ABSTRACT The bone mechanotransduction is an important phenomenon involved in many biological proc... more ABSTRACT The bone mechanotransduction is an important phenomenon involved in many biological processes in the living bone. Due to porous structure of the cortical bone, any dynamic mechanical loading causes fluid flow through the hierarchy of pores arranged in the bone units called osteons. These are distributed almost periodically and involve pores of different sizes; from the Haversian canal forming the axis of each osteon the fluid can enter the system of lacuno-canalicular porosities which drains the porous ultrastructure of the collagen apatite matrix which, thus, presents the second level of porosity. Fig. 1: The decomposi-tion of Y (a 2D scheme).
Fatigue failure of the last three stator rows vanes (S17, EGV1, and EGV2) in the 17 stage gas tur... more Fatigue failure of the last three stator rows vanes (S17, EGV1, and EGV2) in the 17 stage gas turbine axial compressor occurred in the power plant where low calorific fuel syngas, was used. Causes of this dangerous phenomenon were flow pulsations with the frequency of 380–400 Hz that were found by the experimental investigation of the duty gas turbine. Mechanism of the flow unsteadiness origin was studied with the help of flow simulations in the 2D stator cascade system. Three numerical experiments were carried out. The first experiment investigated the flow simulation in the stator cascade system with a steady undisturbed inlet flow with increased turbulence intensity. Obtained data did not meet the standards of the actual compressor operations. In the remaining two numerical experiments, a purposely designed rotor cascade was located in front of the stator cascades. Shedding of vortex structures from the cascade profile surfaces at positive incidence angles is responsible for the ...
The hydraulic analogy existing between the propagation of wavelets at the free surface flow of a ... more The hydraulic analogy existing between the propagation of wavelets at the free surface flow of a liquid and the propagation of acoustic waves in a compressible gas is used to study aerodynamics problems with phenomena at flow around solids at supersonic velocities and aeroacoustic phenomena in supersonic divergent jets. In particular, water level fluctuations, which are proportional to pressure fluctuations in the gas, are measured with an optical fiber and special measuring apparatus. Investigations are carried out on a convergent-divergent (de Laval) nozzle. This phenomenon is linked to the existence of shock-cells in supersonic jets, which are formed in the output of the nozzle. These experimental results will be compared with the results from numerical solution and will be obtained from our own program and from the commercial program CFD Fluent.
Collecting very large amount of data from experimental multiphase measurement is a common practic... more Collecting very large amount of data from experimental multiphase measurement is a common practice in almost every scientific domain. There is a great need to have specific techniques capable of extracting synthetic information, which is essential to understand and model the specific flow phenomena. The intention of developing a method for recognition of flow regime using decomposition mathematical technique comes from the fact that each regime is characterised by typical dynamic behaviour. To recognise the flow dynamic structures, means indeed the recognition of the prevalent regime moreover indicates the actual flow conditions of the monitored area. The direct approach of Proper Orthogonal Decomposition (POD) as introduced by Lumley and the Linear Stochastic Estimation (LSE) as introduced by Adrian are used to identify typical multiphase flow instability. The present approach of statistical data-analysis extends the current evaluation procedure of Electrical Impedance Tomography (...
Gas-liquid flows are omnipresent in industrial and environmental processes. Examples are the tran... more Gas-liquid flows are omnipresent in industrial and environmental processes. Examples are the transportation of petroleum products [1, 2], the cooling of nuclear reactors [3, 4], the operation of absorbers [5], distillation columns [6], gas lift pumps [7] and many mores. Different input parameters induce topologically different flow patterns with different flow character and behaviour [7, 8] . The present study concentrate to diabatic incompressible two-phase flow in horizontal pipeline with separated character [9, 10] (Ugas < 10m/s and Uliquid < 0:2m/s) such as stratified wavy flow regime including typical multiphase instability (Kelvin-elmholtz instability) [11, 12]. The Proper Orthogonal Decomposition (POD) [13], introduced by Lumpay (1967) [14] was used to extract synthetic information essential to understand and to model flow dynamics phenomena. POD in this study are used to identify flow structure in the horizontal pipeline specially under transient of separated flow regi...
