This study introduces a method based on real-coded genetic algorithm to design an elliptical shaped fuel tank. This method enhances the advantage of the system such as roll stability, and reduces disadvantages like fluid c.g. height and overturning moment. These parameters corresponding to the elliptical tanks with different filling levels are properly optimized. Moreover the effects of these optimized shapes on natural sloshing frequency are investigated. Comparing presented results with experimental ones indicate the reliability and accuracy of the present work. In addition, a new method based on genetic algorithm, which enhances tank rollover threshold, is presented. This optimization enhances roll stability, although reducing the natural sloshing frequency in comparison to cylindrical tanks. In contrast, the sloshing frequency of the optimized elliptical tank is enhanced in compare with conventional elliptical tanks, which is considered as an advantageof the presented work.

The objective of this paper is representation of an analytical solution to calculate transmission loss (TL) of an arbitrarily thick cylindrically orthotropic shell, immersed in a fluid medium with a uniform external airflow and contains internal fluids. The shell is assumed to be infinitely long and is excited by an oblique plane wave. The displacements are expanded as cubic functions of the thickness coordinate to present an analytical solution based on Third-order Shear Deformation Theory (TSDT). Equations of motion of the shell are then obtained using virtual work method. By solving shell vibration as well as acoustic wave equations simultaneously, the exact solution for TL is obtained. Predictions with the presented models are compared with those of previous models (CST and FSDT) for thin shells. Similar results are achieved as the effects of shear and rotation on TL are not noticeable in a thin shell. However, the model introduced here exhibits more accurate results for thick shells where the shear and rotation effects become more significant in lower R/h ratios. Additionally, the effects of related parameters on TL such as material and geometrical properties are discussed.