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Effects of operating condition on fish behavior and fish injury in an axial pump

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Science China(Technological Sciences) 2022年第1期65卷 157-168页

作者： YANG DanDan ZHAO MingXiang SHEN Lian LUO XianWu State Key laboratory of Hydroscience and engineering Department of Energy and Power EngineeringTsinghua UniversityBeijing 100084China saint anthony falls laboratory&department of mechanical engineering University of MinnesotaMinneapolisMN 55414USA

In this study,fish behavior and fish injury at different operating conditions are investigated via numerical simulation to evaluate the fish-friendliness of an axial pump that comprises an inlet pipe,a rotor with six blades,a stator with eight vanes,and an outlet *** precisely obtain the flow field when the fish passes through the axial pump,a hybrid large eddy simulation and immersed boundary method is adopted with the full consideration of the fluid-structure interaction *** results indicate that the collision between the fish and the wall of flow components in the axial pump is concentrated near the inlet of the rotor,which results in the complexity of the fish trajectory,especially under the large flow rate *** is noted that the fish is likely to move in the reverse direction of the main flow after the impact with the rotor blade if the flow rate coefficient is too large,which increases the possibility of collision between the fish and the rotor *** is also indicated that the primary factor affecting the strike injury on the fish when it passes through the axial pump is the strike between the fish and the leading edge of the rotor *** addition,the strike injury becomes more significant as the flow rate coefficient ***,the results demonstrate that the fish may simultaneously suffer from strike,pressure,and shear stress injuries,once the collision between the fish and the wall of flow components occurs in the axial pump,thus aggravating the combined damage on the *** on these results,it is recommended that hydraulic machinery should not be operated at large flow rates during fish migration from the view of fish-friendliness.

关键词： axial pump fish behavior fish injury immersed boundary(IB)method fluid-structure interaction(FSI)

Simulation-based study of wind-wave interactions under various sea conditions

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Journal of Hydrodynamics 2019年第6期31卷 1148-1152页

作者： Xuanting Hao Tianyi Li Tao Cao Lian Shen department of mechanical engineering and saint anthony falls laboratory University of MinnesotaMinneapolisMinnesotaUSA

Despite their importance in the ocean environment,the key physical processes in wind-wave interactions are poorly *** a solver developed for undulatory boundaries,we perform numerical simulations of the wind-wave system under various sea conditions,including wind over monochromatic waves,early wind-wave generation,and wind over a broadband wave *** results show that the wave direction and wave age can significantly change the distribution of streamwise vorticity in the wind *** wave patterns are observed in the process of wind-wave *** a broadband wave field,the wave growth rate due to wind input is found to depend on the wave steepness.

关键词： Wind-wave interaction direct numerical simulation large eddy simulation phase-resolved wave simulation

Relationship between wall shear stresses and streamwise vortices in turbulent flows over wavy boundaries

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Applied Mathematics and Mechanics(English Edition) 2019年第3期40卷 381-396页

作者： Lihao WANG Weixi HUANG Chunxiao XU Lian SHEN Zhaoshun ZHANG Applied Mechanics laboratory Department of Engineering MechanicsTsinghua University department of mechanical engineering and saint anthony falls laboratory University of Minnesota

The relationship between wall shear stresses and near-wall streamwise vortices is investigated via a direct numerical simulation(DNS) of turbulent flows over a wavy boundary with traveling-wave motion. The results indicate that the wall shear stresses are still closely related to the near-wall streamwise vortices in the presence of a wave. The wave age and wave phase significantly affect the distribution of a two-point correlation coefficient between the wall shear stresses and streamwise vorticity. For the slow wave case of c/Um = 0.14, the correlation is attenuated above the leeward side while the distribution of correlation function is more elongated and also exhibits a larger vertical extent above the crest. With respect to the fast wave case of c/U_m=1.4, the distribution of the correlation function is recovered in a manner similar to that in the flat-wall case. In this case, the maximum correlation coefficient exhibits only slight differences at different wave phases while the vertical distribution of the correlation function depends on the wave phase.

