Inlet Diameter Research Articles

The Utility of Mid-Pelvic Dimensions Via Plain Radiography in Predicting Cesarean Delivery

Introduction: Studies on the role of pelvimetry in predicting the mode of delivery have yielded mixed results. The aim of this study is to determine utility of the mid-pelvic measurement in predicting the mode of delivery in a cohort of women attempting vaginal delivery.
 Study Design and Methods: With this prospective cohort study, we evaluated the use of x-ray in predicting the delivery outcome of women attempting to deliver vaginally. Women were recruited before labor at >36 weeks gestational age and X-ray pelvimetry was performed after delivery. The exposures of interest were mid pelvic measures including anteroposterior diameters, transverse diameters and circumferences. The outcome measures were whether the women delivered via vaginal route or had cesarean delivery. We estimated the distribution and calculated measures of central tendency and spread of each pelvic dimension. Area under the receiver-operating characteristics curve (AUC) was used to estimate the overall predictive ability for each pelvic dimension and the optimal cut-point was estimated using the method of Liu. Logistic regression analysis was used to identify independent predictors for mode of delivery. The Hosmer – Lemeshow goodness-of-fit test was used to estimate the overall fit while the AUC was used to estimate the overall prediction of the final model.
 Results: A total of 426 women met the inclusion criteria. The mean gestational age at delivery was 40 (±6.0) weeks and the majority were black parturient (62.6%0. A slight majority were nulliparous (52.1%). In all, 127 women (29.8%) were delivered by cesarean delivery. All the pelvic inlet and mid pelvic dimensions were approximately normally distributed. The AUC ranged from 0.62 to 0.86. While the pelvic inlet and mid pelvic diameters had equivalent AUC, the optimal cut-point of the mid pelvic anteroposterior diameter (10.8cm) had both higher sensitivity and specificity than the pelvic inlet anteroposterior diameter (10.2cm) (95% and 85% versus 90% and 80%, respectively). There was an inverse relationship between the mid pelvic anteroposterior diameter and mode of delivery by cesarean section, with a 100% risk among women with a diameter of 9cm or less. However, the multivariable model developed had an AUC of 0.90, indicating overall good and higher predictive ability than the mid-pelvic anteroposterior diameter alone.
 Conclusions: In this large cohort study, the mid pelvic anteroposterior diameter best predicted mode of delivery by cesarean section.

Detailed performance analysis of parabolic trough collectors including geometric effect

Parabolic trough collectors (PTCs) have been known for years as one of the leading methods for extracting energy from the sun. In the present work, the performance of PTCs was investigated. However, its performance needs some improvement to be integrated in more and wide range of applications. This idea motivated the author to investigate the performance of parabolic trough collectors in detail. Thus, in the present work, the performance of parabolic trough collectors is investigated. The effect of eight geometric and inlet variables on the PTC performance was evaluated. Two performance factors , the temperature difference and thermal efficiency, were selected. The effect of inlet condition, including inlet mass flow rate and inlet flow temperature reflector geometry, including reflector length and width,receiver diameters, including inlet and outlet reciever diameters, and cover diameters, including the inlet and outlet cover diameters on these PFs was assessed. Eight thermal working fluids were considered. A non-linear mathematical model was developed for PTC and implemented into MATLAB code where an iterative technique was used to conduct the present analyses. Level curves were generated to study the PTC key performance parameters. The curves revealed that the maximum values of the PFs and maximum range of change in these PFs occurred when the inlet conditions were varied. Changes in the inlet temperature, and changes in the reflector geometry yielded the highest and second-highest values. The cover geometry had the minimum effect on the PFs. Moreover, the best maximum efficiency, best maximum temperature difference, and maximum range of efficiency change were obtained for water, air, and carbon dioxide, respectively. The effect of inlet temperature is more significant than the mass flow rate effect on the thermal efficiency, whereas this effect is reversed in case of the temperature difference, by which the mass flow rate exerts the least influence on the temperature difference.

