scholarly journals TIDAL RESPONSE OF TWO-LAYER FLOW AT A RIVER MOUTH

1976 ◽  
Vol 1 (15) ◽  
pp. 182 ◽  
Author(s):  
Shizuo Yoshida ◽  
Masakazu Kashiwamura
Keyword(s):  
Fresh Water ◽  
Salt Water ◽  
River Mouth ◽  
Intermittent Flow ◽  
Mean Velocity ◽  
Tidal Period ◽  
Salt Wedge ◽  
Tidal Motion ◽  
Layer Flow ◽  
Theoretical Considerations

This paper describes various features of tidal effects on the behavior of a salt wedge and on the mechanism of mixing between the salt water and the fresh water in the vicinity of a river mouth. The studies have been performed through experiments, field observations and theoretical considerations. The condition upon which the fresh water begins to show an intermittent flow-pattern owing to an increase of the tidal action, and the criterion of a transition of the mixing type from negligible into intense, were obtained, with two dimensionless parameters X and 6. The former parameter X is given by A = A0/U0T0, in which T0 is the tidal period, A0 is the tidal amplitude of the sea level, and U0 is the temporal mean velocity of the fresh water at the river mouth. The latter parameter 9 is the so-called Keulegan number. Besides, it came evident that a tidal motion of the salt wedge couldn't be understood without a consideration of the internal wave inside the mouth, which were induced by the tide, in addition to a direct effect of the tide.

Current Measurements in Knight Inlet, British Columbia

1959 ◽  
Vol 16 (5) ◽  
pp. 635-678 ◽  
Author(s):  
G. L. Pickard ◽  
Keith Rodgers
Keyword(s):  
British Columbia ◽  
Fresh Water ◽  
Salt Water ◽  
Current Profile ◽  
Tidal Period ◽  
Shallow Estuary ◽  
Layer Flow ◽  
Bottom Depth ◽  
Future Work ◽  
Made In

One of the features of the circulation in an estuary is the net outflow in the surface layer of the fresh water discharged into the estuary together with an appreciable volume of salt water entrained. Continuity considerations require that there be an inflow of salt water to compensate for that taken out in the surface. In a shallow estuary, such as Chesapeake Bay, this results in a two-layer flow, out at the surface and in below it.In a deep estuary, the questions arise whether or not it also possesses this simple two-layer flow and what is the depth and extent of the inflow. Measurements have been made in several inlets in the British Columbia coast to obtain information about the circulation in a deep estuary. Preliminary experiments were made in Toba, Bute and Knight Inlets, the series made in Knight Inlet in July 1956 being the most complete. The techniques employed and the results obtained are described and discussed.In a shallow section (75 m), in-and-out (flood-and-ebb) flow occurred in phase from surface to bottom, with a net outflow in the upper half and inflow below this. In the presence of an up-inlet wind, the flow in the surface few metres reversed and became up-inlet, with an increased outflow below it.In a deep section, both oscillatory (tidal period) as well as net currents occurred at all depths from the surface to 300 m (relevant bottom depth was 350 m). In this deeper section, the oscillatory components were not in phase from surface to bottom, and the net flow showed a three- or four-layer pattern, rather than the simple two-layer pattern which has previously been assumed to exist. The wind had a marked direct effect on the upper layers to a depth of about 10 m and possibly deeper.The movement of the ship while at anchor was monitored and found to be considerable. Most of the current observations were corrected for ship motion before analysis.Calculations of the net fresh water transport (in the upper layer) give reasonable values but similar calculations for the deep water show a net transport which is not to be expected. This apparent net transport may be a consequence of assuming that the current profile across the entire inlet is the same as that in the centre where measurements were made. Other possible sources of error are suggested. In addition, several recommendations are made for future work.

scholarly journals ESTUARINE CURRENTS AND TIDAL STREAMS

2011 ◽  
Vol 1 (7) ◽  
pp. 28
Author(s):  
Roderick Agnew
Keyword(s):  
Fresh Water ◽  
River Flow ◽  
Salt Water ◽  
Three Dimensional ◽  
Vertical Plane ◽  
Water Layer ◽  
Wave Theory ◽  
Constant Density ◽  
Salt Wedge ◽  
Tidal Streams

