Control of salinity in an estuary by a transition

2021 ◽  
Vol 79 (2) ◽  
pp. 91-98
Author(s):  
Henry Stommel ◽  
Harlow G. Farmer
Keyword(s):  
Salt Water ◽  
Control Action ◽  
Theoretical Reason ◽  
Flume Experiments ◽  
Stratified Estuary

A theoretical reason is developed to explain why the mouth of a vertically stratified estuary should act as a constraint on the amount of salt water available for mixing in the estuary. Flume experiments designed to test this idea are described. The effect of tides on the control action and application to various estuaries is discussed.

Dynamical Characteristics and Salt Transportation of Lingdingyang Bay of Pearl River Estuary in Summer, Guangdong Province, China

2011 ◽  
Vol 347-353 ◽  
pp. 1926-1929
Author(s):  
He Wei ◽  
He Qin Chen ◽  
Hua Li You ◽  
Long Hua Gao
Keyword(s):  
Salt Water ◽  
Three Dimensional ◽  
River Estuary ◽  
Pearl River Estuary ◽  
Velocity Shear ◽  
Pearl River ◽  
Dynamical Characteristics ◽  
Salinity Gradients ◽  
Salinity Transport ◽  
Stratified Estuary

Abstract. In order to comprehend the salinity transport mechanism,the tidally varying circulation,and salt stratification are investigated in Lingdingyang bay.The conclusions are:When the discharge is moderate,Lingdingyang is a highly stratified estuary,and salt wedge movement is very prominent.The baroclinic circulation is comparatively strong,and strong salinity gradients create a complex three-dimensional flow.A tidal intrusion front moves upstream in flood periods,and distance of movement is longest in flood slack.Because Velocity shear across the interface of fresh and salt water,and intense waves from and break,entrainment is very strong which cause salt water into freshwater.

scholarly journals DETERMINATION OF THE INTERFACIAL EDDY DIFFUSION COEFFICIENT OF A HIGHLY STRATIFIED ESTUARY

1976 ◽  
Vol 1 (15) ◽  
pp. 180
Author(s):  
Yu-Hwa Wang
Keyword(s):  
Sea Water ◽  
Salt Water ◽  
Water Layer ◽  
Eddy Diffusion ◽  
Shear Stresses ◽  
Eddy Diffusion Coefficient ◽  
Layer Flow ◽  
Stratified Estuary ◽  
Number Of Publications ◽  
Stratified Estuaries

Estuaries may be sequentially classified into highly stratified, moderately mixed and vertically homogeneous. An important difference between moderately stratified or vertically homogeneous estuaries, and highly stratified estuaries (salt wedges) is that, in the former, tidal currents are sufficient to cause turbulent mixing of fresh water and sea water over the full depth of the estuary. In the latter, a distinct interface or interfacial layer exists which separates the two nearly homogeneous layers. The vertical advectlon of salt in this two-layer flow is the dominant process in maintaining the salt balance. This paper presents an analytical model describing this process. Experiments have been conducted in the laboratory to compare with the developed theory. A large number of publications concerning estuarine dynamics are available for moderately mixed and vertically homogeneous estuaries. Relatively little information, however, is available for highly stratified estuaries. In an earlier work Keulegan (1949) defined the critical velocity of the upper layer at which the entrainment of the salt water layer starts. A summary of Keulegan's work may be found in Chappter 11 of the book, "Estuary and Coastline Hydrodynamics" edited by Ippen (1966). Recently Partheniades et. al. (1975) reviewed Schijf-Schonfeld's analytical work and Keulegan's experimental data with regard to the length, shape and shear stresses of a saline wedge. Wang (1975) compared his laboratory measurements of interfacial stresses with Lock's Theory.

Bulk drag coefficient of a subaquatic vegetation subjected to irregular waves: Influence of Reynolds and Keulegan-Carpenter numbers

2020 ◽  
pp. 34-42
Author(s):  
Thibault Chastel ◽  
Kevin Botten ◽  
Nathalie Durand ◽  
Nicole Goutal
Keyword(s):  
Drag Coefficient ◽  
Wave Height ◽  
Wave Attenuation ◽  
Empirical Relationship ◽  
Breaking Waves ◽  
Irregular Waves ◽  
Geometrical Parameters ◽  
Flume Experiments ◽  
Seagrass Meadows ◽  
Artificial Vegetation

