The Infrared Imaging Research For Large Ship Target On Sea

Aircraft carrier is an important tool of modern sea warfare, the infrared radiationcharacteristics of which has increasingly become an important issue related with both ofthe domestic and foreign militaries. In recent years, some scholars have already donesome research work aiming at the infrared radiation characteristics of ship target on thesea, but most of the simulation results are confined to steady-state and can’t meet thereal-time requirement of modern warfare. Furthermore, the weather condition of marineenvironment is complex and changeable, which will greatly affect the temperature fieldof the ship target. If the model doesn’t take full account of the real-time changes ofthese meteorological parameters (wind velocity, ambient temperature, temperature ofsea surface), then the simulation results will inevitably deviate the actual situation.In this paper, we construct the model of a large ship on the sea. We haveconsidered the real-time changes of external meteorological parameters. On the basis ofwhich, we obtained the non-steady-state temperature field and infrared radiation field ofthe target. Main work includes the following three parts:(1) Geometric modeling of ship target and outputing of associated data filesUsing Auto-CAD software to build a three-dimensional geometric model of thetarget ship, and import it into the ANSYS finite element software to complete theamendment and mesh division of the surface of the model. Further, we export theassociated data files and use the Monte Carlo method to calculate the angular coefficientor radiative transfer factors between the element and element, the element and sky, theelement and sea, etc.(2) Solving the unsteady-state and steady-state temperature field of ship targetSimulating radiations of the background which affect the ship target respectively,such as the solar, sky and sea. We accumulate these external heat source terms andregard it as the whole heat source term. Meanwhile, we have take account into the roleof internal heat resource, the external convective heat transfer, the thermal conductivityamong the surface elements, the multiple reflections between the surface elements andradiative heat transfer among elements. After analyzing these factors above, weestablish the energy conservation of each element. Then, we make use of the implicititerative form to solve the instantaneous unsteady temperature field of ship target.Applying this method, we can also obtain the steady-state temperature field of the shiptarget aiming at some specific time. On this basis, we put forward two kinds of methods to retrieve the transient temperature field of the ship target.(3) Infrared thermal imaging of ship targetTaking advantage of occlusion query function of OpenGL’s graphics library toconfirm the effective radiating elements of ship target, and calculate the point sourceradiance of ship target in different directions. In addition, the use of grid cutting methodhas improved the imaging mottled defect by Monte Carlo method, which can provide uswith clearly thermal image that can reflect the ship surface temperature distribution.Finally, in light of the importance of the sea background, we apply a simplifiedexperience model to simulate the infrared radiation characteristics of the sea whichtakes the first step to explore the imaging of ship target jointed with sea field of view.