Wall Orifice Research Articles

The application value of high-frequency ultrasound in the feasibility assessment of endoscopic retrograde appendicitis therapy in children with appendicitis

Acute appendicitis is one of the common acute abdominal diseases in pediatrics. However, the implementation of radiological examination guided endoscopic retrograde appendicitis therapy (ERAT) in adults is limited in children. Our previous research explored the non-invasive guidance of high-frequency ultrasound (HFUS) for ERAT and achieved good therapeutic effects. This study mainly focuses on exploring the application value of HFUS in the feasibility assessment of ERAT in children with appendicitis. 163 children with appendicitis received ERAT guided by HFUS were analyzed retrospectively. According to the parameters evaluated by HFUS before and during ERAT, the results indicated that the distance between the appendix orifice and the ileocecal valve significantly affected the time required for the guidewire to enter the appendix cavity (P < 0.05). The diameter and the texture of the fecalith, the thickness of the intestinal wall of the appendiceal orifice all had significant effects on the successful removal of the fecalith (P < 0.05). The success rate, treatment time and final flushing effect of the guidewire to reach the blind end of the appendix were significantly affected by the tortuosity of the appendix and whether there was adhesion with surrounding tissues (P < 0.05). HFUS can accurately assess the feasibility of ERAT in children with appendicitis.

Integration of a novel Chemical Looping Combustion reactor into a thermochemical energy storage system

This study analyses the performance of a back-up power process that uses a novel chemical looping packed bed air reactor to oxidize a batch of reduced solids while heating high pressure flowing air. In this arrangement, the solids are slowly oxidized by a diffusionally-controlled flow of oxygen perpendicular to the main air flow, thus imposing very long oxidation times for all reacting particles. A decay in the thermal power output of the reactor can be expected with time due to the increasing resistance to O2 diffusion towards the unreacted oxygen carrier particles as the reaction progresses. In this work, integration of the dynamic system formed by the reactor and the power plant used to produce power from the exploitation of the variable thermal output of the reactor is investigated. Different case studies are assessed for decarbonization of energy production and storage of renewable energy. The reactor is rated at a maximum 50 MWth power output in all cases, employing iron- or nickel-based particles as oxygen carrier. A simplified model for mass and heat transfer in the proximity of the wall orifices allows the definition of operating windows and reactor dimensions. In the chosen case examples, each single reactor operates in discharge mode for around 4–5 h (depending on plant configuration) as a back-up power generator, heating up a compressed air stream up to ∼ 1000 °C and achieving an energy density between 816 and 2214 kWhth/m3. Gas turbines in recuperative, steam injected and combined cycle power plant architectures integrated in the novel chemical looping combustion (CLC) reactor are investigated. Cycle efficiencies up to 49% are calculated for systems that make use of a single reactor configuration and exploit the residual heat for power production through a organic Rankine cycle (ORC) bottomed system. A more flexible multi-reactor configuration is also investigated to address the unavoidable decay in power output during discharge and provide power output controllability. The levelized cost of electricity (LCOE) is estimated be comparable to system elements from the literature when H2 is used as reducing gas. The use of biogas to reduce the solids during the energy charge stage is found to be particularly advantageous, leading to LCOE values between ∼ 120 and 175 €/MWh for the reference reactor system using iron-based solids. This also allows achieving negative CO2 emissions if the captured CO2 generated during the reduction stage is stored.