Fresh water spreading out from the mouth of a river as it enters a salt sea may preserve its identity for a considerable distance on the surface if wind-generated waves, longshore currents and tidal streams are capable of producing only weak mixing. Fig. 1 shows the three dimensional shape of a fresh-water tongue overlying more dense salt water, derived by Takano (1954) on the assumption of constant eddy viscosity and constant density in the fresh water layer, below which the density increases according to an assumed law, making an asymptotic approach to the density of salt water. Takano's model is thus a water jet entraining salt from around and below it. Salt or brackish water may penetrate along the deep channels of an estuary in the shape of a wedge complementary to the fresh water tongue, the salt wedge retreating seawards as heavy rainfall increases the river discharge, and advancing in dry weather intervals. Tidal streams cause a regular oscillation of both fresh and braok water in flood and ebb directions but the seasonal movements of the sloping boundary between fresh and salt water may still be important in low-lying delta regions. Strong tidal streams lead to intense mixing, when neither a fresh water tongue nor a salt wedge can be distinguished, but the isohalines (salinity contours) preserve the general wedge pattern - see Figs. 3 to 6. In the upper reaches of an estuary it is possible to study the effect of the tidal motion by treating it as a simple harmonic perturbation of the uni-directional river flow. Even in the middle portion of the estuary where there is reversal of the horizontal motion, one may seek a "quasi steady" solution for the net effect (seaward movement of fresh water) while allowing for the increased turbulence due to the tidal action. At the seaward end of the estuary there is little deviation from the astronomical tidal rhythm, so the problem reduces to simple harmonic oscillations of salt water. Higher harmonics may be introduced as an extension of the simple solution. For a first approximation it is sufficient to consider flow in the longitudinal vertical plane, to assume that the pressure distribution is hydrostatic as in long wave theory, and even to neglect inertia terms when investigating net effects.

scholarly journals NUMERICAL MODEL FOR DENSITY CURRENTS IN ESTUARIES

1976 ◽  
Vol 1 (15) ◽  
pp. 188 ◽  
Author(s):  
Karsten Fischer
Keyword(s):  
Fresh Water ◽  
Numerical Models ◽  
Salt Water ◽  
Water Discharge ◽  
Physical Models ◽  
Stream Velocity ◽  
Density Currents ◽  
Salt Intrusion ◽  
Salt Wedge ◽  
Flow Models

In the estuarine mixing areas of salt water and fresh water the vertical stream velocity profile generally is strongly affected by the baroclinic forces, giving rise to upstream currents near the bottom. Such reverse currents occur not only in stratified estuaries, but also in estuaries of the well-mixed type |1|, and they may cause problems like strong shoaling areas, salt intrusion, or difficulties when disposing wastes or dredged material |3|. The contributions of the salinity variations to the tidal motion are comparable to the contributions from the fresh water upland discharge |1|. For well-mixed estuaries with negligible fresh water discharge, the tidal velocities and water elevations may be obtained from numerical vertically averaged models or from physical homogeneous-flow models, but for all other conditions or desired results one has to use numerical vertically discretized models or physical inhomogeneous-flow models. As numerical and physical models have different properties and deficiencies, they may be used complementarily rather than concurrently |4|, the farfield regime apparently becoming the domain of numerical models. The increased public and scientific interest in water quality problems led to the development and application of baroclinic numerical tidal models |5, 6| . The present paper is concerned with the question, how well the action of baroclinic forces can be represented by numerical techniques. As a test example, the salt wedge problems is tackled. Studies on salt wedges by means of physical models have been very sucessful |1, 7|, but mathematical approches were confined to analytical solutions for the stationary salt wedge |8 - 10| and simple geometric boundaries only. The numerical approach is free from these restrictions, giving a solution of the complete equations of motion, continuity, and convection-diffusion simultaneously.

Study on Salinity Stratification and Distribution in Lingding Yang Estuary

2008 ◽  
Author(s):  
Mingyuan Yang ◽  
Wei Zhang
Keyword(s):  
Fresh Water ◽  
Salt Water ◽  
Flood Tide ◽  
Tidal Range ◽  
Observation Data ◽  
The South ◽  
Wet Season ◽  
Mean Velocity ◽  
Temporal And Spatial Distribution ◽  
The North

Ling Ding Yang (LDY) estuary is one of the main parts of the whole Zhujiang estuary, which lies in the south sea, China. It is about 60km wide from Hong Kong in the east to Macao in the west and the water areas are approximately 2110 km2. The mixing process of salt water and fresh water in the estuary is influenced by many factors, such as the estuarine geometry, tidal range and ravine flows, etc. In this paper, based on the data from the tidal gauge stations and synchronously surveyed data during July 2003, a study on the temporal and spatial distribution characteristics of salinity was made. According to the observation data, in wet season, the fresh water and salt water mixes with the N parameter between 0.21 and 1.63. The distribution of salinity concentration in the east part of LDY is due to coriolis’ force. The salinity concentration decreases from the sea to the estuary, and there exists apparent division point, Nei Lingding Island. To the south of Nei Lingding Island, it is almost partially mixed, and to the north of Nei Lingding Island, it belongs to highly stratification. At the same time, the stratification parameter and the vertical mean velocity in wet season are compared. The N parameter changes with the velocity of tide flow in a tidal cycle. The value of N in a flood tide is usually larger than that is in an ebb tide. That is to say, the mix intensity is much bigger in the flood tide.

scholarly journals Optimization of the Energy Output of Osmotic Power Plants

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Florian Dinger ◽  
Tobias Tröndle ◽  
Ulrich Platt
Keyword(s):  
Fresh Water ◽  
Power Plants ◽  
Salt Water ◽  
Electricity Consumption ◽  
River Mouth ◽  
Energy Output ◽  
Limiting Factor ◽  
Operational Parameter ◽  
New Approach ◽  
Fresh Water Supply

