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NOTES are short manuscripts describing new developments or important results of a preliminary nature. These Notes should not exceed 2500 words (where a figure or table counts as 200 words). Following informal review by the Editors, they may be published within a few months of the date of receipt. Style requirements are the same as for regular contributions (see inside back cover).

Hypersonic boundary-layer transition can be affected significantly by surface roughness. Many important mechanisms which involve transition induced by arbitrary roughness are not well understood. In this paper, we propose a new high-order cut cell method which combined the non-uniform finite difference method for discrete points near the curvilinear boundary and shock-fitting method for the bow shock. The receptivity process induced by interaction of Mach 5.92 flow over flat plate under the combination effect of twodimensional surface roughness and blow-suction is investigated. Both steady state solutions and unsteady solutions have been obtained by using the new method. For steady flow with roughness, there is significant change inside the boundary layer with flow separation before and after the roughness element. For unsteady flow, the results for flow instability induced by both blow-suction slot and roughness are obtained and analyzed by Linear Stability Theory (LST). These results show that the roughness element with height to be half the boundary layer thickness may delay the hypersonic transition.

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A flash flood disaster is one of the most destructive natural disasters. With the increase in extreme rainfall events, more and more areas will be threatened by flash floods. The flash flood susceptibility assessment is the basis of flash flood risk assessment and is also an important step in flash flood disaster management. Based on Citespace analysis tools, this study made a bibliometric and visualized analysis of 305 documents collected in the core collection of Web of Science in the past 15 years, including the analysis of the number of publications and citation frequency, influence analysis, keyword analysis, author co-citation analysis, and institutional co-operation analysis. This paper summarizes the current research status and future development trend of flash flood susceptibility assessment from five key research subfields, including assessment scale, assessment unit, assessment index, assessment model, and model assessment method, discusses the analysis of the application of remote sensing and GIS in flash flood susceptibility assessment, discusses the problems encountered in the current research of the five subfields, and provides suggestions for flash flood hazard control.