the self-gravitational and effective perturbations grow purely as non-monotonic compressive oscillatory shock-like structures with no such transitory features. It is seen that the referral frame velocity acts as amplitude-reducing agent (stabilizing source) for the electrostatic fluctuations solely. A comparison in the prognostic light of various earlier satellite-based observations and in-situ measurements is presented. The paper ends up with synoptic highlights on the main implications and non-trivial applications in the interstellar space and cosmic plasma environments leading to bounded structure formation.
Development of a Model Foamy Viscous Fluid
Directory of Open Access Journals (Sweden)
Vial C.
2013-08-01
Full Text Available The objective is to develop a model viscous foamy fluid, i.e. below the very wet limit, the rheological and stability properties of which can be tuned. First, the method used for the preparation of foamy fluids is detailed, including process and formulation. Then, experimental results highlight that stable foamy fluids with a monomodal bubble size distribution can be prepared with a void fraction between 25% and 50% (v/v. Their viscoelastic properties under flow and low-strain oscillatory conditions are shown to result from the interplay between the formulation of the continuous phase, void fraction and bubble size. Their apparent viscosity can be described using the Cross equation and zero-shear Newtonian viscosity may be predicted by a Mooney equation up to a void fraction about 40%. The Cox-Merz and the Laun’s rules apply when the capillary number Ca is lower than 0.1. The upper limit of the zero-shear plateau region decreases when void fraction increases or bubble size decreases. In the shear-thinning region, shear stress varies with Ca1/2, as in wet foams with immobile surfaces. Finally, foamy fluids can be sheared up to Ca about 0.1 without impairing their microstructure. Their stability at rest achieves several hours and increases with void fraction due to compact packing constraints. These constitute, therefore, versatile model fluids to investigate the behaviour of foamy fluids below the very wet limit in process conditions.
National Oceanic and Atmospheric Administration, Department of Commerce — Near-shore shallow water Conductivity-Temperature-Depth (CTD) surveys provided vertical profiles of temperature, salinity, and turbidity providing indications for...
National Oceanic and Atmospheric Administration, Department of Commerce — Near-shore shallow water Conductivity-Temperature-Depth (CTD) surveys provided vertical profiles of temperature, salinity, and turbidity providing indications for...
2D Inviscid and Viscous Inverse Design Using Continuous Adjoint and Lax-Wendroff Formulation
Proctor, Camron Lisle
The continuous adjoint (CA) technique for optimization and/or inverse-design of aerodynamic components has seen nearly 30 years of documented success in academia. The benefits of using CA versus a direct sensitivity analysis are shown repeatedly in the literature. However, the use of CA in industry is relatively unheard-of. The sparseness of industry contributions to the field may be attributed to the tediousness of the derivation and/or to the difficulties in implementation due to the lack of well-documented adjoint numerical methods. The focus of this work has been to thoroughly document the techniques required to build a two-dimensional CA inverse-design tool. To this end, this work begins with a short background on computational fluid dynamics (CFD) and the use of optimization tools in conjunction with CFD tools to solve aerodynamic optimization problems. A thorough derivation of the continuous adjoint equations and the accompanying gradient calculations for inviscid and viscous constraining equations follows the introduction. Next, the numerical techniques used for solving the partial differential equations (PDEs) governing the flow equations and the adjoint equations are described. Numerical techniques for the supplementary equations are discussed briefly. Subsequently, a verification of the efficacy of the inverse design tool, for the inviscid adjoint equations as well as possible numerical implementation pitfalls are discussed. The NACA0012 airfoil is used as an initial airfoil and surface pressure distribution and the NACA16009 is used as the desired pressure and vice versa. Using a Savitsky-Golay gradient filter, convergence (defined as a cost functionequations results are followed by the discussion of the viscous inverse design results and techniques used to further the convergence of the optimizer. The relationship between limiting step-size and convergence in a line-search optimization is shown to slightly decrease the final cost function at
Directory of Open Access Journals (Sweden)
Jeffrey A. Sibaja-Cordero
2012-11-01
Full Text Available Geographic Information Systems (GIS applications used in marine habitats are powerful tools for management and monitoring of marine reserves and resources. Here, we present a series of maps of the soft and hard substrates in the shallow waters (>80 m depth of Parque Nacional Isla del Coco (PNIC= Isla del Coco National Park. We use bathymetry data and field data as input for a GIS, GAM, and kriging methods to generate a series of maps that describe the bottom characteristics. Eight types of bottom were found in the PNIC by composition and grain size. The shore of the island and islets consisted of rocky formations (mainly basalts, with coral reefs in the subtidal of some areas. Rhodolith beds had a dispersing distribution. The bottom on the southern and southwestern region is hard substrate, while sediments cover the northern and northeastern zones. Slightly gravelly sand dominated the bays, while gravelly sand (with more coarse grains was frequent offshore. The inner areas of Chatham and Wafer bays have mud and organic matter. The sediments in the area are mostly carbonates, except in Bahía Yglesias where clastic sediments (from the erosion of basalts are presented. The information generated in this study could be a valuable input for future monitoring in the PNIC.La aplicación de Sistemas de Información Geográfica (SIG, en los hábitats marinos es muy importante para la gestión y control de las reservas y recursos marinos. Aquí se presentan una serie de mapas de los sustratos sedimentarios y duros en las aguas poco profundas (> 80 m de profundidad del Parque Nacional Isla del Coco (PNIC. Utilizamos datos de batimetría y datos de campo como entrada para un SIG, GAM, y los métodos de “kriging” para generar una serie de mapas que describen las características del fondo. ocho tipos de fondo marino se encuentran en el PNIC. La orilla de la isla y los islotes consistía de formaciones rocosas (principalmente basaltos, con arrecifes de
Schmitt, Katharina; Heimhofer, Ulrich; Frijia, Gianluca; Huck, Stefan
2017-04-01
Shallow-water carbonate platform sections are valuable archives for the reconstruction of deep-time environmental and climatic conditions, but the biostratigraphic resolution is often rather low. Moreover, chemostratigraphic correlation with well-dated pelagic sections by means of bulk carbonate carbon-isotope stratigraphy is notoriously difficult and afflicted with large uncertainties, as shallow-water sections are particularly prone to the impact of diagenesis. In the current study, an integrated biostratigraphic-chemostratigraphic approach is applied to southern Tethyan Lower Cretaceous carbonate platform deposits (Santa Lucia, Monte La Costa sections) situated in the Central Apennines in Italy. The 500 m thick Santa Lucia section, representing an open lagoonal inner carbonate platform setting, provides a characteristic carbon- and oxygen-isotope pattern that allows for correlation with pelagic composite reference curves (Vocontian and Umbria Marche basins). Calibrated by means of foraminiferal biostratigraphy and rudist bivalve strontium-isotope stratigraphy, the section serves as local chemostratigraphic shallow-water reference for the Barremian to Cenomanian. The 250 m thick Monte La Costa section comprises predominantly coarse grained (biostromal) and often strongly cemented shelf margin deposits. Although benthic foraminifera are scarce and the carbonates evidently suffered strong diagenetic alteration, high-resolution (rudist shell) strontium-isotope stratigraphy in combination with superimposed carbon-isotope trends and biological-lithological changes (e.g., mass occurrences of Bacinella irregularis s.l) enables correlation with the Early Albian to Cenomanian portion of the Santa Lucia reference section. At both localities, chemostratigraphy indicates a major gap covering large parts of the Lower and middle Cenomanian. After having considerably improved the stratigraphic resolution of the studied sections, selected best-preserved rudist shells are going
Digital Repository Service at National Institute of Oceanography (India)
Amrutha, M.M.; SanilKumar, V.; Sharma, S.; Singh, J.; Gowthaman, R.; Kankara, R.S.
Eng., vol.107; 2015; 259-270 Characteristics of shallow water waves off the central west coast of India before, during and after the onset of the Indian summer monsoon M.M.Amrutha1, V. Sanil Kumar1*, Sheela Sharma, Jai Singh1, R.Gowthaman1, R..., and Section 4 summarizes the conclusions. 2. Methods 2.1 Study region The study locations are; 1) off Vengurla at a water depth of 15 m in the eastern Arabian Sea (latitude 15.8327° N and longitude 73.5681° E), 2) off Honnavar at water depth of 30 m (14...
Lauvernet, C.; Munoz-Carpena, R.; Carluer, N.
2012-04-01
Natural or introduced areas of vegetation, also known as vegetative filter strips (VFS), are a common environmental control practice to protect surface water bodies from human influence. In Europe, VFS are placed along the water network to protect from agrochemical drift during applications, in addition to runoff control. Their bottomland placement next to the streams often implies the presence of a seasonal shallow water table which can have a profound impact on the efficiency of the buffer zone (Lacas et al. 2005). A physically-based algorithm describing ponded infiltration into soils bounded by a water table, proposed by Salvucci and Enthekabi (1995), was further developed to simulate VFS dynamics by making it explicit in time, account for unsteady rainfall conditions, and by coupling to a numerical overland flow and transport model (VFSMOD) (Munoz-Carpena et al., submitted). In this study, we evaluate the importance of the presence of a shallow water table on filter efficiency (reductions in runoff, sediment and pesticide mass), in the context of all other input factors used to describe the system. Global sensitivity analysis (GSA) was used to rank the important input factors and the presence of interactions, as well as the contribution of the important factors to the output variance. GSA of VSFMOD modified for shallow water table was implemented on 2 sites selected in France because they represent different agro-pedo-climatic conditions for which we can compare the role of the factors influencing the performance of grassed buffer strips for surface runoff, sediment and pesticide removal. The first site at Morcille watershed in the Beaujolais wineyard (Rhône-Alpes) contains a very permeable sandy-clay with water table depth varying with the season (very deep in summer and shallow in winter), with a high slope (20 to 30%), and subject to strong seasonal storms (semi-continental, Mediterranean climate). The second site at La Jailliere (Loire-Atlantique, ARVALIS
One-Dimensional Problem of a Conducting Viscous Fluid with One Relaxation Time
Directory of Open Access Journals (Sweden)
Angail A. Samaan
2011-01-01
Full Text Available We introduce a magnetohydrodynamic model of boundary-layer equations for conducting viscous fluids. This model is applied to study the effects of free convection currents with thermal relaxation time on the flow of a viscous conducting fluid. The method of the matrix exponential formulation for these equations is introduced. The resulting formulation together with the Laplace transform technique is applied to a variety problems. The effects of a plane distribution of heat sources on the whole and semispace are studied. Numerical results are given and illustrated graphically for the problem.
Mathematical models of viscous friction
Buttà, Paolo; Marchioro, Carlo
2015-01-01
In this monograph we present a review of a number of recent results on the motion of a classical body immersed in an infinitely extended medium and subjected to the action of an external force. We investigate this topic in the framework of mathematical physics by focusing mainly on the class of purely Hamiltonian systems, for which very few results are available. We discuss two cases: when the medium is a gas and when it is a fluid. In the first case, the aim is to obtain microscopic models of viscous friction. In the second, we seek to underline some non-trivial features of the motion. Far from giving a general survey on the subject, which is very rich and complex from both a phenomenological and theoretical point of view, we focus on some fairly simple models that can be studied rigorously, thus providing a first step towards a mathematical description of viscous friction. In some cases, we restrict ourselves to studying the problem at a heuristic level, or we present the main ideas, discussing only some as...
