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The effects of grid-generated turbulence on a turbulent boundary layer are investigated by means of a direct numerical simulation (DNS). A square turbulence-generating grid, on which the velocity components are set to zero, is numerially constructed near the entrance to a rectangular parallelepiped domain. The nonslip condition is applied to the lower boundary to develop a turbulent boundary layer downstream of the turbulence-generating grid. The fractional step method is used to solve the governing equations. The results show that streamwise and vertical turbulence intensities and Reynolds stress normalized by the inner parameters are suppressed in the log-law region by the grid turbulence.

Integration of modern medicine and CAM (complementary and alternative medicine) has been drawn our attention for the expectation of the development of a new medical technology. The pulse diagnosis in traditional Chinese medicine is one of the well-known CAM. The doctor diagnoses not only illness but also decline of health of the patient from the sense of the pulse wave of the radial artery. However, this technique does not have concrete scientific evidence. Therefore, in this paper, a simple mathematical model of the circulatory system of an arm and the tissue surrounding the radial artery was presented to reproduce the pulse wave measurement during the pulse diagnosis. Experiment was first performed to obtain the pressure wave form as the standard by pressing down a pressure sensor against the radial artery. Numerical simulation was performed for the same condition as experiment. By comparing the measurement and computational results, mechanical property of the tissue model and tube law of the artery can be determined from the mean pressure variation, and viscous resistance of the artery can be determined from the amplitude of the pressure oscillation.

Cardiovascular diseases are closely related to blood flow. Ultrasonic-Measurement-Integrated (UMI) simulation, in which results of ultrasonic measurement are fed back to the flow simulation, was proposed in a previous study in order to reproduce the real blood flow accurately and efficiently. The usability of the UMI simulation was confirmed by numerical experiment, but the effectiveness of this simulation was strongly affected by the accuracy of the ultrasonic measurement. In this paper, we examined the accuracy of a commercial ultrasonic measurement device by an experiment with a PVA-H straight tube phantom. By analyzing the measured color Doppler images for a developed laminar flow inside the phantom, we obtained the relationship between the color Doppler value and the Doppler velocity (C-V relationship). It was revealed that the original C-V relationship provided in the device as a color bar was not suitable for quantitative evaluation of Doppler velocity to be used in UMI simulation. Compared with the original C-V relationship, the present C-V relationship results are in far better agreement with the analytic solution. Investigation of the normalized error confirmed that the result obtained with the present C-V relationship was reliable in cases of relatively high Reynolds number in the flow domain except near the wall. The two signal conditioning factors of the device had little influence on the Doppler velocity. Finally, we investigated the effect of temporal and spatial averaging of ultrasonic measurement data to clarify the relation between the number of averagings and the level of agreement with the analytic solution.

This paper deals with measurement-integrated (MI) simulation, which is based on the observer in dynamical system theory to obtain the exact and detailed information of real flows. In this study, we propose the MI simulation coupled with Particle Image Velocimetry (PIV) for a flow with the Karman vortex street behind a square cylinder at Reynolds number of 1200 based on the cylinder width. The validity of the PIV-MI simulation is first examined in two-dimensional numerical experiment. The effect of feedback data rate is investigated by changing the feedback frequency and the feedback area. Then effectiveness of the PIV-MI simulation is validated in experiment. As a result, the PIV-MI simulation with full feedback shows good agreement with the standard solution for both the mean velocity and the velocity fluctuation. From the viewpoint of the reduced feedback data rate, spatially limited feedback shows better results than temporarily limited feedback. It is also confirmed that the information around the cylinder is important to reproduce the wake behind the cylinder. In the result of the experimental validation, the PIV-MI simulation reproduces the experimentally obtained flow field, showing the same effect of the feedback in accordance with the numerical experiment.