On the way to a completely renewable energy supply, additional alternatives to hydroelectric, wind, and solar power have to be investigated. Osmotic power is such an alternative with a theoretical global annual potential of up to 14400 TWh (70% of the global electricity consumption of 2008) per year. It utilizes the phenomenon that upon the mixing of fresh water and oceanic salt water (e.g., at a river mouth), around 2.88 MJ of energy per 1 m3of fresh water is released. Here, we describe a new approach to derive operational parameter settings for osmotic power plants using a pressure exchanger for optimal performance, either with respect to maximum generated power or maximum extracted energy. Up to now, only power optimization is discussed in the literature, but when considering the fresh water supply as a limiting factor, the energy optimization appears as the challenging task.

EXPERIMENTAL INVESTIGATION OF FLOW RESPONSE TO STATIONARY DISTURBANCE IN ROTATING-DISK FLOW

2019 ◽  
Vol XVI (2) ◽  
pp. 13-22
Author(s):  
Muhammad Ehtisham Siddiqui
Keyword(s):  
Boundary Layer ◽  
Boundary Layer Flow ◽  
Three Dimensional ◽  
Rotating Disk ◽  
Careful Analysis ◽  
Laboratory Frame ◽  
Transition To Turbulence ◽  
Turbulent Regime ◽  
Mean Velocity ◽  
Layer Flow

Three-dimensional boundary-layer flow is well known for its abrupt and sharp transition from laminar to turbulent regime. The presented study is a first attempt to achieve the target of delaying the natural transition to turbulence. The behaviour of two different shaped and sized stationary disturbances (in the laboratory frame) on the rotating-disk boundary layer flow is investigated. These disturbances are placed at dimensionless radial location (Rf = 340) which lies within the convectively unstable zone over a rotating-disk. Mean velocity profiles were measured using constant-temperature hot-wire anemometry. By careful analysis of experimental data, the instability of these disturbance wakes and its estimated orientation within the boundary-layer were investigated.

scholarly journals XII. An easy method to distill fresh water from salt water at sea; by Capt. Newland

1772 ◽  
Vol 62 ◽  
pp. 90-92 ◽  
Keyword(s):  
Fresh Water ◽  
Salt Water ◽  
Easy Method

The materials necessary for this process are the following; a copper or iron pot of 15 or 20 gallons, an empty cask, some sheet lead, a small jar, a few wood-ashes or soap, and billet-wood for fewel.

scholarly journals Three-Dimensional Numerical Simulation of Salinity Intrusion and Instability Condition of Salt Wedge Considering Tidal Motion

1997 ◽  
Vol 41 ◽  
pp. 509-514
Author(s):  
Hitoshi IKENAGA ◽  
Tadashi YAMADA ◽  
Kunihide UCHIJIMA ◽  
Masahiro KASAI ◽  
Kimihito MUKOUYAMA ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Three Dimensional ◽  
Salinity Intrusion ◽  
Instability Condition ◽  
Salt Wedge ◽  
Tidal Motion

scholarly journals WATER EXCHANGE IN THE ESTUARY OF THE RAZDOLNAYA RIVER (AMUR BAY, JAPAN SEA) IN THE ICE COVERED PERIOD

2019 ◽  
Vol 196 ◽  
pp. 123-137 ◽  
Author(s):  
P. Yu. Semkin ◽  
P. Ya. Tishchenko ◽  
V. B. Lobanov ◽  
Yu. A. Barabanshchikov ◽  
T. A. Mikhailik ◽  
...  
Keyword(s):  
Water Exchange ◽  
Salt Water ◽  
Groundwater Discharge ◽  
River Mouth ◽  
Japan Sea ◽  
Bottom Layer ◽  
Additional Source ◽  
Flow Through ◽  
Limited Water Exchange ◽  
Annual Discharge

Environmental conditions in the Razdolnaya/Suifen Estuary and adjacent marine area were monitored from 2008 to 2018, by seasons, including winter observations in January 2014 and January 2018. The river discharge in winter was low: 6 m3 /s (mean annual discharge is 73 m3 /s). The estuary was covered by ice. The cline of salt water at the bottom was traced upstream up to 28 km from the river mouth. The currents in the estuary changed in tidal cycle. Increasing of salinity and temperature (> 2о ) at the bottom was observed in the distance 20–24 km from the river bar (this area was distinguished by relatively thin ice, 20 cm, against 40–70 cm in the rest of estuary). Modeling of the water balance in the estuary showed an additional source of salt water in the internal estuary, beyond the direct exchange with the sea over the river bar, that was presumably the water flow through the aquifer. This groundwater discharge was responsible for supporting of the salted bottom layer and for temperature and salinity increasing in the internal estuary during the ebb phase in conditions of limited water exchange by two-layered estuarine circulation because of ice cover at the river mouth.

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