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Numerical simulation of inlet placement on sewage characteristics in the rounded square aquaculture tank with single inlet

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Journal of oceanology and Limnology 2024年第4期42卷 1359-1382页

作者： Xiaozhong REN Yixuan HU Yinxin ZHOU Shupeng DU Wei SUN Hangfei LIU Chenxu ZHAO Ying LIU Key Laboratory of environment Controlled Aquaculture(Dalian ocean University)Ministry of Education Dalian 116023China college of Marine Science and environment Dalian Ocean UniversityDalian 116023China college of ocean and Civil engineering Dalian Ocean UniversityDalian 116023China Zhejiang University Hangzhou 310058China

To improve the self-cleaning ability of aquaculture tank and the efficiency of circulating water,physical and numerical experiments were conducted on the influence of inlet structure on sewage discharge in a rounded square aquaculture tank with a single *** on the physical model of the tank,analysis of how inlet structure adjustment affects sewage discharge efficiency and flow field characteristics was conducted to provide suitable flow field conditions for sinkable solid particle *** addition,an internal flow field simulation was conducted using the RNG k-εturbulence model in hydraulic drive *** a solid-fluid multiphase model was created to investigate how the inlet structure affects sewage collection in the rounded square aquaculture tank with single inlet and *** finding revealed that the impact of inlet structure is considerably affecting sewage *** conditions of C/B=0.07-0.11(the ratio of horizontal distance between the center of the inlet pipe and the tank wall(C)to length of the tank(B))andα=25°(αis the angle between the direction of the jet and the tangential direction of the arc angle)resulted in optimal sewage collection,which is similar to the flow field experiment in the rounded square aquaculture tank with single inlet and *** excellent correlation was revealed between sewage collection and fluid circulation stability in the aquaculture *** present study provided a reference for design and optimization of circulating aquaculture tanks in aquaculture industry.

关键词： rounded square aquaculture tank sewage collection characteristic inlet structure computational fluid dynamic

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Effects of inorganic nutrients and environmental factors on the removal of n-propylbenzene and isopropylbenzene in seawater by cryptophytes Rhinomonas reticulata S6A

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Journal of oceanology and Limnology 2024年第4期42卷 1200-1215页

作者： Jiali CUI Shuhao DU Yumei LI Haiping LI Ping ZHANG Fanping MENG Key Laboratory of Marine environment and Ecology Ministry of EducationOcean University of ChinaQingdao 266100China college of environmental Science and engineering Ocean University of ChinaQingdao 266100China

To effectively remove n-propylbenzene(n-PBZ)and isopropylbenzene(i-PBZ)leaked into seawater using Rhinomonas reticulata S6A(a newly isolated marine microalga),the effects of three inorganic nutrients and four environmental factors on their degradation were determined after 7 d of *** show that NaNO_(3) at 300 mg/L caused a higher removal efficiency of both n-PBZ and i-PBZ(44.79%and 39.26%),while for NaH_(2) PO_(4)·H_(2) O,greater removal rates of two PBZs(47.30%and 42.23%)were achieved at 30 and 20 mg/L,***_(3) supplementation(500-750 mg/L)resulted in a large reduction(43.67%-45.04%)in i-PBZ *** change in seawater pH(from 6 to 9)did not affect the elimination of n-PBZ and *** most suitable salinity and temperature were 30 and 25-30℃,respectively,leading to the PBZs removal of~40%.Light intensity exhibited significant influence on elimination of PBZs,and the maximum removal efficiencies of 56.07%(n-PBZ)and 55.00%(i-PBZ)were recorded under 200 and 600μmol/(m^(2)·s),*** addition,the microalga could still remove PBZs when it failed to grow well due to darkness,strong light,low temperature,or low salinity,which might mean that good growth of alga is not always a necessary condition for PBZs ***,attention should be paid to the suitability of nutrient levels and environmental conditions(excluding pH)in seawater when using microalgae for bioremediating PBZs-contaminated seawater.

