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Influence of the upper mixed layer depth on Langmuir turbulence characteristics

Journal of Oceanology and Limnology 2023年第1期41卷 17-37页

作者： Guojing LI Changming DONG Jiayi PAN Adam T.DEVLIN Dongxiao WANG State Key Laboratory of Tropical Oceanography South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou 510301China Nanjing University of Information Science and Technology Nanjing 210044China Institute of Space and Earth Information Science the Chinese University of Hong KongHong Kong 999077China Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou) Guangzhou 510301China

The upper mixed layer depth(h)has a significant seasonal variation in the real ocean and the low-order statistics of Langmuir turbulence are dramatically influenced by the upper mixed layer depth.To explore the influence of the upper mixed layer depth on Langmuir turbulence under the condition of the wind and wave equilibrium,the changes of Langmuir turbulence characteristics with the idealized variation of the upper mixed layer depth from very shallow(h=5 m)to deep enough(h=40 m)are studied using a non-hydrostatic large eddy simulation model.The simulation results show that there is a direct entrainment depth induced by Langmuir turbulence(h_(LT))within the thermocline.The normalized depthaveraged vertical velocity variance is smaller and larger than the downwind velocity variance for the ratio of the upper mixed layer to a direct entrainment depth induced by Langmuir turbulence h/h_(LT)1,respectively,indicating that turbulence characteristics have the essential change(i.e.,depth-averaged vertical velocity variance(DAVV)DADV for Langmuir turbulence)between h/h_(LT)1.The rate of change of the normalized depth-averaged low-order statistics for h/h_(LT)1.The reason is that the downward pressure perturbation induced by Langmuir cells is strongly inhibited by the upward reactive force of the strong stratified thermocline for h/h_(LT)1.Hence,the upper mixed layer depth has significant influences on Langmuir turbulence characteristics.

关键词： the upper mixed layer depth Langmuir turbulence turbulent characteristics large eddy simulation

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Alluvial channel hydrodynamics around tandem piers with downward seepage

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Frontiers of Structural and Civil Engineering 2020年第6期14卷 1445-1461页

作者： Rutuja CHAVAN Wenxin HUAI Bimlesh KUMARC Department of Civil Engineering Maulana Azad National Institute of Technology BhopalBhopalMadhya Pradesh 462003India Department of Harbor School of Water Resources and Hydropower EngineeringWuhan UniversityWuhan 430072China Department of Civil Engineering Indian Institute of Technology GuwahatiGuwahati 781039India

In this paper,we report the turbulent flow structures and the scour geometry around two piers with different diameters.An experiment was conducted on a non-uniform sand bed with two types of tandem arrangements,namely,pier(T1)with a 75 mm front and 90 mm rear,and pier(T2)with a 90 mm front and 75 mm rear,with and without-seepage flows,respectively.A strong wake region was observed behind the piers,but the vortex strength diminished with downward seepage.Streamwise velocity was found to be maximum near the bed downstream of the piers and at the edge of the scour hole upstream of the piers.Quadrant analysis was used to recognize the susceptible region for sediment entrainment and deposition.Upstream of the piers near the bed,the moments,turbulent kinetic energy(TKE),and TKE fluxes were found to decrease with downward seepage,in contrast to those in a plane mobile bed without piers.The reduction percentages of scour depth at the rear pier compared with the front one were approximately 40%for T1 and 60%for T2.Downward seepage also resulted in restrained growth of scouring with time.

关键词： scour seepage Strouhal number tandem arrangement turbulent characteristics

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turbulent structure in uniform inclined open channel flow over different rough porous beds

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International Journal of Sediment Research 2017年第1期32卷 45-52页

作者： Evangelos Keramaris University of Thessaly Department of Civil EngineeringDivision of Hydraulic and Environmental Engineering

In this study the effects of the different rough porous beds in an open inclined channel are studied experimentally for impermeable and permeable porous bed.For the simulation of porous bed two different types of permeable bed with the same thickness(s’ = 3 cm) and the same porosity ε=0.70 are used:(a) porous filters and(b) gravel bed.Laboratory experiments were used for the calculation of turbulent velocity profiles.Measurements of velocity were taken for inclined channel for three different slopes(S=-0.002,S=-0.004 and S=-0.006) and for five different flow depths(h=5 cm,7 cm,9 cm,11 cm and 13 cm).The total discharge Q varies from 0.78 to 1.31 1/s.The measurements were obtained using a two-dimensional(2D) Particle Image Velocimetry(PIV).The total discharge was estimated using a calibrated venture apparatus.Results showed that the presence of rough porous bed in inclined open channels influence significantly the turbulent characteristics of the flow in comparison with impermeable open channels with the same slopes.

关键词： Particle image velocimetry Porous filters Gravel bed Channel slope turbulent characteristics

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