bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enhancing the Aggressive Intensity of a Cavitating Jet by Introducing Water Flow Holes and a Long Guide Pipe
Authors: Kamisaka Hirokazu , Soyama Hitoshi 
Published: October 2020

Abstract
It is known that the geometry of the nozzle has a great effect on the aggressive intensity of a cavitating jet. In previous reports, various nozzle geometries were proposed, and improvements made to the aggressive intensity were reported. However, no detailed description of the reasons why the aggressive intensity is improved by these various geometries was given. In this study, we conducted erosion tests on pure aluminum Japanese Industrial Standards JIS A1050P using 11 different nozzles with different geometries downstream from the throat outlet in order to understand the effects of the nozzle geometry on the aggressive intensity. In addition, in order to investigate the characteristics of the cavitating jet produced by each nozzle, measurements of the erosion areas, images of the cavitating jet using a high-speed video camera, and measurements of the impingement pressure of the cavitating jet were taken, and correlations between the parameters were obtained. It was found that the nozzle with the largest mass loss was a nozzle with water flow holes near to the throat outlet and a long guide pipe (LGP). The mass loss was 2.5 times that of the previously reported optimum geometry nozzle. Very high correlations were obtained between the mass loss, the inner diameter of the annular erosion area, the impingement pressure measured at the same standoff distance and the cavitation cloud lifetime. Based on these results and the images of the cavitating jets taken with the high-speed video camera, a new cavitating jet progression process is proposed.
Particle Image Velocimetry Measurements of Turbulent Jets Issuing From Twin Elliptic Nozzles With Various Orientations
Authors: Morris Ella Marie , Biswas Neelakash , Aleyasin Seyed Sobhan , Tachie Mark Francis 
Published: October 2020

Abstract
The effects of nozzle orientation on the mixing and turbulent characteristics of elliptical free twin jets were studied experimentally. The experiments were conducted using modified contoured nozzles with a sharp linear contraction. The centers of the nozzle pair had a separation ratio of 5.5. Two nozzle configurations were tested, twin nozzles oriented along the minor plane (Twin_Minor) and twin nozzles oriented along the major plane (Twin_Major) and the results were compared with a single jet. In each case, the Reynolds number based on the maximum jet velocity and the equivalent diameter was 10,000. A planar particle image velocimetry (PIV) system was used to measure the velocity field in the jet symmetry plane. It was observed that the velocity decay rate is not sensitive to nozzle orientation. However, close to the jet exit, the spread rate was highest in the minor plane. In addition, contour plots of swirling strength, Reynolds shear stress and turbulent intensities revealed significant differences between the minor and major planes. Velocity profiles showed little variation close to the jet exit, while further downstream the variations between the velocity profiles were more pronounced between the major and minor planes.
Streamwise Aspect Ratio Effects on Turbulent Flow Separations Induced by Forward–Backward-Facing Steps
Authors: Chalmers Heath , Fang Xingjun , Tachie Mark F. 
Published: October 2020

Abstract
Separated and reattached turbulent flows induced by two-dimensional forward–backward-facing steps (FBFS) with different streamwise lengths submerged in a thick turbulent boundary layer (TBL) are investigated using time-resolved particle image velocimetry (TR-PIV). The aspect ratios (AR) of the step range from 1 to 8, and the Reynolds number based on the freestream velocity and step height is 13 200. The thickness of the incoming turbulent boundary layer is 6.5 times the step height. The effects of varying aspect ratio of the steps on the mean flow, principal stretching, Reynolds stresses, triple velocity correlation, two-point autocorrelation, and unsteadiness of turbulent separation bubbles are studied. The results indicate that the mean flow reattaches over the step for FBFS with aspect ratios of 2 and higher. Two local peaks of Reynolds stresses occur irrespective of AR, and for a sufficiently large AR, a third local peak of Reynolds stresses appear in the shear layer emanating from the trailing edge of the bluff bodies. The streamwise decay of Reynolds stresses is slower for smaller AR cases. Incoming coherent structure is strongly disturbed near an inclined edge where principal stretching switches orientation abruptly. The temporal variation of the first proper orthogonal decomposition (POD) mode and reverse flow area over the bluff bodies shows remarkable correlation, which signifies the flapping motion of separation bubble.
Fundamental Study on Injector Flow Characteristics of Self-Pressurizing Fluid for Small Rocket Engines
Authors: Yasuda Kazuki , Nakata Daisuke , Uchiumi Masaharu , Okada Kugo , Imai Ryoji 
Published: October 2020

