Product(s):	SACS
Version(s):	2023
Area:	Seastate & Wave Response

Problem

How can I generate wave loads considering the diffraction according to MacCamy & Fuchs in SACS?

Solution

SACS use Morrison’s equation to generate the wave load, but the Morison's equation is limited to tubulars which diameters is less than one fifth (1/5) of the wave length and it is more conservative approach. We need to use Wave Diffraction Theory if member size is large, which is more than (1/5) x Wave length.

We implemented the MacCamy & Fuchs approach in SACS Seastate and Wave Response. So, if you do a static analysis, you can run the Seastate module and if you do a dynamic analysis, you can use this approach directly with the wave response module.

For Static Analysis:

Use 'D' option in CDM line column 62 if members within 15 degrees of vertical shall have the inertia coefficient modified based on ratio of member diameter to wave length in order to account for diffraction effects per MacCamy and Fuchs.

For Dynamic Analysis:

Use 'D' option in WAVTIM line column 76 to include diffraction calculations.