scholarly journals A SEMI-ANALYTIC MODEL OF TIDAL INLETS AND THEIR EVOLUTION

2018 ◽  
pp. 62
Author(s):  
Magnus Larson ◽  
Almir Nunes ◽  
Hitoshi Tanaka ◽  
Hans Hanson
Keyword(s):  
Water Exchange ◽  
Flow Model ◽  
Transport Model ◽  
Analytic Model ◽  
Sectional Area ◽  
Tidal Prism ◽  
Tidal Inlets ◽  
Cross Sectional ◽  
Inlet Velocity ◽  
Sediment Transport Model

The water exchange between the sea and a lagoon or bay through an inlet due to tides is a classical topic that has been investigated in a large number of studies (Keulegan, 1967; O’Brien and Dean, 1972; O’Brien and Clark, 1974; Escoffier, 1977). In this paper, a simple semi-analytic model of the flow induced by tides through an inlet connecting the sea to a lagoon or bay is developed. The model is employed to derive explicit expressions for key parameters associated with inlet flows such as bay water level amplitude, tidal prism, maximum inlet velocity, and mixing (retention) time. Also, the inlet flow model is combined with a sediment transport model to determine the conditions for equilibrium as well as the evolution of the inlet cross-sectional area towards equilibrium or closure.

scholarly journals INLETS/ESTUARIES DISCHARGING INTO SHELTERED WATERS

1980 ◽  
Vol 1 (17) ◽  
pp. 151 ◽  
Author(s):  
H.P. Riedel ◽  
M.R. Gourlay
Keyword(s):  
Maximum Velocity ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Tidal Prism ◽  
The South ◽  
Tidal Inlets ◽  
Littoral Drift ◽  
Cross Sectional ◽  
Tidal Estuaries ◽  
The Mean

Tidal prism - cross sectional area relationships and tidal velocities have been measured for inlet entrances and along the length of the estuary for four creeks entering the sheltered waters on the South East Queensland coast, Australia. It has been found that the inlet entrance tidal prism - cross-sectional area relationship is controlled by the magnitude of littoral drift. The tidal prism - cross-sectional area relationship along the estuary is believed to be common to all tidal estuaries landward of the region where littoral drift has an influence. For tidal inlets on sheltered coasts with tidal prisms of the order of 10 n~, the mean maximum velocity entrance is about 0.3 to 0.4 m/s.

scholarly journals REDUCTION PROCESS OF CROSS-SECTIONAL AREA AT RIVER MOUTH

1986 ◽  
Vol 1 (20) ◽  
pp. 113
Author(s):  
Takuzo Shimizu ◽  
Kosuke Kondo ◽  
Ryoichi Kajima
Keyword(s):  
River Mouth ◽  
Reduction Process ◽  
Field Measurements ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Tidal Prism ◽  
Cross Sectional ◽  
Reduction Processes ◽  
The Cross ◽  
Crosssectional Area

Reduction processes of the cross-sectional area at a river mouth were investigated on the basis of numerical simulations and field measurements, in order to predict the possibility of closing of the mouth of the Samegawa River, Fukushima, Japan. As a result, it was found that the decrease in tidal prism, induced by a reduction of the cross-sectional area, had an important effect on the closing of the river mouth. By considering this effect and estimating the sediment transport rate properly, a practical prediction model was successfully established for simulating the reduction processes of the crosssectional area at the river mouth.

scholarly journals EMPIRICAL RELATIONSHIP BETWEEN INLET CROSS-SECTIONAL AREA AND TIDAL PRISM: A RE-EVALUATION

2011 ◽  
Vol 1 (32) ◽  
pp. 86 ◽  
Author(s):  
Marcel Stive ◽  
Liang Ji ◽  
Ronald L Brouwer ◽  
Co Van de Kreeke ◽  
Roahanka Ranasinghe
Keyword(s):  
Empirical Relationship ◽  
Cross Sectional Area ◽  
Similarity Criteria ◽  
Tidal Range ◽  
Published Data ◽  
Sectional Area ◽  
Tidal Prism ◽  
Q Value ◽  
Cross Sectional ◽  
Theoretical Finding

