1,721,178 research outputs found
Studio della Fluidodinamica Interna di Ugelli Propulsivi di Tipo Dual Bell
No full textFilippo Sabetta, Maurizio Di Giacinto, Franco Rispol
Entrained flow gasification of biomass. Part B: plant configurations and co-gasification with coal
No full textNumerical Optimization of Combined Heat and Power Organic Rankine Cycles - Part B: simultaneous design & part-load optimization
Full text linkNon-linear perturbation response of methane-air global and detailed kinetics in premixed reactors
No full textPGS-COM: A hybrid method for non-smooth black-box constrained optimization problems
No full textIn the areas of chemical processes and energy systems, the relevance of black-box optimization problems is growing because they arise not only in the optimization of processes with modular/sequential simulation codes but also when decomposing complex optimization problems into bilevel programs. The objective function is typically discontinuous, non-differentiable, not defined in some points, noisy, and subject to linear and nonlinear relaxable and unrelaxable constraints. In this work, after briefly reviewing the main available direct-search methods applicable to this class of problems, we propose a new hybrid algorithm, referred to as PGS-COM, which combines the positive features of Constrained Particle Swarm, Generating Set Search, and Complex. The remarkable performance of PGS-COM is assessed and compared with that of eleven main alternative methods on twenty five test problems as well as two challenging process engineering applications related to the optimization of a heat recovery steam cycle and a styrene production process
Unsteadiness characterisation of shock wave/turbulent boundary-layer interaction at moderate Reynolds number
Full text linkA direct numerical simulation of an oblique shock wave impinging on a
turbulent boundary layer at Mach number 2.28 is carried out at moderate
Reynolds number, simulating flow conditions similar to those of the experiment
by Dupont et al. (2006). The low-frequency shock unsteadiness, whose
characteristics have been the focus of considerable research efforts, is here
investigated via the Morlet wavelet transform. Owing to its compact support in
both physical and Fourier spaces, the wavelet transformation makes it possible
to track the time evolution of the various scales of the wall-pressure
fluctuations. This property also makes it possible to define a local
intermittency measure, representing a frequency-dependent flatness factor, to
pinpoint the bursts of energy that characterise the shock intermittency scale
by scale. As a major result, wavelet decomposition shows that the broadband
shock movement is actually the result of a collection of sparse events in time,
each characterised by its own temporal scale. This feature is hidden by the
classical Fourier analysis, which can only show the time-averaged behaviour.
Then, we propose a procedure to process any relevant time series, such as the
time history of the wall-pressure or that of the separation bubble extent, in
which we use a condition based on the local intermittency measure to filter out
the turbulent content in the proximity of the shock foot and to isolate only
the intermittent component of the signal. In addition, wavelet analysis reveals
the intermittent behaviour also of the breathing motion of the recirculation
bubble behind the reflected shock, and allows us to detect a direct, partial
correspondence between the most significant intermittent events of the
separation region and those of the wall-pressure at the foot of the shock
Numerical study of transition between the two operating modes of dual bell nozzles, AIAA Paper 2002-3989
No full textEffect of Wall Shape and Real Gas Properties on Dual Bell Nozzle Flowfield, AIAA Paper 2005-3943
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