Abstract:
Objective The simulation and detection of ship airwake are of great significance for ensuring the safety of carrier-based aircraft operations. Traditional methods such as wind tunnel tests, real ship measurements, and computational fluid dynamics (CFD) simulations face challenges such as scale effects, high costs, and inaccurate boundary conditions. This study aims to integrate Doppler wind lidar with CFD to improve the accuracy of ship airwake simulations, providing a more reliable approach for analyzing complex flow fields affected by the atmospheric boundary layer (ABL).
Methods A CFD model based on the delayed detached eddy simulation (DDES) was established to simulate the airwake of the aircraft carrier. The computational domain was set as 1 km×3 km×0.5 km with unstructured meshes, and the hull surface was encrypted to capture flow details (Fig.1). A 1548 nm coherent Doppler wind lidar (Tab.1) was employed to obtain real-time ABL wind profiles and turbulence intensity through velocity-azimuth display (VAD) scanning, which were used as inlet boundary conditions for the CFD model (Fig.6). The lidar also conducted planar position indicator (PPI) scans at elevation angles from 0° to 10° and azimuth angles from −50° to 50° to acquire three-dimensional ship airwake data (Fig.7).
Results and Discussions The CFD simulation accurately captured the turbulence intensity distribution behind the ship island and the vertical velocity fluctuations in the wake region, with the simulated results showing good consistency with the physical phenomena of flow separation and vortex shedding (Fig.2 and Fig.3). With the detected wind profile as boundary condition for simulation, the linear fitting of the measured and simulated radial velocities yielded a slope of 1.095 and an R2 of 0.841, with the simulated radial velocity having a mean error of 0.768 m/s and a standard deviation of 0.941 m/s, verifying the accuracy of the simulation model (Fig.8). Compared with traditional CFD simulations using empirical ABL models, the integration of lidar-measured data can improve simulation accuracy.
Conclusions This paper investigates the flow characteristics of ship airwake by combining computational fluid dynamics (CFD) simulation and Doppler wind lidar, providing new means for ensuring the safety of carrier-based aircraft operations. CFD can effectively simulate the characteristics of ship airwake, and the simulation results show that obvious velocity disturbance areas exist behind the ship island and flight deck. The coherent Doppler wind lidar can detect the characteristics of the marine atmospheric boundary layer and the wake structure of the ship airwake. The lidar detection data can provide boundary conditions and simulation result verification for CFD simulation. The comparison between the measured and simulated results shows that using the wind profile of the Doppler wind lidar as the inlet boundary condition of the ship CFD model can improve the CFD model, making the simulation results closer to the real flow situation of the ship airwake. However, the 60 m distance resolution of the lidar is difficult to resolve the fine structures (such as small-scale vortices) of the ship wake flow field, and its ability to capture the transient changes of the atmospheric boundary layer under complex sea conditions is limited. In the future, it is necessary to advance from three aspects: developing a coherent Doppler wind lidar with meter-scale resolution to improve the resolution ability of wake structures; constructing a real-time inversion model of CFD-lidar; and carrying out comparative experiments under different sea conditions to establish a universal ship airwake reconstruction model.