Submerged specific gravity
Encyclopedia
Submerged specific gravity is a dimensionless measure of an object's buoyancy
when immersed in a fluid
. It can be expressed in terms of the equation
where
stands for "submerged specific gravity", 
is the density
of the object, and
is the density of the fluid.
Submerged specific gravity is equal to the specific gravity given by the ratio of the weight of the object to the weight of the fluid) minus one. That is, the object and fluid have the same density when the specific gravity equals one and the submerged specific gravity equals zero. This fact highlights the utility of the usage of submerged specific gravity in probems involving buoyancy and force balances on submerged objects: the object will naturally rise when its submerged specific gravity is negative, and sink when its submerged specific gravity is positive. Because of this characteristic and its dimensionless nature, submerged specific gravity is ubiquitous in equations of sediment transport
.
Buoyancy
In physics, buoyancy is a force exerted by a fluid that opposes an object's weight. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus a column of fluid, or an object submerged in the fluid, experiences greater pressure at the bottom of the...
when immersed in a fluid
Fluid
In physics, a fluid is a substance that continually deforms under an applied shear stress. Fluids are a subset of the phases of matter and include liquids, gases, plasmas and, to some extent, plastic solids....
. It can be expressed in terms of the equation
where
stands for "submerged specific gravity", is the densityDensity
The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...
of the object, and
is the density of the fluid.Submerged specific gravity is equal to the specific gravity given by the ratio of the weight of the object to the weight of the fluid) minus one. That is, the object and fluid have the same density when the specific gravity equals one and the submerged specific gravity equals zero. This fact highlights the utility of the usage of submerged specific gravity in probems involving buoyancy and force balances on submerged objects: the object will naturally rise when its submerged specific gravity is negative, and sink when its submerged specific gravity is positive. Because of this characteristic and its dimensionless nature, submerged specific gravity is ubiquitous in equations of sediment transport
Sediment transport
Sediment transport is the movement of solid particles , typically due to a combination of the force of gravity acting on the sediment, and/or the movement of the fluid in which the sediment is entrained...
.