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This paper presents temperature estimations via two simple CFD simulations of a dynamic phenomenon in a transparent tank (cylindrical heater rod submerged into water in a glass tank) with ANSYS Fluent and comparison with the optical measurement results obtained via the Digital Holographic Interferometry (DHI) method and thermocouples. Our CFD simulations predict temperature values in good agreement (within 5% error limit) compared to thermocouples and DHI. Furthermore, the great advantages of DHI technique for such kind of reliable, fast, in time, accurate and contactless measurements were highlighted. Data validations of our simulations could lead to further investigations through the CFD simulating technique for a wide range of applications.

This paper deals with the demonstration measurement of the vector field flowing around a general irregular body using Particle Image Velocimetry (PIV). In the case of flow around complex bodies, problems arise due to the fact that the generated single laser sheet does not cover the entire surroundings of the body and the body itself shields the laser. A simple solution has been chosen, and that is the gradual repositioning of the laser optics, recording data from individual positions step-by-step, and subsequent merging of the vector fields. The measurement and evaluation workflow is described. The averaged velocity data are presented. The overlapping areas of each field are presented in graphs and as vector maps individually and merged. The problematic circumstances of the chosen approach are described, and their solution is proposed. The chosen principle is functional. However, care must be taken to observe the current conditions between measurements of individual areas.

This paper describes an investigation of thermo-convective structures called Rayleigh-Bénard-Poiseuille (RBP) convection in a wide rectangular water channel formed above a heated bottom-wall. The phenomenon was investigated experimentally using planar Particle Image Velocimetry (PIV) for velocity vector field data and 2-color Laser-Induced Fluorescence (LIF) for temperature scalar field data. The PIV and LIF records were taken simultaneously on three cameras (one for PIV and two for LIF) in the central vertical plane of the channel in order to detect the secondary flow caused by the natural convection. The result is the combined temperature and velocity data used to evaluate the onset point of the secondary flow. The manifestation of this phenomenon on both velocity and temperature fields is described. The LIF method was confirmed to give more satisfactory results because the PIV method is generally less suitable for lower velocity measurement in boundary layers, both because of adverse reflections and because of the limitation for measuring very low velocities near walls. The measured data were compared with theoretical dependencies and with the literature data. Other limitations of the measurement were described, and steps for its improvement were suggested. In the present setup, temperature influence by the laser or wall accumulation was observed, which needs to be investigated more thoroughly and eliminated in future work.

Bylo testováno mnoho typů mikrokapilár, čtvercových, kulatých a různých velikostí vnitřního průměru, ve kterých byla vytvořena kavitační bublina. Účelem těchto experimentů bylo sledovat rychlost rázové vlny těsně po počáteční kavitační bublině a odrazové vlny uvnitř i vně mikrokapilár. Hlavní metodou byla jiskra indukovaného limitu přehřátí kapaliny. Zde jsme použili metodu rozbití indukovanou laserem (LIB). Bylo popsáno nastavení kavitace, které ovlivňuje stabilitu a velikost bubliny. Pro snímání bublinek kavitace a rázové vlny jsme použili radiografické nastavení s kamerou. Byl pozorován časový vývoj rychlosti rázové vlny; rychlost počáteční rázové vlny uvnitř mikrokapiláry byla vyšší než rychlost rázu mimo mikrokapiláru.

This paper describes the preliminary measurements of the temperature field in water channel by the Planar Laser-Induced Fluorescence (pLIF) method in the one-colour mode using commercial LaVision system. The aim of the work is to find suitable parameters of the experiment (concentration of fluorescent dye, laser power, arrangement of the experiment, etc.) for measuring the temperature field in a closed glass channel of rectangular cross-section with a heated bottom-wall and to verify an applicability of this method in general. The intention is to carry out measurements in the transverse plane of the duct such that the specific thermos-convective structures of the Rayleigh-Bénard-Poiseuille convection, i.e. mixed convection, are detected. For simplicity, the initial measurements were performed in the natural convection regime, i.e. the water in the channel was not driven by the circulation pump. In this case, a larger temperature gradient was created near the wall compared to the force convection case when a cold liquid flows continuously into the experimental area. The presented work serves as a methodological guide for future measurements and provides valuable experience for the design of a new channel for investigation of the thermal flow instabilities.

