The aim of the review is to assess the value of model experimental studies for the development of classical rotor aerodynamics as well as to describe the most significant recent results stimulated by intense development of wind power.;The aim of the review is to assess the value of model experimental studies for the development of classical rotor aerodynamics as well as to describe the most significant recent results stimulated by intense development of wind power.;The aim of the review is to assess the value of model experimental studies for the development of classical rotor aerodynamics as well as to describe the most significant recent results stimulated by intense development of wind power.

The detailed analysis of sound generation in human phonation is severely limited as the accessibility to the laryngeal flow region is highly restricted. Consequently, the physical basis of the underlying fluid–structure–acoustic interaction that describes the primary mechanism of sound production is not yet fully understood. Therefore, we propose the implementation of a hybrid acoustic PIV procedure to evaluate aeroacoustic sound generation during voice production within a synthetic larynx model. Focusing on the flow field downstream of synthetic, aerodynamically driven vocal folds, we calculated acoustic source terms based on the velocity fields obtained by time-resolved high-speed PIV applied to the mid-coronal plane. The radiation of these sources into the acoustic far field was numerically simulated and the resulting acoustic pressure was finally compared with experimental microphone measurements. We identified the tonal sound to be generated downstream in a small region close to the vocal folds. The simulation of the sound propagation underestimated the tonal components, whereas the broadband sound was well reproduced. Our results demonstrate the feasibility to locate aeroacoustic sound sources inside a synthetic larynx using a hybrid acoustic PIV approach. Although the technique employs a 2D-limited flow field, it accurately reproduces the basic characteristics of the aeroacoustic field in our larynx model. In future studies, not only the aeroacoustic mechanisms of normal phonation will be assessable, but also the sound generation of voice disorders can be investigated more profoundly.;The detailed analysis of sound generation in human phonation is severely limited as the accessibility to the laryngeal flow region is highly restricted. Consequently, the physical basis of the underlying fluid–structure–acoustic interaction that describes the primary mechanism of sound production is not yet fully understood. Therefore, we propose the implementation of a hybrid acoustic PIV procedure to evaluate aeroacoustic sound generation during voice production within a synthetic larynx model. Focusing on the flow field downstream of synthetic, aerodynamically driven vocal folds, we calculated acoustic source terms based on the velocity fields obtained by time-resolved high-speed PIV applied to the mid-coronal plane. The radiation of these sources into the acoustic far field was numerically simulated and the resulting acoustic pressure was finally compared with experimental microphone measurements. We identified the tonal sound to be generated downstream in a small region close to the vocal folds. The simulation of the sound propagation underestimated the tonal components, whereas the broadband sound was well reproduced. Our results demonstrate the feasibility to locate aeroacoustic sound sources inside a synthetic larynx using a hybrid acoustic PIV approach. Although the technique employs a 2D-limited flow field, it accurately reproduces the basic characteristics of the aeroacoustic field in our larynx model. In future studies, not only the aeroacoustic mechanisms of normal phonation will be assessable, but also the sound generation of voice disorders can be investigated more profoundly.

The object of this paper is to provide a reliable tool to carry out the parametrical studies of post-stall behaviors in multistage axial compression systems. An adapted version of the 1.5D Euler equations with additional source terms is discretized with a finite volume method and are solved in time by a fourth-order Runge–Kutta scheme. The equations are discretized at mid-span both inside the blade rows and the non-bladed regions. The source terms express the blade-flow interactions and are estimated by calculating the velocity triangles for each blade row. Additional source terms are introduced to represent the effects of inlet disturbances on post-stall behaviors and the physical analysis is therefore proposed to explain the phenomenon.;The object of this paper is to provide a reliable tool to carry out the parametrical studies of post-stall behaviors in multistage axial compression systems. An adapted version of the 1.5D Euler equations with additional source terms is discretized with a finite volume method and are solved in time by a fourth-order Runge–Kutta scheme. The equations are discretized at mid-span both inside the blade rows and the non-bladed regions. The source terms express the blade-flow interactions and are estimated by calculating the velocity triangles for each blade row. Additional source terms are introduced to represent the effects of inlet disturbances on post-stall behaviors and the physical analysis is therefore proposed to explain the phenomenon.;The object of this paper is to provide a reliable tool to carry out the parametrical studies of post-stall behaviors in multistage axial compression systems. An adapted version of the 1.5D Euler equations with additional source terms is discretized with a finite volume method and are solved in time by a fourth-order Runge–Kutta scheme. The equations are discretized at mid-span both inside the blade rows and the non-bladed regions. The source terms express the blade-flow interactions and are estimated by calculating the velocity triangles for each blade row. Additional source terms are introduced to represent the effects of inlet disturbances on post-stall behaviors and the physical analysis is therefore proposed to explain the phenomenon.

A mathematical model for calculating the distribution of temperature and the dynamics of the phase transfor-mations of water in multilayer systems on permafrost-zone surface is proposed. The model allows one to perform calculations in the annual cycle, taking into account the distribution of temperature on the surface in warm and cold seasons. A system involving four layers, a snow or land cover, a top layer of soil, a layer of thermal-insulation materi-al, and a mineral soil, is analyzed. The calculations by the model allow one to choose the optimal thickness and com-position of the layers which would ensure the stability of structures built on the permafrost-zone surface.;A mathematical model for calculating the distribution of temperature and the dynamics of the phase transfor-mations of water in multilayer systems on permafrost-zone surface is proposed. The model allows one to perform calculations in the annual cycle, taking into account the distribution of temperature on the surface in warm and cold seasons. A system involving four layers, a snow or land cover, a top layer of soil, a layer of thermal-insulation materi-al, and a mineral soil, is analyzed. The calculations by the model allow one to choose the optimal thickness and com-position of the layers which would ensure the stability of structures built on the permafrost-zone surface.;A mathematical model for calculating the distribution of temperature and the dynamics of the phase transfor-mations of water in multilayer systems on permafrost-zone surface is proposed. The model allows one to perform calculations in the annual cycle, taking into account the distribution of temperature on the surface in warm and cold seasons. A system involving four layers, a snow or land cover, a top layer of soil, a layer of thermal-insulation materi-al, and a mineral soil, is analyzed. The calculations by the model allow one to choose the optimal thickness and com-position of the layers which would ensure the stability of structures built on the permafrost-zone surface.

EXPERIMENTS IN FLUIDS
ISSN：0723-4864 volume：59 Issue：1 page：1-19
Burns, Ross A
;
Cadell, Seth R
;
Woods, Brian G
;
Bardet, Philippe M
;
André, Matthieu A

A molecular tagging velocity (MTV) technique is developed to non-intrusively measure velocity in an integral effect test (IET) facility simulating a high-temperature helium-cooled nuclear reactor in accident scenarios. In these scenarios, the velocities are expected to be low, on the order of 1 m/s or less, which forces special requirements on the MTV tracer selection. Nitrous oxide $$({\rm N}_2{\rm O})$$ ( N 2 O ) is identified as a suitable seed gas to generate NO tracers capable of probing the flow over a large range of pressure, temperature, and flow velocity. The performance of $${\rm N}_2{\rm O}$$ N 2 O -MTV is assessed in the laboratory at temperature and pressure ranging from 295 to 781 K and 1 to 3 atm. MTV signal improves with a temperature increase, but decreases with a pressure increase. Velocity precision down to 0.004 m/s is achieved with a probe time of 40 ms at ambient pressure and temperature. Measurement precision is limited by tracer diffusion, and absorption of the tag laser beam by the seed gas. Processing by cross-correlation of single-shot images with high signal-to-noise ratio reference images improves the precision by about 10% compared to traditional single-shot image correlations. The instrument is then deployed to the IET facility. Challenges associated with heat, vibrations, safety, beam delivery, and imaging are addressed in order to successfully operate this sensitive instrument in-situ. Data are presented for an isothermal depressurized conduction cooldown. Velocity profiles from MTV reveal a complex flow transient driven by buoyancy, diffusion, and instability taking place over short $$(<1\, {\rm s})$$ ( < 1 s ) and long ( $$>30$$ > 30 min) time scales at sub-meter per second speed. The precision of the in-situ results is estimated at 0.027, 0.0095, and 0.006 m/s for a probe time of 5, 15, and 35 ms, respectively.

The control simultaneous action of a jet and near-wall energy sources on the shockwave structure of a superso-nic flow in the axisymmetric and planar ducts is studied for the purpose of creating a transonic region. The regimes with an extended transonic region are obtained.;The control simultaneous action of a jet and near-wall energy sources on the shockwave structure of a superso-nic flow in the axisymmetric and planar ducts is studied for the purpose of creating a transonic region. The regimes with an extended transonic region are obtained.;The control simultaneous action of a jet and near-wall energy sources on the shockwave structure of a superso-nic flow in the axisymmetric and planar ducts is studied for the purpose of creating a transonic region. The regimes with an extended transonic region are obtained.