In the previous study, it was clarified in the right-angle branch with single side branch that the velocity periodically oscillates in the side branch, and the Strouhal number is independent of cross-sectional area ratio, the flow division ratio of side branch to main branch, and the Reynolds number. In the present study, the flow structure in the right-angle branch with double side branch has been experimentally studied in laminar steady flow using laser Doppler anemometry and particle image velocimetry. Consequently, the velocity also oscillates periodically in both side branches, and the Strouhal number is independent of the Reynolds number although the Strouhal number in the downstream side branch is a little larger than that in the upstream side branch. It has been clarified that the flow oscillation in the right-angle branch is a characteristic phenomenon caused from its geometry and the factor inducing oscillation would be high shear rate.

An experimental study of the aerodynamic characteristics of 3-dimensional flapping wing in hovering flight is conducted. Lift and power are measured in water on a scaled flapping wing of bumblebee. Two types of flapping motion are employed. One is a trapezoidal type of flapping motion which consists of translational, reversal and rotational phases; the other is a sinusoidal type of flapping motion, in which a wing is rotating continuously. The results show that the trapezoidal type has higher efficiency than the sinusoidal type. The shorter rotational phase enhances a fluid force normal to the wing surface. However, the rotational phase during the flapping translational phase contributes the increase of power rather than that of lift. This is because the enhanced fluid force vector due to the rotational phase is directed to the stroke plane, which requires more flapping power. In order to attain higher efficiency in hovering flight, the rotational phase should be done during the reversal phase rather than the flapping translational phase.

In vitro blood vessel biomodeling with realistic mechanical properties and geometrical structures is helpful for training in surgical procedures, especial those used in endovascular treatment. Poly (vinyl alcohol) hydrogel (PVA-H), which is made of Poly (vinyl alcohol) (PVA) and water, may be useful as a material for blood vessel biomodeling due to its low surface friction resistance and good transparency. In order to simulate the mechanical properties of blood vessels, measurements of mechanical properties of PVA-H were carried out with a dynamic mechanical analyzer, and the storage modulus (G’) and loss modulus (G”) of PVA-H were obtained. PVA-Hs were prepared by the low-temperature crystallization method. They were made of PVA with various concentrations (C) and degrees of polymerization (DP), and made by blending two kinds of PVA having different DP or saponification values (SV). The G’ and G” of PVA-H increased, as the C or DP of PVA increased, or as the proportion of PVA with higher DP or SV increased. These results indicate that it is possible to obtain PVA-H with desirable dynamic viscoelasticity. Furthermore, it is suggested that PVA-H is stable in the temperature range of 0°C to 40°C, indicating that biomodeling made of PVA-H should be available at 37°C, the physiological temperature. The dynamic viscoelasticity of PVA-H obtained was similar to that of the dog blood vessel measured in previous reports. In conclusion, PVA-H is suggested to be useful as a material of blood vessel biomodeling.

An experimental study of the aerodynamic characteristics of 3-dimensional flapping wing in hovering flight is conducted in the wide range of parameters, which are Reynolds number, reduced frequency and wing planforms. Lift and power are measured on scaled flapping wings, which mimic bumblebee and cicada wings, and which are delta wings with different locations of maximum chord.The results show that lift and power (1) are almost unchanged in Re=800-5000, (2) increase as the reduced frequency increases, although the effeciency is constant, and (3) increase as the location of maximum chord moves from wing base to tip, although the effeciency decreases.

In the previous study, it has been clarified in the right-angle branch that the periodical oscillation flow is induced in the side branch and the Strouhal number based on the variables in the side branch is independent of the Reynolds number, the flow division ratio, and the radius of the side branch. This periodical oscillation appears along the boundary between two pairs of vortices with the opposite rotation at the cross section of the side branch across the separation flow. In the present study, another source of the periodical oscillation is experimentally clarified that the high shear rate flow is induced along the separation shearing layer between the separation flow of low velocity and the main flow with high velocity along the distal wall in the side branch since the high shear rate along this separation shearing layer is several times as large as that in the upstream trunk or in the downstream region of the side branch.

