Effect of the open sea boundary conditions on storm surge simulations
TL;DR: In this article, the effect of two types of open sea boundary conditions (viz. zero surge condition and the radiation condition) on surge histories in ocean shelf regions with constant depth and linearly varying depth subjected to uniform atmospheric forcing is examined.
About: This article is published in Coastal Engineering.The article was published on 1989-09-01. It has received 4 citations till now. The article focuses on the topics: Surge & Storm surge.
Citations
More filters
TL;DR: In this paper, a numerical parameter study is performed to elucidate the influence of tidal inlets on open coast storm surge hydrographs, and four different inlet-bay configurations are developed based on a statistical analysis of existing tidal inlet along the Florida coast.
24 citations
Journal Article•
TL;DR: In this article, the influence of different off-shore boundary conditions on flow parameters in a rectangular shelf when shelf waters are subjected to uniform wind and idealized cyclone wind forcings was examined.
Abstract: The main purpose of this study is to identify the off-shore boundary conditions which predict physically acceptable features in the time histories of flow parameters in shelf waters under idealized conditions and to use those boundary conditions in simulation of real situations. We examine the influence of different off shore boundary conditions on flow parameters in a rectangular shelf when shelf waters are subjected to uniform wind and idealized cyclone wind forcings. For uniform wind forcing, we show that the conventional forms of Orlanski and the partially clamped conditions which are expressed in terms of the derivatives of η lead to unrealistic shelf response of monotonously increasing surge histories. The clamped condition and a new off-shore boundary condition, which will be referred to as the Heaps-Orlanski condition, when applied along the off-shore boundary are observed to provide better estimates of surges. Since, the clamped and Heaps-Orlanski conditions predict nearly the same surge histories for uniform and stationary cyclonic wind forcings, a simpler clamped condition is recommended in surge simulation studies. The free modes of oscillation on this idealized shelf are also analyzed and they explain some of the features of the numerically simulated surges.
8 citations
TL;DR: In this paper, a coarse-grid model of the west coast of Britain is used to examine the sensitivity of computed storm-surge elevations and currents to a range of open-boundary conditions.
Abstract: A coarse-grid (resolution of order 7 km) model of the west coast of Britain is used to examine the sensitivity of computed storm-surge elevations and currents to a range of open-boundary conditions. The storm-surge period 1 to 26 March 1994 is used for this comparison, as it is a time of significant wind activity. Also current measurements in the North Channel of the Irish Sea together with coastal elevation measurements are available for model validation. Elevations and currents previously computed with a coarse-grid shelf-wide model can also be incorporated into the open-boundary condition to examine the influence of far-field effects. Initial model calculations with no far-field input show the importance of including shelf-wide effects from either the external shelf model, or by using observations from coastal gauges interpolated along the open boundary of the west-coast model. Provided the west-coast model’s open boundary is taken sufficiently far away from the region of interest, in this case the Irish Sea, then either a radiation condition or an elevation-specified condition is appropriate provided far-field effects are taken into account. If these are not included, then neither boundary condition is successful. For the radiation condition it is necessary to include both elevations and currents from a far-field model in order to reproduce the surge. In the case of an elevation-specified boundary condition far-field effects can be incorporated in hindcast calculations by including observed sea-level changes. In a storm-surge prediction calculation the radiation condition with a far-field model is required. Calculations show that computed elevations are spatially more coherent than currents, with flows through the western Irish Sea showing the greatest sensitivity to open-boundary formulation during storm events.
8 citations
01 Jan 2005
TL;DR: In this paper, a numerical parameter study is performed to elucidate the influence of tidal inlets on open coast storm surge hydrographs, and the results indicate that the four inlet-bay configurations do not have a significant impact on the open coast STORM this paper.
Abstract: Abstract Bridge scour modeling requires storm surge hydrographs as open ocean boundary conditions for coastal waters surrounding tidal inlets. These open coast storm surge hydrographs are used to accurately determine both horizontal and vertical circulation patterns, and thus scour, within the inlet and bay for an extreme event. At present, very little information is available on the effect that tidal inlets have on these open coast storm surge hydrographs. Furthermore, current modeling practice enforces a single design hydrograph along the open coast boundary for bridge scour models. This study expands on these concepts and provides a more fundamental understanding on both of these modeling areas. A numerical parameter study is undertaken to elucidate the influence of tidal inlets on open coast storm surge hydrographs. Four different inlet–bay configurations are developed based on a statistical analysis of existing tidal inlets along the Florida coast. The length and depth of the inlet are held constant in each configuration, but the widths are modified to include the following four inlet profiles: 1) average Florida inlet width; 2) 100 m inlet width; 3) 500 m inlet width; and 4) 1000 m inlet width. Results from these domains are compared to a control case that does not include any inlet–bay system in the computational domain. The Advanced Circulation, Two-Dimensional Depth-Integrated (ADCIRC-2DDI) numerical code is used to obtain water surface elevations for all studies performed herein. The code is driven by astronomic tides at the open ocean boundary, and wind velocities and atmospheric pressure profiles over the surface of the computational domains. Model results clearly indicate that the four inlet–bay configurations do not have a significant impact on the open coast storm surge hydrographs. Furthermore, a spatial variance amongst the storm surge hydrographs is recognized for open coast boundary locations extending seaward from the mouth of the inlet. In addition, a storm surge study of Hurricane Ivan in the vicinity of Escambia Bay along the Panhandle of Florida is performed to assess the findings of the numerical parameter study in a real-life scenario. The main conclusions from the numerical parameter study are verified in the Hurricane Ivan study: 1) the Pensacola Pass–Escambia Bay system has a minimal effect on the open coast storm surge hydrographs; and 2) the open coast storm surge hydrographs exhibit spatial dependence along typical open coast boundary locations. The results and conclusions presented herein have implications toward future bridge scour modeling efforts.
5 citations
References
More filters
216 citations
TL;DR: In this article, the authors proposed a method to solve the hydrodynamical equations, taken in linearized form, by first transforming them to eliminate the depth co-ordinate z and then expressing the vertical current structure in terms of a set of eigenfunctions.
Abstract: Summary
The model computes the dynamic response of the Irish Sea to a stationary wind-stress field suddenly applied to the sea surface. The currents at any depth are determined as well as surface elevations, evaluations being made through time at positions on a uniform horizontal grid of mesh 7.5 nautical miles square. This calculation of the three-dimensional current structure marks an advance on earlier numerical sea models which, generally, have solved the vertically-integrated equations of motion and continuity to yield depth-mean flows without reference to the vertical distribution of current.
The method employed solves the hydrodynamical equations, taken in linearized form, by first transforming them to eliminate the depth co-ordinate z. The resulting set of differential equations, involving two horizontal co-ordinates x, y and time t, are then expressed in terms of finite-differences for numerical solution using the familiar initial-value technique of iterating, from one state of motion to the next, across successive time increments δt. Finally, an inverse transformation applied to the computed values restores dependency on the z co-ordinate, expressing the vertical current structure in terms of a set of eigenfunctions (or modes).
The water is assumed to be homogeneous. Also, the coefficient of vertical eddy viscosity which determines the system of internal stresses is regarded as functionally independent of z and t. A slip condition is postulated at the sea bed. Along the open-sea boundaries of the model, elevation and current are related by a radiation condition.
A series of numerical experiments has been carried out with the model to determine the response of the Irish Sea to uniform southerly and westerly wind fields. In each case the surge motion generated has been computed and, after the transient oscillations have been damped down by friction, the steady-state circulation maintained by the wind has been obtained.
60 citations