In this article, a literature survey of the experimental channels used for investigation of a non-isothermal flow is presented. Particular interest is focused on the flow stability with a heated wall by a uniform heat flux. The aim of this work is to prepare a comprehensive overview of the technical design and experimental settings used in previous studies. Collected information shall help to design and manufacture new horizontal channel with a rectangular cross-section with a width of around 200 mm and a height of 20 mm. The channel will be equipped with a constant heat flux section on a bottom wall for investigation of the vortex structures and the flow instabilities using modern optical methods. The channel will operate with liquid (most probably water) in the range of low Reynolds numbers. Parallel laminar flow with Poiseuille velocity profile at the inlet of a heated section and a uniform heat flux predefine the essential requirements on the channel design.

The paper describes the development of a non-invasive flowmeter for lower flow rates and its first tests. This gauge is physically based on the interaction of fluid flow with an ultrasonic signal that passes through the fluid from the transmitter to the receiver. Ultrasonic flowmeters are currently relatively commonly used gauges, whose advantages such as non-invasiveness (i.e. zero pressure losses) and the ability to seamlessly measure the flow rates of any (for example opaque) liquids, without contact with the liquid, are widely known. However, there are still parts of the ultrasonic flowmeter measurement chain that are undergoing research and development. It can be signal processing itself (mainly), its design solution, measurement for different flow cases (measurement in a flow field with a uniform velocity profile, in a flow field with an axisymmetric velocity profile, in a flow field with a general velocity profile), validation of the applied signal processing approaches, evaluation of uncertainties. The flowmeter itself, which development is described in the paper, will be used for trouble-free measurement in air engineering, but also serves as a training device for building a more complex ultrasonic gauge. Therefore, this flowmeter contains more signal transmitters and receivers than it is usual and all transmitter-receiver combinations are captured during the measurement. This gauge is called ultrasonic tomograph and its principle is also outlined in the paper. Here, so far, without a reconstructed vector field.

The dynamic behaviour of cavitation bubble close to a flexible boundary is investigated experimentally. The cavitation bubble is produced as a consequence of an optical breakdown generated by the focus of 532 nm Nd-Yag laser beam. A gold mirror is used to focus the expanded laser beam into a spherically shaped plasma. A PVDF film sensor is used for the measurement of the interaction magnitude between the bubble and the flexible boundary. As the flexible boundary directly the PVFD film sensor is used. The sensor is flexibly mounted within a specially designed movable frame which enables to modify the elastic properties of the system. The bubble dynamics and the flexible wall movement are recorded by high-speed CCD camera and correlated with the acoustic signal obtained by the PVDF film. Different bubble collapse patters for different bubble wall distances and the corresponding acoustic signals are presented.

An experimental channel intended for investigation of a wake behind a cooled cylinder was designed and constructed in this work. The setup is designed for measurements with air at low Reynolds numbers. The measuring techniques based on the standard visualization with a fog generator and the constant temperature anemometry (CTA) were used. The flow performance was investigated behind two cylinders placed inside a channel with square cross section. One cylinder was kept at a constant flow temperature, while the second cylinder could be cooled using a water circuit with a thermostatic bath. The dependency of the Strouhal number on the Reynolds number was evaluated and compared to the literature data and the empirical correlations. The concept of an effective temperature in a non-isothermal flow was also applied. Unfortunately, a considerable difference between the preliminary measurements and the literature data was detected. The air-flow was found to have unsatisfactory high turbulence intensity. Consequently, some modifications of the current channel design are proposed.

This paper describes a process of numerical testing and optimization of the ultrasonic gas meter channel. A conventional ultrasonic flowmeter requires a large installation space due to the quality and stability of the velocity profile. Previously, the shape of the inner gas meter channel was optimized to reach a suitable flow field for ultrasonic measurement. The goal of this work is to find an optimal design of reduced size gas meter to achieve a stable velocity profile with minimum disturbances regardless of the entry conditions in the smallest possible space. Flow characteristics for volume flow rate in the range (1 to 250) m3/h were tested and the parameters of the gas meter were adjusted. Obtained results show good match with the requirements. Future work should aim to the measurement of transit time and the stability of measured values on the optimized design. Finally, it will enable to create the analogy between numerically obtained velocity fields and real transit time measurement.

Non-contact optical methods such as digital holographic interferometry are highly suitable in measurements where the phenomena is fast, performed in transparent or semi-transparent environment and mustn’t be obstructed as when applying local contact techniques. Such specific application can be studying dynamic events during transonic and supersonic blade flutter. Fast, sensitive and rather easy access to the phase information make these techniques very attractive in the study of phase objects/phenomena. However, since light’s phase is bounded to a repetitive cycle of 2π radians, the range of measurement is limited to one cycle of the phase, limiting applications to small gradient phenomena. This paper presents a new interesting way of by-passing this limitation, while still keeping noise values low, by introducing a second laser with a close value wavelength, giving rise to a new interferometric pattern with an extended unambiguous range of measurement. Image acquisition is done simultaneously for both wavelengths and all reconstructions are digitally performed. The principle and preliminary results are included in this paper.

