When a ship moves in an oblique flow,its hydrodynamic loads and wake characteristics vary substantially from those in straight-ahead motion.This dissimilarity can be even more complex when the ship operates in a seawa...When a ship moves in an oblique flow,its hydrodynamic loads and wake characteristics vary substantially from those in straight-ahead motion.This dissimilarity can be even more complex when the ship operates in a seaway of shallow water.In this paper,a numerical analysis of the shallow-water effect on the hydrodynamic forces and wake characteristics of an international ship model,KVLCC2,in oblique flows is conducted.Numerical simulations are performed based on the Reynolds Averaged NavierStokes equation in conjunction with the shear stress transport(SST)k-ωturbulence model.Four relative water depths(h=1.2T,1.5T,3.0T,and 24T;T is the ship draft)and five different drift angles(β=0°,5°,10°,15°,and 20°)are considered.Results reveal the following:i)The shallow-water effect is strong and leads to nonlinear increases in the longitudinal force regardless of drift angles and on the transverse force and yaw moment whenever the drift angle increases.ii)In shallow water,the mean wake fraction is sensitive to the drift angle,and the strength of the aft-body vortex on the leeward side increases.展开更多
Duo to fluctuations in atmospheric turbulence and yaw control strategies,wind turbines are often in a yaw state.To predict the far wake velocity field of wind turbines quickly and accurately,a wake velocity model was ...Duo to fluctuations in atmospheric turbulence and yaw control strategies,wind turbines are often in a yaw state.To predict the far wake velocity field of wind turbines quickly and accurately,a wake velocity model was derived based on the method of momentum conservation considering the wake steering of the wind turbine under yaw conditions.To consider the shear effect of the vertical incoming wind direction,a two-dimensional Gaussian distribution function was introduced to model the velocity loss at different axial positions in the far wake region based on the assumption of nonlinear wake expansion.This work also developed a“prediction-correction”method to solve the wake velocity field,and the accuracy of the model results was verified in wake experiments on the Garrad Hassan wind turbine.Moreover,a 33-kW two-blade horizontal axis wind turbine was simulated using this method,and the results were compared with the classical wake model under the same parameters and the computational fluid dynamics(CFD)simulation results.The results show that the nonlinear wake model well reflected the influence of incoming flow shear and yaw wake steering in the wake velocity field.Finally,computation of the wake flow for the Horns Rev offshore wind farm with 80 wind turbines showed an error within 8%compared to the experimental values.The established wake model is less computationally intensive than other methods,has a faster calculation speed,and can be used for engineering calculations of the wake velocity in the far wakefield of wind turbines.展开更多
Large atmospheric boundary layer fluctuations and smaller turbine-scale vorticity dynamics are separately hypothesized to initiate the wind turbine wake meandering phenomenon,a coherent,dynamic,turbine-scale oscillati...Large atmospheric boundary layer fluctuations and smaller turbine-scale vorticity dynamics are separately hypothesized to initiate the wind turbine wake meandering phenomenon,a coherent,dynamic,turbine-scale oscillation of the far wake.Triadic interactions,the mechanism of energy transfers between scales,manifest as triples of wavenumbers or frequencies and can be characterized through bispectral analyses.The bispectrum,which correlates the two frequencies to their sum,is calculated by two recently developed multi-dimensional modal decomposition methods:scale-specific energy transfer method and bispectral mode decomposition.Large-eddy simulation of a utility-scale wind turbine in an atmospheric boundary layer with a broad range of large length-scales is used to acquire instantaneous velocity snapshots.The bispectrum from both methods identifies prominent upwind and wake meandering interactions that create a broad range of energy scales including the wake meandering scale.The coherent kinetic energy associated with the interactions shows strong correlation between upwind scales and wake meandering.展开更多