Наш клинический опыт применения гольмиевой лазерной энуклеации простаты

Surgical treatment of benign prostatic hyperplasia (BPH) is influenced by a rapidly growing number of technologies.To determine the surgical potential of holmium laser enucleation of the prostate (HoLEP) and the rate of postoperative complications during the learning curve.A total of 98 patients undergoing HoLEP in the surgical department of the Clinical Hospital "Mother & Child" during the period from January 2018 to May 2020 were included in the study. HoLEP was performed by a single surgeon with previous experience in transurethral procedures. The criteria for inclusion in the study group were as follows: moderate-to-severe lower urinary tract symptoms, prostate volume > 40 cm3, maximum flow <15 ml/sec, the volume of residual urine > 50 ml. The exclusion criteria were the following: inflammatory process in the lower urinary tract, genitourinary malignancy, previous urinary tract interventions. The evaluated criteria included age, prostate size, International Prostate Symptoms Score (IPSS and QoL), bladder diary, PSA, uroflowmetry, total operative time, length of catheterization, complications according to the Clavien-Dindo Classification, and length of stay.During pathologic study, two cases of incidental prostate cancer (2.1%) were detected. The relationships between the prostate size and operative time (p<0.05), operative time and length of stay (p<0.05) were found. The total rate of complications was 16.3%. There were no complications more or equal IIIb according to the Clavien-Dindo Classification. The most dangerous complications were injuries of the bladder wall and ureteral orifice (31.25% and 18.75% among all complications, respectively).It should be considered that a large "middle lobe" is associated with a high risk of injury of the ureteral orifices. In our series, there were 5 cases of bladder tamponade, while bladder injuries during the morcellation developed in the first 10 patients.HoLEP is a reasonable alternative to TURP for surgical treatment of BPH and is considered a safe procedure for patients taking anticoagulant and antiplatelet drugs. Past experience of TURP allows to learn the technique faster and to reduce the number of complications.

Diagnostic performance of the vesical imaging-reporting and data system for detecting muscle-invasive bladder cancer in real clinical settings: Comparison with diagnostic cystoscopy.

We herein compared the diagnostic performance of Vesical Imaging-Reporting and Data System (VI-RADS) scoring with diagnostic cystoscopy and evaluated diagnostic accuracies based on tumor locations. Among 112 bladder cancer patients who underwent multiparametric magnetic resonance imaging and diagnostic cystoscopy preoperatively to detect bladder cancer, 61 were analyzed. VI-RADS was categorized into 5 stages by 2 radiologists (R1 and R2). Cut-off values ≥3 indicated muscle-invasive bladder cancer (MIBC). Muscle invasion (MI) was visually evaluated using diagnostic cystoscopy by 2 urologists (U1 and U2). The sensitivity and specificity of VI-RADS scores and diagnostic cystoscopy for diagnosing MI were compared. 16 patients (26.2%) were pathologically diagnosed with MIBC. Regarding MI diagnostic accuracy, the sensitivity/specificity of VI-RADS scores were 93.8/88.9% by R1 and 87.5/86.7% by R2, while those of diagnostic cystoscopy were 56.3/68.9% by U1 and 68.8/84.4% by U2. Therefore, the diagnostic accuracy of VI-RADS was significantly higher than that of cystoscopy, particularly for tumors located on the bladder neck, trigone, dome, and posterior and anterior walls. Over- and under-diagnosis rates were higher with VI-RADS than with diagnostic cystoscopy (25.9% vs. 14.8%) for tumors located on the lateral wall or ureteral orifice. VI-RADS had superior diagnostic performance for detecting MI, especially in tumors located at the bladder neck/trigone/dome/posterior and anterior wall. However, VI-RADS was inferior to cystoscopy in terms of MI detection for tumors located on the lateral wall or ureteral orifice. Therefore, a combination of diagnostic tools is recommended for the accurate staging of these tumors.

Theoretical study for bubble diameter prediction at detachment from an orifice in high liquid velocity cross-flow

Bubble formation and detachment in liquid cross-flow widely existed in industrial systems. In this work, an integrated theoretical model based on a global force balance on the bubble detaching from a wall orifice in high liquid cross-flow is established to give a comprehensive description of bubble detaching process. The bubble detachment diameter are predicted by the model, and the effect of variation forces acing on bubble surface caused by liquid velocity, air flow rate and orifice diameter on bubble detachment is analyzed. Predictions of the theoretical model compare well with the previous experiment. In the horizontal direction, the liquid inertia force is the main detaching force, and the liquid drag force plays an important role in the early stage of bubble detachment. Because of the different liquid flow rate, the resultant force change has great influence on bubble detachment. However, due to the difference of gas flow rate and orifice diameter, the change of resultant force has little effect on bubble detachment. The relationship between gas–liquid momentum ratio, orifice diameter and bubble detachment diameter is fitted. When the ratio is less than 0.2, the liquid inertia force and drag force caused by liquid velocity has a great influence on bubble detachment diameter. When the ratio is greater than 0.2, the effect of liquid velocity is gradually weakened, and the bubble detachment becomes difficult due to the increase of air flow.

