Orifice is a small opening of any cross-section ( such as circular, triangular, rectangular, etc.) On the side or at the bottom of a tank, through which a fluid is flowing. A mouthpiece is a short length of a pipe which is two to three times its diameter in length, fitted in a tank or vessel containing the fluid. Orifices as well as mouthpieces are used for measuring the rate of flow of fluid.Consider a tank fitted with a circular orifice in one of its sides. Let H be the head of the liquid above the centre of the orifice. The liquid flowing through the orifice forms a jet of liquid whose area of cross-section is less than that of orifice. The area of jet of fluid goes on decreasing and at a section C-C, the area is minimum. This section is approximately at a distance of half of diameter of the orifice. At this section, the streamlines are straight and parallel to each other and perpendicular to the plane of the orifice. This section is called Vena-contracta.
Beyond this section, the jet diverges and is attracted in the downward direction by the gravity.
Consider two points 1 and 2. Point 1 is inside the tank and point 2 at the vena-contracta. Let the flow is steady and at a constant head H. Applying Bernoulli's equation at points 1 and 2.
v1 is very small in comparison to v2 as area of tank is very large as compared to the area of the jet of liquid.
This is theoritical velocity. Actual velocity will be less than this value.
Credit:- Book Author- DR.R.K.Bansal
Beyond this section, the jet diverges and is attracted in the downward direction by the gravity.
Consider two points 1 and 2. Point 1 is inside the tank and point 2 at the vena-contracta. Let the flow is steady and at a constant head H. Applying Bernoulli's equation at points 1 and 2.
Credit:- Book Author- DR.R.K.Bansal
Comments
Post a Comment