关键词： direct numerical simulation(DNS) wall shear stress near-wall streamwise vortex two-point correlation

Characteristics of turbulence transport for momentum and heat in particle-laden turbulent vertical channel flows

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Acta Mechanica Sinica 2017年第5期33卷 833-845页

作者： Caixi Liu Shuai Tang Lian Shen Yuhong Dong Shanghai Institute of Applied Mathematics and Mechanics and Shanghai Key laboratory of Mechanics in Energy and Environment engineering Shanghai University department of mechanical engineering and St.anthony falls laboratory University of Minnesota

The dynamic and thermal performance of particle-laden turbulent flow is investigated via direction numerical simulation combined with the Lagrangian point-particle tracking under the condition of two-way coupling, with a focus on the contributions of particle feedback effect to momentum and heat transfer of turbulence. We take into account the effects of particles on flow drag and Nusselt number and explore the possibility of drag reduction in conjunction with heat transfer enhancement in particle-laden turbulent flows. The effects of particles on momentum and heat transfer are analyzed, and the possibility of drag reduction in conjunction with heat transfer enhancement for the prototypical case of particle-laden turbulent channel flows is addressed. We present results of turbulence modification and heat transfer in turbulent particle-laden channel flow, which shows the heat transfer reduction when large inertial particles with low specific heat capacity are added to the flow. However, we also found an enhancement of the heat transfer and a small reduction of the flow drag when particles with high specific heat capacity are involved. The present results show that particles, which are active agents, interact not only with the velocity field, but also the temperature field and can cause a dissimilarity in momentum and heat transport. This demonstrates that the possibility to increase heat transfer and suppress friction drag can be achieved with addition of particles with different thermal properties.

关键词： Direction numerical simulation (DNS) Lagrangian tracking approach Flow drag Heat transfer Particle-laden flow

Snow-powered research on utility-scale wind turbine flows

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Acta Mechanica Sinica 2020年第2期36卷 339-355页

作者： Jiarong Hong Aliza Abraham St.anthony falls laboratory University of MinnesotaMinneapolisMN 55414USA department of mechanical engineering University of MinnesotaMinneapolisMN 55455USA

This paper provides a review of the general experimental methodology of snow-powered flow visualization and super-large-scale particle image velocimetry(SLPIV),the corresponding field deployments and major scientific findings from our work on a 2.5 MW utility-scale wind turbine at the Eolos field *** field measurements were conducted to investigate the incoming flow in the induction zone and the near-wake flows from different *** has been shown that these snow-powered measurements can provide sufficient spatiotemporal resolution and fields of view to characterize both qualitatively and quantitatively the incoming flow,all the major coherent structures generated by the turbine(e.g.,blade,nacelle and tower vortices,etc.)as well as the development and interaction of these structures in the near *** work has further revealed several interesting behaviors of near-wake flows(e.g.,wake contraction,dynamic wake modulation,meandering and deflection of the nacelle wake,etc.),and their connections with constantly-changing inflows and turbine operation,which are uniquely associated with utility-scale *** findings have demonstrated that the near wake flows,though highly complex,can be predicted with substantial statistical confidence using supervisory control and data acquisition(SCADA)and structural response information readily available from current utility-scale *** knowledge can be potentially incorporated into wake development models and turbine controllers for wind farm optimization in the future.

关键词： Wind turbine Utility-scale Wake Snow visualization PIV

Three dimensional flow motions in the viscous sublayer

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Theoretical & Applied Mechanics Letters 2021年第2期11卷 105-109页

作者： S.Santosh Kumar Xinyi Huang Xiang Yang Jiarong Hong department of mechanical engineering University of MinnesotaMinneapolisMN55455 saint anthony falls laboratory University of MinnesotaMinneapolisMN55414 department of mechanical engineering Penn State UniversityUniversity ParkPA16802

We employ novel digital Fresnel reflection holography to capture the 3D flows within the viscous sublayerof a smooth-wall turbulent channel flow at Reτ=*** measurements reveal unsteady and diverse flow patterns in the sublayer including nearly uniform high and low speed flows and strong small-scale(onthe order of viscous wall units)spanwise meandering *** probability density functions(PDFs)ofwall shear stresses show a clear discrepancy in high stress range with those from direct numerical simu-lation(DNS),which is attributed to the unresolved streamwise and spanwise motions by ***,the PDF of Lagrangian particle accelerations yields a stretched exponential shape like that in homogenousisotropic turbulence,indicating strong intermittency in the *** find a significant fraction of highaccelerations is associated with the small-scale meandering *** study helps explain the effectof sublayer-scale roughness on reducing drag and flow separation reported in the literature.

