bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Resonant Environment on Discrete Frequency Noise Generation from a Two-Dimensional Airfoil
Authors: Yamada K. , Furukawa M. , Sakurada S. , Mizokami T. , Aso S. , Sakoda K. , Fukui T. 
Published: May 2021

Abstract
It is known that discrete frequency noise with specific peak frequency, which is often called tonal noise, is generated from an airfoil in the flow conditions within certain Reynolds number range. In this study, the tone noise generated from the NACA0012 airfoil inclined at a small angle to the stream is investigated. The test has been conducted in two different configurations to clarify the effect of resonant environment on the noise generation: one is a duct configuration in which wall was installed at both sides across the airfoil, and the other is a wall-free configuration without any wall around the airfoil. The numerical simulation with lattice Boltzmann method (LBM) also has been conducted to investigate detailed generation mechanism of the tone noise. The experimental results show that the tone noise is generated with several peak frequencies in the wall-free configuration, while it has a single peak for the duct configuration. The simulation results are compared with the experiments at two configurations in terms of sound pressure spectrum, and the pressure fluctuation leading to the tone noise and the corresponding unsteady flow phenomenon are discussed to clarify the noise generation mechanism. A feedback loop is formed between the vortex shedding from separated blade surface boundary layer and the resulting aerodynamic sound at the trailing edge, which results in the tone noise.
Effect of Leading Edge Profile on Cavitation Performance of Mixed Flow Impeller
Authors: Sano Takeshi , Iino Masamichi , Maeda Satoshi 
Published: May 2021

Abstract
Cavitation inception on a pump impeller blade is affected by the blade profile around the leading edge. Even if the difference of the blade profile is limited around the local leading edge area, such as, different elliptical ratios of the leading edge, pressure limitation of cavitation inception differs drastically. This leads to the difference of cavitation erosion speed, and it is important to understand the mechanism and quantitative effect of leading edge shape on cavitation inception, to avoid troubles related to cavitation erosion. In this study, CFD and experimental investigation were carried out to clarify the effect of leading edge shape on cavitation inception. The tested pump was a mixed flow pump, which is widely used as a circulating water pump for power plants. Various leading edge shape were calculated and tested with keeping the blade camber line. Only elliptical ratio of the leading edge on the suction side was changed. As for CFD, isolated impeller, single phase analysis was carried out for 90, 100 and 110% design flow rates, blade surface area on which pressure is less than the vapour pressure was evaluated for each cases. In the experiment, 5 bladed mixed flow pump model was used, and the cavitation length was measured. Both experimental and calculated results were compared and considered. As a result, it was clarified that the optimized value of elliptical ratio is around 2 to 6, which changes depending on the flow rate. Additionally, when the elliptical ratio is 4, was almost half of the one with elliptical ratio 1. Cavity length and cavitation intensity has positive correlation, and estimated erosion speed when the elliptical ratio is4 is almost an eighth of baseline.
The effect of unsteady vortex behavior on noise characteristics in a centrifugal compressor
Authors: Tajima Kenta , Miida Hiroshi , Fujisawa Nobumichi , Ohta Yutaka 
Published: May 2021

Abstract
The effect of diffuser width on the noise level of a centrifugal compressor equipped with vaneless diffusers was investigated through experiments and numerical techniques. In this regard, two diffusers with different widths were installed in the compressor. In case the wider diffuser was used, there was the bandwidth (800 to 900 Hz) noise and pressure fluctuation which was closed to 1/2BPF (700 Hz). This fluctuation occurred because the leakage vortices were of two different frequencies. Type 1 vortices are the ones that were discharged from the main blade and covered Passage 1. Type 2 vortices had the same length as Type 1, but they were discharged from the splitter blade. Type 3 vortices covered both Passages 1 and 2; these were discharged from the main blade. Type 3 vortices were generated predominantly at 270°, and their frequency was approximately 700 Hz at 1/2 BPF frequency. The former two types of vortices occurred occasionally, and their frequency was approximately 1400 Hz. Type 3 vortices grew with the wider diffuser because of the higher pressure-recovery, which caused the serous loading to the impeller blades. The broadband noise fluctuation occurred by the coexistence of the two frequency vortices.
Turbopump Design: Comparison of Numerical Simulations to an Already Validated Reduced-Order Model
Authors: Apollonio A , Anderlini A , Valentini D , Pace G , Pasini A , Salvetti M V , D’Agostino L 
Published: May 2021