Viscous Design of TCA Configuration
Krist, Steven E.; Bauer, Steven X. S.; Campbell, Richard L.
1999-01-01
The goal in this effort is to redesign the baseline TCA configuration for improved performance at both supersonic and transonic cruise. Viscous analyses are conducted with OVERFLOW, a Navier-Stokes code for overset grids, using PEGSUS to compute the interpolations between overset grids. Viscous designs are conducted with OVERDISC, a script which couples OVERFLOW with the Constrained Direct Iterative Surface Curvature (CDISC) inverse design method. The successful execution of any computational fluid dynamics (CFD) based aerodynamic design method for complex configurations requires an efficient method for regenerating the computational grids to account for modifications to the configuration shape. The first section of this presentation deals with the automated regridding procedure used to generate overset grids for the fuselage/wing/diverter/nacelle configurations analysed in this effort. The second section outlines the procedures utilized to conduct OVERDISC inverse designs. The third section briefly covers the work conducted by Dick Campbell, in which a dual-point design at Mach 2.4 and 0.9 was attempted using OVERDISC; the initial configuration from which this design effort was started is an early version of the optimized shape for the TCA configuration developed by the Boeing Commercial Airplane Group (BCAG), which eventually evolved into the NCV design. The final section presents results from application of the Natural Flow Wing design philosophy to the TCA configuration.
Surfactant transport on viscous bilayers
Matar, Omar; Craster, Richard; Warner, Mark
2001-11-01
We model the external delivery of surfactant to pulmonary airways, an integral part of Surfactant Replacement Therapy (SRT), a method of treatment of Respiratory Distress Syndrome in neonates. We examine the spreading dynamics of insoluble surfactant by Marangoni stresses along the mucus-perciliary liquid bilayers that line the inside of airways. The bilayer is modelled as a thin highly viscous mucus surface film (mucus) overlying a much less viscous perciliary liquid layer (PCL); this is appropriate for small airways. By exploiting this large viscosity constrast, a variant of standard lubrication theory is adopted wherein terms, which would have otherwise been neglected in the lubrication approximation, are promoted in order to model correctly the presence of the mucus. Inclusion of van der Waals forces in the model permit the study of the effect of this mucus 'skin' on the possibility of bilayer rupture, a potential cause of failure of SRT. We find that increasing the viscosity contrast and initial mucus layer thickness delays the onset of rupture, while increasing the relative significance of Marangoni stresses leads to more marked thinning and rapid bilayer rupture [1]. [1] O. K. Matar, R. V. Craster and M. R. Warner, submitted to J. Fluid Mech. (2001).
Exact equations for structure functions and equations for source terms up to the sixth order
Peters, Norbert; Gauding, Michael; Göbbert, Jens Henrik; Pitsch, Heinz
2015-01-01
We derive equations for the source terms appearing in structure function equations for the fourth and sixth order under the assumption of homogeneity and isotropy. The source terms can be divided into two classes, namely those stemming from the viscous term and those from the pressure term in the structure function equations. Both kinds are unclosed.
Dynamics of charged bulk viscous collapsing cylindrical source with heat flux
Energy Technology Data Exchange (ETDEWEB)
Shah, S.M.; Abbas, G. [The Islamia University of Bahawalpur, Department of Mathematics, Bahawalpur (Pakistan)
2017-04-15
In this paper, we have explored the effects of dissipation on the dynamics of charged bulk viscous collapsing cylindrical source which allows the out-flow of heat flux in the form of radiations. The Misner-Sharp formalism has been implemented to drive the dynamical equation in terms of proper time and radial derivatives. We have investigated the effects of charge and bulk viscosity on the dynamics of collapsing cylinder. To determine the effects of radial heat flux, we have formulated the heat transport equations in the context of Mueller-Israel-Stewart theory by assuming that thermodynamics viscous/heat coupling coefficients can be neglected within some approximations. In our discussion, we have introduced the viscosity by the standard (non-causal) thermodynamics approach. The dynamical equations have been coupled with the heat transport equation; the consequences of the resulting coupled heat equation have been analyzed in detail. (orig.)
Cottin, Delphine; Brown, Alastair; Oliphant, Andrew; Mestre, Nélia C; Ravaux, Juliette; Shillito, Bruce; Thatje, Sven
2012-08-01
We investigated the tolerance of adult specimens of the shallow-water shrimp Palaemonetes varians to sustained high hydrostatic pressure (10 MPa) across its thermal tolerance window (from 5 to 27 °C) using both behavioural (survival and activity) and molecular (hsp70 gene expression) approaches. To our knowledge, this paper reports the longest elevated hydrostatic pressure exposures ever performed on a shallow-water marine organism. Behavioural analysis showed a 100% survival rate of P. varians after 7 days at 10 MPa and 5 or 10 °C, whilst cannibalism was observed at elevated temperature (27 °C), suggesting no impairment of specific dynamic action. A significant interaction of pressure and temperature was observed for both behavioural and molecular responses. Elevated pressure was found to exacerbate the effect of temperature on the behaviour of the animals by reducing activity at low temperature and by increasing activity at high temperature. In contrast, only high pressure combined with low temperature increased the expression of hsp70 genes. We suggest that the impressive tolerance of P. varians to sustained elevated pressure may reflect the physiological capability of an ancestral species to colonise the deep sea. Our results also support the hypothesis that deep-sea colonisation may have occurred during geological periods of time when the oceanic water column was warm and vertically homogenous. Copyright © 2012 Elsevier Inc. All rights reserved.
Malservisi, R.; Chierici, F.; Iannaccone, G.; Guardato, S.; Pignagnoli, L.; Locritani, M.; Embriaco, D.; Donnarumma, G. P.; Rodgers, M.; Beranzoli, L.
2016-12-01
We present a new methodology aimed at assessing long term small vertical seafloor deformation in shallow water environments by using Bottom Pressure Recorder (BPR) measurements jointly with ancillary sea level, water column and barometric data. These measurements are presently acquired only in areas where the amount of vertical deformation is large and in deep water environment, where the noise induced by the sea state and other near surface disturbances is low. We applied the method to the data acquired in 2011 by a BPR deployed at about 96 m depth in the marine sector of the Campi Flegrei Caldera, during a quasi-symmetric seafloor uplift episode of a few centimeters amplitude. The method provides an estimation of the vertical uplift of the caldera of 2.5 +/- 1.3 cm achieving an unprecedented level of precision in the measurement of the seafloor vertical deformation in shallow water. We reached this result by taking into account the contribution of the BPR instrumental drift and the contribution of the sea water density variations, which can affect the measurement on the order of tens of centimeters. The estimation of the vertical deformation obtained in this way compares favorably with data acquired by a land based GPS station, which is located at the same distance from the area of maximum deformation as the BPR
Large scale structure from viscous dark matter
Blas, Diego; Garny, Mathias; Tetradis, Nikolaos; Wiedemann, Urs Achim
2015-01-01
Cosmological perturbations of sufficiently long wavelength admit a fluid dynamic description. We consider modes with wavevectors below a scale $k_m$ for which the dynamics is only mildly non-linear. The leading effect of modes above that scale can be accounted for by effective non-equilibrium viscosity and pressure terms. For mildly non-linear scales, these mainly arise from momentum transport within the ideal and cold but inhomogeneous fluid, while momentum transport due to more microscopic degrees of freedom is suppressed. As a consequence, concrete expressions with no free parameters, except the matching scale $k_m$, can be derived from matching evolution equations to standard cosmological perturbation theory. Two-loop calculations of the matter power spectrum in the viscous theory lead to excellent agreement with $N$-body simulations up to scales $k=0.2 \\, h/$Mpc. The convergence properties in the ultraviolet are better than for standard perturbation theory and the results are robust with respect to varia...
Sudden viscous dissipation of compressing turbulence
Davidovits, S.; Fisch, N. J.
2015-01-01
Compression of turbulent plasma can amplify the turbulent kinetic energy, if the compression is fast compared to the viscous dissipation time of the turbulent eddies. A sudden viscous dissipation mechanism is demonstrated, whereby this amplified turbulent kinetic energy is rapidly converted into thermal energy, suggesting a new paradigm for fast ignition inertial fusion.
Sudden Viscous Dissipation of Compressing Turbulence.
Davidovits, Seth; Fisch, Nathaniel J
2016-03-11
Compression of turbulent plasma can amplify the turbulent kinetic energy, if the compression is fast compared to the viscous dissipation time of the turbulent eddies. A sudden viscous dissipation mechanism is demonstrated, whereby this amplified turbulent kinetic energy is rapidly converted into thermal energy, suggesting a new paradigm for fast ignition inertial fusion.
On exact traveling-wave solutions for local fractional Korteweg-de Vries equation
Yang, Xiao-Jun; Tenreiro Machado, J. A.; Baleanu, Dumitru; Cattani, Carlo
2016-08-01
This paper investigates the Korteweg-de Vries equation within the scope of the local fractional derivative formulation. The exact traveling wave solutions of non-differentiable type with the generalized functions defined on Cantor sets are analyzed. The results for the non-differentiable solutions when fractal dimension is 1 are also discussed. It is shown that the exact solutions for the local fractional Korteweg-de Vries equation characterize the fractal wave on shallow water surfaces.
On exact traveling-wave solutions for local fractional Korteweg-de Vries equation.
Yang, Xiao-Jun; Tenreiro Machado, J A; Baleanu, Dumitru; Cattani, Carlo
2016-08-01
This paper investigates the Korteweg-de Vries equation within the scope of the local fractional derivative formulation. The exact traveling wave solutions of non-differentiable type with the generalized functions defined on Cantor sets are analyzed. The results for the non-differentiable solutions when fractal dimension is 1 are also discussed. It is shown that the exact solutions for the local fractional Korteweg-de Vries equation characterize the fractal wave on shallow water surfaces.
Theory of viscous transonic flow over airfoils at high Reynolds number
Melnik, R. E.; Chow, R.; Mead, H. R.
1977-01-01
This paper considers viscous flows with unseparated turbulent boundary layers over two-dimensional airfoils at transonic speeds. Conventional theoretical methods are based on boundary layer formulations which do not account for the effect of the curved wake and static pressure variations across the boundary layer in the trailing edge region. In this investigation an extended viscous theory is developed that accounts for both effects. The theory is based on a rational analysis of the strong turbulent interaction at airfoil trailing edges. The method of matched asymptotic expansions is employed to develop formal series solutions of the full Reynolds equations in the limit of Reynolds numbers tending to infinity. Procedures are developed for combining the local trailing edge solution with numerical methods for solving the full potential flow and boundary layer equations. Theoretical results indicate that conventional boundary layer methods account for only about 50% of the viscous effect on lift, the remaining contribution arising from wake curvature and normal pressure gradient effects.