关键词： Viscous sublayer Digital holography Meandering motions Turbulent channel flow Sublayer-scale roughness DNS

Impact of spray droplets on momentum and heat transport in a turbulent marine atmospheric boundary layer

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Theoretical & Applied Mechanics Letters 2019年第2期9卷 71-78页

作者： Ming Pan Caixi Liu Qingxiang Li Shuai Tang Lian Shen Yuhong Dong Shanghai Institute of Applied Mathematics and Mechanics Shanghai University department of mechanical engineering and St.Anthony Falls Laboratory University of Minnesota Shanghai Key laboratory of Mechanics in Energy and Environment engineering

Droplet-laden turbulent airflow(i.e. the mixture of dry air and water vapor) in the marine atmospheric boundary layer is described by an open channel flow configuration in direct numerical simulation(DNS). The dispersed phase, the spray droplets are tracked in a Lagrangian framework, and their impact on the carrier airflow is modeled with the two-way coupling between the two phases. A wide-range droplet size is typically found near the air–sea interface according to the sea spray concentration function(SSCF). The interactions of the droplets with turbulent airflow including mass, momentum, and energy exchange are investigated here. We found a balancing mechanism exists in the droplet effects on the turbulent drag coefficient, since spray droplets lead to a decreased vertical turbulent momentum transport, but also lead to an increased droplet contribution to total drag coefficient. For the heat transfer, as droplet mass loading increasing, the total Nusselt number decreases due to the depression of turbulent heat flux and enhanced negative droplet convective flux.

关键词： Direct numerical simulation Air-sea interface Sea spray Turbulent airflow

Simulation-based study of wind-wave interactions under various sea conditions

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Simulation-based study of wind-wave interactions under vario...

A quasi-coupled wind wave experimental framework for testing offshore wind turbine floating systems

第三十届全国水动力学研讨会暨第十五届全国水动力学学术会议

作者： HAO Xuan-ting LI Tian-yi CAO Tao SHEN Lian department of mechanical engineering and saint anthony falls laboratory University of Minnesota

Despite their impact on the ocean environment,key physical processes in wind-wave interactions are poorly *** a solver developed for undulatory boundaries,we perform numerical simulations of wind-wave systems under various sea conditions,including wind over monochromatic waves,early wind-wave generation,and wind over a broadband wave *** results show that the wave direction and wave age can significantly change the streamwise vorticity distribution in the wind *** wave patterns are observed in the process of wind-wave *** a broadband wave field,the wave growth rate due to wind input is found to depend on the wave steepness.

关键词： wind-wave interaction direct numerical simulation large eddy simulation phase-resolved wave simulation

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Theoretical & Applied Mechanics Letters 2021年第5期11卷 280-290页

作者： C.Feist F.Sotiropoulos M.Guala saint anthony falls laboratory College of Science and EngineeringUniversity of MinnesotaMinneapolis MN 55414USA department of mechanical and Nuclear engineering Virginia Commonwealth UniversityRichmond VA 23284-2527USA department of Civil Environmental and Geo-EngineeringCollege of Science and EngineeringUniversity of MinnesotaMinneapolis MN 55455-0116USA

Two sets of experiments in the *** falls laboratory(SAFL)wave tank facility and atmospheric wind tunnel are integrated to provide a scaled representation of a floating wind turbine under heave and pitch motions due to ocean *** quasi-coupling is established by controlling the turbine rotor speed to generate a thrust force mimicking steady or fluctuating wind gusts in the wave tank,and by using two actuators to oscillate a miniature turbine in the wind *** pitch and heave motions under varying waves are scaled down using rotor geometry and the wake meandering frequency to study the effect of the floating platform kinematics on the evolution and characteristics of the oscillating turbine *** a limited case of experimental conditions results provide a phenomenological and quantitative description of the floating-turbine system under variable waves and simulated wind ***,we demonstrate that wind gusts contribute to increase the platform pitch range,and that periodic large scale flow patches of high and low momentum flow are generated by the oscillating rotor in the turbulent boundary layer and are coherently convected through the *** mechanisms could amplify the pitch response of downwind floating turbine units within the offshore power plant,in particular if the wave and/or wind forcing frequencies happen to approach the pitch natural frequency of the floating system.

关键词： Wind power Ocean Renewable Turbulent flow