Manabu Hishida

Toward the Fastest Unstructured CFD Code "FaSTAR"

Along with the system development of “Digital/Analog-Hybrid Wind Tunnel” at JAXA, a fast CFD code is required. Based on the investigation of well-known unstructured CFD codes, we have determined the target performance and specification of CFD code. This is then followed by the development of a fast unstructured CFD code “FaSTAR”. The accuracy of drag prediction with FaSTAR is validated by the DPW4 benchmark problem. The computed drag coefficients generally agree with other results. Since we employ the Cartesian-based unstructured grid generated with HexaGrid, the predicted drag is affected by the choice of discretization method, whether it is cell-center or cell-vertex. Moreover, the reconstruction method is found to be important. This affects the drag prediction accuracy and the smoothness of surface pressure distribution. The computational speed of present CFD code is 1.8 hour/case with 10 million grid and 100 cores for a standard civil aircraft. The multigrid method with the global coarse grid shows four times faster convergence than that with the zonal coarse grid. Here, the coarse grids are generated utilizing the octree data of Cartesian grid.

FLOW AND OPTICAL FIELDS IN A SUPERSONIC FLOW CHEMICAL OXYGEN-IODINE LASER

The flow and optical fields of a supersonic, flow chemical oxygen-iodine lasers are simulated by solving the three-dimensional Navier-Stokes equations and the paraxial wave equation, and the laser power extraction characteristics are studied. The effects of the wall catalysis are also discussed by introducing the surface catalytic efficiency into the wall boundary condition. The numerical results show that the pair of contrarotating vortices behind the curved jet greatly enhance the mixing and the simultaneous chemical reaction. The effect of the residual flow non-uniformity on the output laser beam is small due to the low Mach number and the fairly good mixing. The wall catalysis reduces the laser performance in case a plenty of excited species diffuse toward the wall of nozzle blades.

The Japanese Histologic Classification and T-score in the Oxford Classification system could predict renal outcome in Japanese IgA nephropathy patients

BackgroundThe Oxford Classification is utilized globally, but has not been fully validated. In this study, we conducted a comparative analysis between the Oxford Classification and Japanese Histologic Classification (JHC) to predict renal outcome in Japanese patients with IgA nephropathy (IgAN).MethodsA retrospective cohort study including 86 adult IgAN patients was conducted. The Oxford Classification and the JHC were evaluated by 7 independent specialists. The JHC, MEST score in the Oxford Classification, and crescents were analyzed in association with renal outcome, defined as a 50% increase in serum creatinine.ResultsIn multivariate analysis without the JHC, only the T score was significantly associated with renal outcome. While, a significant association was revealed only in the JHC on multivariate analysis with JHC.ConclusionsThe JHC and T score in the Oxford Classification were associated with renal outcome among Japanese patients with IgAN. Superiority of the JHC as a predictive index should be validated with larger study population and cohort studies in different ethnicities.

A Multi-Cycle CFD Analysis of Oxyhydrogen Pulse Detonation Engine

In order to discuss the feasibility of pulse detonation engine (PDE) cycle under specific configurations and conditions, a two-dimensional reactive flowfield during the PDE multicycles is numerically studied for Ar-diluted hydrogen-oxygen mixtures. A simplified twostep chemical reaction model with a high-resolution numerical scheme is introduced to simulate a practical-size PDE configuration. The results show that, in the refilling process, a high-pressure/high-temperature region is formed near the injection ports, resulting in an undesirable self-ignition of fresh gas mixture. Thus we propose a new injection technique “ignition-preventor” to avoid the self-ignition and discuss its validity and influence on the successive re-initiation process of detonation.

Seasonal proteinuria changes in IgA nephropathy patients after proteinuria remission

Background Proteinuria is a powerful prognostic factor for end-stage renal disease in IgA nephropathy (IgAN) patients. However, it is not known whether proteinuria exacerbations are related to seasonal changes. Methods We retrospectively enrolled consecutive patients diagnosed with IgAN by kidney biopsy at our hospital between 2002 and 2014. Proteinuria remission was defined as urinary protein <0.3 g/gCr in two consecutive outpatient urinalyses and exacerbation as urinary protein ≥0.75 g/gCr. Four seasons were defined: spring (March–May), summer (June–August), autumn (September–November), and winter (December–February). We performed a multivariate analysis to identify factors associated with the second remission following a proteinuria exacerbation. Results We analyzed 116 patients. Proteinuria remission and exacerbation occurred in 77, and 43 patients, respectively. The incidence of proteinuria exacerbation was significantly higher in autumn and winter than in spring and summer (p = 0.040). The cumulative second remission rate was significantly higher in patients with autumn and winter proteinuria exacerbation than in patients with spring and summer exacerbations (p = 0.0091). In multivariate analyses, exacerbation onset in autumn and winter (hazard ratio [HR], 3.51; 95% confidence interval [CI], 1.41–8.74) and intensive therapy (HR, 2.26; 95% CI, 1.05–4.88) were significantly associated with a second proteinuria remission. Conclusion In IgAN patients in proteinuria remission, proteinuria exacerbation frequently occurred in autumn and winter. Exacerbations occurring in autumn and winter tended to remit early.

A CFD Analysis of Wave Interaction in a Multi-Tube PDE

In order to put a Pulse Detonation Engine (PDE) to practical use, the reduction of one cycle time is indispensable because the PDE supplies repetitive and intermittent thrust in its nature. As one of techniques to realize such demand, several attempts to use multi-tube combustor in one PDE are seen. To investigate the feasibility of such multi-tube PDE, it is important to understand the complicated pressure wave interaction among the combustion channels. In this study, the two-dimensional oxyhydrogen PDE model with two channels and a common nozzle is numerically simulated and the wave propagation and interaction inside the channels are discussed.

Numerical simulation of a Q-switched operation in a supersonic flow chemical oxygen-iodine laser

.4 Q-switched supersonic flow chemical oxygeniodine laser is simulated by solving the gas flow model coupled with the precise chemical kinetic model and the geometric optical model. The model includes the effects of hyperfine relaxation and velocity cross relaxation for iodine atoms. The effects of such relaxations and nonuniformity of the threedimensional flow field upon the power extraction are discussed. The results show that the peak power under the influence of hyperfine relaxation and velocity cross relaxation, which is normalized to the corresponding continuous wave value, is 15. It agrees fairly well with common experimental results of Qswitched chemical oxygen-iodine laser operations. The peak power of pulse in the three-dimensional flow field is considerably small compared to that in the equivalent one-dimensional flow field and the pulse is widened roughly twice due to insufficient mixing, shock waves, expansion waves and wakes.