Airblast calculator

Air Displacements

Estimate modelled travel speed from outlet dimensions, measured airspeed, and target cross-section.

Step 1 of 4

Measure outlet area

Describe the air outlets on your sprayer. For a two-sided sprayer, the calculator mirrors the same outlet dimensions on the opposite side.

Does the sprayer operate on one side or both sides?

For both-side spraying, outlet dimensions and target cross-sections are mirrored. Airspeed is still measured independently on the left and right. For one-side spraying, only the operating side is included.

How many outlets are on one side of the sprayer?

Count the outlets on one operating side, from bottom to top.

Are all outlets on one side the same size?

Step 2 of 4

Measure airspeed

For each outlet, enter readings taken across the entire opening. The wizard calculates the mean and sample coefficient of variation independently for low and high fan gear.

High-speed air is loud and may carry debris. Use suitable eye and hearing protection and an anemometer rated for the expected airspeed.
Step 3 of 4

Target displacement volume

Define the cross-section extending from each outlet to its assigned target canopy.

Where the four measurements come from

Use the side view below to picture the cross-section assigned to one mirrored outlet pair. Measure the four blue boundaries. The illustration is schematic and not to scale. Assuming swath intended to reach middle of canopy.

Four measurements used to calculate target displacement cross-sectional areaA tower sprayer is shown on the right, a crop canopy on the left, and a blue four-sided displacement area extending from the outlet to the middle of the canopy. Arrows identify A, B, C, and D.TARGET CANOPYSPRAYER TOWEROUTLETTARGET CROSS-SECTIONABCDoutlet bottom to target bottomtarget top to outlet top
ABottom boundary: bottom of the outlet to bottom of the assigned target.
BTarget boundary: height of the assigned target canopy.
CTop boundary: top of the target to top of the outlet.
DOutlet boundary: height of the outlet opening.
Calculator step: four-sided cross-sectional area × 100 m of row = target displacement volume.
Step 4 of 4

Recommended travel speed

Displacement rate × 100 m ÷ 1,000. The recommended modelled maximum speed is set by the outlet with the lowest displacement capacity. Other outlet results are provided as secondary diagnostics.

Model limitation: This calculator does not account for canopy density and assumes that spray-laden air reaches the target intact. A mismatch may indicate overspray of an adjacent row at slower speeds or underspray of distant rows at faster speeds, potentially causing waste, drift, or poor coverage. Confirm results with field observations and coverage indicators.