An Adaptive Semi-Implicit Scheme for Simulations of Unsteady Viscous Compressible Flows
Steinthorsson, Erlendur; Modiano, David; Crutchfield, William Y.; Bell, John B.; Colella, Phillip
1995-01-01
A numerical scheme for simulation of unsteady, viscous, compressible flows is considered. The scheme employs an explicit discretization of the inviscid terms of the Navier-Stokes equations and an implicit discretization of the viscous terms. The discretization is second order accurate in both space and time. Under appropriate assumptions, the implicit system of equations can be decoupled into two linear systems of reduced rank. These are solved efficiently using a Gauss-Seidel method with multigrid convergence acceleration. When coupled with a solution-adaptive mesh refinement technique, the hybrid explicit-implicit scheme provides an effective methodology for accurate simulations of unsteady viscous flows. The methodology is demonstrated for both body-fitted structured grids and for rectangular (Cartesian) grids.
Electrokinetic Control of Viscous Fingering
Mirzadeh, Mohammad; Bazant, Martin Z.
2017-10-01
We present a theory of the interfacial stability of two immiscible electrolytes under the coupled action of pressure gradients and electric fields in a Hele-Shaw cell or porous medium. Mathematically, our theory describes a phenomenon of "vector Laplacian growth," in which the interface moves in response to the gradient of a vector-valued potential function through a generalized mobility tensor. Physically, we extend the classical Saffman-Taylor problem to electrolytes by incorporating electrokinetic (EK) phenomena. A surprising prediction is that viscous fingering can be controlled by varying the injection ratio of electric current to flow rate. Beyond a critical injection ratio, stability depends only upon the relative direction of flow and current, regardless of the viscosity ratio. Possible applications include porous materials processing, electrically enhanced oil recovery, and EK remediation of contaminated soils.
Angular dynamics of small crystals in viscous flow
Fries, J.; Einarsson, J.; Mehlig, B.
2017-01-01
The angular dynamics of a very small ellipsoidal particle in a viscous flow decouples from its translational dynamics and the particle angular velocity is given by Jeffery's theory. It is known that cuboid particles share these properties. In the literature a special case is most frequently discussed, namely that of axisymmetric particles with a continuous rotation symmetry. Here we compute the angular dynamics of crystals that possess a discrete rotation symmetry and certain mirror symmetries but do not have a continuous rotation symmetry. We give examples of such particles that nevertheless obey Jeffery's theory. However, there are other examples where the angular dynamics is determined by a more general equation of motion.
Fjords in viscous fingering: selection of width and opening scale
Energy Technology Data Exchange (ETDEWEB)
Mineev-weinstein, Mark [Los Alamos National Laboratory; Ristroph, Leif [UT-AUSTIN; Thrasher, Matthew [UT-AUSTIN; Swinney, Harry [UT-AUSTIN
2008-01-01
Our experiments on viscous fingering of air into oil contained between closely spaced plates reveal two selection rules for the fjords of oil that separate fingers of air. (Fjords are the building blocks of solutions of the zero-surface-tension Laplacian growth equation.) Experiments in rectangular and circular geometries yield fjords with base widths {lambda}{sub c}/2, where {lambda}{sub c} is the most unstable wavelength from a linear stability analysis. Further, fjords open at an angle of 8.0{sup o}{+-}1.0{sup o}. These selection rules hold for a wide range of pumping rates and fjord lengths, widths, and directions.
Viscous heating in fluids with temperature-dependent viscosity: implications for magma flows
Directory of Open Access Journals (Sweden)
A. Costa
2003-01-01
Full Text Available Viscous heating plays an important role in the dynamics of fluids with strongly temperature-dependent viscosity because of the coupling between the energy and momentum equations. The heat generated by viscous friction produces a local temperature increase near the tube walls with a consequent decrease of the viscosity which may dramatically change the temperature and velocity profiles. These processes are mainly controlled by the Peclét number, the Nahme number, the flow rate and the thermal boundary conditions. The problem of viscous heating in fluids was investigated in the past for its practical interest in the polymer industry, and was invoked to explain some rheological behaviours of silicate melts, but was not completely applied to study magma flows. In this paper we focus on the thermal and mechanical effects caused by viscous heating in tubes of finite lengths. We find that in magma flows at high Nahme number and typical flow rates, viscous heating is responsible for the evolution from Poiseuille flow, with a uniform temperature distribution at the inlet, to a plug flow with a hotter layer near the walls. When the temperature gradients induced by viscous heating are very pronounced, local instabilities may occur and the triggering of secondary flows is possible. For completeness, this paper also describes magma flow in infinitely long tubes both at steady state and in transient phase.
Saltzman, Matthew R.; Edwards, Cole T.
2017-04-01
The carbon isotopic composition of the global dissolved inorganic carbon (DIC) reservoir is best estimated from open ocean pelagic carbonate sediments (δ13Ccarb). However, this is not practical for most of geologic time because seafloor subduction has removed the pre-Jurassic record and these time periods may have lacked planktonic calcifying organisms, and therefore shallow water carbonate platform or periplatform sediments are utilized. Shallow water deposits are susceptible to a wide range of post-depositional alteration processes and syn-depositional controls on δ13Ccarb that include carbonate mineralogy, water mass restriction, and a host of related variables (e.g., pH, temperature, organic decomposition, evaporation and CO2 solubility) that can produce local gradients in DIC. The degree to which shallow water δ13C curves diverge from open marine deposits may be critical to understanding how well global carbon cycle isotope mass balance models can predict organic carbon burial rates, but documentation of such divergence is often hindered by factors that limit chronostratigraphic correlation in restricted water masses (e.g., endemic faunas). Here we integrate strontium isotope (87Sr/86Sr) stratigraphy and biostratigraphy to compare δ13C curves in a case study along a depth transect in Middle-Late Ordovician carbonate platform settings. The restricted tidal flat and more open marine deposits are offset by a maximum of ∼2‰ during sea level drop and ∼0‰ during highstand flooding of the platform. Global carbon cycle models such as GEOCARBSULF use published δ13Ccarb curves to drive organic carbon burial rates under the assumption that δ13Ccarb reflects a global seawater signal. We show here the potential pitfalls of using a published δ13Ccarb curve that violates this global assumption. For the 460 million year Middle-Late Ordovician time bin in GEOCARBSULF, improper usage of our locally depleted δ13C curve to drive global organic carbon burial would
FRW Bulk Viscous Cosmology with Modified Chaplygin Gas in Flat Space
Saadat, H
2016-01-01
In this paper we study FRW bulk viscous cosmology in presence of modified Chaplygin gas. We write modified Friedmann equations due to bulk viscosity and Chaplygin gas and obtain time-dependent energy density for the special case of flat space.
Investigation of tool-py friction of viscous textile composites (CD-rom)
Lin, H.; Harrison, P.; van de Haar, K.; Long, A.C.; Akkerman, Remko; Clifford, M.J.; Long, A.
2006-01-01
Dynamic tool-ply friction for a thermoplastic viscous textile composite has been measured using a commercial rotational rheometer as a function of rate, temperature and normal pressure. Results of this novel experimental technique have enabled a general empirical equation to be determined relating
Evolution of basic equations for nearshore wave field
ISOBE, Masahiko
2013-01-01
In this paper, a systematic, overall view of theories for periodic waves of permanent form, such as Stokes and cnoidal waves, is described first with their validity ranges. To deal with random waves, a method for estimating directional spectra is given. Then, various wave equations are introduced according to the assumptions included in their derivations. The mild-slope equation is derived for combined refraction and diffraction of linear periodic waves. Various parabolic approximations and time-dependent forms are proposed to include randomness and nonlinearity of waves as well as to simplify numerical calculation. Boussinesq equations are the equations developed for calculating nonlinear wave transformations in shallow water. Nonlinear mild-slope equations are derived as a set of wave equations to predict transformation of nonlinear random waves in the nearshore region. Finally, wave equations are classified systematically for a clear theoretical understanding and appropriate selection for specific applications. PMID:23318680
Analysis on the Viscous Pumping in a Magnetic Fluid Seal Under a Rotating Load and the Seal Design
長屋, 幸助; 大沼, 浩身; 佐藤,淳
1990-01-01
This paper discusses effects of viscous pumping in a magnetic fluid seal under a rotating load. The Reynolds equation was presented for the seal based on magnetic fluid mechanics, and the expressions for obtaining pressures in the seal, eccentricities of the rotating shaft due to the viscous pumping and seal pressures were given. Numerical Calculations were carried out for some sample problems, and the effect of magnetic flux densities on the pressure in the seal and the seal pressures were c...
Directory of Open Access Journals (Sweden)
Ricardo C. Garla
2017-03-01
Full Text Available ABSTRACT The hunting tactics of lemon sharks, Negaprion brevirostris, are described from underwater and cliff-top observations in the Fernando de Noronha Archipelago, western equatorial Atlantic, Brazil. Two main tactics were observed in the shallow waters of sandy beaches and reefs environments: (i “substrate inspection” of crevices and holes over rocky and reef bottoms, and (ii “sardine blitz”, which refer to striking schools of fishes (mainly sardines in the surf zone. The first tactic was restricted to juveniles up to 2 m of total length, whereas subadult and adult sharks with total length larger than 2 m displayed the second. As lemon sharks use waters less than 5 m depth to hunt, perform social behaviours and predator avoidance, results highlight the importance of properly managing these habitats for their conservation, especially in areas where tourism has increased substantially.
DEFF Research Database (Denmark)
Jansen, Teunis; Kristensen, Kasper; Kainge, Paulus Inekela
2016-01-01
Shallow-water hake (Merluccius capensis) is of considerable ecological and economic importance in the Benguela Current Large Marine Ecosystem in South Africa and Namibia. Optimal management of the resource is currently constrained by the limited understanding of migration patterns and population...... (stock) structure. We combined data from multiple demersal trawl surveys from the entire distribution area to estimate growth rate, mortality and spatial and temporal patterns of M. capensis. Analyses were conducted using the geostatistical model GeoPop. The complexity of the model and the amount of data...... required a new level of soft- and hardware performance. This was achieved by utilizing Template Model Builder and high-end computational hardware (Amazon Elastic Compute Cloud, EC2). The data and the model enabled us to follow the distribution and infer movements of M. capensis from the recruitment...
McFadden, C. S.; Brown, A. S.; Brayton, C.; Hunt, C. B.; van Ofwegen, L. P.