Yakınsak-Konik Nozulların Giriş ve Çıkış Çaplarının İtme Kuvveti ve Hacimsel Debi Üzerindeki Etkisinin Teorik, Nümerik ve Deneysel İncelemesi

It is possible to see convergent conical type nozzles everywhere, from daily life to rocket science. They are utilized as the main part of the propulsion system in many applications such as air blow guns for spraying, steam turbines for compression, rockets for thrust generation, satellites for altitude control and so on. Although the convergent conical nozzle is a well-known nozzle, there are few studies on the effects of geometric changes by comparing more than one approach together. Therefore, this study investigates thrust and volumetric flow rate for different inlet and exit diameters of the convergent conical nozzles theoretically, numerically and experimentally. In this study, the quasi-one-dimensional Euler equations are defined for the theoretical investigation of convergent conical nozzles. However, in this approach, many important features such as viscous losses are neglected. In fact, nozzle flows have highly complex features including shock waves, turbulence, and boundary layers due to compressible effects. Thus, Computational Fluid Dynamic (CFD) simulations are performed with ANSYS Fluent for numerical investigation of the nozzle in this study. CFD simulations provide a better understanding and illustration of convergent conical type nozzle flows. For a third approach, the experimental investigation is conducted for thrust and volumetric flow rate measurements. Theoretical and numerical results are compared with the experimental results and similarity ratios are defined to find the closest to the experimental results.

Effect of Feed Materials on Pellet Properties, Capacity and Energy Consumptions Values

In this study, it was aimed to determine the power consumption, work capacity and some properties of the pellet feed of the pelletizing machine used in the pelleting of animal feeds consisting of small and granular mixtures.
 A pellet machine with a die hole inlet diameter of 8 mm, an outlet diameter of 5 mm and a flat die with a diameter of 195 mm was used to pellet the feeds. In the experiments, two different feed materials consisting of mixed feed and barley only were used. The bulk weight of the pellets (kg m-3), durability (%), compression resistance (N mm-2), pellet moisture (%) were determined. In addition, hourly pelleting capacity (kg h -1), required energy consumption (kW), specific energy consumption (kW kg -1) of the pelletizing machine were determined.As a result of the trials, the capacity of the pellet feed making machine was 172.80 kg h-1 in the pelleting process from barley and 170 kg h-1 in the pelleting process from mixed feed. The required electrical energy consumption was 7.63 kW, in barley pelleting and 9.18 kW in mixed feed pelleting. Specific energy consumption 0.044 kW kg-1 in barley pelleting, 0.054 kW kg-1 in mixed feed pelleting

Optimization of a novel impulse gas turbine nozzle and blades design utilizing Taguchi method for micro-scale power generation

This study is conducted to optimize the nozzle and blade of a compact non-combustion impulse gas turbine driven by the pressurized gas line with Computational Fluid Dynamics (CFD) approach and Taguchi method. For nozzle, throat diameter, nozzle inlet and outlet diameter and convergent-divergent length were investigated. Meanwhile, number of blades, blade radius, blade curvature angle, blade thickness and surface roughness were evaluated for blade. An L25 orthogonal array was chosen for both optimizations. Once optimized, the corresponding operating envelope was identified and compared against the original turbine. When operating at flow rate of 1.2MMSCFD and pressure of 69 bar, the turbine with optimized nozzle produces a maximum power output of 4383.59W at 5500 rpm, while with optimized blades produce 2058.64W at 5000 rpm. Combining optimized nozzle and blades produced 4928.64W at 6000 rpm. These produced powers are significantly higher than the original turbine maximum power of 1743.81W at 4500 rpm. This indicates potential performance enhancement of the turbine by optimizing its blade and nozzle geometry which is useful for its implementation on the offshore platform. To fully utilize this potential enhancement, the electric generator attached to the turbine shall be fine-tuned to have peak power at the optimum rpm band of the optimized turbine.