关键词： propylbenzene(PBZ) Rhinomonas reticulata seawater inorganic nutrient environmental factor

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Landsat Image-Based Spatiotemporal Variation Analysis of Erosion and Deposition off the Qingshuigou of the Yellow River Delta from 1984 to 2021

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Journal of ocean University of China 2024年第5期23卷 1173-1184页

作者： DONG Sheng LI Songda TAO Shanshan college of engineering Ocean University of China

Owing to climate change and human activity, the Qingshuigou of the Yellow River Delta(YRD) has undergone dynamic changes in erosion and deposition. Therefore, studying these changes is important to ensure ecological protection and sustainable development. In this study, the trend of erosion-deposition evolution in the Qingshuigou was investigated based on 38 coastline phases extracted from Landsat series images of the YRD at one-year intervals from 1984 to 2021. The periodicity of the scouring and deposition evolution was also analyzed using wavelet analysis. Results showed that the total area of the Qingshuigou was affected by deposition and erosion and that the fluctuation first increased and then decreased. The total area reached a maximum in 1993. The depositional area first increased and then decreased, whereas the overall erosion area decreased. Deposition and erosion areas showed periodic changes to some extent; however, the periodic signal intensity decreased. Furthermore, factors including channel morphological evolution and variations in water and sediment discharge affect the spatiotemporal dynamics of erosion and deposition processes. The application of nonconsistency tests finally revealed that deposition area and flushing magnitude exhibited non-stationarities, which are potentially attributed to impacts from climatic change drivers.

关键词： coastline erosion and deposition remote sensing wavelet analysis Yellow River Delta

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Flow-Slip Stability Behavior of Calcareous Sand Treated by Microbially Induced Carbonate Precipitation Technology

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Journal of ocean University of China 2024年第5期23卷 1381-1389页

作者： KOU Hailei HE Xiang HOU Wangxiang LI Zhendong ZHANG Xixin AN Zhaotun LU Jiaqing college of engineering Ocean University of China

Flow-slip damage commonly destabilizes coastal slopes. Finding a slope stabilization method for calcareous sands in the South China Sea is crucial. Microbially induced calcite precipitation is a promising, eco-friendly method for soil stabilization. This study investigates the effect of microbial treatments, initial relative density, initial cell pressure, and initial stress ratio on the flow-slip stability of calcareous sand specimens by using constant shear drained tests. These tests lay the foundation to study the mechanical instability of sand slopes. Results show that the microbial-treated specimens maintain stable stresses longer, take longer to reach the instability, and withstand larger volumetric strains. Microbial treatment effectively enhances sand stability under constant shear drainage, with improvements amplified by higher initial relative density and initial cell pressure. In addition, a smaller initial stress ratio reduces shear effects on the specimen and increases resistance to flow slides. Microanalysis reveals that the flow-slip stability of calcareous sand slopes is enhanced by contact cementation, particle coating, void filling, and mutual embedment of calcium carbonate crystals.

关键词： clcareous sand constant shear drained tests flow-slip stability microbially induced carbonate precipitation

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Reliability analysis of carbon fiber rod-reinforced umbilical cable under tension using an improved sampling method

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Petroleum Science 2024年第4期21卷 2769-2778页

作者： Yu Zhang Hong-Yu Zhang Ran Xia Si-Ao Jiang Fang Wang college of Safety and ocean engineering China University of Petroleum China Academy of Aerospace Aerodynamics China Aerospace Science and Technology Group college of engineering Science and Technology Shanghai Ocean University

The umbilical cable is a vital component of subsea production systems that provide power, chemical agents, control signals et al., and its requirement for reliability is exceedingly high. However, as the umbilical cable is a composite structure comprising multiple functional units, the reliability analysis of such cables involves numerous parameters that can impact calculation efficiency. In this paper, the reliability analysis of a new kind of umbilical cable with carbon fiber rod under tension is analyzed. The global dynamic analytical model is first established to determine the maximum tension load, then the local analytical model of umbilical cable including each unit are constructed by finite element method(FEM). Based on the mechanical analytical model, the reliability of umbilical cable under tension load is studied using response surface method(RSM) and Monte Carlo method. During the calculation process, a new tangent plane sampling method to calculate the response surface function(RSF) is proposed in this paper, which could make sampling points faster come close to the RSF curve, and it is proved that the calculation efficiency increases about 33% comparing with traditional method.

