Study on Scale Model Design for Wind- and Flow-Induced Drift of Maritime Targets in Tank Experiments

Accurately predicting the drift behavior of floating objects (such as fishing boats and life rafts) under complex sea conditions is of great reference value for maritime search and rescue operations. Based on the principle of dimensional analysis, this study derived a similarity criterion for scaled model tests in a laboratory wind-wave-current flume. The criterion comprehensively considers the physical dimensions and measurement limitations of the flume, the typical scales of fishing boats and life rafts in the South China Sea, and the requirements for simulating strong winds and rapid currents. Accordingly, the scale ratios of key physical parameters (such as geometric dimensions, wind speed, and current velocity) for the tests were determined. Based on this criterion, representative scaled models were designed and fabricated, including half-loaded and fully-loaded life rafts, dummies, and a fishing boat. Controlled experiments were conducted in the flume to observe the drift characteristics of these floating objects under wind-induced, current-induced, and wind-current-coupled driving conditions. The experimental results show that: ①In wind-induced drift, the drift velocity exhibits a significant linear relationship with the wind speed. The fitting equation for the half-loaded life raft is y=0.0328x+0.0508, and for the fully-loaded life raft, it is y=0.0254x−0.0189, both of which agree well with equivalent open-sea measurement data; ②In purely current-induced drift, the current drift coefficient is approximately 1; ③Under wind-current-coupled conditions, the average error between the theoretically calculated drift velocity and the experimentally measured value for the fully-loaded life raft is 4.8%, with consistent trends. Meanwhile, the drag coefficient derived from the model test results shows an error of no more than 5% compared to equivalent open-sea calculations. In summary, the scaled model test scheme established in this study successfully reproduces the main drift mechanisms of floating objects. The results for wind-induced and current-induced drift are consistent with open-sea observations, and the wind-current-coupled drift results align with theoretical predictions, validating the rationality and reliability of the derived similarity criterion and adopted scale ratios. This provides an effective method for studying the drift of maritime floating objects through physical model tests.