The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Hiroyuki Haniu - One of the best experts on this subject based on the ideXlab platform.
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generation of new frequencies by nonlinear interaction between different vortex Shedding frequencies in span wise direction of a stepped circular cylinder
Transactions of the Japan Society of Mechanical Engineers. B, 2007Co-Authors: W U Ping, Hiroyuki Haniu, Katsumi MiyakoshiAbstract:It is known that the low-Frequency fluctuation about 1/20 of vortex Shedding Frequency exists in the irregularity of the vortex Shedding from a two-dimensional circular cylinder. Local vortex Shedding Frequency in spanwise direction is considered to differ from one point to another due to different local Strouhal number caused by flow three-dimensionality. Therefore, nonlinear interaction between vortex Shedding cells of different frequencies is considered to be the cause of the low-Frequency fluctuation. In this study, two distinctive different vortex Shedding frequencies have been forced to occur at a local spanwise position with use of a stepped circular cylinder, and modified particular phase difference TSC (Trans-Spectral Coherence) analysis was conducted to investigate the presence of quadratic (or second order) nonlinear interaction in the wake. It is expected that the quadratic nonlinear interaction is generated as the result of complicated interaction between spanwise vortex cells of different frequencies.
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the formation mechanism and Shedding Frequency of vortices from a sphere in uniform shear flow
Journal of Fluid Mechanics, 1995Co-Authors: Hiroshi Sakamoto, Hiroyuki HaniuAbstract:Experiments to investigate the formation mechanism and Frequency of vortex Shedding from a sphere in uniform shear flow were conducted in a water channel using flow visualization and velocity measurement. The Reynolds number, defined in terms of the sphere diameter and approach velocity at its centre, ranged from 200 to 3000. The shear parameter K, defined as the transverse velocity gradient of the shear flow non-dimensionalized by the above two parameters, was varied from 0 to 0.25. The critical Reynolds number beyond which vortex Shedding from the sphere occurred was found to be lower than that for uniform flow and decreased approximately linearly with increasing shear parameter. Also, the Strouhal number of the hairpin-shaped vortex loops became larger than that for uniform flow and increased as the shear parameter increased.The formation mechanism and the structure of vortex Shedding were examined on the basis of series of photographs and subsequent image processing using computer graphics. The range of Reynolds number in the present investigation, extending up to 3000, could be classified into three regions on the basis of this study, and it was observed that the wake configuration did not differ substantially from that for uniform flow. Also, unlike the detachment point of vortex loops in uniform flow, which was irregularly located along the circumference of the sphere, the detachment point in shear flow was always on the high-velocity side.
Hiroshi Noguchi - One of the best experts on this subject based on the ideXlab platform.
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polymer effects on karman vortex molecular dynamics study
Journal of Chemical Physics, 2018Co-Authors: Yuta Asano, Hiroshi Watanabe, Hiroshi NoguchiAbstract:We investigated the Karman vortex behind a circular cylinder in a polymer solution by a molecular dynamics simulation. The vortex characteristics are distinctly different for short and long polymers. The solution with the long polymer exhibits a reduction in the vortex Shedding Frequency and broadening of the lift coefficient spectrum. On the other hand, the characteristics of the short-polymer solution are almost the same as those of the Newtonian fluid. These facts are consistent with the experiments. Because the distributions of the gyration radius and the orientational order of the long-polymer solution are highly inhomogeneous in the flow field, we conclude that the extensional property of the polymer plays an important role in changing the flow characteristics.
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polymer effects on karman vortex molecular dynamics study
arXiv: Soft Condensed Matter, 2018Co-Authors: Yuta Asano, Hiroshi Watanabe, Hiroshi NoguchiAbstract:We investigated the Karman vortex behind a circular cylinder in a polymer solution by a molecular dynamics simulation. The vortex characteristics are distinctly different for short and long polymers. The solution with the long polymer exhibits a reduction in the vortex Shedding Frequency and broadening of the lift coefficient spectrum. On the other hand, the characteristics of the short-polymer solution are almost same as those of the Newtonian fluid. These facts are consistent with the experiments. Because the distributions of the gyration radius and the orientational order of the long-polymer solution are highly inhomogeneous in the flow field, we conclude that the extensional property of the polymer plays an important role in changing the flow characteristics.
Horst Bleckmann - One of the best experts on this subject based on the ideXlab platform.
