WO2018096558A1

WO2018096558A1 - Bubble diverter bow for bottom sonar transducer equipped oceanographic and research vessels

Info

Publication number: WO2018096558A1
Application number: PCT/IN2017/050548
Authority: WO
Inventors: Vaidyanatha Iyer ANANTHA SUBRAMANIAN; Manickavasagam PALANIAPPAN
Original assignee: INDIAN INSTITUTE OF TECHNOLOGY MADRAS (IIT Madras)
Priority date: 2016-11-24
Filing date: 2017-11-21
Publication date: 2018-05-31

Abstract

Present disclosure relates to a bubble diverter bow in a vessel (ship) for diverting bubbles arising in a path of transducer in vessel. The bubble diverter bow is obtained by redesigning a hull body of the vessel. Plurality of variants are introduced in the hull. The plurality of variants is introduced from each side starting from a bow associated with the hull in a fore-body section of the hull. Each variant of the plurality of variants comprises a predefined cross-section.

Description

"BUBBLE DIVERTER BOW FOR BOTTOM SONAR

TRANSDUCER EQUIPPED OCEANOGRAPHIC AND RESEARCH

VESSELS"

FIELD OF INVENTION

[0001] The embodiments herein generally relate to a bubble diverter bow for bottom sonar transducer equipped oceanographic and research vessels. The present application is based on, and claims priority from an Indian Application Number 201641040170 filed on 24^th November, 2016 the disclosure of which is hereby incorporated by reference herein.

BACKGROUND OF INVENTION

[0002] Ships employed for oceanographic research purposes are fitted with bottom acoustic transducers. The transducer works by projecting a sonar beam into bottom space underwater below the ships for measurement purposes. The measurement quality is affected if there are any bubble streams in the flowing water under the ship in the acoustic window around the transducer. For effective functioning of transducers, the bubbles need to be avoided in the region of the transducer.

[0003] A solution for diverting bubble provides a typical practice of locating an array of acoustic transducers below a keel bottom of the ship as an external appendage. The transducer performs poorly because of bubble interference in the flow. [0004] Conventional design attempts to reduce an interference due to bubbles by modifying an underwater appendage shape to improve diversion of the flow. An external bottom mounted acoustic transducer might be effective, though external mount adds to appendage drag and are also vulnerable to damage.

OBJECT OF INVENTION

[0005] The principal object of the embodiments herein is to provide a bubble diverter bow in a vessel.

[0006] Another object of the embodiment is to provide a re- designing of a hull of a ship by introducing plurality of variants in a bow region of the hull.

[0007] Another object of the embodiments herein is to provide the bubble diverter bow of a ship to divert the bubble entrained streams away from the bottom ship center line.

[0008] Another object of the embodiments herein provides the bubble diverter bow which for reducing bubble sweep down below the region of sonar transducer location by effectively diverting the flow sideways.

SUMMARY

[0009] Accordingly, the disclosure provides a bubble-diverter bow comprising a plurality of variants introduced into a hull of a vessel. Each variant from the plurality of variants comprises pre-defined geometry parameters. The plurality of variants is introduced from each side starting from a bow associated with the hull. The plurality of variants is introduced in a fore-body section of the hull.

[0010] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.

BRIEF DESCRIPTION OF FIGURES

[0011] This invention is illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:

[0012] FIG. 1(a) illustrates a bubble bow diverter in a vessel with plurality of variants, according to an embodiment as disclosed herein;

[0013] FIG. 1(b) illustrates a bubble bow diverter in a vessel with plurality of variants, according to another embodiment as disclosed herein; [0014] FIG. 1(c) illustrates a bubble diverter bow in a vessel with plurality of variants, according to another embodiment as disclosed herein;

[0015] FIG. 2 illustrates a perspective view of a hull with plurality of variants, according to another embodiment as disclosed herein;

[0016] Fig. 3(a) and FIG. 3(b) illustrate different views for variant

A, variant B and variant C with reference to an original hull, according to another embodiment as disclosed herein;

[0017] Fig. 4(a) illustrates a graphical representation of speed versus resistance, according to an embodiment as disclosed herein;

[0018] FIG. 4(b) illustrates a graphical representation of speed versus resistance for variant C, according to an embodiment as disclosed herein;

[0019] FIG. 5 and FIG. 6 illustrate streamline traces, according to an embodiment as disclosed herein;

[0020] FIG. 7 to FIG. 10 illustrate streamline traces for emanating depths of 0.3 m and 1.2 m, according to an embodiment as disclosed herein;

[0021] FIG. 11 illustrates perspective views of streamline traces at the keel bottom for each of the variant A, the variant B and the variant C, according to an embodiment as disclosed herein; [0022] FIG. 12 shows the streamlines generated at 0.3 m below the free surface for the bubble diverter bow for the variant C, according to an embodiment as disclosed herein; and

[0023] Fig. 13 shows Stream-lines generated at 1.2m below free surface as function of different speeds for the bubble diverter bow, according to an embodiment as disclosed herein.

