Criteria for jet formation from impinging shells and plates

Abstract

Criteria on jet formation and jet cohesiveness are proposed for collapsing solid plates and shells. These criteria are also applicable to impinging fluid sheets from plane or annular nozzles. Under the high impact speeds treated here, the solid plates or shells behave as compressible fluids; for the impinging fluid sheets compressibility effects will also be assumed important. Jetting will occur if either the collision is subsonic or the impinging angle is large enough such that the shock in the flow is not attached at the collision point. Jets formed from subsonic collisions are coherent; those from supersonic collisions are not coherent. The criteria are shown to be in general agreement with available experimental evidence. Further, the proposed criteria are also verified by two-dimensional unsteady finite-difference computer calculations. In addition, these calculations indicate the mechanical reasons for the coherency or noncoherency of the jet under various impact conditions. The practical applications of these criteria include collapsing shaped-charge liners, the explosive welding of plates, and steady impinging fluid sheets from annular nozzles.

Physics of Hypercumulation: Jet Formation in Shaped Charge and Ablatively-Driven Implosion of Hollow Cones

“…As it well known hydrodynamic theory by G. Taylor, G. Birkhoff [6] and M. Lavrentyev [7] promotes first approximation for the analytical solution of the problem provided that jet forming is managed by steady outflow laws. In experiments mentioned above, cones and wedges were imploded onto their axes by pressure generated via laser ablation of their outer surfaces and were based on classical hydrodynamic theory of cumulative jet.…”

“…For classical shaped charge conditions and geometry, relative jet velocity Vjet and mass Mjet respectively are related to the apex half-angle α as [6][7][8] Vjet~cot(α/2), Mjet~sin2(α/1) (1) Formulae (1) predict that very high jet velocity can be achieved at very small angles α. From the hydrodynamic theory it is followed that compressibility imposes a lower limit on α and reduces the mass of a jet in comparison with Eqs.…”

“…From the hydrodynamic theory it is followed that compressibility imposes a lower limit on α and reduces the mass of a jet in comparison with Eqs. (1).It is important that at angles smaller than this lower limit, i.e., α < αcrit, the cumulative jet is not produced [5][6][7]. In an ideal gas and wedge geometry, classical theory predict αcrit = sin-1(1/γ) [6][7][8] where γ is the adiabatic exponent.…”

“…(1).It is important that at angles smaller than this lower limit, i.e., α < αcrit, the cumulative jet is not produced [5][6][7]. In an ideal gas and wedge geometry, classical theory predict αcrit = sin-1(1/γ) [6][7][8] where γ is the adiabatic exponent. For γ = 5/3 the corresponding apex angle are relative large 2αcrit = 74° [2].…”

The theoretical analysis and numerical simulation of the metal jet incoherence

“…Although the supersonic collision to form stable metal jet is possible, the incoherence jet phenomenon have been observed from experiments in the supersonic region. The assumption is proposed by Zhou [1] (θ c is the limit angle to produce the attached shock wave):…”