Irregular frequency elimination of three-dimensional hydroelasticity in frequency domain

2020 ◽  
Vol 196 ◽  
pp. 106817
Author(s):  
Peng Yang ◽  
Jingru Li ◽  
Dongwei Wu ◽  
Wei Zhang
Keyword(s):  
Frequency Domain ◽  
Three Dimensional ◽  
Irregular Frequency

scholarly journals Lifting restrictions on coherence loss when characterizing non-transparent hypersonic phononic crystals

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Konrad Rolle ◽  
Dmytro Yaremkevich ◽  
Alexey V. Scherbakov ◽  
Manfred Bayer ◽  
George Fytas
Keyword(s):  
Frequency Domain ◽  
Hybrid Approach ◽  
Three Dimensional ◽  
Phononic Crystals ◽  
Hybrid Technique ◽  
Detection Mechanism ◽  
Pump Probe ◽  
Fabry Perot ◽  
Multilayer Stacks ◽  
Deposition Techniques

AbstractHypersonic phononic bandgap structures confine acoustic vibrations whose wavelength is commensurate with that of light, and have been studied using either time- or frequency-domain optical spectroscopy. Pulsed pump-probe lasers are the preferred instruments for characterizing periodic multilayer stacks from common vacuum deposition techniques, but the detection mechanism requires the injected sound wave to maintain coherence during propagation. Beyond acoustic Bragg mirrors, frequency-domain studies using a tandem Fabry–Perot interferometer (TFPI) find dispersions of two- and three-dimensional phononic crystals (PnCs) even for highly disordered samples, but with the caveat that PnCs must be transparent. Here, we demonstrate a hybrid technique for overcoming the limitations that time- and frequency-domain approaches exhibit separately. Accordingly, we inject coherent phonons into a non-transparent PnC using a pulsed laser and acquire the acoustic transmission spectrum on a TFPI, where pumped appear alongside spontaneously excited (i.e. incoherent) phonons. Choosing a metallic Bragg mirror for illustration, we determine the bandgap and compare with conventional time-domain spectroscopy, finding resolution of the hybrid approach to match that of a state-of-the-art asynchronous optical sampling setup. Thus, the hybrid pump–probe technique retains key performance features of the established one and going forward will likely be preferred for disordered samples.

scholarly journals 3D Dynamic Simulation of Heat Conduction through a Building Corner Using a BEM Model in the Frequency Domain

Energies ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 4595
Author(s):  
Nuno Simões ◽  
Joana Prata ◽  
António Tadeu
Keyword(s):  
Frequency Domain ◽  
Three Dimensional ◽  
Dynamic Effect ◽  
Building Envelope ◽  
Heat Fluxes ◽  
Heat Flux Distribution ◽  
Thermal Bridge ◽  
Proposed Model ◽  
Moisture Condensation ◽  
Thermal Bridging

This paper sets out a three-dimensional (3D) boundary element method (BEM) formulation in the frequency domain to simulate heat transfer through a point thermal bridge (PTB) at a corner in a building envelope. The main purpose was to quantify the dynamic effect of a geometrical PTB in terms of distribution of temperatures and heat fluxes, which is useful for evaluating moisture condensation risk. The numerical model is first validated experimentally using a hot box to measure the dynamic heat behavior of a 3D timber building corner. The proposed model is then used to study the dynamic thermal bridging effect in the vicinity of a 3D concrete corner. Given the importance of the risk of condensation, this study looks at the influence of an insulating material and its position on the temperature and heat flux distribution through the PTB under steady state and dynamic conditions.

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