Due to the great Tohoku earthquake on 11 March 2011, the dispersion of radioactive materials from the Fukushima Daiichi nuclear power plant induced serious environmental pollution centered in the eastern part of Fukushima Prefecture. Considering that nuclear power plants in Japan locate over and/or near complex terrains, it is critical to understand local-scale wind systems over such complex terrains. This study investigates the characteristics of local-scale wind fields in complex terrain by conducting high-resolution meteorological simulations that represent small-scale terrain features for the case in the eastern area of Fukushima in March 2011. The analyses are conducted for the relationship between the complex terrain and the boundary-layer winds. The effects of the complex terrain can be found for winds at the level of at least 200-m height above ground level for the terrain examined here.

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An atmospheric general circulation model (AGCM) for Venus is being developed on the basis of AFES (AGCM For the Earth Simulator) in order to study atmospheric phenomena of Venus by the numerical simulation with high resolution. Super-rotation is assumed to exist at initial state and to be maintained by the relaxation forcing due to the meridional temperature gradient. In the time evolution of this setting, baroclinic modes grow in the cloud layer with small static stability. The structures of unstable modes are similar to those obtained in the linear stability analysis initially, but changed by the nonlinear interactions in the later stage. Meridional transport of momentum and heat by these unstable modes is discussed.

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Reynolds number (Re) dependency on the state of the oceanic double-gyre is investigated using a quasi-geostrophic model under constant forcing. The results are classified by energy level and length of the strong eastward jet. Both the energy levels and the lengths of the jet increase with an increase in Re until Re = 209, but begin to decrease at Re = 314. For Re = 209, intense eddy shedding occurs from the easternmost tip of the jet. For Re = 314, the jet is collapsed and eddy shedding occurs not only from the easternmost tip of the jet but also in the path of the jet. The realistic phenomena are considered to correspond to the results for Re = 314 in this study. The dominant instability in the long-term variability of the oceanic double-gyre seems to be different from the instability of the G-mode suggested by Simonnet and is related to shear instability.

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The present study focuses on the recent update of the global ocean data assimilation system in the Meteorological Research Institute (MRI). The model domain of the system is extended to cover the Arctic Ocean with advanced physical processes incorporated (e.g., sea ice). Compared with data-free simulation, data assimilation improves reproduction of the circulation field in the Arctic Ocean, as well as temperature and salinity which are directly modified by data insertion. The system also effectively reproduces the observed sea-ice field. In addition to extending the domain, we have sophisticated statistical information in the global ocean for data assimilation, including coupled temperature-salinity empirical orthogonal function modes in a background error covariance matrix, by incorporating new observational datasets. This improves variability, especially in the salinity field in the tropical Pacific and Indian Oceans, even during the period before the recent increase of salinity observations. The updated system effectively reproduces the oceanic structure associated with the 1997-1998 El Niño. These results will likely contribute to more accurate seasonal predictions using a coupled atmosphere-ocean model.

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We have numerically studied the dynamics of spring-loaded cylinders in a uniform flow at low Reynolds number (Re = 400). For a single cylinder, two different types of oscillation are ob- served for the characteristic frequency of the cylinder due to the interaction between the cylinder and the vortices generated in the downstream flow. When two cylinders are in a side-by-side arrangement in uniform flow, the synchronization of the two cylinders was observed even if the natural frequencies of the cylinders are different. The synchronization region was determined based on the distances of cylinder centers and the frequency differences between the cylinders. A phase equation has been derived from numerical data to describe the synchronization behavior.

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Engineering relations for fire plumes are widely used for an architectural design of onshore buildings and plants. In the offshore environment, however, fire plume features are considerably different from those in a compartment of onshore facilities because the fire source location changes with time due to the influence of complex ship motions. Thus, in this study large eddy simulation of a turbulent buoyant plume above an oscillating fire source has been carried out to clarify the fire plume features in the offshore environment. As a preliminary step, unsteady fire source movement associated with complex ship motion is simplified to simple harmonic oscillation in the horizontal direction. The numerical results are compared with conventional relations for fire plumes above a stationary source with ideal geometry. Consequently, it has been found that qualitative properties of the present buoyant plume are mainly composed of well-recognized features of the two-dimensional and axisymmetric plumes.

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In Japan Aerospace Exploration Agency (JAXA), work is presently underway for the complementary use of Experimental Fluid Dynamics (EFD) and Computational Fluid Dynamics (CFD). The main purpose is to improve the utility of both EFD and CFD and the data assimilation technique is expected to be a promising approach. In this study, a coupled system of high-speed CFD solver (FaSTAR) and measurement- integrated- simulation (MIS) algorithm is constructed, and an identical twin experiment of flow field around a 2-dimensional airfoil with difference boundary condition is performed.