MP36-07 EVALUATING THE DIAGNOSTIC ACCURACY OF VESICAL IMAGING-REPORTING AND DATA SYSTEM FOR DETECTING MUSCLE-INVASIVE BLADDER CANCER IN REAL CLINICAL SETTING

You have accessJournal of UrologyImaging/Radiology: Uroradiology I (MP36)1 Apr 2020MP36-07 EVALUATING THE DIAGNOSTIC ACCURACY OF VESICAL IMAGING-REPORTING AND DATA SYSTEM FOR DETECTING MUSCLE-INVASIVE BLADDER CANCER IN REAL CLINICAL SETTING Ryohei Kufukihara*, Eiji Kikuchi, Keisuke Shigeta, Youta Yasumizu, Nobuyuki Tanaka, Toshikazu Takeda, Kazuhiro Matsumoto, Ryuichi Mizuno, Yuki Arita, Hirotaka Akita, Masahiro Jinzaki, and Mototsugu Oya Ryohei Kufukihara*Ryohei Kufukihara* More articles by this author , Eiji KikuchiEiji Kikuchi More articles by this author , Keisuke ShigetaKeisuke Shigeta More articles by this author , Youta YasumizuYouta Yasumizu More articles by this author , Nobuyuki TanakaNobuyuki Tanaka More articles by this author , Toshikazu TakedaToshikazu Takeda More articles by this author , Kazuhiro MatsumotoKazuhiro Matsumoto More articles by this author , Ryuichi MizunoRyuichi Mizuno More articles by this author , Yuki AritaYuki Arita More articles by this author , Hirotaka AkitaHirotaka Akita More articles by this author , Masahiro JinzakiMasahiro Jinzaki More articles by this author , and Mototsugu OyaMototsugu Oya More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000000880.07AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Although Vesical Imaging-Reporting and Data System (VI-RADS) has introduced for additional diagnostic modality for bladder cancer (Bca) patients, the diagnostic accuracy in real clinical setting remains uncertain. Our aim is to compare the diagnostic performance of VI-RADS scoring between urologists and radiologists, and to evaluate the accuracy for detecting muscle invasive bladder cancer (MIBC). METHODS: We identified 112 patients who underwent multiparametric- magnetic resonance imaging (mp-MRI) and diagnostic cystoscope preoperatively for Bca detection. VI-RADS was categorized from 1 to 5 (3 or more as suspecting muscle invasive) among two radiologists (R1 and R2) and two urologists (U1 and U2), who were blinded to histopathologic findings. The presence of muscle invasion was also visually evaluated by cystoscopic findings. The MacNemar analysis was used to assess the impact of diagnostic accuracy between VI-RADS and cystoscope. RESULTS: Overall, 61 patients met the criteria and were able to calculate VI-RADS score. Among them, 16 (26.2%) were pathologically diagnosed as MIBC and 45 (73.8%) as non-MIBC. Focusing on muscle invasion diagnostic accuracy, the sensitivity/specificity values in VI-RADS score were 93.8% and 88.9% by R1, 87.5% and 86.7% by R2, 81.3% and 84.4% by U1, and 81.3% and 80.0% by U2, which had no significant differences among radiologists and urologists (p=0.131, p=0.184, respectively). On the other hand, the sensitivity/specificity values in diagnostic cystoscopy were 53.3% and 68.2% by U1, 66.7% and 86.4% by U2, which diagnostic accuracy were marginally significantly lower than VI-RADS score compared to that of R1 (p=0.007 and p=0.062, respectively). Interestingly, VI-RADS scored by R1 and R2 showed overestimations upon 5 and 6 cases, and underestimations upon 1 and 3 cases out of 61 cases (12.3% misdiagnosis as total), which were all localized in lateral wall or nearby ureteral orifice. Limiting in these tumor locations, the diagnostic cystoscopy performed by U1 and U2 tended to have higher diagnostic accuracy than those of VI-RADS (overestimations were 3 and 2 cases, and underestimations were 2 and 0 cases, respectively (5.7% misdiagnosis as total). CONCLUSIONS: VI-RADS shows promise as a comprehensive tool which can be used by both urologists and radiologist. Although VI-RADS comprises the higher diagnostic accuracy for detecting muscle invasion, visual judgement acquired by cystoscope may be crucial upon tumors developed in lateral wall or nearby ureteral orifice. Source of Funding: nothing © 2020 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 203Issue Supplement 4April 2020Page: e524-e524 Advertisement Copyright & Permissions© 2020 by American Urological Association Education and Research, Inc.MetricsAuthor Information Ryohei Kufukihara* More articles by this author Eiji Kikuchi More articles by this author Keisuke Shigeta More articles by this author Youta Yasumizu More articles by this author Nobuyuki Tanaka More articles by this author Toshikazu Takeda More articles by this author Kazuhiro Matsumoto More articles by this author Ryuichi Mizuno More articles by this author Yuki Arita More articles by this author Hirotaka Akita More articles by this author Masahiro Jinzaki More articles by this author Mototsugu Oya More articles by this author Expand All Advertisement PDF downloadLoading ...

