Abstract. Dynamic analysis of a tank containing liquid is a complex problem involving fluid-structure interaction. The tank-liquid system is simplified by an equivalent model in which the total liquid mass is divided into two zones -impulsive and convective. The paper is primary focused on the behavior of the free liquid surface (the convective portion of liquid) subjected to the dynamic loading which may result in liquid spilling or tank wall damage. Therefore, the sufficient freeboard must be required to design. The paper deals with the seismic design of the open cylindrical liquid storage tank with the aim to determine convective dynamic properties (natural frequencies and modes of oscillation), maximum vertical displacements over tank radius and overall response of the liquid to an earthquake. The analysis is performed analytically by applying procedures for the determination of convective effects based on simplified equivalent springmass model, numerically response spectrum, and method of motion integrating equations utilizing ANSYS Multiphysics.

The resulting dynamic loading on machines, the environment and humans generated by vibration and noise is dependent on the vibro-insulating components and the quality of resilient materials used in the mounting of these components. Well-designed vibration isolation of vibrating sources can effectively reduce the transmission of vibro-acoustic energy into supporting and surrounding structures. Based on frequency spectrum, the vibro-isolation efficiency of various vibro-insulating components and their resilient materials is analysed. The solution of this problem is based on theoretical knowledge and methodology of the transmission of vibration-sound waves and measurement of the machines involved. Measurements of vibration at the sources and along the path of transmission, as well as sound measurements, were performed for different vibro-isolators to compare real results with theory. Measured components include; isolation of a recirculation fan in a heating plant, air-conditioning unit, and combustion engine of a passenger vehicle. For the detection of the vibro-acoustic energy the vibration and sound were measured and FFT analysis was applied. Finally, this paper suggests measures which can be taken to reduce undesirable vibro-acoustic energy on machines, the environment and bystanders.

Transmission of vibroacoustic energy from an internal combustion engine (ICE) to its surroundings largely depends on how it is mounted, on available transmission paths and on the construction of the vehicle body and/or its surrounding structures. This is especially true in low speed engines in enclosed areas which generate perceptually weak noise, but strong low-frequency waves which energy has a negative impact on human health, comfort and driving safety especially in prolonged exposure to the source. The primary aim of the article was to analyse components of the ICE unit which had a determining impact on the reduction of low-frequency waves. Thus, the structurally transmitted noise from the ICE to its surrounding structure (body of the passenger vehicle) was analysed. The results of the vibroacoustic measurements were compared to modal analysis in order to determine possible resonance sources in the vehicle body and/or for assessing the influence of the vehicles safety gear on the generated vibroacoustic energy transfer into the cabin area of the passenger vehicle. Measurements were made for a passenger vehicle at rest and operating in its most common operational speed as well as for the stationary ICE of a cogenerate unit (CGU). Measurements and FFT analysis were used for the detection of the vibroacoustic energy sound pressure level (noise) and mechanical vibration. Firstly, the low-frequency noise sources were determined and their direct effects on the human body were investigated. Finally, this paper suggests some measures which may contribute to the reduction of undesirable vibroacoustic energy in enclosed areas.

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The paper proposes two methods for determining the quality of industrially manufactured bearings, where the vibro-acoustic energy is expressed by measuring the vibration acceleration. The determined criteria were verified and 100 % agreement was reached in determining the required quality of the bearings. Unwanted bearing noise emissions and its faults can be monitored over the maximum acceleration value determined from the time history, the frequency distribution and the r.m.s. value of the determined frequency range.