Abstract
Nitrous oxide is a suitable propellant for rocket engines and has been widely used in various countries, given its high saturated vapor pressure, which enables self-pressurization. Because nitrous oxide is in a state of vapor–liquid equilibrium in tanks, it is easy to form a gas–liquid two-phase flow by cavitation in feed line. Since accurately estimating the performance of rocket engines requires evaluating the characteristics of propellant flows, tests reported in this paper were conducted using hybrid rocket engines under three conditions: cold flow test, hot firing test at low back pressure, and hot firing test at high back pressure. With consideration to the subcooling degrees, nitrous oxide may be in an unsteady superheated state in the upstream flow of the injector. In a comparison of the pressure ratios between the injector in each test condition, it is observed that a critical two-phase flow was formed in the injector in the cold flow test and in the low backpressure firing test. In the high backpressure hot firing test, the injector flow may be choked, but the large oscillations were observed in chamber pressure and thrust. According to the FFT analysis results, these oscillations were caused by chugging and acoustic oscillation. In light of these experimental results, it is suggested that when the chamber pressure fluctuates due to combustion instability such as chugging and acoustic oscillation, it may affect the injector flow characteristics and the critical two-phase flow.
Theoretical, Numerical, and Experimental Study on an Unsteady Venturi Flowmeter for Incompressible Flows
Authors: Kambayashi Izuru , Kang Donghyuk , Nishimura Naoki 
Published: October 2020

Abstract
To examine the dynamic characteristics of turbomachinery and cavitation, the pulsating flow rates should be evaluated. As it is difficult to measure these pulsating flow rates quantitatively, systematic research has not been conducted on the dynamic characteristics of turbomachinery and cavitation. In this paper, an unsteady energy equation for a venturi tube has been proposed to measure pulsating flow rates. The pulsating flow rates were calculated using two methods based on the unsteady energy equation for incompressible flows. The first method calculated a pulsating flow rate by using the Euler method. The second one calculated the complex amplitude of a pulsating flow rate using a transfer function derived from the linearized unsteady energy equation. We analytically examined the order of magnitude for unsteady terms. The results indicated that the unknown unsteady loss was much smaller than the unsteady momentum. In the experiment, pulsating flows were generated by a reciprocating piston, and the given pulsating flow was measured using a hot wire anemometer. The pulsating flow rates evaluated by using the proposed methods were validated via numerical simulation and experiment. In particular, the influence of amplitudes on the evaluation of pulsating flow rates was numerically examined. Therefore, the nonlinear effect could be evaluated by using the proposed method, and the time-averaged loss coefficient was enough to evaluate the pulsating flow rate coefficient. The proposed unsteady venturi flowmeter can be applied to a wide range of research fields, such as analyzing dynamic characteristics of flows.
Analysis of the Pressure Pulsation and Vibration in a Low-Specific-Speed Centrifugal Pump
Authors: Cui Baoling , Zhang Yingbin , Huang Yakun 
Published: October 2020

Abstract
Unsteady pressure pulsation and fluid force induced by flow instabilities in the centrifugal pump is an important cause of vibration, which is detrimental to the safe operation of the pump. In this study, we numerically investigated the pressure pulsation and radial force in a low-specific-speed centrifugal pump by using the detached-eddy simulation method. We also performed a vibration displacement experiment on the shaft of the centrifugal pump. The vortex identification method was introduced to clarify the internal correlation between unsteady flow structures with pressure pulsations. The results showed that the pressure pulsations at the impeller outlet were closely associated with the periodic vortex shedding from the blade pressure surface. The rotor–stator interaction between a relatively big trailing vortex core and volute tongue generated larger pressure pulsation and radial force in the pump at a low flow rate. Under a large flow rate, the trailing vortex core was easily broken and dispersed, and this resulted in smaller pressure pulsation and radial force compared with that at a low flow rate. Under the design flow rate, the pressure pulsation intensity and the radial force in the impeller were smaller than that under the off-design flow rate. Compared with the spectra between the radial force on the impeller and radial displacement on the shaft, they both presented higher amplitude at the shaft frequency. The vibration of the pump shaft was closely related to the radial force on the impeller.
Training Distribution in 1500-m Speed Skating: A Case Study of an Olympic Gold Medalist
Authors: Orie Jac , Hofman Nico , Meerhoff Laurentius A. , Knobbe Arno 
Published: October 2020

