Mean Void Research Articles

Assessment of ansys-fluent Code for Computation of Two-Phase Flow Characteristics: A Comparative Study of Water–Air and Silicone Oil–Air in a Vertical Pipe

Abstract The study aimed to assess the flow characteristics of water–air and silicone oil–air in a vertical upward pipe, utilizing computational fluid dynamics (CFD) simulations with the volume of fluid (VOF) model. Structured meshes with various resolutions were employed to ensure mesh independence, and the k–ε realizable model addressed turbulence. Simulations were conducted in a vertical pipe with a diameter of 67 mm, while varying superficial gas velocities. The investigation focused on the impact of superficial gas velocity on flow patterns, radial void fractions, void fraction time series, probability density functions (PDFs), and mean void fractions. Results indicated a transition in flow patterns with increasing superficial gas velocities: water–air shifted from cap-bubbly to churn flow, and silicone oil–air transitioned from bubbly to annular flow. Notably, annular flow was observed in silicone oil even at low gas velocity. Substantial alterations were observed in radial void fraction profiles corresponding to changing flow patterns. Void fraction time series showed higher fluctuations for water compared to silicone oil, and PDFs identified regimes. Mean void fraction consistently demonstrated higher values for silicone oil compared to water across all flow conditions. The CFD results were validated against experiments, demonstrating good agreement. Furthermore, the validated model was applied to predict pressure drops and liquid velocities between the two systems. Silicone oil exhibited lower pressure drops compared to water. Significant differences in liquid velocities were observed between the two systems at 0.05 m/s and 5.71 m/s, emphasizing the impact of fluid properties.

Understanding two‐phase flow behaviour: CFD Assessment of silicone oil–air and water–air in an intermediate vertical pipe

AbstractThe study utilized computational fluid dynamics (CFD) simulations employing the volume of fluid (VOF) model to analyze silicone oil–air flows in a vertical pipe with a diameter of 67 mm. Various structured meshes ensured grid independence, and the k‐ε realizable model addressed turbulence. The analysis characterized bubbly to annular flows, involving the evaluation of flow patterns, radial void fractions, void fraction time series, probability density functions (PDFs), power spectral densities (PSDs), and mean void fractions. Results indicated a transition from bubbly to annular flow with increasing gas velocities and notable changes in radial void fraction profiles. Void fraction exhibited significant variations with distinct flow patterns at constant liquid velocity. PDFs identified flow regimes, and PSDs revealed frequency patterns. CFD results were validated against experiments, demonstrating good agreement. The validated CFD model was utilized to investigate radial gas velocities and pressure drops, revealing a shift from uniform velocity distributions to irregular patterns and a decrease in total pressure drop with an increase in gas superficial velocity. The model was also applied to a water‐air system to explore two‐phase flow behaviour. The impact of superficial gas velocity on flow patterns and radial void fractions was studied through numerical analysis and compared with the silicone oil‐air system. Results showed that at extreme gas velocities (0.06 and 5.53 m/s), silicone oil exhibited bubbly and annular flows, while water displayed cap bubbly and churn flows. The significant variation in radial void fraction at these velocities emphasized the impact of fluid properties.

Spatial virtual recovery design technology of ancient buildings based on 3D laser scanning technology

Due to the persistent advancements in science and technology, the implementation of digital technology in the preservation of cultural heritage is progressively expanding. One of the focal points of research lies in the spatial virtual restoration design technology of ancient edifices, which is based on three-dimensional laser scanning technology. The study initially outlines the process of obtaining point cloud data via 3D laser scanning technology and subsequently executes denoising, splicing, and simplification processing on the point cloud. Subsequently, the pre-processed data undergo 3D mesh model construction. Finally, an effective repair technique is implemented to address the void phenomenon present during the modeling process. To construct the implicit surface, the RBF method is employed and new vertices are adjusted, resulting in a more accurate spatial virtual restoration of ancient buildings (ABs). The study found that using the radial basis function based void repair method resulted in a mean void repair accuracy of 92.38% in the west wall, an improvement of 3.08% compared to the Liepa-based method. In addition, this method achieved the highest accuracy of 98.94% on the north wall, improving by 6.37% compared to the Poisson grid editing algorithm. Meanwhile, the RBF-based method repaired cavities in the west wall model with an average runtime of only 20.613 s, resulting in a 19.16 s reduction compared to the Liepa-based method. In addition, the method’s average repair time for the north wall was only 5.364 s, a decrease of 13.28 s compared to the Poisson grid editing algorithm. This shows that combining 3D laser scanning technology and cavity repair technology can acquire high-quality point cloud data of historic structures, create precise 3D models, and achieve spatial virtual restoration. This offers a new and efficient technological approach to preserving and passing down ABs.