Experimental Investigation of Flow Parameters in a Mild Curved S-shaped Diffusing Duct

The paper presents a detailed study of the performance of fully developed subsonic turbulent flow in a circular cross-section S-shaped centerline-diffusing duct. A precalibrated 5-hole pressure probe was used for the measurements. The diffuser cross-section was expanded to 2.25 area ratio (Ar) at the exit. The duct was fabricated by joining two 22.5º bends of curvature ratio (βt) 11.46 in reverse direction with a centerline offset of 0.2 of the axial length of the diffuser. The test was carried out with inlet Re=8.4x105, calculated based on diffuser inlet diameter. The experimental results indicated the generation of secondary flow in the form of a pair of counter rotating vortices in the first half, which changes its senses of rotation in the second half. The overall static pressure recovery of the diffuser was 40%.

Structure optimization and fertilizer injection performance analysis of a non‐axisymmetric Venturi injector

AbstractTo improve the fertilizer injection performance of a non‐axisymmetric Venturi injector (NAVI), the effects of the contraction angle, diffusion angle, throat diameter and tilt angle of the injection pipe on the fertilizer injection performance of NAVI were examined. Based on the test, the original NAVI was optimized, and the fertilizer injection performance of NAVI before (F1) and after (F2) optimization was compared. Then, a non‐axisymmetric Venturi injector with arc diffusion (F3) was proposed. The results showed that when the water inlet diameter of the non‐axisymmetric Venturi injector was 25 mm, the optimal structural parameters were as follows: the contraction angle was 40°, the diffusion angle 6°, the throat diameter 7 mm and the tilt angle of the injection pipe was 120°. Compared with F1, the injection rate and fertilizer injection efficiency of F2 increased by 21–66 and 27–79%, respectively. Changing the diffusion section of NAVI into an arc structure was conducive to reducing the vortex area size by 11% and improving the injection rate by 20–62%. The results can provide an important reference for the structural design of Venturi injectors.

Characterization of Biogas as an Alternative Fuel in Micro-Scale Combustion Technology

This study observes the flame characteristics of the biogas in micro/meso-scale (MSC) combustion technology, namely in a cylindrical MSC. For comparison, the fuel and combustor variations were carried out with backward-facing step size (bfs) as the flame holder in the combustor.The bfs are varied by changing the combustor's length of the inlet diameter. However, the size of the outlet diameter of the combustor is always constant to obtain a continuous combustion reaction zone. Biogas/methane (CH4), butane gas (C4H10), and a mixture of biogas-butane are used as fuel, with air as the oxidizing agent. The results showed that the type of fuel, reactant flow velocity, and equivalent ratio that occurred in the fuel variation and the bfs variation of the cylindrical msc influenced the flame characterization. Stable flame forms in the stoichiometric to rich equivalent ratio area and the medium to high reactant velocity area. The result shows that the equivalent ratio (φ) is 1.23 –1.44, the flame stability limit at the combustor ratio of 0.7, and biogas fuel has low flame stability compared to butane and the biogas-butane mixture. Moreover, the flame can be stable on butane fuel in the equivalent ratio (φ) 0.85 –1.43 and (φ) 0.86 –1.19 for the biogas-butane fuel mixture. Furthermore, when the D1/D2 increases, the flame stability of biogas tends to be wider than when the combustor ratio is 0.7, where the equivalent ratio (φ) is 0.98 –1.42. The result also shows that the flame can be stable on butane fuel in the equivalent ratio (φ) 0.71 –1.43, and for the biogas-butane fuel mixture, the flame can be stable in the equivalent ratio (φ) 0.69 –1.32. However, the best characterization of biogas combustion is formed in the variation of biogas treatment by mixing butane gas (biogas-butane). One of the methods used is called with a wider flame stability limit area. More varied flame visualization variations with a more widely distributed flame mode map, flame, and combustor wall temperature. The result shows that the combustor wall temperature of butane is around 225-250 °C, higher than the characterization of biogas combustion around 150°C, where it's without mixing butane gas for the possible test ranges.

