 aspect of the pregation system design and for that we will like to the emitter hydrolux basically we are interested in is that uhh what is the relationship, emitter discharge the emitter discharge and the operating pressure, where basically we are we are ultimately our main interest is how uniform the application can be applied, the irrigation application how uniform it can be applied and that since we know that it is a function of the operating pressure we also know that there are some losses which incur as we have seen in the case of sprinkler irrigation system, so the drip and sprinkler irrigation system the design aspects are almost similar you have the similar situations in the case of sprinkler irrigation system you had the along the lateral you had the discharge which was reducing discharge as you go downstream the lateral is precipitated the same was true for the main line also in this case also is the similar situation the only difference is that the pressures when you come to the lateral level pressures are much lower the pressures are much much lower in comparison to what the pressures were in the case of sprinkler irrigation system, so uhh though the philosophy will remain same but the relationships might change that is what we are trying to look into when we uhh when we go into the details of the design aspects which relationships are relevant now when we talk in terms of the drip or the uhh the trickle irrigation system. So in other words we can as we know most of us have gone through the basic hydraulic courses and we have seen that the flow regime is a very important aspect and you had you had introduced the Reynolds numbers to designate the flow regime. So in this in this case also we use we take the help of the Reynolds numbers and we evaluate the flow regime because the flow regime will decide what is the order of magnitude of the prevailing pressures and the flow regime can accordingly change which in turn will change the characteristics of the flow or in what we are interested that how the what will be the behaviour of flow in terms of the pressure variations which will be caused because of the retardance which will be introduced in the flow due to the friction losses. So the flow regimes of laminar this we have already gone through that depending on the Reynolds number we will define the Reynolds number once again. If this Reynolds number is less than 2000 the flow regime is known to be laminar. It will be a unstable flow regime if the Reynolds number is between 2000 and 10,000 is partially turbulent in this range sorry this is instead of 10,000 this is 4,000 extremely sorry and when it is 10,000 that limit will be the beginning of fully turbulent flow. So anything beyond 10,000 is a fully turbulent flow. As you know the Reynolds number is expressed as Vd by nu and because of the various dimensions which we are or the units which we are using for different items we will put this constant of 1000 also. This is the Reynolds number V is the flow velocity meters per second emitter diameter nu is the kinematic viscosity this is expressed in meters per second and normally the value of kinematic viscosity is taken as 1 into times for minus 6 it is case per second at 20 degree centigrade. Now this Reynolds number you might have seen the Moody diagram which gives a relationship between the Reynolds number and the friction factor because basically we are interested in the friction factor, how this friction factor changes with respect to the regime of the flow and that is our basic interest that is why we want to know what is the regime when you are having a particular system when it is operating at the time of design also you will know that what will be the operation policy, how it will operate, what will be the pressures which will be the preventing pressures or operating pressures and that will decide what will be the regime of the flow and accordingly you will use the appropriate relationships. Now it is from the Moody diagram you must have seen that the friction factor F there is a friction factor is a linear variation is a linear function of in the case of laminar flow it will be a non-linear and the flow is partially turbulent is also called the transition zone the friction factor where F will be a constant when you have the fully turbulent but in general you will find that the flow is very unstable in this zone when it is partially turbulent in most of the field conditions you would not be able to have such a flow available for a longer period will be either laminar or it will be turbulent flow. So as far as the relationships are concerned you will be either using the relationships depending on which what is the prevalent flow at that time with laminar you will be using those relationships which are relevant to the laminar flow otherwise you will use the turbulent flow relationships. Now let us see some of the possible relationships which might be which might be put to use when you are going for the designs and some of the possibilities are because if you look back and see that we have gone through many of the individual emitters so it will be a function of emitter what type of flow will be prevalent along with the pressures and other things. So looking at the type of emitters along with the type of flow that is what is required so you might not be going through all the possible combinations we will give you some of the possible type of emitters which are which are discussed here let us say the orifice emitter. So if you have this emitter and the flow is fully turbulent then the emitter discharge we are interested in if I designate the emitter discharge as small q this is equal to 3.6 to A