Predicting the precipitated calcium carbonate and unconfined compressive strength of bio-mediated sands through robust hybrid optimization algorithms

Biological soil stabilization through Microbial-Induced Calcite Precipitation (MICP) demonstrates the potential to be an eco-friendly and sustainable approach to enhance the strength properties of cohesionless granular soils. In this study, based on a comprehensive set of experimental data compiled from literature, the amounts of Precipitated Calcium Carbonate (PCC) and Unconfined Compressive Strength (UCS) of MICP-treated sands are estimated through hybridizing Artificial Neural Network (ANN) and Adaptive Neuro-Fuzzy Inference System (ANFIS) models with metaheuristic algorithms. During the data extraction procedure, a total of 70 and 115 datasets are used to predict the PCC and UCS, respectively. Accordingly, five key features of urea concentration (Mu), calcium chloride (Mcc), optical density of bacterial suspension (OD600), pH and total volume of injection per volume of sample (Vt), are first selected as the inputs of the hybrid models to estimate the amount of calcium carbonate precipitation within the porous structure of MICP-treated granular medium. The experimental data on the PCC along with the basic characteristics of the host sand including mean grain size (D50), uniformity coefficient (Cu) and void ratio (e), are then adopted as the inputs of the numerical models in the second phase whilst the UCS of bio-mediated sands is set as the output. The performance and accuracy of implemented models are rigorously assessed through analyzing various statistical indices and performance criteria. According to the numerical analysis, the ANN-PSO and ANFIS-PSO hybrid models show the best performance in predicting PCC and UCS of bio-mediated sands, respectively. Using the well-established Gene Expression Programming (GEP) algorithm, practical correlations are developed to predict the PCC and UCS values of MICP-mediated soils based on the characteristics of biological binding agents as well as the host material. The Machine Learning (ML)-based models presented in this study provide engineers with a fruitful framework for the rough and preliminary estimation of the amount of calcite precipitation as well as the UCS of bio-mediated sands in the field prior to stabilization and performing complementary tests.

Mechanical Behavior and Void Analysis of 3D Printed PEEK by Fused Deposition Modeling (FDM) with Varying Infill Patterns

Polyether ether ketone (PEEK) was printed via FDM using gyroid, line, and tri-hexagon infill patterns. Its effect on the mechanical behavior (tensile, flexural and compression) and the investigation of void percentage and orientation angles within the internal structure were studied. The line pattern showed the highest tensile strength at 55.46 MPa due to its internal structure with a higher number of deposited layers oriented along the direction of the stress enabling higher stress absorption, the laminate theory. The angular lines on both tri-hexagon and gyroid patterns provided disadvantage as supported by Timoshenko's theory where the internal structures acted like a beam which is prone to easier deformation. Line pattern also demonstrated the highest flexural strength at 103.67 MPa. The continuity of the pattern along the internal structure perpendicular to the direction of the force provided more effective transfer of stress. However, the highest compressive load was observed in gyroid pattern with 8,266.89 N. The redundancies in the internal structure design of gyroid pattern enabled more compression load absorption. Symmetry and internal angles in gyroid and tri-hexagon patterns allowed more compressive force which are more susceptible to fractures due to higher strains created. Lastly, void percentage showed line pattern with the lowest at 1.53%. In addition, the mean void orientation angle showed that the closer it is to 0o, the weaker the part.