Mean Flow Characteristics Downstream of a Vortex Tube Separator Array

Vortex tube separator (VTS) arrays are used to filter foreign particles from turboshaft engine intakes. Arrays may consist of hundreds of separators that share a common surrounding plenum, potentially allowing for significant interactions between the devices. However, most VTS studies have been limited to individual separators acting alone. The current study first involves an experimental investigation of the fluid flow emerging from the outlets of a VTS array installed in a wind tunnel. Particle image velocimetry is used to measure the flowfield at planes , , and downstream of the outlets, where is the inlet tube diameter of a separator. The results indicate that the emerging vortices quickly merge into a single vortex with high circumferential velocity concentrated near the edges of the duct, and that a central recirculation zone (CRZ) develops. This is in contrast to the flow from a single VTS, which does not have a clear CRZ. Comparisons to similar combustion swirler flows lead to the hypothesis that VTS arrays may uniquely generate fast-developing CRZs that produce strong axial flow gradients near or even within some VTS outlets. Such gradients will alter the filtration performance of affected VTSs, which is highly sensitive to flow rates. To explain the onset of recirculation that is exclusive to the array configuration, the framework of a momentum integral model has been developed and is presented here. Additionally, computer-aided design files of the experimental geometry along with inlet/outlet boundary conditions are being made available for any future computational validation studies of this complex flowfield.

Value of the newly developed pelvic dimension index/prostate volume ratio in predicting positive surgical margin in prostate cancer.

To evaluate the diagnostic performance of pelvimetric measurements, in particular the pelvic dimension index (PDI)/prostate volume (PV) ratio (PDI/PV), in predicting positive surgical margin (PSM) in prostate cancer (PC). 127 patients who had pre-operative pelvic imaging were included in this study. Demographic and clinical data were recorded. Apical depth (AD), interspinous distance (ISD), intertuberous distance (ITD), bony femoral width (BFW), soft-tissue width (SW), symphysis angle (SA), anteroposterior diameter of the pelvic inlet (API), anteroposterior diameter of the pelvic mid-plane (APM), anteroposterior diameter of the pelvic outlet (APO), pelvic depth (PD), bony width index (BWI), soft tissue width index (SWI), pelvic cavity index (PCI), PDI and PV were measured on MRI or CT. Using PDI and PV, we developed a new parameter of "PDI to PV ratio" (PDI/PV). Logistic regression analysis was used to determine the predictive potential of variables in detection of PSM. The AD, PV, SA and total prostate specific antigen (PSA) were significantly higher in PSM( +), while PDI, BWI, SWI, API, PDI/PV and PD were significantly lower in PSM( +) (p< 0.05). In multivariate analysis, PDI/PV ratio and clinical stage were all significant predictor of PSM, where PDI/PV ratio was the strongest predictor, followed by clinical stage. Pelvimetric measurements indicating deep location of the prostatic apex rather than pelvic width are more effective in predicting PSM. Prediction of PSM with pelvimetric measurements, in particular PDI/PV ratio, may be helpful for surgical planning in preoperative period.

Development and validation of a nomogram for predicting operating time in laparoscopic anterior resection of rectal cancer.

The goal of this study is to create and verify a nomogram estimate operating time in rectal cancer (RC) patients based on clinicopathological factors and MRI/CT measurements before surgery. The nomogram was developed in a cohort of patients who underwent laparoscopic anterior resection (L-AR) for RC. The clinicopathological and pelvis parameters were collected. Risk factors for a long operating time were determined by univariate and multivariate logistic regression analyses, and a nomogram was established with independent risk factors. The performance of the nomogram was evaluated. An independent cohort of consecutive patients served as the validation dataset. The development group recruited 159 RC patients, while 54 patients were enrolled in the validation group. Independent risk factors identified in multivariate analysis were a distance from the anal verge <5 cm (P = 0.024), the transverse diameter of the pelvic inlet (P < 0.001), mesorectal fat area (P = 0.017), and visceral fat area (P < 0.001). Then, a nomogram was built based on these four independent risk factors. The C-indexes of the nomogram in the development and validation group were 0.886 and 0.855, respectively. And values of AUC were the same with C-indexes in both groups. Besides, the calibration plots showed satisfactory consistency between actual observation and nomogram-predicted probabilities of long operating time. A nomogram for predicting the risk of long operating duration in L-AR of RC was developed. And the nomogram displayed a good prediction effect and can be utilized as a tool for evaluating operating time preoperatively.