Abstract
The article expands on the ongoing assessment of the reduced order model proposed by some of the authors for the geometric definition and noncavitating performance evaluation in the preliminary design and parametric optimization of mixed-flow centrifugal turbopumps. Some of the dynamically most significant predictions of the model are compared with the experimentally validated URANS (Unsteady Reynolds-Averaged Navier-Stokes) simulations of the non-cavitating flow through a typical six-bladed unshrouded mixed-flow turbopump for liquid propellant rocket engines operating at both design and off-design flow conditions and different values of the impeller clearance. The observed discrepancies can be explained in terms of the simplifying assumptions introduced for the development of the model and their relative magnitude (< ±10%) does not adversely interfere with the accurate prediction of the turbopump performance over a wide range of operating conditions above and below design flow rate. Together with earlier experimental validations, the results dramatically confirm the capability of the proposed model to generate useful engineering solutions of the turbopump preliminary design problem at a negligible fraction of the computational cost required by 3D numerical simulations.
Coupled Mode Flutter of a Linear Compressor Cascade in Subsonic and Transonic Flow Conditions
Authors: Schuff Matthias , Chenaux Virginie Anne 
Published: May 2021

Abstract
Flutter onset in turbomachinery is typically investigated numerically via decoupled methods due to a high mass ratio of structure to air. The unsteady aerodynamic response of a forced motion vibration is evaluated for a positive or negative work entry. The forced motion simulations assume vacuum mode shape vibrations at certain amplitudes without modal coupling due to aerodynamic forces. This approach, also known as the energy method, is valid for a high blade mass ratio and small logarithmic decrement values. An aeroelastic study of a multi-passage linear compressor cascade was performed. In fluid-structure-coupled time-marching CFD, generic heave and pitch degrees of freedom are allowed to vibrate freely in reaction to any aerodynamic forces. For one subsonic and one transonic flow condition predicted to be stable by the classical energy method approach, aerodynamically coupled-mode flutter is observed. It is shown that variations in the starting conditions, i.e. the initial vibration and inter-blade phase angle of the system, can have a strong influence on the number of CFD iterations required until amplitudes grow. However, if coupled-mode flutter is present in the system, it will ultimately set in at a distinct inter-blade phase angle.
Mitigation Method for Pressure Fluctuations Induced by Acoustic Resonance
Authors: Tsutaya K , Liu Z , Kubo M , Miyagawa K 
Published: May 2021

Abstract
Multi-stage pumps used for boiler water supply of thermal power plants have large capacity and pressure. Fluctuations may cause vibration and noise in pumps, piping systems, and surrounding structures. Lots of studies have been conducted on the pressure fluctuation phenomenon of turbopump piping systems. Some of the factors are the rotor-stator interaction, a resonance between the fluid in the pipe and, excitation source and resonance between structure and pump operation. Besides, studies on mitigation method for pressure fluctuations have been conducted. Inserting orifice to add damping, adjusting the length of pipe to change resonance frequency and, installing resonator to mitigate a specific frequency. However, these studies have not quantified the solution to the pressure fluctuations, so further research is needed to elucidate the causes and establish countermeasures quantitatively. In this study, pressure fluctuations due to acoustic resonance are generated by using a speaker. An orifice, a bent tube, and a branch pipe are installed at the node and antinode of the secondary pressure standing wave in the pipe, and the effects on the standing wave are observed. Moreover, the mitigation method for the pressure standing wave is established by performing a sweep test. Numerical analysis is conducted by AMESim to validate the results of experiment. It is clarified that by inserting the orifice at the appropriate position of a standing wave, pressure fluctuations are mitigated. In the case of branch pipe, pressure fluctuations are effectively mitigated by inserting it having appropriate pipe length and boundary condition.
Control of jet structure utilizing the change in the outlet velocity distribution with time
Authors: Ichihara C , Yamaguchi D , Kobayashi R , Nishibe K , Yokota K , Sato K 
Published: May 2021