At the Olympic level, optimally distributing training intensity is crucial for maximizing performance. Purpose: The authors evaluated the effect of training-intensity distribution on anaerobic power as a substitute for 1500-m speed-skating performance in the 4 y leading up to an Olympic gold medal. Methods: During the preparation phase of the speed-skating season, anaerobic power was recorded periodically (n = 15) using the mean power (in watts) with a 30-s Wingate test. For each training session in the 4 wk prior to each Wingate test, the volume (in hours), training type (specific, simulation, nonspecific, and strength training), and the rating of perceived exertion (RPE; CR-10) were recorded. Results: Compared with the 8 lowest, the 7 highest-scoring tests were preceded by a significantly (P < .01) higher volume of strength training. Furthermore, the RPE distribution of the number of nonspecific training sessions was significantly different (P < .01). Significant (P < .05) correlations highlighted that a larger nonspecific training volume in the lower intensities RPE 2 (r = .735) and 3 (r = .592) was associated positively and the medium intensities RPE 4 (r = −.750) and 5 (r = −.579) negatively with Wingate performance. Conclusion: For the subject, the best results were attained with a high volume of strength training and the bulk of nonspecific training at RPE 2 and 3, and specifically not at the adjoining RPE 4 and 5. These findings are surprising given the aerobic nature of training at RPE 2 and 3 and the importance of anaerobic capacity in this middle-distance event.
Career Performance Trajectories of Professional Australian Football Players
Authors: Sullivan Courtney , Kempton Thomas , Ward Patrick , Coutts Aaron J. 
Published: October 2020

Purpose: To develop position-specific career performance trajectories and determine the age of peak performance of professional Australian Football players. Methods: Match performance data (Australian Football League [AFL] Player Rank) were collected for Australian Football players drafted via the AFL National Draft between 1999 and 2015 (N = 207). Players were subdivided into playing positions: forwards (n = 60; age 23 [3] y), defenders (n = 71; age 24 [4] y), midfielders (n = 58; age 24 [4] y), and ruckmen (n = 18; age 24 [3] y). Linear mixed models were fitted to the data to estimate individual career trajectories. Results: Forwards, midfielders, and defenders experienced peak match performance earlier than ruckmen (24–25 vs 27 y). Midfielders demonstrated the greatest between-subjects variability (intercept 0.580, age 0.0286) in comparison with ruckmen, who demonstrated the least variability (intercept 0.112, age 0.005) in AFL Player Rank throughout their careers. Age had the greatest influence on the career trajectory of midfielders (β [SE] = 0.226 [0.025], T = 9.10, P < .01) and the least effect on ruckmen (β [SE] = 0.114 [0.049], T = 2.30, P = .02). Conclusions: Professional Australian Football players peak in match performance between 24 and 27 years of age with age, having the greatest influence on the match performance of midfielders and the least on ruckmen.
Monitoring Cardiorespiratory Fitness in Professional Soccer Players: Is It Worth the Prick?
Authors: Buchheit Martin , Simpson Ben M. , Lacome Mathieu 
Published: October 2020