This paper deals with the demonstration of the non-uniformity of velocity profiles in a DN 200 air circular pipe as part of the development of a newly designed tomographic ultrasonic flowmeter. The flowmeter should measure the flow quality independently. Therefore, different aerodynamic conditions were created by placing mechanical obstacles at the entrance of the measuring chamber, and these conditions were experimentally verified. As an experimental channel substituting a section with ultrasonic sensors, a glass segment was placed at the inlet of a suction pipeline, in front of which perforated plates were inserted to break the uniformity of the velocity profile. The two-dimensional Particle Image Velocimetry (2D PIV) method was used to measure in a plane lying in the longitudinal axis of the channel. The experimental setup and PIV system parameters are described. The results are presented as velocity profiles and contour diagrams in cross-sections at different longitudinal positions in the channel. The results show that the requirement of non-uniformity is satisfied. The used disturbing plates disturb the axial symmetry of the profiles and create a backflow.

Ultrasonic (US) flow meters are devices for a fluid flow measurement using the ultrasonic principle. Current research project dealing with developing the ultrasonic flowmeter with an innovative channel shape. Previously the work was aimed to the topology optimization using the CFD methods. The final prototype has to be analyzed experimentally to verify the velocity profiles in the US measurement section. The obtained velocity profiles in this region are necessary as the input for the US sensor data evaluation. A particle image velocimetry (PIV) was selected as a potentially suitable technique for the velocity profiles measurement. This paper presents the development and initial testing of a new experimental setup including the experimental track and PIV system. Several modifications were realized during the preparation of the experimental setup. Finally, measurements were performed with a simplified model and the results were evaluated in the form of velocity profiles in the area of interest. The most important results are the knowledge about the requirements on the model preparation. The future work will be aimed to the prototype of the ultrasonic flowmeter.

This article represents a part of an ongoing work on the preparation of an experimental rectangular channel for the PIV and LIF measurements of vortex structures and temperature field in a non-isothermal water flow. The main aim of the current study is to develop a sufficiently accurate simplified numerical model of the real problem. The basic requirements for thermal properties of heated bottom-wall are specified. In the computational model, there are several simplifications such as 2D case and a constant temperature of a heated surface along the longitudinal coordinate. Results of the numerical simulation of the fluid flow and heat transfer are verified on the experimental data obtained in a laboratory channel with the same geometry and similar flow conditions. The presented results helped to define additional requirements on the design of a new experimental channel intended for investigation of the flow instabilities in a non-isothermal liquid flow.

Piezoelectric PVDF sensors offer a unique option for the measurement of cavitation aggressiveness represented by the magnitude of impacts due to cavitation bubble collapses near walls. The aggressiveness measurement requires specific sensors shape and area, whereas commercial PVDF sensors are fabricated in limited geometry and size ranges. The photolithography method offers a possibility of production of home-made PVDF sensors of arbitrary shape and size. This paper deals with the calibration of a photolithographically home-made PVDF sensor for the cavitation impact load measurement. The calibration of sensors was carried out by the ball drop method. Sensors of different sizes were fabricated by the photolithography method from multi-purpose both side metallized PVDF sheet. The standard technology used for the fabrication of printed circuit boards was utilized. Commercial PVDF sensors of the same size were calibrated and the calibration results were compared with the home-made sensors. The effect of size and the effect of one added protective layer of Kapton tape on a sensor sensitivity were investigated.

Paper presents new mathematical model for air flow velocity distribution in rounded rectangular ducts and its experimental verification. In papers [1, 2] an mathematical model based on modified Prandtl equation for power power-law velocity profile was determined. It works very well for smaller cross sections. During the study of larger cross sections new phenomena in flowing air have been observed, it forced the search for a new model. The new model is based on a rounded rectangular division into two parts: slot and rounded square.

In the article author identifies a possible bone of mutual vibration energy measuring application used in the study of standard rail, as part of a dedicated research methodology and detailed methodologies developed in many previous author studies. Theoretical analysis and practical verification of susceptibility testing measurement information complex vibration processes indicates a possibility for their use. Recognizing the need to improve methods of machines and structures testing to assess their degradation state - this work presents important results of the research in the verification field of the proposed measures effectiveness of mutual research bench.