Abstract
Flow control using jets is widely implemented. In particular, the clarification of jet technology is indispensable in the control of the blade stall control of blades and for thermal management, such as refrigeration and air conditioning. As part of the fundamental research into the topics mentioned above, various studies of the flow characteristics of steady jets have long been conducted, and the structure of the jets investigated. However, studies on flow control by synthetic jets that essentially exhibit an unsteady flow have begun only recently. Synthetic jets have a flow wherein the jet structure forms downstream of the slot, although the net flow rate is zero, because of repeated ejection and suction. Attempts have been made to control of the jet’s direction of travel by adjusting only the jet’s frequency without any geometric changes. However, many aspects of the effect of oscillation characteristics on the jet’s structure are still unclear. Moreover, since the flow rate is low, it is not suitable for large-scale fluid control, such as that required for high-power fluid machinery. In this study, excited jets are proposed, wherein the velocity distribution change with time at the slot exit and the time-averaged flow rate are considered. An attempt was made to control the jet structure by means of the oscillation characteristics. The influences of the frequency and the phase of the slot outlet velocity distribution on the maximum jet velocity and the jet width were investigated by numerical calculations and experiments. Our research led us to conclude that the staggered vortex street is generated when the phase of the slot exit velocity distribution is π. Further, we concluded that the jet structure could be controlled by the frequency under a certain specific set of conditions.
Design Optimization of High Specific Speed Prototype Francis Turbine by Design of Experiments
Authors: Lee Nak-Joong , Hwang Young-Cheol , Inagaki Morihito , Miyagawa Kazuyoshi 
Published: May 2021

Abstract
In general, Francis turbines are known to last for 40 to 50 years of use. However, exchanging an old turbine for a new is expensive because of modernization costs. Therefore, many modernization projects will take place through new runner changes. The Francis turbine in this paper has a high specific speed of about 330m-kW and a runner diameter of about 4.3m. The new runner can be expected to have a more stable flow and improved performance by flow analysis. In this paper, the performance analysis of the runner was performed using the CFD by Design Of Experiments (DOE). The sensitivity of variables was examined using L18 method. Numerical analysis was performed via BladeGen, Turbogrid, ICEM CFD, and CFX, which are commercial CFD codes. The design goal is to enable not only the best efficiency point but also a more stable operation than before even at partial load conditions. Find out how to find the shape of a runner blade by searching for design points that maximize annual power generation according to newly selected operating conditions.
Heat generation of ball bearing for rocket-engine turbopump in low-temperature gas hydrogen
Authors: Kakudo Hiromitsu , Yokoyama Takashi , Takada Satoshi 
Published: May 2021