WT5 'BZThis paper presents an unsteady and nonlinear wake model based on th e widely used Peters He finite state dynamic wake model with improvements. The swirl component in the tip trace plane (TTP) can be pr...WT5 'BZThis paper presents an unsteady and nonlinear wake model based on th e widely used Peters He finite state dynamic wake model with improvements. The swirl component in the tip trace plane (TTP) can be predicted, nonlinear items are added into the linear theory, and the old small angle assumption use d in matrix prediction is removed. All of these enha ncements are aimed at the low speed flight phase and formulations for the induce d velocity field just in the TTP frame are derived. The corresponding FORTRAN pr ogram is tested and optimized for the real time applications on PCs.展开更多
This paper describes an improved model of curved vortex element on the circular arc (CVEC) for rotor wake analysis.As the key of the paper,two approximate formulas are derived by the series of limited terms to replace...This paper describes an improved model of curved vortex element on the circular arc (CVEC) for rotor wake analysis.As the key of the paper,two approximate formulas are derived by the series of limited terms to replace the Legendre incomplete elliptical integrals from the Biot-Savart integration,and the analytical solution of the induced velocity for the CVEC is obtained, which is more efficient in the complex rotor free wake calculation. Furthermore,the approximate formulas with the chosen factors are selected to avoid sigularity and give finite result of the induced velocity on the Vortex line,and an equivalent viscous vortex core radius might be evaluated.As examples, the induced velocity calculations on the vortex ring and two turns of a skew vortex helix are performed, and the comparisons between the circular-arc vortex element and the conventional straightline vortex element (SLVE) are given.It is shown that this curved vortex element model is advantageous over the SLVE model and is suitable for the rotor wake analysis.展开更多
钢管塔力学性能卓越,应用广泛,但其钢管杆件长细比较大,水平放置易在低风速下发生涡激共振现象。钢管构件长期振动易使钢结构疲劳损伤甚至破坏,严重影响输电塔结构正常服役安全。针对钢管塔构件涡激振动现象开展试验研究,并提出有效的...钢管塔力学性能卓越,应用广泛,但其钢管杆件长细比较大,水平放置易在低风速下发生涡激共振现象。钢管构件长期振动易使钢结构疲劳损伤甚至破坏,严重影响输电塔结构正常服役安全。针对钢管塔构件涡激振动现象开展试验研究,并提出有效的阻尼控制方法。首先,开展了原尺输电塔钢管杆件气动效应研究。对槽型插板节点钢管弱轴向涡激振动响应及尾流展向特性进行分析。其次,引入尾流振子模型,探究了增加阻尼比对钢管杆涡振响应的理论抑制效果的提升。最后,根据理论计算结果开展调谐质量阻尼器(tuned mass damper,TMD)控制试验,通过加装TMD对钢管振动响应进行了控制,振幅最多可以下降95.8%,表明TMD可有效提高钢管塔在复杂风环境下的结构稳定性,保证钢管服役期间的安全。展开更多
目的观察全面性发育迟缓患儿实施醒脑开窍、补肾健脾养心针法治疗的效果。方法选取GDD住院患儿82例,随机分为对照组和试验组,各41例,2组各脱落3例,最终2组各纳入38例。对照组行常规康复治疗,试验组在此基础上增加实施醒脑开窍、补肾健...目的观察全面性发育迟缓患儿实施醒脑开窍、补肾健脾养心针法治疗的效果。方法选取GDD住院患儿82例,随机分为对照组和试验组,各41例,2组各脱落3例,最终2组各纳入38例。对照组行常规康复治疗,试验组在此基础上增加实施醒脑开窍、补肾健脾养心针法。对2组患儿治疗前后应用Gesell发育量表、Peabody 2运动发育评估量表、婴儿-初中生社会生活能力量表进行疗效评估。结果治疗后2组精细运动、大运动、语言、适应性、个人-社交发育商(developmental quotient,DQ)及精细运动商(fine motor quotient,FMQ)、粗大运动商(gross motor quotient,GMQ)、总体运动商(total motor quotient,TMQ)和自我管理、独立生活、作业操作、参加集体活动、运动、交往评分均较治疗前提高(P<0.05),试验组大运动、语言、适应性、个人-社交DQ及FMQ、GMQ、TMQ和自我管理、独立生活、作业操作、运动评分较对照组更高(P<0.05),而2组精细运动DQ和参加集体活动、交往评分比较不存在统计学差异(P>0.05)。结论醒脑开窍、补肾健脾养心针法可改善GDD患儿智力发育、运动功能及社会生活能力。展开更多
The basal ganglia(BG) act as a cohesive functional unit that regulates motor function,habit formation,and reward/addictive behaviors. However,it is still not well understood how the BG maintains wakefulness and suppre...The basal ganglia(BG) act as a cohesive functional unit that regulates motor function,habit formation,and reward/addictive behaviors. However,it is still not well understood how the BG maintains wakefulness and suppresses sleep to achieve al these fundamental functions until genetical y engineered systems developed these years. Significant research efforts have recently been directed at developing genetic-molecular tools to achieve reversible and cell-type specific in vivo silencing or activation of neurons in behaving animals. Optogenetic tools can be used both to specifically activate or inhibit neurons of interest and identify functional synaptic connectivity between specific neuronal populations,both in vivo and in brain slices. Another recently developed system by Roth and colleagues permits the selective and ″remote″ manipulation(activation and silencing) of neuronal activity via all 3 major GPCR signaling pathways(G_i,G_s and G_q). These so-called ″ designer receptors exclusively activated by designer drugs″(DREADD) involve mutant GPCRs that do not respond to their endogenous ligands but are responsive to otherwise inert biological compounds. Recently,we demonstrated the essential roles and the neural pathways of the neurons expressing adenosine A_(2A) receptors or dopamine D_1 receptors in the BG for sleep-wake regulation using the genetically engineered systems including optogenetics and DREADD. We proposed a plausible model in which the caudate-putamen and the nucleus accumbens integrates behavioral processes with sleep/wakefulness through adenosine and dopamine receptors.展开更多
基金supported by the National Key R&D Plan Project(No.2019YFD0901003)。
