A fluid is always a continuous medium and there cannot be voids in it. The properties of a fluid, e.g., density, may, however, vary from place to place in the fluid. In addition to shear force, fluid may also be subjected to compressive forces. These compressive forces tend to change the volume of the fluid and in turn its density. If the fluid yields to the effect of the compressive forces and changes its volume, it is compressible, otherwise it is incompressible .
a) Density (ketumpatan)
- density is highly variable in gases and increases nearly proportionally to the pressure level.
b) Specific Volume (isipadu tentu)
c) Relative Density (ketumpatan relatif)
- the ratio of the density of a substance to the density of some standard substance at a specified temperature (usually water at 4°C, for which density H2O 1000 kg/m3).
d) Specific Gravity, SG (graviti tentu)
- the density of a substance is given relative to the density of the well-known substance.
e) Specific Weight (berat tentu)
f) Compressibility (kebolehmampatan)
- refers to the change in volume (V) of a substance that is subjected to a change in pressure on it.
g) Bulk Modulus, E (modulus pukal)
h ) Viscosity (Kelikatan)
- The internal resistance of a fluid to motion or the “fluidity,” and that property is the viscosity.
- The force a flowing fluid exerts on a body in the flow direction is called the drag force, and the magnitude of this force depends, in part, on viscosity
- Fluids for which the rate of deformation is proportional to the shear stress are called Newtonian fluids
- Water, air, gasoline, and oils (Newtonian fluids) Blood and liquid plastics (non-Newtonian fluids)
- In one-dimensional shear flow of Newtonian fluids, shear stress can be expressed by the linear relationship
i) Dynamic Viscosity (Kelikatan dinamik)
- defined as shear force per unit area
Force/ Area = Force x Time = Mass
Velocity/ Distance Area Length x Area
j) Kinematic Viscosity ( Kelikatan kinematik )
- the ratio of dynamic viscosity to density
k ) Surface Tension ( ketegangan permukaan )
- a drop of blood forms a hump on a horizontal glass!
- a drop of mercury forms a near-perfect sphere and can be rolled just like a steel ball over a smooth surface!
- water droplets from rain or dew hang from branches or leaves of trees!
l) Capillary effect (Kererambutan)
- Another interesting consequence of surface tension is the capillary effect,which is the rise or fall of a liquid in a small-diameter tube inserted into the liquid.
- This effect is usually expressed by saying that water wets the glass (by sticking to it) while mercury does not
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