Journal of the Brazilian Society of Mechanical Sciences and Engineering

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List of Papers (Total 556)

Oil-water liquid flow rate determined from measured pressure drop and water hold-up in horizontal pipes

Stimulated by rapid progress in down-hole measuring techniques production engineers wonder whether in the near-future monitoring of oil/water production rates for horizontal wells can become possible on the basis of measured oil/water pressure losses and water hold-ups. A complicating issue is that these measured data depend on the oil and water flow patterns. The question then...

Statistical characterization of two-phase slug flow in a horizontal pipe

The present paper reports the results of an ongoing project aimed at providing statistical information on slugs in two-phase flow in a horizontal pipe. To this end, the flow was examined experimentally and numerically. On the experimental side, three non-intrusive optical techniques were combined and employed to determine the velocity field and bubble shape: particle image...

A new correlation for single and two-phase flow pressure drop in round tubes with twisted-tape inserts

Twisted-tape inserts are frequently used in heat exchangers as a passive and inexpensive heat transfer enhancement method. However, their use results not only heat transfer coefficient increments, but also pressure drop penalties. The present study analyses the literature on single and two-phase frictional pressure drop inside tubes with twisted-tape inserts focusing on the...

Experimental investigation of horizontal gas-liquid slug flow by means of wire-mesh sensor

The monitoring and visualization of two-phase flow is of great importance either from technical/practical point of view for process control and supervision or from scientific/theoretical point of view, for the understanding of physical phenomenon. A wire-mesh sensor was applied to experimentally investigate two-phase horizontal pipe flow. Furthermore, some physical flow...

Film fraction in a vertical circular Venturi scrubber

The liquid film affects significantly the Venturi scrubber efficiency. Film fraction was measured in a vertically mounted laboratory scale Venturi scrubber with a 0.020 m throat diameter. The liquid was injected at the throat by one to six 0.001 m holes. The throat gas velocity varied from 50 to 90 m/s and the relative jet penetration varied between 0.05 and 0.85. A special test...

Comparison between experimental data and numerical modeling for the natural circulation phenomenon

The study of natural circulation phenomenon has been object of crescent interest in scientific community in recent years. The new generation of compact nuclear reactors uses natural circulation of the fluid as a residual heat removal cooling system in case of accident or shutdown. The objective of this paper is to present a comparison between experimental data and numerical...

Boiling of R-134a in horizontal mini tube

This work presents the results of an experimental study carried out with R-134a to characterize heat transfer and pressure drop during flow boiling in a horizontal smooth tube of 2.6 mm ID. The experimental tests included (i) heat fluxes in the range from 10 to 100 kW/m2, (ii) the refrigerant mass velocities set to discrete values in the range of 240-930 kg/m2s and (iii...

Generation of stationary Gaussian processes and extreme value distributions for high-cycle fatigue models - application to tidal stream Turbines

The operating environment of tidal stream turbines is random due to the variability of the sea flow (turbulence, wake, tide, streams, among others). This yields complex time-varying random loadings, making it necessary to deal with high cycle multiaxial fatigue when designing such structures. It is thus required to apprehend extreme value distributions of stress states, assuming...

Construction of Lyapunov functions for the estimation of basins of attraction

Technical systems are often modeled through systems of differential equations in which the parameters and initial conditions are subject to uncertainties. Usually, special solutions of the differential equations like equilibrium positions and periodic orbits are of importance and frequently the corresponding equations are only set up with the intent to describe the behavior in...

Influence of physical and geometrical system parameters uncertainties on the nonlinear oscillations of cylindrical shells

This work investigates the influence of physical and geometrical system parameters uncertainties and excitation noise on the nonlinear vibrations and stability of simply-supported cylindrical shells. These parameters are composed of both deterministic and random terms. Donnell's non-linear shallow shell theory is used to study the non-linear vibrations of the shell. To discretize...

Dynamics of rotating non-linear thin-walled composite beams: analysis of modeling uncertainties

In this article a non-linear model for dynamic analysis of rotating thin-walled composite beams is introduced. The theory is deduced in the context of classic variational principles and the finite element method is employed to discretize and furnish a numerical approximation to the motion equations. The model considers shear flexibility as well as non-linear inertial terms...

