Page 360 - Civil Engineering Formulas

CHAPTER 12
HYDRAULICS

AND WATERWORKS

FORMULAS

To simplify using the formulas in this chapter, Table 12.1 presents symbols,
nomenclature, and United States Customary System (USCS) and System Inter-
national (SI) units found in each expression.

CAPILLARY ACTION

Capillarity is due to both the cohesive forces between liquid molecules and
adhesive forces of liquid molecules. It shows up as the difference in liquid sur-
face elevations between the inside and outside of a small tube that has one end
submerged in the liquid (Fig. 12.1).
Capillarity is commonly expressed as the height of this rise. In equation form,
2 cos
h (12.1)
(w 1 w 2 )r
where h capillary rise, ft (m)
surface tension, lb/ft (N/m)
w and w specific weights of fluids below and above meniscus, respec-
2
1
tively, lb/ft (N/m)
angle of contact
r radius of capillary tube, ft (m)
Capillarity, like surface tension, decreases with increasing temperature. Its
temperature variation, however, is small and insignificant in most problems.

VISCOSITY

Viscosity of a fluid, also called the coefficient of viscosity, absolute viscosity,
or dynamic viscosity, is a measure of its resistance to flow. It is expressed as the

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