into C0 to the emitter discharge is in liters per second A is the emitter cross sectional flow area millimeter square C0 is the orifice coefficient a typical value of this coefficient is taken as 0.6 normally G is the acceleration due to gravity and H is the orifice operating pressure is expressed in meters. Let us take a case of if you have a long path emitter the flow regime is laminar the emitter discharge q is expressed as this one expression now in this case this term we have already all the other terms are same only F is introduced which is the friction factor dimensionless quantity now F as you see that is a laminar flow range the flow regime is laminar in this case if you remember the moody diagram the in the laminar range the friction factor is expressed as 64 by so that is what you have to see that if your flow regime is known then you have to use the F value the friction factor value accordingly and in this case the other term which we have not expressed so far is the L which is the emitter length the emitter length is the long path emitter the emitter length is not the physical length of the emitter is the length of the path the spiral grooves which we have provided inside the long length or the long path emitter what is the length of that because that is a effective length through which the water is passing and that is what has to be used in the case of a long path emitter so that will be given when you are given that this is a long path emitter the length of the groove will also be given along with that. Let us take another case use the same long path emitter is in the turbulent regime has changed the type of emitter is same but the regime has changed to turbulent flow regime in this case the equation which will be used is also slightly different with H not including D. So this is the expression which has to be used for the turbulent flow case to find out the emitter discharge in this case the friction factors the friction factor F is having a different relationship and in this relationship the friction factor is given as this expression where this term is absolute roughness now it is a function of the ratio of the diameter to the absolute roughness because the friction factor will be dependent on what is the extent of the roughness of that material which is being used in the case of the turbulent flow. In this while using this equation you have to be careful that the units used for D and E are the same units they are not different units because earlier we have expressed D in millimetres and right now we are getting the eta is in millimetres so when you are using this both the units should be same that is very important for this relation should be there. In literature you will find that the value of the absolute roughness for different types of materials is available these are the the materials or saw the materials which are normally used for the the deprecation system network for the plastic the minimum and the maximum absolute roughness is given so you will you will get an idea that what is the range what is the range to be used or the value has to fall within this range while doing the design. The exact might change because in this case also there is rough variation between the minimum and the maximum value then the commercial steel and wrought iron this is the range galvanised iron is slightly higher so this is in the ascending order aluminium is more than galvanised iron then concrete riveted steel corrugated metal pipe. So all these these are the suggestive values which can be used while doing the design I like to go through a small problem to give you an idea that how much these parameters can change when you when you go from one regime to another regime using the same type of emitter. In this case in this problem there is some data given the given data is the design discharge is 4.0 litres per second which is the requirement the type of emitter to be used is long path emitter and the operating pressure is 10 meters you are using a microtubing which has the inside of 1 millimetre. When we are discussing the long path emitter I had not shown you but I had just mentioned that you can at outlet you can have the microtubing instead you have 1 or 2 microtubings for the water to leave the emitter. Now in this particular case is the long path emitter and the exit is through the microtube which has 1 millimetre of time and then the kinematic viscosity nu is taken as 1 into 10 to the power minus 6 meters per second. Now you are required to what is required you are required to compute the length of emic length is required if these are the required design parameters to be fulfilled that is design discharge of 4 litres per second with the operating pressure of this and the other quantities are given. In this case you can find out the velocity because Q is given area is known. So Q is 4 litres per I am sorry this is not 4 litres per second this will become too much this is 4 litres per hour the design discharge is 4 litres per hour is 4 litres per second there is a very huge discharge which is not required specifically in the case of the drip irrigation. 