Gaseous Fluid Flow Research Articles

Nonlinear Damping as the Fourth Dimension in Optical Fiber Anemometry

AbstractIn this study, nonlinear damping is introduced as the fourth dimension in the operation of a fiber tip optomechanical anemometer. The flow sensing element, featuring a 3D rotor measuring 110 µm in diameter and fabricated through a two‐photon nanomachining process, is monolithically integrated onto the cleaved face of the optical fiber, which serves as an integrated waveguide. As the rotor encounters airflow, it spins, and mirrors on its blades reflect light across the fiber core at each pass. This setup permits precise measurement of gaseous fluid flow with minimal sensor footprint at the point of detection and accommodates a variety of optical sources and measurement apparatuses without the need for specific wavelength or broad‐spectrum capabilities. To stabilize the rotation of the rotor and facilitate consistent frequency‐domain analysis, a polydimethylsiloxane hydrocarbon stabilizing agent is infused into the gap between the rotor and stator of the sensing element via dual‐function microfluidic channels. This enhancement allows for the measurement of gaseous nitrogen flow rates from 10 to 20 liters per minute (LPM), with a consistent periodic response. Comprehensive characterizations of the fiber tip anemometer are presented with and without the stabilizing medium, demonstrating its crucial role in regulating the dynamics between the rotor and the stator.

Estimation of Gas Leak Volume to Quantify Gaseous Fluid Flow in Processing Plants

Estimation of Gas Leak Volume to Quantify Gaseous Fluid Flow in Processing Plants

Heat transfer and friction factor correlations for slip gaseous fluid flow in confined porous medium with pore-scale LBM modelling

The gaseous fluid flow and heat transfer with the consideration of rarefaction effects are important at micro/nano-scales. The formulation of accurate predictive models is beneficial to optimize the heat transfer and friction across the porous domain, in micro- and nano-devices. In this work, the lattice Boltzmann method (LBM) with multiple-relaxation-time (MRT), which offers a natural and robust way to simulate the slip gaseous fluid flow and heat transfer, was applied to the confined porous medium at a pore-scale level. An efficient boundary scheme was utilized at the walls of porous media to consider the velocity slip and temperature jump effect. A two-dimensional porous domain composed of different types of micro obstacles (circle, ellipse and diamond) was established for the pore-scale simulations. Nusselt number (Nu) and friction factor (Cf) were obtained and analyzed across the obstacles with varying Knudsen number (0.0 ≤ Kn ≤ 0.1), Reynolds number (1 ≤ Re ≤ 10) and porosity (0.4 ≤ ε ≤ 0.8). With increasing Re number, Nu number shows an increasing trend for all obstacles, however, for increasing Kn number, Nu number decreases accordingly. Whereas, the friction factor Cf shows a decreasing trend for both increasing Kn and Re numbers. Based on the obtained results, the new predictive correlations for Nusselt number and friction factor were proposed, which will be valuable to understand the slip gaseous flow characteristic in confined porous space.

Numerical Modeling of Slip Flow and Heat Transfer Over Microcylinders With Lattice Boltzmann Method

In this paper, a lattice Boltzmann (LB) model is established to simulate the gaseous fluid flow and heat transfer in the slip regime under the curved boundary condition. A novel curved boundary treatment is proposed for the LB modeling, which is a combination of the nonequilibrium extrapolation scheme for the curved boundary and the counter-extrapolation method for the macroscopic variables on the curved gas–solid interface. The established numerical model can accurately predict the velocity slip and temperature jump of the microscale gas flow on the curved surface, which agrees well with the analytical solution for the microcylindrical Couette flow and heat transfer. Then, the slip flow and the heat transfer over the single microcylinder are numerically studied in this work. It shows that the velocity slip and the temperature jump are obviously influenced by the Knudsen number and the Reynolds number, and the local Nusselt number depends on which gas rarefaction effect (velocity slip or temperature jump) is dominant. An increase in the Prandtl number leads to a decrease in the temperature jump, which enhances the heat transfer on the microcylinder surface. The numerical simulation of the flow and heat transfer over two microcylinders in tandem configuration are carried out to investigate the wake interference effect. The results show that the slip flow and heat transfer characteristics of the downstream microcylinder are influenced by the wake region behind the upstream cylinder as the spacing is small.

A new curved boundary treatment for LBM modeling of thermal gaseous microflow in the slip regime

The lattice Boltzmann method (LBM) modeling shows its powerful capability in the numerical prediction of thermal gaseous fluid flow. However, the LBM simulation of gaseous microflow with complex boundaries is still challenging, in which the uniform Cartesian lattices are adopted in the numerical model. In this work, a new curved boundary treatment for LBM modeling of thermal gaseous microflow in slip regime is proposed, which is a combination of the non-equilibrium extrapolation method for curved boundary and the counter-extrapolation method for the gas velocity/temperature on the curved wall. The proposed treatment considers the effect of the offset between the physical boundary and the closest grid line and involves no specific gas–wall interaction parameters, which is proved to be more accurate and applicable. The new curved boundary treatment is utilized with the multiple-relaxation-time model and then validated for several benchmark cases, which shows its superiority in slip flow and heat transfer prediction compared with the current curved boundary schemes for gaseous microflow.