The synthetic jets (SJs) have many significant applications and the number of applications is increasing all the time. In this research the main focus is on the primary flow control which can be used effectively for the heat transfer increasing. This paper deals with the experimental research of the effect of two SJs worked in the bifurcated mode used for control of an axisymmetric air jet. First, the control synthetic jets were measured alone. After an adjustment, the primary axisymmetric jet was added in to the system. For comparison, the primary flow without synthetic jets control was also measured. All experiments were performed using PIV method whereby the synchronization between synthetic jets and PIV system was necessary to do.

This paper reports on measurements by digital holographic tomography in flow measurement. It is demonstrated capability of the method by measurement of general temperature field consisting of system of three orifices. Results obtained by digital holographic tomography are compared to results obtained by hot wire anemometry CTA.

This article deals with numerical investigation of flow and mixing of air and sulphur dioxide SO2 in designated mixing chamber. The mixing chamber is a part of experimental laboratory reactor designed for simulating the flue gas desulfurization (FGD) process. Aim of this work is the numerical investigation of effect of different mixing chamber geometries to mixture composition, especially to mass fraction of sulphur dioxide. Using of similar concentration of sulphur dioxide in the experimental reactor as in the real process is necessary to be able to make additional research. Conclusion describes the effect of different geometries of mixing chamber to mixing. The aim of this work is to develop perfectly works mixing chamber, which will be manufactured and then implemented into experimental FGD reactor. The results will be validated by experiment after the mixing chamber will be manufactured.

This paper describes the additional research of the synthetic jet array in a channel flow and continues the paper of authors Dančová, Trávníček and Vít, [1]. Numerical simulations support the experiments from [1] and the influence of the new slope of the synthetic jet orifices is studied here. This research will be used for preparation of the experiments with inclined orifices of the synthetic jet array.

This paper describes an investigation of the commercial synthetic jet actuator “SynJet ZFlow 90 Outdoor Cooler” (Nuventix). The velocity flow field was investigated using the thermoanemometry method in the constant temperature mode. The Eigen frequency of the used actuator was also calculated in this work.

Presented paper includes description of design and assemblage of an experimental device for measuring temperature field into thermoacoustic generator using holographic interferometry method. This paper introduces the process of measurement on this apparatus and processing and analysis results too.

The paper deals with the measurement of temperature fields in a synthetic jet. This type of experiment presents several challenges; therefore, to ensure the best precision possible, two experimental methods were used – digital holographic interferometry (DHI) and thermo-anemometry in constant current mode as an auxiliary method to verify DHI.

A numerical and experimental study of multiple circular synthetic jets interacting with low Reynolds number laminar channel flow is presented. Flow velocity and temperature fields in channel are computed using three-dimensional computational model under a meso-scale. The working fluid is air. Moreover, flow visualization in water is performed under approximately double size. The computed flow field and heat transfer distribution on the wall are compared with the experimental results.

The article deals with experimental investigation into flow in an ejector with four synthetic jets. The aim of the synthetic jets is to excite the mixing layer in the ejector and intensify the mixing process. The cavities of the synthetic jet actuators are hidden in the mixing chamber wall and the synthetic jets are perpendicular to the ejector axis. CTA and pneumatic measuring method were used to investigate the influences of synthetic jets on flow inside the ejector.

In this paper, 2D simulations were carried out to prove the potential of thermoacoustic technology in separating a binary gas mixture. A 2D model of a gas mixture separator was developed, including a loudspeaker responsible for producing acoustic waves in the separation pipe. As a result of the imposed sound waves propagating inside the separator, main parameters including pressure, temperature, and density undergo oscillations, which in turn drive the light and heavy gas components in opposite directions. Through time, one end of the separator is enriched with the light component while the other end is enriched with the heavy one. Simulations were all performed using ANSYS Fluent. The aim was to separate an ideal gas mixture of Helium–Argon and study the impact of different parameters on the separation process. [ABSTRACT FROM AUTHOR]

This paper introduces, describes, and compares the energy storage technologies of Compressed Air Energy Storage (CAES) and Liquid Air Energy Storage (LAES). Given the significant transformation the power industry has witnessed in the past decade, a noticeable lack of novel energy storage technologies spanning various power levels has emerged. To bridge this gap, CAES and LAES emerge as promising alternatives for diverse applications. The paper offers a succinct overview and synthesis of these two energy storage methods, outlining their core operational principles, practical implementations, crucial parameters, and potential system configurations. The article also highlights approaches to enhance the efficiency of these technologies and underscores the roles of thermal energy storage within their processes. Furthermore, it delves into the discussion of the significance of hybrid systems and polygeneration in the contexts of CAES and LAES technologies. Moreover, we briefly explore the potential integration of these technologies into other power systems. [ABSTRACT FROM AUTHOR]