Purpose: To compare between-tests changes in submaximal exercise heart rate (HRex, 3 min, 12 km/h) and the speed associated with 4 mmol/L of blood lactate (V4mmol) in soccer players to get insight into their level of agreement and respective sensitivity to changes in players’ fitness. Methods: A total of 19 elite professional players (23 [3] y) performed 2 to 3 graded incremental treadmill tests (3-min stages interspersed with 1 min of passive recovery, starting speed 8 km/h, increment 2 km/h until exhaustion or 18 km/h if exhaustion was not reached before) over 1.5 seasons. The correlation between the changes in HRex and V4mmol was examined. Individual changes in the 2 variables were compared (>2 × typical error considered “clear”). Results: The changes in HRex and V4mmol were largely correlated (r = .82; 90% confidence interval, .65–.91). In more than 90% of the cases, when a clear individual change in HRex was observed, it was associated with a similar clear change in V4mmol (the same direction, improvement, or impairment of fitness) and conversely. Conclusions: When it comes to testing players submaximally, the present results suggest that practitioners can use HRex or V4mmol interchangeably with confidence. However, in comparison with a field-based standardized warm-up run (3–4 min, all players together), the value of a multistage incremental test with repeated blood lactate samplings is questionable for a monitoring purpose given its time, labor, cost, and poorer player buy-in.
Managing Load to Optimize Well-Being and Recovery During Short-Term Match Congestion in Elite Basketball
Authors: Doeven Steven H. , Brink Michel S. , Huijgen Barbara C.H. , de Jong Johan , Lemmink Koen A.P.M. 
Published: October 2020

In elite basketball, players are exposed to intensified competition periods when participating in both national and international competitions. How coaches manage training between matches and in reference to match scheduling for a full season is not yet known. Purpose: First, to compare load during short-term match congestion (ie, ≥2-match weeks) with regular competition (ie, 1-match weeks) in elite male professional basketball players. Second, to determine changes in well-being, recovery, neuromuscular performance, and injuries and illnesses between short-term match congestion and regular competition. Methods: Sixteen basketball players (age 24.8 [2.0] y, height 195.8 [7.5] cm, weight 94.8 [14.0] kg, body fat 11.9% [5.0%], VO2max 51.9 [5.3] mL·kg−1·min−1) were monitored during a full season. Session rating of perceived exertion (s-RPE) was obtained, and load was calculated (s-RPE × duration) for each training session or match. Perceived well-being (fatigue, sleep quality, general muscle soreness, stress levels, and mood) and total quality of recovery were assessed each training day. Countermovement jump height was measured, and a list of injuries and illnesses was collected weekly using the adapted Oslo Sports Trauma Research Center Questionnaire on Health Problems. Results: Total load (training sessions and matches; P < .001) and training load (P < .001) were significantly lower for ≥2-match weeks. Significantly higher well-being (P = .01) and less fatigue (P = .001) were found during ≥2-match weeks compared with 1-match weeks. Conclusion: Total load and training load were lower during short-term match congestion compared with regular competition. Furthermore, better well-being and less fatigue were demonstrated within short-term match congestion. This might indicate that coaches tend to overcompensate training load in intensified competition.
Association between atopic keratoconjunctivitis and the risk of corneal ulcer
Authors: Jan Ren-Long , Weng Shih-Feng , Wang Jhi-Joung , Tseng Sung-Huei , Chang Yuh-Shin 
Published: October 2020

AimsTo investigate the risk of corneal ulcer in patients with atopic keratoconjunctivitis (AKC).MethodsThe nationwide, population-based, retrospective, matched cohort study included 171 019 newly diagnosed patients with AKC who were identified by the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM), code 372.05, and selected from the Taiwan National Health Insurance Research Database. The age-, sex- and potential comorbidities-matched control group included 171 019 patients with non-AKC selected from the Taiwan Longitudinal Health Insurance Database 2000. Patient information was collected between 1 January 2004 and 31 December 2011, and both groups of patients were tracked from the index date until December 2013. The incidence and risk of corneal ulcer (ICD-9-CM code 370.0 except for 370.07) was compared between the groups. A Cox proportional hazard regression analysis was performed to obtain the adjusted HR for corneal ulcer. The cumulative corneal ulcer incidence rate was calculated with the Kaplan-Meier analysis.ResultsIn total, 2018 patients with AKC and 1481 controls developed a corneal ulcer during the follow-up period. The incidence rate of corneal ulcer was 1.42 times (95% CI1.33 to 1.52; p<0.0001) higher in patients with AKC than in controls. After adjusting for potential confounders, including diabetes mellitus, chronic renal disease, topical steroid ophthalmic agent use, lid margin disease, keratoconjunctivitis sicca, ocular blunt trauma and post-corneal transplantation, patients with AKC were 1.26 times more likely to develop a corneal ulcer than controls (adjusted HR, 1.26; 95% CI 1.14 to 1.39; p<0.05).ConclusionsPatients with AKC had an increased risk of developing a corneal ulcer and should be advised of this risk.
Prevalence, risk factors and management of ocular hypertension or glaucoma in patients with Vogt-Koyanagi-Harada disease
Authors: Yang Peizeng , Wang Chaokui , Su Guannan , Pan Su , Qin Yang , Zhang Jun , Cao Qingfeng , Zhong Zhenyu , Zhou Chunjiang , Wang Yao , Kijlstra Aize 
Published: October 2020