3D simulation of pulsatile bubbly flow resembling decompression sickness conditions inside a realistic human artery

I-VED (In-Vivo Embolic Detector) is a novel diagnostic tool for non-invasive, real-time detection of bubbles in humans. Bubbles are precursors of decompression sickness (DCS), which can be encountered in astronauts, scuba divers, etc. I-VED exploits an EU patented electrical impedance spectroscopy technology, developed under the umbrella of a European Space Agency project. So far, I-VED has been calibrated and validated in vitro. In view of the forthcoming in-vivo trials, it needs to be configured for sensing bubbles in the bloodstream. For this, 3D computational fluid dynamics simulation is performed to investigate axial and radial variation of void fraction (α) and flow velocity (U) in a pulsatile bubbly flow inside a realistic human artery (diameter: 5–20 mm, implying vessel dilatation or contraction), where liquid velocity, bubble size, and void fraction resemble DCS conditions. Results show that U and α show a core-peaking profile despite the variation of artery diameter, while 3D sharp turns yield U and α non-uniformities in the angular direction that do not affect mean void fraction across the artery. Obtained knowledge allows deeper insight on the physics and spatial characteristics of bubbly flow in a real artery, which is useful in the design of measuring volume and tuning of I-VED.

Small-strain shear stiffness of sand-gravel mixtures

Small-strain shear stiffness (G0) is a key parameter for seismic ground response analysis and performance evaluation of various earth structures and foundations. To account for its pressure and density dependency, G0 has been conveniently correlated to mean effective stress (σm′) and void ratio (e). Such an approach is suitable for conventional uniform materials. However as found in this study, it is not always applicable to estimate the G0 of sand-gravel mixtures (SGMs), because it essentially fails to account for the combined effects of density and gravel content (GC). In this study, aimed at addressing this issue and developing a theoretical framework and empirical correlations suitable for estimating the G0 of SGMs, a series of bender element laboratory tests were carried out on selected SGMs. Specifically, SGMs were obtained by mixing two clean sands – namely New Brighton Sand (mean diameter, D50 = 0.2 mm) and Dalton River Washed Sand (D50 = 0.75 mm) – and rounded pea gravel (D50 = 5.5 mm). Shear wave velocity of specimens having GC = 0, 10, 25, 40 and 60% and prepared at a relative density (Dr) of 20, 30, 45 and 60% was measured at σm′ = 50, 100, 150 and 200 kPa. The laboratory results indicated that G0 of SGMs increases with increasing both the Dr and σm′, whereas the effect of GC would be marginal to significant depending on the limiting and threshold sand contents. To correlate G0 simultaneously with both GC and Dr, the equivalent void ratio (ef(eq)) was adopted. It is shown that the use of ef(eq) makes it possible to uniquely describe the G0 of SGMs for any combination of GC and Dr over the full range of σm′ level applied in this study.

Investigation of ductile damage in dual phase steel during tensile deformation by in situ X-ray computed tomography

In situ synchrotron radiation X-ray computed tomography (CT) is used to understand the void nucleation and growth behaviour of dual phase (DP) steel, DP800, during uniaxial tensile deformation. The voids were identified post mortem as having nucleated primarily in the (41 vol%) martensite phase. The behaviour of individual voids was found to be broadly in line with a Rice and Tracey style growth model (their volume increasing by a factor of 10), while the mean void size was broadly in line with a model that included the continuous nucleation of new voids, as well as the growth of existing voids, throughout straining. Voids tended to elongate during uniaxial (low stress triaxiality) straining, but then to dilate more isotropically as necking led to increased triaxiality. One large pre-existing void was found to elongate quicky at first, but then for growth to slow, presumably because it was not located in the highest triaxial stress (necked) region. Perhaps surprisingly the average size of the void population grows only slowly (by a factor of 2) during straining; this is because while the size of each void grows, new small voids are always being nucleated. Finally, the changes of stress triaxiality and shear stress state during tensile deformation of the square cross-section smooth tensile specimen are investigated via finite element modelling, to qualitatively assess the impact of sample geometry on void nucleation behaviour and fracture strain in the current study.

Separate and joint clustering characteristics of large-Stokes-number sprays subjected to turbulent co-flows

Separate and joint droplets, clusters, and voids characteristics of sprays injected in a turbulent co-flow are investigated experimentally. Simultaneous Mie scattering and interferometric laser imaging for droplet sizing along with separate hotwire anemometry are performed. The turbulent co-flow characteristics are adjusted using zero, one or two perforated plates. The Taylor-length-scale-based Reynolds number varies from 10 to 38, and the Stokes number estimated based on the Kolmogorov time scale varies from 3 to 25. The results show that the mean length scale of the clusters normalized by the Kolmogorov length scale varies linearly with the Stokes number. However, the mean void length scale is of the order of the integral length scale. It is shown that the number density of the droplets inside the clusters is approximately 7 times larger than that in the voids. The ratios of the droplets number densities in the clusters and voids to the total number density are independent of the test conditions and equal 5.5 and 0.8, respectively. The joint probability density function of the droplets diameter and clusters area shows that the droplets with the most probable diameter are found in the majority of the clusters. It is argued that intensifying the turbulence broadens the range of turbulent eddy size in the co-flow which allows for accommodating droplets with a broad range of diameters in the clusters. The results are of significance for engineering applications that aim to modify the clustering characteristics of large-Stokes-number droplets sprayed into turbulent co-flows.

