# D-Flow Flexible Mesh

D-Flow Flexible Mesh (D-Flow FM) is the new software engine for hydrodynamical simulations on unstructured grids in 1D-2D-3D. Together with the familiar curvilinear meshes from Delft3D 4, the unstructured grid can consist of triangles, pentagons (etc.) and 1D channel networks, all in one single mesh. It combines proven technology from the hydrodynamic engines of Delft3D 4 and SOBEK 2 and adds flexible administration, resulting in:

• Easier 1D-2D-3D model coupling, intuitive setup of boundary conditions and meteorological forcings (amongst others).
• More flexible 2D gridding in delta regions, river junctions, harbours, intertidal flats and more.
• High performance by smart use of multicore architectures, and grid computing clusters.
An overview of the current developments can be found here.

The D-Flow FM - team would be delighted if you would participate in discussions on the generation of meshes, the specification of boundary conditions, the running of computations, and all kinds of other relevant topics. Feel free to share your smart questions and/or brilliant solutions!

## Message Boards

### Group Velocity Calculation for Multiple Wave Components

HK

#### Group Velocity Calculation for Multiple Wave Components

Youngling Posts: 1 Join Date: 12/22/17
Hi All,

I am a beginning coastal modeler and I haven't been able to find a general equation for wave group velocity, when more than two components are involved.

It seems that all the equations for group velocity I could find fall into one of the two approaches:

1. By taking the derivative of wave frequency with respect to wave number: i.e., del(omega)/del(k)

2. By multiplying the phase velocity C by a ratio n.

Both approaches, however, assume that the wave group consists of only two individual waves with very similar wave periods.

Is there any general equation available that can be used for any arbitrary number of waves with widely different periods?

Any help will be greatly appreciated. My apologies if this is such a basic question, but it has been bothering me to a great degree..

Thanks.

-Hans