Wave motion between two fluid-filled boreholes in an elastic medium

Santos

2003

Applied Acoustics

The boundary element method (BEM) has been used to compute the acoustic wave propagation through a single vertical panel, which separates two rooms, made of concrete, when one of the rooms is excited by a steady-state, spatially sinusoidal, harmonic line load pressure at low frequencies. This work focuses on how the connection of the panel to the ceiling affects the acoustic insulation provided by the wall. Perfect double-fixed partitions and acoustic barrier-type structures with differently-sized gaps between the ceiling and the barrier are studied. The BEM model is formulated in the frequency domain and takes the air-solid interaction fully into account. Insulation dips are localised in the frequency domain and identified with dips associated with both the wall's natural dynamic vibration modes and with those associated with the air in the rooms. The influence of the wall's thickness on acoustic insulation is also analysed. The computed results obtained with the acoustic barrier type structure are compared with those obtained by a rigid model. The importance of the rooms' surface conditions is assessed, modelling the rooms with cork. #

Section: Discussionmentioning

confidence: 99%

“…The BEM equations that are applied to this problem have already been applied by the authors to the solution of wave propagation in a fluid filled borehole [37]. The acoustic and elastic media are assumed to be homogeneous, and a perfect coupling between the solid and the fluid inside the rooms is held to exist.…”

Section: Bem Formulationmentioning

confidence: 99%

Assessing the effect of a barrier between two rooms subjected to low frequency sound using the boundary element method

Santos

2003

Applied Acoustics

“…it must be sufficiently large (Bouchon and Aki [23]). This technique is an adaptation and extension of other mathematical and numerical formulations used to solve problems such as wave propagation (Tadeu et al [24] and Godinho et al [25]). Note that Eq.…”

Section: Three-dimensional Problem Formulation and Green's Functions mentioning

confidence: 99%

Fundamental solutions for transient heat transfer by conduction and convection in an unbounded, half-space, slab and layered media in the frequency domain

Simões

Engineering Analysis with Boundary Elements

2005

Self Cite

Analytical Green's functions in the frequency domain are presented for the three-dimensional diffusion equation in an unbounded, halfspace, slab and layered media. These proposed expressions take into account the conduction and convection phenomena, assuming that the system is subjected to spatially sinusoidal harmonic heat line sources and do not require any type of discretization of the space domain. The application of time and spatial Fourier transforms along the two horizontal directions allows the solution of the three-dimensional time convection-diffusion equation for a heat point source to be obtained as a summation of one-dimensional responses. The problem is recast in the time domain by means of inverse Fourier transforms using complex frequencies in order to avoid aliasing phenomenon. Further, no restriction is placed on the source time dependence, since the static response is obtained by limiting the frequency to zero and the high frequency contribution to the response is small.The proposed functions have been verified against analytical time domain solutions, known for the case of an unbounded medium, and the Boundary Element Method solutions for the case of the half-space, slab and layered media. q

“…The authors have used a similar technique in the analysis of wave propagation inside seismic prospecting boreholes [22] and outdoor propagation of sound waves in the presence of obstacles [23].…”

Section: D Problem Formulationmentioning

confidence: 99%

Study of transient heat conduction in 2.5D domains using the boundary element method

Godinho

Engineering Analysis with Boundary Elements

Simões

2004

Self Cite

This paper presents the solution for transient heat conduction around a cylindrical irregular inclusion of infinite length, inserted in a homogeneous elastic medium and subjected to heat point sources placed at some point in the host medium. The solution is computed in the frequency domain for a wide range of frequencies and axial wavenumbers, and time series are then obtained by means of (fast) inverse Fourier transforms into space -time.The method and the expressions presented are implemented and validated by applying them to a cylindrical circular inclusion placed in an infinite homogeneous medium and subjected to a point heat source, for which the solution is calculated in closed form. The boundary elements method is then used to evaluate the temperature field generated by a point source in the presence of a cylindrical inclusion, with a non-circular cross-section, inserted in an unbounded homogeneous medium. Simulation analyses using this model are then performed to study the transient heat conduction in the vicinity of these inclusions. q