The correlation of fractal dimension to fracture surface slope for fatigue crack initiation analysis under bending-torsion loading in high-strength steels

In this study, the fractal dimension of fatigue fracture surfaces is investigated in order to find an alternative failure loading indicator. Some of many metrological factors are generalized by reducing the fracture surface structure to one factor and develop an entire fracture surface procedure by analyzing the impact of surface slope and calculation resolution. Three notched geometries are studied under cyclic bending-torsion: 34CrNiMo6 high-strength steel bars with transverse blind holes; (ii) 34CrNiMo6 high-strength steel bars with lateral U-shaped notches; and (iii) 18Ni300 maraging steel hollow bars with transverse holes produced by selective laser melting. The surface topographies of fatigue fractures were measured with an optical profilometer. The bending-torsion ratio, maximum local von Mises equivalent stress and the number of cycles to crack initiation are examined using the fractal dimension. Moreover, a comparison was also made for conventional surface topography parameters such as root mean square height and void volume. A fatigue crack initiation model based on surface topography and loading conditions is proposed. The model relies on the product of the maximum local von Mises equivalent stress and the fractal dimension divided by the root mean square height to void volume ratio. The results show that the fracture plane geometry, expressed by the fractal dimension Df, can facilitate the estimation of post-failure loading history. In particular, the analysis based on the enclosing boxes method (EBM) is more accurate when it is used as an extra-fine resolution without any plane leveling.

Carbon dioxide-water bubbly flow in a vertical pipe with or without chemical absorption

CO2 bubbly pipe flows with or without chemical absorption were measured to obtain spatial evolution of dissolving bubbly flows. The experiments were carried out using pure water and aqueous NaOH solution of pH = 13 at two gas volume fluxes. The spatial evolutions of flow patterns, mean void fractions and bubble diameter distributions were obtained using an image processing method. The enhancement factor correlation proposed in our previous study was implemented into a three-dimensional one-way bubble tracking method to examine its applicability to CO2-water bubbly flow with chemical absorption. The numerical prediction agreed well with the measured spatial evolutions with or without chemical absorption, which confirmed the applicability of the enhancement factor correlation to bubbly pipe flows.

Incorporating truncated fractal distribution into Maxwell model to quantify thermal conductivity and its uncertainty in heterogeneous multiparticle systems

An approach is developed to examine the mean and uncertainty of thermal conductivity of a heterogeneous multiparticle system, where the particle concentration or void fraction is treated as a truncated fractal distribution. The truncated fractal distribution is then integrated into the Maxwell model, which is equivalent to a cell model in which the multiparticle system is conceptualized as a spherical fluid cell that envelopes a solid particle. The developed mean thermal conductivity is compared with four experimental data sets of liquid-saturated media from the literature. The effect of fractal characteristics is quantified and discussed. Incorporating particle concentration or void fraction truncated fractal distribution can better capture scatters in the experimental results. The thermal conductivity and its standard deviation decrease with increasing fractal dimensions. When the void fraction is truncated fractal, the uncertainty increases mostly in the low mean void fraction range and drops more quickly with the increasing mean void fraction compared to the case where the particle concentration is truncated fractal. In a typical case of multiparticle system when the solid particles are more conductive than the fluid, the faster increase rate of standard deviation with the ratio of solid over fluid conductivities occurs when the mean void fraction is smaller.

Effect of Process Parameters on Void Distribution, Volume Fraction, and Sphericity within the Bead Microstructure of Large-Area Additive Manufacturing Polymer Composites.