2014-06-01
The application of DNA barcoding to anthozoan cnidarians has been hindered by their slow rates of mitochondrial gene evolution and the failure to identify alternative molecular markers that distinguish species reliably. Among octocorals, however, multilocus barcodes can distinguish up to 70 % of morphospecies, thereby facilitating the identification of species that are ecologically important but still very poorly known taxonomically. We tested the ability of these imperfect DNA barcodes to estimate species richness in a biodiversity survey of the shallow-water octocoral fauna of Palau using multilocus ( COI, mtMutS, 28S rDNA) sequences obtained from 305 specimens representing 38 genera of octocorals. Numbers and identities of species were estimated independently (1) by a taxonomic expert using morphological criteria and (2) by assigning sequences to molecular operational taxonomic units (MOTUs) using predefined genetic distance thresholds. Estimated numbers of MOTUs ranged from 73 to 128 depending on the barcode and distance threshold applied, bracketing the estimated number of 118 morphospecies. Concordance between morphospecies identifications and MOTUs ranged from 71 to 75 % and differed little among barcodes. For the speciose and ecologically dominant genus Sinularia, however, we were able to identify 95 % of specimens correctly simply by comparing mtMutS sequences and in situ photographs of colonies to an existing vouchered database. Because we lack a clear understanding of species boundaries in most of these taxa, numbers of morphospecies and MOTUs are both estimates of the true species diversity, and we cannot currently determine which is more accurate. Our results suggest, however, that the two methods provide comparable estimates of species richness for shallow-water Indo-Pacific octocorals. Use of molecular barcodes in biodiversity surveys will facilitate comparisons of species richness and composition among localities and over time, data that do not
Kim, Hyeonju; Lee, Gwang Hoon; Yi, Bo Yeon; Yoon, Youngho; Kim, Kyong-O.; Kim, Han-Joon; Lee, Sang Hoon
2017-06-01
In high-resolution, shallow-water seismic surveys, correction for water-column height variations caused by tides, weather, and currents is an important part of data processing. In this study, we present a very simple method of correction for profile-length (i.e., long-wavelength) water-column height variations for high-resolution seismic data using a reference bathymetric grid. First, the difference between the depth of the seafloor picked from seismic data and the bathymetry from the bathymetric grid is computed at the locations where the shot points of seismic profiles and the bathymetric grid points are collocated or closest. Then, the results are gridded and smoothed to obtain the profile-length water-column height variations for the survey area. Next, the water-column height variations for each seismic profile are extracted from the smoothed grid and converted to two-way traveltimes. The corrections for the remaining mis-ties at the intersections, computed within a circular region around each tie shot point, are added to the corrections for the water-column height variations. The final, mistie corrected water-column height corrections are loaded to the SEGY trace header of seismic data as a total static. We applied this method to the sparker data acquired from the shallow-water area off the western-central part of Korea where the tidal range is over 7 m. The corrections for water-column height variations range from -10 to 4 m with a median value of about -2 m. Large corrections occur locally between and near the islands probably due to the amplification and shortening in tidal wavelength caused by rapid shoaling toward the islands.
Otake, T.; Sakamoto, Y.; Itoh, S.; Yurimoto, H.; Kakegawa, T.
2012-12-01
*Otake, T. totake@eng.hokudai.ac.jp Div. of Sustainable Resources Engineering, Hokkaido Univ., Sapporo, Japan Sakamoto, Y. yu.sakamoto12@gmail.com Dep. of Earth Science, Tohoku Univ., Sendai, Japan Itoh, S. sitoh@ep.sci.hokudai.ac.jp Dep. of Natural History Sciences, Hokkaido Univ., Sapporo, Japan Yurimoto. H. yuri@ep.sci.hokudai.ac.jp Dep. of Natural History Sciences, Hokkaido Univ., Sapporo, Japan Kakegawa, T. kakegawa@m.tohoku.ac.jp Dep. of Earth Science, Tohoku Univ., Sendai, Japan Geochemical data from ferruginous chemical sedimentary rocks (e.g., Banded Iron Formation: BIF) have been used to reconstruct the surface environments of early Earth. However, only a few studies have investigated the geochemical characteristics of BIFs deposited in a shallow water environment during the Archean, which may have differed from those deposited in a deep water environment. Therefore, we investigated geological, petrographic and geochemical characteristics of ferruginous rocks deposited in a shallow water environment in the Moodies group, in the Barberton Greenstone Belt, South Africa. We obtained ferruginous rock samples in the Moodies group from both an outcrop and underground gold mine, and compared the characteristics of these samples. The 70 sedimentary rock samples were divided into groups based on the dominant Fe minerals they contain: Hematite-rich jaspilite (HM group), Magnetite-rich iron formation/shale/sandstone (MT group), and Siderite-rich sandstone (SD group). Samples in the HM group are predominantly composed of fine-grained quartz (rocks of the Moodies Group. These results suggest that Cr and U were chemically mobile, possibly as oxidized species, in the Earth's surface environment at ~3.2 Ga.
Sintering of polydisperse viscous droplets
Wadsworth, Fabian B.; Vasseur, Jérémie; Llewellin, Edward W.; Dingwell, Donald B.
2017-03-01
Sintering—or coalescence—of compacts of viscous droplets is driven by the interfacial tension between the droplets and the interstitial gas phase. The process, which occurs in a range of industrial and natural settings, such as the manufacture of ceramics and the welding of volcanic ash, causes the compact to densify, to become stronger, and to become less permeable. We investigate the role of droplet polydispersivity in sintering dynamics by conducting experiments in which populations of glass spheres with different size distributions are heated to temperatures above the glass transition interval. We quantify the progress of sintering by tracking changes in porosity with time. The sintering dynamics is modeled by treating the system as a random distribution of interstitial gas bubbles shrinking under the action of interfacial tension only. We identify the scaling between the polydispersivity of the initial droplets and the dynamics of bulk densification. The framework that we develop allows the sintering dynamics of arbitrary polydisperse populations of droplets to be predicted if the initial droplet (or particle) size distribution is known.
Influence of viscous loads on motor planning.
Thoroughman, Kurt A; Wang, Wei; Tomov, Dimitre N
2007-08-01
Here we computationally investigate how encumbering the hand could alter predictions made by the minimum torque change (MTC) and minimum endpoint variance hypotheses (MEPV) of movement planning. After minutes of training, people have made arm trajectories in a robot-generated viscous force field that were similar to previous baseline trajectories without the force field. We simulate the human arm interacting with this viscous load. We found that the viscous forces clearly differentiated MTC and MEPV predictions from both minimum-jerk predictions and from human behavior. We conclude that learned behavior in the viscous environment could arise from minimizing kinematic costs but could not arise from a minimization of either torque change or endpoint variance.
Viscous thread behavior in branching microchannels
Cubaud, Thomas; Hu, Xiaoyi; Sauzade, Martin
2014-11-01
We experimentally study the properties of viscous core-annular flows using miscible fluids in bifurcating microchannels. A viscous filament is first generated using a square hydrodynamic focusing junction by injecting a thick fluid into the central channel and a thin fluid from the side-channels. This method allows us to produce miscible fluid threads of various sizes and lateral positions in the channel, and enables the systematic study of thread transport and stability from low to moderate Reynolds numbers in branching microfluidic networks. We examine, in particular, the role of viscous buckling instabilities on thread behavior and the formation of complex viscous mixtures and stratifications at the small-scale. This work is supported by NSF (CBET-1150389).
Low moduli elastomers with low viscous dissipation
DEFF Research Database (Denmark)
Bejenariu, Anca Gabriela; Yu, Liyun; Skov, Anne Ladegaard
2012-01-01
A controlled reaction schema for addition curing silicones leads to both significantly lower elastic modulus and lower viscous dissipation than for the chemically identical network prepared by the traditional reaction schema....
Non-equilibrium radiation from viscous chemically reacting two-phase exhaust plumes
Penny, M. M.; Smith, S. D.; Mikatarian, R. R.; Ring, L. R.; Anderson, P. G.
1976-01-01
A knowledge of the structure of the rocket exhaust plumes is necessary to solve problems involving plume signatures, base heating, plume/surface interactions, etc. An algorithm is presented which treats the viscous flow of multiphase chemically reacting fluids in a two-dimensional or axisymmetric supersonic flow field. The gas-particle flow solution is fully coupled with the chemical kinetics calculated using an implicit scheme to calculate chemical production rates. Viscous effects include chemical species diffusion with the viscosity coefficient calculated using a two-equation turbulent kinetic energy model.
Numerical Investigation of Damping of Torsional Beam Vibrations by Viscous Bimoments
DEFF Research Database (Denmark)
Hoffmeyer, David; Høgsberg, Jan Becker
2017-01-01
Damping of torsional beam vibrations of slender beam–structures with thin–walled cross–sections is investigated. Analytical results from solving the differential equation governing torsion with viscous bimoments imposed at the boundary, are compared with a numerical approach with three......–dimensional, is oparametric elements. The viscous bimoments act on the axial warping displacements associated with in homogeneous torsion, and are in a numerical format realized by suitable configurations of concentrated, axial forces describing discrete dampers.It is illustrated by an example that significant damping ratios...
Diffusion and viscous flow in bulk glass forming alloys
Energy Technology Data Exchange (ETDEWEB)
Bartsch, A.; Zoellmer, V.; Raetzke, K. [Institut fuer Materialwissenschaft - Materialverbunde, Technische Fakultaet, Christian-Albrechts Universitaet zu Kiel, Kaiserstr. 2, 24143 Kiel (Germany); Meyer, A. [Institut fuer Materialphysik im Weltraum, Deutsches Zentrum fuer Luft- und Raumfahrt (DLR), 51170 Koeln (Germany); Faupel, F., E-mail: ff@tf.uni-kiel.de [Institut fuer Materialwissenschaft - Materialverbunde, Technische Fakultaet, Christian-Albrechts Universitaet zu Kiel, Kaiserstr. 2, 24143 Kiel (Germany)
2011-06-15
Research highlights: > We measured radiotracer diffusivities of all components in a Pd{sub 43}Cu{sub 27}Ni{sub 10}P{sub 20} melt. > We see a vast decoupling between the diffusivity of Pd and of the smaller components at T{sub g}. > We see no decoupling between Pd diffusion and viscous flow. > The Stokes-Einstein equations holds for Pd in the hole supercooled range. > Pd forms a slow subsystem. - Abstract: We review radiotracer diffusion and isotope measurements in bulk glass forming alloys from the glassy state to the equilibrium melt and compare diffusion and viscous flow. In the glassy as well as in the deeply supercooled state below the critical temperature T{sub c}, where the mode coupling theory predicts a freezing-in of liquid-like motion, very small isotope effects indicate a highly collective hopping mechanism. Not only in the glassy state but also in the supercooled state below T{sub c} the temperature dependence of diffusion is Arrhenius-like with an effective activation enthalpy. A clear decoupling takes place between the diffusivities of the individual components of the alloys and between time scales related to diffusive transport and viscous flow. While the component decoupling is small for the smaller components a vast decoupling of more than 4 orders of magnitude is observed in Pd-Cu-Ni-P alloys between the diffusivity of the large majority component Pd and of the smaller components at the glass transition temperature T{sub g}. The diffusivities of all components merge close to the critical temperature T{sub c} of mode coupling theory. Above T{sub c}, the onset of liquid-like motion is directly evidenced by a gradual drop of the effective activation energy. This strongly supports the mode coupling scenario. The isotope effect measurements show atomic transport up to the equilibrium melt to be far away from the regime of uncorrelated binary collisions. For Pd, in contrast to the behavior of single component molecular glass formers, the Stokes
Gottlieb, D.; Turkel, E.
1980-01-01
New methods are introduced for the time integration of the Fourier and Chebyshev methods of solution for dynamic differential equations. These methods are unconditionally stable, even though no matrix inversions are required. Time steps are chosen by accuracy requirements alone. For the Fourier method both leapfrog and Runge-Kutta methods are considered. For the Chebyshev method only Runge-Kutta schemes are tested. Numerical calculations are presented to verify the analytic results. Applications to the shallow water equations are presented.
Golitsyn, G. S.
1977-01-01
The main results were the formulas for the mean convection velocities, of a viscous fluid and for the mean temperature difference in the bulk of the convecting fluid. These were obtained: by scaling analysis of the Boussinesq equations, by analysis of the energetics of the process, and by using similarity and dimensional arguments. The last approach defines the criteria of similarity and allows the proposition of some self-similarity hypotheses. By several simple new ways, an expression for the efficiency coefficient gamma of the thermal convection was also obtained. An analogy is pointed out between non-turbulent convection of a viscous fluid and the structure of turbulence for scales less than Kolmogorov's internal viscous microscale of turbulence.
