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

 

 

Message Boards

Neumann B.C

Moein Doostmohammadi, modified 2 Years ago.

Neumann B.C

Youngling Posts: 7 Join Date: 12/5/18 Recent Posts

Hi everybody,

I'm modelling a simple channel for the beginning of my thesis and i would really appreciate if you help me.

First let me explain my problem. I want to model a monochromatic wave travelling through a channel with arbitrary dimensions but with Water Level B.C at left and Neumann B.C at right of the model domain. I want this simple wave to go out at right boundary somehow unchanged ( i mean water level gradient=0).

I set boundary conditions to the model with "water level- time series" on the left side as a upstream and "neumann" at the right side of the model as Downstream, but the flow at the right boundary with neumann type starts to move back to the model area instead of going out. I tried different kinds of "Forcing Types" like "time series, harmonic"  for neumann at right of the model domain but faced with the same problem. Would you give me some insight about how the "Neumann" B.C works and affects the model?! I myself think that the right boundary kind of generates flow back to the model because it's simulating outer conditions through right boundary to the model but i want it to read the same water elevation one step before the boundary so the wave can cross it undisturbed.

P.S: I've attached my model's files so you can see what i've done.
many thanks for your consultants

Attachments:

Phil Shepperd, modified 2 Years ago.

RE: Neumann B.C

Padawan Posts: 45 Join Date: 12/4/18 Recent Posts

My first thought is that your right boundary should be Riemann rather than Neumann???  Or possibly even a Water Level boundary with the reflection co-efficient defined as appropriate.   Have you tried these options?

Moein Doostmohammadi, modified 2 Years ago.

RE: Neumann B.C

Youngling Posts: 7 Join Date: 12/5/18 Recent Posts

Hi Phil,
Thanks for your advice and time you gave me to reply. I tried to specify water level for both boundaries even though i knew this isn't right to give same boundary conditions for both boundaries. But again it started to give velocities from the outer right part of the domain to the model as it is obvious in QUICKIN for horizontal velocity!