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Mathematical Modelling of Sound Radiation from a T Junction of City Roads in Windy Conditions

Piddubniak O., Piddubniak N.

Archives of Acoustics

2016

Vol. 41, No. 3

543--558

The sound radiation from vehicles travelling on the city roads with T junction was considered. The wind effect on acoustic field was taken into account. The solution of this problem was found with the help of the integral Fourier transforms and stationary phase method as the superposition of solutions for the cases of vehicles moving along the straight roads and roads with right-angle bend. As an example, the numerical analysis of traffic noise characteristics was carried out for the T junction city road on one of streets in the town of Łódź (Poland).

Non-diffraction fringes produced by thin biprism

Liping Z., Jianghong G., Long X.

Optica Applicata

2012

Vol. 42, nr 4

699--711

Thin biprism can form non-diffraction fringes when it is illuminated by coherent plane wave and the non-diffraction fringes have long focal length and uniform intensity distribution. Geometrical optics characteristic of thin biprism is analyzed. Non-diffraction field produced by thin biprism at the Fresnel zone is deduced with exact Fresnel integral and an approximation representation is obtained by the stationary phase method. Numerical calculation is utilized to investigate the properties of non-diffraction fringes and evaluate the influence of the diffractive field caused by rectangle aperture's square edge on the fringes. An experiment is setup to observe the intensity of the non-diffraction fringes.

Sound Radiation from a Roundabout

Piddubniak O., Piddubniak N.

Archives of Acoustics

2010

Vol. 35, No. 3

437-456

Sound propagation from the vehicles moving on the city roundabout, with taking into account the wind is investigated. Solution of the problem for one moving sound source is found by means of the integral Fourier transforms extended over space variables and time. Inverse transforms are calculated approximately, using a stationary phase method and iterative technique. The solution for a general problem is obtained as a superposition of many partial solutions. The numerical analysis of noise characteristics is performed for the three-way Korfanty roundabout case in Łódz.

Generation of waves in two superposed fluids covered by an elastic plate in the presence of running stream

Dolai P.

International Journal of Applied Mechanics and Engineering

2009

Vol. 14, no 1

139-156

This paper is concerned with the problem of two-dimensional wave generation due to an initial disturbance created at the upper surface of two superposed fluid layers in the presence of uniform running streams. The upper fluid of finite height is covered by a thin elastic plate. The lower fluid of finite depth is separated from the upper one by a common interface. Assuming linear theory, the problem is formulated as a coupled initial value problem of the velocity potentials describing the motion in the two fluids. In the mathematical analysis, the Laplace and Fourier transform techniques have been utilized to obtain the elevations at the upper fluid surface and the interface in the form of infinite integrals involving the initial elevation due to plate deflection. As a special case when the initial elevation concentrated at a point on the upper surface, these integrals are evaluated asymptotically by the method of stationary phase. The asymptotic forms of the upper surface elevation and the interface elevation are depicted graphically in a number of figures. The effects of the upper fluid covered by an elastic plate and the presence of running streams on the wave motion are discussed.