Viscous Dissipation and Criticality of Subducting Slabs
Riedel, Mike; Karato, Shun; Yuen, Dave
2016-04-01
Rheology of subducting lithosphere appears to be complicated. In the shallow part, deformation is largely accomodated by brittle failure, whereas at greater depth, at higher confining pressures, ductile creep is expected to control slab strength. The amount of viscous dissipation ΔQ during subduction at greater depth, as constrained by experimental rock mechanics, can be estimated on the basis of a simple bending moment equation [1,2] 2ɛ˙0(z) ∫ +h/2 2 M (z) = h ṡ -h/2 4μ(y,z)y dy , (1) for a complex multi-phase rheology in the mantle transition zone, including the effects of a metastable phase transition as well as the pressure, temperature, grain-size and stress dependency of the relevant creep mechanisms; μ is here the effective viscosity and ɛ˙0(z) is a (reference) strain rate. Numerical analysis shows that the maximum bending moment, Mcrit, that can be sustained by a slab is of the order of 1019 Nm per m according to Mcrit˜=σp ∗h2/4, where σp is the Peierl's stress limit of slab materials and h is the slab thickness. Near Mcrit, the amount of viscous dissipation grows strongly as a consequence of a lattice instability of mantle minerals (dislocation glide in olivine), suggesting that thermo-mechanical instabilities become prone to occur at places where a critical shear-heating rate is exceeded, see figure. This implies that the lithosphere behaves in such cases like a perfectly plastic solid [3]. Recently available detailed data related to deep seismicity [4,5] seems to provide support to our conclusion. It shows, e.g., that thermal shear instabilities, and not transformational faulting, is likely the dominating mechanism for deep-focus earthquakes at the bottom of the transition zone, in accordance with this suggested "deep criticality" model. These new findings are therefore briefly outlined and possible implications are discussed. References [1] Riedel, M. R., Karato, S., Yuen, D. A. Criticality of Subducting Slabs. University of Minnesota
DYNAMICS OF THIN VISCOUS LAYERS
ROJAS, NICOLAS
2011-01-01
As Isaac Newton discovered in Mechanics, and published in his Principia Mathematica in 1687, inertial effects are essential to describe natural phenomena. In the case of Fluid Dynamics, inertia was included by Claude-Louis Navier and George Gabriel Stokes almost two centuries after in 1822 when calculating the mass and momentum conservation of au infinitesimal fluid elemeut. Although Navier-Stokes equations are very useful for describing any event of any liquid or gas and there...
Directory of Open Access Journals (Sweden)
C. Lauvernet
2018-01-01
Full Text Available Vegetative filter strips are often used for protecting surface waters from pollution transferred by surface runoff in agricultural watersheds. In Europe, they are often prescribed along the stream banks, where a seasonal shallow water table (WT could decrease the buffer zone efficiency. In spite of this potentially important effect, there are no systematic experimental or theoretical studies on the effect of this soil boundary condition on the VFS efficiency. In the companion paper (Muñoz-Carpena et al., 2018, we developed a physically based numerical algorithm (SWINGO that allows the representation of soil infiltration with a shallow water table. Here we present the dynamic coupling of SWINGO with VFSMOD, an overland flow and transport mathematical model to study the WT influence on VFS efficiency in terms of reductions of overland flow, sediment, and pesticide transport. This new version of VFSMOD was applied to two contrasted benchmark field studies in France (sandy-loam soil in a Mediterranean semicontinental climate, and silty clay in a temperate oceanic climate, where limited testing of the model with field data on one of the sites showed promising results. The application showed that for the conditions of the studies, VFS efficiency decreases markedly when the water table is 0 to 1.5 m from the surface. In order to evaluate the relative importance of WT among other input factors controlling VFS efficiency, global sensitivity and uncertainty analysis (GSA was applied on the benchmark studies. The most important factors found for VFS overland flow reduction were saturated hydraulic conductivity and WT depth, added to sediment characteristics and VFS dimensions for sediment and pesticide reductions. The relative importance of WT varied as a function of soil type (most important at the silty-clay soil and hydraulic loading (rainfall + incoming runoff at each site. The presence of WT introduced more complex responses dominated by strong
Starek, M. J.
2016-02-01
Small-scale Unmanned Aircraft Systems (UAS) enable the integration of light weight, low-cost imaging payloads providing a flexible and efficient means for conducting localized littoral surveys. Through exploitation of high imagery overlap and minimal aiding technology, photogrammetric techniques and structure from motion (SfM) methods can be applied to derive accurate 2D and 3D geospatial data about the observed terrain. Furthermore, small-scale UAS enable rapid response capabilities and provide the potential for collecting repeated observations at high temporal frequency making them an exceptional tool for monitoring dynamic coastal environments. This study examines the accuracy of topographic and bathymetric data derived from a UAS-based photogrammetric survey of a low-energy, shallow-water littoral zone. The study site is, an engineered and restored beach, located on Ward Island in Corpus Christi Bay, TX. Two UAS surveys were conducted roughly two months apart using a system called the SenseFly eBee. The eBee is an ultra-lightweight ( 0.7 kg) fully autonomous platform and it was equipped with a 16 megapixel RGB camera. The objectives were to: (1) assess accuracy differences in SfM derived point clouds over exposed and submerged beach; (2) evaluate effects of scene-to-scene variability and flight design on derived data products. Several key components were analyzed in order to assess the accuracy and usefulness of elevation data derived from the UAS/SfM approach. First, a sensitivity analysis was conducted to examine the impacts of image scale and match constraints on the fidelity of 3D point cloud data derived from the SfM processing workflow. Evaluation focused on differences in accuracy and density of point data over exposed and submerged beach. Second, a noise filter was developed to remove non-subtrate returns from the SfM cloud for bathymetric modeling. Finally, a bathymetric inversion approach was applied to derive an estimate of water depth. Results show
Directory of Open Access Journals (Sweden)
Kumar Hitesh
2009-01-01
Full Text Available The boundary layer steady flow and heat transfer of a viscous incompressible fluid due to a stretching plate with viscous dissipation effect in the presence of a transverse magnetic field is studied. The equations of motion and heat transfer are reduced to non-linear ordinary differential equations and the exact solutions are obtained using properties of confluent hypergeometric function. It is assumed that the prescribed heat flux at the stretching porous wall varies as the square of the distance from origin. The effects of the various parameters entering into the problem on the velocity field and temperature distribution are discussed.
Simulation of viscous flows using a multigrid-control volume finite element method
Energy Technology Data Exchange (ETDEWEB)
Hookey, N.A. [Memorial Univ., Newfoundland (Canada)
1994-12-31
This paper discusses a multigrid control volume finite element method (MG CVFEM) for the simulation of viscous fluid flows. The CVFEM is an equal-order primitive variables formulation that avoids spurious solution fields by incorporating an appropriate pressure gradient in the velocity interpolation functions. The resulting set of discretized equations is solved using a coupled equation line solver (CELS) that solves the discretized momentum and continuity equations simultaneously along lines in the calculation domain. The CVFEM has been implemented in the context of both FMV- and V-cycle multigrid algorithms, and preliminary results indicate a five to ten fold reduction in execution times.
Divergence-Free SPH for Incompressible and Viscous Fluids.
Bender, Jan; Koschier, Dan
2017-03-01
In this paper we present a novel Smoothed Particle Hydrodynamics (SPH) method for the efficient and stable simulation of incompressible fluids. The most efficient SPH-based approaches enforce incompressibility either on position or velocity level. However, the continuity equation for incompressible flow demands to maintain a constant density and a divergence-free velocity field. We propose a combination of two novel implicit pressure solvers enforcing both a low volume compression as well as a divergence-free velocity field. While a compression-free fluid is essential for realistic physical behavior, a divergence-free velocity field drastically reduces the number of required solver iterations and increases the stability of the simulation significantly. Thanks to the improved stability, our method can handle larger time steps than previous approaches. This results in a substantial performance gain since the computationally expensive neighborhood search has to be performed less frequently. Moreover, we introduce a third optional implicit solver to simulate highly viscous fluids which seamlessly integrates into our solver framework. Our implicit viscosity solver produces realistic results while introducing almost no numerical damping. We demonstrate the efficiency, robustness and scalability of our method in a variety of complex simulations including scenarios with millions of turbulent particles or highly viscous materials.
Viscous self interacting dark matter and cosmic acceleration
Atreya, Abhishek; Bhatt, Jitesh R.; Mishra, Arvind
2018-02-01
Self interacting dark matter (SIDM) provides us with a consistent solution to certain astrophysical observations in conflict with collision-less cold DM paradigm. In this work we estimate the shear viscosity (η) and bulk viscosity (ζ) of SIDM, within kinetic theory formalism, for galactic and cluster size SIDM halos. To that extent we make use of the recent constraints on SIDM cross-section for the dwarf galaxies, LSB galaxies and clusters. We also estimate the change in solution of Einstein's equation due to these viscous effects and find that σ/m constraints on SIDM from astrophysical data provide us with sufficient viscosity to account for the observed cosmic acceleration at present epoch, without the need of any additional dark energy component. Using the estimates of dark matter density for galactic and cluster size halo we find that the mean free path of dark matter ~ few Mpc. Thus the smallest scale at which the viscous effect start playing the role is cluster scale. Astrophysical data for dwarf, LSB galaxies and clusters also seems to suggest the same. The entire analysis is independent of any specific particle physics motivated model for SIDM.
The application of preconditioning in viscous flows
Energy Technology Data Exchange (ETDEWEB)
Choi, Y.H. (NASA Lewis Research Center, Cleveland, OH (United States)); Merkle, C.L. (The Pennsylvania State Univ., University Park (United States))
1993-04-01
A time-derivative preconditioning algorithm that is effective over a wide range of flow conditions from inviscid to very diffusive flows and from low speed to supersonic flows has been developed. The algorithm uses a preconditioning matrix that introduces well-conditioned eigen values while simultaneously avoiding nonphysical time reversals for viscous flows. The resulting algorithm also provides a mechanism for controlling the inviscid and viscous time step parameters at very diffusive flows, thereby ensuring rapid convergence for very viscous flows as well as for inviscid flows. Computational capabilities are demonstrated through computation of a wide variety of problems. Convergence rates are shown to be accelerated by as much as two orders of magnitudes, while providing solutions that are identical to those obtained without preconditioning method. 26 refs., 21 figs.
