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The LIUTO: a modern, low wave generating, passenger MB for water cities

A. Paciolla Diparthen to Ingegneria Navale 'Federico 11' Naples Universi@, Italy

Abstract

The only means of transport in Venice is constituted by the waterways, which have to sustain the weight of both commercial and passenger traffic. The last one overtakes, during the tourist high season, the limit that seems to be acceptable to preserve the historical buildings staying along the canals banks. For this reason some limits to the wave generation in lagoon navigation have been fixed. This paper presents an argument for the design of LIUTO, a modem vessel generating low wave and velocity fields, and in particular the results of the last study carried out in Venice in March 2000 comparing the wave and velocity field generated by the existing vessel with the one generated by the LIUTO. The diagrams elaborated by the author demonstrate that the LIUTO generates a smaller velocity field and waves with smaller total energy than the existing vessel one.

1 The LIUTO project

LIUTO, acronym for Low Impact Urban Transport water Omnibus, is a project supported by the European Commission (project no BE 95-1782 , DG XI1 - Research and Technological Development, Brite-Euram programme) having as Co-ordinator the ACTV, the public transport company of Venice, and as partners: The INTERMARINE S. p. A. (Italy) constructor of naval vessels in composite materials, the MARIN - Maritime Research Institute Netherlands (Netherlands) naval and maritime research institute, the SHOTTEL-WERFT Josef Becker GmbH & Co. (Germany) constructor of azimuthal propulsion systems, SVA - Shiffbau-Versuchsanstalt Potsdam GmbH (Germany) naval research institute, Dipartimento di Ingegneria Navale (Italy) of the University Federico I1 of

Transactions on the Built Environment vol 52, © 2001 WIT Press, www.witpress.com, ISSN 1743-3509

Naples na\-a1 research institute. The project, started in 1996 and finished in March 2000, had been co-ordinated with the development of a hybrid propulsion system. commissioned by ACTV. The result is a vessel presenting a reduction in wave and wash generation, a better tnanoeuc-rability, a reduction of maintenance costs.

2. The DTN contribution to the LlUTO project

The contribution of Dipartilnento di Ingegneria Navale (in the following : DIN) to this project had concerned the design of a hull cutting down the global resistance and the wave generation and washing effect, the testing of more than one model in its towing tank simulating normal condition and shallow water conditions in order to optimise the final design of the hull, and the design and constniction of innovative sensors useful to measure the wave and the pressure perhirbation due to the hull's and the propeller's action. The DIN organized two campaigns of fill1 scale radiated wave and wash tests, the first in 1997 having as object the existing vessel operating on the route Piazzale Roma - Canal Grande - Piazza San Marco - Lido, the second in March 2000 on both existing and new vessel in order to compare the beha\lour of the two hulls.

3. The wave generation and washing effect reduction

The passenger transport in Venice is mostly based on public services. managed by ACTV. The ACTV's fleet in service on the water lines is constituted by 54 waterbusses or "vaporetti" (Ml'b) and 59 motor crafts (M/s) plus a fenr larger units. The trafic is mainly concentrated in the main canals of the city, in any case in restricted lagoon waters, sometimes very shallow The increasing tourist activity has got as consequence an increase of passenger transport capacity demand (in Gran canal the frequency of ACTV vessel's passing is 5 - 10 minutes) and all this has a dangerous impact on the delicate environmental equilibrium of the lagoon in general and in particular of the catrals on wliose banks there are historical buildings. The prolonged action of varying local pressures and washing on the mortar of submerged exposed walls can cause its progressive erosion that can finally effect the draining of the sand and clay filler used in the building foundations. For this reason ,in recent years, the Venice mayor has prevented the motor craft driver from sailing along one major canal (Rio Novo). The speed in the Venetian lagoon area is for these reasons limited to 10.8 kn in open water in the lagoon, 8.1 kn in the Canale della Giudecca, 5.9 kn in the Grand Canal. More recently had been created the Comrnissione Moto Ondoso (Wave motion Committee in the following CMO) with the aim of studying the genesis, consequences and possible solution of snch undesired and serious phenomenon. The studies of this organization endeavored to find a parameter rather easy to use but meaningful of quantity of energy transformed from vessels in waves, and take


