Michele Mossa | Politecnico di Bari (original) (raw)

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Papers by Michele Mossa

The slug flow is the most frequent multiphase flow occurring into a flexible marine riser used by... more The slug flow is the most frequent multiphase flow occurring into a flexible marine riser used by the petroleum industry in offshore environments and it is featured by the presence of both a liquid and a gaseous phase. This work describes a simple model of the slug flow regime by means of an equivalent monophase compressible flow modelling. A main topic related to the risers issue in presence of multiphase flow regimes involving the presence of petroleum is the probability of a potential breaking of the pipe itself with consequent outfall of the inner fluid into the outer marine environment. In presence of waves and currents directed toward a coastline it would be possible the spreading and increasing of the pollutants concentration in very sensitive areas bringing imbalance to the coastal environment. The slug regime in this work is modelled as a monophase compressible flow having a steady behaviour during its rising toward the top end motion of the riser starting from the bottom one and characterized by adiabatic processes and energy losses along the entire length of the pipe. The main equations characterizing the motion of the flow in a curved pipe will be described together with the derivation of the forces acting upon the its inner surface wall. The last ones were implemented in a MATLAB code to obtain the behaviour of a flexible marine riser as a free hanging catenary initial configuration to investigate the dynamic stresses the riser being undergone. The results may be useful to a correct design of this kind of pipe in order to avoid their breaking in an offshore environment.

International Journal of Remote Sensing, 2013

J Hydraul Res, 2004

This paper presents experimental results of a turbulent non-buoyant jet vertically discharged in ... more This paper presents experimental results of a turbulent non-buoyant jet vertically discharged in a stagnant ambient and of the same jet discharged in a flow field of regular waves. The study was carried out in a wave channel and jet velocities were measured with a backscatter four-beam two-component fiber-optic LDA system. The signal of the two velocity components was sampled simultaneously to that of a resistance probe of the water surface profile in wave field configurations. This transducer was placed in the transversal section of the channel crossing the measurement point of the LDA system. The present study also includes a comparative investigation of the main fluid mechanics characteristics in cases of jet discharged in a stagnant ambient, and the same jet discharged in flow fields of regular waves characterized by different periods. Analysis of these characteristics underlines the substantial differences between the two cases under study.

Journal of Hydraulic Engineering, Jul 1, 2004

This paper presents experimental results of a turbulent neutrally buoyant jet vertically discharg... more This paper presents experimental results of a turbulent neutrally buoyant jet vertically discharged in a stagnant ambient and of the same jet discharged in a flow field of regular waves, in the intermediate range between deep and shallow water. A number of such studies have been performed on this configuration in the past, but mostly limited to concentration ͑dilution͒ measurements. Thus one could argue the need for a detailed analysis of this problem with modern instrumentation. This paper will address the deficiency and will present the results of a new experimental study into wave-induced mixing. Velocity jet components were measured with a backscatter, twocomponent four-beam laser Doppler anemometer system. For the cases of jets with waves, ensemble-averaged velocities were obtained by phase averaging the measured signals separated by the wave period over about 500 waves. The main results of the present study indicate the following: ͑1͒ the entrained flow is higher in the case of jet with waves; ͑2͒ oscillating velocity components cannot be described by classic wave motion theories; ͑3͒ comparison of the root-mean square of turbulent velocity components indicates the effect of wave presence; ͑4͒ in the case of jet-wave interaction, the reduction of the jet momentum shown in literature can be explained by the presence of the turbulent Reynolds normal stresses ͑which are not as small as in the case of stagnant ambient and, consequently, cannot be ignored͒ and the wave Reynolds normal stresses; and ͑5͒ the analysis of the wave Reynolds shear stresses shows that it is not always right to apply a wave motion theory to obtain the statistical contribution of the wave field; a conclusion particularly interesting in order to enable the improvement of mathematical models present in literature.

Journal of Hydraulic Research, 2007

In this paper, the historic floods in the city of Bari, Italy, are analyzed and compared to the r... more In this paper, the historic floods in the city of Bari, Italy, are analyzed and compared to the recent flood of October 2005. The objective is to point out the role of anthropogenic action and poor planning in the amplification of territory risks. The studied zone is highly permeable and is characterized by a drainage network which is not always defined. It is constructed of numerous natural incisions which, locally, are called "lame". The main hydraulic characteristics of floods are described evidencing the effect of ungovernable and chaotic anthropogenic impact, that, being united with incorrect planning, result in catastrophic events. A high level of attention must always be given to the protection of the territory in order to avoid high risk situations. Once hydraulic operations are carried out they must be maintained in order to continue their efficiency which cannot be put to risk by poor territorial planning.

Environmental Fluid Mechanics, 2015

Journal of Hydraulic Research