DETAILED DESCRIPTION OF INVENTION

[0024] The embodiments herein and the various features and benefits of design are explained fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. Also, the various embodiments described herein are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments. The term "or" as used herein, refers to a nonexclusive or, unless otherwise indicated. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein can be practiced and to further enable those skilled in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein. [0025] The embodiments herein provide a bubble diverter bow (or a bow for diverting bubbles) for a bottom Sound Navigation and Ranging (SONAR) transducer equipped oceanographic and research vessels (ships). The embodiments herein provide re- shaping a ship hull (body) at a forward region to overcome a bubble sweep down problem in a region of the acoustic window of a transducer. A bow region may be redesigned to control hydrodynamic flow such that bubbles-entrapped water of an upper surface layers is strategically diverted to flow side-ways of the hull or at the bottom side-ways well away from the location of the sonar transducer.

[0026] The disclosure includes re-designing the hull at the forward region instead of modifying an appendage shape. The bubble diverter bow allows the water to divert both the sides. The redesigning of the hull is different from a bulbous bow which is primarily for drag reduction. The bubble diverter bow uses radical approach to achieve a desirable property of effective bubble diversion. Resistance reduction is achieved primarily by avoiding an appendage at the bottom.

[0027] In accordance with an embodiment, referring to FIG. 1(a), FIG. 1(b) and FIG. 1(c), bubble diverter bows in a vessel 100 with different type of plurality of variants 102 introduced in a hull 104 (hull body) is shown. Hereafter, the hull 104 with the different type of variants may be referred as a Variant A, a Variant B and a Variant C as shown in the FIG. 1(a), FIG. 1(b) and FIG. 1(c) respectively. [0028] The plurality of variants 102 are introduced into the hull 104 of the vessel 100. Each variant of the plurality of variants 102 comprise predefined geometry parameters. The predefined geometry parameters comprise a length parameter, a cross-sectional area parameter, and a volume parameter. The variant A, the variant B and the variant C differs in terms of the predefined geometry parameters to illustrate an effect of change of the predefined geometry parameter over the bubble diversion. The vessel 100 may include a bottom SONAR transducer equipped oceanographic and research vehicle.

[0029] In the FIG. 1(a), FIG. 1(b) and FIG. 1(c), the plurality of variants 102 i.e. the variant A, the variant B and the variant C comprises the predefined geometry parameters defined by a different predefined length, sectional areas and a volume of displacement influencing at least one of a drag of a streamline and a diversion of the streamline. One or more parameters associated with the vessel 100 for modifying the hull 104 are given in Table 1 below.

6 Operational speed 10-11 knots

7 Displacement 3791m^j

8 Water line length 77.7m

9 Wetted surface area 1529 m²

Table 1

[0030] The plurality of variants 102 is introduced for modifying an under- water hull 104 from each side starting from a bow associated with the hull 104 to achieve the bubble diverter bow. The plurality of variants 102 is introduced in a fore-body section of the hull 104 of the vessel 100. The plurality of variants 102 may be represented through the length parameter, the area parameter and the volume parameter (also referred as three parameters) for defining geometry of the bubble diverter bow as shown in FIG. 1(a), FIG. 1(b) and the FIG. 1(c).

[0031] The plurality of variants 102 comprises the predefined geometry parameters defining the length parameter variation at each side of the hull 104, the cross-sectional area parameter variation at a predefined section at a forward direction, a wetted surface parameter of the bubble diverter bow, and a volume parameter variation of the bubble diverter bow. The length parameter variation, the cross-sectional area parameter variation and the volume parameter variation are called the diverter length parameter (Diverter length/LBP), diverter cross-section parameter (Maximum area of cross section at the diverter bow/midship section area of vessel) and diverter volume parameter (bubble diverter shape volume/ Hull volume displacement).

[0032] Table 2 below provides details on three parameters for variant A, variant B and variant C.

Table 2

[0033] FIG. 2 illustrates a perspective view of the hull 104 obtained after introducing the plurality of variants 102. FIG. 3(a) and FIG. 3(b) shows different views of the variant A, the variant B and the variant C with reference to an original hull.

[0034] As shown in FIG. 1(a), FIG.l (b), FIG. 1(c) and FIG. 2, in order to divert bubbles, a U-shape section at the bow of the hull 104 may be modified by introducing the plurality of variants 102 (also referred as section shapes). The plurality of variants 102 comprises an accentuated U- shape with a controlled inflection along under-water beam. The accentuated U-shape comprises a flattened section shape.

[0035] The plurality of variants 102 is introduced by keeping a wetted surface of the hull 104 and total volume of displacement of the hull 104 to a constant. The three parameters are not entirely independent of each other but are used to describe the modification in the hull 104 after introducing the plurality of variants 102.