Background/aimsThis study was performed to examine the prevalence, risk factors and treatment outcome of OHT/glaucoma in Chinese patients with Vogt-Koyanagi-Harada (VKH).MethodsRetrospective non-interventional case series were conducted on a total of 2281 patients with VKH referred from April 2008 to April 2019. Of these cases, 1457 had a minimum follow-up period of 3 months and were included for this study. Medical records were reviewed for demographic, ocular and treatment data.ResultsAmong 2914 eyes of 1457 patients with VKH, 695 (23.9%) eyes of 425 patients (29.2%) developed OHT/glaucoma. The risk factors of OHT/glaucoma included initial BCVA of 20/200 or worse (OR=4.826), final best-corrected visual acuity (BCVA) of 20/50–20/100 (OR=5.341) and final BCVA of 20/200 or worse (OR=4.235), the interval between uveitis attack and referral time interval being 2 months or more (OR=3.318), more than three recurrent episodes (OR=4.177) and posterior synechiae (OR=1.785). The main possible mechanisms of OHT/glaucoma were inflammatory factor-induced open-angle OHT/glaucoma in 277 eyes (39.9%) and pupillary block arising from complete posterior synechiae in 201 eyes (28.9%). In these 695 eyes with OHT/glaucoma, normalised intraocular pressure (IOP) was achieved in 389 eyes (56.0%) following medical treatment. In the remaining 306 eyes, various surgical interventions were performed and a normalised IOP could be achieved in 249 eyes (81.4%).ConclusionOHT/glaucoma is a common complication in Chinese patients with VKH. Risk factors of OHT/glaucoma included worse acuity at first and final visits, the longer interval between uveitis attack and referral, more recurrent episodes and posterior synechiae.
Compression sutures combined with intracameral air injection versus thermokeratoplasty for acute corneal hydrops: a prospective-randomised trial
Authors: Zhao Zelin , Wu Siteng , Ren Weina , Zheng Qinxiang , Ye Cong , Kim Andy D. , Jhanji Vishal , Wang Michael T. M. , Chen Wei 
Published: October 2020

AimsTo compare the efficacy of compression sutures combined with intracameral air injection (CSAI) and thermokeratoplasty (TKP) for the management of acute corneal hydrops in keratoconus.MethodsIn this multi-centre randomised clinical trial, 20 patients with keratoconus (20 eyes) with acute corneal hydrops were enrolled and randomised to receive either CSAI or TKP and followed-up for a period of 6 months.ResultsThere were no significant differences in patient demographics, severity of corneal hydrops and preoperative duration of symptoms between the two groups. In both groups, corneal oedema resolved within 2 weeks. The maximum thickness of the corneal scars following CSAI and TKP was not significantly different. Best spectacle-corrected visual acuity was superior in the CSAI group at 6-month follow-up (CSAI vs TKP, 0.52 (0.37, 0.85) vs 0.96 (0.70, 1.34) LogMAR, p=0.042). CSAI resulted in greater corneal endothelial cell density (CSAI vs TKP, 2677.8±326.7 vs 1955.3±298.1 cells/mm2, p<0.001) and flatter corneal curvature (CSAI vs TKP: mean keratometry value, 52.13±4.92 vs 63.51±5.83D, p<0.001; maximum keratometry value, 65.21±7.42 vs 77.13±12.01D, p=0.016) at the 6-month follow-up.ConclusionAlthough both CSAI and TKP resulted in resolution of acute corneal hydrops in keratoconus, CSAI was associated with superior clinical outcomes in this study.Chinese Clinical trial registration numberChiCTR-IOR-17013764