DE2023963A1 - Hull for full-form ships - Google Patents

Description

Nippon Kokan Kabushiki Kaisha IUM "1Q7n Tokyo, Japan Ship hull for full-form ships The invention relates to hull shapes for full-form ships.

As is well known, there are currently two types of bow constructions for full-form ships, namely the so-called bubble or Arched bow and the non-arched bow. In any case, the bow can have many different shapes, with the Feed rate of each bow shape has its advantages and disadvantages, which makes it difficult to determine a suitable one Posing hull shape for a new ship.

The Qesamt hull drag of a ship is determined by numerous Factors of different physical causes determined. If the total hull drag of a full-form ship is viscous flow and wave formation resistance is determined or mainly consists of these factors, is the greatest Part of the total resistance is the viscous flow resistance. Theoretical investigations of the viscous flow resistance (viscous resistance) Jedooh nooh haven't progressed so far that they are only a practical, workable theoretical solution when designing the bow of a ship.

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It has been shown that with the existing full-hull forms none of the usual bow shapes, both when the ship is fully loaded and when the ship is loaded with ballast, low or high drag Able to guarantee propulsion performance "

The bow shape, commonly known as the cylinder bow, exhibits the least resistance of the hull when fully loaded when it is is properly constructed to match the main body part; when loaded with ballast, however, this hull shape is well constructed in terms of resistance to the main hull parts underlay an adapted arch, which ensures low resistance when loaded with ballast. However, the resistance and the propulsive power of the bladder or arching bow are very sensitive to changes of the bow draft as a result of changes in cargo or other conditions, so that in extreme cases this bow shape in a Comparison may show the worst results.

The advantages of a cylinder nose are the excellent propulsion performance when fully loaded as well as in the reduced Construction costs that can be attributed to the fact that each double curve at the bow surfaces over very large areas extends.

More precisely, it can be the total drag of a ship's hull be broken down into the following factors depending on the cause of the various resistance components?

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Total resistance ($ 100).

Pressure resistance

Skin rub resistance ($ 70)

Ripple resistance
was standing

Viscosity pressure resistance

LbW

_, stand (25ίί)

Li _r I j>

l
! I!

Friction form resistance f ι

.... J j

Frictional resistance as an equivalent area ($ 55)! ι ι

Residual resistance

T
ι

Viscous Flow Resistance ($ 95)

Total resistance (100 #)

The dashed lines in the diagram above give a useful one Type of classification of the resistance components »The numbers in brackets indicate the quantitative size of each resistance component of a typical full-form ship in the low-speed range, but these numbers are of course different variable according to the size, shape, draft and speed of a certain ship.

The portion of the skin friction resistance expressed as "frictional resistance as equivalent area" relates only to the wetted height of the fuselage, so that only the components of the residual resistance can be viewed as offering a means of reducing the total resistance. In relation to the front half of the fuselage, of all the residual resistance components, the wave formation resistance and the frictional form resistance contribute significantly to the residual resistance. 109813/1039 - ⁴ -

BATH ORIGINAL

Both in theory and by experiment it has been proven that the ripple resistance and the frictional shape resistance largely determined by the approach angle of a main flow line to the water surface, as shown in is explained below.

The well-known Michell's applies to the wave formation resistance Integral formula (coordinate axes see in Fig. 1):

ßr / 2

R _w . Λ (P ² + Q ² ) se = 'θαθ (1) <

^Ji Jo

Tn mean in this formula

R _w = wave formation resistance;

U ■ = forward speed of the ship in relation to the water;

Q) - \ t ¥ exp (K _o z sec. ² _ö ) cos _{(KqX sec} . _{0) dx dz} .

f = water density;
K = acceleration due to gravity and

0 =

This formula (1) immediately shows that the tangent --4 - ^ - - of the angle between the waterline and the forward speed is an important factor in the waveform resistance.

109813/1039 ^{BAD 0RIQlNAL}

A comparable, practically usable theoretical formula for the friction-form resistance has not yet been developed, but the following formula is known to provide the form factor K _2f (see "Form Affects Viscous Resistance of Ships" by Ichiro Tanaka, "Journal of the Society of Naval Architects of Japan ", Volume 113):

^K 2f - ² ^ ^c w " ¹⁾ I o ... (2)

In this formula:

K ₂ f Relbung form resistance / frictional resistance as an equivalent plane;

L length of the ship;

B width of the ship and

C _w water area coefficient (water level area / L χ B).

Formula (2) does not contain a tangent factor as clearly stated as the factor * y of formula (1), but if one takes into account that B / L represents the mean tangent of the angle between the water and the current, and if one also considers the Considering the nature of the factor C, it can be seen that the tangent of the angle between the water line and the main flow line is again decisive.