[0036] The plurality of variants 102 are introduced to transform a bulbous bow of the vessel 100 into a bulb-less bow. A resistance is obtained in a range of 37 N to 68 N at a speed of the vessel in a range of 9 knots to 12 knots. FIG. 4 (a) illustrates a graphical representation of resistance versus speed of the vessel 100. FIG. 4(b) illustrates resistance comparison for variant C.

[0037] Table 3 below provides a different value of resistance obtained after introducing the plurality of variants 102 in the hull 104 at different speeds.

Table 3 [0038] In an embodiment, streamline is also affected due to the modification in the hull 104 after introducing the plurality of variants 102. Streamline traces visualize a flow path of bubble-mixed water flow at different depths below a surface emanating from around the bow of the hull 104. In an example, a highest bubble density within a 1.2 m depth from the surface at a speed of 13.5 knots is considered. Streamline traces are shown in Figs 5 and FIG. 6.

[0039] FIG. 7 to FIG. 10 illustrates streamline trace for two different emanating depths of 0.3 m and 1.2 m. For depth levels at the start of the streamlines (0.3 m and 1.2 m) and for the variant A, the variant B and the variant C considered, the streamline traces are at more than 50% of the half breadth away from a bottom keel center-line at the location of the sonar transducer. The streamline traces stay away even at 50% of the Length variation parameter (LBP) from the forward perpendicular.

[0040] FIG. 11 illustrates perspective views of streamline traces at the keel bottom for each of the variant A, the variant B and the variant C.

[0041] In an embodiment, FIG. 12 shows the streamlines generated at 0.3 m below the free surface for the bubble diverter bow for the variant C. For all speed ranges the effectiveness of the Bubble Diverter Bow is seen as the flows are completely outwards and therefore the bubbles are effectively diverted avoiding sweep-down. [0042] As seen in FIG. 7 to FIG. 10 and FIG. 12, a region right up to a mid-ship region is a favorable location for sensor array installation. Similarly, streamlines generated at 1.2 m below the free surface, move along the hull well outwards at a distance of 55 to 70% of half breadth for all speed ranges. Depth- wise at all speeds the streamlines reach the bottom at a delayed length i.e. at 37% of LBP from FP. It may be further seen that the critical streamlines are completely away from the ship centerline, and therefore the sonar transducer may be mounted at or near the mid-ship, utilizing minimal pitch related motion without speed restriction.

[0043] Fig. 13 shows Stream-lines as function of different speeds for the bubble diverter bow. Traces originating at 1.2 m below surface all are safely diverted.

[0044] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

[0045] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

Claims

STATEMENT OF CLAIMS I/We claim:

1. A bubble-diverter bow, comprises: a plurality of variants, introduced into a hull of a vessel, wherein each variant from the plurality of variants comprises predefined geometry parameters; wherein the plurality of variants is introduced from each side starting from a bow associated with the hull, and wherein the plurality of variants is introduced in a fore -body section of the hull.

2. The bubble-diverter bow as claimed in claim 1, wherein the vessel comprises a bottom SONAR transducer equipped oceanographic and research vehicle.

3. The bubble-diverter bow as claimed in claim 1, wherein the plurality of variants is introduced to transform a bulbous bow of the vessel into one with a bulb-less bow.

4. The bubble-diverter bow as claimed in claim 1, wherein the predefined geometry parameters comprise a length parameter variation at each side of the hull, a cross -sectional area parameter variation at a pre-defined forward section, a wetted surface parameter of the bubble diverter bow, and a volume parameter variation of the bubble diverter bow.

5. The bubble-diverter bow as claimed in claim 1, wherein the wetted surface parameter comprises in a range of 0.998 to 1.014, and wherein the length parameter comprises in a range of 0.18 to 0.32, and wherein the area parameter comprises in a range of 0.137 to 0.145, and wherein the displacement parameter comprises in a range of 0.983 to 1.0.

6. The bubble-diverter bow as claimed in claim 1, wherein the plurality of variants comprises an accentuated U- section shape with a controlled inflection at sections below under-water beam, wherein the accentuated U-shape comprises a flattened section shape.

7. The bubble-diverter bow as claimed in claim 1, wherein the plurality of variants is introduced by controlled wetted surface of the hull and total volume of displacement of the hull to a favorable constant.

8. The bubble-diverter bow as claimed in claim 1, comprises a low drag in a range of vessel speed 9 knots to 12 knots.

9. The bubble-diverter bow as claimed in claim 8, wherein a value of resistance for the vessel comprise in a range of 37 N to 68 N for the vessel speed in the range of 9 knots to 12 knots.

10. The bubble-diverter bow as claimed in claim 1, comprises a bubble mitigation at the sonar device region.