著者

Masahiro KANAZAKI Kai TOMISAWA Koji FUJITA Akira OYAMA Hiroki NAGAI

出版者

The Japan Society of Mechanical Engineers

雑誌

Journal of Fluid Science and Technology (ISSN:18805558)

巻号頁・発行日

vol.14, no.3, pp.JFST0017, 2019 (Released:2019-12-19)

参考文献数

11

被引用文献数

1

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We redesigned the Mars Airplane Balloon Experiment Two (MABE-2) based on MABE-1 to improve the vehicle’s stability and controllability. Following the redesign, the MABE-2 vehicle had a larger horizontal tail volume than that of MABE-1 for improved stability performance. In addition, to further improve the stability and control characteristics, a rectangular planform was employed for the horizontal tail wing; in contrast, MABE-1 had a tapered planform. The vertical tail position of MABE-2 was moved to the end of the horizontal tail wing, because the vertical tail of MABE-1, which was positioned at the mid span of the horizontal tail wing, showed aerodynamic interaction with the horizontal tail wing. In this paper, we discussed the aerodynamic performance of a control surface based on computational fluid dynamics with variation in the deflection angle between the control surface and the horizontal tail (elevator), and we examined the effects of this redesign on longitudinal control characteristics. Numerical investigations confirmed the linear variation in the pitching moment and the aerodynamic force with the changing elevator deflection angle in MABE-2. Surface pressure observations indicated that MABE-2 shows a smooth variation in the pressure distribution with changing elevator deflection angle, while MABE-1 does not. These results demonstrate that the aerodynamic control characteristics of MABE-2 were improved in comparison to those of MABE-1.

著者

Yutaro MOTOORI Susumu GOTO

出版者

The Japan Society of Mechanical Engineers

雑誌

Journal of Fluid Science and Technology (ISSN:18805558)

巻号頁・発行日

vol.14, no.3, pp.JFST0016, 2019 (Released:2019-12-19)

参考文献数

16

被引用文献数

3

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Coarse-graining is indispensable for extracting a hierarchy of vortices in fully developed turbulent flow with multiscale nature. In the present study, for a high-Reynolds-number turbulent boundary layer, we employ two simple coarse-graining methods in real space; namely, a Gaussian filter and the combination of the Gaussian filters at two scales. The former corresponds to a low-pass filter of Fourier modes, while the latter corresponds to a band-pass filter. We also examine two different filter widths for the band-pass filter. Then, we show difference in the statistics of the three filtered fields. Since the velocity gradients in turbulence are mainly determined by the smallest-scale motions, vortical structures identified by the second invariant Q of the velocity gradient coarse-grained by the filters are similar. However, there is difference between low- and band-pass filtered fields in the contribution to the enstrophy production rates. This is because the production rates are determined not only by the magnitude of the strain rates but also by the alignment between the vorticity and the stretching direction. In addition, since vortices are not created in the entire system, the conditional sampling by the value of Q is essential to understand the generation mechanism of the hierarchy of vortices. The conditional analysis of the band-pass filtered fields demonstrates that small-scale vortices in the log layer are stretched by twice-larger vortices, whereas they weaken the twice-larger vortices. This observation is consistent with the picture of the energy cascade. We also show that when using the band-pass filter, these conclusions are robust irrespective of the choice of the filter width.

著者

Masahiro KANAZAKI Shoma ITO Fumio KANAMORI Masaki NAKAMIYA Koki KITAGAWA Toru SHIMADA

出版者

一般社団法人 日本機械学会

雑誌

Journal of Fluid Science and Technology (ISSN:18805558)

巻号頁・発行日

vol.11, no.1, pp.JFST0003-JFST0003, 2016 (Released:2016-02-17)

参考文献数

8

被引用文献数

1

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This paper reports on the conceptual design of a three-stage launch vehicle (LV) with a clustered hybrid rocket engine (HRE) through multi-disciplinary design optimization. This LV is a space transportation concept that can deliver micro-satellites to sun-synchronous orbits (SSOs). To design a high-performance LV with HRE, the optimum size of each component, such as an oxidizer tank containing liquid oxidizer, a combustion chamber containing solid fuel, a pressurizing tank, and a nozzle, should be determined. In this study, paraffin (FT-0070) is used as a propellant for the HRE, and three cases are compared: In the first case, HREs are optimized for each stage. In the second case, HREs are optimized together for the first and second stages but separately for the third stage. In the third case, HREs are optimized together for each stage. The optimization results show that the performance of the design case that uses the same HREs in all stages is 40% reduced compared with the design case that uses optimized HREs for each stage.

