# 1-15 - Lecture 13 Center Pivot Nozzling I Center Pivot...

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Lecture 13 Center Pivot Nozzling I. Cen e reduced closer to the slower speed at inner points; q r r) e required near the end of the center pivot, spray nd the spray drops nearest the pivot ter Pivot Nozzling The wetted width of the application package can b pivot point because the towers are moving at a therefore, the application intensity (AR) is less ( Generally, if spray booms ar drops can be used toward the center, a point will produce something like a fine mist At the far end of the lateral the application may be more like a torrential rain Generally, impact and spray sprinklers would not be mixed on a center pivot because the pressure requirements are substantially different The minimum wetted width at any radius r along the pivot (for an elliptical pattern) can be calculated as: = d r x pa 8rU w 60T AR DE (274) where AR x is the maximum permissible application rate (mm/min) according , and vegetative cover; U d is in mm/day; T pa d as a fraction es zero for r 0 m/min) at radius r at the ground using a device with wetted diameter w d should be: to limits imposed by the soil, slope is in hrs/day; and DE is expresse Note that w r approach A suitable application device can then be selected for radius r such that the wetted diameter of the device, w d , is greater or equal to w r (w d w r ) The actual application rate (m ' d e e r d rU R O AR 7.5Tw (275) unt for evaporation and wind drift losses, and pipe leakage 0/8 = 7.5 and that we are using f = 1 day Divide by R in the above equation to obtain AR at the nozzle ing an elliptical pattern) along the lateral is: The term “R e O e ” is included in the above equation to acco Note that 6 e The wetting time at any radius r (assum ( ) f t Sprinkle & Trickle Irrigation Lectures Page 155 Merkley & Allen r r 4D t AR π where D is the total cumulative application (d R O = (276) f e e )

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