ENTRANCE EFFECTS OF THERMAL CREEP ON FLUID HEATING IN RECTANGULAR MICROCHANNELS

The effects of thermal creep on the development of gaseous fluid flow and heat transfer in rectangular microchannels with constant wall temperature are investigated in the slip-flow regime. Thermal creep arises from tangential temperature gradients, which may be significant in the entrance region of channels, and affects the velocity and temperature fields particularly in low Reynolds number flows. In the present work, the Navier–Stokes and energy equations coupled with velocity-slip and temperature-jump conditions applied at the channel walls are solved numerically using a control-volume technique. Despite the constant wall temperature, tangential temperature gradients form in the gas layer adjacent to the wall due to the temperature-jump condition. The effects of slip/jump and thermal creep on the flow patterns and parameters are studied in detail for a wide range of channel aspect ratios and, Knudsen and Reynolds numbers. Furthermore, the effects of variable properties on velocity-slip and, friction and heat transfer coefficients are also examined.

STUDY OF GAS–SOLID FLOW IN A MULTICHANNEL CYCLONE / ORO IR KIETŲJŲ DALELIŲ SRAUTO DAUGIAKANALIAME CIKLONE TYRIMAS

This paper aims to analyse the problem of the gas–solid particle (SP) flow in the multichannel cyclone (three rings) with tangential inlet (KDG – equipment for separation of solid particles from gaseous fluid flow). It provides a review of experimental and theoretical papers that describe cyclones with a very complex swirling flow. The paper describes the experimental study and numerical modelling of the flow in the multichannel cyclone, the height of which is 0.72 m and the diameter – 0.50 m; with the height of the cylindrical part amounting to 0.29 m, the height of the conical part – 0.43 m, and the inlet area – 0.29×0.034 m2. The multi-functional measuring instrument Testo 400, intended for measuring the flow velocity in the inlet and outlet of the multichannel cyclone was used in experimental studies of the cyclone. Three-dimensional transport differential equations (Reynolds) for incompressible turbulent flow inside a cyclone are solved numerically using finite volume-based numerical method and turbulence models, namely the Standard k-ϵ model, the RNG k-ϵ model. According to results obtained during the experiments with quartz sand and quartz sand dust pollutants, the highest SP treatment efficiency as regards these pollutants, reaching 85.8-90.4%, was obtained. Modelling results obtained from the numerical tests with the inlet velocity of 6.27–10.78 m/s and, the flow rate of 0.111–0.190 m3/s have demonstrated a reasonable agreement with experimental and theoretical results. The average relative error was ± 4.3%. Santrauka Nagrinėjama dujų ir kietųjų dalelių aerodinamika daugiakanaliame (trijų žiedų) išcentriniame ciklone-filtre (keturkanalis dulkių gaudytuvas – KDG). Srauto įtekėjimas tangentinis. Apžvelgti eksperimentiniai ir teoriniai procesų tokiuose ciklonuose, kuriuose susidaro ypač sudėtingas sūkurinis srautas, tyrimo darbai. Atliktas eksperimentinis tyrimas ir skaitinis oro srauto judėjimo KDG ciklone modeliavimas (ciklonas 0,72 m aukščio ir 0,50 m skersmens, cilindrinės dalies aukštis −0,29 m, kūginės (dulkių rinktuvo) −0,43 m, įtekėjimo angos plotas −0,29×0,034 m2). Ciklono eksperimentiniams tyrimams naudota Testo 400 daugiafunkcis matuoklis, skirtas oro srauto greičiui matuoti daugiakanalio ciklono įtekėjimo ir ištekėjimo angose. Pateiktosios pernašos trimatės diferencialinės lygtys (Reinoldso) atvejo, kai turbulentinis srautas ciklono viduje nespūdusis, skaitiškai spręstos baigtinių tūrių metodu, taikant standartinį k-ϵ, ir RNG k-ϵ turbulencijos modelius. Remiantis tyrimų rezultatais, didžiausiasis ciklono su kvarcinio smėlio ir kvarcinio smėlio dulkių teršalais valymo efektyvumas siekė 85,8–90,4%. Modeliavimo rezultatai, kai įtekėjimo greitis 6,27–10,78 m/s ir debitas −0,111–0,190 m3/s, atitinkamai neblogai sutapo su eksperimentų duomenimis. Vidutinė santykinė paklaida siekė ±4,3 proc.

