| As the top superstructure of warships, mast is the essential radar scattering source of a warship. Therefore, stealth design for masts can effectively improve the stealth performance of the ship. In modern ship designs, because of the small radar scattering cross section area and good stealth effects, enclosed cylindrical masts are widely used. As an important platform which installs radar and other electronic equipment, it is inevitable that there will be a big amount of protruding structure on the surface of a mast, and the masts are generally large scaled structures, which brings many difficulties to radar scattering calculations. In previous mast designs, truss structures are usually applied, and wind loads have small effects to the mast structure. With the widespread use of enclosed masts in modern warship designs and constructions, the effects of wind loads have become more and more important. It is necessary to study the wind pressure distribution of enclosed masts through wind tunnel experiments.First, on the basis of massive reading of related papers and articles, the research development status of stealth masts and its significance to overall ship stealth, target scattering characteristics were briefly introduced, including electromagnetic characteristics and target RCS calculation methods. Graphical Electromagnetic Computing (GRECO) was elected as the RCS calculation method after comparative analysis. Basic principles of GRECO method were studied; calculation formulas of GRECO were derived and compiled. After comparison of relevant examples, defects of the method were analyzed and improved correspondingly. Then the metal coating radar absorbing material (RAM) scattering calculations and multiple scattering calculations were introduced into improved GRECO, and a visual calculation method that is applicable for metal coating radar absorbing materials was obtained.Then, take certain mast as an example, the model of the mast was divided into several groups, radar scattering of each group was calculated, main scattering source was analyzed. Targeted stealth modifications of the mast were carried out. After the modifications, RCS of the mast was recalculated and analyzed. The results showed that the feature values of RCS of the mast have satisfied design requirements, but the peak values in several angles were large. Then, the structure was modified in accordance with the problems. After the third time of RCS calculation of the mast, the results showed that feature values of RCS satisfied design requirements, peak values were reduced significantly. Due to various reasons, stealth performance of RAM coated mast was not analyzed here.Finally, wind load experiment was applied to a1:15model of the stealth improved mast, the experiment was conducted relying on wind tunnel laboratory in Dalian University of Technology, wind speed was15m/s, wind angle range was0°～360°, surface load pressure data of mast under five conditions were obtained. After the experiment, preliminary analysis of the data was conducted, stability of the data was checked, and dubious data was excluded; comparative analysis of the data under each conditions were carried out, it was discovered that wind pressure values under condition4and5have little differences compared with condition1, this is because the posture under these conditions were ship leaning forward and back10°, respectively, which is similar to the horizontal posture under condition1; wind pressure data of first three conditions were compared at last, wind pressure data and wind angles with greatest threat to each component of the mast was searched, which provides data support to possible follow-up strength analysis of the mast. |
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