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This paper presents a numerical solution to multi-objective shape optimization problems of steady-state viscous flow fields. In this study, a multi-objective shape optimization problem using a normalized objective functional is formulated for drag minimization and lift maximization of an isolated body located in viscous uniform flow. In addition, another multi-objective shape optimization problem is formulated for lift maximization while the drag is set to a desired constant value. The shape gradients for these shape optimization problems are derived theoretically using the Lagrange multiplier method, adjoint variable method, and the formulae of the material derivative. Reshaping is performed using the traction method, which has been proposed as an approach to solving shape optimization problems. The validity of the proposed method is confirmed by the results of 2D low Reynolds number viscous flow problems.

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A numerical simulation is performed on the acoustic scattering from a circular vortex. Perturbed linearized compressible Euler equations for the perfect gas is used as the governing equations. A symplectic integration method and the compact finite difference schemes are applied to these equations. Two model flows are considered to approximate isolated circular vortex. They are the Rankine vortex and the Burgers vortex. In the case radial velocity distribution is modeled by a Rankine vortex, overall agreement of the pressure field computed by the present study and the previous studies is good. Acoustic wave interference patterns for the case of the Burgers vortex is compared with the case velocity profile is modeled by the Rankine vortex.

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A feedback control of flow separation on the NACA0024 airfoil has been investigated by using dielectric barrier discharge (DBD) plasma actuators and fiber Bragg grating (FBG) flow sensors. Tangential jets are generated from the DBD plasma actuator at the leading edge of the airfoil. The FBG flow sensor put near the root of a cantilever beam detects the vibrations of the cantilever tip by wake flow around the trailing edge and flow separation is adjudicated by the standard deviation of Bragg wavelength (λ_B'). A demonstration of flow separation control was conducted successfully under periodic flow separation by a feedback algorithm using a threshold level of λ_B' = 0.006 at Re = 5.3×10⁴ and showed that the flow separation can be mitigated by about 20% in this strategy.

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In this research, effects of Gurney flaps were investigated for aerodynamic characteristics of NACA4412 airfoil by wind-tunnel experiments. The Gurney flaps with height of 0 to 6% of the chord length were attached at the trailing edge. Under flow condition of Reynolds number 6.5×10⁵, experimental setup was three-dimensional (3D) or quasi two-dimensional (2D), according to flow fields without or with side plates. The higher the Gurney flaps are, the more both maximum lifts and stall angles increase: in 2D cases maximum lifts become higher but stall angles hardly change, while in 3D cases stall angles become remarkably higher than in 2D cases. Each family of polar curves for 2D or 3D measurements constitutes a curve like an envelope. By use of each “envelope”, when the necessary value of lift is given, combination of an attack angle and a flap height with the lowest value of drag can be obtained.

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In this study, the motions and distributions of microbubbles in Taylor—Couette vortices were simultaneously measured by using an imaging approach. To obtain the velocity of microbubbles and the velocity distribution of the liquid phase, particle tracking velocimetry (PTV) adopting laser induced fluorescence (LIF) technique were employed by a single color-imaging video camera. This setup enabled us to distinguish tracer particles from microbubbles in captured images. The modifications in the waviness of Taylor vortices, enhancement of the basic wave and reduction of the modulation wave, are consistent with a recent study (Watamura et al., 2010). Further, the simultaneous measurements of velocity field and microbubble motions show a preferential distribution and organized ascending motion of the microbubbles in the wavy vortical structure of Taylor—Couette flows.

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A novel static-implicit finite element formulation based on the incremental equilibrium equation (IEE), which has been recently developed in the meshfree method, for the large deformation analysis is proposed. As the IEE is a semi-empirical equation without any mathematical derivation so far, a mathematical derivation of the IEE from the virtual work equation in rate form is presented. The proposed static-implicit FE formulation is precisely described, and the prospective advantage of our method combined with rezoning technique is clarified. A few examples of the large deformation analysis are presented to show that the proposed formulation has enough accuracy comparable to the standard formulation.

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It is required to maintain the durability of concrete structures from the viewpoint of the proper control of maintenance. Thus, it is necessary to evaluate the soundness of the structures. The ultrasonic method which is one of nondestructive tests is tried to use as an evaluation method. In the case of the object of which density is high and its distribution is homogeneous, the ultrasonic can detect defects correctly. However, a concrete is inhomogeneous, and the wave spreads intricately if it comes to a crack or a discontinuous portion. Therefore, the limit and usefulness of applicability of the ultrasonic method are indefinite. In order to apply the ultrasonic method to concrete structures, it is necessary to grasp the influence of the properties of the concrete on the propagation of the wave. In this study, numerical analyses are conducted with considering the inhomogeneous of the concrete to check the applicability of the ultrasonic to the concrete.

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This study numerically and experimentally investigated the effect of a single solid particle on the interaction between water and an elastic tube due to a water hammer. The investigation was conducted by impacting a steel cylinder projectile (at a speed of 2.4 m/s) onto the surface of a water–filled polycarbonate tube to initiate the water hammer propagating through both the tube and water. We examined the effect of a single cylindrical particle on the impact tube response for different particle radii and materials (steel, aluminum, and polycarbonate). Computational and experimental strains observed in front of the particle were in good agreement; the radial tube displacement was higher when the particle was made of stiffer material. In the experiment, the tube response in the middle of the particle was strongly affected by the size of the particle rather than the particle’s material. To evaluate the maximum impact response of hoop strains around the particle, a new model was proposed that treats the particle as a rigid body, and it successfully captured the experimental tendencies.

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Much attempt was made to improve PEFC performance to optimize its operating condition and its structure by experimental and numerical trials. One of the most critical issues about PEFC improvement is the durability enhancement at its membrane electrode assembly (MEA) to keep its robust control. The objective of this study is to keep the optimal water distribution at MEA with applying the hydrophilic anode support. In this study, the influence of modification to use two hydrophilic support materials is calculated by the case of weak hydrophilized carbon support and strong hydrophilic SnO₂ support. The distribution of liquid water shows that hydrophilic anode support has the effect to hold the liquid water in anode catalyst layer under the low humidification, and water saturation ratio in cathode catalyst layer is also controlled by the use of hydrophilic materials. Hydrophilic anode support works as a water transport pathway to anode across polymer electrolyte membrane. Its effect also prevents from drying-up of the anode and flooding of the cathode.

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This paper describes an analysis of high frequency electromagnetic fields using the finite element method of Maxwell equations including the displacement current. To solve a large-scale complex symmetric problem on a parallel computer efficiently, a domain decomposition method based on a COCR method is proposed. The COCR method improved convergence behavior in solving an interface system as compared to the COCG method, and then significantly reduced the computation time for the large-scale problems.

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We present a simple numerical simulation on local solutions of partial differential equations. It is enabled by using IPNS(Infinite-Precision Numerical Simulation). The equation solved here is the Laplace equation. The behaviors of numerical solutions are different corresponding to the existence or nonexistence of the solution. The numerical method used here is not restricted to the Laplace equation. So, our results may be useful for the theoretical proof on the existence or nonexistence of the solution of partial differential equations.

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It is shown that an equation derived by Van Gorder (2012) denoting a motion of a locally induced vortex filament in a coordinate representation can be transformed directly into an equation described in Umeki (2010) for a temporal evolution of a complex variable denoting a tangential vector of the filament. Analytical and numerical solutions using the equation in a coordinate representation are shown for some examples. A first-order exponential integrator for the Serret-Frenet formula is derived, which is useful when an information of the curvature and the torsion is available for computation of the shape of the filament.

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We consider a mathematical structure of the mean field equation for vortex filament systems. The vortex filament systems composed of nearly parallel vortex filaments can be regarded as a three-dimensional extension of the point vortex systems introduced by Onsager to investigate the 2D turbulence. We reveal that the vortex filament systems are equipped with a dual variational structure as in the case of the point vortex systems, and that two expressions of the mean field equation for the system in terms of the stream function and the vorticity are derived from a Lagrangian. In addition, we discuss the existence of solutions to the mean field equations.

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In this paper we investigate the Euler-Maruyama approximation of the reflecting Ornstein-Uhlenbeck process using the penalty method and estimate the speed of convergence in L^p sense. We also consider a numerical simulation of the refiecting Ornstein-Uhlenbeck processes with one and two dimensional domains, respectively.

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Wavefront aberration measurement is important to evaluate the performance of the imaging lens. In this research, a novel mathematical model of the spot image for the aberration retrieval method from the spot images has been developed. Firstly, we explain the development of the expression for the proposed mathematical model of the spot image. The proposed model is expressed with the coordinate transform on the exit pupil plane and the Fourier transform. Secondly, we explain the aberration retrieval method from the spot images using the proposed mathematical model. Finally, we show two types of the numerical verification experiments. From the numerical experiments, the spot images calculated by the conventional model and the proposed model are compared. Also it is confirmed that the aberration retrieval method from the spot images using the proposed model is stable, and this aberration retrieval method is highly accurate and precise.

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Recently, genome wide association studies (GWAS) have been one of the important approaches to identify loci associated with common diseases. GWAS have discovered many disease-associated loci in autosomes which do not determine the gender. For some of diseases, however, their prevalence rates are different between males and females. Hence, to estimate statistical powers for association tests, we need to consider the difference in the case of combined genotyping data of both genders. In this paper, we propose a new method to calculate the power of genetic association test for diseases whose prevalence rates are different between genders using Bayesian methods.

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