Air gap and impact load prediction

DNV's new guidelines, OTG13 and OTG 14, put forth new recommendations for the estimation of air gap and horizontal wave impact loads. Here we describe a combined simulation and model test procedure to address the new DNV guidelines and provide input to the air gap analysis and horizontal wave impact loads.

services

Linear diffraction analysis
A first assessment of a floaters air gap can be evaluated using linear diffraction analysis combined with DNV (OTG13) correction factors

Time domain simulations
If air gap exceedance is detected in Phase 1, time domain simulations can be used to combine the coupling between wave frequent and low frequent motions as well as the OTG13 correction factors.

Air gap model tests
If air gap exceedance is confirmed in Phase 2, model tests can be carried out to determine asymmetry factors and/or verify simulation results.

Model tests and/or CFD
Simulations to determine impact loads If air gap exceedance is detected in Phase 2 and/or Phase 3, impact loads on the platform deck need to be determined according to DNV’s OTG14.

shortcrest effect
SHORTCREST EFFECT OF SHORTCRESTEDNESS ON EXTREME WAVE IMPACT

COMMERCIAL AIR GAP MODEL TESTS WITH FIXED STRUCTURES AND FLOATERS

BreaKin JIP 2016-2018
Increased the understanding of the scale effects involved in wave-in-deck model tests and provided a between link wave kinematics and impact loads. www.marin.nl/jips/breakin

ComMotion JIP 2015-2018
Developed fast and efficient CFD method for predicting wave loads on moving and deforming structures in extreme waves. www.marin.nl/jips/commotion

ShorTCresT JIP 2011-2013
Accounted for short crestedness in the design of offshore structures against extreme waves based on a good description of their spectral characteristics, statistics, kinematics, breaking and loading and to deliver a concreted (empirical) design methodology.

CresT JIP 2008-2010
Developed models for realistic extreme waves and a design methodology for the loading and response of floating platforms.