ANALYSIS OF NUMERICAL MODELLING OF TURBULENCE IN A CONICAL REVERSE‐FLOW CYCLONE

This paper aims to analyse the problem of numerical modelling of the airflow in a conical reverse‐flow (CRF) cyclone with tangential inlet (equipment for separation of solid particles from gaseous fluid flow). A review of experimental and theoretical papers that describe cyclones with very complex swirling flow is performed. Three‐dimensional transport differential equations for incompressible turbulent flow inside a cyclone are solved numerically using finite volume‐based turbulence models, namely, the Standard k–ϵ model, the RNG k–ϵ model and the Reynolds stress model (RSM). The paper describes the numerical modelling of the airflow in the CRF cyclone, the height of which is 0.75 m, diameter ‐ 0.17 m, height of cylindrical part ‐ 0.255 m, height of conical part ‐ 0.425 m, inlet area is 0.085×0.032 m2. Mathematical model of airflow in a cyclone consisted of Navier‐Stokes (Reynolds) three‐dimensional differential equation system. Modelling results, obtained from the numerical tests when inlet velocity is 4.64, 9.0 and 14.8 m/s and flow rate is, respectively, 0.0112, 0.0245 and 0.0408 (0.0388) m3/s, have demonstrated a reasonable agreement with other authors’ experimental and theoretical results. The average relative error was ± 7.5%. Santrauka Nagrinejama duju aerodinamikos kūginiame grižtamojo srauto (KGS) ciklone (irenginys kietosioms dalelems atskirti iš oro srauto) su tangentiniu srauto itekejimu skaitinio modeliavimo problema. Trimates nespūdžiojo turbulentinio srauto ciklono viduje pernašos diferencialines lygtys skaitiškai sprestos baigtiniu tūriu metodu taikant standartini k–ϵ, RNG k–ϵ ir Reinoldso itempiu (RIM) turbulencijos modelius. Atliktas skaitinis oro srauto judejimo KGS ciklone modeliavimas. Ciklono aukštis – 0,75 m, skersmuo ‐ 0,17 m, cilindrines dalies aukšti ‐ 0,255 m, kūgines ‐ 0,425 m, itekejimo angos plotas 0,085×0,032 m2. Oro srauto judejimo ciklone matematinis modelis – Navje ir Stokso (Reinoldso) trimačiu diferencialiniu lygčiu sistema. Modeliavimo rezultatai, kai itekejimo greitis 4,64, 9,0 bei 14,8 m/s ir debitas – 0,0112, 0,0245 ir 0,0408 (0,0388) m3/s, neblogai sutapo su kitu autoriu eksperimentiniais rezultatais. Vidutine santykine paklaida ‐ ± 8 proc. Резюме Анализируется проблема аэродинамики газового потока в коническом возвратного потока (КВП) циклоне (оборудование для отделения твердых частиц от газового потока) с тангенциальной подачей газа. Произведен обзор экспериментальных и теоретических работ в циклонах такого типа, в которых образуется сложное вихревое течение потока. Для моделирования использованы трехмерные дифференциальные уравнения переноса, численно решаемые методом конечных объемов с использованием следующих моделей: стaндартной k–e, RNG k–e и рейнольдсовой модели турбулентности напряжений. Произведено численное моделирование движения потока воздуха в циклоне КВП, высота которого 0,75 м, диаметр – 0,17 м, высота цилиндрической части – 0,255 м, конической части – 0,425 м, площадь входного отверстия – 0,085×0,032 м 2 . Математическую модель движения потока воздуха в циклоне составила система трехмерных дифференциальных уравнений Навье-Стокса и Рейнольдса. Анализ результатов, произведенный при скоростях втекания в циклон 4,64, 9,0 и 14,8 м/с (дебит – 0,0112, 0,0245 и 0,0408 м 3 /c) и для модели рейнольдсовых напряжений, показал приемлемую согласованность с результатами других исследователей – со средней относительной погрешностью ± 7,5 проц.

ANALYSIS OF THE NUMERICAL MODELLING OF TURBULENCE IN THE CONICAL REVERSE-FLOW CYCLONE

The paper describes the numerical modelling of the swirling fluid flow in the Stairmand cyclone (conical reverse-flow – CRF) with tangential inlet (equipment for separating solid particles from the gaseous fluid flow). A review of experimental and theoretical papers is conducted introducing three-dimen­sional differential equations for transfer processes. The numerical modelling of the Stairmand cyclone the height of which is 0.75 m, diameter – 0.17 m, the height of a cylindrical part – 0.290 m, a conical part – 0,39 m and an inlet area is 0,085×0,032 m is presented. When governing three-dimensional fluid flow, transfer equations Navje-Stokes and Reynolds are solved using the finite volume method in a body-fitted co-ordinate system using standard k– e and RNG k– e model of turbulence. Modelling is realised for inlet velocity 4.64, 9.0 and 14.8 m/s (flow rate was 0.0112, 0.0245 and 0.0388 m3/s). The results obtained from the numerical tests have demonstrated that the RNG k– e model of turbulence yields a reasonably good prediction for highly swirling flows in cyclones: the presented numerical results (tangential and radial velocity profiles) are compared with numerical and experimental data obtained by other authors. The mean relative error of ± 7,5% is found.