文摘When a ship moves in an oblique flow,its hydrodynamic loads and wake characteristics vary substantially from those in straight-ahead motion.This dissimilarity can be even more complex when the ship operates in a seaway of shallow water.In this paper,a numerical analysis of the shallow-water effect on the hydrodynamic forces and wake characteristics of an international ship model,KVLCC2,in oblique flows is conducted.Numerical simulations are performed based on the Reynolds Averaged NavierStokes equation in conjunction with the shear stress transport(SST)k-ωturbulence model.Four relative water depths(h=1.2T,1.5T,3.0T,and 24T;T is the ship draft)and five different drift angles(β=0°,5°,10°,15°,and 20°)are considered.Results reveal the following:i)The shallow-water effect is strong and leads to nonlinear increases in the longitudinal force regardless of drift angles and on the transverse force and yaw moment whenever the drift angle increases.ii)In shallow water,the mean wake fraction is sensitive to the drift angle,and the strength of the aft-body vortex on the leeward side increases.
基金Supported by the Key R&D Program of Shandong Province,China(No.2023ZLYS01)the National Key R&D Program of China(No.2022YFC3104200)+2 种基金the National Natural Science Foundation of China(No.12302301)the China Postdoctoral Science Foundation(No.2023M742229)the Zhejiang Provincial Natural Science Foundation(ZJNSF)(No.LQ22F030002)。
文摘Duo to fluctuations in atmospheric turbulence and yaw control strategies,wind turbines are often in a yaw state.To predict the far wake velocity field of wind turbines quickly and accurately,a wake velocity model was derived based on the method of momentum conservation considering the wake steering of the wind turbine under yaw conditions.To consider the shear effect of the vertical incoming wind direction,a two-dimensional Gaussian distribution function was introduced to model the velocity loss at different axial positions in the far wake region based on the assumption of nonlinear wake expansion.This work also developed a“prediction-correction”method to solve the wake velocity field,and the accuracy of the model results was verified in wake experiments on the Garrad Hassan wind turbine.Moreover,a 33-kW two-blade horizontal axis wind turbine was simulated using this method,and the results were compared with the classical wake model under the same parameters and the computational fluid dynamics(CFD)simulation results.The results show that the nonlinear wake model well reflected the influence of incoming flow shear and yaw wake steering in the wake velocity field.Finally,computation of the wake flow for the Horns Rev offshore wind farm with 80 wind turbines showed an error within 8%compared to the experimental values.The established wake model is less computationally intensive than other methods,has a faster calculation speed,and can be used for engineering calculations of the wake velocity in the far wakefield of wind turbines.
基金supported by the National Science Foundation(Grant No.21-36371)supported by the National Science Foundation(Grant Nos.21-38259,21-38286,21-38307,21-37603,and 21-38296)。
文摘Large atmospheric boundary layer fluctuations and smaller turbine-scale vorticity dynamics are separately hypothesized to initiate the wind turbine wake meandering phenomenon,a coherent,dynamic,turbine-scale oscillation of the far wake.Triadic interactions,the mechanism of energy transfers between scales,manifest as triples of wavenumbers or frequencies and can be characterized through bispectral analyses.The bispectrum,which correlates the two frequencies to their sum,is calculated by two recently developed multi-dimensional modal decomposition methods:scale-specific energy transfer method and bispectral mode decomposition.Large-eddy simulation of a utility-scale wind turbine in an atmospheric boundary layer with a broad range of large length-scales is used to acquire instantaneous velocity snapshots.The bispectrum from both methods identifies prominent upwind and wake meandering interactions that create a broad range of energy scales including the wake meandering scale.The coherent kinetic energy associated with the interactions shows strong correlation between upwind scales and wake meandering.
文摘WT5 'BZThis paper presents an unsteady and nonlinear wake model based on th e widely used Peters He finite state dynamic wake model with improvements. The swirl component in the tip trace plane (TTP) can be predicted, nonlinear items are added into the linear theory, and the old small angle assumption use d in matrix prediction is removed. All of these enha ncements are aimed at the low speed flight phase and formulations for the induce d velocity field just in the TTP frame are derived. The corresponding FORTRAN pr ogram is tested and optimized for the real time applications on PCs.