4 litres per hour is the design discharge and you have the area and this is 1.415 meters per second 5 meters per second knowing the velocity you can find out the Reynolds number because now you have the velocity you have the diameter you have the nu value into 1000 is what is the expression which we have used so 1.415 meters per second into 1 millimetres by minus 6 meters per second this works out to be 1415 which is less than 2000 therefore the flow regime is laminar. So you have a laminar regime if your flow regime is laminar you can find out the friction factor which is 0.0452 now once you have the friction factor then the meter discharge can be gained using the appropriate equation which we have just written earlier this was the equation which was to be used for the laminar flow for the long path emitter and this in this everything else is known but for the L and L works out to be 2.167 meter although the quantities are known we will have their values and L is 2.167 meters. Now if we change one parameter if we say that required design discharge is not 4 litres per hour but is 28 litres over this this high-disk design discharge want to find out now what is the change in length you can find out the Reynolds number and since the Reynolds number is linear function of the velocity which is again a function of the discharge you can directly find out the Reynolds number for this particular velocity which will be prevalent at that time for the discharge of 28 litres per hour by using this proportionality this will be 9905 which is almost close to value of 10000. So since is towards the fully turbulent side because this might it would not be in the unstable zone for a longer period so you can assume this to be fully turbulent case that means to get a design discharge of 28 litres per second your flow regime will become a turbulent flow regime and now the friction factor will be computed by this expression and this particular case the material which is taken for that the value of the absolute those the value of the eta which we have found out in this particular case from the table the absolute roughness is given as 0.003 which is the minimum absolute roughness for the case of the plastic. So taking eta is 0.003 here all the other quantities are known the f value works out to be 0.261 and now using the relevant equation for the emitter discharge you can find out the since the emitter discharge is known which is 28 litres per hour so you can substitute all the other values the only unknown is the length which will work out to be 0 to 4 metres. Look at the drastic variation in terms of the length requirement the moment your flow regime has changed and that is what we were saying that in this particular case when you talk in terms of the selection of flow parameters this is very important to know that will be the possible range which it can create it to and you will also have to see that what is the what is the maximum design discharge which is required or the minimum design discharge which is required whether you will have a situation where you can cater to cope up with the total requirement throughout the season of the crop. In some cases if they are the orchards then it is year after year when you do not the requirement will still change the requirement will still change because of two things one the climatic the climatic changes where you will have the seasonal variation the other will be the change in terms of the size of the plant the plant when it is small then you will have less amount of requirement as it matures the requirement will also reduce but that will only be different in the first few years once it has stabilized then will be only the climatic changes which will bring out bring about the change in the requirement and that will decide how your design should be the options can be again either you can change the number of individual points the number of emitters that can be one option or you can change the operation policy so that is where you have to decide which one is the better option whether you will like to change the number of emitters or you will like to change the pressure which will in turn change the discharge but here the only importance of this particular going through this specific exercise was to tell you that they can be a drastic change in the requirements of the system. Okay let us now let us next go into another aspect which we have seen earlier for the spring clarification system which is the uniformity the case of uniformity everything which we are doing we are doing with the assumption that we will be in a position to have uniformity of application uniformity of uhh uhh distribution of water and we had seen earlier in the previous case that uniformity cannot be 100 percent it has to be we have to lose something you have to lose some uniformity the higher the coverage you want to have so if your extent of the network is very large then your chances that the uniformity will be you will be doing that at the expense of the uniformity that is very important to understand because that will decide on your layout it will also decide the pattern of your operation because if you have a very big area the layout is not the only factor which will uhh which will decide will be the uniformity you might be having a layout but if you are operating in in segments then you are reducing the extent of the the the the network which is influencing all these variations. So that is very important aspect when you go in for the design you will have to take all those things into picture. Let us look at the emitter uniformity as we have mentioned in the beginning of this topic that the emitter uhh system or the the trickle system is basically is intended to have a very close relationship between the crop water requirement and what is uhh uhh being supplied in terms of the the emitter discharge. Now the emitter uniformity becomes more important because of this fact because if the the discharge which you are supplying is not taking care of the requirement and since the requirement has to immediately match with the the discharge you do not have very very large interval which is available because of the fact that you are not at no time you are trying to replenish the