Energy Technology Data Exchange (ETDEWEB)
Verma, Devendra; Tomar, Vikas, E-mail: tomar@purdue.edu
2015-04-01
This investigation reports a comparison of the exoskeleton mechanical strength of deep sea shrimp species Rimicaris exoculata and shallow water shrimp species Pandalus platyceros at temperatures ranging from 25 °C to 80 °C using nanoindentation experiments. Scanning Electron Microscopy (SEM) observations suggest that both shrimp exoskeletons have the Bouligand structure. Differences in the structural arrangement and chemical composition of both shrimps are highlighted by SEM and EDX (Energy Dispersive X-ray) analyses. The variation in the elastic moduli with temperature is found to be correlated with the measured compositional differences. The reduced modulus of R. exoculata is 8.26 ± 0.89 GPa at 25 °C that reduces to 7.61 ± 0.65 GPa at 80 °C. The corresponding decrease in the reduced modulus of P. platyceros is from 27.38 ± 2.3 GPa at 25 °C to 24.58 ± 1.71 GPa at 80 °C. The decrease in reduced moduli as a function of temperature is found to be dependent on the extent of calcium based minerals in exoskeleton of both types of shrimp exoskeletons. - Highlights: • Shrimp species Pandalus platyceros and Rimicaris exoculata exoskeletons are analyzed. • Temperature dependent properties of shrimp exoskeleton are compared. • Mechanical properties are correlated with structure and composition of exoskeleton. • Mechanical properties reduce with increase in temperature. • Presence of biominerals gives better thermal stability to structure.
Directory of Open Access Journals (Sweden)
Eydis Einarsdottir
2017-02-01
Full Text Available Twenty-eight sponge specimens were collected at a shallow water hydrothermal vent site north of Iceland. Extracts were prepared and tested in vitro for cytotoxic activity, and eight of them were shown to be cytotoxic. A mass spectrometry (MS-based metabolomics approach was used to determine the chemical composition of the extracts. This analysis highlighted clear differences in the metabolomes of three sponge specimens, and all of them were identified as Haliclona (Rhizoniera rosea (Bowerbank, 1866. Therefore, these specimens were selected for further investigation. Haliclona rosea metabolomes contained a class of potential key compounds, the 3-alkyl pyridine alkaloids (3-APA responsible for the cytotoxic activity of the fractions. Several 3-APA compounds were tentatively identified including haliclamines, cyclostellettamines, viscosalines and viscosamines. Among these compounds, cyclostellettamine P was tentatively identified for the first time by using ion mobility MS in time-aligned parallel (TAP fragmentation mode. In this work, we show the potential of applying metabolomics strategies and in particular the utility of coupling ion mobility with MS for the molecular characterization of sponge specimens.
Rakociński, Michał; Racki, Grzegorz
2016-01-01
Microbial carbonates, consisting of abundant girvanellid oncoids, are described from cephalopod-crinoid and crinoid-brachiopod coquinas (rudstones) occurring in the lowermost Famennian of the Holy Cross Mountains, Poland. A Girvanella-bearing horizon (consist with numerous girvanellid oncoids) has been recognised at the Psie Górki section, and represents the northern slope succession of the drowned Dyminy Reef. This occurrence of microbialites in the aftermath of the Frasnian-Famennian event is interpreted as the result of opportunistic cyanobacteria blooms, which, as 'disaster forms', colonised empty shallow-water ecological niches during the survival phase following the Frasnian metazoan reef collapse, due to collapsed activity of epifaunal, grazing, and/or burrowing animals. The anachronistic lithofacies at Psie Górki is linked with catastrophic mass mortality of the cephalopod and crinoid-brachiopod communities during the heavy storm events. This mass occurrence of girvanellid oncoids, along with Frutexites-like microbial shrubs and, at least partly, common micritisation of some skeletal grains, records an overall increase in microbial activity in eutrophic normal marine environments. Microbial communities in the Holy Cross Mountains are not very diverse, being mainly represented by girvanellid oncoids, and stand in contrast to the very rich microbial communities known from the Guilin area (China), Canning Basin (Australia) and the Timan-northern Ural area (Russia). The association from Poland is similar to more diverse microbial communities represented by oncoids, trombolites and stromatolites, well known from the Canadian Alberta basin.
Renegar, D Abigail; Turner, Nicholas R; Riegl, Bernhard M; Dodge, Richard E; Knap, Anthony H; Schuler, Paul A
2017-01-01
Previous research evaluating hydrocarbon toxicity to corals and coral reefs has generally focused on community-level effects, and results often are not comparable between studies because of variability in hydrocarbon exposure characterization and evaluation of coral health and mortality during exposure. Toxicity of the polycyclic aromatic hydrocarbon 1-methylnaphthalene to the coral Porites divaricata was assessed in a constant exposure toxicity test utilizing a novel toxicity testing protocol uniquely applicable to shallow-water corals, which considered multiple assessment metrics and evaluated the potential for post-exposure mortality and/or recovery. Acute and subacute effects (gross morphological changes, photosynthetic efficiency, mortality, and histologic cellular changes) were evaluated during pre-exposure (4 wk), exposure (48 h), and post-exposure recovery (4 wk) periods. Coral condition scores were used to determine a 48-h median effective concentration of 7442 μg/L. Significant physical and histological changes resulted from exposure to 640 μg/L and 5427 μg/L 1-methylnaphthalene, with a 1-d to 3-d delay in photosynthetic efficiency effects (ΔF/Fm). Pigmented granular amoebocyte area was found to be a potentially useful sublethal endpoint for this species. Coral mortality was used to estimate a 48-h median lethal concentration of 12 123 μg/L. Environ Toxicol Chem 2017;36:212-219. © 2016 SETAC. © 2016 SETAC.
Saylam, Kutalmis; Brown, Rebecca A.; Hupp, John R.
2017-06-01
Airborne Lidar bathymetry (ALB) is an effective and a rapidly advancing technology for mapping and characterizing shallow coastal water zones as well as inland fresh-water basins such as rivers and lakes. The ability of light beams to detect and traverse shallow water columns has provided valuable information about unmapped and often poorly understood coastal and inland water bodies of the world. Estimating ALB survey results at varying water clarity and depth conditions is essential for realizing project expectations and preparing budgets accordingly. In remote locations of the world where in situ water clarity measurements are not feasible or possible, using multiband satellite imagery can be an effective tool for estimating and addressing such considerations. For this purpose, we studied and classified reflected electromagnetic energy from selected water bodies acquired by RapidEye sensor and then correlated findings with ALB survey results. This study was focused not on accurately measuring depth from optical bathymetry but rather on using multiband satellite imagery to quickly predict ALB survey results and identify potentially turbid water bodies with limited depth penetration. For this study, we constructed an in-house algorithm to confirm ALB survey findings using bathymetric waveform information. The study findings are expected to contribute to the ongoing understanding of forecasting ALB survey expectations in unknown and varying water conditions, especially in remote and inaccessible parts of the world.
Directory of Open Access Journals (Sweden)
Anna Józefczuk
2003-06-01
Full Text Available The idea of the study was to describe short-term and seasonal variationsin the composition and abundance of zooplankton in the coastal area of theGulf of Gdansk at two shore stations and the influence of selectedenvironmental factors (temperature, salinity, wind velocity on it. The studieswere based on material collected in the shallow waters of the Gulf of Gdanskfrom stations located by the Marine Promenade (Bulwar Nadmorski in Gdynia andthe pier in Sopot. Samples were collected in 2001 mainly at weekly intervalsusing an open-type plankton net. Environmental parameters were measured at thesame time. The zooplankton at the Gdynia and Sopot stations consisted of30 taxa; Rotatoria, Copepoda and meroplankton were dominants.There was a much higher percentage of Rotatoria and a lower percentage of meroplankton at Sopot than at Gdynia. Considerable differences were apparent in the numbers ofparticular groups of zooplankton at these stations in the same periods.Simpson's biodiversity index, here based on the zooplankton of the shallowwaters off Gdynia and Sopot, was relatively high most of the time.Diversity of mesozooplankton was greatest in July and October. There was a significantcorrelation between the abundance of mesozooplankton and environmental factorsin the case of cladoceran and polychaete larvae. Frequent studies at stationslocated close to each other illustrate the highly dynamic range of variationsoccurring in the coastal area: the concentrations of particular organismsfluctuated very considerably from one week to another, even by a factor ofseveral dozen. Nevertheless, the statistically mean numbers of zooplankton atboth stations are comparable.
Verma, Devendra; Tomar, Vikas
2015-04-01
This investigation reports a comparison of the exoskeleton mechanical strength of deep sea shrimp species Rimicaris exoculata and shallow water shrimp species Pandalus platyceros at temperatures ranging from 25°C to 80°C using nanoindentation experiments. Scanning Electron Microscopy (SEM) observations suggest that both shrimp exoskeletons have the Bouligand structure. Differences in the structural arrangement and chemical composition of both shrimps are highlighted by SEM and EDX (Energy Dispersive X-ray) analyses. The variation in the elastic moduli with temperature is found to be correlated with the measured compositional differences. The reduced modulus of R. exoculata is 8.26±0.89GPa at 25°C that reduces to 7.61±0.65GPa at 80°C. The corresponding decrease in the reduced modulus of P. platyceros is from 27.38±2.3GPa at 25°C to 24.58±1.71GPa at 80°C. The decrease in reduced moduli as a function of temperature is found to be dependent on the extent of calcium based minerals in exoskeleton of both types of shrimp exoskeletons. Copyright © 2015 Elsevier B.V. All rights reserved.
Zhang, Yanjie; Sun, Jin; Chen, Chong; Watanabe, Hiromi K.; Feng, Dong; Zhang, Yu; Chiu, Jill M. Y.; Qian, Pei-Yuan; Qiu, Jian-Wen
2017-04-01
Polynoid scale worms (Polynoidae, Annelida) invaded deep-sea chemosynthesis-based ecosystems approximately 60 million years ago, but little is known about their genetic adaptation to the extreme deep-sea environment. In this study, we reported the first two transcriptomes of deep-sea polynoids (Branchipolynoe pettiboneae, Lepidonotopodium sp.) and compared them with the transcriptome of a shallow-water polynoid (Harmothoe imbricata). We determined codon and amino acid usage, positive selected genes, highly expressed genes and putative duplicated genes. Transcriptome assembly produced 98,806 to 225,709 contigs in the three species. There were more positively charged amino acids (i.e., histidine and arginine) and less negatively charged amino acids (i.e., aspartic acid and glutamic acid) in the deep-sea species. There were 120 genes showing clear evidence of positive selection. Among the 10% most highly expressed genes, there were more hemoglobin genes with high expression levels in both deep-sea species. The duplicated genes related to DNA recombination and metabolism, and gene expression were only enriched in deep-sea species. Deep-sea scale worms adopted two strategies of adaptation to hypoxia in the chemosynthesis-based habitats (i.e., rapid evolution of tetra-domain hemoglobin in Branchipolynoe or high expression of single-domain hemoglobin in Lepidonotopodium sp.).
Energy Technology Data Exchange (ETDEWEB)
Sugimoto, Norihiko, E-mail: nori@phys-h.keio.ac.jp [Department of Physics, Research and Education Center for Natural Sciences, Keio University, 4-1-1 Hiyoshi, Kouhoku-ku, Yokohama, Kanagawa 223-8521 (Japan)
2015-12-15
Inertia-gravity wave radiation from the merging of two co-rotating vortices is investigated numerically in a rotating shallow water system in order to focus on cyclone–anticyclone asymmetry at different values of the Rossby number (Ro). A numerical study is conducted on a model using a spectral method in an unbounded domain to estimate the gravity wave flux with high accuracy. Continuous gravity wave radiation is observed in three stages of vortical flows: co-rotating of the vortices, merging of the vortices, and unsteady motion of the merged vortex. A cyclone–anticyclone asymmetry appears at all stages at smaller Ro (≤20). Gravity waves from anticyclones are always larger than those from cyclones and have a local maximum at smaller Ro (∼2) compared with that for an idealized case of a co-rotating vortex pair with a constant rotation rate. The source originating in the Coriolis acceleration has a key role in cyclone–anticyclone asymmetry in gravity waves. An additional important factor is that at later stages, the merged axisymmetric anticyclone rotates faster than the elliptical cyclone due to the effect of the Rossby deformation radius, since a rotation rate higher than the inertial cutoff frequency is required to radiate gravity waves.
