A multi-objective DIRECT algorithm for ship hull optimization

The paper is concerned with black-box nonlinear constrained multi-objective optimization problems. Our interest is the definition of a multi-objective deterministic partition-based algorithm. The main target of the proposed algorithm is the solution of a real ship hull optimization problem. To this purpose and in pursuit of an efficient method, we develop an hybrid algorithm by coupling a multi-objective DIRECT-type algorithm with an efficient derivative-free local algorithm. The results obtained on a set of “hard” nonlinear constrained multi-objective test problems show viability of the proposed approach. Results on a hull-form optimization of a high-speed catamaran (sailing in head waves in the North Pacific Ocean) are also presented. In order to consider a real ocean environment, stochastic sea state and speed are taken into account. The problem is formulated as a multi-objective optimization aimed at (i) the reduction of the expected value of the mean total resistance in irregular head waves, at variable speed and (ii) the increase of the ship operability, with respect to a set of motion-related constraints. We show that the hybrid method performs well also on this industrial problem

Radical Crosslinked Albumin Microspheres as Potential Drug Delivery Systems: Preparation and In Vitro Studies

The aim of this research is the preparation of acryloylated bovine serum albumin microspheres and the evaluation of their employment in drug delivery. The influence of preparation parameters on albumin microspheres and the chemicophysical properties of loaded drugs were investigated. In particular, we focused our attention on acylation albumin degree, amount of acryloylated albumin against comonomer in the polymerization step, and finally the release profile. We considered on the interaction drug-matrix, the fuctionalization degree of albumin, and the water affinity of matrix

On the use of Synchronous and Asynchronous Single-objective Deterministic Particle Swarm Optimization in Ship Design Problems

A guideline for an effective and efficient use of a deterministic variant of the Particle Swarm Optimization (PSO) algorithm is presented and discussed, assuming limited computational resources. PSO was introduced in Kennedy and Eberhart (1995) and successfully applied in many fields of engineering optimization for its ease of use. Its performance depends on three main characteristics: the number of swarm particles used, their initialization in terms of initial location and speed, and the set of coefficients defining the behavior of the swarm. Original PSO makes use of random coefficients to sustain the variety of the swarm dynamics, and requires extensive numerical campaigns to achieve statistically convergent results. Such an approach can be too expensive in industrial applications, especially when CFD simulations are used, and for this reason, efficient deterministic approaches have been developed (Campana et al. 2009). Additionally, the availability of parallel architectures has offered the opportunity to develop and compare synchronous and asynchronous implementation of PSO. The objective of present work is the identification of the most promising implementation for deterministic PSO. A parametric analysis is conducted using 60 analytical test functions and three different performance criteria, varying the number of particles, the initialization of the swarm, and the set of coefficients. The most promising PSO setup is applied to a ship design optimization problem, namely the high-speed Delft catamaran advancing in calm water at fixed speed, using a potential-flow code

Application of derivative-free multi-objective algorithms to reliability-based robust design optimization of a high-speed catamaran in real ocean environment

A reliability-based robust design optimization (RBRDO) for ship hulls is presented. A real ocean environment is considered, including stochastic sea state and speed. The optimization problem has two objectives: (a) the reduction of the expected value of the total resistance in waves and (b) the increase of the ship operability (reliability). Analysis tools include a URANS solver, uncertainty quantification methods and metamodels, developed and validated in earlier research. The design space is defined by an orthogonal four-dimensional representation of shape modifications, based on the Karhunen-Loeve expansion of free-form deformations of the original hull. The objective of the present paper is the assessment of deterministic derivative-free multi-objective optimization algorithms for the solution of the RBRDO problem, with focus on multi-objective extensions of the deterministic particle swarm optimization (DPSO) algorithm. Three evaluation metrics provide the assessment of the proximity of the solutions to a reference Pareto front and their wideness.A Reliability-Based Robust Design Optimization (RBRDO) for ship hulls is presented. A real ocean environment is considered, including stochastic sea state and speed. The optimization problem has two objectives: (a) the reduction of the expected value of the total resistance in waves and (b) the increase of the ship operability (reliability). Analysis tools include a URANS solver, uncertainty quantification methods and metamodels, developed and validated in earlier research. The design space is defined by an orthogonal four-dimensional representation of shape modifications, based on the Karhunen-Loève expansion of free-form deformations of the original hull. The objective of the present paper is the assessment of deterministic derivativefree multi-objective optimization algorithms for the solution of the RBRDO problem, with focus on multiobjective extensions of the Deterministic Particle Swarm Optimization (DPSO) algorithm. Three evaluation metrics provide the assessment of the proximity of the solutions to a reference Pareto front and their wideness