The well-known empirical relationship between the equilibrium cross-sectional area of tidal inlet entrances (A) and the tidal prism (P), first developed by O’Brien (1931), has been extensively reviewed. Our theoretical investigations indicate that a unique A-P relationship should only be expected for clusters of inlets that are phenomenological similar (i.e. fairly similar hydrodynamic and morphological conditions), and that the exponent q in the A-P relation should be larger than 1. However, relevant published data available to date do not clearly support this theoretical finding. A re-analysis of the available data sets by Stive et al. (2009) indicated that they may not be sufficiently reliable to verify our theoretical finding with regard to q>1 due to the violation of the condition of phenomenological similarity, and possibly also due to violating the initial definitions given by O’Brien (1931) in estimating the tidal prism. The resolution of this issue is important because slightly different values of q result in significantly variable values for the equilibrium cross-sectional area of the tidal entrance. This may have significant implications in determining the true stable equilibrium entrance cross-sectional area. Here we present a re-analysis of the available data with a focus on determining the phenomenological dependencies of the A-P relationship. The available A-P data from the US Pacific, Atlantic and Gulf coasts (Jarrett, 1976 and Powell, 2003) have been re-scrutinized and categorized following the above mentioned phenomenological similarity criteria, viz. similar tidal range, similar sediment size, similar littoral transport and similar hydraulic radius. All together, some 20 different categories were considered and A-P relationships were obtained for each category. Generally, high correlations were found between the stable inlet predicted by each A-P relationship and the corresponding data. However, only in a limited number of categories were they significantly better than the correlations for the complete datasets. Finally, we point out that only in a number of categories the q value associated with the A-P relationship exceeded unity as suggested by the theoretical derivations. In the majority of categories the q value associated with the A-P relationship does not exceed unity. This is truly disappointing, and we have no physical explanation for this and consider this issue unresolved.

scholarly journals Small Scales Dynamics Inferred from Tidal Measurements to Mitigate Daily Floodings in the City of Douala: A Case Study of the Besseke's Flood Drain

2020 ◽  
pp. 45-62
Author(s):  
Besack Felix ◽  
Onguene Raphael ◽  
Ebonji Seth Rodrigue ◽  
Oben Mbeng Lawrence ◽  
Kouandji Bekoumb Joseph Betsaleel ◽  
...  
Keyword(s):  
Brackish Water ◽  
Neap Tide ◽  
Spring Tide ◽  
Field Measurements ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Tidal Prism ◽  
Cross Sectional ◽  
Small Scales

The recently constructed Besseke’s flood drain is always filled with water due to individual or combined effect of the tide, urbanization drainage, underground plumes and precipitations runoffs. This study focused on the analysis of small scales dynamics inferred from short term tidal measurements to mitigate the daily flooding in the Besseke’s flood drain. The methodology used is based on field measurements observation. The sampling of water level was conducted during two (02) different tidal regimes in May 2019. The volume of brackish water moving in and out of the Besseke’s flood drain was calculated using the formula of O’Brien. The results showed that Spring conditions had greater amplitudes than Neap tide conditions. During Spring tides, the tidal prism that passed in the midsection of the Besseke’s flood drain (S4) was 3.5 × 101 m3. This means that only a negligible amount of the incoming brackish water reaches the Besseke’s flood drain, amplifies and causes the daily flooding. The unexpected stronger amplitudes and dynamics observed in S4 could be due to its sub estuary nature. Furthermore, the percentage composition of water in this section, showed that the fraction of brackish water changes from 85.7% during Spring tide to 77.8% in the Neap tide conditions. The overall spatial evolution revealed that, the trend in tidal prism (during Spring conditions) was (S0) > (S2) > (S1) > (S3) > (S4) with corresponding values of 2.1 × 104, 1.3 ×104, 1.0 × 104, 2.5 × 102 and 3.5 × 101 m3 respectively. Finally, Tidal prism and Cross-sectional area showed a perfect correlation (r2 = 0.96). The best fitted Cross-sectional area-Tidal prism relationship was obtained in S3 (Market) during Spring tide condition.

scholarly journals Managing Tidal Inlets

2019 ◽  
Vol 1 (2) ◽  
Author(s):  
Jonathan Akin French
Keyword(s):  
Dynamic Equilibrium ◽  
River Mouth ◽  
Tidal Prism ◽  
Tidal Inlets ◽  
Littoral Drift ◽  
Flow Area ◽  
Cross Sectional ◽  
Storm Flow ◽  
Tidal Flows ◽  
Runoff Events

