Journal of Fluid Science and Technology最新文献

{"title":"Hydrodynamic performance and appendage considerations of wave-piercing planing craft overlapping waves and porpoising","authors":"Sangwon Kim, Sang-eui Lee, Gyoung-Woo Lee, Kwang-cheol Seo, N. Oshima","doi":"10.1115/ajkfluids2019-4931","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4931","url":null,"abstract":"\u0000 This work addresses the numerical study of wave-piercing planing hull and related hydrodynamic performance as the appendages. From the half century ago, the interest in high-speed planing crafts has been advanced toward maintaining performance stably. The main reasons to make it hard are instability motion occurring from porpoising and wave condition. Porpoising is mainly due to overlap the heaving and pitching motion with certain period, which is caused by instable pressure distribution and changing longitudinal location of center of gravity. In addition, in wave condition, encountering wave disturbs going into planing mode. This paper presents numerical results of wave-piercing planing hull in porpoising and wave condition. Numerical simulation is conducted via Reynolds Averaged Navier-stokes (RANS) with moving mesh techniques (overset grid), performed at different wave condition. The results for the behaviors of wave-piercing hull form are practically presented and investigated in this study. The understanding of these phenomena is important for design of appendages of wave-piercing hull-form.","PeriodicalId":44704,"journal":{"name":"Journal of Fluid Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2019-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43181720","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fuel regression behavior of swirling-injection end-burning hybrid rocket engine","authors":"T. Sakurai, Yuya Oishige, Kazuyuki Saito","doi":"10.1299/jfst.2019jfst0025","DOIUrl":"https://doi.org/10.1299/jfst.2019jfst0025","url":null,"abstract":"Typical hybrid rockets, using solid plastic fuel and liquid oxidizer, have the potential to become non-explosive propulsion systems based on boundary layer combustion (Takahashi and Shimada, 2018). This feature enables hybrid rockets to be both safe and low-cost vehicles. However, there are two primary disadvantages in their use as propulsion systems. One is the low fuel regression rate, which results in a low thrust density. The other is the variation in the oxidizerto-fuel mass ratio (O/F shift) during combustion. This is typically observed in a hybrid rocket engine using a single-port fuel grain. To increase the fuel regression rate, low melting temperature fuels, such as paraffin wax, have been applied (Karabeyoglu, 2002). The authors used paraffin wax in a swirling-oxidizer-flow-type hybrid rocket engine (Saito et al., 2012). The fuel regression rate of paraffin wax reached 5 mm/s, which was approximately seven times greater than that of polypropylene under the same oxidizer mass flux. For the O/F shift problem, one of the solutions is the end-burning hybrid rocket engine. In this engine, as the combustion occurs at the end surface of the cylindrical fuel grain, the burned area does not vary with time and, therefore, constant O/F would be realized under constant oxidizer injection conditions. Saito et al. demonstrated constant O/F burning in their axial-injection end-burning hybrid rocket motor under various operation conditions, including thrust throttling (Saito et al., 2018). The authors investigated the swirling-injection end-burning hybrid rocket engine not only to solve the O/F shift problem, but also to obtain a higher regression rate with swirling oxidizer injection. Compared to other studies (Haag et al., 2000; Rice et al., 2003), the novel approach in this study is the combination of swirling-injection end-burning and the use of paraffin wax fuel. Previous studies (Hayashi and Sakurai, 2015; Oishige et al., 2016) reported that the fuel end-surface regressed in the grain axial direction, as anticipated, and the local fuel regression rate had characteristic Abstract Burning experiments were conducted to better understand the fuel regression behavior in a swirling-injection end-burning hybrid rocket engine using paraffin wax/gaseous oxygen propellant. The oxidizer mass flow rate, grain diameter, and the distance between the oxidizer injector and the grain end-surface were the variable parameters taken as influencing the regression rate. The engine attained an overall axial regression rate as high as approximately 5 mm/s, whereas unstable combustion occurred with increasing burning time owing to low melting temperature of paraffin wax. The fuel grain with a diameter of 90 mm also resulted in unstable combustion caused by the initial shallow