Short carbon fiber-reinforced composite materials produced by large-area additive manufacturing (LAAM) are attractive due to their lightweight, favorable mechanical properties, multifunctional applications, and low manufacturing costs. However, the physical and mechanical properties of short carbon-fiber-reinforced composites 3D printed via LAAM systems remain below expectations due in part to the void formation within the bead microstructure. This study aimed to assess void characteristics including volume fraction and sphericity within the microstructure of 13 wt% short carbon fiber acrylonitrile butadiene styrene (SCF/ABS). Our study evaluated SCF/ABS as a pellet, a single freely extruded strand, a regularly deposited single bead, and a single bead manufactured with a roller during the printing process using a high-resolution 3D micro-computed tomography (µCT) system. Micro voids were shown to exist within the microstructure of the SCF/ABS pellet and tended to become more prevalent in a single freely extruded strand which showed the highest void volume fraction among all the samples studied. Results also showed that deposition on the print bed reduced the void volume fraction and applying a roller during the printing process caused a further reduction in the void volume fraction. This study also reports the void's shape within the microstructure in terms of sphericity which indicated that SCF/ABS single freely extruded strands had the highest mean void sphericity (voids tend to be more spherical). Moreover, this study evaluated the effect of printing process parameters, including nozzle temperature, extrusion speed and nozzle height above the printing table on the void volume fraction and sphericity within the microstructure of regularly deposited single beads.

Phase-resolved characteristics of bubbles in cloud cavitation shedding cycles

To investigate the complex physics and mixture properties inside sheet/cloud cavities, we performed an experimental study that used phase-resolved optical probes and high-speed photography to acquire both vapor-water information and large-scale flow structures. We found distinctive characteristics at different scales: the large scale of cavitation shedding, and the small scale of bubbles. Large-scale cavitation behavior was examined using the mean void fraction profile and raw signal history, characterized by the shedding of cavity cloud. Small-scale information on bubbles and probability density function of bubble size distributions were quite similar at various measurement locations. Based on the experimental data, we proposed an empirical bubble size distribution and discussed the corresponding statistical quantities for cloud cavitation.

PD38-01 FEASIBILITY, SAFETY AND EFFICACY RESULTS OF THE SUFU FOUNDATION OPEN LABEL CLINICAL TRIAL OF ULTRASOUND CONFIRMED TRANSVAGINAL BOTULINUM TOXIN A (BTA) FOR REFRACTORY OVERACTIVE BLADDER (OAB)

