טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentEdri Idan
SubjectPressures Due to an Internal Explosion within a Room with
Different Confining Conditions
DepartmentDepartment of Civil and Environmental Engineering
Supervisor Professor Emeritus David Yankelevsky
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Abstract

A confined explosion produces very complex pressure signals, mainly because of the reflected shock waves from the boundaries and the presence of openings. This problem has been considerably less investigated than explosion in the free air and there are open basic questions to be addressed. Understanding the confined explosion phenomenon is mandatory to predict the pressure-time history with high fidelity. The latter is essential for predicting the dynamic structural response of the envelope panels and to evaluate their resulting damage.

The present study focuses on a single cuboid with given openings for venting, that is subjected to an internal explosion at its center. Both an experimental program to provide quality pressure-time histories on the interior boundaries and numerical and theoretical studies to analyze the pressure characteristics were carried out. The study clarified major characteristics of the phenomenon and enabled high quality prediction of the pressure-time record.

To achieve the main goals of the present research the following objectives were addressed:

?  Full scale controlled tests were performed and yielded high quality pressure records that were used for comparisons with the computational results and to investigate the pressure distribution on the test room walls.

?  Numerical simulations were conducted using ANSYS AUTODYN software to better understand the governing parameters effects on the complex pressure time history. Thermodynamic and thermo-chemical processes occurring at various stages of the detonation and combustion processes were investigated and the additional afterburning energy was added into the equation of state of the explosive during an appropriate time interval.

?  Theoretical studies were conducted to provide thermo-chemical parameters of the explosive material to be incorporated in the analysis and to provide analytical simplified models to simulate the pressure record. A unique model for the gas pressure prediction was derived, based on the ideal gas equation of state. This model predicts the gas pressure as function of the charge weight per unit volume of the confined space. Moreover, a method for calculating the gas pressure decay, based on Bernoulli theory, was developed for a partially confined explosion. Comparisons of the derived formulas with our and other sources experimental results show very good agreement.

This research enhances our understanding and enables high fidelity predictions of the pressure time histories. It may contribute to enhance the analysis and design of the elements that are subjected to these pressures.