crack of the cast grain. The radial distribution of the local regression rate exhibited dependency on the radial position and had two peaks: close to the periphery and the middle of the chamber. Fro","PeriodicalId":44704,"journal":{"name":"Journal of Fluid Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1299/jfst.2019jfst0025","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66304250","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of heaving and pitching motions on underside aerodynamics of a sedan vehicle","authors":"Ryuichi Maruyama, Kento Shinji, T. Nonomura, K. Asai","doi":"10.1299/jfst.2019jfst0012","DOIUrl":"https://doi.org/10.1299/jfst.2019jfst0012","url":null,"abstract":"Unsteady pressure distributions around a simplified sedan automobile model were investigated by conducting dynamic wind-tunnel testing using the newly developed forced oscillating apparatus, HEXA-X3, which can produce 6-degrees-of-freedom motion. The effects of heaving and pitching oscillation were investigated as the model simulated a vehicle running on a flat road at approximately 40 m/s and 1 Hz oscillation. The effects of the ground plate on unsteady pressure distributions over the model surfaces were measured while simulating heaving and pitching motion at Strouhal-number conditions similar to those for actual vehicles. The influence of the tubing on the frequency response of the pressure sensor was evaluated to be negligible by conducting a calibration experiment first. In the static case, the overall pressure distribution was consistent with that for a typical sedan, and the influence of the local relative flow velocity changes due to the contraction effect was observed in the underside of the model. In the forced oscillation tests, the effect of heaving and pitching motions on the flow around the underside was investigated. Effects of oscillation parameters, specifically amplitude and frequency, were investigated using the gain and phase-lag normalized by data from the steady model. Results of the test indicate that there is a characteristic distribution in pressure fluctuation, and the phenomena that become dominant in the flow around the underside vary according to location. The dynamic heaving motion was shown to change the pressure distribution, possibly due to changes in the effective angle of attack in addition to the static effect. The pitching test showed that a dynamic camber effect works in addition to those effects.","PeriodicalId":44704,"journal":{"name":"Journal of Fluid Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1299/jfst.2019jfst0012","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66302966","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Numerical investigation of geometrical corrugation influence to vortex flowfields at low Reynolds number","authors":"Y. Yamaguchi, D. Sasaki, M. Okamoto, K. Shimoyama, S. Obayashi","doi":"10.1299/jfst.2019jfst0018","DOIUrl":"https://doi.org/10.1299/jfst.2019jfst0018","url":null,"abstract":"Micro Air Vehicle (MAV) are often utilized for the disaster spot, ecosystem observation and topography investigation these days. Because the full length of the body is centimeter scale, the Reynolds number of MAV becomes low (10-10). A laminar separation bubble is formed in low Reynolds number unlike a high Reynolds number domain because the viscous term becomes dominant. Numerical and experimental analysis of high performance airfoils in low Reynolds number flow is proposed (M. Anyoji et al., 2014). In low Reynolds number flows, flat plate or thin wings have better aerodynamic performance compared to thick streamlined airfoils. However, there are still many problems with related to the aerodynamic performance. For example, batteries tend to be heavy and the thrust is not sufficient in low Reynolds number. These results would be useful in designing low Reynolds number aircraft such as micro-air vehicles. For example, an insect-sized MAV was proposed by (Wood et al., 2012) and (Kroo and Kunz., 2001).","PeriodicalId":44704,"journal":{"name":"Journal of Fluid Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66303479","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of mainstream velocity and setting position on flow separation control of a curved wall using plasma actuators","authors":"T. Matsunuma, T. Segawa","doi":"10.1299/JFST.2019JFST0007","DOIUrl":"https://doi.org/10.1299/JFST.2019JFST0007","url":null,"abstract":"Dielectric barrier discharge (DBD) plasma actuators were used for the active control of flow separation on a curved wall simulated suction surface of a gas turbine blade at three different mainstream velocities, UMS = 2.2 m/s, 4.1 m/s, and 6.3 m/s. Owing to the change in mainstream velocity, the Reynolds