to suggest a limit curve of residual resistance that tnustn't be overcame from the hull operating in Venetian lagoon. The technology and vessels Qpe developed in LIUTO project could be directly transferred to application in other water cities such as Amsterdam, Lisbon etc and generally in urban water transport in areas very crowded such as Holland or Gennany where the erosion of banks and the disturbance and damage to vessels moored alongside is of increasing concern. The reduction of tlie residual resistance, and consequently of the power needed to the propulsion of the vessel, lias helped the design of the hybrid energy system using a propulsion system run by an electric motor powered by battery packs and an inverter. These are charged in turn by a diesel generator that runs at constant speed. The diesel engine can so rnn at its optimum efficiency level, minimising its pollutant emissions, and its vibrations generation and increasing the conlfort of both the passengers and the inhabitants of the t om. The research project related to the propulsion system had been financed by ACTV and developed by ANSALDO SISTEMI INDUSTRIAL1 on tlie basis also of a study carried out by a team in which took part the DIN.

4 The LIUTO hull

The towing tests camed out on the lnodels built by the DIN self have revealed a rneaningfhl reduction of total resistance, and therefore of the effective power. The fig l shons the residual resistance of the LTUTO liull compared with the limit imposed by the CMO.

10 12 14 16 18 20 22

Speed (kmlh) Fig. l : LIUTO res. res. and CM0 limlt

The fig. 2 shows the total resistance coefficient of the LLIUTO hull compared nit11 the esisting vessel's one. You can see that in correspondence of some value of Fronde number the reduction of total resistance coefficient is over 30%, and in any case reaches everywhere the 20%.


0.18 0,2 0,22 0,24 0,26 0,28 0,3 0.32 0 3 4 0,36 0.38 0,4

FROUDE NUMBER Fig. 2 : Total resistance coeff. LIUTO vs. existing

5 The last campaign in Venice

In order to confirm the LIUTO hull behaviour shown in towing tests, fit11 scale radiated wave and wash tests have been carried out in Venice on one of the existing vessels and the LIUTO one. This campaign was based on tests in free water during which have been measured both nave height and velocity of the stream caused by the passage of the vessels at a measured distance from a platform on which had been mounted all the instruments. The table 1 shows the instruments used.

Wave height I Stream velocity I Vessel site & speed 1 Basic stream Capacitive probes I Strain gauge sensors I DGPS I Current meter

Tab. 1 The instrumentation.

The wave height has been measured using capacitive probes logging the level of the water with high resoldion. It is a conventional measurement taken by an instnnnentation whose accuracy and reliability has already been tested inany times at the DIN. The measurement of the stream perturbation gave some problems, due to the smallness of the velocity induced by the passage of the vessels, and to the very hard operational conditions being the water of the lagoon rich in seaweeds and other elements distnrbing the measure. So the DIN had to project innovative sensors to make this measurement. Water velocity has been so measured at two different depth with stream sensors composed of a foil supporting a ball offering a calculated drag; the foil deformation , measured with strain gauges. is proportional to water speed. Fig. 3 shows this kind of sensor. The sensors were set on a support consisting in a pole driven in the bottom of the canal supporting four arms at the two different height of O,94 m and 1,8 m (these


values are read continually and the position of the arms are changed when, by the action of the tide , thej exceed the fixed clearance ) . Each ann supports t\+o

Fig. 3 Velocity sensor

sensors, each one can bend in only one direction, and the two direction are perpendicular, so we have the upper sensor measuring the longitudinal colnponent of the velocity of water (in the following UL sensor), the upper sensor measuring the transversal component ( UT sensor) and likewise the DL sensor and the DT one. The fig. 1 shows this support.

NOT IN SCALE

f j, / I -

t , / FIG. 4 \ elocity sensors support

i

The basic stream velocity has been measured by a current meter. The site and the speed of the vessel have been measured using the Differential Global Position System.


708 Urban Tramport a t d the Etwir-onnzet~t it2 the 21st Cetltuq

6 The data collect during the campaign All the data collect during this ca~npaign have been elaborated and organi~ed in files reporling, relatively to the velocity field, the values of transverse and longitudinal component of the velocity of water in correspondence of upper and down sensors, and relatively to the wave formation the spectrum of the energy of the waves. The runs usefid are these shown in tab. 2

Table 2 : The tests log.

