RANS Simulation for the Maneuvering and Control of a Suboff Submarine Model

Submarine maneuverability has been analyzed by means of computational fluid dynamics(CFD).This approach provides an alternative,accurate,and cost-effective method for simulating actual flow.The numerical results show that the numerical simulation of the viscous flow related to a moving submarine based on the RANS equation with a relevant turbulence model can not only provide rich flow field details such as flow separation,but also accurately predict its hydrodynamic performance.The present study indicates that CFD can be used to forecast the submarine’s maneuverability in the initial design stage.The present results will be used in the future as a basis for analyzing methods to reduce the vibration and noise generated by the submarine.

Effect of the yaw angle on turbulent flow structures around the submarine model

The objective of this paper is to investigate the turbulent flow structures around the submarine model and evaluate the effect of the yaw angle on the turbulent flow characteristics.The large eddy simulation based on the boundary data immersion method is used to investigate.The computational domain consists of 1.2×10^(8)uniformly distributed Cartesian orthogonal grid nodes to capture the basic flow characteristics around the model.The pressure coefficient,friction coefficient and wake velocity distribution are in good agreement with the experimental data.Three different types of vortex structures were mainly captured around the model,including horseshoe vortex,sail tip vortex and crossflow separation vortex.With the increase of the yaw angle,the asymmetry of the horseshoe vortex and the tip vortex gradually increases,and the vortex strength of the vortex leg on the windward of the horseshoe vortex and the vortex strength of the tip vortex also increase gradually.For the crossflow separation vortex,the flow separation zone gradually expands and migrates downstream with the increase of the yaw angle.

NUMERICAL SIMULATION OF VISCOUS FLOW AROUND AN APPENDED SUBMARINE MODEL

A multizone/multiblock coupled RANS equation solver is presented to numerically simulate the viscous flow around an appended submarine model at Reynolds number 1. E7. k-ε two equation turbulenc model together with wall function are used. The resulting finite difference equations are solved by SIMPLEC, ADI. The technique of rising up the bottom surface is presented to overcome radial contraction problem in Cartesian coordinate system. Benchmark numerical calculations have been compared with experimental data, the radial distribution of axial velocity on the propeller disk plane is 4. 63%.

Application of Tube-Packaged FBG Strain Sensor in Vibration Experi ment of Submarine Pipeline Model

Optical fiber sensors have received increasing attention in the fields of aeronautic and civil engineering for their superior ability to stand explosion, immunity to electromagnetic interference and high accuracy, especially fit for measureroent applications in harsh environment. In this study, a novel FBG （fiber Bragg grating） strain sensor, which is packaged in a 1.2 mm stainless steel tube with epoxy resin, is developed. Experiments are conducted on the universal material testing machine to calibrate its strain transferring characteristics. The sensor has the advantages of small size, high precision and flexible use, and exhibits promising potentials. Five tube-packaged strain FBG sensors have been applied to the vibration experiment of a submarine pipeline model. The strain measttred with the FBG sensor agrees well with that measttred with the electric resistance strain sensor.

Submarine fans： A critical retrospective (1950-2015)

When we look back the contributions on submarine fans during the past 65 years （1950 -2015）, the empirical data on 21 modern submarine fans and I0 ancient deep-water sys- tems, published by the results of the First COMFAN （Committee on FANs） Meeting （Bouma eta｜., 1985a）, have remained the single most significant compilation of data on submarine fans. The 1970s were the ＂heyday＂ of submarine fan models. In the 21st century, the general focus has shifted from submarine fans to submarine mass movements, internal waves and tides, and contourites. The purpose of this review is to illustrate the complexity of issues surrounding the origin and classification of submarine fans. The principal ele- ments of submarine fans, composed of canyons, channels, and lobes, are discussed using nine modern case studies from the Mediterranean Sea, the Equatorial Atlantic, the Gulf of Mexico, the North Pacific, the NE Indian Ocean （Bay of Bengal）, and the East Sea （Korea）. The Annot Sandstone （Eocene-Oligocene）, exposed at Peira-Cava area, SE France, which served as the type locality for the ＂Bouma Sequence＂, was reexamined. The field details are documented in questioning the validity of the model, which was the basis for the turbidite- fan link. The 29 fan-related models that are of conceptual significance, developed during the period 1970-2015, are discussed using modem and ancient systems. They are： （I） the classic submarine fan model with attached lobes, （2） the detached-lobe model, （3） the channel-levee complex without lobes, （4） the delta-fed ramp model, （5） the gully-lobe model, （6） the suprafan lobe model, （7） the depositional lobe model, （8） the fan lobe model, （9） the ponded lobe model, （I0） the nine models based on grain size and sediment source, （11） the four fan models based on tectonic settings, （12） the Jackfork debrite model, （13） the basin-floor fan model, （14） supercritical and subcritical fans, and （15） the three types of fan reservoirs. Each model is unique, and the long-standing belief that submarine fans are composed of turbidites, in particular, of gravelly and sandy high-density turbi- dites, is a myth. This is because there are no empirical data to validate the existence of gravelly and sandy high-density turbidity currents in the modern marine environments. Also, there are no experimental documentation of true turbidity currents that can trans- port gravels and coarse sands in turbulent suspension. Mass-transport processes, which include slides, slumps, and debris flows （but not turbidity currenrs）, are the most viable mechanisms for transporting gravels and sands into the deep sea. The prevailing notion that submarine fans develop during periods of sea-level lowstands is also a myth. The geologic reality is that frequent short-term events that last for only a few minutes to several hours or days （e.g., earthquakes, meteorite impacts, tsunamis, tropical cyclones, etc.） are more important in controlling deposition of deep-water sands than sporadic long- term events that last for thousands to millions of years （e.g., lowstand systems tract）. Submarine fans are still in a stage of muddled turbidite paradigm because the concept of high-density turbidity currents is incommensurable.