Abstract
Cryogenic fluid such as liquid hydrogen, liquid oxygen, and liquid methane is used for rocket propellant because of their performance. Cryogenic fluid turbopump equipped in rocket-engine is started to rotate after precooling bearings is completed. The ball bearing used for the turbopump have worse lubricating performance because the lubricant is not liquid material such as oil which coagulate at cryogenic temperature but solid material. Polytetrafluoroethylene (PTFE) is used for the lubricant in Japanese rocket engines [1]. One of the glass transition temperature of PTFE is around 100 K, and it is considered that the strength of PTFE become weak discontinuously above 100 K and poor lubrication problem would occur in bearings. Ball bearings for turbopump which need to perform high stiffness at high rotation speed don’t meet the performance suddenly when they have any slight damages. Therefore, bearings should be precooled before the engine start so that poor lubrication problems would not occur. However, there is little knowledge of the ball bearing performance in the environment of gas coolant. If ball bearings for turbopumps have good performance in the environment, turbopump can be started to rotate under the insufficient precool environment. It contributes reduction of time and propellant for the precool, and improvement of rocket performance and diversification of space transportation mission are expected. In this study, bearing rotational tests in gas coolant are conducted in the several conditions of the rotational speed and the thrust load in order to clarify the bearing performance for rocket engines in gas coolant.
High-performance ocean energy harvesting turbine design – A strategy of compound leaning
Authors: Ranjith B. , Madhan Kumar P. , Takao Manabu , Samad Abdus 
Published: May 2021

Abstract
Blade leaning works well for steam, hydro and gas turbines, where the flow is unidirectional. In contrary, the turbine used in an oscillating water column wave energy device has a unique design which can work only in bidirectional flow and gives a unidirectional torque. In this article, a compound leaning concept is explored through numerical modelling. An impulse turbine with 0.3m diameter and two rows of guide vanes mirroring each other was considered as a case study. Reynolds-averaged Navier-Stokes equation with k-ε turbulence closure model was solved in ANSYS-CFX code. The present numerical result matches well with the existing experimental results. The modified rotor blade gave 8.8% higher efficiency as it reduced the intensity of trailing edge vortex shedding and the downstream recirculation region.
Experimental determination of turbocharger heat flows for validation of a power separation approach
Authors: Brodbeck Philipp 
Published: May 2021

Abstract
This work presents a new method to measure the heat flow from a turbocharger to the ambient air. The experimental setup, performed on a hot gas test bench, includes an insulated box with two openings, encapsulating the turbocharger. These openings enable a controlled air flow through the box, which is measured at the inlet duct of the box. With temperature measurements at the inlet and outlet of the box, the quantitative heat flow can be calculated. With this information, an approach to estimate those heat flows from standard turbocharger test bench measurements can be validated and refined. The performed measurements at different turbine inlet temperatures and turbine mass flows show a good conformity with expected heat flows. Due to convective and radiative effects, the heat flows increase with both turbine mass flow and turbine inlet temperature. However, the setup with the insulated box has an effect on the overall thermal conditions, since the convection around the turbocharger decreases if the specimen is not as exposed as in common test bench setups.
The Characteristics of Rotordynamic Forces generated by Mechanical Seals
Authors: Inoue H , Yabui S , Inoue T 
Published: May 2021

Abstract
Evaluating rotordynamic reaction force caused by whirl excitation is very effective technique in order to investigate the dynamic properties of the mechanical seal. Especially, it is easy to understand the stability of the rotating component by investigating rotordynamic tangential force. In this paper, the stability of the mechanical seal was discussed by measuring the rotordynamic tangential force depending on the whirl frequency. Judging from the result, the mechanical seal used for this study has stable performance that the tangential force always acts against whirling direction at 1,000 rpm of rotational speed and up to 30 Hz of whirl frequency. Furthermore, whirl frequency ratio and effective damping were calculated using cross-coupled stiffness and direct damping which were obtained by solving quaternary linear equations after whirl excitation test. Whirl frequency ratio was always bellow 1.0, and effective damping was also always positive at all frequencies. Those results indicate that the mechanical seal definitely generate the force to stabilize this whirl vibration.
Effects of Misalignment of Turbine Wheel Hub with Housing
Authors: Wang Yu , Chen Hua , Ma Chao , Sun Jinhui 
Published: May 2021