关键词： Umbilical cable Carbon fiber rod Failure analysis Response surface method Reliability

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Glycine-β-cyclodextrin-assisted cometabolism of phenanthrene and pyrene by Pseudomonas stutzeri DJP 1 from marine sediment

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Journal of oceanology and Limnology 2024年第2期42卷 560-569页

作者： Junfeng JIANG Weijun TIAN Zhiyang LU Meile CHU Huimin CAO Dantong ZHANG college of environmental Science and engineering Ocean University of ChinaQingdao 266100China Key Laboratory of Marine environment and Ecology Ministry of EducationQingdao 266100China

Cometabolic degradation is currently an effective and extensively way to remove high molecular weight polycyclic aromatic hydrocarbons(HMW-PAHs).Unfortunately,due to low bio-accessibility and high biotoxicity,the cometabolic degradation rate of HMW-PAHs is ***-β-cyclodextrin(GCD)was obtained through amino modification ofβ-cyclodextrin(BCD)and added to cometabolic system of phenanthrene(PHE)and pyrene(PYR)to assist PYR *** show that the addition of GCD(100 mg/L)effectively improved the removal rate of PYR(20 mg/L)by 42.3%.GCD appeared to increase the bio-accessibility and reduce the biotoxicity of PHE and PYR,and then promoted the growth of Pseudomonas stutzeri DJP1 and stimulated the elevation of dehydrogenase(DHA)and catechol 12 dioxygenase(C12O)*** phthalate metabolic pathway was accelerated,which improved the cometabolic *** study provided a new reference for the cometabolic degradation of HMW-PAHs.

关键词： cometabolism phenanthrene pyrene glycine-β-cyclodextrin biological accessibility biotoxicity

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Analytical and Experimental Research on Wave Scattering by an Open-Type Rectangular Breakwater with Horizontal Perforated Plates

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Journal of ocean University of China 2024年第5期23卷 1185-1201页

作者： HE Shuyue LIU Yong LI Huajun Fisheries college Ocean University of China Shandong Province Key Laboratory of ocean engineering Ocean University of China

This study proposes a novel open-type rectangular breakwater combined with horizontal perforated plates on both sides to enhance the sheltering effect of the rectangular box-type breakwaters against longer waves. The hydrodynamic characteristics of this breakwater are analyzed through analytical potential solutions and experimental tests. The quadratic pressure drop conditions are exerted on the horizontal perforated plates to facilitate assessing the effect of wave height on the dissipated wave energy of breakwater through the analytical solution. The hydrodynamic quantities of the breakwater, including the reflection, transmission, and energyloss coefficients, together with vertical and horizontal wave forces, are calculated using the velocity potential decomposition method as well as an iterative algorithm. Furthermore, the reflection and transmission coefficients of the breakwater are measured by conducting experimental tests at various wave periods, wave heights, and both porosities and widths of the horizontal perforated plates. The analytical predicted results demonstrate good agreement with the iterative boundary element method solution and measured data. The influences of variable incident waves and structure parameters on the hydrodynamic characteristics of the breakwater are investigated through further calculations based on analytical solutions. Results indicate that horizontal perforated plates placed on the water surface for both sides of the rectangular breakwater can enhance the wave dissipation ability of the breakwater while effectively decreasing the transmission and reflection coefficients.

关键词： analytical solution experimental test horizontal perforated plates hydrodynamic characteristics rectangular breakwater

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Insight into the Inhibition of the Poisonous Sulfide Production from Sulfate-Reducing Microbiota in Mariculture Habitat

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Journal of ocean University of China 2024年第2期23卷 447-454页

作者： ZHAO Xuning ZHANG Zhiming ZHAO Yangguo MUPINDU Progress Shandong Provincial Key Laboratory of Marine environment and Geological engineering(MEGE) College of Environmental Science and EngineeringOcean University of ChinaQingdao 266100China Key Laboratory of Marine environmental Science and Ecology(ocean University of China) Ministry of EducationQingdao 266100China