ABSTRACT The bone mechanotransduction is an important phenomenon involved in many biological proc... more ABSTRACT The bone mechanotransduction is an important phenomenon involved in many biological processes in the living bone. Due to porous structure of the cortical bone, any dynamic mechanical loading causes fluid flow through the hierarchy of pores arranged in the bone units called osteons. These are distributed almost periodically and involve pores of different sizes; from the Haversian canal forming the axis of each osteon the fluid can enter the system of lacuno-canalicular porosities which drains the porous ultrastructure of the collagen apatite matrix which, thus, presents the second level of porosity. Fig. 1: The decomposi-tion of Y (a 2D scheme).
Fatigue failure of the last three stator rows vanes (S17, EGV1, and EGV2) in the 17 stage gas tur... more Fatigue failure of the last three stator rows vanes (S17, EGV1, and EGV2) in the 17 stage gas turbine axial compressor occurred in the power plant where low calorific fuel syngas, was used. Causes of this dangerous phenomenon were flow pulsations with the frequency of 380–400 Hz that were found by the experimental investigation of the duty gas turbine. Mechanism of the flow unsteadiness origin was studied with the help of flow simulations in the 2D stator cascade system. Three numerical experiments were carried out. The first experiment investigated the flow simulation in the stator cascade system with a steady undisturbed inlet flow with increased turbulence intensity. Obtained data did not meet the standards of the actual compressor operations. In the remaining two numerical experiments, a purposely designed rotor cascade was located in front of the stator cascades. Shedding of vortex structures from the cascade profile surfaces at positive incidence angles is responsible for the ...
The hydraulic analogy existing between the propagation of wavelets at the free surface flow of a ... more The hydraulic analogy existing between the propagation of wavelets at the free surface flow of a liquid and the propagation of acoustic waves in a compressible gas is used to study aerodynamics problems with phenomena at flow around solids at supersonic velocities and aeroacoustic phenomena in supersonic divergent jets. In particular, water level fluctuations, which are proportional to pressure fluctuations in the gas, are measured with an optical fiber and special measuring apparatus. Investigations are carried out on a convergent-divergent (de Laval) nozzle. This phenomenon is linked to the existence of shock-cells in supersonic jets, which are formed in the output of the nozzle. These experimental results will be compared with the results from numerical solution and will be obtained from our own program and from the commercial program CFD Fluent.
Collecting very large amount of data from experimental multiphase measurement is a common practic... more Collecting very large amount of data from experimental multiphase measurement is a common practice in almost every scientific domain. There is a great need to have specific techniques capable of extracting synthetic information, which is essential to understand and model the specific flow phenomena. The intention of developing a method for recognition of flow regime using decomposition mathematical technique comes from the fact that each regime is characterised by typical dynamic behaviour. To recognise the flow dynamic structures, means indeed the recognition of the prevalent regime moreover indicates the actual flow conditions of the monitored area. The direct approach of Proper Orthogonal Decomposition (POD) as introduced by Lumley and the Linear Stochastic Estimation (LSE) as introduced by Adrian are used to identify typical multiphase flow instability. The present approach of statistical data-analysis extends the current evaluation procedure of Electrical Impedance Tomography (...
Gas-liquid flows are omnipresent in industrial and environmental processes. Examples are the tran... more Gas-liquid flows are omnipresent in industrial and environmental processes. Examples are the transportation of petroleum products [1, 2], the cooling of nuclear reactors [3, 4], the operation of absorbers [5], distillation columns [6], gas lift pumps [7] and many mores. Different input parameters induce topologically different flow patterns with different flow character and behaviour [7, 8] . The present study concentrate to diabatic incompressible two-phase flow in horizontal pipeline with separated character [9, 10] (Ugas < 10m/s and Uliquid < 0:2m/s) such as stratified wavy flow regime including typical multiphase instability (Kelvin-elmholtz instability) [11, 12]. The Proper Orthogonal Decomposition (POD) [13], introduced by Lumpay (1967) [14] was used to extract synthetic information essential to understand and to model flow dynamics phenomena. POD in this study are used to identify flow structure in the horizontal pipeline specially under transient of separated flow regi...
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Papers by Jiri Polansky