Sandy inlets are in a dynamic equilibrium between wave-driven littoral drift acting to close them, and tidal flows keeping them open. Their beds are in a continual state of suspension and deposition, so their bathymetry and even location are always in flux. Even so, a nearly linear relationship between an inlet’s cross-sectional flow area and the inshore tidal prism is maintained - except when major wind and/or runoff events act to close or widen an inlet. Inlet location can be stabilized by jetties, but dredging may still be necessary to maintain a navigable channel. Armoring with rock large enough to resist erosion can protect an inlet bed or river mouth from excessive storm flow erosion.  Armoring can also be used as a stratagem to close inlets.

scholarly journals A NUMERICAL MODEL FOR DUNE DYNAMICS

1980 ◽  
Vol 1 (17) ◽  
pp. 95
Author(s):  
J. Sundermann ◽  
H.-J. Vollmers ◽  
W. Puls
Keyword(s):  
Sediment Transport ◽  
Path Length ◽  
Erosion Rate ◽  
Flow Model ◽  
Transport Model ◽  
Shear Velocity ◽  
Mean Flow ◽  
Sediment Transport Model ◽  
The Mean ◽  
Bed Material

A numerical sediment transport model is formulated that serves especially for the simulation of bedform mechanics. The model is based on the idea that sediment transport is determined by the erosion rate and the path length of bed material. Formulas for the erosion rate and the path length are derived from physical considerations and from measurements; they depend mainly on the local values of the shear velocity and the mean flow velocity near the bed. The behaviour of detached sediment is simulated by a Monte Carlo procedure, which is based on the mean flow velocities and the eddy viscosity. All flow properties that are needed for the sediment transport model are computed by a numerical flow model that includes two turbulence equations. Results of the flow model and the sediment transport model are compared with measured data.

Cross Sectional Area Changes due to Plastic Bending of Prismatic Bars

2018 ◽  
Author(s):  
Michael J. Zielinski ◽  
Ismail Soner Cinoglu
Keyword(s):  
Finite Element ◽  
Numerical Model ◽  
Empirical Model ◽  
Manufacturing Process ◽  
Small Strain ◽  
Strain Theory ◽  
Cross Sectional Area ◽  
Analytic Model ◽  
Sectional Area ◽  
Cross Sectional

Given the current trend in manufacturing to decrease part variability, and in order to increase product quality, dimensional tolerances are becoming more exacting. With this in mind, and with the decreased time allotted for components to progress from design to manufacture, it has become more critical that accurate models of the manufacturing process are developed. This paper investigates the changes in cross sectional area when a prismatic bar is plastically deformed into a ring of constant diameter. Through further processing, these rings are transformed into components that function to secure mechanical components, such as bearings, into assemblies. Failure of the ring can cause significant damage, or failure of the assembly. Typical thickness tolerances are on the order of +/−.002” (0.05 mm), but can be as small as +/−.0002” (0.005 mm). Also, a growing trend in manufacturing is for the final ring to have a specified thickness on the inner and outer edge within this tolerance band. The rings are produced in various metallic materials with different mechanical properties by continuously coiling prismatic bars to a specific diameter. An analytic model based on small strain theory was developed for the simple cross sections of rectangular and trapezoidal geometries. This model was then extended to include the effect of a hyperbolic rather than linear stress distribution through this simple section in order to relieve the constraints of small strain theory and adequately model the actual process. An empirical model was developed based on experimental observations. A numerical model was developed using the commercial finite element analysis (FEA) software Abaqus (SIMULIA, Providence, RI) to simulate the manufacturing process. This was compared to the empirical model developed from production parts for validation. Once the finite element model is validated, it could be used to explore the effects of design parameters (initial dimensions of the prismatic bar, material properties etc.) and create efficient designs for manufacturing. The empirical model can then be used in the design process. Additionally, the numerical simulation could be used to model more complex cross sectional areas which cannot be evaluated analytically. There was adequate agreement between the empirical and numerical models to the extent that the numerical model could be used for more complex cross sectional geometries. A further refinement of the analytic model to include finite strain theory should be used to expand on this.