著者

Tomoki YAMAZAKI Yoshiaki ABE Tomonaga OKABE

出版者

The Japan Society of Mechanical Engineers

雑誌

Journal of Fluid Science and Technology (ISSN:18805558)

巻号頁・発行日

vol.18, no.2, pp.JFST0026, 2023 (Released:2023-06-28)

参考文献数

38

被引用文献数

1

---

A flapping wing is considered as one of the most effective aerodynamic systems for micro air vehicles (MAVs). Many numerical studies have been attempted to investigate the flow field around a flapping wing; nevertheless, the long-term flow characteristics, which can cause a non-negligible effect on long-term hovering operations of MAVs have not been adequately clarified owing to the high computational cost involved. This study numerically investigates the long-term flow characteristics around a flapping flat-plate wing during hovering flight at a chord-based Reynolds number of 2.5 × 104. Based on the finite-volume method with the arbitrary Lagrangian-Eulerian (ALE) method, two-dimensional laminar flow analyses were performed for 40 periods of flapping motions with stroke inversion angles of β = 30°, 45°, and 60°. The results showed that the lift coefficient CL was not completely periodic despite the periodic motion. To identify the CL characteristics for each β case, a half-stroke-period-based phase-average of CL was calculated over different time segments. Then, the phase-averaged CL using the fifth to 30th periods sufficiently provided converged aerodynamic characteristics: the β = 30° and 45° cases had a single peak of CL, whilst the β = 60° had double peaks; the second peak taking the maximum CL in the β = 60° case was delayed compared to others. The results of this study provide a guideline for the number of periods required in the numerical estimation of the CL characteristics and associated flow fields around flapping-type MAVs, which contributes to their further improvement of them.

著者

Tatsuhiko IMAI Kenya KONDO Yasumasa SUZUKI Yuya MIKI

出版者

The Japan Society of Mechanical Engineers

雑誌

Journal of Fluid Science and Technology (ISSN:18805558)

巻号頁・発行日

vol.18, no.1, pp.JFST0022, 2023 (Released:2023-04-26)

参考文献数

38

---

In this study, oil film interferometry (OFI) was applied to the flow around the suction surface of a two-dimensional airfoil under high lift conditions to measure the wall shear stress. However, existing OFI methods have difficulty measuring the wall shear stress in images affected by reverse and secondary flows. Therefore, the particle image velocimetry (PIV) method was applied to the Fizeau fringe images to determine the direction of progress from the calculated velocity vector. An airfoil with a wing section of NACA0012 was used, the Reynolds number was set to 8 × 104, and angle of attack was set at 11°. A direct spatial domain correlation was used for the PIV analysis method. At x/c = 0.75 to 0.83, the measured local skin friction coefficient was good agreeing with the large eddy simulation calculated results reported by Miyazawa et al. (Transaction of the JSME, Series B, Vol.72, No.721 (2006)). However, a large difference between the measured and calculated local skin friction coefficients occurred at x/c = 0.17 near the re-attachment point. The wall shear stress is determined by calculating the dominant frequencies using fast Fourier transform (FFT) analysis from the matrix data obtained by mean of the pixel intensities in the analysis region in the span direction. If the Fizeau fringe image is uniform in the span direction, the program can calculate the periodic waves. When the Fizeau fringes are tilted to the analysis range, the FFT analysis of the obtained matrix data results in an error because the dominant frequency cannot be calculated. Therefore, velocity vectors were detected near the re-attachment point by adapting PIV to the Fizeau fringe images. The local skin friction coefficients were calculated by OFI measurements with the Fizeau fringe images that were rotated by the angle of the velocity vector determined by PIV.