Thermal Performance Optimization of Integrated Microchannel Cooling Plate for IGBT Power Module.

In high-integration electronic components, the insulated-gate bipolar transistor (IGBT) power module has a high working temperature, which requires reasonable thermal analysis and a cooling process to improve the reliability of the IGBT module. This paper presents an investigation into the heat dissipation of the integrated microchannel cooling plate in the silicon carbide IGBT power module and reports the impact of the BL series micropump on the efficiency of the cooling plate. The IGBT power module was first simplified as an equivalent-mass block with a mass of 62.64 g, a volume of 15.27 cm3, a density of 4.10 g/cm3, and a specific heat capacity of 512.53 J/(kg·K), through an equivalent method. Then, the thermal performance of the microchannel cooling plate with a main channel and a secondary channel was analyzed and the design of experiment (DOE) method was used to provide three factors and three levels of orthogonal simulation experiments. The three factors included microchannel width, number of secondary inlets, and inlet diameter. The results show that the microchannel cooling plate significantly reduces the temperature of IGBT chips and, as the microchannel width, number of secondary inlets, and inlet diameter increase, the junction temperature of chips gradually decreases. The optimal structure of the cooling plate is a microchannel width of 0.58 mm, 13 secondary inlets, and an inlet diameter of 3.8 mm, and the chip-junction temperature of this structure is decreased from 677 °C to 77.7 °C. In addition, the BL series micropump was connected to the inlet of the cooling plate and the thermal performance of the microchannel cooling plate with a micropump was analyzed. The micropump increases the frictional resistance of fluid flow, resulting in an increase in chip-junction temperature to 110 °C. This work demonstrates the impact of micropumps on the heat dissipation of cooling plates and provides a foundation for the design of cooling plates for IGBT power modules.

A strategy for regulation of gas–liquid microflow patterns by changing gas kinetic energy

Controllable regulation of gas–liquid microflow pattern and bubble size is significant to bubble-based microfluidics, but it is hard to be realized with the existing technologies. Accordingly, this work reports a convenient strategy that changes the gas kinetic energy to controllably regulate the microflow patterns from Taylor flow to short bubble flow and bubbly flow. Results exhibit that the desired flow patterns and bubble size can be effectively obtained by varying the gas inlet size to change gas kinetic energy, and a much wider bubbly flow regime which could not be reached normally in conventional T-junction microchannels is easily obtained. Besides, from the bubble’s characteristic width and length, the behaviors of the bubble generation in different T-junctions were compared to reveal the mechanism behind the generation of bubbles. Importantly, as the hydraulic diameter of the gas inlet decreases from 365.0 to 50.0 μm, the dominative factors on the bubble generation transfer mainly from the liquid phase to both the two-phases because the gas–liquid Weber number ratio increases from 6.6 × 10−5–5.4 × 10−3 to 4.2 × 10−2–3.4. Finally, the parameter of the two-phase Weber number ratio is the first time introduced to the unified prediction model for bubble generation frequency.

Numerical Simulations of Swirling Water Jet Atomization: A Mesh Convergence Study

We report on numerical simulations of a swirling water jet flowing out of a nozzle into a still air atmosphere at normal conditions. Primary jet breakup and atomization were studied with an emphasis on the effect of grid resolution on the results. Jet inlet diameter D was set to 0.8 mm, a bulk velocity was set to 7.6 m/s (Re=6100, Wel=650), and the swirl rate was set to S=0.3. The near region of the jet (up to x/D=16) was studied. The results were obtained for four different grid resolutions with the smallest cell size of 6 μm. It is shown that the use of an adaptive mesh refinement procedure for interface tracking allows us to get to convergent results in terms of both droplets volume and surface area distributions, while the total number of droplets changes with the increased grid refinement level. This phenomenon may be attributed to the formation of small (grid-cell sized) droplets due to numerically-triggered instabilities at the gas-liquid interface.

