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. 




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



Message Boards

D3D-WAVE: Relation between 'northdir' parameter and rectilinear grid axes

Anonymous Anonymous, modified 7 Years ago.

D3D-WAVE: Relation between 'northdir' parameter and rectilinear grid axes

The scenario:
A rectilinear computational grid created in a regular cartesian coordinate reference frame (i.e. with x/M axis aligned horizontally increasing from west/left to east/right, and y/N axis aligned vertically increasing from south/bottom to north/top) is rotated about its origin by alpha degrees to align the x/M axis with an effectively straight coastline.

The question:
When specifying the 'northdir' parameter in the .mdw file [e.g. from the Physical_Parameter/Constants window of the GUI] should the parameter be expressed relative to the unrotated z/M axis or the rotated x/M axis?

For example...
If the coastline is aligned south-west to north-east [with the sea to the north-west] the recti-linear computational grid would be rotated by alpha=+45 degrees. Would the 'northdir' parameter then be specified as 45 degrees or would it remain as 90 degrees as it would be specified for the unrotated computational grid?

João Gil, modified 7 Years ago.

RE: D3D-WAVE: Relation between 'northdir' parameter and rectilinear grid ax

Padawan Posts: 29 Join Date: 10/24/12 Recent Posts
Dear Ruairi,

In my point of view, the xy axis stay unrotated, which means their position won't depend on the rotation applied to the grid.
Therefore, after reading your example in the last paragraph, I'd say the 'northdir' remains 90 degrees...

Best regards,
João Gil
Anonymous Anonymous, modified 7 Years ago.

RE: D3D-WAVE: Relation between 'northdir' parameter and rectilinear grid ax (Answer)

Dear João,

Thanks for your thoughts. This is what I believe as well.
Just I've been getting seeing odd results relating to directions and was wondering whether it was something as simple as axis orientation.

I intend to work on this basis [and focus on finding other causes for the problem] unless anyone else suggests this is wrong.