EYE ON DESIGNTechniques open up new possibilitiesImaging MeasurementBY WIM LAFEBERith its staggering ability can be measured using two cameras. The duration of the deformations was Image Correlation. The measured shapes to show displacements Recently, a ? exible composite propel- shorter than 1 millisecond, which meant of the stern wave were compared to the of submillimeter scale ler was tested in the Cavitation Tunnel that the cameras had to acquire images shapes calculated by MARIN’s Parnas-Wto stern waves of several at MARIN. As strain gauges could not at 15,000 frames per second! These mea- sos CFD Software. Digital Image Cor-meters high, the Digital Image Correla- be applied, the Digital Image Correla- surements were combined with data from relation opens up new possibilities for tion technique has been applied on a tion technique was used. A random pat- pressure sensors, strain gauges and high- measurement campaigns that previously wide range of projects at MARIN. Ex- tern was painted on the propeller blades speed videos of the wave impacts. This seemed impossible. MARIN continues amples from research programs in con- so the deformation could be captured by combined dataset provided valuable in- to apply this technique within challeng-trolled conditions and full-scale trials are the cameras. The measured data from sight and a better understanding of wave ing projects.highlighted. the deforming propeller blades under impact loading and the corresponding In some situations conventional sen- various conditions was used to improve structural response of the containment sors cannot be applied. For example, structural models of composite propel- system. For the validation Computation-when the sensors alter the hydro-dynam- lers. al Fluid Dynamics (CFD) software stern The Authorical or structural properties of the object wave measurements were performed on or, when the sensor capabilities are sim- LNG Containment System a +100 m vessel. A ? eld of 25 m behind Wim Lafeber is Researcher Hydro-struc-ply too limited. However, Digital Image Full-scale wave impact tests have been the vessel was covered by two cameras tural Services at the Trials & Monitoring Department of MARIN, the Maritime Re-Correlation can provide a solution. This conducted on an instrumented LNG con- to capture the stern wave at different search Institute Netherlands. is a method where the shape and defor- tainment system panel. Here, a random ship speeds. Here, the natural texture of e: w.lafeber@marin.nlmation of a three-dimensional surface pattern was also painted on the surface. the stern wave was used for the Digital 14 Maritime Reporter & Engineering News • SEPTEMBER 2014MR #9 (10-17).indd 14 MR #9 (10-17).indd 14 9/3/2014 11:10:33 AM9/3/2014 11:10:33 AM