We were discussing the basicÂ difference between orifice and mouthpiece, in the subject of fluid mechanics, in our last post. Now we will go ahead to find out the classification of orifices and mouthpieces i.e. types of orifices and mouthpieces.

First we will see here the classification of orifices and after that we will see the classification of mouthpieces. So let us come to the main topic, without wasting your time.

### Classification of Orifices

As previously discussed that an orifice is basically a small opening of any cross-section such as triangular, square or rectangular on the side or at the bottom of tank, through which fluid is flowing.

Orifices are classified on the basis of their size, shape, nature of discharge and shape of the upstream edge. There are following types of orifices as mentioned here.

#### A. Orifices are classified on the basis of size and head of liquid from centre of orifice

Small orifice:
If the head of the liquid from the centre of the orifice is more than five times the depth of orifice, that orifice will be termed as small orifice.Â

Large orifice:
If the head of the liquid from the centre of the orifice is less than five times the depth of orifice, that orifice will be termed as large orifice.

#### B. Orifices are classified on the basis of their cross sectional area

On the basis of the cross-sectional area of the orifice, orifices are classified as circular, rectangular, triangular and square orifices.

#### C. Orifices are classified on the basis of shape of upstream edge

On the basis of shape of upstream edge of the orifice, orifices are classified as sharp edges orifices and bell mouthed orifices.

#### D. Orifices are classified on the basis of nature of discharge

On the basis of nature of discharge, orifices are classified as free discharging orifices and fully drowned or submerged orifices.

#### E. Orifices are classified on the basis of sub-merged condition

On the basis of sub-merged condition, orifices are classified as fully sub-merged orifices and partially sub-merged orifices.Â

### Classification of MouthpieceÂ

Mouthpiece is basically a small length of pipe which will be installed with the tank or vessel containing the fluid. Length of this small pipe will be approximate two to three times of its diameter.

Mouthpieces are classified on the basis of their position with respect to the tank, their shape and nature of discharge. There are following types of mouthpieces as mentioned here.

#### A. Mouthpieces are classified on the basis of their position with respect to the tank

On the basis of their position with respect to the tank or vessel to which they are fitted, mouthpieces are classified as external mouthpieces and internal mouthpieces.

#### B. Mouthpieces are classified on the basis of their shape

On the basis of their shape, mouthpieces are classified as cylindrical mouthpieces, convergent mouthpieces and convergent-divergent mouthpieces.

#### C. Mouthpieces are classified on the basis of nature of discharge

On the basis of nature of discharge at the outlet of mouthpiece, mouthpieces are classified as mouthpieces running full and mouthpieces running free.

If the jet of liquid after contraction does not touch the sides of mouthpiece, mouthpiece will be termed as running free.

If the jet of liquid after contraction expands and fills the whole mouthpiece, mouthpiece will be termed as running full.

Now we will go ahead to discuss the advantages and disadvantages of orifices and mouthpieces, in the subject of fluid mechanics, in our next post.

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### Reference:

Fluid Mechanics, By R. K. Bansal