End-member modeling analysis of tidal flat sediments grain size and their implications for sedimentary sources from Jiangsu coast, Eastern China

582-589Sediment grain-size distributions (GSDs) provide rich information about sedimentary sources and potentially about environmental and climatic changes. However, neither traditional descriptive statistics nor curving fitting methods are able to address this complexity fully. In this study, end-member modeling analysis (EMMA) was conducted on the GSDs of tidal flat samples from the Jiangsu coast. Based on the frequency and spatial distributions of the end members (EMs), the sedimentary sources of each EM were discussed. The results show that EM1 comprises 76.07-100% of the total grain sizes between YTJ and CM3 and represents Yangtze River as a dominant supplier. EM2 comprises 50.50% to 95.6% of the total grain sizes between DF and LSG, reflecting that the coast is the transitional zone influenced by Yellow River and Yangtze River. EM3 comprises 50.33% to 100% of the total grain sizes between GHK1 and DLG, showing Yellow River as a dominant supplier. EM4 comprises 88% to 97.53% of the total grain sizes between LD1 and LD3, reflecting that the tidal flat sediments of Liandao Island were mainly from the nearshore rock weathering. Compared to the traditional method of sediment grain size analysis, EMMA can determine the EMs and provide better explanations of the sediment provenance and regional sedimentary environment in the study area

Correlation analysis of separation shock oscillation and wall pressure fluctuation in unstarted hypersonic inlet flow

The flow field in a hypersonic inlet model at a design point of M = 6 has been studied experimentally. The focus of the current study is to present the time-resolved flow characteristics of separation shock around the cowl and the correlation between the separation shock oscillation induced by the unstart flow and the wall pressure fluctuation when the inlet is in a state of unstart. High-speed Schlieren flow visualization is used to capture the transient shock structure. High-frequency pressure transducers are installed on the wall around both the cowl and isolator areas to detect the dynamic pressure distribution. A schlieren image quantization method based on gray level detection and calculation is developed to analyze the time-resolved spatial structure of separation shock. Results indicate that the induced separation shock oscillation and the wall pressure fluctuation are closely connected, and they show the same frequency variation characteristics. The unsteady flow pattern of the “little buzz” and “big buzz” modes are clarified based on time-resolved Schlieren images of separation shock. Furthermore, the appropriate location of the pressure transducers is determined on the basis of the combined analysis of fluctuating wall-pressure and oscillating separation shock data