著者

Kosuke SUZUKI Masaya KOUJI Masato YOSHINO

出版者

The Japan Society of Mechanical Engineers

雑誌

Journal of Fluid Science and Technology (ISSN:18805558)

巻号頁・発行日

vol.18, no.1, pp.JFST0011, 2023 (Released:2023-04-26)

参考文献数

24

---

We conducted measurements of a butterfly’s motion in forward flight and numerical simulations using a computational model reflecting its motion. We measured the motion of a cabbage white butterfly (Pieris rapae), and then we constructed a computational model composed of a thorax, an abdomen, and four wings (i.e., left and right wings with fore and hind parts). Furthermore, we calculated the flow field and aerodynamic force and torque generated by the butterfly model using the immersed boundary–lattice Boltzmann method. In this simulation, we considered two types of periodic motions corresponding to slightly-descending and ascending forward flights. As a result, we found that the wing-tip and leading-edge vortices are formed on the wings and then released backward and downward in both flights. The major difference between the two flights is the flapping amplitude, indicating that the butterfly changes the flapping amplitude for each period and increases it to ascend. In addition, we considered a chimera model whose motion is based on the slightly-descending flight but partly given by the ascending flight. As a result, we found that the pitching angle and the angle of attack determine the traveling direction, but simply changing these angles does not achieve the ascending flight due to insufficient lift force. Thus, the butterfly should adjust the flapping and lead–lag angles in response to the pitching angle and the angle of attack to change the flight mode.

著者

Naoya UENE Hideki TAKEUCHI Yasutaka HAYAMIZU Takashi TOKUMASU

出版者

The Japan Society of Mechanical Engineers

雑誌

Journal of Fluid Science and Technology (ISSN:18805558)

巻号頁・発行日

vol.15, no.1, pp.JFST0005, 2020 (Released:2020-01-30)

参考文献数

23

被引用文献数

1 6

---

We consider a Couette flow of a rarefied Ar gas with heat transfer between two wall surfaces and investigate the scattering behavior of gas molecules reflected either at a clean Pt surface or at a surface contaminated with adsorbates. Water molecules abundantly present in the atmosphere were adopted as the adsorbates. The reflection of gas molecules on the lower wall surface was simulated by Molecular Dynamics (MD) method to obtain accommodation coefficients and velocity distribution functions of gas molecules. We applied the modified reflection model of gas molecule and investigated the velocity distribution functions of the model by comparing the MD results to verify the validity. The accommodation coefficients obtained by the MD method depend on the number of adsorbed water molecules on the lower wall surface. Specifically, tangential momentum accommodation coefficient (TMAC) tended to increase and then decrease with the increase in adsorbed water molecules, but normal momentum accommodation coefficient (NMAC) tended to decrease monotonically. The velocity distribution functions of the modified reflection model approximately show the good agreement with the MD calculation but the degree of coincidence depends on the speed difference between the upper and lower wall surfaces, and the number of adsorbed water molecules on the surface.

著者

Koji MIYAJI Hiroto TAKEGAWA

出版者

The Japan Society of Mechanical Engineers

雑誌

Journal of Fluid Science and Technology (ISSN:18805558)

巻号頁・発行日

vol.17, no.2, pp.JFST0004, 2022 (Released:2022-07-13)

参考文献数

21

---

A new computation method to predict a transonic wing flutter under the limit-cycle oscillation (LCO) is developed using the time spectral (TS) method. The fluid and structural unknowns at a specified time interval in one cycle of the flutter are obtained by steady-state solutions of the aeroelastic TS equations, and thus higher computational efficiency is expected. Determining the frequency is the key for the flutter prediction, and we propose a method of minimizing the residuals of the fluid equation. The time histories of the plunge and pitch are reconstructed by the discrete Fourier transform, and compared with the existing time marching (TM) method. The effects of the number of harmonics in the TS and the time-step size in the TM are examined for the detailed comparison. The frequency, amplitude, and phase differences between the structural vibration modes all well agree between the two methods for a wide range of flutter speed index. Complex flutter boundaries are also predicted. The TS method is faster to reach the LCO than the TM method for the first vibration mode of the flutter. It is slower for the second vibration mode, but the increase in the computation time is much smaller than the reduction in the first mode. In general, the TS method is particularly advantageous for the prediction near flutter boundaries and is useful for aircraft design.