The present paper deals with a fundamental study of aerodynamic drag reduction for a vehicle with a feedback flow control. As the first step, two-dimensional calculation was performed for a flow around a simplified vehicle model. The mechanism of unsteady drag was investigated in relation to the vortex shedding from the model. The location of the control flow nozzle was so determined that the control flow influences the drag most effectively. The key in designing the present feedback control is the definition of the output signal. Based on the physical consideration of the drag generation, the location of the output velocity measurement was changed within a limited region near the front windshield. A systematic calculation revealed that the output signal defined in a small region results in a significant drag reduction of 20% with respect to the case without control. The present feedback flow control is generally applicable to the drag reduction of the bluff body for which the drag is generated under the same mechanism of essentially two-dimensional vortex shedding.

This paper deals with a new flow analysis system, namely the hybrid wind tunnel ,w hich integrates the experimental measurement with a wind tunnel and a corresponding numerical simulation with a computer. Analysis here is performed for the fundamental flow with the Karman vortex street in a wake of a square cylinder. A specific feature of the hybrid wind tunnel is existence of the feedback signal to compensate the error in the pressure on the side walls of the cylinder and the feed-forward signal to adjust the upstream velocity boundary condition. Investigation is focused on evaluating the hybrid wind tunnel as a flow analysis methodology with respect to the ordinary simulation and the experiment. As compared with the ordinary simulation, the hybrid wind tunnel substantially improves the accuracy and the efficiency in the analysis of the flow. Especially, the oscillation of the flow due to the Karman vortex street reproduced with the hybrid wind tunnel exactly synchronizes with that of the experiment, while that with the ordinary simulation never behave like that. In comparison with the experiment, the hybrid wind tunnel provides more detailed information of the flow than the experiment does.

Neutrophils must flow through the pulmonary capillary network in a deformed shape because pulmonary capillaries are closely interconnected, and deformed neutrophils take about 15 s to 1 min to return to their resting spherical shape. In this paper, flow of a neutrophil through two moderate constrictions in a pipeline is numerically investigated, focusing on the effect of cell deformation on the cell's transit time through the constrictions. Changing sizes and positions of the constrictions, we found that the maximum cell radius at the entrance of the constriction and the throat radius of the constriction are the dominant factors in predicting the cell's transit time through the constriction. When the difference between these two radii is relatively large, steeper constriction (smaller radius of curvature) increases the transit time, but this tendency is reversed when the difference is small. Cells traverse the constriction without delay when the maximum cell radius and throat radius are comparable. Finally, we present a simple mathematical model for the transit time.

In this study, numerical simulation was performed with the SIMPLER method on the amplification of Tollmien-Schlichting (T-S) wave in the boundary layer over a flat plate and its suppression with a wall motion actuator. The T-S wave was induced by the interaction between sound wave introduced by a speaker and a protuberance on the surface of the plate, and amplified in the unstable region of the boundary layer. The vertical vibration of a wall motion actuator was used to control the T-S wave. The influence of the amplitude and phase of actuator vibration on the control effectiveness was investigated in the simulation. The results show that the T-S wave can be effectively suppressed by the motion of the actuator surface if the phase and amplitude of the actuator are appropriately adjusted.

The former analysis of neutrophil's transit through pulmonary capillary network used the result of a micropipette aspiration experiment to model the transit in single capillary segment despite blunt tip geometry of the pipette is largely different from the real capillary segment. In the previous work, we have numerically investigated the transit of passive and fMLP-stimulated neutrophils through an arc-shaped constriction, establishing the analytical expression for the transit time. This paper intends to give a simplified model for the transit of a neutrophil through a capillary segment based on the numerical analysis and the stress strain relationship of a Maxwell material. It is shown that the transit time is in proportion to the viscosity of the cell and in inverse proportion to the square root of the curvature radius of the constriction. The definition of the driving pressure of the cell into a micropipette is also applicable to that into the constriction.