7 The elaboration of the data collect during the campaign

Regarding the log of the tests performed in Venice we particularly want to emphasise : 1). The tests would have to be carried out on three values of speed: about 6 kn, about 9 kn and about 10 kn. Actually, although we have tried to run the boats in very similar conditions, the control of the speed parameter was not exact enough. 2) We can say the same about the minimurn distance which varies from 26.01 m to 43.14 m. 3) Naturally a half of the tests was performed in direction N and the other half in direction S. About the second point we can distinguish the wave measurement and the velocity measurement. We suppose, in the following, that the wave measurenlent is not strongly sensitive to the distance, so we are sure to make a negligible mistake if \W compare the measurement of wave's height without making any correction which takes into account the distance differences. Regarding the velocity measurement we believe that the distance plays an important rule. We have corrected the data related to the velocity field thinking that this parameter was inversely proportional to the square of the distance.


We have considered the vector sum of tlie values measured by tlie transversal sensor and tliat measured by tlie longitudinal one. Proceeding in this nay, n-e were able to compare all the routes independently from the direction N or S. We liave disregarded the fact tliat tlie two sensors were not pliysically in tlie sane point, because we have proposed tlie liypotliesis in which the two sensors are in the same conditions with regard to tlie perturbation front. The fig. 5 shows the velocity of water read by tlie longitudinal upper sensor in correspondence of tlie passage of the LIUTO vessel in one of the tests.

distance (m) Fig. 5 LIUTO velocity of water LU sensor

8 The wave formation

In order to compare tlie wave fonnation of the two hulls, we liave considered the energy spectruni of the wave motion induced by the passage of the motorboats.. In fig. 6 we show the wave patteni read by the capacitive probes during one of tlie passages of tlie LWTO vessel. In fig. 7 we show one of the diagram of the energy spectrum. We collected all tlie data related to tlie ME46 boat and presented they in a diagram lia~ing as abscissa the ship speed. and in ordinate tlie value of tlie specific energy of the wave fonnation. A regression cun'e of the second order crossing the origin point was drann (fig. 8). The same has been done with tlie data of LIUTO (fig 9). hi fig. 10 we can compare the behaviours of tlie two hulls and we can note tliat in the whole field of ship speed the LIUTO hull generates a wave energy spectrum snialler than the Ml36 one. Only at the begiinung of tlie field there is an imersion of tendency. but to better investigate this field of speed it would be necessary to have some energy value related to speed lesser tlian 6 h.


distance (m) Fig. 6 LlUTO wave pattern

~ Pp -- - - -~ - - -. . .

Spec~fic energy = 0,004 m2 --

0 0,s 1 15 2 2,5 3

Fig. 7 LlUTO wave energy Frequency (Hz)

Ship Speed FIG. 8 MB6 Wave Energy Spectrum


Ship speed

FIG. 9 L I N O Wave Energy Spectrum

h 0-03 7

fi 0,025 ~~ - - -- - -- - -

6 7 8 9 l 0 l l 12

Ship Speed

FIG. 10 Wave Energy Spectrum

9 The velocity pattern

We have considered the vector sum of the hardest condition resulting fi.0111 the trausvese upper and longitudinal upper sensors measurement, and corrected them reporting all the data to a conventional distance of 35 111 in the lly~pothesis that they were inversely proportiolial to the distance. We made tlie same with the transverse down and longitudinal down sensors. We have had sonie difficulties percei\ring the values read by tlie upper sensors during the LIUTO route, therefore the values related to these routes do not hake, in our opinion, tlie same reliability of the others. In fig 11 we show the data distribution of the up sensors in the case of ME36 boat;


in fig 12 the data related to the LIUTO boat, in fig 13 we compare these data and the regressio~~ cun es.

Ship speed (kn) FIG. l 1 MB6 U velocity on the sensors

Ship speed (kn) FIG. 12 LIUTO U velocity on sensors

Ship speed FIG. 13 ME6 versus LIUTO velocity on the U sensors


We can note that at low speed the LIUTO seem to generate a velocity field harder than MB6 boat, whereas at higher speeds it seenls to happen the contrary. We confirm, in this regard, our feeling of lesser reliability of the LIUTO data related to the lower speeds. In figg 11, 15 and 16 we show the data read by the sensors in the lower position.

Ship speed (kn)

FIG 14 M66 D velocity on the sensors

111 this case it is not any doubt that the LIUTO liull generates lesser \,alues of velocity.