Study of gas biogeochemical parameters of gaseous fluids from the bottom of the Black Sea

Gaseous fluid flows from sediments into bottom water of seas and oceans attract attention of oceanographers, particularly specialists in gas geochemistry [1]. Fluid flows from the Black Sea bottom were the main study object in Cruise 61 of the R/V Professor Vodyanitskii , carried out in the Ukrainian segment of the Black Sea in June‐July, 2004. The expedition was organized and conducted by the Division of Marine Geology and Sedimentary Ore Formation, National Academy of Sciences of Ukraine. Gas biogeochemical parameters were investigated at the Institute of Oceanology (Moscow). These works were aimed at studying spatial variations in gas biochemical parameters in seawater and bottom sediments in the zone of local fluid flows. Bottom water was sampled in fluid discharge areas detected by multibeam sonar as a gaseous plume. Samples were taken closest to the fluid discharge site in the depth interval of 200‐2000 m. Specially designed equipment and methods were used for the study of gas biogeochemical parameters [2]. Water samples were taken with a hermetic bottom bathometer from the bottom layer of 1.5‐2.0 m above the seafloor, with the bathometer cartridge at several meters above the bottom, and by integration of the bathometer from the water column located 100‐150 m above the bottom. Bottom sediments were sampled by a gravity corer with a plastic container that fills with sediments in situ. In the case of spontaneous degassing of gas-saturated sediment after dismantling of the corer on deck, the released gas mixture inflated the container and the gas sample was taken by syringe for chromatographic analysis. Then, sediment samples were taken at different levels of the core. The content of gas components (hydrocarbons, helium, hydrogen, carbon dioxide, and permanent gases) and biochemical parameters, such as the ATP content and alkaline phosphomonoesterase activity (APHA), were simultaneously determined in water and sediment samples. The article presents new factual data on underwater fluid discharge areas. Methane and carbon dioxide appeared to be most informative among gas components. Hydrogen, helium, and homologues of methane were not detected, because their concentration in the analyzed gas mixture was below the sensitivity of the chromatograph. The gas mixture was either sampled immediately from the plastic container of the gravity corer (or hermetic core catcher) or was extracted by phase-equilibrium degassing of seawater and sediment samples. In both cases, air was the main gas carrier. Therefore, oxygen and nitrogen were also measured methodologically. In total, approximately 100 samples were analyzed. The gas mixture contained methane (0.0‐89.8 vol %) and carbon dioxide (0.0‐15.5 vol %). The total content of oxygen and nitrogen varied from 8.65 to 100 vol %. Table 1 presents data on various gas mixtures obtained from the gravity corer container and hermetic core catcher or extracted from water and sediment samples. Biochemical parameters were measured in the same water and sediment samples. In addition, certain intervals of the core and bottom and surface water samples were analyzed to estimate biological activity of seawater medium in study areas. Table 2 presents gasometric and biochemical data. The data from Tables 1 and 2 make it possible to disclose some peculiarities in the distribution of gas biogeochemical parameters. In the study areas, bottom water is saturated with methane and carbon dioxide. The biological activity of water is sufficiently high and

Noise suppression and particle separation apparatus for high pressure gaseous fluid flows

Noise suppression and particle separation apparatus for flows of high pressure, high velocity, particle-laden, gaseous fluid, such as geothermal steam, comprises a gaseous fluid conduit that has axially installed around its discharge end a larger diameter, cylindrical inner expansion chamber having a number of flow-dividing fluid discharge openings at which fluid flow diffusing elements are connected for receiving and diffusing the flow of gaseous fluid from the apertures. A still-larger diameter, cylindrical noise suppression chamber is axially mounted around the inner chamber and flow diffusing elements. The diffusion elements increase the fluid flow noise frequency range and sound deadening material installed in the outer chamber absorbs noise in this higher frequency range so that the venting fluid noise level outside the apparatus is no more than about 95 dB. To enable fluid expansion, the fluid conduit diverges at its outlet end, the inner chamber has a diameter at least about twice that of the flow inlet conduit and the outer chamber has a diameter that is at least about twice that of the inner chamber. Flow direction and velocity changes in the apparatus cause the disengagement of particulates entrained in the fluid flow.