Swimming motion of a bacterial cell in an infinite liquid was numerically analyzed. The relation between the cell size, the flagellar rotational rate and its swimming speed was calculated. The calculated values are comparable to observed values. Near a surface, the motion becomes different from the motion unaffected by any surfaces. The rotations of the flagella and the cell body cause a circular motion. According to our numerical results, the pitch angle varies during the circular motion, and it becomes zero at a certain distance from the surface. This suggests that cells will accumulate within a range of distance.
Wing of bird is composed of lots of feathers and thus shows conspicuous difference from the wing of conventional airplane. In this study, the function of primary feather of bird wing is focused on and the wind tunnel test was conducted by using models of assembled wing with several primary feathers. The result shows that the existence of gap between primary feathers reduced the lift and lift-to-drag ratio. It also reduced the bending moment made by the primary feathers at the tip of the wing, thus indicating the benefit of assembled wing to augment the tolerance of wing to the destruction due to the strong bending moment under turbulent condition.
In this paper we propose new image features named radial intensity profiles (RIP) for high-speed autofocusing of cells based on our Depth From Diffraction (DFDi) method. DFDi is a method of extracting depth information of target cells from a single defocused image containing their diffraction patterns. High-speed focusing of separated yeast cells with 20 ms response time and continuous autofocusing with a scanning microscope were demonstrated. The successful continuous autofocusing shows that image-based high-throughput measurement of cells could be realized using the proposed algorithm.
We consider the effects of chordwise flexibility on the aerodynamic performance of flapping wings using numerical simulation. The two-dimensional Navier-Stokes equations are solved using a Fourier pseudo-spectral method with no-slip boundary conditions imposed by the volume penalization method. The flexible wing is modelled with a non-linear beam equation. Our numerical simulations of heaving plates show that the maximum thrust is achieved at a stroke frequency lower than resonant, which is in agreement with experiments. The oscillatory part of the force only increases in amplitude when the frequency increases. We also consider aerodynamic interactions between two heaving foils.
We carried out experiments to measure velocities within turbulent water flow over wavy plates fixed to the bottom of an open channel. We also have measured total drag acting on these plates. Wall-shear stress is evaluated from the gradient of mean velocity adjacent to the plate surface. The pressure drag is calculated from the difference between the total drag and friction drag. Results show that the friction drag for a symmetrical-wavy plate is 21% lower than that for a flat plate. The former, furthermore, offers benefits in reducing pressure-drag increases.
This study is to develop prosthetic flippers for an injured sea turtle named “Yu” from the view-point of 3D (three-dimensional) hydrodynamic analysis of sea turtles’ forelimb propulsion. Firstly template matching method is used to compare the 3D movements of fore flippers in three cases respectively: those of a healthy turtle, those of Yu with and without prosthetic flippers. Secondly 3D hydrodynamic analyses for three cases based on quasi-steady wing element theory are carried out to investigate the hydrodynamic effects of prosthetic flippers on the swimming performance of sea turtles. Finally the hydrodynamic effects are clarified and some remarks for designing new prosthetic flippers in future are given.
This paper describes a non-tethered flapping robot with resonant-driven wings. We proposed a wing with a thin plate that can be resonated at a low frequency using a small battery mounted on the robot. The thrust force generated by the proposed wings at their resonant frequency was 35 percent larger than that of non-resonant wings. Moreover, the non-tethered robot with four wings was developed for free flight. The phase difference between fore and hind wings was varied from 0 to 180 degrees. The robot with the phase difference of 0 and 90 degrees successfully made a level flight.
The simulation method for synchronized swimming was developed by extending the swimming human simulation model ‘SWUM.’ In order to acquire the input data for the simulation, an experiment using subject swimmers was carried out. Using the acquired input data, the simulation reproducing the experiment was conducted. The simulated results were compared with the experimental ones and the sufficient validity of the simulation method was confirmed. In addition, parameter studies about timing of motion among the swimmers were conducted. It was found that the jumping height became maximum (0.7m larger than original) when the upper swimmer's motion was 0.07s earlier.
The speed-up of robotic fish is hoped to aim at practical use. It is therefore important to develop methods for making such robots swim faster, and computer simulations are invaluable. In this study, a computational simulation model was developed for three-dimensional fluid-structure interaction analysis. The flow around the caudal fin can be analyzed by treating the fin as an elastic body. Experiments were also carried out and good agreement was found between the experimental results and those of the numerical analysis. Moreover, the effects of the flexibility of caudal fin on the robot's propulsive performance were investigated using computational simulations.