You have accessJournal of UrologyCME1 May 2022PD38-01 FEASIBILITY, SAFETY AND EFFICACY RESULTS OF THE SUFU FOUNDATION OPEN LABEL CLINICAL TRIAL OF ULTRASOUND CONFIRMED TRANSVAGINAL BOTULINUM TOXIN A (BTA) FOR REFRACTORY OVERACTIVE BLADDER (OAB) Sean W. Berquist, Chen Shenhar, Stefanie van Uem, Ashu Mohammad, Abdelrahman S. Abdalla, Craig V. Comiter, Raveen Syan, Eboo Versi, and Amy D. Dobberfuhl Sean W. BerquistSean W. Berquist More articles by this author , Chen ShenharChen Shenhar More articles by this author , Stefanie van UemStefanie van Uem More articles by this author , Ashu MohammadAshu Mohammad More articles by this author , Abdelrahman S. AbdallaAbdelrahman S. Abdalla More articles by this author , Craig V. ComiterCraig V. Comiter More articles by this author , Raveen SyanRaveen Syan More articles by this author , Eboo VersiEboo Versi More articles by this author , and Amy D. DobberfuhlAmy D. Dobberfuhl More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000002596.01AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: To address challenges associated with delivering botulinum toxin A (BTA) via traditional cystoscopy for refractory overactive bladder (OAB), the SUFU Foundation sponsored a pilot clinical trial to determine feasibility, safety and efficacy of transvaginal intradetrusor BTA. METHODS: Women with refractory OAB were prospectively enrolled (March 2019 to June 2021) and underwent transvaginal ultrasound to confirm anatomy of the trigone and bladder. Ultrasound was removed and transvaginal intradetrusor BTA injection (Botox® 100 units) was performed under direct visualization via half speculum. Repeat ultrasound was performed to confirm correct delivery of BTA. Prospective feasibility, safety and efficacy outcomes were recorded. Treatment benefit scale (TBS) and patient global impression of change (PGIC) were recorded at 6 and 12 weeks. After 12 weeks subjects were eligible for the continuity phase and repeat BTA injection at time of symptom recurrence (PGIC <50% improved) to determine inter-injection interval duration of effect. Covariates were recorded at each study visit: AUASS, OABq-SF SB & QOL, 3-day bladder diary. Data are presented as mean±SD, and analyzed in SAS by repeated measure ANOVA. RESULTS: Women (n=15, age 67±8 yr, BMI 27.5±5.2, medical comorbidities 4.5±2.6) underwent a total of 31 BTA injections, and were previously treated with 1.8±0.9 1st/2nd line, and 0.7±0.9 3rd line OAB treatments. Feasibility was demonstrated by all subjects completing BTA injection [procedure pain score 2.5±1.6 (0–10 scale)]. Ultrasound confirmed correct BTA delivery in all subjects. Safety was demonstrated by 0% immediate procedural complication, 0% rate of retention and 3% rate of UTI. Prior to 12 week follow-up, 2 subjects were lost, and 1 died of unrelated causes. 75% of subjects reported significant improvement at 6 weeks and 58% reported improvement at 12 weeks. There was significant improvement in AUASS, OAB-qSF SB & QOL total scores on ANOVA [F(1,11)=5.02, p=0.04; F(1,11)=7.14, p=0.02 & F(1,11)=8.4, p=0.01]. Mean void volume on diary significantly increased by 6 weeks [F(1,10)=6.2, p=0.03]. Eligible subjects were enrolled in the continuity phase and demonstrated an inter-injection interval of 18.9±9.6 weeks. CONCLUSIONS: Transvaginal BTA for refractory OAB appears to be a simple, feasible, safe, and efficacious procedure, with a mean inter-injection duration of effect greater than 18 weeks, when administered in an open label clinical trial. Source of Funding: SUFU Foundation © 2022 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 207Issue Supplement 5May 2022Page: e645 Advertisement Copyright & Permissions© 2022 by American Urological Association Education and Research, Inc.MetricsAuthor Information Sean W. Berquist More articles by this author Chen Shenhar More articles by this author Stefanie van Uem More articles by this author Ashu Mohammad More articles by this author Abdelrahman S. Abdalla More articles by this author Craig V. Comiter More articles by this author Raveen Syan More articles by this author Eboo Versi More articles by this author Amy D. Dobberfuhl More articles by this author Expand All Advertisement PDF DownloadLoading ...

Air–water flow properties in hydraulic jumps on rough pebbled bed

ABSTRACT In open channel flows, a hydraulic jump is a rapid shift from a supercritical flow to a subcritical flow with a sharp rise in the elevation of the free surface, which is associated with strong energy dissipation, air entrainment, and spray. The present research aims to investigate the air–water flow properties in a hydraulic jump on rough pebbled bed. A range of discharges from 0.06 to 0.1 m3/s, corresponding to inflow Froude numbers Fr 1 between 1.7 and 2.84 and Reynolds numbers Re 1 from 140,000 to 220,000 were considered. The basic parameters of two-phase flow such as the void fraction and bubble count rate are presented. Close to the jump toe, the mean void fraction on rough bed was larger than on smooth bed, while farther downstream larger magnitudes were observed on smooth bed. No significant difference was observed between rough and smooth beds in terms of the maximum void fraction. In the turbulent shear layer, the bubble count rate was comparatively larger on rough bed than on smooth bed, while the longitudinal distribution decayed for both bed configurations.

Reduction of skin friction and two-phase flow structure beneath wall in horizontal rectangular channel

From the viewpoint of the improvement of the air lubrication method for the ship's hull resistance reduction, an experimental study was conducted for two-phase flow in a horizontal rectangular channel with a length of 3.0 m, a gap of 0.05 m, and a width of 0.2 m, which simulates the external two-phase flow. The database on frictional drag and local two-phase flow parameters, including void fraction profile and gas chord length, was collected using a shear stress sensor and a double sensor probe. Measurement of two-phase flow structure was performed at three axial positions of z = 0.930, 1.43, and 1.93 m from the bubble injection port. The wall shear stress was obtained at z = 1.93 m. A total of 72 datasets are acquired a room temperature and at flow conditions of superficial liquid velocity <jf> ranging from 0.832 to 3.00 m/s and superficial gas velocity <jg> ranging from 0.0232 to 0.714 m/s. The effects of entry length, liquid and gas flow rates on the phase distribution characteristics beneath the wall were discussed. The bubble layer thickness was newly defined as the length scale. The bubble layer thickness was not so sensitive to the changes in the liquid flow rates and the entry length, and highly dependent on the gas flow rates in the present experimental conditions. The mean void fraction in the bubble layer was highly reliant on the liquid flow rate and decreased with the superficial liquid velocity. In contrast, the insignificant effect of gas flow rate on the mean void fraction was confirmed. A strong correlation between the drag reduction effect due to the air lubrication and the mean void fraction in the bubble layer was confirmed. The obtained data are expected to be used for the modeling of the interfacial area transport terms, development of the constitutive equations of the drift flux model, modeling of the drag reduction for the external two-phase flow and the benchmark tests of various CFD codes in the future study.

