Simulation of the Internal Wave of a Subsurface Vehicle in a Two-Layer Stratified Fluid
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Simulation of the Internal Wave of a Subsurface Vehicle in a Two-Layer Stratified Fluid AKBARNEJAD BAIE Mohammad1), PIROOZNIA Mahmood2), *, and AKBARINASAB Mohammad3) 1) Department of Physical Oceanography, Science and Research Branch, Islamic Azad University, Tehran 1477893855, Iran 2) Department of Geodesy, K. N. Toosi University of Technology, Tehran 1996715433, Iran 3) Department of Physical Oceanography, University of Mazandaran, Babol 4741613534, Iran (Received June 9, 2019; revised March 26, 2020; accepted October 10, 2020) © Ocean University of China, Science Press and Springer-Verlag GmbH Germany 2020 Abstract Internal waves are one of the various phenomena that occur at sea, and they affect acoustic equipment and sea density measurement equipment. In this study, internal waves are simulated using computational fluid dynamics method in the presence of a submarine in a pre-stratified fluid. Several scenarios were implemented by Froude number changes and submersible velocity by using the Navier-Stokes k-ε turbulence model. Results indicate that the realizable k-ε turbulence model gives better results than the RNG k-ε model and the internal waves flow in this model are well represented, which increases the wavelength of the internal waves by increasing the Froude number and floating velocity, while the internal angle of the Kelvin waves is decreased. We also observe that increasing the floating velocity causes the turbulent velocity contours to increase due to the drag coefficient and its relationship with the Reynolds number. The Reynolds number increases with the increasing velocity of the float motion. The results indicate the efficiency of this method in the discovery of subsurface objects. Key words
internal waves; numerical simulation; computational fluid dynamics; turbulence models
1 Introduction Turbulent sequences are formed by distance from a submarine depending on the physics and speed of the submarine. Sea water always returns to its stratification mode due to the mass conservation law. Therefore, due to the disturbance in the submarine passage, sea water tends to return to its previous state because of the damping of the turbulent sequences of the kinematic energy into potential energy. Moreover, due to the fluid’s tendency to return to its previous state, the intersection in the density gradient, and the difference in pressure, potential energy transforms into kinetic energy, presenting as waves that are responsible for calming water. These waves are called internal waves (Sutherland et al., 2000). The factors that create the internal waves of passing an object from a prestratified zone. Spatial variations of density on the surface are gradient densities (Sutherland, 2006). In a marine environment, the pressure gradient is caused by variations in salinity or water temperature. As salinity increases and temperature decreases, the density increases due to the increase in the density of particles per unit area. Seawater stratification occurs when water with various characteristics such as salinit
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