Predicting the oscillating bi-directional exchange flow in the Straits of Mackinac

2013 ◽  
Vol 39 (4) ◽  
pp. 663-671 ◽  
Author(s):  
Eric J. Anderson ◽  
David J. Schwab
Keyword(s):  
Exchange Flow ◽  
Straits Of Mackinac

Rotating Exchange Flow

1997 ◽  
Author(s):  
Daniel R. Ohlsen ◽  
John E. Hart
Keyword(s):  
Exchange Flow

scholarly journals The Effects of Exchange Flow on the Karst Spring Hydrograph under the Different Flow Regimes: A Synthetic Modeling Approach

Water ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1189
Author(s):  
Malihe Shirafkan ◽  
Zargham Mohammadi ◽  
Vianney Sivelle ◽  
David Labat
Keyword(s):  
Flow Regime ◽  
Spring Discharge ◽  
Exchange Flow ◽  
Flow Conditions ◽  
Spring Hydrograph ◽  
Conduit Flow ◽  
Discharge Fluctuations ◽  
Recession Coefficient ◽  
The Matrix ◽  
Synthetic Modeling

In this study, a synthetic modeling approach is proposed to quantify the effect of the amount and direction of the exchange flow on the karstic spring discharge fluctuations under different hydrologic conditions corresponding to high and low flow conditions. We hypothesis that the spring discharge fluctuations constitute a valuable proxy to understand the internal processes of the karst system. An ensemble of spring hydrographs was synthetically produced to highlight the effect of exchange flow by exploring the plausible range of variability of coefficients of exchange flow, conduit diameter, and matrix hydraulic conductivity. Moreover, the change of the rate of point recharge through the karst conduit allows for the quantifying of the sensibility of the spring hydrograph to the directions of exchange flow. We show that increasing the point recharge lies to a remarkable linear recession coefficient (β) as an indication of the conduit flow regime. However, a reduction in and/or lack of the point recharge caused the recession coefficient to change to exponential (α) due to the dominant effect of the matrix restrained flow regime and/or conduit-influenced flow regime. The simulations highlight that the exchange flow process from the conduit to the matrix occurred in a short period and over a restricted part of the conduit flow regime (CFR). Conversely, the exchange flow dumped from the matrix to the conduit occurs as a long-term process. A conceptual model is introduced to compare spring hydrographs’ characteristics (i.e., the peak discharge, the volume of baseflow, and the slope of the recession curve) under the various flow conditions with the directions of the exchange flow between the conduit and the matrix.

Effects of riffle–step restoration on hyporheic zone chemistry in N-rich lowland streams

2006 ◽  
Vol 63 (1) ◽  
pp. 120-133 ◽  
Author(s):  
Tamao Kasahara ◽  
Alan R Hill
Keyword(s):  
Urban Areas ◽  
Hyporheic Zone ◽  
Stream Water ◽  
Ion Concentration ◽  
Hyporheic Exchange ◽  
Ecosystem Functions ◽  
Exchange Flow ◽  
Nutrient Inputs ◽  
Lowland Streams ◽  
Hyporheic Zones

Stream restoration projects that aim to rehabilitate ecosystem health have not considered surface–subsurface linkages, although stream water and groundwater interaction has an important role in sustaining stream ecosystem functions. The present study examined the effect of constructed riffles and a step on hyporheic exchange flow and chemistry in restored reaches of several N-rich agricultural and urban streams in southern Ontario. Hydrometric data collected from a network of piezometers and conservative tracer releases indicated that the constructed riffles and steps were effective in inducing hyporheic exchange. However, despite the use of cobbles and boulders in the riffle construction, high stream dissolved oxygen (DO) concentrations were depleted rapidly with depth into the hyporheic zones. Differences between observed and predicted nitrate concentrations based on conservative ion concentration patterns indicated that these hyporheic zones were also nitrate sinks. Zones of low hydraulic conductivity and the occurrence of interstitial fines in the restored cobble-boulder layers suggest that siltation and clogging of the streambed may reduce the downwelling of oxygen- and nitrate-rich stream water. Increases in streambed DO levels and enhancement of habitat for hyporheic fauna that result from riffle–step construction projects may only be temporary in streams that receive increased sediment and nutrient inputs from urban areas and croplands.