Experimental Study of the Influence of the Geometrical Parameters of the Radial Labyrinth Pump on the Pump’s Operating Parameters and Performance

Centrifugal pumps are the most common machines responsible for the increase in hydraulic energy in a piping system. Their proper design, operation, and maintenance have a strong influence on the performance of technological processes carried out in many industrial units. For the ultra-low specific speed (nq &lt; 10) application, there is no economical reason for these pumps to be used. This is caused by an increase in internal losses in the pump. The article concerns the problem of the hydraulic operation of a new type of labyrinth pump—the radial labyrinth pump (RLP), which is a developed axial unit. The main research method involves the experimental research of hydraulic sets consisting of passive and active discs. The analyses were preceded by dimensional analysis and experimental planning. The study investigates the influence of a chosen structural parameter of both discs on the process of energy conversion obtained in the pump. The influence of parameters such as number, depth and width of the grooves, as well as inlet angle and diameter on the properties of the pump was studied and discussed in detail. The essential novelty of the article is the recognition of the hydraulic performance of the RLP with grooved discs. To extend the scope of the conducted research for the chosen hydraulic sets, a comparison of the mutual cooperation of an active disc with a smooth and grooved passive one was conducted. It was identified that not every geometric relationship of the parameters of the active and passive discs results in an increase in head with respect to cooperation with a smooth passive disc (motionless). The highest head and high efficiencies were obtained for sets with short channels with large inlet diameters—zk12 and zk13—ratios for zk12 d1ap/d2ap = 0.78, and for zk13 zk12 d1ap/d2ap = 0.81. Based on the obtained results, preliminary recommendations for the construction were made.

Adjustment of the Coarse Grain Problem of the Horizontal Continuous Casting Slab by Optimizing the Crystallizer Structure

This paper mainly focuses on the problem of coarse grain on the bottom surface of the red copper horizontal continuous casting billet, and tries to thicken the bottom end of the crystallizer by combining numerical simulation and industrial experiment, and indirectly improves the cooling strength of the bottom surface of the casting billet to solve the problem of grain coarseness. The results show that the optimum diameter of the lower inlet of the copper sleeve was 14.2 mm, when the diameter of the inlet increased from 11 mm to 14.2 mm, the cooling intensity of the lower part of the casting billet gradually increased, and the grain on the lower surface was significantly refined; and with the increase of the diameter of the water inlet, the average width of the columnar grain decreased from 1.94 mm to 1.64 mm, the grain size decreased, and the number of grains increased.

Experimental investigation and optimization of modification during backside-water-assisted laser drilling using flowing water

Backside-water-assisted laser drilling (BWALD) is a laser drilling process in which the workpiece is partially submerged in water. The backside of the workpiece is surrounded by water, and its upside directly contacts the air. In this study, flowing water was used to solve the problem where the generated air bubbles and debris prevent water from penetrating the through-hole and achieve the fabrication of micro-holes with high aspect ratios via BWALD. Moreover, a two-step micro-hole processing strategy was proposed to divide the BWALD into punching-through and modification steps. The modification process is the key to improve the machining performance, but involves numerous processing parameters. So, the effects of modification parameters (pulse energy, modification speed, frequency and number of modifications) on the responses of the micro-hole diameters and roundness were investigated during BWALD using flowing water on the basis of the response surface methodology (RSM). To achieve the optimal combination of parameters for a given situation, the regression models for the inlet diameter, outlet diameter, inlet roundness and outlet roundness of the modified micro-holes were developed. The adequacies of the developed models were subsequently verified by the analysis of variance (ANOVA) method. Finally, the well-rounded micro-hole with an inlet diameter of 105.62 μm and an outlet diameter of 96.65 μm which taper was only 0.21° was obtained with the optimum modification parameters: pulse energy of 15.9 μJ, frequency of 52.9 kHz, modification speed of 4.7 mm/s and number of modifications of 313.