著者

Masato YAMAGISHI Yusuke YAHAGI Masanori OTA Yusuke HIROSE Shinsuke UDAGAWA Tatsuro INAGE Shigeya KUBOTA Koji FUJITA Kiyonobu OHTANI Hiroki NAGAI

出版者

The Japan Society of Mechanical Engineers

雑誌

Journal of Fluid Science and Technology (ISSN:18805558)

巻号頁・発行日

vol.16, no.3, pp.JFST0021, 2021 (Released:2021-10-01)

参考文献数

16

被引用文献数

4

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Three-dimensional density measurement of unsteady flow field around a projectile (φ = 8mm) is carried out in the ballistic range at Institute of Fluid Science, Tohoku University. The purpose of this study is to obtain the density distribution including its wake region in non-axisymmetric unsteady flow. The projectile’s Mach number in the experiment is 1.35. Simultaneous multi-angle BOS measurement system using twelve digital cameras and pulsed LEDs is installed in the test chamber of the ballistic range. The Color-Grid Background Oriented Schlieren (CGBOS) technique is used in the measurement system to obtain the projection data of density gradient. Algebraic Reconstruction Technique (ART) method and Successive Over Relaxation (SOR) method are used to obtain the density distribution from projection data. To improve the accuracy of 3D reconstruction, we evaluate the view-angle of the measurement system in the present study. The result shows that the bow shock, expansion wave and recirculation zone can be confirmed by the proposed method. However, bow shock in each method are thicker than the schlieren image due to the blur of the CGBOS images. Even then, the 3D shape of density distribution reconstructed by proposed method can be reliable, and the relative error of obtained density between the theoretical value for normal shock relation is about 5% at the bow shock.

著者

Kota TOMIUKA Yu NISHIO Seiichiro IZAWA Yu FUKUNISHI

出版者

The Japan Society of Mechanical Engineers

雑誌

Journal of Fluid Science and Technology (ISSN:18805558)

巻号頁・発行日

vol.15, no.1, pp.JFST0001, 2020 (Released:2020-01-01)

参考文献数

23

被引用文献数

1

---

In this study, the receptivity of a flat-plate boundary layer was studied by introducing a thin sheet-type disturbance. An airfoil-shaped device was used to generate a thin disturbance without velocity deficit in which a steady jet was ejected from its trailing edge to the downstream. Despite the absence of strong disturbances in the freestream outside the boundary layer, streaky structures similar to an ordinary bypass transition were generated. They meandered slowly in the spanwise direction where their downstream parts were oscillating in a delayed fashion. Turbulent spots were formed in the further downstream region. Consequently, the energy growth of the low frequency band in the velocity fluctuation spectrum was found to originate from this meandering motion of the streaks, whereas the growth of the middle- and high-frequency bands was attributed to the appearances of the turbulent spots.

著者

Kohei OZAWA Toru SHIMADA

出版者

The Japan Society of Mechanical Engineers

雑誌

Journal of Fluid Science and Technology (ISSN:18805558)

巻号頁・発行日

vol.13, no.4, pp.JFST0031, 2018 (Released:2018-11-09)

参考文献数

31

被引用文献数

7

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The characteristics of several O/F control methods for hybrid rocket propulsion have been discussed and theoretically analyzed from the physical properties of propellants and fuel regression behavior. In this research, comparisons have been made among different oxidizer injection methods of Altering-intensity Swirling Oxidizer Flow Type (A-SOFT), Aft-chamber Oxidizer Injection Method (AOIM), and Swirling-AOIM for the throttle range with a constant O/F, design restrictions of the fuel grain, penalties on the adoption of the methods, and suitable scales of the engine. Theoretical analysis on regression rates has revealed that A-SOFT has upper and lower limits of throttle while maintaining a constant O/F whereas AOIM does not have any lower limit, and Swirling-AOIM covers both the throttle ranges. The designing restriction of the fuel grain derived from the regression rate behavior has indicated that A-SOFT using paraffin and oxygen has a potential to maintain 50-100% throttle range over a burn. The penalties for the adoption of these O/F control methods have also been discussed from the aspects of the increase in the complexity of the system, structural mass, and pressure drop at the injector for the methods using gaseous injection. The pressure drop has quantitatively been evaluated by relating the available swirl strength with the cross-sectional area and gaseous oxidizer mass flux at the injector. This analysis has revealed 5 times difference in the available swirl strength between the gaseous oxygen and the decomposed gas of 90% hydrogen peroxide. The sizing of the 1st stage of the satellite launcher has revealed that A-SOFT and Swirling-AOIM are suitable for small-scale engines with a propellant mass of 100-102 [ton] using paraffin and liquid oxygen whereas AOIM and Swirling-AOIM are suitable for engines with paraffin and 90% hydrogen peroxide.