scholarly journals The Tidally Averaged Momentum Balance in a Partially and Periodically Stratified Estuary

2010 ◽  
Vol 40 (11) ◽  
pp. 2418-2434 ◽  
Author(s):  
Mark T. Stacey ◽  
Matthew L. Brennan ◽  
Jon R. Burau ◽  
Stephen G. Monismith
Keyword(s):  
Water Column ◽  
Time Scale ◽  
Eddy Viscosity ◽  
Momentum Equation ◽  
Momentum Balance ◽  
Exchange Flow ◽  
Bed Stress ◽  
Turbulent Momentum ◽  
Stratified Estuary ◽  
Estuarine Exchange

Abstract Observations of turbulent stresses and mean velocities over an entire spring–neap cycle are used to evaluate the dynamics of tidally averaged flows in a partially stratified estuarine channel. In a depth-averaged sense, the net flow in this channel is up estuary due to interaction of tidal forcing with the geometry of the larger basin. The depth-variable tidally averaged flow has the form of an estuarine exchange flow (downstream at the surface, upstream at depth) and varies in response to the neap–spring transition. The weakening of the tidally averaged exchange during the spring tides appears to be a result of decreased stratification on the tidal time scale rather than changes in bed stress. The dynamics of the estuarine exchange flow are defined by a balance between the vertical divergence of the tidally averaged turbulent stress and the tidally averaged pressure gradient in the lower water column. In the upper water column, tidal stresses are important contributors, particularly during the neap tides. The usefulness of an effective eddy viscosity in the tidally averaged momentum equation is explored, and it is seen that the effective eddy viscosity on the subtidal time scale would need to be negative to close the momentum balance. This is due to the dominant contribution of tidally varying turbulent momentum fluxes, which have no specific relation to the subtidal circulation. Using a water column model, the validity of an effective eddy viscosity is explored; for periodically stratified water columns, a negative effective viscosity is required.

Shipwrecks of the Straits of Mackinac

1992 ◽  
Vol 18 (2) ◽  
pp. 46
Author(s):  
Timothy Koerner ◽  
Charles E. Feltner ◽  
Jeri Baron Feltner
Keyword(s):  
Straits Of Mackinac

Unsteady convective exchange flows in cavities

1998 ◽  
Vol 368 ◽  
pp. 127-153 ◽  
Author(s):  
J. J. STURMAN ◽  
G. N. IVEY
Keyword(s):  
Boundary Layer ◽  
Steady State ◽  
Boundary Layer Thickness ◽  
Buoyancy Flux ◽  
Exchange Flow ◽  
Flushing Time ◽  
Exchange Flows ◽  
Buoyancy Forcing ◽  
Convective Exchange ◽  
Approach To Steady State

Horizontal exchange flows driven by spatial variation of buoyancy fluxes through the water surface are found in a variety of geophysical situations. In all examples of such flows the timescale characterizing the variability of the buoyancy fluxes is important and it can vary greatly in magnitude. In this laboratory study we focus on the effects of this unsteadiness of the buoyancy forcing and its influence on the resulting flushing and circulation processes in a cavity. The experiments described all start with destabilizing forcing of the flows, but the buoyancy fluxes are switched to stabilizing forcing at three different times spanning the major timescales characterizing the resulting cavity-scale flows. For destabilizing forcing, these timescales are the flushing time of the region of forcing, and the filling-box timescale, the time for the cavity-scale flow to reach steady state. When the forcing is stabilizing, the major timescale is the time for the fluid in the exchange flow to pass once through the forcing boundary layer. This too is a measure of the time to reach steady state, but it is generally distinct from the filling-box time. When a switch is made from destabilizing to stabilizing buoyancy flux, inertia is important and affects the approach to steady state of the subsequent flow. Velocities of the discharges from the end regions, whether forced in destabilizing or stabilizing ways, scaled as u∼(Bl)1/3 (where B is the forcing buoyancy flux and l is the length of the forcing region) in accordance with Phillips' (1966) results. Discharges with destabilizing and stabilizing forcing were, respectively, Q−∼(Bl)1/3H and Q+∼(Bl)1/3δ (where H is the depth below or above the forcing plate and δ is the boundary layer thickness). Thus Q−/Q+>O(1) provided H>O(δ), as was certainly the case in the experiments reported, demonstrating the overall importance of the flushing processes occurring during periods of cooling or destabilizing forcing.