In addition, according to the theory of the smallest wave resistance (see "Ships of Minimum Wave Making Resistance" by H. Maruo i.a., "Journal of the Sooiety of Naval Architects of Japan", Volume 114) has been theoretically proven that a hull shape with lowest wave formation resistance a cylindrical bow shape

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with finite rounding or dullness of the stem edge deeper water level and with less roundness or dullness with a shallow draft. This fact theoretically justifies the superiority of a cylindrical bow in fully loaded condition. .

The object of the invention is, therefore, without a bubble or buckle body substantially inferior even when loaded with ballast condition to be similar in the first place to provide a hull shape which virtually the advantages of Zylinderbug hull shape ensured.

Based on the above theories and experimental results According to the invention, the considerations were made that the bow in the area of the load waterline was almost cylindrical and pulling a lower part of the bow forward to reduce the dullness of the edge of the stem at this section reduce, with particular attention to the optimal combination of the change in the dullness of the stem edge as a function of the draft and the angle which the waterline of the immediately adjoining hull sections to the forward direction determine.

The term "A & rounding" or used in the following description and in the claim in connection with the stem leading edge "Bluntness" means half the width across the frame of the hull at the point of contact between a line parallel to the keel line lying waterline and a tangent to this waterline, which runs at an angle of 60 ° to the hull center line. FIG. 2 illustrates this definition, the bluntness or rounding being denoted by Y in the cross section shown.

- 7th

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This task is performed on a full-form hull with a Degree of fullness of at least 0.75 and a length of at least 120 m between verticals solved according to the invention in that / the rounding or bluntness Yf of the section the leading edge of the bow in the area of the full-load waterline

B 41 ν 4 ^ B (B »largest trunk width over frame) ² ^ L · ~~ * 5"

amounts to,-; ■; - ■■ - - · ■ -, ·? --.- -.o ^ »., ■. ■ · ■■■ -..-.

2. the section of the stern leading edge at practically the

same stump at least $ 15 of the full-load draft vertically below the full-load waterline, at the stern edge enough, '' "- \ ■ ·

under said section of the leading edge, a part of the same protrudes over a distance 1 from this section forwards, where - ~ - ¹ ; v

0.02 L £. 1 ^ - 0.04 L (L m length between

FJr Xr xr trir

Vertical)

• is, and

4. the roundness or bluntness of the leading edge of this

• Part of the protruding section by "more than 1/5 is practically constant before the vertical section and

amounts to.

1 0 9 Ö 1 3/1 0 3

The following is a preferred embodiment of the invention explained in more detail with reference to the drawings. Show it:

Fig. 1 is a diagram to illustrate the used Coordinate system for a ship's hull,

Fig. 2 is a diagram to illustrate the dimensioning of the Dullness or rounding of a hull shape with the features of the invention,

Figure 3 is a side view of the stem portion of a hull shape according to the invention,

Fig. 4 is a diagram for the schematic representation of the Change in the bluntness of the stern section according to FIG. 3 as a function of the draft,

5 shows a diagram for the schematic representation of the results of model tests on a conventional cylinder bow, a vaulted torso bow shape and a Mixture of both bow shapes and

6 shows diagrams for the schematic representation of the results "il and 7 of comparative model tests on the three hull molds according to FIG. 5 and two hull shapes according to the invention, these figures once the loaded with ballast and on the other hand illustrate the fully loaded condition.

The following are those on which the hull shape according to the invention is based Considerations explained in more detail.

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I. The shape of the water level at the bow near the full load water line:

For this it is more beneficial to have a large dullness or rounding off to be provided on the leading edge in order to thereby define the angle of the immediately adjacent to the largest trunk width to shrink the overlying waterline. In this way, the local Solingen will be opposite near the bow end a finer or slimmer shape, but with a deep draft the current becomes larger along the surface of the hull viewed as practically two-dimensional, so that the influence this interference is not great. Hence the downsizing of the angle to the waterline immediately afterwards justified to the stern section.

II. The shape of the water level at the bow near the ballast water line:

For this, other conditions are decisive, which is why it is cheaper 1st, the local disturbances or vortex formations in the vicinity to reduce the leading edge, as the draft becomes smaller the flow of the local disturbances increased and their The area also expands because the flow is more three-dimensional will. The position of the leading edge at the point of the ballast waterline does not affect what is determined according to the usual rules Ship length L ^, so that here to reduce the angle the leading edge of the immediately adjoining waterline can protrude far beyond the front vertical, as is the case for the practical application is permissible, so that a projecting Section is formed which is not bubble-shaped, but rather the shape of a protruding * fin or rib owns. '

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10 9 813/10 3 9

III. Change in the bluntness of the leading edge depending on the draft

This factor applies to the leading edge area between the load and ballast waterline, whereby the reason given by Paktor % lf also applies to the area immediately below the full load waterline. The cylindrical stem section can therefore continue vertically to a certain depth below the full-load waterline. The extent of the vertical section below the full-load waterline should be determined as a function of the depth at which the undesirable influence of the expression exp (K _Q Z see ) becomes small if the advantages of a cylindrical bow are to be maintained when fully loaded. Then the principles of Factor II can be applied to the upper part of the forward extension so that this part becomes less blunt and as a slightly convex edge up to about Tdhe Maximum speed in ballast laden. - ", state generated wave surface. This requires a rapid decrease in the bluntness of the leading edge of the stem in the downward direction, which can be taken into account by appropriate pairing of the lines around the bow."

