Study on similarity tests and numerical simulation characteristics of stiffened cylindrical shell structures under strong impact loading

Under strong impact loading, stiffened cylindrical shells exhibit nonlinear, non-stationary, and initial-condition-sensitive responses, which are difficult to evaluate using conventional time- or frequency-domain methods. This study investigates prototype and scaled-model tests of stiffened cylindrical shells subjected to underwater explosions and develops corresponding ALE fluid-structure interaction simulations. Based on acceleration signals, the Lyapunov exponent, Hurst exponent, Lempel-Ziv complexity, and symbolic distance are used to assess test similarity and simulation reliability. Results show good agreement in Lyapunov and Hurst exponents among different scale models, confirming statistical similarity in nonlinear dynamics. Symbolic distance decreases with increasing scale ratio, indicating stronger trajectory similarity to the prototype. Numerical simulations reproduce the stable decay behavior in the later stage but remain limited in capturing early-stage chaotic dynamics and trajectory complexity. The proposed method provides a quantitative framework for evaluating scaled-model similarity and numerical reliability under underwater explosion loading.