General formula to calculate the fragment velocity of warheads with hollow core

In some novel warheads, the explosive charge is not compactly filled within the cylindrical casing but has a hollow core instead. However, most existing formulas can only predict the fragment velocity of warheads fully filled with explosive charge. In this work, through theoretical analysis and numerical simulations, a new formula was proposed to predict the initial fragment velocity of novel warheads with hollow core. The formula was built on top of the Gurney formula and made use of a correctional function to account for the effects of the rarefaction wave from the hollow core of the explosive charge on the fragment velocity. The formula showed good agreement with the experimental results in the validation tests. Hence, the proposed formula is suitable for predicting the initial fragment velocity of warheads with hollow core.