Fracture surface topography investigation and fatigue life assessment of notched austenitic steel specimens

The objectives of this study were to investigate the fracture surface topography of X8CrNiS18-9 austenitic stainless-steel specimens for different loadings and notch radii and to supplement the knowledge about the fracture mechanisms for fatigue performance. Cases with three different values of the notch radius ρ and the stress amplitude σa were analysed. The fracture topographies were quantified by the areas over their entire surfaces with the aid of an optical confocal measurement system. The results showed a well-correlated root mean square height Sq and void volume Vv, identifying the characteristics of the entire fracture method. A fracture surface topography fatigue damage model was developed based on the product of the stress amplitude σa by the Sq to the Vv ratio. Overall, the predictions were close to the fatigue lives found in the experiments.

Radiological Analysis of Gentamicin Eluting Synthetic Bone Graft Substitute Used in the Management of Patients With Traumatic Bone Voids.

BackgroundManagement of traumatic bone voids has always been challenging. Gentamicin eluting synthetic bone graft substitute (Cerament-G) showed encouraging results in achieving good bone healing with a satisfactory degree of resorption when utilised as a void filler. This study aims to assess the radiological signs of Cerament-G remodelling when used for patients with traumatic bone voids.MethodsRetrospective data analysis of all patients admitted to our unit between 2015 and 2021 with traumatic bone voids who had Cerament-G applied intraoperatively as a void filler. Postoperative radiographic images of the fracture site at six weeks, three months, six months, and at the final follow-up were reviewed. The radiological signs of Cerament-G integration, percent of void healing at the final follow-up were assessed.ResultsA total of 51 patients (52 fractures) were included in the study. Among them 10 were female and 41 were male with a mean age of 42.7 (11 - 90) years. The mean void size was 6.58 cm3. Mean follow-up duration was 9.73 months. Primary fracture union was achieved in 44 (86.3%) patients. Delayed union was reported in six (11.7%) patients, while one (1.9%) patient had non-union. Twenty-seven (52%) patients had >90% of void healing with normal trabecular bone. Twenty (38.5%) patients had 50-90% void healing with normal bone. Whereas only five (9.5%) patients had less than 50% of void healing.ConclusionCerament-G used as a void filler for patients with traumatic bone void has resulted 98% fracture union rate with good signs of radiological remodelling into a trabecular bone. More than 50% void filling with new trabecular bone was reported in more than 90% of patients. Non-union was reported in only one patient.

Cosmic voids in GAN-generated maps of large-scale structure

A Generative Adversarial Network (GAN) was used to investigate the statistics and properties of voids in a ΛCDM universe. The total number of voids and the distribution of void sizes is similar in both sets of images and, within the formal error bars, the mean void properties are consistent with each other. However, the generated images yield somewhat fewer small voids than do the simulated images. In addition, the generated images yield far fewer voids with central density contrast ∼−1. Because the generated images yield fewer of the emptiest voids, the distribution of the mean interior density contrast is systematically higher for the generated voids than it is for the simulated voids. The mean radial underdensity profiles of the largest voids are similar in both sets of images, but systematic differences are apparent. On small scales (r<0.5rv), the underdensity profiles of the voids in the generated images exceed those of the voids in the simulated images. On large scales (r>0.5rv), the underdensity profiles of the voids in the simulated images exceed those of the voids in the generated images. The discrepancies between the void properties in the two sets of images are attributable to the GAN struggling to capture absolute patterns in the data. In particular, the GAN produces too few pixels with density contrasts ∼−1 and too many pixels with density contrasts in the range ∼−0.88 to ∼−0.63.