Spacetime design of aeroacoustic metacontinua through optimal response matching

The paper deals with an integrated approach to the design of a metacontinuum capable to attain a specific target response when operating in a flow. The context of the research is related to the development of a general framework for identification of the mechanical properties required by a metamaterial-based, noise-abatement device for aeronautical application. The bulk metamaterial is here represented as an unconventional continuum with peculiar constitutive equations. The propagation of an acoustic perturbation in such a continuum is governed by a generalized wave equation written here in the aeroacoustic spacetime. The spacetime metrics of the generalized D'Alembertian reveals that the acoustic perturbations propagate through a curved spacetime, whose curvature depends jointly by the metacontinuum properties and the background aerodynamic flow. The identification of the mechanical properties of the metacontinuum is achieved by matching its acoustic response with a pre-defined target using numerical optimization. A suitable measure of the distance between the acoustic responses is used as the objective function to be minimized. The problem is completed by the relevant constraints and solved numerically using a meta-heuristic algorithm. Preliminary numerical results show how the developed method can effectively identify the elasticity tensor that induces an acoustic response compatible with the target

An integrated toolchain for the design of aeroacoustic metamaterials: The H2020 project AERIALIST

The project AERIALIST (AdvancEd aicRaft-noIse-AlLeviation devIceS using meTamaterials), funded within the Breakthrough Innovation topic of the H2020 program, has closed its activity on May 2020. The objective of the project was the disclosure of the potential of metamaterials in developing disruptive devices for the mitigation of aircraft noise, in order to contribute to the identification of the breakthrough technologies targeted at the achievement of the noise reduction targets foreseen by the ACARE Flightpath 2050. Although targeted to low TRL, AERIALIST has been focused on the development of an integrated toolchain capable to address the entire design loop, from the early conception to the numerical and experimental proof of concept, up to the final design and manufacturing. The toolchain was founded onto four pillars: i) the extension of the acoustic metamaterial theory to aeroacoustics; ii) the exploitation of the latest additive manufacturing technologies; iii) the wind-tunnel assessment of the selected concepts; iv) the identification of a development roadmap towards higher TRL. After three years of activity, the project has attained all its objectives. The present paper is a review of the main outcomes of the project, their application potential and relevance to the ACARE objectives

On aeroacoustic space-time curvature for certain aerodynamic flows

The research on acoustic metamaterials is probably the most lively research field in classical mechanics since the early achievemnts dating back to 2006. One of the most intriguing and challenging aspects emerged during the last decade deals with the theoretical modeling of the acoustic meta-behavior in presence of a background aerodynamic flow. Indeed, the structure of the equations governing the propagation of an acoustic perturbation in a moving medium is substantially different, due to the effect of the convecive terms, mixing space and time derivatives through the components of the aerodynamic velocity vector field. An effective approach to cope with this aspect relies in the spacetime reinterpretation of the (aero)acoustic equations adopting the analytical tools developed within the framework of the special and general relativity. Indeed, the Minkowskian structure of the equations governing the propagtion of waves in quiescent media turns out to be Lorentzian in presence of a non-uniform background aerodynamic, with the component of the veloicity field acting as space-time-bending elements. The present paper analyses the actual structure of the aeroacoustic spacetime for certain types of flows of interest in many applications. The analysis will take advantage of the existence of analytical solutions to derive the structure of the metric tensor in closed form and make some consideration about the related Ricci's tensor an the corresponding scalar curvarture. The paper will consider potential flows around simple geometries, includig the effect of contact discontinuities (wakes), and potential vortices. The final goal of the research is a deeper understanding of the underlying structure of the acoustic spacetime for those classes of applications where the aerodynamic convections plays a key role, in order to contribute to the disclosure of breakthrough modeling approaches

Acoustic Cloaking of a Moving Object

The paper describes a theoretical and numerical approach to the modeling of an acoustic meta- material for the cloaking of an object moving within a compressible medium and impinged by an acoustic perturbation due to sources co-moving with it. The interest in the extension of the acoustic cloaking theory to objects and sources in arbitrary motion stems from the possibility to apply such a concept to the manipulation of the acoustic emissions produced by transporta- tion media. The ultimate goal is the alleviation of the acoustic impact on the community through the deep modification and/or cancellation of the intensity and directivity of the scat- tered field produced by the moving obstacle. The possible application in the aeronautical field imposes strict requirements on the mechanical properties of the acoustic metamaterial adopted, especially in terms of lightness, thus making the inertial cloaking (IC) approach an unfeasible candidate. Despite this fact, the IC is used here as a preliminary exercise to verify the possi- bility to achieve the cloaking. The generalized acoustic wave equation for the pseudo-pressure is written in a frame of reference rigidly connected to the object. The convected generalized wave equation so obtained is Laplace-transformed and then recast in an original boundary integral form. The Boundary Integral Equation formulation is suitably extended to take into account the equivalent field-source distribution needed to model the mechanical properties of the acoustic metamaterial constituting the cloak. The numerical solution of the resulting Boundary-Field Integral Equation can be obtained, at different frequencies, using a dedicated Boundary Element Method implemented into an in-house developed code. Particular atten- tion is payed to the mechanical properties of the resulting metamaterial, in order to avoid the solutions yielding totally unfeasible configurations