Stability of a Floating Body
INTRODUCTION
Laboratory experiment 5 is an exercise in hydrostatic. It is designed to demonstrate the stability of a floating cylinder and to familiarize the student with the concept of buoyancy, metacenter and metacentric height. It is also an experimental verification of the theory presented in the textbook.
The center of the buoyancy of a floating body depends on the shape of the body and on the position in which it is floating. If the body is disturbed by a small angle of heel, the center of buoyancy changes because the shape of the submerged volume is changed. The point of intersection of the lines of action of the buoyancy force before and after heel is called the metacenter (M) and the distance between the center of gravity (G) and M is called the metacentric height (GM).
For stability the metacentric height GM must be positive. Stability (restoring force) increases with increasing GM.
PURPOSE
OBJECTIVE
The objectives of this experiment are:
1. To determine how the floating characteristics of a pontoon changes as it is loaded with weight and tilts.
2. To determine the metacentric height of the pontoon by measurement and calculation.
EQUIPMENT
The unit shown in Fig. 1 consists of a pontoon (1) and a water tank as float vessel. The rectangular pontoon is fitted with a vertical sliding weight (2) which permits adjustment of the height of the centre of gravity and a horizontal sliding weight (3) that generates a defined tilting moment. The sliding weights can be fixed in any positions using knurled screws. The positions (4, 5) of the sliding weights and the draught (6) of the pontoon can be measured using the scales. A heel indicator (7) is also available for measuring the heel angle.
THEORY
Floating bodies are a special case; only a portion of the body is submerged, with the remainder poking of the free surface. The buoyancy, , which is the weight of the displaced water, i.e., submerged body portion, is equal to its dead weight, . The
Laboratory experiment 5 is an exercise in hydrostatic. It is designed to demonstrate the stability of a floating cylinder and to familiarize the student with the concept of buoyancy, metacenter and metacentric height. It is also an experimental verification of the theory presented in the textbook.
The center of the buoyancy of a floating body depends on the shape of the body and on the position in which it is floating. If the body is disturbed by a small angle of heel, the center of buoyancy changes because the shape of the submerged volume is changed. The point of intersection of the lines of action of the buoyancy force before and after heel is called the metacenter (M) and the distance between the center of gravity (G) and M is called the metacentric height (GM).
For stability the metacentric height GM must be positive. Stability (restoring force) increases with increasing GM.
PURPOSE
OBJECTIVE
The objectives of this experiment are:
1. To determine how the floating characteristics of a pontoon changes as it is loaded with weight and tilts.
2. To determine the metacentric height of the pontoon by measurement and calculation.
EQUIPMENT
The unit shown in Fig. 1 consists of a pontoon (1) and a water tank as float vessel. The rectangular pontoon is fitted with a vertical sliding weight (2) which permits adjustment of the height of the centre of gravity and a horizontal sliding weight (3) that generates a defined tilting moment. The sliding weights can be fixed in any positions using knurled screws. The positions (4, 5) of the sliding weights and the draught (6) of the pontoon can be measured using the scales. A heel indicator (7) is also available for measuring the heel angle.
THEORY
Floating bodies are a special case; only a portion of the body is submerged, with the remainder poking of the free surface. The buoyancy, , which is the weight of the displaced water, i.e., submerged body portion, is equal to its dead weight, . The
References: