Hiroyuki Okuizumi

Tohoku University | Tohokudai

The rules governing the dimensions of the Javelin were substantially changed in 1986. It was considered that this new design guaranteed there was zero pitching moment at 0° angle of attack and that the pitching moment decreased (became negative) with increasing angle of attack. The objective of this study is to investigate if the pitching moment re...

To reduce optimization time spent on real-world expensive multi-objective optimization problems (MOPs), a relatively large number of points added in each cycle is an effective way to push the Pareto front approximation to the optimal Pareto front as more time-consuming experiments can be performed in a parallel manner. In this study, an enhanced mu...

To efficiently achieve tangible improvements in the aerodynamic objectives of a vehicle based on a computational fluid dynamics (CFD) simulation that produces unavoidable noise, an improved system is proposed. This system, called regression kriging with re-interpolation (RKri)-based efficient global optimization (EGO) with a pseudo expected improve...

The rules governing the dimensions of the Javelin were substantially changed in 1986. It was considered that this new design guaranteed there was zero pitching moment at 0° angle of attack and that the pitching moment decreased (became negative) with increasing angle of attack. The objective of this study is to investigate if the pitching moment re...

In this study, the influence of the position measurement method of a magnetic suspension and balance system (MSBS) for complex models such as a spaceplane was investigated, and a new position measurement method of MSBS for the spaceplane was developed. The new position measurement method can avoid complex shape parts such as wings by placing the se...

The Turbojav is a throwing implement designed for training junior athletes in javelin throwing. However, it apparently exhibits significantly different aerodynamic characteristics compared with a typical javelin. To elucidate the aerodynamic characteristics of the Turbojav, wind tunnel tests were conducted with a 1-m magnetic suspension and balance...

The conditions for the generation of negative Magnus force about a rotating sphere has not been clarified yet. Therefore, we developed a wind tunnel test method to investigate the negative Magnus force region using the 1-m magnetic suspension and balance system of the Institute of Fluid Science, Tohoku University, which can support a model in the w...

Using the world’s largest magnetic suspension and balance system (MSBS) and a low-turbulence wind tunnel, we successfully measured the aerodynamic forces acting on a non-spinning women’s javelin. It was found that the drag and the lift increased as the angle of attack was increased up to 18°. The pitching moment increased for angles of attack up to...

As accuracy of optimization can not be guaranteed without high-quality samples, the distribution of a finite number of evaluation points where experiments should be conducted in design space is an important issue, particularly when the experiment to obtain sample is expensive. To utilize limited number of evaluation points to represent the design s...

In order to consider the trajectory of the Turbojav, a wind tunnel test was performed using Magnetic Suspension and Balance System (MSBS), and the longitudinal three-component force was measured. The flight trajectory of the Turbojav was calculated from the measured aerodynamic force, and the throwing conditions were optimized using NSGA-II. It was...

Using the world’s largest 1-m MSBS (Magnetic Suspension and Balance System) and low-turbulence wind tunnel at Tohoku University, we successfully measured the aerodynamics force acting on a non-spinning women’s javelin with no supporting rod. The primary advantage of the MSBS is the complete elimination of any support, which can interference with th...

The aerodynamic coefficients of the turbo-jav (a short javelin for junior or disabled athletes) up to 26 degree angle of attack were obtained using Magnetic Suspension and Balance System (MSBS). Ordinary thin models are susceptible to interference caused by mechanical supports. However, MSBS can eliminate the support interference because the model...

The aerodynamics of the javelin is treated as a rigid body in spite of it flies with vibration in actual flight, and it seems there is no wind tunnel test result considered the effect of vibration. The objective of this study is to evaluate the effect of vibration for the aerodynamic force acting on the javelin using 1-m Magnetic Suspension and Bal...

The drag coefficients of freestream-aligned circular cylinders of fineness ratios of 0.75–2.0 were investigated with a magnetic suspension and balance system (MSBS). The objective was to find the critical geometry, that is, the fineness ratio at which the drag coefficient becomes the local maximum within this ratio range. The experiments were condu...

Support interference in wind tunnel testing is an unavoidable effect. It is difficult to measure the aerodynamic force acting on a model such as a ball owing to this effect [1]. A magnetic suspension and balance system (MSBS) suspends the model without any mechanical supports by using magnetic force, and at the same time, can measure the aerodynami...

In this study, we conducted experimental measurements and computational analysis to investigate the aerodynamics of a shuttlecock, especially the effects of the camber of the shuttle’s skirt. The static aerodynamic coefficient from the experiment showed that the camber of the skirt was able to modify the aerodynamic characteristics. A positive camb...

There are some reports that the Magnus force becomes negative at some situation in wind tunnel test. If so, there is possibility of a variety of curves using change of the direction of the Magnus force. PIV measurements of a flying table tennis ball were conducted to confirm whether a similar phenomenon was observed in real flight. A high-speed cam...

An experimental study and a computational study are conducted to understand the aerodynamics of the shuttlecock especially about the effect of the chamber of the blade. The lift, drag, pitching moment coefficient is measured in the experiment. It was found that the chamber of the blade can change the aerodynamic properties. The increase in camber c...

It is said that there are some differences between wind tunnel test and flight test on the ball aero dynamics. The reason of the difference seems to come from an acceleration and deceleration or unsteady motion at the flight test. In order to confirm the differences, PIV measurements around a flying table tennis ball are conducted. The high speed c...

It seems that there is a great difference between a wind tunnel test and a flight test about a region of the negative Magnus force. In order to confirm these differences, the flight experiments were conducted. At low spin condition, some strange trajectory that a ball rises to was occasionally observed. The trajectory obtained from the flight exper...

The negative Magnus force was observed on a sphere at the moderate Reynolds number and the moderate spin rate which is defined by the ratio of the circumferential velocity to the free stream velocity. This region matches the forehand smash in a table tennis game according to the result of Taneda's experiments. To confirm the possibility of the exis...