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CIEG-306 Fluid Mechanics Laboratory
2. Stability of a Floating Body
Objective
The objectives of this experiment are:
1. to measure the angle of inclination at which an eccentrically loaded body floats,
2. to observe the circumstances under which a floating body is unstable, and
3. to compare the observed results with theoretical predictions.
Apparatus
The apparatus consists of an open plastic box (‘barge’) which floats in water and carries a mast
(Figure 1). A plumb-bob suspended from the mast provides a means of measuring the angle of inclination of the barge. The vertical position of the center of gravity is controlled by a weight
Wv which may be moved to different heights on the mast. The horizontal position of the center of gravity is controlled by a second weight Wh which may be moved to different horizontal positions on the barge. The following information is necessary: length of barge L= 34.9 cm., width of barge b = 20.3 cm., vertically moving weight Wv = 2.79 N, horizontally moving weight
Wh = 3.11 N, total weight of assembled apparatus W = 13.21 N. For the barge without the weights, the vertical position of the center of gravity, zb, is 5.2 cm. from the outer bottom of the barge. In the following all z distances are measured from the outer bottom of the barge.
Figure 1: A schematic plot of the barge and experimental apparatus
1
Inclination Test
The barge in the inclination test is stable and the purpose is to determine the relationship between load that brings the barge to tilt and the angle of the tilt. The theory behind the inclination test goes as follows. A floating body shall experience net vertical buoyancy force B
(upward) that balance with its weight W (downward), i.e., B=W. The weight of the floating body W acts through its center of gravity (xG, zG) while the buoyancy force B acts through the centriod of the displaced volume (called buoyancy center). When the barge is inclined at an angle , the balance of moments
2. Stability of a Floating Body
Objective
The objectives of this experiment are:
1. to measure the angle of inclination at which an eccentrically loaded body floats,
2. to observe the circumstances under which a floating body is unstable, and
3. to compare the observed results with theoretical predictions.
Apparatus
The apparatus consists of an open plastic box (‘barge’) which floats in water and carries a mast
(Figure 1). A plumb-bob suspended from the mast provides a means of measuring the angle of inclination of the barge. The vertical position of the center of gravity is controlled by a weight
Wv which may be moved to different heights on the mast. The horizontal position of the center of gravity is controlled by a second weight Wh which may be moved to different horizontal positions on the barge. The following information is necessary: length of barge L= 34.9 cm., width of barge b = 20.3 cm., vertically moving weight Wv = 2.79 N, horizontally moving weight
Wh = 3.11 N, total weight of assembled apparatus W = 13.21 N. For the barge without the weights, the vertical position of the center of gravity, zb, is 5.2 cm. from the outer bottom of the barge. In the following all z distances are measured from the outer bottom of the barge.
Figure 1: A schematic plot of the barge and experimental apparatus
1
Inclination Test
The barge in the inclination test is stable and the purpose is to determine the relationship between load that brings the barge to tilt and the angle of the tilt. The theory behind the inclination test goes as follows. A floating body shall experience net vertical buoyancy force B
(upward) that balance with its weight W (downward), i.e., B=W. The weight of the floating body W acts through its center of gravity (xG, zG) while the buoyancy force B acts through the centriod of the displaced volume (called buoyancy center). When the barge is inclined at an angle , the balance of moments