Investigation on the noise induced by gas–liquid two-phase flow in a capillary tube

In order to research the noise generated by gas–liquid two-phase flow within capillary tubes in refrigeration systems, this study employs a numerical simulation method based on the volume of fluid model and evaporation-condensation model. The noise of gas–liquid two-phase flows is generated by refrigerant vaporization in capillary tubes under different inlet temperatures and diameters. The results of this study showed that two-phase flow noise in capillary tubes predominantly exists in the frequency range of 0–200 Hz, corresponding to low-frequency noise. Under different inlet temperature and diameter conditions, the total sound pressure level (TSPL) of a two-phase flow noise increased with the increase in the capillary tube diameter. Moreover, when the inlet temperature was 316.6 K, as the diameter increased from 1 to 1.9 mm, TSPL increased from 32.02 to 34.36 dB. In addition, as the inlet temperature gradually decreased, TSPL increased. Furthermore, it was found that the lower the inlet temperature, the greater the increase in TSPL. When the inlet temperatures were 316.6, 313.6, 310.6, and 307.6 K, and the diameter increased from 1 to 1.9 mm, TSPL increased by 2.34, 3.41, 4.1, and 5.38 dB, respectively, corresponding to the relative increase of 7.31%, 10.23%, 11.85%, and 15.34%. Finally, using an orthogonal analysis, a criterion relationship was obtained for predicting the TSPL of gas–liquid two-phase flow noises in capillary tubes under different conditions. This study provides guidance for noise control and structural optimization of capillary tubes considering the gas–liquid two-phase flow.

Investigation of heavy gas dispersion characteristics in a static environment: Spatial distribution and volume flux prediction

The unexpected release of hazardous gases due to natural/industrial accidents or man-made disasters can have tragic consequences. Compared with other gaseous pollutants, heavy gases easily accumulate in personnel working areas and are more difficult to eliminate through existing mechanical ventilation systems. In this paper, to improve air quality in enclosed environments, the spatial characteristics of heavy gas dispersion were obtained based on an analysis of the basic properties of heavy gas dispersion. Schlieren experiments and image processing were conducted with shadow correction and noise reduction. The computational fluid dynamics (CFD) was used for predicting the dispersion of heavy gas. The numerical simulations cover a wide range of the densimetric Froude number (Fr) from 6.45 to 25.79, and a best-fit relation of Fr and the height of heavy gas fountain was provided. The radial velocity, radial density and axial density at cross-section of heavy gas dispersion were normalized using the unified scaling law. The axial density reached a minimum value at a height of 10 times the inlet diameter. Further decreases in the inertial force or decreases in the buoyant force can reduce the dilution of heavy gas by ambient fluids, which means that heavy gases diffuse faster and farther. An alternative method for estimating volume flux during gas dispersion using Fr was also proposed.

Hydraulic Calculations of a Telescopic Water Intake

Abstract Telescopic water intake structures allow for the selective intake of water from the top layers of a reservoir. A telescopic water intake has a high degree of mobility, and a wide field of application; at the same time, it is very simple and convenient to operate. Despite these advantages, an exact calculation method for a telescopic water intake is lacking (Lipin, 2020; Lipin, 2022). Therefore, the purpose of this research is to develop an exact calculation method for a telescopic water intake. In order to perform this task, all the structural elements of a telescopic water intake were analyzed separately by means of existing hydraulic principles. The impact of the critical submergence depth of the water intake funnel on the operability of a telescopic water intake was studied, and an equation for the critical submergence depth calculation was proposed. The optimal range of the flow rate coefficient ( μ =0.30 - 0.45) was proposed for calculating the funnel flow rate, and the correlation between the flow rate and funnel inlet diameter was defined. The optimal curvature radius of the elbow was proposed. In order to verify the above mentioned parameters and correlations, analytical and numerical calculations of specific examples were performed. The results of the numerical modelling demonstrated that the critical submergence depth and shape of the water intake funnel, as defined by the analytical calculations, ensured its effective operation free of cavitation and vortexes. The analytically calculated dimensions of the telescopic column, following the numerical modelling results, provided normal hydraulic conditions without active cavitation. According to the numerical modelling, the proposed curvature radius of the elbow was sufficient to avoid significant cavitation and vortex formation in the elbow structure. This research can provide guidance for the design of telescopic water intake structures.