High-resolution atmospheric, climate large-ensemble simulations are used to assess future changes in heavy rainfall events. In most parts of the world, the rate of increase in precipitation is noticeably larger for events occurring once in 100 years than those occurring once every year. The increase can be decomposed into two contributions. One is that from water vapor in the atmosphere that increases ~7% per 1-K temperature rise. The other is that from upward motion that lifts up near-surface water vapor to condensate into rainfall. The simulation results show that the upward motion in the middle and upper troposphere conspicuously increases for the events occurring once in 100 years.

Under the background of enrichment of the precipitation database, which is based on the climate change projection, future-change projection of flood risk is already developing. However, when we focus on the sediment-related hazard on a watershed scale, sediment production and transport in the catchment should be carefully treated. In this description paper, firstly, we introduce the structure of the simulation model SiMHiS, composed of a sediment production and supply model based on landslide prediction, rainfall infiltration and runoff, and sediment transport in the channel system. Secondly, we introduce a future-projection result in the Akatani River watershed in Northern Kyushu Island, Japan, damaged by heavy rainfall in 2017. Maximum water discharge, total volume of sediment discharge, maximum water level, and maximum riverbed level at specific locations are selected as indicators for the assessment. For the rainfall data, local extreme values of heavy rainfall data that occurs in northern Kyushu during the rainy season were given to the simulation to evaluate the future change of the extreme event by using the limited period of the dataset. The results showed a clear increasing trend for all indexes, indicating that phenomena of a scale that does not occur in the current climate might occur. We also discussed the possibility of statistical and quantitative evaluation in future studies using our method with the precipitation dataset, which has finer spatiotemporal resolution and a more extended period.

Sea level rise is expected to cause significant normal-state shoreline retreat and higher waves due to changes in wave climate are expected to cause significant temporary shoreline retreat. The shoreline changes will increase the risk of coastal disasters. The Bruun rule is currently widely used to predict shoreline retreat due to sea level rise, although its reliability should be improved. The effective use of long-term beach monitoring data with deep neural networks can lead to a better understanding of the processes of beach response to sea level rise.

The wall friction term in a one-dimensional model vanishes under the stagnant liquid conditions (i.e. the liquid volume flux J_L = 0). Hence void fraction α_G(ΔP) in rod bundles have been evaluated using measured pressure gradients dP/dz. However, effects of the wall friction term on α_G(ΔP) have not been quantitatively evaluated. In this study, we therefore carried out air-water experiments using a 3×3 rod bundle under the conditions of J_L = 0, and measured dP/dz and α_G,exp with the closing valve method. We obtained the dimensionless wall friction force F_w^* (= α_G(ΔP)－α_G,exp) from the measured dP/dz and α_G,exp. The F_w^* values were expressed by using the gas volume flux J_G, because the liquid flow field was induced by the gas flow (i.e. J_G). The difference between α_G,exp and α_G(ΔP) was reduced by half after α_G(ΔP) was corrected using the obtained correlation for F_w^*. The F_w^* correlation was applied to existing α_G(ΔP) data for 4×4 and 8×8 bundles, and effects of F_w^* on the α_G(ΔP) values were confirmed to be small in a large rod bundle due to the small wall area per unit fluid volume.

In our previous studies, we carried out air-water counter-current flow experiments under flooding conditions in vertical pipes of 40 mm diameter with combinations of sharp-edged or rounded top and bottom ends to measure counter-current flow limitation (CCFL), pressure gradient dP/dz, and void fraction α_G. We obtained the wall and interfacial friction factors, f_w and f_i, and proposed a correlation of f_w. In the present study, we carried out similar experiments with sharp-edged top and bottom ends, and obtained f_w and f_i. We proposed a correlation of f_i for all flow patterns including smooth film (SF) and rough film (RF) due to flooding at the top and bottom ends, respectively. By using the one-dimensional annular flow model and the proposed f_w and f_i correlations, we computed the liquid volume fraction α_L,cal and compared it with the experimental data α_L,exp. The computation gave two solutions of α_L,cal for SF and RF, which agreed relatively well with the α_L,exp values for SF and RF in the regions of low gas superficial velocity J_G and high J_G, respectively.

Passive production of synthesis gas from liquid methanol using a packed bed of porous particles supporting a catalyst is investigated. Heating of an upper side of the packed tube the bottom of which is immersed in liquid methanol causes upward flow by the capillary action enhanced by evaporation and syn-gas is produced in temperature increased dried region. The extension of the dried region toward the wetted region reduces considerably the responsiveness in the productions of the reactant vapor and syn-gas due to the high flow resistance of the bed. Utilization of a combined particle bed, which consists of two different size particles geometrically arranged and separates the dried and wetted regions to the prescribed ranges, allows low flow resistance and, as a result, causes significant increases in the mass flow rate and the responsiveness.