Numerical Analysis of Turbulent Fluid Flow and Drag Coefficient for Optimizing the AUV Hull Design

Autonomous Underwater Vehicles (AUVs) are robots able to perform tasks without human intervention (remote operators). Research and development of this class of vehicles has growing, due to the excellent characteristics of the AUVs to operate in different situations. Therefore, this study aims to analyze turbulent single fluid flow over different geometric configurations of an AUV hull, in order to obtain test geometry that generates lower drag force, which reduces the energy consumption of the vehicle, thereby increasing their autonomy during operation. In the numerical analysis was used ANSYS-CFX&#174 11.0 software, which is a powerful tool for solving problems involving fluid mechanics. Results of the velocity (vectors and streamlines), pressure distribution and drag coefficient are showed and analyzed. Optimum hull geometry was found. Lastly, a relationship between the geometric parameters analyzed and the drag coefficient was obtained.

Numerical Analysis of Heavy Oil-Water Flow and Leak Detection in Vertical Pipeline

Pipeline is a conventional, efficient and economic way for oil transportations. The use of a good system for detecting and locating leaks in pipeline contribute significantly to operational safety and cost saving in petroleum industry. This paper aims to study the heavy oil-water flow in vertical ducts including leakage. A transient numerical analysis, using the ANSYS-CFX? 11.0 commercial software is performed. The mathematical modeling considers the effect of drag and gravitational forces between the phases and turbulent flow. Mass flow rate of the phases in the leaking orifice, the pressure drop as a function of the time and the velocity distributions are presented and discussed. We can conclude that volumetric fraction of phases and fluid mixture velocity affect pressure drop and mass flow rate at the leak hole.

Oily Water Treatment by Ceramic Membrane: Modeling and Simulation

The separation process of oily water using membranes has attracted the attention of researchers and engineers. The greater problem in the use of membrane separation process is the reduction in permeate flux due to clogged pores by oil deposition inside the membrane or by the effect of the concentration polarization. For this purpose, a theoretical study of a water/oil separation module was performed. This device consists of a tubular ceramic membrane provided with a rectangular inlet section. Numerical simulations were performed using Ansys CFX software to solve the mass and momentum conservation equations in the fluid and porous domains. Here was adopted the RNG k-ε turbulence model. The effect of the membrane porosity and the inlet velocity of the fluid mixture on the two-phase flow behavior inside the separation module were evaluated. Results of the volumetric fraction, velocity and pressure fields of the oil and water phases are presented and analyzed. The results indicate a higher oil concentration within the membrane for the cases of higher porosity, and that the inlet fluid mixture velocity does not substantially affect the velocity profile within the separation module. It is found that the maximum separation efficiency of the module was obtained with feed velocity of 40 m/s and membrane porosity of 0.44.

On the Study of Autonomous Underwater Vehicles by Computational Fluid-Dynamics

Autonomous Underwater Vehicles (AUV’s) are considered as advanced classes of vehicles, capable of performing pre-established missions without physical communication with the ground or human assistance. The research and development of this type of vehicles have been motivated, due to its excellent characteristics, ideal to the military, scientific and industrial sectors. Thus, the objective of this paper is to study fluid flow behavior past over AUV’s, without and with control surfaces (rudders), by Computational Fluid-Dynamics (CFD), aiming to obtain information about the impact of the operating depth and control surfaces on the vehicle's hydrodynamics, in order to help researchers and designers of this class of vehicles. Results of the drag coefficient, pressure, velocity and streamlines distribution around the vehicles are presented and analyzed.

Numerical Study of Oil/Water Separation by Ceramic Membranes in the Presence of Turbulent Flow

Disposal of produced water during petroleum extraction causes serious environmental damage, hence the need to complete the water treatment before being disposed to environment within the criteria set established by environmental agencies in the countries. Ceramics membranes have been highlighted as a good device for separating oil/water. These act as a barrier to oil in the aqueous stream, because their essential properties for filtration, such as chemical inertness, biological stability and resistance to high temperatures. The limitation of the separation process is the decay of permeate flux during operation, due to concentration polarization and fouling. In this sense, this paper aims to evaluate numerically the feasibility of the process of separating oil/water by means of ceramic membranes in the presence of a turbulent flow induced by a tangential inlet. The results of the velocity, pressure and volumetric fraction distributions for the simulations different by varying the mass flow rate inlet and different geometric characteristics of the membrane are presented and analyzed.