Computational Investigation of Flow Control Methods in the Impeller Rear Cavity

In typical median and small aeroengines, the air used to realize the functions such as cooling of turbine blades and disks, sealing of turbine cavities and bearing chambers, adjusting of rotating assembly axial load is normally drawn through the rear cavity of centrifugal impeller, so the thorough understanding of flow characteristics and pressure distribution and the proposal of the corresponding control methods in the cavity are the key to design the rational secondary air system. With an impeller rear cavity in a small turbofan engine as an object, the current study was dedicated to the investigation of flow control methods in the cavity. Two methods, namely, baffle and swirl-controlled orifice, were proposed to regulate the pressure loss and distribution in the cavity. Furthermore, the influence of geometry parameters of the two methods such as the length of baffle, the space between the baffle and rotating disk wall, the orientation, and radial position of swirl-controlled orifice was investigated. The CFD results show that the swirl-controlled orifice which could deswirl the flow is more effective in regulating the pressure loss and its distribution in cavity than baffle. The variation of the radial position of the swirl-controlled orifice had little influence on pressure loss but obvious influence on pressure distribution; therefore, decreasing the radial position could reduce the axial load on the rotating disk without changing the outlet pressure.

Bubble formation and evolution behavior from vertical wall orifice

Bubble formation is an integral part of the two-phase flow science. Through numerical simulation and experiments using different air flow rates and orifice diameters, the present study aims at investigating the behavior of bubble formation and evolution from vertical wall orifice in quiescent pure water. For the experiments, the images of the bubble formation process under different working conditions were recorded using a high-speed camera and analyzed the entire process. The bubble formation process can be divided into three stages, namely nucleation, stable growth, and necking. According to the obtained results, bubble forms only when the air-phase pressure exceeds the threshold pressure at wall orifice. Due to the influence of the threshold pressure and buoyancy, the bubble volume decreases with an increase in the wall orifice diameter for the same flow rate. Moreover, the volume of fluid method is applied to simulate bubble formation in a three-dimensional model and the “buffer volume” is considered in the simulation model. The simulation results matched well with the experimental data, which proves the existence of threshold pressure and the periodic pressure fluctuation at the wall orifice.

Analysis and prediction of nature gas noise in a metering station based on CFD

Based on the previous measurements data, the standard orifice flowmeters is one of the main noise sources in nature gas metering stations. In this paper, a theoretical method that combines the Large Eddy Simulations (LES) with the Ffowcs Williams Hawkings (FW-H) acoustic analogy theory has been used to analysis the Sound Pressure Level (SPL) distribution in standard orifice flowmeter. And then, a series of numerical simulations have been performed over a range of conditions, including medium velocity, aperture size, and orifice thickness. At last, a correlation formula of the maximum SPL and medium velocity has been presented by fitting the numerical results. It shows that the SPL increases over velocity logarithmically, and the maximum SPL is present at the upstream wall of orifice and in two reverse flows of vortex areas of the downstream pipe. Meanwhile, a smaller aperture size leads to higher SPL, while orifice thickness brings about faint influence. The SPL increases by about 8 dB by the decreasing of aperture per 20 mm. Finally, the data obtained from the fitting are verified by field data and is approved by the staff. The results provide effective guidance for practical operation of orifice flowmeter noise prevention and control.

Transverse Injection Experiments within an Axisymmetric Scramjet Combustor

Abstract Investigations on the performance of a rear wall angled cavity with upstream transverse fuel injection in a Mach 1.8 flow field is experimentally studied in a non-reacting flow facility. The high speed flow is directed to a circular cross sectional supersonic combustor and proceeded towards the cavities having two consecutive angles being inclined towards the downstream flow direction. Wall mounted injector is positioned at a distance of 10 mm upstream from the cavity. Air is used as the injectant to simulate the gaseous fuel. The experiments are performed to explore the effect of the increase in injection pressures within various rear wall angled cavities by comparing with the ‘no-injection’ case and to finally assess the mixing performance of the flow. Transverse injection through upstream wall orifice of the cavities outlines a more uniform mixing compared to ‘no-injection’ configuration. Increase in injection pressures enhances mixing and stagnation pressure loss values.