scholarly journals Impact of evaporation and precipitation on estuarine mixing

2021 ◽  
Author(s):  
Marvin Lorenz ◽  
Knut Klingbeil ◽  
Hans Burchard
Keyword(s):  
River Runoff ◽  
Freshwater Flux ◽  
Exchange Flow ◽  
Surface Salinity ◽  
Estuarine Mixing ◽  
Freshwater Transport ◽  
Freshwater Forcing ◽  
Order Of Magnitude ◽  
Inverse Estuary ◽  
The Persian Gulf

AbstractRecent studies could link the quantities of estuarine exchange flows to the volume-integrated mixing inside an estuary, where mixing is defined as the destruction of salinity variance. The existing mixing relations quantify mixing inside an estuary by the net boundary fluxes of volume, salinity, and salinity variance which are quantified as Knudsen or Total Exchange Flow bulk values. So far, river runoff is the only freshwater flux included and the freshwater exchange due to precipitation and evaporation is neglected. Yet, the latter is the driving force of inverse estuaries, which could not be described by the existing relations. To close this gap, this study considers evaporation and precipitation to complete the existing mixing relations by including cross-surface salinity variance transport. This allows decomposing the mixing into a riverine and a surface transport contribution. The improved relations are tested against idealized two-dimensional numerical simulations of different combinations of freshwater forcing. The mixing diagnosed from the model results agrees exactly with the derived mixing relation. An annual hind-cast simulation of the Persian Gulf is then used to test the mixing relations, both exact and approximated, e.g., long-term averaged, for a realistic inverse estuary. The results show that the annual mean mixing contributions of river discharge and evaporation are almost equal, although the freshwater transport due to evaporation is about one order of magnitude larger than the river runoff.

scholarly journals Using an Isohaline Flux Analysis to Predict the Salt Content in an Unsteady Estuary

2017 ◽  
Vol 47 (11) ◽  
pp. 2811-2828 ◽  
Author(s):  
Matthew D. Rayson ◽  
Edward S. Gross ◽  
Robert D. Hetland ◽  
Oliver B. Fringer
Keyword(s):  
River Flow ◽  
Salt Content ◽  
Box Model ◽  
Flux Analysis ◽  
Galveston Bay ◽  
Exchange Flow ◽  
Salt Intrusion ◽  
Adjustment Time ◽  
The Mean ◽  
Salinity Difference

AbstractAn estuary is classified as unsteady when the salinity adjustment time is longer than the forcing time scale. Predicting salt content or salt intrusion length using scaling arguments based on a steady-state relationship between flow and salinity is inaccurate in these systems. In this study, a time-dependent salinity box model based on an unsteady Knudsen balance is used to demonstrate the effects of river flow, inward total exchange flow (tidal plus steady), and the salinity difference between inflow and outflow on the salt balance. A key component of the box model is a relationship that links the normalized difference between inflowing and outflowing salinity at the mouth and the mean salinity content. The normalized salinity difference is shown to be proportional to the mean salinity squared, based on theoretical arguments from the literature. The box model is validated by hindcasting 5 years of mean salinity in Galveston Bay (estimated from coarse observations) in response to highly variable river discharge. It is shown that this estuary typically has a long adjustment time relative to the forcing time scales, and, therefore, the volume-averaged salinity rarely reaches equilibrium. The box model highlights the reasons why the adjustment time in a large, partially mixed estuary like Galveston Bay is slower when the mean salt content is higher. Furthermore, it elucidates why the salt content in the estuary is more responsive to changes in river flow than in landward exchange flow at the estuary mouth, even though the latter quantity is usually several times larger.

scholarly journals Exchange Flow Variability between Hypersaline Shark Bay and the Ocean

2018 ◽  
Vol 6 (2) ◽  
pp. 65 ◽  
Author(s):  
Yasha Hetzel ◽  
Charitha Pattiaratchi ◽  
Hrvoje Mihanović
Keyword(s):  
Exchange Flow ◽  
Flow Variability ◽  
Shark Bay
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