Trans RINA, Vol 153, Part A1, Intl J Maritime Eng, 2011 Jan-Mar DISCUSSION


EXPERIMENTAL AND NUMERICAL STUDY ON PROGRESSIVE FLOODING IN FULL-SCALE


P Ruponen, Napa Ltd, Finland P Kurvinen, Aalto University, Finland I Saisto, VTT, Finland J Harras, Finnish Naval Research Institute, Finland


(Vol 152 Part A4 2010) COMMENT P Corrignan, Bureau Veritas, France


Generally speaking, I think that the paper is of good quality. The work performed is clearly described and is original since I am not aware any other such experiments at full scale. Please find below some more detailed comments and questions to the authors:


 The summary and introduction should explicitly state that the paper concerns flooding in still water condition.


 Section 2.3 Measurements: – It would help to have a scheme presenting the air pipes and the


locations measurements in the air pipes


– "the flow velocity close to the pipe surface was measure...": this is not clear for me; a drawing would probably help


– Could the water height measurement from


pressure measurement be checked with direct water height measurement for some cases?


 Section 3.2(b): the legend of Figure.9 should be below the figure (not in the next column)


 Section 3.3, 4th paragraph: please add the definition of (critical) damping (ratio) x.


 Section 3.4: a drawing showing the coordinate system axes would be helpful


 Section 4.1 1.2.1.


1.2.2. first sentence of second paragraph: Air


overpressure and water level should be put in opposite order.


for me why Figure12 shows a "too flooding" when


end of second paragraph: it is not clear slow


discharge coefficients since the curves show that the water level calculated


using rough estimations of using these


coefficients is larger than the measured one during the first 80s.


1.2.3. end of 4th paragraph: it is indicated


that the stiffeners and brackets lead to a more rapide change of the water level at the sensor location, whereas Figure.12 shows a delay in the measured signal compared to the calculated ones.


©2011: The Royal Institution of Naval Architects of velocity 1.2.4. end of last paragraph: use of velocity


measurements in the air pipe: the fact that the Pitot measured velocity in the centre of the pipe can be accounted for to derive average velocities which could then be compared to calculated velocities. By considering a turbulent flow in the air pipe, the velocity profile can be


represented by UU r R , where n is 0 (1


) n 1/


about 7 for turbulent flow. Then the average velocity is related to the (measured) velocity in the centre of the pipe (U0). Applying this, one founds Average velocity approximately 0.8U0, which seems to correspond to what is presented on Figure.15.


 Section 4.2: first paragraph: "...no notable air


compression was observed...": how would a notable air compression be observed?


 Conclusion: the conclusion concerning the suitability of


the simplified Bernoulli's equation for the


modelling of progressive flooding seems to me a bit to fast, since the validation case here concerns the flooding in still water conditions. For the ship on waves, I would imagine that dynamic effects (e.g. sloshing in


partially flooded compartments,


variations in flooding conditions at the damage opening due to waves/interaction ship-waves), which do not seem to be modelled here, could play a role. It would be interesting that the author elaborate on the applicability of the software to a damaged ship on waves.


P Valanto, Hamburg Ship Model Basin HSVA, Germany


This is an interesting paper on a topic, which is not exactly new. After all, some of the issues in this paper have already been discussed by E. Torricelli around 1643. The authors, however, present measurements, which are not


full scale often found in open


literature and are in principle free of scale effects that may take place with measurements in reduced scale.


The theoretical modeling with the assumption of perfect gas and Bernoulli’s theorem appear from the start as sufficient. The good correlation between the measured results and the simulations in the rather limited heeling range also confirm this.


This good correlation does not come as a surprise. The vessel floats in calm water inside the covered dock. Thus the ship is subject neither to wind nor to wave action. Two important openings are modeled as butterfly valves. Thus the situation is very much under control with quite accurate


previous information of the discharge


coefficients. The only exception to this is perhaps the valve between the side tank and the equipment room. Here the authors obtain discharge coefficient values


A-63


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