Numerical investigation and optimization on the micro-ramp vortex generator within scramjet combustors with the transverse hydrogen jet

An effective fuel supply strategy with high mixing efficiency, large penetration depth and low stagnation pressure losses determines the overall performance of the scramjet (supersonic combustion ramjet) engine. In this paper, the transverse hydrogen injection flow field with a micro-ramp located upstream of the wall orifice has been investigated numerically based on the code validation. There are four design variables considered in the current study, namely the width, length, and height of the micro-ramp and the distance between the center of the wall orifice and the trailing point of the micro-ramp. Nine cases predicted by the three-dimensional Reynolds-averaged Navier–Stokes (RANS) equations coupled with the two equation k–ω shear stress transport (SST) turbulence model are used for parametric analysis, and the parametric analysis has been carried out by the extreme difference analysis approach. Three optimization cases are obtained, and they have different objectives, namely the minimization of the mixing length, the maximization of the penetration depth and the minimization of the stagnation pressure losses. The flow structures of all cases have been discussed and compared. The quantitative evaluation results of three optimization cases show that the extreme difference analysis approach is an efficient parametric analysis method, and it can obtain the optimal strategy for the micro-ramp within scramjet combustors with the transverse hydrogen jet.

Cavernous Sinus and Parasellar Region: An Endoscopic Endonasal Anatomic Cadaver Dissection.

The aim of this study was to investigate the neurovascular structures of the cavernous sinus with the endonasal endoscopic transpterygoid approach on fresh human cadavers. Additionally, the course of internal carotid artery (ICA) and relevant anatomy was thoroughly investigated to refine the anatomical landmarks, exposure difficulties, potential complications, and limitations using the endonasal endoscopic technique. This study was carried out at an otolaryngology department of a tertiary medical center between June 2014 and June 2015. The surgical dissection was performed on 10 fresh human cadaver specimens using paranasal sinus and skull base endoscopic instruments. Cavernous sinuses and parasellar area were explored via an endoscopic endonasal transpterygoid approach. Dehiscence was present in 5 (25%) cavernous ICAs. Projection of the cavernous ICA on the whole lateral sphenoid wall was prominent in 6 (%30) sphenoid sinuses. Anterior curve was prominent in 12 (60%) cavernous ICAs, whereas posterior was prominent in 7 (35%). Mean distance between the lateral wall of eustachian tube orifice and petrous ICA was 19.50 ± 1.05 mm (range 18-22 mm). Cranial nerves of the cavernous sinus showed no variation. Control of the ICA is critical during the endonasal endoscopic approach to the cavernous sinus and skull base. The vidian nerve is a reliable and important landmark to the petrous ICA in the transpterygoid approach. Dissection of the eustachian tube and its relation to the ICA has to be kept in mind during nasopharyngeal surgery.

Pressure and Velocity Fluctuation in the Numerical Simulation of Bubble Detachment in a Venturi-Type Bubble Generator

The Venturi-type bubble generator proposed by Oak Ridge National Laboratory is used to produce micro-sized bubbles. In this paper, a numerical simulation is carried out to study the process of the bubble formation and detachment from a wall orifice of a Venturi-type bubble generator in a cross-flowing liquid. The Volume-of-Fluid (VOF) method is applied to track the two-phase interface and study the evolution of the bubble formation. The result of the computation provides a visual three-dimensional bubble and shows the process of bubble formation and detachment. Three stages are identified during bubble formation (the expansion stage, the rising stage, and the collapse stage). Because of the compressibility of the gas, a fluctuation of the pressure and the mass flow rate in the gas chamber is observed, which is considered a significant effect on the bubble formation and detachment. The mechanism of the bubble detachment is clarified with the help of the mass flow rate fluctuation. The equivalent diameter is compared with that predicted by a previous model. A Coupled Level Set Volume-of-Fluid (CLSVOF) simulation is compared with the VOF simulation; the three stages and the fluctuation are also observed in the CLSVOF simulation.

