Buoyancy

Learning Objectives

1) To learn how to determine the buoyancy force acting on a submerged object.

2) To learn how to do an engineering estimate of this quantity.

Buoyancy – an upward force exerted by a liquid, gas or other fluid that opposes the weight of an immersed object.

B liq DispF ρ g V

Disp

ρ = density of displaced liquidg = standard gravityv = displaced volume

Equilibrium Equation

y B

B liq Disp

F = 0 = F - W

W = F = ρ g V

W

FB

94

FLUID STATICS Learning Objectives

1). To evaluate the hydrostatic pressure loading acting on a body that is immersed in a liquid. 2). To determine the resultant of a given line, pressure, or

body load on a submerged body and to evaluate the reaction acting on the body that carries such a load.

3). To do an engineering estimate of the equivalent loading.

Assumptions 1). The liquid is incompressible, (i.e., = constant). 2). The hydrostatic pressure loading always acts normal to

any submerged surface, regardless of orientation. 3). The hydrostatic (gage) pressure at a point in a liquid is

proportional to the depth “h” below the free surface.

Hydrostatic Pressure Distribution p = hydrostatic (gage) pressure (pgage = pabs – patm)

= density of the liquid g = acceleration of gravity h = height below the free surface of the liquid

p = ρgh