Employment of an acoustic camera for noise characterisation of a laboratory equipment

Exposure to noise constitutes a health risk. The present paper is related to activities performed to test emerging technologies aimed to characterise noise sources. In particular, acoustic acquisitions have been achieved on a complex laboratory equipment composed by different machines including a rotor serving as blower. Advanced noise measurement techniques based on acoustic holography and beamforming have been employed to realise a deep characterisation of the noise sources. This analysis could fix, in effective way, the possible mitigation strategies and, if extended to the other noise sources, a comprehensive management of the workplace noise exposure

Preliminary Optimization of the Sonic Boom Properties for Civil Supersonic Aircraft

In this work a simple model has been used that relates sonic boom effects to the main geometric and operative parameters of the civil supersonic aircraft. In particular, a relation between the maximum overpressure and the aircraft shape factor is employed to define an optimal preliminary design point for the supersonic civil aircraft. Carlson’s method has been widely adopted for preliminary numerical investigations of sonic boom signatures associated with different categories of supersonic aircrafts. Correlations of these numerical predictions with flight-test data have shown a reasonable agreement and confirmed the validity of the method in spite of its ease of use. Modern supersonic aircrafts are conceived to have minimum effects on people and structures through properly designed sonic boom signatures (“sine wave”- like signature is one option) and adjusting their geometry through sophisticated Computational Fluid Dynamics methods. The N-wave approach is based on simplified assumptions that do not take into account the rise time, which is one of the major factors influencing the human ear response to sonic boom and cannot be used for estimating advanced sound metrics like the perceived loudness decibel. Nevertheless, the N-wave model can be used in an early stage of the design, because it generally provides conservative estimations (upper limits) of the overpressures due to an assigned supersonic aircraft geometry, giving a rough figure of its effect on the community. Different geometries can be, therefore, easily optimized through this approach to better fix starting points for minimizing the effects of boom signatures, which are shaped subsequently through higher-order methods

Preliminary evaluation and optimization of civil aircraft sonic-boom properties through Carlson's method

In this paper a simple approach based on the Carlson's method will be presented to define a supersonic conguration optimized in terms of sonic boom properties. The Carlson's method provides a simplified procedure for the calculation of sonic boom characteristics for supersonic airplane congurations and spacecrafts. The information required for the signature predictions are: aircraft shape factor KS, aircraft operating conditions and atmospheric data. Unfortunately, there is not an analytic expression of the shape factor. Nevertheless, a graphic representing the relationship between KS and parameters related to the aircraft geometry, can be used. In this paper KS have been approximated through a linear and a quadratic interpolation as a function of other parameters and its minimization problem has been formulated. Computational results show the optimal values to be assigned to the aircraft geometry parameters in order to obtain the minimal value of the shape factor and in consequence of the sonic boom overpressure

Mistuning effects evaluation on turbomachine dynamic behaviour using genetic algorithms

This paper presents a new approach to evaluating the mistuning effects on turbomachinery blades that is classified as neither deterministic nor statistical — it is based on the employment of genetic algorithms. A genetic algorithm has been exploited to find the structurally mistuned configuration that leads to the maximum value of blade vibration amplitude for an assigned domain of variations. A test case has been fixed and subjected to an assigned forcing field; the target of the test case was to perform a smart search of the worst mistuned configuration. The test case was a twenty-blade disc on which one thousand forced frequency response analyses have been performed. A comparison with the results, based on the Monte Carlo methods, proved the suitability and the relevance of the proposed approach. The investigation has demonstrated the applicability of this new possible engineering approach to the study of systems with uncertain properties

Optimal Routing and Resource Allocation in Multi-Hop Wireless Networks

This paper addresses the problem of simultaneously optimizing power consumption and routing in multi-hop wireless networks while forcing the satisfaction of the required transmission demands between given origin-destination pairs. We devise a linear programming model for the selection of optimal routes and transmission schemes where both the power and link capacity levels are suitably discretized. Since the constraint matrix of such a model contains a huge number of columns, we propose an exact algorithm for its solution based on column-generation approach. The associated column-generation procedure is based on the solution of linear integer programming models. We report some computational results on networks with up to 65 nodes, showing the feasibility of our solution approach

Routing and Scheduling in Wireless Ad Hoc Networks

Computing capacity bounds of ad hoc networks, as well as optimizing radio resource allocation in order to approach those bounds is a hard task that have recently attracted the interest of the research community. In this paper we address the problem of jointly optimizing the routing of flows, the transmission scheduling over wireless links along the path, and the emitted power for bandwidth guaranteed traffic demands. We propose a mixed integer linear programming model which considers the signal to interference and noise ratio at receiver and accounts for the effect of adaptive transmission rate through a set of discrete link capacity and power values. To find the optimal solution of the proposed problem we provide an algorithm based on column generation. Reported numerical results on networks with up to 50 nodes and 170 links show the effectiveness of the proposed approach even with quite bit problem instances

Vibrational analysis of aerospace composite components for production defects and operating damage detection

Non-Destructive Testing of aircraft structures is of paramount relevance leading to key information regarding the structural characteristics and the residual life of a component. This paper is focused on the experimental and modeling activities related to vibrational analysis carried out on a typical aeronautical composite sample. A flap section of a regional aircraft has been studied applying the conventional tools of the modal analysis. The aeronautical component has been at first characterized in terms of natural frequencies and normal modes. Then it has been damaged using a drop tower that induced a controlled impact in the structural component. The vibrational analyses have been repeated and the normal modes in the two conditions have been compared. Then other approaches based on vibrational properties of the structures have been investigated to detect defect and damage