Analysis of ligamentary atomization of highly perturbed liquid sheets

Ligamentary structures are often encountered in liquid atomization processes. They appear for instance during the atomization of liquid sheets issuing from triple-disk nozzles. Because of the development of turbulence along the internal wall of the discharge orifice, these sheets are highly perturbed and exhibit the formation of ligaments along their sides. The present investigation addresses the question of the origin of size dispersion of the droplets emanating from the atomization of these ligaments. The adopted strategy consists in describing the atomization process reported by experimental images by using a multi-scale tool and in conducting an analysis that concentrates on the dynamic of the small structures carried by the ligaments that might be the main small droplets providers. The advantages of the tool are its ease of application as well as its capacity to bring an information that incorporate the shape of the analyzed interface. The statistical scale analysis demonstrates that the small structures carried by the ligaments are subject to an elongation mechanism whose strength varies from one liquid to another. This mechanism is not dominant in the production of the small drops from the breakup of the ligaments. The dispersion of the drop size distribution, represented by the order of a Gamma distribution, is found to strongly correlate with the initial deformation of the ligaments. An interesting result here is the ease of characterizing the average ligament deformation with the concept of scale distribution. The fact that a single parameter is sufficient to represent the drop size dispersion and that this dispersion correlates with the ligaments deformation suggests the dominance of a single mechanism in the ligament breakup, i.e., the capillary mechanism. As demonstrated in a previous investigation, capillary mechanism is associated with elongation mechanism at small scales. All these results are strengthened by the fact that the explored experimental conditions are uncorrelated.

Thermal damage of sulfur processed chamber under Claus operating reaction conditions—A case study

The sulfur from acid gas and sour gas is recovered to produce useful sulfur products. The claus reaction is industrially important process to recover sulfur from corrosive acid and sour gases. To achieve claus reaction, high temperature reactor is utilized under controlled conditions. The Claus combustion reaction heater made of 94% alumina refractory bricks were damaged under ideal equilibrium operating conditions. The first principle mathematical model was developed to measure the temperature profiles at hot face bricks and its interfaces to predict outer steel surface temperature. The maximum outer steel wall surface temperature was measured as 548.6 °C using thermograph experiments and compared against the predicted temperature. Large variations in temperature differences have confirmed that the refractory wall was damaged due to abnormal reactions. This thermal damage is discussed and presented with various evidences from visual inspection. The hot face wall bricks, matrix blocks and orifice throat were damaged and presented by macroscopic visual inspection. However, hardness of the steel shell is within specified limit. Therefore, the refractory repair inside the reactor and thermal insulation of external shell has been proposed to prevent steel shell from creep, graphitization, and high temperature oxidization and corrosion damages.

Neoglottis reconstruction with sternohyoid muscles on upper-tracheal orifice after laryngectomy.

Ideal speech restoration remains a difficult challenge for patients undergoing laryngectomy so far. Our aim was to explore the feasibility of neoglottic reconstruction with sternohyoid muscles on upper-tracheal orifice after total laryngectomy which can obtain relatively ideal voice rehabilitation. Fifteen male patients are laryngectomized, of whom eight with standard total laryngectomy and seven underwent nonstandard total laryngectomy with epiglottis conserved. After laryngectomy, the upper margin of the anterior hypopharyngeal mucosa (postcricoid mucosa) was stitched to the posterior margin of upper-tracheal orifice and a triangle-shaped neoglottis on upper-tracheal orifice was reconstructed using bilateral sternohyoid muscles near the hyoid bone which were sutured to the posterior wall and bilateral of upper-tracheal orifice. Then tracheolingual root anastomosis was done and reconstruction surgery was completed. Finally, a satisfactory voice was achieved in 14 of 15 patients except one whose neoglottis is stenosed and 11 cases had no severe complications including aspiration erroneous deglutition. The stomach catheters were removed successfully from 4 to 6weeks after surgery in 11 cases, respectively. The neoglottis had to be closed in three patients because of aspiration problem. One neoglottis was closed 3weeks after surgical reconstruction because of tracheal rings tear which created a bigger neoglottis. One neoglottis was removed 32 moths after total laryngectomy due to big neoglottis. Another one was closed 3weeks after surgery by reason of the fear of aspiration without psychological preparation. Therefore, it is feasible to use the sternohyoid muscles for creation of a neoglottis on upper-tracheal orifice and provide an alternative surgical method of the voice restoration for the patients after laryngectomy.