Directory of Open Access Journals (Sweden)
François Clayer
2014-12-01
Full Text Available The near-field stratigraphic record of the Early Silurian glaciations is well documented in the literature. Data from far-field areas are, however, sparse. One of the best far-field stratigraphic records of these Llandovery glaciations is exposed on Anticosti Island in eastern Canada. Eight shallow-water paleotropical facies are present close to the mid-Telychian Jupiter–Chicotte formational boundary along the south-central coast of Anticosti Island. These can be grouped into three facies associations that include, from bottom to top: a carbonate facies association (FA-1, a mixed siliciclastic and carbonate facies association (FA-2 and an encrinitic facies association (FA-3. These mid- to outer-ramp strata represent deposition mostly from episodic, high-energy storm events as evidenced by their sharp bases, hummocky cross-stratification, large wave ripples, gutter casts and wave-enhanced sediment gravity flow deposits. Superimposed on a long-term regressive trend, one main transgressive–regressive (TR sequence and four meter-scale TR cycles are evident, indicating a multi-order stratigraphic framework developed under the influence of glacio-eustasy. The Jupiter–Chicotte formational boundary, a regional discontinuity surface caused by a forced regression, corresponds to the onset of a far-field mid-Telychian glaciation.
Chichvarkhin, Anton
2016-01-01
The coast of northern Primorye region, north of Peter the Great Bay has been sparsely studied in regards to its molluscan fauna, with just a few works reviewing the distribution of local mollusks. This work presents a survey of the shallow water heterobranch sea slugs currently occurring around Kievka Bay to Oprichnik Bay, Russia. Thirty-nine species of sea slugs were found in this study and the new species Cadlina olgae sp. nov., described herein. Most (24) of the species occurring in the area have widespread ranges in the northern Pacific Ocean. The eight species are endemic for the Sea of Japan and adjacent part of the Sea of Okhotsk. Seven other occur also in northern Atlantic and Arctic waters. Thirteen found species are not known from Peter the Great Bay but known from adjacent northern Pacific waters. The finding of a previously undescribed species emphasizes the need of further surveys, particularly in subtidal and deeper waters, in order to improve the knowledge on this neglected fauna in Primorye.
Derivation of asymptotic two-dimensional time-dependent equations for ocean wave propagation
Lannes, David
2007-01-01
A general method for the derivation of asymptotic nonlinear shallow water and deep water models is presented. Starting from a general dimensionless version of the water-wave equations, we reduce the problem to a system of two equations on the surface elevation and the velocity potential at the free surface. These equations involve a Dirichlet-Neumann operator and we show that all the asymptotic models can be recovered by a simple asymptotic expansion of this operator, in function of the shallowness parameter (shallow water limit) or the steepness parameter (deep water limit). Based on this method, a new two-dimensional fully dispersive model for small wave steepness is also derived, which extends to uneven bottom the approach developed by Matsuno \\cite{matsuno3} and Choi \\cite{choi}. This model is still valid in shallow water but with less precision than what can be achieved with Green-Naghdi model, when fully nonlinear waves are considered. The combination, or the coupling, of the new fully dispersive equati...
Stability analysis of bulk viscous anisotropic universe model
Sharif, M.; Mumtaz, Saadia
2017-11-01
This paper is devoted to study the phase space analysis of locally rotationally symmetric Bianchi type I universe model by taking three different cases for bulk viscosity coefficient. An autonomous system of equations is established by defining normalized dimensionless variables. In order to investigate stability of the system, we evaluate corresponding critical points for different values of the parameters. In the case of bulk viscous matter and radiation, the parameters η=η0 and m≥0.8 show realistic evolution of the universe (prior radiation dominated era, conventional decelerated matter dominated state and ultimately accelerated expansion). We conclude that stable solutions exist in the presence of bulk viscosity with different choices of parameter m.
Mathematical theory of compressible viscous fluids analysis and numerics
Feireisl, Eduard; Pokorný, Milan
2016-01-01
This book offers an essential introduction to the mathematical theory of compressible viscous fluids. The main goal is to present analytical methods from the perspective of their numerical applications. Accordingly, we introduce the principal theoretical tools needed to handle well-posedness of the underlying Navier-Stokes system, study the problems of sequential stability, and, lastly, construct solutions by means of an implicit numerical scheme. Offering a unique contribution – by exploring in detail the “synergy” of analytical and numerical methods – the book offers a valuable resource for graduate students in mathematics and researchers working in mathematical fluid mechanics. Mathematical fluid mechanics concerns problems that are closely connected to real-world applications and is also an important part of the theory of partial differential equations and numerical analysis in general. This book highlights the fact that numerical and mathematical analysis are not two separate fields of mathematic...
Viscous Rayleigh-Taylor instability in spherical geometry
Mikaelian, Karnig O.
2016-02-01
We consider viscous fluids in spherical geometry, a lighter fluid supporting a heavier one. Chandrasekhar [Q. J. Mech. Appl. Math. 8, 1 (1955), 10.1093/qjmam/8.1.1] analyzed this unstable configuration providing the equations needed to find, numerically, the exact growth rates for the ensuing Rayleigh-Taylor instability. He also derived an analytic but approximate solution. We point out a weakness in his approximate dispersion relation (DR) and offer a somewhat improved one. A third DR, based on transforming a planar DR into a spherical one, suffers no unphysical predictions and compares reasonably well with the exact work of Chandrasekhar and a more recent numerical analysis of the problem [Terrones and Carrara, Phys. Fluids 27, 054105 (2015), 10.1063/1.4921648].
Evolution of a universe filled with a causal viscous fluid
Chimento, Luis P
2012-01-01
The behaviour of solutions to the Einstein equations with a causal viscous fluid source is investigated. In this model we consider a spatially flat Robertson-Walker metric, the bulk viscosity coefficient is related to the energy density as $\\zeta = \\alpha \\rho^{m}$, and the relaxation time is given by $\\zeta/\\rho$. In the case $m = 1/2$ we find the exact solutions and we verify whether they satisfy the energy conditions. Besides, we study analytically the asymptotic stability of several families of solutions for arbitrary $m$. We find that the qualitative asymptotic behaviour in the far future is not altered by relaxation processes, but they change the behaviour in the past, introducing singular instead of deflationary evolutions or making the Universe bounce due to the violation of the energy conditions.
Bulk Viscous Matter-dominated Universes: Asymptotic Properties
Avelino, Arturo; Gonzalez, Tame; Nucamendi, Ulises; Quiros, Israel
2013-01-01
By means of a combined study of the type Ia supernovae test,together with a study of the asymptotic properties in the equivalent phase space -- through the use of the dynamical systems tools -- we demonstrate that the bulk viscous matter-dominated scenario is not a good model to explain the accepted cosmological paradigm, at least, under the parametrization of bulk viscosity considered in this paper. The main objection against such scenarios is the absence of conventional radiation and matter-dominated critical points in the phase space of the model. This entails that radiation and matter dominance are not generic solutions of the cosmological equations, so that these stages can be implemented only by means of very particular solutions. Such a behavior is in marked contradiction with the accepted cosmological paradigm which requires of an earlier stage dominated by relativistic species, followed by a period of conventional non-relativistic matter domination, during which the cosmic structure we see was formed...
Perturbational self-similar solutions for multi-dimensional Camassa-Holm-type equations
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Hongli An
2017-02-01
Full Text Available In this article, we sutdy a multi-component Camassa-Holm-type system. By employing the characteristic method, we obtain a class of perturbational self-similar solutions with elliptical symmetry, whose velocity components are governed by the generalized Emden equations. In particular, when n=1, these solutions constitute a generalization of that obtained by Yuen in [38]. Interestingly, numerical simulations show that the analytical solutions obtained can be used to describe the drifting phenomena of shallow water flows. In addition, the method proposed can be extended to other mathematical physics models such as higher-dimensional Hunter-Saxton equations and Degasperis-Procesi equations.
Traveling Wave Solutions of Space-Time Fractional Generalized Fifth-Order KdV Equation
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Dianchen Lu
2017-01-01
Full Text Available The Korteweg-de Vries (KdV equation, especially the fractional higher order one, provides a relatively accurate description of motions of long waves in shallow water under gravity and wave propagation in one-dimensional nonlinear lattice. In this article, the generalized exp(-Φ(ξ-expansion method is proposed to construct exact solutions of space-time fractional generalized fifth-order KdV equation with Jumarie’s modified Riemann-Liouville derivatives. At the end, three types of exact traveling wave solutions are obtained which indicate that the method is very practical and suitable for solving nonlinear fractional partial differential equations.
Bulk viscous cosmology in early Universe
Indian Academy of Sciences (India)
the introduction of viscosity affects the appearance of singularity, is briefly discussed in particular solutions. The deceleration parameter has a freedom to vary with the scale factor of the model, which describes the accelerating expansion of the Universe. Keywords. Cosmology; viscous Universe; radiation phase; inflationary ...
Viscous fingering with partially miscible fluids
Fu, X.; Cueto-Felgueroso, L.; Juanes, R.
2015-12-01
When a less viscous fluid displaces a more viscous fluid, the contrast in viscosity destabilizes the interface between the two fluids, leading to the formation of fingers. Experimental and numerical studies of viscous fingering have focused on fluids that are either fully miscible (e.g. water and glycerol) or perfectly immiscible (e.g. water and oil). In practice, however, the miscibility of two fluids can change appreciably with temperature and pressure, and often falls into the case of partial miscibility, where two fluids have limited solubility in each other (e.g. CO2 and water). Following our recent work for miscible systems (Jha et al., PRL 2011, 2013) and immiscible systems (Cueto-Felgueroso and Juanes, PRL 2012, JFM 2014), here we propose a phase-field model for fluid-fluid displacements in a porous medium, when the two fluids have limited (but nonzero) solubility in one another. In our model, partial miscibility is characterized through the design of the thermodynamic free energy of the two-fluid system. We express the model in dimensionless form and elucidate the key dimensionless groups that control the behavior of the system. We present high-resolution numerical simulations of the model applied to the viscous fingering problem. On one hand, we demonstrate the effect of partial miscibility on the hydrodynamic instability. On the other, we elucidate the role of the degree of fingering on the rate of mutual fluid dissolution. Figure caption: final snapshots in simulations of viscous fingering with a two-fluid system mimicking that of CO2 and water. The colormap corresponds to the concentration of CO2. A band of less viscous gas phase rich in CO2 (red) displaces through the more viscous liquid phase that is undersaturated with CO2 (blue). At the fluid interface, an exchange of CO2 occurs as a result of local chemical potentials that drives the system towards thermodynamic equilibrium. This results in a shrinkage of gas phase as well as a local increase in
Shallow Water Tuned Liquid Dampers
DEFF Research Database (Denmark)
Krabbenhøft, Jørgen
The use of sloshing liquid as a passive means of suppressing the rolling motion of ships was proposed already in the late 19th century. Some hundred years later the use of liquid sloshing devices, often termed Tuned Liquid Dampers (TLD), began to find use in the civil engineering community...... that for realistic roughness parameters the bottom friction has very limited effect on the liquid sloshing behavior and can be neglected. Herby the postulate is verified. Based on the mathematical model three dimensionless parameters are derived showing that the response of the damper depends solely on ratio...