Tests were carried out on models of a type 23 freighter performed with six different examples of bow shapes. In the comparative tests showed a conventional cylinder bow shape (Hull shape CY) the best propulsion performance in a fully loaded draft state, while a thin or slender one Bubble shape (hull shape B) under draft conditions with ballast the cheapest section.

■■■ '■ - 11 -

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'"" BAD ORIGINAL

For this reason, an attempt was made to keep the bow shape of the hull shape CY close to the full load draft line with the bow of the Combine hull shape B in the vicinity of the ballast draft line in order to determine whether a model ship with this mixed bow shape offers the advantages of both constructions.

Using only the basic ideas listed under I and II, a new type of model ship hull shape CF was designed taking into account clear lines, whereupon resistance tests were carried out in three load states compared to the fiäamm hull shapes CY and B in a flow channel and in a towing tank. The results of this test are shown in FIGS. 5, 6 and 7, which show a "steep" draft (ie a shallow draft), a ballast draft and a full-load draft. In each case the ordinate is the residual resistance. Coefficient Cr and the abscissa the Froude number Fn. With the exception of the state of the test draft, the performance of the new model CF was between the performances of the two trunk shapes and the expected results were not achieved.

For this reason, with the application of the third basic idea III, in addition to the factors I and H, two further base models were made, one of which had a hull shape CFg, in which the radius of curvature R of the leading edge on the full-load waterline was 2 m, like this' , was also the case with the hull shape CY, while the other model had a »hull shape CF, (R ■ 3 m). Both models met the requirements of the invention.

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In the case of the hull shape CF ^ the bluntness was Yf = B / 22 "8, while 1 = 0.027 L and Y, was slightly less than Yf / φ . In the case of the hull shape CF, Y _f = B / 15.2, while 1 = 0.027 L. and Yj _{5 was} slightly less than Y ^, /,.

Both hull forms, GPg and CF, met the following conditions a) Degree of fullness - ^ $ 0.75

b) Length between perpendiculars (L) J>. 120 ms

c) dullness or roundness (as defined above); the leading edge at the full load waterline between B and Bj
¥ 5TB

d) length at the protruding section (l) between a 0, and 0.04L (cf. Pig, 3) S.

e) dullness of the protruding portion dei * um

as 1 protruding leading edge between 0 and " W

(see Fig. 4) j

''" ■■■

f) Dullness extends below the waterline by at least

of the full-load draft (comp. Fig. 3 and%

The graphic representations according to FIG. 6 wtxu. f show * that the hull shapes CFg and CF surpass the trunk-hull colors in both ballast and full-load states »

In the comparison tests carried out with the CF hull shape, the water temperature Wf was different than in the comparison tests on the CF2 and CF * _# hull shapes, but it showed

■ ■. '. - 13 -

1 0 9 8 1 37 1 0 3 9 bad original

2023SS3

in both experiments almost the same hull shape CY; the same coefficient of residual resistance. The respective residual resistance coefficients of the five ship models are therefore given together in FIGS . 6 and J for comparison purposes.

The shape of the fuselage according to the invention thus has the same advantages both a cylindrical bow and a vesicular shape respectively arched bugs and allows, as can be seen from the above An attempted comparison results in a reduction in the through- Hull generated water forest both in a fully loaded position as well as when loaded with ballast.

ORIGINAL BATHROOM

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Claims (1)

Pat e η t a η s ρ r u ο h Full-form hull with a degree of completeness of
at least 0.75 and a length of at least 120 m
between perpendiculars, characterized in that ^ (1) the roundness or bluntness Yf of the portion of the | The leading edge of the stern in the area of the full-load waterline B • ν <£ B '(ß ^β largest trunk width over frame), (2) the section of the stern leading edge at practically the same dullness by at least $ 15 the full-load draft vertically below the full-load wa ^ ariine on the stern leading edge enough, under said section of the leading edge a part of the same over a distance 1 from this section to the front protrudes, where 0.02 L £. 1 fs. 0.04 L _ (L = length between
and verticals) (4) the roundness or bluntness of the leading edge of this
Part of the projecting section is practically constant by more than 1 / j5 before the vertical section and ■ 0 <Y _b £ _ ^Y - amounts to. 1098 13/1039 _BAD ORIGINAL