Seagrass meadows are essential for protection of coastal erosion by damping wave and stabilizing the seabed. Seagrass are considered as a source of water resistance which modifies strongly the wave dynamics. As a part of EDF R & D seagrass restoration project in the Berre lagoon, we quantify the wave attenuation due to artificial vegetation distributed in a flume. Experiments have been conducted at Saint-Venant Hydraulics Laboratory wave flume (Chatou, France). We measure the wave damping with 13 resistive waves gauges along a distance L = 22.5 m for the “low” density and L = 12.15 m for the “high” density of vegetation mimics. A JONSWAP spectrum is used for the generation of irregular waves with significant wave height Hs ranging from 0.10 to 0.23 m and peak period Tp ranging from 1 to 3 s. Artificial vegetation is a model of Posidonia oceanica seagrass species represented by slightly flexible polypropylene shoots with 8 artificial leaves of 0.28 and 0.16 m height. Different hydrodynamics conditions (Hs, Tp, water depth hw) and geometrical parameters (submergence ratio α, shoot density N) have been tested to see their influence on wave attenuation. For a high submergence ratio (typically 0.7), the wave attenuation can reach 67% of the incident wave height whereas for a low submergence ratio (< 0.2) the wave attenuation is negligible. From each experiment, a bulk drag coefficient has been extracted following the energy dissipation model for irregular non-breaking waves developed by Mendez and Losada (2004). This model, based on the assumption that the energy loss over the species meadow is essentially due to the drag force, takes into account both wave and vegetation parameter. Finally, we found an empirical relationship for Cd depending on 2 dimensionless parameters: the Reynolds and Keulegan-Carpenter numbers. These relationships are compared with other similar studies.

Investigational Studies on Quantity of Salinity in Netravati River Estuary Sand-Coastal Karnataka

2018 ◽  
Vol 6 (6) ◽  
pp. 46
Author(s):  
Raveesha P ◽  
K. E. Prakash ◽  
B. T. Suresh Babu
Keyword(s):  
Brackish Water ◽  
Sea Water ◽  
Salt Water ◽  
Construction Material ◽  
Salt Content ◽  
River Estuary ◽  
Sand Sample ◽  
River Sand ◽  
Natural Aggregates

The salt water mixes with fresh water and forms brackish water. The brackish water contains some quantity of salt, but not equal to sea water. Salinity determines the geographic distribution of the number of marshes found in estuary. Hence salinity is a very important environmental factor in estuary system. Sand is one major natural aggregate, required in construction industry mainly for the manufacture of concrete. The availability of good river sand is reduced due to salinity. The quality of sand available from estuarine regions is adversely affected due to this reason. It is the responsibility of engineers to check the quality of sand and its strength parameters before using it for any construction purpose. Presence of salt content in natural aggregates or manufactured aggregates is the cause for corrosion in steel. In this study the amount of salinity present in estuary sand was determined. Three different methods were used to determine the salinity in different seasonal variations. The sand sample collected nearer to the sea was found to be high in salinity in all methods.  It can be concluded that care should be taken before we use estuary sand as a construction material due to the presence of salinity.

Assessing flood risk and detecting changes of salt water inflow in a coastal micro-tidal brackish marsh using GIS

2008 ◽  
Vol 37 (3) ◽  
Author(s):  
Jacek Urbański ◽  
Agata Ślimak
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Flood Risk ◽  
Salt Water ◽  
Brackish Marsh ◽  
Distance Functions ◽  
Water Inflow ◽  
Small Range ◽  
Natural Environments ◽  
Baltic Coast

Assessing flood risk and detecting changes of salt water inflow in a coastal micro-tidal brackish marsh using GISIn order to assess changes in salt water inflow and potential flood risks due to sea level rise in a micro-tidal Beka brackish marsh on the Polish Baltic Coast GIS was used. Such wetlands are important elements of coastal zone natural environments. Creating a geodatabase within a GIS system makes it possible to carry out broad analyses of complex systems, such as coastal wetlands. The results indicate that a 40 cm sea-level rise would considerably increase the frequency of flooding in the investigated area, in part because of the small range of the annual sea level oscillations there. A map of the index of changes in saltwater inflow, created with the help of cost-weighted distance (functions), shows that changes which have occurred along the shore, consisting of filling in the drainage channel outlets, have likely had a significant impact on the vegetation of the area.

Optimized control over modes of hydraulic percussion cutting heads of mining machines

2020 ◽  
pp. 95-104
Author(s):  
Yu. M. Smirnov ◽  
B. M. Kenzhin ◽  
N. S. Smakova ◽  
M. A. Zhurunova
Keyword(s):  
Time Derivative ◽  
Operating Conditions ◽  
Control Action ◽  
Main Function ◽  
Output Data ◽  
Working Cycle ◽  
Control Units ◽  
Action Change ◽  
Function Element ◽  
Service Factors

The main cause of the disagreement between the actual and calculated output data of hydraulic percussion mining machines is the erroneous feed of manipulation signals by the control units. For the maximal fitting of the calculated and actual figures, the continuous method of control action using the third time derivative of the law of motion of the main function element is accepted, namely, the accuracy. The mathematical models of control using displacement, velocity and acceleration are developed. The service factors of mining machines are found. Based on the theory of control and the mathematical logic theory, the logical circuits of formation of manipulation signals in each phase of the working cycle are developed. The main elements are converters, integrators and accumulators ensuring decomposition of elements of the logical circuits and further generation of appropriate control action. It is found that the simplest way is to generate the control action for acceleration of the key function element. For the developed circuits, it is recommended to use general charts of the control action change, implementable for a certain design of hydraulic percussion cutting heads in certain operating conditions.

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