Loudness scattering due to vibro-acoustic model variability

The use of numerical simulation in the design and evaluation of products performance is ever increasing. To a greater extent, such estimates are needed in a early design stage, when physical prototypes are not available. When dealing with vibro-acoustic models, known to be computationally expensive, a question remains, which is related to the accuracy of such models in view of...

Control of uncertainties within an interdisciplinary design approach of a robust high heel

Within this paper the combination of several methods, developed and used in Collaborative Research Center (CRC) 805 - "Control of Uncertainties in Load Carrying Systems in Mechanical Engineering" of the DFG (German Research Foundation), is used to demonstrate the development of a load carrying system under uncertainty. The development starts with the identification of relevant...

The fundamental elements in certain inverse acoustic problems: their roles and interactions

Acoustic holography and holophony, wave field synthesis and active noise control are based on common elements which are causality, model, objective, and regularization. In the frequency domain (putting causality aside), a simple formulation states the influence - not the interaction - of errors of the model and objective and of regularization of the results. However, it does not...

Stochastic modeling of flexible rotors

Flexible rotors are characterized by inherent uncertainties affecting the parameters that influence the dynamic responses of the system. In this context, the handling of variability in rotor dynamics is a natural and necessary extension of the modeling capability of the existing techniques of deterministic analysis. Among the various methods used to model uncertainties, the...

Influence of a diagonal pre-drilled hole on hole quality during the reaming process using multiblade tools

The requirements of production engineering for a precision hole are to ensure the required quality as well as minimal production costs. The interactions between machine, tool and the pre-drilled hole result in uncertainties during the final reaming process. For this purpose the reaming process itself and the appearance of process faults were focused in a large number of...

Modeling random corrosion processes via polynomial chaos expansion

Polynomial Chaos Expansion (PCE) is widely recognized as a flexible tool to represent different types of random variables/processes. However, applications to real, experimental data are still limited. In this article, PCE is used to represent the random time-evolution of metal corrosion growth in marine environments. The PCE coefficients are determined in order to represent data...

Effect of parametric uncertainties on the performance of a piezoelectric energy harvesting device

The use of piezoelectric materials for the development of electromechanical devices for the harvesting or scavenging of ambient vibrations has been extensively studied over the last decade. The energy conversion from mechanical (vibratory) to electrical energy is provided by the electromechanical coupling between mechanical strains/stresses and electric charges/voltages in the...

Aeroelastic stability analysis using linear matrix inequalities

The present work describes an alternative methodology for identification of aeroelastic stability in a range of varying parameters. Analysis is performed in time domain based on Lyapunov stability and solved by convex optimization algorithms. The theory is outlined and simulations are carried out on a benchmark system to illustrate the method. The classical methodology with the...

Control of strain in a flexible beam using Ni-Ti-Cu shape memory alloy wire actuators

In this paper the development of an experimental test bench to analyze and control the strain of a flexible aluminum beam subjected to external disturbances is described. In the proposed platform, strain-gauges are used to measure the strain of the beam in a single cantilever mode while Ni-Ti-Cu Shape Memory Alloy (SMA) wires are used as force actuators. Data acquisition and...

Nonlinear dynamics of a SMA large-scale space structure

Large-scale structures are of special interest of aerospace applications, especially the ones involving smart materials. This paper deals with an archetypal system with two degrees of freedom that resembles the use of SMA elements as vibration isolation systems on a sparse aperture satellite array. The system has SMA elements in two perpendicular directions connected to a mass...

Architecture of a remote impedance-based structural health monitoring system for aircraft applications

The essence of structural health monitoring (SHM) is to develop systems based on nondestructive inspection (NDI) technologies for continuous monitoring, inspection and detection of structural damages. A new architecture of a remote SHM system based on Electromechanical Impedance (EMI) measures is described in the present contribution. The proposed environment is employed to...

System identification and active vibration control of a flexible structure

The aim of this paper is to illustrate the active control of vibration of a flexible structure using a model-based digital controller. The state-space model of the system is derived using a system identification technique known as the Observer/Kalman Filter Identification (OKID) method together with Eigensystem Realization Algorithm (ERA). Based on the measured response of the...