Vittorio Bovolin

Simulating fluid-structure interaction with SPH

Fluid-structure interaction (FSI) is the condition according to which a fluid comes in contact and interacts with a structure. A simple application of the impulse-momentum theorem yields as a result the developing of pressure waves, propagating inside both media. The present work presents a critical assessment of the Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH) method to simulate the first stages of a 2D fluid impacting onto a rigid vertical wall. The effects on the results in terms of the sound speed c0, appearing inside the state equation, as well as of the velocity νa of the approaching fluid are here investigated.

Simulating Flows with SPH: Recent Developments and Applications

Fluid motion is often numerically reproduced by means of grid-based methods such as Finite Difference Methods (FDMs) and Finite Elements Methods (FEMs). However, these techniques exhibit difficulties, mainly related to the presence of time-dependent boundaries, large domain deformations or mesh generation. This chapter describes a relatively recent meshfree and pure Lagrangian technique, the Smoothed Particle Hydrodynamics (SPH) method, which overcomes the above mentioned limitations. Its original frame has been developed in 1977 by (Gingold and Monaghan, 1977) and independently by (Lucy, 1977) for astrophysical applications. Since then, a number of modifications to ensure completeness and accuracy have been yielded, in order to solve the main drawbacks of the primitive form of the method. Because a calculation is based on short-range particle interactions, it is essential to limit the computational costs related to the neighbourhood definition. Available searching algorithms are then presented and discussed. Finally, some practical applications are presented, primarily concerning free surface flows. The capability to easily handle large deformations is shown.

Hydraulic modeling of flood pulses in the Middle Bussento Karst System (MBSKS), UNESCO Cilento Global Geopark, Southern Italy

Karst systems provide water for domestic and industrial uses and for generating hydropower, but they can also create fluvial hazards, such as upstream back-flooding and downstream karst flash-flood events. However, these hazards are difficult to foresee due to the complex recharge-discharge processes as well as the lack of information on the inside of the system, which has often not been completely surveyed by speleologists or explored by boreholes. To overcome these difficulties, hydro-chemical data from the monitoring system in the Middle Bussento Karst System (MBSKS), one of the first Experimental Karst Systems in southern Italy, were recorded and previously discussed. Based on shared background in flood karst hydraulic modeling, this paper describes the conceptual premises and rationale of a general-purpose hydraulic model that is suitable both for the MBSKS and for other Mediterranean, multi-recharge, mature, conduit-dominated karst systems. To test the reliability of the model, simulations of time-space behavior and response are performed using natural and artificial flood pulses “as tracers”, considering a “pulse” as a significant variation in water quantity and/or quality. The results of the model explain the interactions between allogenic, autogenic and anthropogenic recharges from differentiated sources and phreatic conduit systems. These results also clarify the overall response of karst springs at typical time scales of flood pulses.

Monitoring Activity at the Middle Bussento Karst System (Cilento Geopark, Southern Italy)

This paper deals with the results of the monitoring activities carried out in the Middle Bussento Karst System (MBSKS) during fall 2012. The MBSKS is located in the Cilento, Vallo Diano and Alburni National Park—European Geopark in the south of Italy. Results discussed in this paper are part of a larger monitoring program which has started in 2010 in an attempt to apply the European Water Directive to the protected areas. Since fall 2012, the program has been focused on the monitoring of the MBSKS. This phase has been aimed to improve knowledge of the hydro-dynamic behavior of the mature MBSKS, differentiating outputs coming from anthropogenic, autogenic and allogenic sources. During this phase two stations, located at one of the stream sink input and at the output of the system, have been used. Results obtained have confirmed some known mature karst systems behavior as such as: flushing effect, piston flow and very fast input-output response. Additional analysis has provided enough information to outline a hydraulic model of the system. Furthermore lessons learnt during this period have led to the implementation of an upgraded monitoring system that is now under completion.

Stochastic Simulation Of Solid Particle Diffusion InSlow Decaying Turbulent Flow

This paper deals with the behaviour of suspended solid particles in isotropous, homogeneous and gradually decaying turbulent flows. Kraichnans spectral description of the turbulent field is employed to investigate the influence of the particle size and mass on the Lagrangian parameters. The procedure is validated by making use of existing data on turbulent solid transport and it is shown to be a reliable as well as a reasonably cheap tool to evaluate the behaviour of suspended solid particles.