Journal of Ocean Engineering and Science最新文献

The study of internal atmospheric waves, also known as gravity waves, which are detectable inside the fluid rather than at the fluid surface, is presented in this work. We have used the time-fractional and fuzzy-fractional techniques to solve the differential equation system representing the atmospheric internal waves model. The $q$-Homotopy analysis Shehu transform technique ($q$-HAShTM) is used to solve the model. The method helps find convergent solutions since it helps solve nonlinearity, and the fractional derivative can be easily computed using the Shehu transform. Finally, the obtained solution is compared for the particular case of $\alpha =1$ with the HAM solution to explain the method’s accuracy.

In this article, non-linear time-fractional diffusion equations are considered to describe oil pollution in the water. The latest technique, fractional reduced differential transform method (FRDTM), is used to acquire approximate solutions of the time fractional-order diffusion equation and two cases of Allen–Cahn equations. The acquired results are collated with the exact solutions and other results from literature for integer-order $\alpha$, which reveal that the proposed method is effective. Hence, FRDTM can be employed to obtain solutions for different types of nonlinear fractional-order IVPs arising in engineering and science.

The loading method of the external excitations generated by the equipment directly affects the predicted result of the mechanical noise which should be the same under different excitation forms for the given equipment. In this paper, general load criteria are proposed to define forces/moments as the standard form and convert other forms of loads in the low-frequency domain. As the most typical form to characterize equipment excitation, acceleration load loading methods for different conditions are investigated. The equivalent formula between ideal accelerations and generalized forces establishes the first load criterion. The second load criterion is proposed to address the issue of an average acceleration loading, in which the phase and amplitude distribution are both absent, and cannot apply to the load identification. The upper and lower limits of the mechanical noise can be determined by the vibroacoustic transfer function of the three load models, and the energy-averaged value is used to represent the mechanical noise. Furthermore, the third criterion is used to handle the case where the acceleration load is given by the results of a bench test. According to the equipment source descriptor invariance, the conversion method is achieved between the bench test and the real ship based on the transfer function of a load model, and the mechanical noise is predicted by an equivalent energy method. Finally, a three-parameter method to quantitatively evaluate the well-fitting of experimental and numerical results, and the load criteria are well validated by underwater acoustic experiments of an experimental model.

The present study enlightens the two-dimensional analysis of the thermo-mechanical response for a micropolar double porous thermoelastic material with voids (MDPTMWV) by virtue of Eringen’s theory of nonlocal elasticity. Moore-Gibson-Thompson (MGT) heat equation is introduced to the considered model in the context of memory-dependent derivative and variable conductivity. By employing the normal mode technique, the non-dimensional coupled governing equations of motion are solved to determine the analytical expressions of the displacements, temperature, void volume fractions, microrotation vector, force stress tensors, and equilibrated stress vectors. Several two-dimensional graphs are presented to demonstrate the influence of various parameters, such as kernel functions, thermal conductivity, and nonlocality. Furthermore, different generalized thermoelasticity theories with variable conductivity are compared to visualize the variations in the distributions associated with the prior mentioned variables. Some particular cases are also discussed in the presence and absence of different parameters.

With the increase of heat transfer problems in marine vehicles and submerged power stations in oceans, the search for an efficient finned-tube heat exchanger has become particularly important. The purpose of the present investigation is to analyze and compare the thermal exchange and flow characteristics between five different fin designs, namely: a concentric circular finned-tube (CCFT), an eccentric circular finned-tube (ECFT), a perforated circular finned-tube (PCFT), a serrated circular finned-tube (SCFT), and a star-shaped finned-tube (S-SFT). The fin design and spacing impact on the thermal-flow performance of a heat exchanger was computed at Reynolds numbers varying from 4,300 to 15,000. From the numerical results, and when the fin spacing has been changed from 2 to 7 mm, an enhancement in the Colburn factor and a reduction in the friction factor and fin performances were observed for all cases under study. Three criteria were checked to select the most efficient fin design: the performance evaluation criterion P_EC, the global performance criterion G_PC, and the mass global performance criterion$M_{G_{PC}}$. Whatever the value of Reynolds number, the conventional CCFT provided the lowest performance evaluation criterion P_EC, while the SCFT gave the highest amount of P_EC. The most significant value of G_PC was reached with the ECFT; however, G_PC remained almost the same for CCFT, PCFT, SCFT, and S-SFT. In terms of the mass global performance criterion, the S-SFT provides the highest $M_{Gpc}$as compared with the full fins of CCFT (41–73% higher) and ECFT (29–54% higher). Thus, the heat exchanger with S-SFT is recommended to be used in the cooling of offshore energy systems.

This article considers time-dependent variable coefficients $(2+1)$ and $(3+1)$-dimensional extended Sakovich equation. Painlevé analysis and auto-Bäcklund transformation methods are used to examine both the considered equations. Painlevé analysis is appeared to test the integrability while an auto-Bäcklund transformation method is being presented to derive new analytic soliton solution families for both the considered equations. Two new family of exact analytical solutions are being obtained successfully for each of the considered equations. The soliton solutions in the form of rational and exponential functions are being depicted. The results are also expressed graphically to illustrate the potential and physical behaviour of both equations. Both the considered equations have applications in ocean wave theory as they depict new solitary wave soliton solutions by 3D and 2D graphs.