total deficit which we have been doing in the case of earlier irrigation systems where we were trying to make use of the storage available in the the soil that soil storage we are trying to dump the water in that storage and then keep on using that water for a longer duration. The dumping is at a uhh at a much let us let us put it this way that the dumping is at a much quicker rate so you are using the the basic storage which is available in the soil by bringing the soil moisture to the field capacity level whereas in this particular case you might not be doing that. You are keeping the deficit some level of deficit still might be there and in some cases if you even if you have started with a low level of deficit by providing the the uniform uhh rate of uhh input you are keeping the deficit at a lower level. If you wait for a longer period the deficit might increase which might in turn uhh increase the the stress in the crop so that will have a detrimental effect. So in this case since we are the rate at which we are supplying the moisture is very low if you are if your uhh crop water requirement is not being satisfied if there is a deficit which is being created continuously then if you accumulate that deficit over some period it might become so much it will have some drastic uhh some ill effect on the the crop system or the the the crop uhh that particular plant or even that row of crop. So the uniformity becomes more important from that angle. The uniformity in this case we we uhh measure in terms of emission uniformity is only a nomenclature given to the uniformity if we call u e as the emission uniformity this is expressed this is expressed as 100 into this is uhh expressed in percentage so 101 minus 1.27 by n into c v q minimum divided by q average the various terms which are used here this is the emission uniformity in percentage n is the number of emitters a plant let me let me tell you that this is the uniformity of discharge along a lateral the emission uniformity which we are expressing through this is the uniformity of discharge along a so n will be the number of emitters per plant the case of point source emitters it can also be this one case either n will be this if you have uhh the point source emitters if you have used the point source emitters on a permanent crop or n will be case A spacing between unit length of lateral line manufacturers or manufacturers to compute c v c v is basically the coefficient of variation and b is case p is 1. Now the n value in this particular case will be either of the two uhh whichever is greater than 2 cases cases A and B which we have given for a line source that is how you determine the n it will be either of the two cases whichever is the greater value when you have the line source if you have the point source then it will be the number of emitters per plant c v is the is the manufacturers specified coefficient is provided by the manufacturer is the coefficient of variation coefficient of variation of discharge and that is normally when the manufacturer provides emitter he gives the value of the coefficient of variation of discharge and q minimum is the minimum meter discharge litters per hour similarly the q maximum is the where we are calling it q average q average is the average or design discharge litters per hour that means if you know the various quantities if you know what is the minimum discharge which is prevalent in a particular setting what is the q average you can find out how much is the uniformity the emission uniformity provided you also know what is the value of c v and you know what is the type of setting or the type of system which you have adopted that will decide what is the n value the c v is is available for various types of emitters which have been manufactured by the various manufacturers. Now I will like to give you some values of c v is for some different types of emitters and how they can be classified on the basis of the c v value this is this recommendation is given by the American society of agriculture engineers recommended to the classification where this is while selecting a particular emitter you can you can see that whether what type of emitter it is whether it is good looking at the value of c v whether it can be accepted or you should not be accepting it so the emitter type the value of c v and the classification which has been put into depending on the value of c v. For point source emitters if the value of c v is less than point naught 5 can be termed as a good emitter if it is between point naught 5 and point 1 is average it is marginal and if it is more than point 1 5 is unacceptable so if your coefficient of variation is quite excessive should be using those emitters similarly for line source emitters if it is less than naught 1 is good. So in comparison the coefficient of variation will be higher in the case of line source is unavoidable you can have a better coefficient of variation in the case of point source is between point 1 and point 2 average class it belongs to average class and greater than point 2 is marginal or you can also term it as unacceptable. Similarly there is another information of the table which is provided which can also give you reasonable level of information in terms of what is the emission uniformity which is achievable with respect to the different types of emitters and with respect to the various types of crop spacings. So this is the design standards for the emission uniformity again this recommendation is given by the American Society of Agriculture Engineers this table I think I will stop here for a while before we discuss this table and then we will go into the extension of this topic.