This article investigates the thermal performance of convective-radiative annular fins with a step reduction in local cross section (SRC). The thermal conductivity of the fin’s material is assumed to be a linear function of temperature, and heat transfer coefficient is assumed to be a power-law function of surface temperature. Moreover, nonzero convection and radiation sink temperatures are included in the mathematical model of the energy equation. The well-known differential transformation method (DTM) is used to derive the analytical solution. An exact analytical solution for a special case is derived to prove the validity of the obtained results from the DTM. The model provided here is a more realistic representation of SRC annular fins in actual engineering practices. Effects of many parameters such as conduction-convection parameters, conduction-radiation parameter and sink temperature, and also some parameters which deal with step fins such as thickness parameter and dimensionless parameter describing the position of junction in the fin on the temperature distribution of both thin and thick sections of the fin are investigated. It is believed that the obtained results will facilitate the design and performance evaluation of SRC annular fins.;This article investigates the thermal performance of convective-radiative annular fins with a step reduction in local cross section (SRC). The thermal conductivity of the fin’s material is assumed to be a linear function of temperature, and heat transfer coefficient is assumed to be a power-law function of surface temperature. Moreover, nonzero convection and radiation sink temperatures are included in the mathematical model of the energy equation. The well-known differential transformation method (DTM) is used to derive the analytical solution. An exact analytical solution for a special case is derived to prove the validity of the obtained results from the DTM. The model provided here is a more realistic representation of SRC annular fins in actual engineering practices. Effects of many parameters such as conduction-convection parameters, conduction-radiation parameter and sink temperature, and also some parameters which deal with step fins such as thickness parameter and dimensionless parameter describing the position of junction in the fin on the temperature distribution of both thin and thick sections of the fin are investigated. It is believed that the obtained results will facilitate the design and performance evaluation of SRC annular fins.;This article investigates the thermal performance of convective-radiative annular fins with a step reduction in local cross section (SRC). The thermal conductivity of the fin’s material is assumed to be a linear function of temperature, and heat transfer coefficient is assumed to be a power-law function of surface temperature. Moreover, nonzero convection and radiation sink temperatures are included in the mathematical model of the energy equation. The well-known differential transformation method (DTM) is used to derive the analytical solution. An exact analytical solution for a special case is derived to prove the validity of the obtained results from the DTM. The model provided here is a more realistic representation of SRC annular fins in actual engineering practices. Effects of many parameters such as conduction-convection parameters, conduction-radiation parameter and sink temperature, and also some parameters which deal with step fins such as thickness parameter and dimensionless parameter describing the position of junction in the fin on the temperature distribution of both thin and thick sections of the fin are investigated. It is believed that the obtained results will facilitate the design and performance evaluation of SRC annular fins.

We report velocity measurements in a vertical turbulent convection flow cell that is filled with the eutectic liquid metal alloy gallium–indium–tin by the use of local Lorentz force velocimetry (LLFV) and ultrasound Doppler velocimetry. We demonstrate the applicability of LLFV for a thermal convection flow and reproduce a linear dependence of the measured force in the range of micronewtons on the local flow velocity magnitude. Furthermore, the presented experiment is used to explore scaling laws of the global turbulent transport of heat and momentum in this low-Prandtl-number convection flow. Our results are found to be consistent with theoretical predictions and recent direct numerical simulations.;We report velocity measurements in a vertical turbulent convection flow cell that is filled with the eutectic liquid metal alloy gallium–indium–tin by the use of local Lorentz force velocimetry (LLFV) and ultrasound Doppler velocimetry. We demonstrate the applicability of LLFV for a thermal convection flow and reproduce a linear dependence of the measured force in the range of micronewtons on the local flow velocity magnitude. Furthermore, the presented experiment is used to explore scaling laws of the global turbulent transport of heat and momentum in this low-Prandtl-number convection flow. Our results are found to be consistent with theoretical predictions and recent direct numerical simulations.

Based on data obtained in the previous experimental study conducted by the authors, two approaches are proposed for analytical and numerical modeling of a critical two-phase flow in a pipe with a granular layer. An analytical approach is based on a polytrophic model, while a numerical approach was developed using a smoothed particle hydrodynamics method. A model of isenthalpic flow of vapor–water mixture in a fixed bed of solid particles is considered is this study. The mixture expansion process is considered to be polytropic. Similarly to the known problem of gas dynamics of a granular bed, an analytical relationship for calculation of a critical mass velocity was obtained. The results of the calculation based on the analytical and numerical models were compared with the experimental data and agreement between analytical and numerical data and the experiment was observed.;Based on data obtained in the previous experimental study conducted by the authors, two approaches are proposed for analytical and numerical modeling of a critical two-phase flow in a pipe with a granular layer. An analytical approach is based on a polytrophic model, while a numerical approach was developed using a smoothed particle hydrodynamics method. A model of isenthalpic flow of vapor–water mixture in a fixed bed of solid particles is considered is this study. The mixture expansion process is considered to be polytropic. Similarly to the known problem of gas dynamics of a granular bed, an analytical relationship for calculation of a critical mass velocity was obtained. The results of the calculation based on the analytical and numerical models were compared with the experimental data and agreement between analytical and numerical data and the experiment was observed.;Based on data obtained in the previous experimental study conducted by the authors, two approaches are proposed for analytical and numerical modeling of a critical two-phase flow in a pipe with a granular layer. An analytical approach is based on a polytrophic model, while a numerical approach was developed using a smoothed particle hydrodynamics method. A model of isenthalpic flow of vapor–water mixture in a fixed bed of solid particles is considered is this study. The mixture expansion process is considered to be polytropic. Similarly to the known problem of gas dynamics of a granular bed, an analytical relationship for calculation of a critical mass velocity was obtained. The results of the calculation based on the analytical and numerical models were compared with the experimental data and agreement between analytical and numerical data and the experiment was observed.