The production of toxic sulfides is a common environmental problem in ***,the effective inhibition of sulfidogens is the key to prevent sulfides *** this study,the possibility and mechanism of nitrate(NO_(3)^(−))inhibiting the activity of the sulfate-reducing microbiota(SRM)from mariculture sediments was *** results showed that 1,3,and 5 mmol L^(−1)NO_(3)^(−)continuously inhibited sulfide production for 1-3 *** NO_(3)^(−) dosage increased to 7 mmol L^(−1),the duration of inhibition increased to 6 *** product NO_(2)^(−)heavily inhibited the activity of dissimilar sulfate reductase gene(dsrB)by 3 orders,which was the main reason that the sulfate-reducing activity was *** SRM structure changed significantly with the dosage of NO_(3)^(−),while the abundance of sulfidogens Desulfovibrio species increased due to their capability of detoxifying nitrite through nitrite ***,sulfidogens Desulfovibrio species are more adaptable to a high nitrate/nitrite environment,and the traditional control strategies by dosing nitrate/nitrite should be paid more attention *** findings will serve as helpful guidelines for sulfate-reducing microbiota in the habitat of mariculture to reduce their generation of poisonous sulfide.

关键词： sulfate-reducing microbiota sulfide nitrate Desulfovibrio mariculture

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Molecular dynamics simulation of the flow mechanism of shear-thinning fluids in a microchannel

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Chinese Physics B 2024年第4期33卷 516-525页

作者：杨刚郑庭程启昊张会臣 Naval Architecture and ocean engineering college Dalian Maritime UniversityDalian 116026China

Shear-thinning fluids have been widely used in microfluidic systems,but their internal flow mechanism is still ***,in this paper,molecular dynamics simulations are used to study the laminar flow of shear-thinning fluid in a *** validated the feasibility of our simulation method by evaluating the mean square displacement and Reynolds number of the solution *** results show that the change rule of the fluid system's velocity profile and interaction energy can reflect the shear-thinning characteristics of the *** velocity profile resembles a top-hat shape,intensifying as the fluid's power law index *** interaction energy between the wall and the fluid decreases gradually with increasing velocity,and a high concentration of non-Newtonian fluid reaches a plateau ***,the velocity profile of the fluid is related to the molecule number density distribution and their values are inversely *** analyzing the radial distribution function,we found that the hydrogen bonds between solute and water molecules weaken with the increase in *** observation offers an explanation for the shear-thinning phenomenon of the non-Newtonian flow from a micro perspective.

关键词： molecular dynamics simulation non-Newtonian fluid microchannel shear-thinning

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Frequency Domain Fatigue Evaluation on SCR Girth-Weld Based on Structural Stress

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China ocean engineering 2024年第2期38卷 255-270页

作者： ZHANG Long ZHAO Tian-feng college of Safety and ocean engineering China University of Petroleum(Beijing)Beijing 102249China

The Steel Catenary Riser(SCR)is a vital component for transporting oil and gas from the seabed to the floating *** harsh environmental conditions and complex platform motion make the SCR’s girth-weld prone to fatigue *** structural stress fatigue theory and Master S-N curve method provide accurate predictions for the fatigue damage on the welded joints,which demonstrate significant potential and compatibility in multi-axial and random fatigue ***,we propose a new frequency fatigue model subjected to welded joints of SCR under multiaxial stress,which fully integrates the mesh-insensitive structural stress and frequency domain random process and transforms the conventional welding fatigue technique of SCR into a spectrum analysis technique utilizing structural ***,a full-scale FE model of SCR with welds is established to obtain the modal structural stress of the girth weld and the frequency response function(FRF)of modal coordinate,and a biaxial fatigue evaluation about the girth weld of the SCR can be achieved by taking the effects of multi-load correlation and pipe-soil interaction into *** research results indicate that the frequency-domain fatigue results are aligned with the time-domain results,meeting the fatigue evaluation requirements of the SCR.

关键词： SCR girth weld random vibration self(cross)power spectrum structural stress method biaxial fatigue damage

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