intro story Coast / Estuary

Coast / Estuary

Coastal systems are among the most dynamic physical systems on earth and are subject to a large variety of forces. The morphodynamic changes occurring to coastlines worldwide are of great interest and importance. These changes occur as a result of the erosion of sediments, its subsequent transport as bed load or suspended load, and eventual deposition. 
 
Estuaries are partly enclosed water bodies that have an open connection to the coast. Estuaries generally have one or more branching channels, intertidal mudflats and/or salt marshes. Intertidal areas are of high ecological importance and trap sediments (sands, silts, clays and organic matter).
Within the Delft3D modelling package a large variation of coastal and estuarine physical and chemical processes can be simulated. These include waves, tidal propagation, wind- or wave-induced water level setup, flow induced by salinity or temperature gradients, sand and mud transport, water quality and changing bathymetry (morphology). Delft3D can also be used operationally e.g. storm, surge and algal bloom forecasting. 
 
On this discussion page you can post questions, research discussions or just share your experience about modelling coastal and/or estuarine systems with Delft3D FM. 
 

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Sub groups
D-Flow Flexible Mesh
DELWAQ
Cohesive sediments & muddy systems

 

 

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Specifying temperature at outflow discharges

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Todd DeMunda, modified 5 Years ago.

Specifying temperature at outflow discharges

Hi all, we have been using Delft3D to simulate temperature in a small reservoir in the US. The reservoir is proposed to serve as the heat sink/source for an HVAC unit, and environmental regulators want to know how the thermal structure of the reservoir will be affected. In this situation, heat is added during the summer and extracted during the winter from a flat plate heat exchanger. As far as we can tell there is no way to simply add or subtract heat from a model cell. We have had to treat it like a power plant, with water withdrawn and returned to a nearby location at a raised temperature. Not ideal, but it seems to work.

One situation we have encountered is that in withdrawing water (using a discharge with a negative flow rate, the model requires us to specify the temperature of the water we are taking out (Section 4.5.8 of the FLOW manual). This seems counter-intuitive, as temperature of water removed should be what has been calculated in the model up to that time. It is not clear what happens if the model temperature is different from the value the user is required to specify. We have adapted to this situation by selecting temperatures that we estimate to be close to the model simulated temperature, but that can’t be exact. We would appreciate insight into why this specification requirement exists and what can be done to deal with it.

The second question has to do with getting heat into the model. Since there is no provision for simply discharging (or removing) heat, it must be carried by a flow. The model places a temperature limit of 60 degrees C which requires a substantial artificial flow to convey a specified amount of heat. This artificial flow can induce errors in the simulation. To minimize these errors the flow should be small. Can the temperature limit on the discharge be raised (altering the source code, maybe?) to allow the artificial flow to made small? If the temperature limit were raised to say 10,000 degrees C, the flow needed to convey the heat could be made small.

Thanks for your help!
Adri Mourits, modified 5 Years ago.

RE: Specifying temperature at outflow discharges (Answer)

Yoda Posts: 1221 Join Date: 1/3/11 Recent Posts
Hi Todd,

There are two ways to add heat to the system:
1. Add water, via a discharge, with a high temperature. Just as you are trying.
2. Via heat exchange with the air at the top layer. This is probably not an option for your situation.

Currently, it is not implemented to just add heat to the system.

I assume you refer to section "4.5.9.1 Discharge". The limit of 60 degrees is a physically safe upper boundary. It is not a hard coded boundary. You are free to use higher temperatures in your model. I tried with 100 000 degrees Celsius and it ran fine.

Regards,

Adri