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determination of object position vortex Shedding Frequency and flow velocity using artificial lateral line canals
Beilstein Journal of Nanotechnology, 2011Co-Authors: Adrian Klein, Horst BleckmannAbstract:The lateral line system of fish consists of superficial neuromasts, and neuromasts embedded in lateral line canals. Lateral line neuromasts allow fish to sense both minute water motions and pressure gradients, thereby enabling them to detect predators and prey or to recognize and discriminate stationary objects while passing them. With the aid of the lateral line, fish can also sense vortices caused by an upstream object or by undulatory swimming movements of fish. We show here that artificial lateral line canals equipped with optical flow sensors can be used to detect the water motions generated by a stationary vibrating sphere, the vortices caused by an upstream cylinder or the water (air) movements caused by a passing object. The hydrodynamic information retrieved from optical flow sensors can be used to calculate bulk flow velocity and thus the size of the cylinder that shed the vortices. Even a bilateral sensor platform equipped with only one artificial lateral line canal on each side is sufficient to determine the position of an upstream cylinder.
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Kármán vortex street detection by the lateral line.
Journal of comparative physiology. A Neuroethology sensory neural and behavioral physiology, 2007Co-Authors: Boris P. Chagnaud, Horst Bleckmann, Michael HofmannAbstract:Fish use the lateral line system for prey detection, predator avoidance, schooling behavior, intraspecific communication and spatial orientation. In addition the lateral line may be important for station holding and for the detection of the hydrodynamic trails (vortex streets) generated by swimming fish. We investigated the responses of anterior lateral line nerve fibers of goldfish, Carassius auratus, to unidirectional water flow (10 cm s−1) and to running water that contained a Karman vortex street. Compared to still water conditions, both unidirectional water flow and Karman vortex streets caused a similar increase in the discharge rate of anterior lateral line nerve fibers. If exposed to a Karman vortex street, the amplitude of spike train Frequency spectra increased at the vortex Shedding Frequency. This increase was especially pronounced if the fish intercepted the edge of a Karman vortex street. Our data show that the vortex Shedding Frequency can be retrieved from the responses of anterior lateral line nerve fibers.
Hiroshi Sakamoto - One of the best experts on this subject based on the ideXlab platform.
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the formation mechanism and Shedding Frequency of vortices from a sphere in uniform shear flow
Journal of Fluid Mechanics, 1995Co-Authors: Hiroshi Sakamoto, Hiroyuki HaniuAbstract:Experiments to investigate the formation mechanism and Frequency of vortex Shedding from a sphere in uniform shear flow were conducted in a water channel using flow visualization and velocity measurement. The Reynolds number, defined in terms of the sphere diameter and approach velocity at its centre, ranged from 200 to 3000. The shear parameter K, defined as the transverse velocity gradient of the shear flow non-dimensionalized by the above two parameters, was varied from 0 to 0.25. The critical Reynolds number beyond which vortex Shedding from the sphere occurred was found to be lower than that for uniform flow and decreased approximately linearly with increasing shear parameter. Also, the Strouhal number of the hairpin-shaped vortex loops became larger than that for uniform flow and increased as the shear parameter increased.The formation mechanism and the structure of vortex Shedding were examined on the basis of series of photographs and subsequent image processing using computer graphics. The range of Reynolds number in the present investigation, extending up to 3000, could be classified into three regions on the basis of this study, and it was observed that the wake configuration did not differ substantially from that for uniform flow. Also, unlike the detachment point of vortex loops in uniform flow, which was irregularly located along the circumference of the sphere, the detachment point in shear flow was always on the high-velocity side.
S V Prabhu - One of the best experts on this subject based on the ideXlab platform.
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Frequency detection in vortex flowmeter for low reynolds number using piezoelectric sensor and installation effects
Sensors and Actuators A-physical, 2012Co-Authors: A Venugopal, Amit Agrawal, S V PrabhuAbstract:Abstract Piezoelectric sensors are one of the most widely used sensors for vortex flowmeter application due to their low cost. Various researchers have employed piezoelectric sensor for this application. However, the location of the sensor and the performance of vortex flowmeter under disturbed conditions are seldom reported. In the present study, experimental investigations are conducted with water as the working medium in a circular pipe of diameter 52.5 mm. The optimum position of the piezoelectric sensor behind the trapezoidal bluff body is found out be 0.85 times the width of the bluff body. A new algorithm based on empirical mode decomposition and autocorrelation decay rate is suggested to identify the vortex Shedding Frequency under low Reynolds numbers flow condition. The performance of the flowmeter is also evaluated under different disturbed flow conditions to quantify the sensitivity of the flowmeter. The disturbances studied are single 90° bend, gate valve, globe valve, and two 90° out of plane bends. The overall uncertainty in the Strouhal number is within ±1.71%.