Heat transfer for elastico-viscous flow between two rotating porous discs
Sharma, P. R.; Verma, P. D.
1983-04-01
The problem of temperature distribution and heat transfer for elastico-viscous fluid flow between two rotating porous disks is studied. The equations of motion and energy are solved by a regular perturbation method for small Reynolds number. The effects of the elasticity of the fluid, suction/injection parameter, rotation parameter, Prandtl number and Eckert number on Nusselt numbers at the two disks have been discussed numerically and compared with Newtonian fluid case.
Velocity-vorticity formulation of three-dimensional, steady, viscous, incompressible flows
Energy Technology Data Exchange (ETDEWEB)
Meir, A.J. [Auburn Univ., AL (United States)
1994-12-31
In this work we discuss some aspects of the velocity-vorticity formulation of three-dimensional, steady, viscous, incompressible flows. We describe reasonable boundary conditions that should be imposed on the vorticity and a compatibility condition that the vorticity must satisfy. This formulation may give rise to efficient numerical algorithms for approximating solutions of the Stokes problem, which in turn yields an iterative method for approximating solutions of the Navier-Stokes equations.
Generation of Bianchi Type V Bulk Viscous Cosmological Models with Time Dependent $\\Lambda$-Term
Pradhan,Anirudh; Jotania, Kanti; Rai, Anju
2006-01-01
Bianchi type V bulk viscous fluid cosmological models are investigated with dynamic cosmological term $\\Lambda(t)$. Using a generation technique (Camci {\\it et al.}, 2001), it is shown that the Einstein's field equations are solvable for any arbitrary cosmic scale function. Solutions for particular forms of cosmic scale functions are also obtained. The cosmological constant is found to be decreasing function of time, which is supported by results from recent type Ia supernovae observations. S...
An investigation of the transonic viscous drag coefficient for axi-symmetric bodies
Fan, Yue Sang
1995-01-01
Viscous drag in the transonic regime over an axi-symmetric body with a unique aft contour surface is investigated. The forebody is composed of an arbitrary ellipsoid. The unique aft contour surface has been obtained by an exact solution of the small perturbation transonic equation, using guidelines and tools developed at the Naval Postgraduate School. This unique contour allows the delay of shock formation in the aft portion, hence delaying the onset of wave drag which results in a reduction ...
Stokes’ and Lamb's viscous drag laws
Eames, I.; Klettner, C. A.
2017-03-01
Since Galileo used his pulse to measure the time period of a swinging chandelier in the 17th century, pendulums have fascinated scientists. It was not until Stokes' (1851 Camb. Phil. Soc. 9 8-106) (whose interest was spurred by the pendulur time pieces of the mid 19th century) treatise on viscous flow that a theoretical framework for the drag on a sphere at low Reynolds number was laid down. Stokes' famous drag law has been used to determine two fundamental physical constants—the charge on an electron and Avogadro's constant—and has been used in theories which have won three Nobel prizes. Considering its illustrious history it is then not surprising that the flow past a sphere and its two-dimensional analog, the flow past a cylinder, form the starting point of teaching flow past a rigid body in undergraduate level fluid mechanics courses. Usually starting with the two-dimensional potential flow past a cylinder, students progress to the three-dimensional potential flow past a sphere. However, when the viscous flow past rigid bodies is taught, the three-dimensional example of a sphere is first introduced, and followed by (but not often), the two-dimensional viscous flow past a cylinder. The reason why viscous flow past a cylinder is generally not taught is because it is usually explained from an asymptotic analysis perspective. In fact, this added mathematical complexity is why the drag on a cylinder was only solved in 1911, 60 years after the drag on a sphere. In this note, we show that the viscous flow past a cylinder can be explained without the need to introduce any asymptotic analysis while still capturing all the physical insight of this classic fluid mechanics problem.
Directory of Open Access Journals (Sweden)
Ramiro Román-Contreras
2010-04-01
Full Text Available Few studies have focused on the palaemonid fauna of the Mexican Caribbean. This study provides a list of shallow water free-living and symbiont shrimps of the family Palaemonidae collected on turtle grass (Thalassia testudinum in Bahía de la Ascensión, Bahía del Espíritu Santo and Mahahual reef lagoon, Quintana Roo, Mexico. Ten species in 8 genera are reported, of which the genus Periclimenes is the most diverse with 3 species. An updated geographic distribution along the western Atlantic and other regions is provided for all the species. The greatest affinity of the palaemonid fauna studied, besides that with the Caribbean province, is with the Brazilian, Argentinian, and Texan zoogeographic provinces. Of the 10 species reported in this paper, 8 represent new local records in the studied area.Los crustáceos de la familia Palaemonidae del Caribe mexicano han sido poco estudiados. En este trabajo se presenta un listado de palemónidos de vida libre y simbiontes recolectados en el pasto marino Thalassia testudiuim de Bahía de la Ascensión, Bahía del Espíritu Santo y la laguna arrecifal de Mahahual, Quintana Roo, México. Se registran 10 especies pertenecientes a 8 géneros, siendo el género Periclimenes el más diverso con 3 especies. Para todas las especies se proporciona su distribución geográfica en la costa del Atlántico americano así como en otras regiones. Además de la provincia Caribeña, los palemónidos recolectados también muestran alta afinidad con otras provincias zoogeográficas como la Brasileña, Argentina y Texana; de las 10 especies registradas en este estudio, 8 representan nuevo registro local en el área estudiada.
Kpeglo, D O; Mantero, J; Darko, E O; Emi-Reynolds, G; Akaho, E H K; Faanu, A; Garcia-Tenorio, R
2015-02-01
Radiometric determinations have been carried out to assess public exposure to radioactivity for communities along the coast of a shallow water offshore oilfield in Ghana (which started their operations recently) in order to establish baseline data using alpha spectrometry after radiochemical separation and non-destructive gamma spectrometry. The average activity concentrations of (234)U, (238)U, (230)Th and (232)Th by alpha-particle spectrometry and of (226)Ra, (228)Ra, (228)Th, (40)K, (210)Pb, (234)Th and (137)Cs by gamma-ray spectrometry were determined in the soil samples. The activity concentrations of (234)U, (238)U, (230)Th and (232)Th were determined in the water samples by alpha-particle spectrometry and of (226)Ra by liquid scintillation counting. The total annual effective dose to the public was estimated from the measured activity concentrations and this was clearly below the International Commission on Radiological Protection (ICRP) reference level of 1 mSv y(-1) for public exposure control. In addition, the estimated values of Raeq, Hex and Hin were all lower than the recommended acceptable values and the mean values of gross alpha and gross beta determinations performed for all the water samples give values that were all below the Ghana Standards Authority and World Health Organization recommended guideline values for drinking water quality. The results obtained show insignificant public exposure to radioactivity. However, this study provides important information for future studies on subsequent evaluations of the possible future environmental contamination due to activities of the oil industry in Ghana. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
Directory of Open Access Journals (Sweden)
Lukas Schuster
Full Text Available Symbioses between ciliate hosts and prokaryote or unicellular eukaryote symbionts are widespread. Here, we report on a novel ciliate species within the genus Zoothamnium Bory de St. Vincent, 1824, isolated from shallow-water sunken wood in the North Adriatic Sea (Mediterranean Sea, proposed as Zoothamnium ignavum sp. nov. We found this ciliate species to be associated with a novel genus of bacteria, here proposed as "Candidatus Navis piranensis" gen. nov., sp. nov. The descriptions of host and symbiont species are based on morphological and ultrastructural studies, the SSU rRNA sequences, and in situ hybridization with symbiont-specific probes. The host is characterized by alternate microzooids on alternate branches arising from a long, common stalk with an adhesive disc. Three different types of zooids are present: microzooids with a bulgy oral side, roundish to ellipsoid macrozooids, and terminal zooids ellipsoid when dividing or bulgy when undividing. The oral ciliature of the microzooids runs 1¼ turns in a clockwise direction around the peristomial disc when viewed from inside the cell and runs into the infundibulum, where it makes another ¾ turn. The ciliature consists of a paroral membrane (haplokinety, three adoral membranelles (polykineties, and one stomatogenic kinety (germinal kinety. One circular row of barren kinetosomes is present aborally (trochal band. Phylogenetic analyses placed Z. ignavum sp. nov. within the clade II of the polyphyletic family Zoothamniidae (Oligohymenophorea. The ectosymbiont was found to occur in two different morphotypes, as rods with pointed ends and coccoid rods. It forms a monophyletic group with two uncultured Gammaproteobacteria within an unclassified group of Gammaproteobacteria, and is only distantly related to the ectosymbiont of the closely related peritrich Z. niveum (Hemprich and Ehrenberg, 1831 Ehrenberg, 1838.
Dynamics of multicomponent vesicles in a viscous fluid
Sohn, Jin Sun; Tseng, Yu-Hau; Li, Shuwang; Voigt, Axel; Lowengrub, John S.
2010-01-01
We develop and investigate numerically a thermodynamically consistent model of two-dimensional multicomponent vesicles in an incompressible viscous fluid. The model is derived using an energy variation approach that accounts for different lipid surface phases, the excess energy (line energy) associated with surface phase domain boundaries, bending energy, spontaneous curvature, local inextensibility and fluid flow via the Stokes equations. The equations are high-order (fourth order) nonlinear and nonlocal due to incompressibil-ity of the fluid and the local inextensibility of the vesicle membrane. To solve the equations numerically, we develop a nonstiff, pseudo-spectral boundary integral method that relies on an analysis of the equations at small scales. The algorithm is closely related to that developed very recently by Veerapaneni et al. [81] for homogeneous vesicles although we use a different and more efficient time stepping algorithm and a reformulation of the inextensibility equation. We present simulations of multicomponent vesicles in an initially quiescent fluid and investigate the effect of varying the average surface concentration of an initially unstable mixture of lipid phases. The phases then redistribute and alter the morphology of the vesicle and its dynamics. When an applied shear is introduced, an initially elliptical vesicle tank-treads and attains a steady shape and surface phase distribution. A sufficiently elongated vesicle tumbles and the presence of different surface phases with different bending stiffnesses and spontaneous curvatures yields a complex evolution of the vesicle morphology as the vesicle bends in regions where the bending stiffness and spontaneous curvature are small. PMID:20808718
DEFF Research Database (Denmark)
Cutanda Henriquez, Vicente; Andersen, Peter Risby; Jensen, Jakob Søndergaard
2016-01-01
In recent years, boundary element method (BEM) and finite element method (FEM) implementations of acoustics in fluids with viscous and thermal losses have been developed. They are based on the linearized Navier–Stokes equations with no flow. In this paper, such models with acoustic losses...