Feasibility of an onboard wake vortex avoidance system

It was determined that an onboard vortex wake detection system using existing, proven instrumentation is technically feasible. This system might be incorporated into existing onboard systems such as a wind shear detection system, and might provide the pilot with the location of a vortex wake, as well as an evasive maneuver so that the landing separations may be reduced. It is suggested that this system might be introduced into our nation's commuter aircraft fleet and major air carrier fleet and permit a reduction of current landing separation standards, thereby reducing takeoff and departure delays

The measurement of droplet size distributions from rotary atomizers

Various experimental techniques have been developed to recover droplet size distributions emitted from rotary atomizers. These techniques include both single line-of-sight measurements through the center of the spray cloud and volume weighted averaging from multiple passes through portions of the spray. Because the droplet size distribution of a spray is one of the most important inputs into aerial spray prediction models such as AgDRIFT®, a consistent, widely-accepted standard for rotary atomizers should be developed and implemented with regard to this measurement. No such standard currently exists. The present paper summarizes current measurement techniques and develops a simple computer model to predict droplet movement following emission from a rotary atomizer in a wind tunnel. Qualitative comparisons are made with available data to demonstrate the effects of single line-of-sight measurements and weighted averaging from multiple passes

Suggested revisions to ASAE standard S572 Aug99

The development of ASAE Standard S572 Aug99 helped the industry and applicators respond to drift issues raised by the U. S. Environmental Protection Agency and concerned environmental groups. However, application of the standard to existing nozzles and tank mixes raised three concerns: (1) how to classify a drop size distribution when the drop size spectrum crosses classification categories; (2) how to define the driftable portion of a drop size distribution; and (3) how to expand the ASAE Standard so as to better delineate classification categories. The first question was addressed in a paper presented at the NAAA/ASAE meeting in December 2003 in Reno, NV, in which it was demonstrated that the standard should be used to recover drift potential, correlated to readily determined parameters such as D , D , and D , and thereby unambiguously nail classification categories for all nozzles and tank mixes. The second and third questions will be addressed in this paper, by determining the drop size that drifts from an aerial application and by proposing additional reference nozzles to expand the classification categories

A review of ground sprayer data and a preliminary analytical model

This paper summarizes the ground sprayer data collected by the Spray Drift Task Force (SDTF) and discusses its implementation as the Tier I model in AgDRIFT®. Preliminary analytical Lagrangian ground sprayer modeling efforts by the SDTF and the USDA Forest Service, to accurately and rapidly predict the deposition downwind from a spray block for any set of initial conditions, are also discussed

Characterizing granular material in aerial application

The ASTM Standard: Standard Test Method for Particle Size Distribution of Granular Carriers and Granular Pesticides (E726-01) is the only ASTM standard that specifically addresses the characterization of nonspherical particles. To our knowledge there is no standard for particle size distribution measurements by laser diffraction or for particle sphericity measurements by any means to complete the description of the granular material. The present paper reviews a modeling effort that effectively characterizes and then represents the behavior of nonspherical particles during aerial application, highlights the difficulties inherent in interpreting light scattering by nonspherical particles, and suggests a laboratory experiment that accurately recovers particle sphericity. Model revisions enable the user to select the granular application technique from a menu of options once the granular material has been adequately parameterized. Quantitative comparisons are made with available field data to demonstrate the implementation of the several available granular material delivery systems. Notice is made that a standard should be developed for measuring (1) particle size distributions using laser diffraction instruments, and (2) particle sphericity with a technique suggested in the paper

Initial laboratory measurements of the evaporation rate of droplets inside a spray cloud

This article calculates the evaporation rate of water droplets stacked on several threads, positioned downwind of one another. The measurement approach was used previously to determine the evaporation rate of isolated suspended droplets, on a single thread, for development of the Spray Drift Task Force (SDTF) droplet evaporation data base. Here, the effect of evaporating droplets upwind of other droplets is examined, recovering the effective evaporation rate of individual water droplets surrounded by other water droplets in a spray cloud. The results quantify the modified wet bulb temperature depression felt by the droplets within the cloud and are used to compare AGDISP model predictions with SDTF aerial deposition data

The need for nozzle emission spectra in drift mitigation

Aerial application models, such as AgDRIFT®, rely on an accurate nozzle emission spectrum to quantify the effects of atomization on deposition and drift. In this paper we explore the consequences of approximating the droplet size distribution and the implications of the accuracy of that approximation for downwind drift and the setting of buffer zones