Evaluation of overland flow model for a hillslope using laboratory flume data

2013 ◽  
Vol 68 (5) ◽  
pp. 1188-1194 ◽  
Author(s):  
A. C. C. Arguelles ◽  
M. Jung ◽  
G. Pak ◽  
H. Aksoy ◽  
M. L. Kavvas ◽  
...  
Keyword(s):  
Flow Model ◽  
Overland Flow ◽  
Transport Model ◽  
Experimental Setup ◽  
Data Set ◽  
Sediment Transport Model ◽  
Laboratory Flume ◽  
Physically Based ◽  
Overland Flow Model ◽  
The Given

Comprehensive modelling of overland flow requires models for both rill and interrill area overland flow. Evaluation of a physically based mathematical model for simulating overland flow generated on rill and interrill areas of hillslope was done using a data set gathered from a laboratory experimental setup. A rainfall simulator has been constructed together with a 6.50 m × 1.36 m erosion flume that can be given adjustable slopes in both longitudinal and lateral directions. The model was calibrated and validated using the experimental results from the setup of the flume having 5% lateral and 10% longitudinal slopes where rainfall intensities of 105 and 45 mm/hr were induced with the use of nozzles. Results show that for the given slope combination, the model was capable of simulating the flow coming from the rill and interrill areas for the two different rainfall intensities. It was found that significantly more of the flow occurred in the form of the rill flow. The model studied here can be used for the better prediction of overland flow and can also be used as a building block for an associated erosion and sediment transport model.

scholarly journals Managing Tidal Inlets

2019 ◽  
Vol 1 (2) ◽  
Author(s):  
Jonathan Akin French
Keyword(s):  
Dynamic Equilibrium ◽  
River Mouth ◽  
Tidal Prism ◽  
Tidal Inlets ◽  
Littoral Drift ◽  
Flow Area ◽  
Cross Sectional ◽  
Storm Flow ◽  
Tidal Flows ◽  
Runoff Events

Sandy inlets are in a dynamic equilibrium between wave-driven littoral drift acting to close them, and tidal flows keeping them open. Their beds are in a continual state of suspension and deposition, so their bathymetry and even location are always in flux. Even so, a nearly linear relationship between an inlet’s cross-sectional flow area and the inshore tidal prism is maintained - except when major wind and/or runoff events act to close or widen an inlet. Inlet location can be stabilized by jetties, but dredging may still be necessary to maintain a navigable channel. Armoring with rock large enough to resist erosion can protect an inlet bed or river mouth from excessive storm flow erosion.  Armoring can also be used as a stratagem to close inlets.

Pelvic Canal Narrowing Caused by Triple Pelvic Osteotomy in the Dog

1994 ◽  
Vol 07 (03) ◽  
pp. 110-113 ◽  
Author(s):  
D. L. Holmberg ◽  
M. B. Hurtig ◽  
H. R. Sukhiani
Keyword(s):  
Postoperative Complications ◽  
Pelvic Osteotomy ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Canal Width ◽  
Operative Complications ◽  
Post Operative Complications

SummaryDuring a triple pelvic osteotomy, rotation of the free acetabular segment causes the pubic remnant on the acetabulum to rotate into the pelvic canal. The resulting narrowing may cause complications by impingement on the organs within the pelvic canal. Triple pelvic osteotomies were performed on ten cadaver pelves with pubic remnants equal to 0, 25, and 50% of the hemi-pubic length and angles of acetabular rotation of 20, 30, and 40 degrees. All combinations of pubic remnant lengths and angles of acetabular rotation caused a significant reduction in pelvic canal-width and cross-sectional area, when compared to the inact pelvis. Zero, 25, and 50% pubic remnants result in 15, 35, and 50% reductions in pelvic canal width respectively. Overrotation of the acetabulum should be avoided and the pubic remnant on the acetabular segment should be minimized to reduce postoperative complications due to pelvic canal narrowing.When performing triple pelvic osteotomies, the length of the pubic remnant on the acetabular segment and the angle of acetabular rotation both significantly narrow the pelvic canal. To reduce post-operative complications, due to narrowing of the pelvic canal, overrotation of the acetabulum should be avoided and the length of the pubic remnant should be minimized.

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