# Study on the Interference Process of Liquid Radial Reflux on the Stability of a Shaped Charge Jet
## 1 Introduction
[PERSON] and [PERSON] [12] investigated the penetration behavior of copper, aluminum, and tantalum molding jets in water by using high-speed photography and intermittent switching technology. [PERSON] and [PERSON] [13] demonstrated that a closed structure full of liquid has a good interference effect on the jet through experiments. [PERSON] [14] studied the penetrating behavior of jet particles in water through high-speed photography and X-ray experiments. [PERSON] [15; 16] modified Szendrei equations and obtained the reaming equations of jet penetration in water through high spatial and temporal resolutions and profile-streak technology. [PERSON] [17] performed X-ray photography and found that the collapse of the penetration channel leads to complete disappearance of the jet tail during its penetration into a water-filled airtight container. From an engineering viewpoint, [PERSON] [18] proposed a new type of protective armor comprising a sealed steel box unit structure filled with water and calculated the interference of this armor in the jet flow. [PERSON] [19; 20] and [PERSON] [21; 22] established a theoretical model of the interference mechanism of fluid-filled single-cell structures in jets. [PERSON] and [PERSON] [23; 24] determined the relationship between the residual penetration of the jet and the physical parameters of the target, jet, and liquid material through dimensional analysis. [PERSON] [25; 26] established a theoretical model to calculate the velocity interval of a jet subjected to interference by considering the compressibility of the liquid and the multiple impacts of the jet on the liquid and used the lateral velocity method to calculate the residual penetration depth. [PERSON] [27] presented experimental and theoretical investigations of the penetration capability of the residual SCJ emerging from the liquid-filled compartment structure after the penetration process at different impact angles. [PERSON] et al. [19; 20; 21; 22; 23; 24; 25; 26] established a calculation model for the velocity interval of a disturbed jet. However, they ignored the interference of the liquid radial reflux driven by the bottom plate reflection and the side-wall secondary reflection waves on the jet, which would introduce errors in the calculation of the interference velocity interval. The interference of liquid radial reflux in the SCJ by the LFCS in this paper can be divided into the following three parts: bottom plate reflection interference, side-wall reflection interference, and side-wall secondary reflection interference. A theoretical model, which can accurately calculate the velocity interval of the disturbed jet and the residual penetration depth of the jet, is established considering the change in liquid sound velocity and the propagation path of shock waves. The calculation revealed that the interference of the LFCS in the SCJ is mainly concentrated in the tip and middle part of the jet. The AUTODYN-2D hydrocode and the Euler-Lagrange coupling algorithm are then used to demonstrate intuitively the three stages of the liquid reflux interfering jet driven by shock waves, which verifies the accuracy of the theoretical analysis. Finally, X-ray technology is used to capture the shape of the jet penetration in the LFCS, and the velocity interval of the disturbed jet is calculated. The experimental results show that the liquid composite structure has an obvious interference effect on the high-speed section of the SCJ, and the theoretical model established in this paper can accurately calculate the disturbed velocity interval and the residual penetration depth of the jet. Therefore, the theoretical model can be used to guide the design of the LFCS and predict its anti-jet capacity.