We were discussing the basic difference
between orifice and mouthpiece, classification
of orifices and mouthpieces and also advantages and disadvantages of orifices in the subject of fluid mechanics, in our recent posts.

Now we will go ahead to find out the various hydraulic co-efficients, in the subject of fluid mechanics, with the help of this post.

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Now we will go ahead to find out the various hydraulic co-efficients, in the subject of fluid mechanics, with the help of this post.

We will find out here following three
types are hydraulic co-efficients as mentioned below

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**Co-efficient
of velocity, C**_{V}

_{V}

Co-efficient of velocity is basically
defined as the ratio of actual velocity of liquid jet at vena-contracta to the
theoretical velocity of the liquid jet.

Actual velocity of liquid jet at
vena-contracta will be less than the theoretical velocity due to the friction
of the orifice.

Co-efficient of velocity is denoted by C

_{V}and will be given as mentioned here

*Co-efficient of velocity = Actual velocity of liquid jet at vena-contracta / theoretical velocity*

Value of co-efficient of velocity varies
from 0.95 to 0.99 depending on the types of orifices, shape and size of
orifice.

For sharp edge orifice, value of
co-efficient of velocity will be 0.98. Theoretical velocity of liquid jet could
be understood by securing the post flow through an orifice.

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**Co-efficient
of contraction, C**_{C}

_{C}

Co-efficient of contraction is basically
defined as the ratio of area of liquid jet at vena-contracta to the area of the
orifice.

Co-efficient of contraction is denoted
by C

_{C}and will be given as mentioned here

*Co-efficient of contraction = Area of liquid jet at vena-contracta / Area of the orifice*

Value co-efficient of contraction varies
from 0.61 to 0.69 depending on shape and size of orifice and head of liquid
under which liquid flow takes place.

We will take usually 0.64 for
Co-efficient of contraction.

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**Co-efficient
of discharge, C**_{d}

_{d}

Co-efficient of discharge is basically
defined as the ratio of actual discharge from an orifice to the theoretical
discharge from the orifice.

Co-efficient of discharge is denoted by
C

_{d}and will be given as mentioned here

*Co-efficient of discharge = Actual discharge from an orifice / Theoretical discharge from the orifice*

C

_{d}= Q/Q_{th}
Where,

Q = Actual discharge from an orifice

Q

_{th}= Theoretical discharge from an orifice
Q = Actual velocity x Actual area

Q

_{th}= Theoretical velocity x Theoretical area
Co-efficient of discharge = (Actual
velocity x Actual area) / (Theoretical velocity x Theoretical area)

Co-efficient of discharge = (Actual
velocity / Theoretical velocity) X (Actual area / Theoretical area)

Co-efficient of discharge = Co-efficient
of velocity X Co-efficient of contraction

C

_{d}= C_{V}x C_{C }_{}

Therefore, we can also define the
co-efficient of discharge as the product of Co-efficient of velocity and
Co-efficient of contraction.

Value co-efficient of discharge varies
from 0.61 to 0.65 depending on shape and size of orifice.

We will take usually 0.62 for
Co-efficient of discharge.

Now we will go ahead to find out the
method to determine the various types of hydraulic co-efficients, in the
subject of fluid mechanics, in our next post.

Do you have any suggestions? Please
write in comment box.

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**Reference:**

Fluid
mechanics, By R. K. Bansal

Image
Courtesy: Google

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