Abstract
Alignment of a turbocharger turbine rotor hub with its housing can affect aerodynamic performance of the turbine, and studies may have been done in industry to quantify this effect. However, there is no related publication in open literature and so the effect and the underline mechanism remain trade secrets. A numerical investigation into the effect and the mechanism was carried by current authors using two turbine wheels with identical flow passage but different backdisc configurations: one with a full backdisc and the other a deeply scalloped backdisc. For each configuration, five alignments of the wheel hub with housing were studied, these include a full alignment of the rotor hub and the housing and four misalignments of the two turbine components. Effects of the alignment and turbine operating condition on aerodynamic performance of the turbines were studied. The flow field of the turbines was interrogated, and the underline mechanism that produced the performance changes was investigated. The study yields some interesting results: For the full backdisc configuration, the exposure of the backdisc and the wheel recess from housing both decrease turbine efficiency. It has been found that the exposure of the backdisc in the housing outflow creates a stagnation point at the tip of the backdisc, generating some loss. The stagnation then forces the incoming flow to move away from the hub and toward the shroud side of the wheel, producing further losses within the wheel passage. The high pressure at the tip of the backdisc also reduces the flow entering the backdisc cavity between the wheel and heat shield, thus decreases the loss in the cavity. However, this loss is relatively small compared with the loss in the main flow passage. It has also found that the misalignment has greater negative effects on aerodynamic performance of the turbine with deeply scalloped backdisc, and a stronger leakage flow from the backdisc cavity into rotor passage occurs due to the opening in the backdisc by the scalloping. Turbine operating condition has an effect too: lower U/C condition shows higher impacts of misalignment than higher U/C condition. These results are reported and analysed.
Investigation of wind properties at MUTSU Bay and TSUGARU Strait JAPAN
Authors: Honda A , Sasanuma N 
Published: May 2021

Abstract
Present investigation was conducted to confirm the wind properties at Mutsu Bay and Tsugaru Strait by measurement. The wind distribution along the pathway of ferry ship was investigated. Wind speed and wind direction were measured on one of the four ships operated between Aomori Harbour and Hakodate Harbour during 2018. This paper describes the wind properties measured by ferry anemometer.
Emergency department visits and associated healthcare costs attributable to increasing temperature in the context of climate change in Perth, Western Australia, 2012–2019
Authors: Tong Michael Xiaoliang , Wondmagegn Berhanu Yazew , Xiang Jianjun , Williams Susan , Hansen Alana , Dear Keith , Pisaniello Dino , Xiao Jianguo , Jian Le , Scalley Ben , Nitschke Monika , Nairn John , Bambrick Hilary , Karnon Jonathan , Bi Peng 
Published: May 2021

Abstract
Increasing temperature and its impact on population health is an emerging significant public health issue in the context of climate change in Australia. While previous studies have primarily focused on risk assessment, very few studies have evaluated heat-attributable emergency department (ED) visits and associated healthcare costs, or projected future health and economic burdens. This study used a distributed lag non-linear model to estimate heat attributable ED visits and associated healthcare costs from 13 hospitals in Perth, Western Australia, and to project the future healthcare costs in 2030s and 2050s under three climate change scenarios—Representative Concentration Pathways (RCPs)2.6, RCP4.5 and RCP8.5. There were 3697 ED visits attributable to heat (temperatures above 20.5 °C) over the study period 2012–2019, accounting for 4.6% of the total ED visits. This resulted in AU$ 2.9 million in heat-attributable healthcare costs. The number of ED visits projected to occur in the 2030s and 2050s ranges from 5707 to 9421 under different climate change scenarios, which would equate to AU$ 4.6–7.6 million in heat associated healthcare costs. The heat attributable fraction for ED visits and associated healthcare costs would increase from 4.6% and 4.1% in 2010s to 5.0%–6.3% and 4.4%–5.6% in 2030s and 2050s, respectively. Future heat attributable ED visits and associated costs will increase in Perth due to climate change. Excess heat will generate a substantial population health challenge and economic burdens on the healthcare system if there is insufficient heat adaptation. It is vital to reduce greenhouse gas emissions, develop heat-related health interventions and optimize healthcare resources to mitigate the negative impact on the healthcare system and population health in the face of climate change.