Kingery-Bulmash Blast Wave Characteristics Calculator

Python implementation of the Simplified Kingery Airblast Formulas and Coefficients from:

Simplified Kingery Airblast Calculations

Swisdak, Jr, Michael M.
NAVAL SURFACE WARFARE CENTER INDIAN HEAD DIV MD
1994 Aug 01
Accession Number: ADA526744
Security Classification: UNCLASSIFIED

Applicable for TNT equivalent NEQ (Net Explosive Quantity) and hemispherical surface bursts.

Installation

Using pip to install from PyPI:

pip install kingery-bulmash

Usage

import kingery_bulmash as kb

Use prefix kb. to import all required objects. An example for a TNT eqivalent NEQ of 10,000 kg at 500 m:

import kingery_bulmash as kb

# for metric units: 10000kg at 500m
res = kb.Blast_Parameters(unit_system=kb.Units.METRIC, 
                          neq=10000, 
                          distance=500)

print(res)

Blast Parameters (Kingery-Bulmash)
NEQ: 10000 kg
Distance: 500 m
Time of Arrival: 1276.1650108864796 ms
Incident Pressure: 5.0549639655028455 kPa
Reflected Pressure: 10.244621193146642 kPa
Positive Phase Duration: 133.23344980362697 ms
Incident Impulse: 295.87689480141484 kPa-ms
Reflected Impulse: 1063.0270073779907 kPa-ms
Shock Front Velocity: 347.3295095310771 m/s

kb.Units

The kb.Units Enum is how we select the units for the calculation, it needs to be passed to kb.Blast_Parameters as either kb.Units.METRIC or kb.Units.IMPERIAL.

• kb.Units.METRIC

  for neq in kg and distance in m.

• kb.Units.IMPERIAL

  for neq in lb and distance in ft.

[!IMPORTANT] The library does not convert between units. Rather, it uses the metric and imperial parameters from the paper directly, therefore there might be slight differences between the results.

kb.Blast_Parameters

class kb.Blast_Parameters(unit_system, neq, distance, safe=True)

The Blast_Parameters dataclass calculates all the Kingery-Bulmash parameters from the paper.

Attributes:

• unit_system : kb.Units.METRIC or kb.Units.IMPERIAL

  Defines the unit system of the imput and calculated results. See kb.Units section here.

• neq: float

  TNT equivalent net explosive quantity. kg or lb based on unit_system.

• distance: float

  Distance from the explosive. m or ft based on unit_system.

• safe: bool, optional

  When True (default), kb.Blast_Parameters will raise a ValueError if any attribute is out of range. When False any attribute out of range will be set to None without raising a ValueError, this allows to significantly expand the range of values for less sensitive attributes. Default is True.

[!TIP] Blast_Parameters can raise Exception and ValueError, it is recommended to use try and except to handle this this behaviour. Python Errors Tutorial.

__post_init__ attributes:

• time_of_arrival: float, None

  Time of arrival in ms.

• incident_pressure: float, None

  Incident pressure in kPa or psi based on unit_system.

• reflected_pressure: float, None

  Reflected pressure in kPa or psi based on unit_system.

• positive_phase_duration: float, None

  Positive phase duration in ms.

• incident_impulse: float, None

  Incident inpulse in kPa-ms or psi-ms based on unit_system.

• reflected_impulse: float, None

  Reflected impulse in kPa-ms or psi-ms based on unit_system.

• shock_front_velocity: float, None

  Shock front velocity in m/s or ft/s based on unit_system.

• all_units: dict

  Dictionary containing key: value pairs where the key is the attribute name as a str and the value is the unit as str.

Methods:

• to_dict()

  Returns a dict representation of the dataclass

• __repr__()

  Inherits the default dataclass behaviour

• __str__()

  "Pretty" representation of the data as str

Examples:

Example 1: Single Attribute

import kingery_bulmash as kb

res = kb.Blast_Parameters(unit_system=kb.Units.METRIC, 
                          neq=10000, 
                          distance=500, 
                          safe=True)

#getting only incident pressure
pr = res.incident_pressure

#getting the units of incident pressure
pr_u = res.all_units['incident_pressure']

print(pr, pr_u)

5.0549639655028455 kPa

Example 2: Loop Over Range (safe=False)

In this example we set safe=False as the range of scaled distances allowed by incident_impulse is larger than shock_front_velocity which would cause a ValueError sooner if safe=True. Try and except used to handle when distance is 0.

import kingery_bulmash as kb

NEQ = 5000
for dist in range(0, 10000, 1000):
    try:
        RES = kb.Blast_Parameters(unit_system=kb.Units.IMPERIAL,
                                  neq=NEQ,
                                  distance=dist,
                                  safe=False)
        
        i_imp = RES.incident_impulse
        i_imp_u = RES.all_units["incident_impulse"]
        
        print(f'{dist} ft: {i_imp} {i_imp_u}')
    
    except ValueError as err:
        print(f'{dist} ft: {err}')

0 ft: 'distance' must be > 0.
1000 ft: 26.167261959845302 psi-ms
2000 ft: 12.835212556333252 psi-ms
3000 ft: 8.344381432625331 psi-ms
4000 ft: 6.147651070542891 psi-ms
5000 ft: 4.8505476573514335 psi-ms
6000 ft: 3.99668842429768 psi-ms
7000 ft: None psi-ms
8000 ft: None psi-ms
9000 ft: None psi-ms

Build/Install/Test From Source

The build-system is Hatch.

To build and install from source, clone the repository and in the root folder run:

hatch build

To install with pip, also from the root folder, run:

pip install dist\kingery_bulmash-X.X.X-py3-none-any.whl

Adjust the file name/path accordingly.

To run tests:

hatch test