Mixing augmentation mechanism induced by the pseudo shock wave in transverse gaseous injection flow fields

The mixing process between the injectant and air is very crucial for the engineering implementation of the scramjet engine, and this is due to the very short resident time of fuel in supersonic flows. In the current study, the three-dimensional Reynolds-average Navier–Stokes (RANS) equations coupled with the two equation k-ω shear stress transport (SST) turbulence model have been employed to investigate the transverse injection flow field with the pseudo shock wave induced by the high back pressure, and the freestream Mach number is 3.75. At the same time, the influence of the back pressure on the flow field properties has been evaluated as well. The obtained results show that the pseudo shock wave induced by the back pressure plays an important role in the mixing enhancement between the injectant and air. When the back pressure ratio is larger than 5.0, the mixing efficiency increases with the increase of the back pressure ratio. However, when the back pressure ratio is 3.0, the near-field mixing process has been improved, and accordingly its mixing efficiency in this region is larger than the benchmark. This implies that the intense combustion downstream of the injector can enhance the mixing process between the injectant and air, and the mixing and combustion process can be enhanced mutually. When the pseudo shock wave has been pushed upstream of the wall orifice, more injectant has been brought into the separation zone upstream of the injector, and this is beneficial for the mixing process between the injectant and air.

Plasma-enhanced mixing and flameholding in supersonic flow.

The results of experimental study of plasma-based mixing, ignition and flameholding in a supersonic model combustor are presented in the paper. The model combustor has a length of 600 mm and cross section of 72 mm width and 60 mm height. The fuel is directly injected into supersonic airflow (Mach number M=2, static pressure P(st)=160-250 Torr) through wall orifices. Two series of tests are focused on flameholding and mixing correspondingly. In the first series, the near-surface quasi-DC electrical discharge is generated by flush-mounted electrodes at electrical power deposition of W(pl)=3-24 kW. The scope includes parametric study of ignition and flame front dynamics, and comparison of three schemes of plasma generation: the first and the second layouts examine the location of plasma generators upstream and downstream from the fuel injectors. The third pattern follows a novel approach of combined mixing/ignition technique, where the electrical discharge distributes along the fuel jet. The last pattern demonstrates a significant advantage in terms of flameholding limit. In the second series of tests, a long discharge of submicrosecond duration is generated across the flow and along the fuel jet. A gasdynamic instability of thermal cavity developed after a deposition of high-power density in a thin plasma filament promotes the air-fuel mixing. The technique studied in this work has weighty potential for high-speed combustion applications, including cold start/restart of scramjet engines and support of transition regime in dual-mode scramjet and at off-design operation.

Hydraulic Performance of Aggregate Beds with Perforated Pipe Underdrains Flowing Full

Results are presented from an experimental study of the stage discharge relationship for a porous pipe buried under loose laid aggregate. A series of steady-state experiments were performed in which the depth of flow over the pipe was measured for a given pipe discharge. The stage-discharge relationship for the entire system is well described by an orifice equation when the water surface in the aggregate trench was horizontal and the pipe was running full at the outlet. An energy equation analysis shows that the dominant energy losses are due to flow through the small side wall orifices into the pipe and from friction losses along the pipe. Friction losses in the aggregate are shown to be negligible, which again supports the orifice equation model. Discharge coefficients are reported for three commonly available porous pipes. The results of this research can be used in the sizing and placement of subsurface drains in aggregate filled storm water infiltration practices such as infiltration trenches and porous pavements.

Effect of cavitating flow on forced convective heat transfer: a modeling study

With water as working medium, a numerical study on liquid convection heat transfer accompanied by cavitating flow in a circular tube was conducted by combining mixture model and Schnerr–Sauer cavitation mode in the commercial code, Ansys Fluent. Cavitation is instigated by setting a restriction orifice in the circular tube. The simulation results show that cavitation occurs around the wall of the restriction orifice and disappears at the downstream regions. The comparison of local heat transfer coefficients under the same mass flow rate indicates that, heat transfer is significantly augmented at the downstream regions of the restriction orifice because of the occurrence of cavitation. The analysis on the characteristics of cavitating and noncavitating flows confirms that the occurrence of cavitation can increase the turbulence intensity under the same mass flow rate, which is the origin for heat transfer to be enhanced. Based on it, the effects of such factors as inlet pressure and ratio of orifice to pipe diameter on cavitation enhanced heat transfer were further investigated for the purpose of application.