Study on Optimization of Flood Discharge Types in MHSJ Stilling Basin

At the beginning of the operation of a Hydropower Station adopted a new type of stilling basin with multi-horizontal submerged jets (MHSJ), it was found there was a phenomenon of roller shutter door and window vibration in some local area of the downstream region during the flood discharging process. The prototype observation indicated that the flow induced vibration is greatly influenced by flood discharging types with different open combination of the sluice gates. Flow fluctuating pressure is a main load that frequently causes damages to flood discharge structures, which is a crucial incentive that caused flow induced vibration of the downstream region of the hydropower station. In this paper, from the perspective of hydraulics, the flood discharging types with different open combination of the sluice gates under same flood discharge were simulated through a series of hydraulic model experiments. Judged by the values of fluctuating pressure on the bottom plate of stilling basin, it was found the joint discharging type of surface outlets and middle outlets is better than surface outlets discharging type or middle outlets discharging type. The response law between discharge allocation proportion of each outlet and fluctuating pressure characteristics in the still basin was preliminary revealed. The optimal flood discharge types were obtained. The research results can provide technical support for the operation and management of the Hydropower Station. The reduction of vibration intensity from the source is expected

Effect of Water Column Stability on Surface Chlorophyll and Time Lags under Different Nutrient Backgrounds in a Deep Reservoir

Hydrodynamic conditions are considered to be very important in the control of algal blooms. Weekly or daily measurements may miss some important events in the hydrodynamic process, resulting in inaccurate evaluations of the impacts of hydrodynamics on phytoplankton. In this study, high-frequency (15-min interval) measurements were used to analyze the effect of water column stability on surface chlorophyll a (Chl a) and lag time under different nutrient backgrounds during a cyanobacterial bloom in the Three Gorges Reservoir, China. Cross-correlation analysis between the relative water column stability (RWCS) and Chl a was performed at different stages. The results showed that the RWCS above the euphotic depth influenced the surface Chl a concentration most significantly. A lower RWCS (&lt;20) limited the increase in the Chl a concentration, and a higher RWCS caused a significant increase in Chl a only when nutrients were not limited (TN/TP &lt; 29) and light and temperature conditions were suitable. It took a short time for a higher RWCS to significantly increase the surface Chl a concentration compared with a lower RWCS. When the waterbody had a very low Chl a concentration (almost 0), approximately 2 days were needed to significantly increase the Chl a concentration, while approximately only half an hour was needed when the background concentration of Chl a was slightly higher. During the bloom period, a decline in the RWCS significantly decreased the Chl a in a very short time (approximately half an hour). Reducing the water column stability could be a good approach to control cyanobacterial blooms.</p

Comparative Study on the Hydraulic Characteristics of Nature-Like Fishways

Due to the complex structure and the multiformity of boulder arrangements, there is currently no perfect design criterion for nature-like fishways. This paper proposes four types of nature-like fishways arranged with an impermeable partition wall (IPW), a semi-permeable partition wall (SPPW) or a fully permeable partition wall (FPPW). The hydraulic characteristics of these fishways were investigated experimentally. The results show that the discharge of the fishway arranged with a FPPW was almost twice that of an IPW fishway, and the discharge of a SPPW fishway was between the two extremes. The mean flow velocity of the FPPW fishway was larger than that of the other schemes. For the fishway arranged with an IPW, the flow information was basically consistent with that of the engineered technical fishway. In the FPPW or SPPW fishway, there was more abundant flow information and no obvious recirculation zones in the fishway pool, and these conditions are suitable for migratory fish moving up- and downstream. Notably, for the fishway arranged with two fish passages, two mainstreams were formed in the pool, which divided the flow pattern of the pool into three flow regions. A weak recirculation area was formed in the low-velocity region, which facilitates swimming for migratory fish. According to this comprehensive comparative study, the SPPW fishway with two fish passages had low discharge, abundant flow information and favorable fish migration characteristics; thus, it is the optimal fishway scheme among those studied in this paper

Impact Pressure Influence of Flood on Bridge Deck under Sediment Deposition Conditions: An Experimental Study

This paper investigates the impact of sediment deposition and inflow conditions on horizontal impact pressure and frequency analysis of bridge deck vibrations during flooding. Flooding-induced pressure and vibrations contribute to bridge collapse, and sediment deposition influences water flow and impact pressure. The study explores the relationship between sediment deposition height and impact pressure, revealing a significant increase as sediment approaches 50% of bridge deck clearance. Sediment amplifies impact pressure response to flow velocity changes. The dimensionless sediment deposition height has a greater influence on impact pressure compared to the inflow Froude number. Two distinct frequencies, dominant and secondary, are identified for impact pressure and water level fluctuations. Dominant frequencies positively correlate with sediment deposition height and Froude number, indicating an increasing trend. Secondary frequencies remain stable (0.31–0.58 Hz). These findings enhance understanding of flow dynamics and bridge–flow interaction in sediment-deposited channels, providing theoretical support for evaluating and managing disasters related to bridges in such environments. Overall, this research contributes to the field of bridge engineering and supports improved design and maintenance practices for bridges exposed to sediment-deposited channels

Label-Free Microchannel Immunosensor Based on Antibody–Antigen Biorecognition-Induced Charge Quenching

Pursuing convenient operations and precise testing have become an urgent requirement in clinical diagnosis, treatment, and prognosis. Label-free detection is desirable for obviating the labeling process while maintaining high sensitivity and efficiency. Here, we used the dual properties of highly selective antibody–antigen recognition and potential signaling of biomolecules to construct a label-free electroosmotic flow-driven microchannel (LF-EMB) biosensor based on an antibody–antigen biorecognition-induced charge quenching theory proposed herein. The LF-EMB consists of a one-step immune-reaction, one-button portable device, and supporting microfluidic chip, providing a high-powered tool for rapid on-site testing. The LF-EMB quantified interleukin-6 and kanamycin levels down to 1 pg/mL and 5 pg/mL, respectively, with the whole analysis completed within 35 min. The outstanding sensitivity and detection speed of the constructed LF-EMB provide a convenient option for the quantitative detection of inflammatory markers and antibiotics

Mesophilic Argonaute-Mediated Polydisperse Droplet Biosensor for Amplification-Free, One-Pot, and Multiplexed Nucleic Acid Detection Using Deep Learning

Detection of nucleic acids from a single multiplexed and amplification-free test is critical for ensuring food safety, clinical diagnostics, and environmental monitoring. In this study, we introduced a mesophilic Argonaute protein from Clostridium butyricum (CbAgo), which exhibits nucleic acid endonuclease activity, to achieve a programmable, amplification-free system (PASS) for rapid nucleic acid quantification at ambient temperatures in one pot. By using CbAgo-mediated binding with specific guide DNA (gDNA) and subsequent targeted cleavage of wild-type target DNAs complementary to gDNA, PASS can detect multiple foodborne pathogen DNA (2 CFU/mL) simultaneously. The fluorescence signals were then transferred to polydisperse emulsions and analyzed by using deep learning. This simplifies the process and increases the suitability of polydisperse emulsions compared to traditional digital PCR, which requires homogeneous droplets for accurate detection. We believe that PASS has the potential to become a next-generation point-of-care digital nucleic acid detection method