The higher the velocity of the air current, the greater will be the
resistance to airflow. The resistance is nearly proportional to the
velocity squared. Mason
a. The average velocity of water in a channel at the point where the depth
over a flow measuring weir is recorded. Hammond
b. The mean velocity in the conduit immediately upstream from a weir, dam,
Venturi throat, orifice, or other structure. Seelye, 1
a. The velocity with which the shock wave traverses an explosive charge on
detonation. BS, 12
b. The velocity of detonation of an explosive was previously determined by
what is known as the Dautriche test. The basis of this test is that a
length of Cordtex detonating fuse detonates at a uniform speed, and if the
two ends of a length of Cordtex are detonated simultaneously, the
detonation waves will meet at the middle of the length of fuse. Similarly,
if the two ends are detonated at different times, the distance from the
middle of the fuse to the point where the two detonation waves meet is
directly proportional to the interval of time between the detonations of
the two ends of the Cordtex fuse. Furthermore, if the distance can be
measured, the interval of time between the detonation can be calculated,
since the velocity of detonation of Cordtex is known.
Syn:Dautriche test
An average velocity of flow of a liquid just downstream of a measuring
weir. Hammond
a. The pressure equivalent of the air velocity at any particular point.
This is always positive. BS, 8 b. The pressure exerted by a moving fluid in the direction of its motion.
It is the difference between the total pressure and the static pressure.
Strock, 2
c. In Mine ventilation, the pressure exerted by the kinetic energy of air
movement. Syn:velocity head
d. The algebraic difference between the total head and the static
pressure. Roberts, 1
A linear arrangement of sensors used to record reflections over a large
range of shot-to-geophone distances, which is used to determine seismic
velocity from the time-distance relationship. AGI
The ratio of the distance through which the force applied to a machine
moves, and the distance through which the load moves.
See also:mechanical advantage
This type of collector is designed to remove very large dust particles. It
is often used ahead of other collectors to reduce the dust load, and to
remove the particles most likely to cause abrasion. The velocity reducing
collector has no moving parts and, in most instances, can be installed in
front of the induced draft fan, reducing the abrasion of the fan blades.
This type of collector also can be used under many high-temperature
conditions. Pit and Quarry
A small portable direct-reading instrument used to measure the velocity of
air at a point. Hartman, 2
Profit; easily earned money. Fay
Cyanotrichite in bright blue velvetlike druses and spherical forms.
Syn:lettsomite; cyanotrichite.
Products sold by coal mine annually. Pryor, 3
A variety of fossil resin from Vendee, France. Tomkeieff
A high-grade ferric-oxide pigment of a purer red hue than either light red
or Indian red. Obtained either native as a variety of hematite red or more
often artificially, by calcining copperas in the presence of lime. The
composition ranges from 15% to 40% ferric oxide and from 60% to 80%
calcium sulfate. The 40% ferric oxide is the pure grade, and sp gr, 3.45.
CCD, 2
Migmatite of which the mobile portion(s) were formed by exudation
(secretion) from the rock itself (Dietrich & Mehnert, 1961).
CF:veined gneiss; composite gneiss. Not widely used. AGI
a. In explosives, a small passage made with a needle through stemming, for
admitting a squib to enable the charge to be lighted.
b. A hole, extending up through the bearing at the top of the core-barrel
inner tube, that allows water and air in the upper part of the inner tube
to escape into the borehole or into the annular space between inner and
outer barrels. Long
An enclosed airway to direct airflow to a given area or location.
MSHA, 4
See:motive column
A current of air traveling in mines. Peel
a. The total head in pascals or kilopascals required to overcome the
friction of the air in mines and to provide some final or exit velocity to
discharge the air to the atmosphere.
b. The total pressure exerted on the atmosphere by the mine fan to
overcome the resistance of the mine to the passage of a required volume of
air throughout the mine necessary for its ventilation.
See also:mine total head; fan total head; total ventilating pressure.
Kentucky