Experiment on stability and others on Maxsurf program Essay Example

Experiment on stability and others on Maxsurf program

Table of Contents

2Introduction

2Displacement, block and prismatic coefficients change

4Trimming moment

5The trimming angle and forward and aft drafts

7Conclusion

Introduction

The aim of the paper is calculate ship stability. Reliance on the metacentric height as a measure of transverse stability is limited, to situations in which the ship heels to small angles from the upright, typically less than about 10 degrees. When changing the angle of G on the position of the Metacentre will not alter the metacentric height. However, it changes laterally it will change leading to unstable equilibrium. When the vessel is inclined in a certain angle, the centre of buoyancy changes from the centreline as the centre of gravity does not change. This causes rotation of the vessel since the forces of both the buoyancy and gravity are the same but acting in different direction location. This balances both forcesleading to unstable equilibrium.

Displacement, block and prismatic coefficients change

The following shows how the displacement, block and prismatic coefficients change with respect to the draft.

experiment on stability and others on Maxsurf program

The observed changes are sensible as they are consisted with the parameters as expected.

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GZ values plot

Plot GZ values with respect to the heel angle for two tested displacements (135000 and 145000 tonnes). Explain the difference between the two curves.

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The first type of curve the recession curving starts earlier unlike the other curve and some part of this curve will be a constituent of the graph. If individual type two curves are fitted together to form a composite curve, the result is a master recession curve. It represents the base flow contribution, after surface runoff has ceased, at as many different stages as possible

Trimming moment In the barge, when tanks 1 and 8 are partially filled with fresh water (80% and 10% respectively), does it create a positive or negative trimming moment This creates does it create a positive trimming moment positive. Since it is not flooded it will remain stable.

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The angle of trim may be expressed as follows

experiment on stability and others on Maxsurf program  4

experiment on stability and others on Maxsurf program  5

Angle of trim is calculated as

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The trimming angle and forward and aft drafts

When the barge’s tank 1 and 2 are fully flooded with water calculate the trimming angle and forward and aft drafts and compare your results with Maxsurf.

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Change of trim forward = 39.3 cm

Trimming angle =

Displacement t

0

0

0

0

0

0

0

0

0

0

Draft at FP m

Draft at AP m

Draft at LCF m

Trim (+ve by stern) m

0

0

0

0

0

0

0

0

0

0

WL Length m

Beam max extents on WL m

Wetted Area m^2

Waterpl. Area m^2

Prismatic coeff. (Cp)

Block coeff. (Cb)

Max Sect. area coeff. (Cm)

Waterpl. area coeff. (Cwp)

LCB from zero pt. (+ve fwd) m

LCF from zero pt. (+ve fwd) m

Immersion (TPc) tonne/cm

MTc tonne.m

RM at 1deg = GMt.Disp.sin(1) tonne.m

Max deck inclination deg

0

0

0

0

0

0

0

0

0

0

Trim angle (+ve by stern) deg

0

0

0

0

0

0

0

0

0

0

Trimming angle and forward and aft drafts are different from that produced by results with Maxsurf. This may be as results of errors of entry or calculation. The ships’ equilibrium point is not the point at which the forces of buoyancy forces and gravitational are equal. In equilibrium the vessel can tilt and the GZ>0 or GZ<0 is stretched downward a distance d from its centerline length so that the buoyancy causes movement.

Note that the GM depends on inclination angle and g but not on the mass of the vessel. This means that there is stable equilibrium and positive moments when metacentre is above the center of gravity (GZ>0) however when (GZ=0), the vessel will be at neutral equilibrium. Unstable equilibrium will be achieved when (GZ<0) that is center of gravity is above metacentre.

Conclusion

The two methods of calculating Curves of Stability for ships produce different results. However, Maxsurf is more accurate. According to Maxsurf the trim is less than 1% while the excel has some of the figures of more than 1%