number was varied as Re = 1.7 × 104, 3.1 × 104, and 4.7 × 104, respectively. Particle image velocimetry system was used to obtain two-dimensional velocity field measurements. The amplitude of input voltage for the plasma actuator was changed from ±2.0 kV to ±4.0 kV. At the lower mainstream velocity, UMS = 2.2 m/s (Re = 1.7 × 104), the separated flow induced on a curved wall was consider-ably reduced by the flow control using the DBD plasma actuator. Moreover, the effect of flow control by the plasma actuator was gradually reduced at the higher mainstream velocities, UMS = 4.1 m/s and 6.3 m/s (Re = 3.1 × 104 and 4.7 × 104, respectively). The flow control effect was improved by changing the position of the plasma actuator. When the plasma actuator was positioned immediately before the separation point, it exhibited better flow control effects than when positioned immediately behind the separation point.","PeriodicalId":44704,"journal":{"name":"Journal of Fluid Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66302982","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Shape optimization analysis considering a rotational body in a flow field based on the adjoint variable and the finite element methods","authors":"T. Kurahashi, Y. Ozeki, E. Katamine","doi":"10.1299/JFST.2019JFST0004","DOIUrl":"https://doi.org/10.1299/JFST.2019JFST0004","url":null,"abstract":"","PeriodicalId":44704,"journal":{"name":"Journal of Fluid Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1299/JFST.2019JFST0004","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66303252","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Study on heat transportation of an impinging jet interfering with a Couette flow (comparison with Poiseuille flow)","authors":"Jumpei Kitayama, T. Kubo","doi":"10.1299/JFST.2019JFST0006","DOIUrl":"https://doi.org/10.1299/JFST.2019JFST0006","url":null,"abstract":"Paper No.19-00079 © 2019 The Japan Society of Mechanical Engineers [DOI: 10.1299/jfst.2019jfst0006] Abstract In this study, we compare the flow and temperature fields of a heated impinging jet interfering with a Couette flow and a Poiseuille flow through numerical simulations. We find that the instantaneous vortex structure in the Couette main flow has some periodicity and affects the heat transfer on the jet impinging surface. In time-averaged flow and temperature fields, the Nusselt number shows unique distributions. Further, a counter-rotating vortex pair is extracted, similar to the previously reported studies on a jet in a cross flow. It is found that this vortex pair involves the main flow fluid and causes a unique Nusselt number distribution. The overall heat transfer in the Couette main flow is lower than that in the Poiseuille main flow. From the mean velocity field, a back current occurs behind the jet inlet, which is similar to the separation in the wake flow of a cylinder crossing the main flow. In addition, the fluctuation velocity in the Couette main flow does not spread wider than that in the Poiseuille main flow, and high velocity fluctuations concentrate on the front edge of the jet flow. The distributions of both mean and fluctuation velocities of the Couette flow interfering with the jet are similar to those of the turbulent Couette flow.","PeriodicalId":44704,"journal":{"name":"Journal of Fluid Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1299/JFST.2019JFST0006","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66303378","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thermo-fluid dynamic design optimization of a concentric tube heat exchanger","authors":"T. Hirano, Mitsuo Yoshimura, K. Shimoyama, A. Komiya","doi":"10.1299/jfst.2019jfst0011","DOIUrl":"https://doi.org/10.1299/jfst.2019jfst0011","url":null,"abstract":"This study proposes a shape optimization approach for the cross-sectional shape of the inner pipe of a counter-flow concentric tube heat exchanger. The cross-sectional shape of the inner pipe is expressed by an algebraic expression with a small number of parameters, and their heat transfer performance is evaluated by a commercial Computational Fluid Dynamics (CFD) solver. The optimization is conducted by the Non-Dominated Sorting Genetic Algorithm II (NSGA-II) assisted by the Kriging surrogate model, and the NSGA-II finds the optimal cross-sectional shape with many protrusions around the perimeter of the inner channel to improve the heat transfer performance. In this study, heat transfer performance is evaluated from the temperature drop at the outlet of the high-temperature fluid. The present optimization finds the optimal channel with many protrusions, which achieves lower outlet temperature than a circular channel even with the same heat transfer surface area. This