著者

Tomohiro HIRANO Mitsuo YOSHIMURA Koji SHIMOYAMA Atsuki KOMIYA

出版者

The Japan Society of Mechanical Engineers

雑誌

Journal of Fluid Science and Technology (ISSN:18805558)

巻号頁・発行日

vol.14, no.2, pp.JFST0011, 2019 (Released:2019-11-07)

参考文献数

21

被引用文献数

2

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This study proposes a shape optimization approach for the cross-sectional shape of the inner pipe of a counterflow 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.

著者

Masahiro KANAZAKI Fumio KANAMORI Yosuke KITAGAWA Masaki NAKAMIYA Koki KITAGAWA Toru SHIMADA

出版者

一般社団法人 日本機械学会

雑誌

Journal of Fluid Science and Technology (ISSN:18805558)

巻号頁・発行日

vol.9, no.5, pp.JFST0071-JFST0071, 2014 (Released:2014-11-28)

参考文献数

6

被引用文献数

2

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The subject of this paper is to improve on parameterization for conceptual design method of three stage hybrid rocket. Multi-Objective Genetic Algorithm (MOGA) is employed to solve multi-disciplinary design exploration of a three-stage launch vehicle concept using a hybrid rocket engine. MOGA which is used as the optimization methods for multi-objective problems utilizes real-number cording and the Pareto ranking method. According to our previous study, the propulsive performance of MOGA's solution was as low as the lower limit of design space. The design space of a conceptual three-stage launch vehicle hybrid rocket engine was reconsidered based on the results of multi-disciplinary design optimization. The design variables of the nozzles were reconsidered by exploring the design space. Specifically, the nozzle expansion ratio was considered as the ratio of the nozzle exit radius to the body radius. In this way, there are no solutions which violate the design constraints about the geometric condition of the nozzle exit. Consequently, the new conceptual design method can effectively explore solutions which have higher propulsive performance than previous method. As the result, the combustion chamber pressure is increased in the first stage. In the second stage, the solutions which are explored, modified parameterization are shown larger thrust level than previously.

著者

Junichi OHTA Masahiro IGUCHI Masahito ONARU

出版者

一般社団法人 日本機械学会

雑誌

Journal of Fluid Science and Technology (ISSN:18805558)

巻号頁・発行日

vol.9, no.1, pp.JFST0009-JFST0009, 2014 (Released:2014-06-05)

参考文献数

23

---

Progressive ultrasonic waves cause acoustic streaming in a liquid. Although theoretical and experimental studies on acoustic streaming for liquid phase have been carried out, acoustic streaming for a solid-liquid mixture does not seem to have been investigated. The purpose of this study is to clarify the velocity distribution of acoustic streaming in a solid-liquid mixture. An ultrasonic wave with a frequency of 485 kHz was horizontally irradiated on tap water with aluminum particles in a cylindrical tube with a diameter of 120 mm whose orientation was kept horizontal; the acoustic streaming velocities were measured with the irradiation time of the ultrasonic wave, initial particle concentration, and particle shape as the parameters. The following results were obtained: (a) The higher the initial particle concentration is, the faster the acoustic streaming velocity of a solid-liquid mixture becomes;(b) When ultrasonic waves are irradiated on a liquid with heavier solid particles, the acoustic streaming velocity of the solid-liquid mixture decreases with irradiation time to a certain extent.

著者

MIAU Jiun-Jih TU J. K. LIAO T. W.

出版者

The Japan Society of Mechanical Engineers

雑誌

Journal of Fluid Science and Technology (ISSN:18805558)

巻号頁・発行日

vol.4, no.2, pp.415-429, 2009

被引用文献数

5

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Unsteady, three-dimensional characteristics of vortex shedding were studied with self-made MEMS sensors situated spanwisely on a circular cylinder subjected to uniform incoming flow. Firstly, verification on the reliability of the MEMS sensor signals was made by comparing with the hot-wire signals obtained in the flow simultaneously. Subsequently, the MEMS sensor signals were analyzed with Wavelet and Hilbert transformations and 2D-FFT. By Wavelet and Hilbert transformations, the results obtained indicate that the strongly three-dimensional vortex shedding events are featured with pronounced spanwise variations in the instantaneous phases of vortex shedding, which are further identified as the occurrences of vortex dislocation. Furthermore, the results of 2D-FFT analysis reveal that the spanwise wave numbers of vortex shedding largely falls in a range between -2 to 2, for the MEMS sensors spanned over a spanwise region of 3 D in length.