USER GUIDE

Customizing VBS3Fires

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VBS3Fires v3.6.3 User Guide

26.5.1 Aerodynamic Drag (drag.dat)

This file determines the drag profile for a projectile flying though the atmosphere. It defines the way

that the drag changes based on the Mach number (speed relative to the speed of sound) of the

projectile. The sample file shown in the appendix displays some example values for the file.

VBS3Fires will ignore the first line of the file, and then read the Mach number entries in order,

performing a linear interpolation between entries. In other words, the mach numbers should always

be present in ascending order in the file. They correspond to points on a chart, with straight lines

used to join the specified points up to each other.

The Aerodynamic Drag is defined in a file called drag.dat.

26.5.2 Atmosphere profile (atmosphereProfile.dat)

This file determines the temperature (in Kelvin) and density (in kilograms per cubed meter) of the

atmosphere as varying heights.

Entries in this file should be entered in ascending order of altitude (in meters). The first line of the

file is ignored by VBS3Fires. Linear interpolation is performed between entries to provide a changing

value for density and temperature over each band.

The atmosphere profile file is called atmosphereProfile.dat.

26.5.3 Met Table (met.dat)

This file contains the wind data which may be defined at varying wind bands. The first line of the file

is ignored, and then any line after that is deemed to represent a band. Each line defines a height (in

meters), a wind speed (in meters per second), and a wind direction (in degrees).

The altitude is deemed to be the bottom of the band with all altitudes above that having the same

wind and direction until the next altitude value in the file is reached. The wind direction and speeds

are the same within each band and no interpolation occurs within Fire within the bands.

The met table file is called met.dat.