 Myself Deshmukh Sachin, I am working as the assistant professor in Valgenstrup Technology Civil Engineering Department. Students today we are going to learn about the orifice meter and we are going to see the concept that is flow through orifice meter. These are the outcomes. At the end of this topic you are able to understand the concept of orifice meter and you can calculate the discharge through the orifice meter. First of all I will recall orifice meter is one of the application of Bernoulli's equation. Venturi meter was also the application along with rotometer, then pitot tube. These are the applications of Bernoulli's. We know the working of venturi meter. Now we will see what is the orifice meter and how it works. An orifice meter or you can say the orifice plate is a device employed for measuring the discharge. It works same that is the principle as the venturi meter. It consists of a flat circular plate having circular sharp-aged hole. The hole that is the diameter is called as a orifice meter. The concentric with the pipe it is concentric with the pipe. The diameter of orifice may vary from 0.4 to 0.8 times the diameter of the pipe. In simple way you can say it is an opening provided at the side of the tank or at the bottom of the tank to measure the discharge through the tank or through the storage. See this figure you can see here this is a pipe this is a pipe diameter this is a flow and this is the orifice plate this is the orifice plate. Actually the one thing comes in our mind the Bernoulli's equation because Bernoulli's equation that we are going to apply at two sections section one and section two. Now the thing comes in our mind it is a thin plate and where we are going to apply the Bernoulli's equation definitely we are going to apply at this end at the first and at the second here you can see we can apply this we may say this is the controlled volume. Now see here the behavior here due to the reduced area the area has been reduced due to this orifice plate. So here you can see here you can observe here you can observe the diameter is reduced here you can observe the diameter of the jet is reduced the reduced diameter is called as a Vena contracta this is a very important term keep in your mind Vena contracta it is used to calculate the coefficient of contraction okay. Now see okay this is a simple figure and the manometer is attached manometer is attached this is a you can say the difference in the manometric liquid similar similar as we are done for the venture meter okay we will proceed further liquid flows through the pipe the flow suddenly contracts as it approaches the orifice meter or orifice plate you can say and then suddenly expands after the orifice back to full with the full pipe diameter this forms a Vena contracta just now we have seen or a throat immediately pass the orifice this reduction in the flow pattern at the Vena contracta causes increased velocity and hence lower the pressure at the throat because they are inversely proportional that is velocity as well pressure the same thing that we have seen in the venture meter. Now we will find the equation to calculate the discharge through the orifice meter these are the notations d1 at the diameter of the section 1 p1 pressure at section 1 v1 velocity at section 1 area 1 or a1 as at the area at section 1 similarly d2 p2 v2 a2 are the corresponding values at section 2 so with applying the Bernoulli's equation we know p1 upon w plus v1 square upon 2g plus z1 that is the total energy you can say pressure energy, kinetic energy and potential energy at section 1 it is equal to section 2. So we can calculate this h okay because p by w is equal to h or p1 minus p2 upon w is h which is equal to v2 square upon 2g minus v1 square upon 2g take this v1 on other side on the left hand side so that you will get v2 square upon 2g is equal to h plus v1 square upon 2g again simplify it you will get v2 is equal to under root 2gh plus v1 square. Now section 2 is at Vienna contractor where the area is reduced and a2 represents the area okay so and a0 a0 that is a suffix 0 it is a area of the orifice then we will get coefficient of contraction coefficient that cc is coefficient of contraction it is the ratio of area of Vienna contractor to area of the orifice area of Vienna contractor to the area of orifice. So a2 which is area of area at Vienna contractor is equal to a0 a0 into cc that is coefficient of contraction we know the continuity equation a1 v1 is equal to a2 v2 similarly v1 is equal to a0 cc v2 upon a1 that is only the steps we have followed and we have calculated what is v1 and what is v2 now substituting the value of v1 in the above equation we get v2 is equal to under root 2gh a0 square cc square v2 square upon a1 that is a1 square okay again simplified we will get v2 is equal to under root 2gh upon under root 1 minus a0 square upon a1 square into cc square discharge formula that is q is equal to a1 v1 or a2 v2 is equal to this is you can say v a2 is calculated that is a0 cc which is equal to a0 cc into v2 and put this value that q is equal to a0 cc and v2 is v2 is under root 2gh this one under root 2gh upon under root 1 minus a0 square upon a1 square cc square again simplified again simplified okay we will get cd that is coefficient of contraction again simplified then then substituting the values substituting these values we get finally we get finally q is equal to cd upon cd into a0 a1 under root 2gh upon under root a1 square minus a0 square you just recall the equation for the venture meter that is q theoretical that is discharge theoretical for venture meter is a1 that is a1 a2 under root 2gh upon under root a1 square minus a2 square it is in the similar way it is in the similar way only the thing that you have to take into account with coefficient of contraction as well as coefficient of discharge coefficient of contraction and coefficient of discharge okay this is also the important term and then this formula can be used for calculation of discharge through orifice meter some coefficients related to with orifice meter are that is coefficient of contraction it is the ratio of area of jet at when a contractor to the area of jet of orifice coefficient of velocity it is the ratio of actual velocity of the jet at when a contractor to the theoretical velocity and coefficient of discharge that is it is the ratio of actual discharge of the to the theoretical discharge what is the difference between an inch meter and orifice meter it is venture meter is device which is inserted in the pipeline to measure the incompressible fluid flow rates okay it is a major it can be measuring through the venture meter can be used to for measuring the flow rates of all incompressible flows and venture meter the flow velocity is measured by noting the pressure difference okay in the inlet and throat whereas orifice meter the velocity measured by using p-tort tube or tragic tree method these are the review questions just go through these equations and these are the answers the answers okay the cheapest device is orifice meter the principle of orifice meter same as orifice meter is true orifice meter can be used for measuring the rate of flow in the open in open pipe like structure though it is wrong and coefficient of velocity is the ratio of actual velocity of the jet to the to the theoretical velocity this is true you just concentrate on this also that is difference between venture meter and orifice meter also okay so these are the answers just go through once again these are the reference books if you find any difficulty you can contact me thank you