Difference between revisions of "CMS-Flow:Diffraction"

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== Wave diffraction ==
 
== Wave diffraction ==
 
The first term on the right side of the governing equation is the wave diffraction term formulated from a parabolic approximation wave theory (Mase 2001). In applications, the diffraction intensity parameter κ values (≥ 0) needs to be calibrated and optimized for structures. The model omits the diffraction effect for κ = 0 and calculates diffraction for κ > 0. Large κ (> 15) should be avoided as it can cause artificial wave energy losses (Mase 2001). In practice, values of κ between 0 (no diffraction) and 4 (strong diffraction) have been determined in comparison to measurements. A default value of κ = 2.5 was used by Mase et al. (2001, 2005a, 2005b) to simulate wave diffraction for both narrow and wide gaps between breakwaters. In CMSWave, the default value of κ assigned by SMS is 4, corresponding to strong diffraction. For wave diffraction at a semi-infinite long breakwater or at a narrow gap, with the opening equal or less than one wavelength, κ = 4 (maximum diffraction allowed in the model) is recommended. For a relatively wider gap, with an opening greater than on wavelength, κ = 3 is recommended. The exact value of κ in an application is dependent on the structure geometry and adjacent bathymetry, and should to be verified with measurements.
 
The first term on the right side of the governing equation is the wave diffraction term formulated from a parabolic approximation wave theory (Mase 2001). In applications, the diffraction intensity parameter κ values (≥ 0) needs to be calibrated and optimized for structures. The model omits the diffraction effect for κ = 0 and calculates diffraction for κ > 0. Large κ (> 15) should be avoided as it can cause artificial wave energy losses (Mase 2001). In practice, values of κ between 0 (no diffraction) and 4 (strong diffraction) have been determined in comparison to measurements. A default value of κ = 2.5 was used by Mase et al. (2001, 2005a, 2005b) to simulate wave diffraction for both narrow and wide gaps between breakwaters. In CMSWave, the default value of κ assigned by SMS is 4, corresponding to strong diffraction. For wave diffraction at a semi-infinite long breakwater or at a narrow gap, with the opening equal or less than one wavelength, κ = 4 (maximum diffraction allowed in the model) is recommended. For a relatively wider gap, with an opening greater than on wavelength, κ = 3 is recommended. The exact value of κ in an application is dependent on the structure geometry and adjacent bathymetry, and should to be verified with measurements.
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[[CMS#Documentation_Portal | Documentation Portal]]

Latest revision as of 22:24, 17 May 2010

Wave diffraction

The first term on the right side of the governing equation is the wave diffraction term formulated from a parabolic approximation wave theory (Mase 2001). In applications, the diffraction intensity parameter κ values (≥ 0) needs to be calibrated and optimized for structures. The model omits the diffraction effect for κ = 0 and calculates diffraction for κ > 0. Large κ (> 15) should be avoided as it can cause artificial wave energy losses (Mase 2001). In practice, values of κ between 0 (no diffraction) and 4 (strong diffraction) have been determined in comparison to measurements. A default value of κ = 2.5 was used by Mase et al. (2001, 2005a, 2005b) to simulate wave diffraction for both narrow and wide gaps between breakwaters. In CMSWave, the default value of κ assigned by SMS is 4, corresponding to strong diffraction. For wave diffraction at a semi-infinite long breakwater or at a narrow gap, with the opening equal or less than one wavelength, κ = 4 (maximum diffraction allowed in the model) is recommended. For a relatively wider gap, with an opening greater than on wavelength, κ = 3 is recommended. The exact value of κ in an application is dependent on the structure geometry and adjacent bathymetry, and should to be verified with measurements.


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