Theoretical Evaluation of Two-Phase Flow in a Horizontal Duct with Leaks

The transport of oil and its derivates are done, mostly, by pipeline. The time to detect leaks has to be short for pre-venting big disasters in the nature and decreasing losses for industries. The techniques available for leak detection vary from visual inspection to the use of computational techniques such as mathematical modeling. This paper aims to study the fluid dynamics of two-phase flow (water-oil) in the pipe with leakage. The equations of the mass and momentum conservation are numerically solved by using the ANSYSCFX commercial code with the aid of a structured mesh of a horizontal pipe with three holes of leaks. The Eulerian-Eulerian model was adopted considering the oil as continuous phase and water as dispersed phase, and constant fluid properties. With profiles of pressure and volume fraction along the time in the pipe, the influence of leakage on the single-phase (oil) and two-phase (water-oil) was evaluated.

Isothermal Transport (Core-Flow Type) of Heavy and Ultraviscous Oil in Curved Pipes: A Transient Study by CFD

In the scenery of the oil industry, the remaining resources associated with light oils have an increasingly smaller share in the natural energy resources available to man, and in return the importance of resources associated with heavy oils has increased significantly. One of the drawbacks of this type of oil is associated with its low mobility due to the high viscosity in reservoir conditions, making the transport in pipelines very difficult, especially through pumping methods that require high powers. Thus, the development of new techniques and optimization of some existing technologies, aiming at the commercial use of heavy oil accumulations plays an important role. A viable technique that has been used is the core annular flow, in which small amounts of water are injected close to the pipe wall, lubricating the oil core, reducing friction and decreasing the pressure drop during the flow. In this sense, this work aims to perform, numerically, an energetic and hydrodynamic analysis of a heavy oil-water two-phase flow, using the core-flow technique, in curved pipes, in the Ansys CFX software. Results of the velocity, pressure, and volume fraction distribution of the involved phases are presented and analyzed. It was observed that the proposed mathematical model was able to accurately represent the analyzed phenomena and that a reduction factor in the pressure drop of 28.4 was obtained as compared to the heavy oil single-phase flow.

Unsteady Fluidynamic Behavior of Gas Bubbles Flowing in Curved Pipes: A Numerical Study

Petroleum is considered as one of the factors for the development of a nation as well as a cause of economic and political conflicts around the world because of the diversity of products obtained with their derivatives such as fuel for automotives and aviation, and manufacturing plastic parts, among others. The crude petroleum (usually oil, water and gas) found in an underground reservoir is transported to the surface by pipes, and has drawn the attention of researchers because of the problems generated in the pipeline with particular attention to the loss of pressure, friction and bubbles. For a fluid flow in plug regime, where many of the bubbles formed coalesce and produce bigger ones of sizes almost equal to the pipe diameter (Taylor bubble), severe instability in the flow is caused. In this context, the objective of this research has been to study the Taylor bubble flow in curved ducts using the software CFX. Results of the transient effects of the air concentration on the bubble air volumetric fraction, of the viscosity on bubble format, and pipe angle of 90? on bubble symmetry are presented and interpreted.

Thermo-Hydrodynamics of Core-Annular Flow of Water, Heavy Oil and Air Using CFX

The transport of heavy and ultra-viscous oil employing the core-flow technique has been increasing recently, because it provides a greater reduction of the pressure drop during the flow. In this context, the effect of temperature and the presence of gas on the thermo-hydrodynamics of a three-phase water-heavy oil-air flow in a horizontal pipe under the influence of gravity and drag forces, using the commercial software ANSYS CFX?, have been evaluated. The standard κ ? ε turbulence model, the mixture model for heavy oil-water system and the particle model for heavy oil-gas and water-gas systems, were adopted. Results of velocity, volume fraction, pressure and temperature fields of the phases present along the pipe are presented and discussed. It has been found that the presence of the air phase and the variation in the temperature affect the behavior of annular flow and pressure drop.

Numerical Simulation of the Shell-and-Tube Heat Exchanger:Influence of the Lower Flows and the Baffles on a Fluid Dynamics

This project proposes the numerical reproduction development of the water flow in a shell-and-tube heat exchanger 2:1 according to the CLASS C TEMA standard (for moderate operation conditions, with commercial application). With baffles in aluminum and copper tube for the cold fluid flow, the shell is in acrylic, and with thermal analysis efficiencies with regard to the presence or not of the baffles, that is to analyze the efficiency with only, the tubes and the shell and soon after the analysis with tubes and baffles. Heat exchangers are widely used equipment on an industrial and commercial scale, the application of these equipments on an industrial scale represents innovative processing solutions reflecting the processes efficiency, producing significant savings and lower cost, supporting the business success, and consequently offering opportunities, social responsibility, which are the pillars of sustainability. For the development of this work the methodology was used to calculate effectiveness, following the design parameters and contour conditions, it was analyzed the fluids behavior in the shell and the tube, through computational fluid dynamics (CFD) using the software ANSYS CFX 15.0. The results were compared with Excel generated worksheets calculated using the existing equations and correlations.