FIG. 15 LIUTO D velocity on the sensors


Ship speed (kn)

FIG. 16 MB6 versus LIUTO velocity on the D sensors

10 Conclusions

The open \vater full scale tests carried out in Venetian lagoon in March 2000 lia\.e been the last action of the LIUTO project and have demonstrated that the LlUTO generates waves having an energj spectnlni ver) sn~aller tlian the one generated by the traditional vessel. The same can be told with regard to the velocity field. The LIUTO's teclu~ology can be proposed for other water cities suffering from problems of traffic, nave motion pollution, air pollution. The last one can be reduced both by the hybrid propulsion system, and by the reduction of power required for the propulsion reached because of the reduction of llull residual resistance. So it is possible to say that the LIUTO hull represents a significant progress in the field of research regarding the low wave formation hulls.

References

[ l ) F. Balsamo - A. Brighenti - G. Landri - A. Paciolla - F. Quaranta : The propulsion of public transport vessels in coastal and inner waters: data acquisition, elaboration and study of a1ternath.e solutions proc. of lW1' 9-1 , Ronla 1994 121 F. Balsanio - A. Brighenti - G. Landri - A. Paciolla - F. Quaranta : Experimentation and nieasurenlents on the propulsion plant of a water bus in sen-ice on the 'Canal Grande' in Venice proc. qf Polish CIALlC l~~temationnl t70toicil on combu~t io~~ engines, Warsaw 23-24/5/2994 .V01 1 no 1 I994


[3] F. Balsarno - A. Paciolla -F . Quaranta : Un sistelna per la lnisura a bordo dei parainetri caratteristici del fi~nriona~nento dell'apparato motore e della navigazione report cfDipnrtirmvito tJi I~ipeg~ierio .Vmw/e , Napoli May 1994 [3] F. Balsamo - A. Briglienti - G. Landri - A. Paciolla - F. Quaranta : Sisterna ibrido per vaporetti: studio di prefattibilita lstituto .\fotori del CVR (p~lhbl . no 93RR822) Napoli May 1991 151 F. Balsamo - A. Briglienti - G. Landri - A. Paciolla - F. Quaranta : Tlie propulsion of coastal and inland n-ater transportation vessels - working data acquisition and preliminary design of innovative system to reduce polluttant elnissions yroc. c f fhe 21'' ('1,\L-l(7 Interlaken 1993 [6] F. Balsalno - A. Paciolla - F. Quaranta : Monitoraggio ed elaborazione dati di bordo I,'nutonrnziorie n m d e Novelnber 1995 [7] F. Balsalno - A. Paciolla - F. Quaranta : L'acquisizione a bordo dei dati di propulsione e di na~igaTione Ln Tei-rmtecnicn April 1996 [8] F. Balsamo, A. Briglienti,S. Miranda,A. Paciolla. P. Pagan, C. Pensa : Tlie contribution of DTN to LIUTO European Project proc. (If the Irlternotiorid Corigress or1 Alnrine Techrtologv I iIL42f 97 ISTAMBUL 1997 [9] COMUNE di VENEZIA . Assessorato ai Trasporti e Senizi Pubblici . Colnlnissione per lo studio del moto ondoso. "Relazione finale" May 1991 [l01 A. Paciolla, S. Mirando. C. Pensa. LTUTO WP 1.2: Na\d basic design and slnall scale toning resistalice and radiated nave tests LIC'TO intei-iinl report 17' D I X I [;TO. ll'P1.2 September . '97 [l l ] A. Paciolla . G. Boccadamo . LrCTTO sea keeping performance 1,11'7'0 11iter7inl rtJport / l0 DIA\%ICrTOsenkeep Feb. 1999 1121 A. Paciolla F. Balsa~no . F. Quaranta : The calibration of the sensors for the measurement of the water velocity LII7TO irifernnl report /l0 DI.VL1C-TO.c.e/is Feb. 1999 1131 A. Paciolla . F. Balsamo . F. Quaranta Final report on the preliminan fill1 scale tests carried out in Venice in July 1997 LIC7T0 intemd report riO

DINLICTO-IlT42--5-7 .l Feb. 1998

[l31 A. Paciolla, F. Balsatno, F. Quaranta, Final report on tlie fill1 scale tests on the environmental impact of the conventional M/B and the new LIUTO boat LJC'TO inttmnl report Apr. 2000. [IS] A. Paciolla Some considerations about the comparison nit11 the present M/B LII 'TO interrid report June 2000.

Acknowledgments

Tlie author tlianks for tlie collaboration all tlie people working at the DIN im-olved in the LKJTO project: researchers, technicians, and administrative staff. In particular he thanks Mr Pasquale Cioffi for tlie help given in niaterial choosing. building and testing of the velocity sensors and Mr. Andrea Bove for the help given during the dynamic tests on the sensors and during the fill1 scale open water tests.


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