Atomization Models

Nozzle Models Update Information:

July 12, 2017 - All models updated to correct error in calculation of boom flow rate.

October 30, 2017 - All models updated with Extra Coarse/Ultra Coarse Classification Categories

March 2, 2021 - Fixed Nozzle and Pressure models fixed for calculation error in DV10, DV50, DV90 and %<100 um.

November 30, 2022 - Updated High Speed Nozzle Models with 2 new Straight Stream nozzles.

 

The USDA-ARS Aerial Spray Nozzle Models were developed to provide aerial applicators with a tool for determining the droplet size resulting from an application scenario based on the nozzle used and the operational conditions of the application.  They provide a quick and easy interface providing the user with droplet size and classification information based on the nozzle being used as well as the operational conditions of the application (orifice size, spray pressure, orientation angle and airspeed).  These models are currently two versions of these models, one termed as “Low Speed” and one termed “High Speed”.  Low speed refers to nozzles operating in airspeeds below 120 mph while high speed refers to nozzles operating in airspeeds above 120 mph.  It should be noted here that only the airspeed is critical when selecting which set of models to use, the platform (fixed versus rotary wing) does not matter.  Not all nozzles are available for both speed ranges, but new data is added from time to time.

Applicators are responsible for appropriate setup and operation of their spray system to ensure applications meets product label requirements and provide the most efficient delivery of the product to the target while mitigating off-target movement.  Complying with the label requirements, related to spray system setup, typically means falling within a specified spray rate and targeted droplet size or spray classification.  Spray rate and droplet size are typically tied together as changes in airspeed, pressure or orifice to meet a certain droplet size class will generally also change application rate, or vice-a-versa, and typically requires an iterative approach to meeting both.  The nozzle models make short work of determining droplet size and class, but determining the resulting spray rate, in gallons per acre, requires taking the airspeed, spray pressure, nozzle orifice size, effective swath width and number of nozzles used and going through a series of calculations to determine total boom flowrate, per nozzle flowrate and finally number of nozzles required.  If the number of nozzles required does match with a given setup requirement, this process of changing one of the operational settings, determining droplet size, then determining boom and nozzle flowrate and nozzle number is repeated until the desired setup is obtained.

To help expedite this process, and to encourage applicators to download and actively use the droplet sizing models as part of their everyday operations, the nozzle and boom calculations have been integrated into the atomization model spreadsheets.  This updated interface is more than just a droplet size calculator.  There are currently three versions available for your download and use.

The first version is very much that same as the versions that have been in circulation for a number of years now, with the exception that where the graphical representation of droplet size once resided, now contains the boom and nozzle flowrate and nozzle number calculations.  To use these models, simply select your nozzle, then enter or select your orifice size, nozzle angle, spray pressure and airspeed, and finally in the bottom half of the interface enter your spray rate and effective swath width.  With this information entered, the models will determine droplet size, classification as well as calculate the total boom and per nozzle flowrate required as well as the number of nozzle needed.

The low and high airspeed versions of these models can be download here (Click on the pictures to download the Excel file):

High-Speed Models

Low-Speed Models

 

A second version integrates to low and high airspeed models into a single worksheet and rather than having the user specify the nozzle and operational settings, allows them to specify the operation airspeed, the spray rate, effective swath width, the number of nozzle to be used and the droplet size classification (FINE, MEDIUM, COARSE, etc…) required.  With this information, the model returns a listing of the combinations of nozzle type, orifice size, orientation angle and spray pressure that meet the entered requirements.  The detailed droplet size data is also given for each combination.  A user simply selects whether they want to use the high airspeed (120-180 mph) models or low airspeed (50-120 mph) models.  After which they enter the airspeed, spray rate, swath width, number of nozzles and droplet size classification required.

This version can be downloaded here:

Fixed Nozzle Quantity Models (shows multiple setup outcomes)

 

And finally, the third version is very similar to the second version, but rather than specifying a single number of nozzles to be used, the user specifies the spray pressure and a range for the number of nozzles.  The model then returns a list a the combinations of nozzle type, number, orifice size, and orientation angle the provide the user specified spray rate and droplet size classification.  Like the other versions, the detailed droplet size data is also provided for each combination.

This version can be downloaded here:

Variable Nozzle Quantity Models (shows multiple setup outcomes)

 

These updated nozzle model interfaces are not meant to supplant any current practices or setup calculations that you may use, rather to provide you with an enhanced, more efficient interface with the current models.  We also encourage you as you work on setting up your aircraft spray booms to attend and Operation S.A.F.E. clinic to have your spray pattern evaluated and adjusted.  More information on Operation S.A.F.E. can be found here:

 

Currently this new boom and nozzle calculation feature is limited to the Excel versions of the models.  The droplet size only versions are available at the Apple App store here:

 

We hope users will give these enhanced versions a test drive and let us know what they think.  We are working to add new features that offer even greater utility, and would welcome your feedback on things you would like to see in future updates.  If you have any suggestions for how we can improve them, please contact us (Brad.fritz@ars.usda.gov).   We look forward to your feedback and hope these new versions provide you extra incentive to routinely use the nozzle models as you set up your airplanes this coming season.