News
MAUV ON A MISSION
The mAUV (modular Autonomous Underwater Vehicle) was on a mission in the Seakeeping and Manoeuvring Basin. First video shows mAUV inspecting a sea mine. Its manoeuvers around the mine are a demonstration of the six Degrees of Freedom control capabilities of the vessel.Second video shows mAUV performing a ‘lawn mower’ pattern, commonly used in survey […]
THE NETHERLANDS HAS A WORLD FIRST WITH FIRST OFFSHORE SOLAR FARMSYSTEM
Oceans of Energy announces that it has installed the first floaters of the world’s first solar farm system on the North Sea, off the Dutch coast. The offshore solar farm system was installed at the end of November and has since successfully generated energy and withstood the first storms. At MARIN, the system was successfully […]
Events
Publications
2017 

Yvette Klinkenberg René Bosman, Jie Dang ; Ligtelijn, Do Advanced measurements of rimdriven tunnel thrusters The Wageningen TTseries JIP Conference The 5th international conference on advanced model measurements technology (AMT '17) 11/13102017, 2017. @conference{Klinkenberg2017, title = {Advanced measurements of rimdriven tunnel thrusters The Wageningen TTseries JIP}, author = {Yvette Klinkenberg, René Bosman, Jie Dang and Do Ligtelijn}, url = {http://www.marin.nl/web/Publications/Publicationitems/AdvancedmeasurementsofrimdriventunnelthrustersTheWageningenTTseriesJIP.htm}, year = {2017}, date = {20171011}, booktitle = {The 5th international conference on advanced model measurements technology (AMT '17) 11/13102017}, abstract = {For the Wageningen TTseries JIP a rimdriven tunnel thruster test setup was used to evaluate the cavitation dynamics, underwater radiated noise levels (URN), pressure fluctuations on the inside of the tunnel, loads on the propeller, and dynamic generated side forces on the ship hull. Experiences with this complex test setup are discussed in this paper. As there are too much elements in the setup to be discussed down to the last detail, this paper will point out the general components and will go into detail on noise measurements and the calibration of a 6component frame. The calibration and check loads of one of the 6component frames are presented. An elaborate paragraph on noise measurements discusses the calibration of the hydrophones, determination of the acoustic transfer of the setup and signal quality. The analysis of the noise measurements showed disturbances in signals recorded by 2 out of 3 hydrophones. Although not yet completely pinpointed, these disturbances are ascribed to unwanted electromagnetic current, inadequate grounding or engine control switches. Other issues present during measurements were warming of bearings, Bernoulli effects between static and rotating segments of the setup, and calcification and creep of sensors after long time submergence of the setup. In the near future extra effort will be put in to tackle these challenges. Nevertheless, this complex setup with inhouse developed, as well as off the shelf sensors answers to the demanding research questions asked in the TT JIP.}, keywords = {}, pubstate = {published}, tppubtype = {conference} } For the Wageningen TTseries JIP a rimdriven tunnel thruster test setup was used to evaluate the cavitation dynamics, underwater radiated noise levels (URN), pressure fluctuations on the inside of the tunnel, loads on the propeller, and dynamic generated side forces on the ship hull. Experiences with this complex test setup are discussed in this paper. As there are too much elements in the setup to be discussed down to the last detail, this paper will point out the general components and will go into detail on noise measurements and the calibration of a 6component frame. The calibration and check loads of one of the 6component frames are presented. An elaborate paragraph on noise measurements discusses the calibration of the hydrophones, determination of the acoustic transfer of the setup and signal quality. The analysis of the noise measurements showed disturbances in signals recorded by 2 out of 3 hydrophones. Although not yet completely pinpointed, these disturbances are ascribed to unwanted electromagnetic current, inadequate grounding or engine control switches. Other issues present during measurements were warming of bearings, Bernoulli effects between static and rotating segments of the setup, and calcification and creep of sensors after long time submergence of the setup. In the near future extra effort will be put in to tackle these challenges. Nevertheless, this complex setup with inhouse developed, as well as off the shelf sensors answers to the demanding research questions asked in the TT JIP.  
Brouwer, Joris; Tukker, Jan Random uncertainty of variance of finite length measurement signals Conference The 5th international conference on advanced model measurements technology (AMT '17) 11/13102017, 2017. @conference{Brouwer2017, title = {Random uncertainty of variance of finite length measurement signals}, author = {Joris Brouwer and Jan Tukker}, url = {http://www.marin.nl/web/Publications/Publicationitems/Randomuncertaintyofvarianceoffinitelengthmeasurementsignals.htm}, year = {2017}, date = {20171011}, booktitle = {The 5th international conference on advanced model measurements technology (AMT '17) 11/13102017}, abstract = {When considering stationary measurements, the finite length of any practical measurement imposes a random uncertainty component to statistical quantities being researched. In other words, repeating the same experiment will result in a slightly different answer. This happens for example when the limiting factor is facility length (e.g. performing resistance measurements in a towing tank) or when the limiting factor is time (e.g. offshore platform motions in a wave basin). This paper is the fourth in a series of papers considering the analytical derivation and practical estimation of such statistical uncertainties. The previous three papers considered mean values of random processes. This fourth paper considers variance instead and is analogous to the first paper of the series. Both random and periodic process classes are considered. The analytical derivation of the statistical uncertainty of signal variance is given for random, finite bandwidth noise processes and periodic processes. The former is a general solution while the latter is only valid for the trivial case of sinusoid signals. The reason to include periodic solution is its significant deviation from the finite bandwidth solution. The analytical solutions are verified by means of artificially generated signals. In general, the uncertainty of variance for finite bandwidth processes reduce with the square root of the signal length once measurement length exceeds the inverse bandwidth of the process. Measuring too short may result in a standard uncertainty equal to the variance itself. For periodic signals, the uncertainty of variance reduces with signal length itself. Estimating methods to find the statistical uncertainty of signal variance from a single measurement are given for both classes of processes. The analytic solutions and estimating methods are verified with artificially created signals. The presented uncertainty estimators are able to yield reliable and accurate estimates of the 95% confidence intervals.}, keywords = {}, pubstate = {published}, tppubtype = {conference} } When considering stationary measurements, the finite length of any practical measurement imposes a random uncertainty component to statistical quantities being researched. In other words, repeating the same experiment will result in a slightly different answer. This happens for example when the limiting factor is facility length (e.g. performing resistance measurements in a towing tank) or when the limiting factor is time (e.g. offshore platform motions in a wave basin). This paper is the fourth in a series of papers considering the analytical derivation and practical estimation of such statistical uncertainties. The previous three papers considered mean values of random processes. This fourth paper considers variance instead and is analogous to the first paper of the series. Both random and periodic process classes are considered. The analytical derivation of the statistical uncertainty of signal variance is given for random, finite bandwidth noise processes and periodic processes. The former is a general solution while the latter is only valid for the trivial case of sinusoid signals. The reason to include periodic solution is its significant deviation from the finite bandwidth solution. The analytical solutions are verified by means of artificially generated signals. In general, the uncertainty of variance for finite bandwidth processes reduce with the square root of the signal length once measurement length exceeds the inverse bandwidth of the process. Measuring too short may result in a standard uncertainty equal to the variance itself. For periodic signals, the uncertainty of variance reduces with signal length itself. Estimating methods to find the statistical uncertainty of signal variance from a single measurement are given for both classes of processes. The analytic solutions and estimating methods are verified with artificially created signals. The presented uncertainty estimators are able to yield reliable and accurate estimates of the 95% confidence intervals. 