An experimental study is presented outlining the mechanical aspects of biological locomotion in beach fleas. Two basic types of dynamic behavior of beach fleas were examined, and their locomotive organs were observed microscopically. The jumping and swimming of beach fleas were analyzed by the high-speed video camera system. The structural properties of swimming and leaping organs were also studied. In the experiment for the jumping analysis, the relation between the surface roughness of ground and the horizontal jump distance were examined. Mechanical aspects in the relation between locomotive organs and behavior of beach flea were considered.
In this study, the motion of a squid-like underwater robot with two undulating side fins has been investigated through towing tank experiment and simulation of 6-DOF mathematical model in 3D space with the aim of developing a real time simulator. The comparison between simulation results and experimental results confirmed the accuracy of the simulation. The real time handling simulator was developed based on the mathematical model by using Open Dynamic Engine (ODE). It was confirmed that the robot in this simulator can move in the similar way as real robot’s motion by the same control.
Swimming motion of single celled dinoflagellates, Symbiodinium sp, was calculated by using the boundary element method, In the calculation, the propagating helical wave of the transverse flagellum with a membrane is considered. For the thrust rate, the numerical result well agrees with the observation. In our model, the cell body is assumed to rotate to the opposite direction of the wave propagation to balance the total torque. The cell rotation was observed from two directions to compare with the above obtained numerical result. The rotational direction is opposite to that in the prediction.
This paper describes jumping behaviour of the globular springtails. Direct observations on the jumping and climbing behaviour of springtails were conducted in the laboratory. The kinematics of jumping in tiny springtails was analyzed with high-speed video camera system. The vertical climbing behaviour was analyzed in contrast to the jumping behaviour. The jumping performance of springtails was revealed.
This paper is concerned with a small jumping mechanism. Microscopic observations of springtail leaping organs were conducted using a confocal leaser scanning microscope. A simple springtail mechanism using a spring and small electromagnet was produced based on the observations of leaping organ and the jumping analysis of the globular springtail. Jumping characteristics of the mechanism were examined with high-speed video camera system.
A mechanism to generate asymmetry wing flapping amplitude for the flapping-type Micro Air Vehicle (MAV) system was proposed in this paper. The mechanism concept was inspired from the flapping motion of an insect: Diptera. The insects conduct the asymmetric wing flapping amplitude to generate rotational torque to control flight orientation without using a tail rudder. The mechanism using Bio-Metal Fiber actuator was developed and evaluated experimentally.
Sharp Corporation has been developing high-performance electric fans by applying the characteristics of wings of living creatures. This paper describes an electric fan having a propeller that mimics the shape of the wings of a Chestnut Tiger butterfly. Most electric fans generate a nonuniformly distributed wind velocity, which cause an uncomfortable feeling for the user. If the number of fan blades was increased, the wind generated would be smoother; however, the efficiency of the propeller itself would decrease. To solve these problems, we have modeled prototype electric fan propeller blades based on the shape of a Chestnut Tiger butterfly wing.
In this study, the swimming humanoid robot SWUMANOID for research of human swimming was developed. It was half the size of a real human and had the same body proportions and appearance; mass distribution was considered, as well. It was actuated by 20 motors, which were waterproofed and compactly designed. Swimming motions were determined based on human swimming movements. To realize the swimming arm stroke, a joint imitating the human's scapular retraction was installed and the methodology to realize the swimming motion with that joint was established. Finally, the efficiency of the design was validated by simulation and representatively, the crawl stroke was successfully realized in the water tank.
The objective of this study was to realize the free swimming of the crawl stroke with the previously developed swimming humanoid robot. The upper body of the robot was remodeled to fit a free swimming test. The developed robot was simulated to raise feasibility of the crawl stroke. Through the simulation, two improved models were proposed. In the experiment, the swimming humanoid robot was fitted to the two simulation models and both realized the crawl stroke successfully. The measured roll angle was about ± 60 degrees and the swimming speed was between 0.2 m/s and 0.24 m/s.
To examine swarm formation, we developed a system comprising a set of robots, a position acquisition system, a visible light communication device, and a PC to obtain the position and orientation of the respective robot and to determine their motion. Using it, experiments were conducted on the ground and underwater. Results of the experiments show that the system can make the robots form a predefined formation on the ground. They can move two underwater robots to target points. Results show that the system is useful to develop and to verify swarm algorithms in a realistic situation, not merely in a computer simulation.