result indicates that the number of protrusions plays important roles which contribute not only to increase heat transfer area but also to improve heat transfer performance.","PeriodicalId":44704,"journal":{"name":"Journal of Fluid Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66303397","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fundamental study on cooling of biological phantom using ice slurry in limited space","authors":"T. Okabe, H. Nishikawa, Taimei Miyagawa, T. Inamura, K. Fumoto","doi":"10.1299/jfst.2019jfst0020","DOIUrl":"https://doi.org/10.1299/jfst.2019jfst0020","url":null,"abstract":"Paper No.19-00166 © 2019 The Japan Society of Mechanical Engineers [DOI: 10.1299/jfst.2019jfst0020] Abstract The cooling process of a biological phantom using ice slurries with different geometries in a limited space was experimentally investigated. Ice slurry has recently been considered to as a solution to cool organs in the abdominal cavity efficiently and rapidly to suppress biological reactions during minimally invasive laparoscopic surgeries. However, previous studies have not focused on the interactions between ice slurry and biological tissues in the abdominal area. In this study, we aimed to investigate the effects of ice slurry geometry, enclosure width Lw, and mimic-blood flow rate Qb on the cooling of a biological phantom using ice slurry in a limited space. We prepared the same volume of ice slurry using different geometries with an ice packing factor of 25 wt% using a scraper-type method to place on the phantom surface. We observed the melting behaviors of the ice slurries and measured the surface and core temperatures of the biological phantom. It was found that the supply methods of the ice slurry affected the cooling of biological tissues significantly. When the ice slurry width was the same as that of the enclosure, the ice slurry floated on the melted slurry and inhibited the cooling of the biological phantom. When the slurry width was small compared to that of the enclosure, the slurry remained in contact with the phantom, thus resulting in its efficient and rapid cooling. The mimic-blood flow promoted the melting of the ice slurry increased the heat flux on the phantom surface. However, the core temperature was not affected. Thus, the core temperature cannot be reduced unless the blood flow is occluded.","PeriodicalId":44704,"journal":{"name":"Journal of Fluid Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1299/jfst.2019jfst0020","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66303638","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Melting heat transfer in rectangular cavity filled with ice slurry heated from below","authors":"Taimei Miyagawa, T. Okabe, Takuro Miyanishi, T. Kogawa, H. Murata, K. Fumoto","doi":"10.1299/jfst.2019jfst0021","DOIUrl":"https://doi.org/10.1299/jfst.2019jfst0021","url":null,"abstract":"Ice slurry is a homogeneous mixture of small ice particles and a carrier liquid. It is widely used in many fields. Previous studies have gradually clarified its heat transfer in high ice packing factor (IPF). However, only a few studies have focused on the mechanism of heat transfer with low IPF in a cavity heated from below. The objective of this study is to experimentally clarify the melting heat transfer of ice slurry in a cavity heated from below with low IPF to develop a direct contact medical cooling system. To observe the melting behavior of ice slurry, the test section was made of acrylic resin (100 mm × 60 mm× 30 mm) and a silicone rubber heater that was used for heating under constant heat flux conditions. We measured the surface temperature of the heater and the liquid thickness. We showed that the melting process can be divided into three stages. In the first stage, heat conduction dominated the process of heat transfer and the temperature of the heater rapidly increased. In the second stage, natural convection heat transfer dominated the process of heat transfer that increased the melting rate of ice slurry and decreased the temperature of the heater. In the third stage, heat conduction dominated the process of heat transfer in the concentration stratification. This led to a decrease in the melting rate and an increase in the temperature of the heater. Our result also showed that the melting process of the ice slurry is slow enough to consider it the quasi-steady state in the range of 104 < Ra∗ < 107 as compared to the development of the velocity and temperature fields.","PeriodicalId":44704,"journal":{"name":"Journal of Fluid Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1299/jfst.2019jfst0021","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66303692","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}