文摘This paper describes an improved model of curved vortex element on the circular arc (CVEC) for rotor wake analysis.As the key of the paper,two approximate formulas are derived by the series of limited terms to replace the Legendre incomplete elliptical integrals from the Biot-Savart integration,and the analytical solution of the induced velocity for the CVEC is obtained, which is more efficient in the complex rotor free wake calculation. Furthermore,the approximate formulas with the chosen factors are selected to avoid sigularity and give finite result of the induced velocity on the Vortex line,and an equivalent viscous vortex core radius might be evaluated.As examples, the induced velocity calculations on the vortex ring and two turns of a skew vortex helix are performed, and the comparisons between the circular-arc vortex element and the conventional straightline vortex element (SLVE) are given.It is shown that this curved vortex element model is advantageous over the SLVE model and is suitable for the rotor wake analysis.
文摘钢管塔力学性能卓越,应用广泛,但其钢管杆件长细比较大,水平放置易在低风速下发生涡激共振现象。钢管构件长期振动易使钢结构疲劳损伤甚至破坏,严重影响输电塔结构正常服役安全。针对钢管塔构件涡激振动现象开展试验研究,并提出有效的阻尼控制方法。首先,开展了原尺输电塔钢管杆件气动效应研究。对槽型插板节点钢管弱轴向涡激振动响应及尾流展向特性进行分析。其次,引入尾流振子模型,探究了增加阻尼比对钢管杆涡振响应的理论抑制效果的提升。最后,根据理论计算结果开展调谐质量阻尼器(tuned mass damper,TMD)控制试验,通过加装TMD对钢管振动响应进行了控制,振幅最多可以下降95.8%,表明TMD可有效提高钢管塔在复杂风环境下的结构稳定性,保证钢管服役期间的安全。
文摘目的观察全面性发育迟缓患儿实施醒脑开窍、补肾健脾养心针法治疗的效果。方法选取GDD住院患儿82例,随机分为对照组和试验组,各41例,2组各脱落3例,最终2组各纳入38例。对照组行常规康复治疗,试验组在此基础上增加实施醒脑开窍、补肾健脾养心针法。对2组患儿治疗前后应用Gesell发育量表、Peabody 2运动发育评估量表、婴儿-初中生社会生活能力量表进行疗效评估。结果治疗后2组精细运动、大运动、语言、适应性、个人-社交发育商(developmental quotient,DQ)及精细运动商(fine motor quotient,FMQ)、粗大运动商(gross motor quotient,GMQ)、总体运动商(total motor quotient,TMQ)和自我管理、独立生活、作业操作、参加集体活动、运动、交往评分均较治疗前提高(P<0.05),试验组大运动、语言、适应性、个人-社交DQ及FMQ、GMQ、TMQ和自我管理、独立生活、作业操作、运动评分较对照组更高(P<0.05),而2组精细运动DQ和参加集体活动、交往评分比较不存在统计学差异(P>0.05)。结论醒脑开窍、补肾健脾养心针法可改善GDD患儿智力发育、运动功能及社会生活能力。
文摘The basal ganglia(BG) act as a cohesive functional unit that regulates motor function,habit formation,and reward/addictive behaviors. However,it is still not well understood how the BG maintains wakefulness and suppresses sleep to achieve al these fundamental functions until genetical y engineered systems developed these years. Significant research efforts have recently been directed at developing genetic-molecular tools to achieve reversible and cell-type specific in vivo silencing or activation of neurons in behaving animals. Optogenetic tools can be used both to specifically activate or inhibit neurons of interest and identify functional synaptic connectivity between specific neuronal populations,both in vivo and in brain slices. Another recently developed system by Roth and colleagues permits the selective and ″remote″ manipulation(activation and silencing) of neuronal activity via all 3 major GPCR signaling pathways(G_i,G_s and G_q). These so-called ″ designer receptors exclusively activated by designer drugs″(DREADD) involve mutant GPCRs that do not respond to their endogenous ligands but are responsive to otherwise inert biological compounds. Recently,we demonstrated the essential roles and the neural pathways of the neurons expressing adenosine A_(2A) receptors or dopamine D_1 receptors in the BG for sleep-wake regulation using the genetically engineered systems including optogenetics and DREADD. We proposed a plausible model in which the caudate-putamen and the nucleus accumbens integrates behavioral processes with sleep/wakefulness through adenosine and dopamine receptors.
