To achieve hydrodynamic design excellence in Autonomous Underwater Vehicles(AUVs)largely depends on the accurate prediction of lift and drag forces.The study presents Computational Fluid Dynamics(CFD)-based lift and d...To achieve hydrodynamic design excellence in Autonomous Underwater Vehicles(AUVs)largely depends on the accurate prediction of lift and drag forces.The study presents Computational Fluid Dynamics(CFD)-based lift and drag estimations of a novel torpedo-shaped flight-style AUV with bow-wings.The horizontal bow-wings are provided to accommodate the electromagnetic arrays used to perform the cable detection and tracking operations near the seabed.The hydrodynamic performance of the AUV due to addition of these horizontal bow-wings is required to be investigated,particularly at the initial design stage.Hence,CFD techniques are employed to compute the lift and drag forces observed by the flight-style AUV,maneuvering underwater at different angles of attack and varying speeds.The Reynolds-Averaged Navier-Stokes Equations(RANSE)closure is achieved by employing the modified k-ϵ model and Two-Scale Wall Function(2-SWF)approach is used for boundary layer treatment.Further,the study also highlights the unique mesh refinement and solution-adaptive meshing techniques to perform the CFD simulations in Solidworks Flow Simulation(SWFS)environment.The drag polar curve for flight-style AUV with and without bow-wings is generated using the computed lift and drag coefficients.The curve provided essential insights for achieving hydrodynamically efficient and optimized AUV design.From the drag polar curve,it is revealed that due to horizontal bow-wings,the flight-style AUV is capable to generate higher lift with less drag and thus,it gives better lift-to-drag ratio compared to the AUV without bow-wings.Moreover,simulated results of axial drag observed by the AUV have also been compared with free-running experimental results and are found in good agreement.展开更多
基金supported in part by the National Natural Science Foundation of China(Grant Nos.52131101 and 52071153)in part by Hubei Natural Science Foundation for Innovation Groups(Grant No.2021CFA026).
文摘To achieve hydrodynamic design excellence in Autonomous Underwater Vehicles(AUVs)largely depends on the accurate prediction of lift and drag forces.The study presents Computational Fluid Dynamics(CFD)-based lift and drag estimations of a novel torpedo-shaped flight-style AUV with bow-wings.The horizontal bow-wings are provided to accommodate the electromagnetic arrays used to perform the cable detection and tracking operations near the seabed.The hydrodynamic performance of the AUV due to addition of these horizontal bow-wings is required to be investigated,particularly at the initial design stage.Hence,CFD techniques are employed to compute the lift and drag forces observed by the flight-style AUV,maneuvering underwater at different angles of attack and varying speeds.The Reynolds-Averaged Navier-Stokes Equations(RANSE)closure is achieved by employing the modified k-ϵ model and Two-Scale Wall Function(2-SWF)approach is used for boundary layer treatment.Further,the study also highlights the unique mesh refinement and solution-adaptive meshing techniques to perform the CFD simulations in Solidworks Flow Simulation(SWFS)environment.The drag polar curve for flight-style AUV with and without bow-wings is generated using the computed lift and drag coefficients.The curve provided essential insights for achieving hydrodynamically efficient and optimized AUV design.From the drag polar curve,it is revealed that due to horizontal bow-wings,the flight-style AUV is capable to generate higher lift with less drag and thus,it gives better lift-to-drag ratio compared to the AUV without bow-wings.Moreover,simulated results of axial drag observed by the AUV have also been compared with free-running experimental results and are found in good agreement.
文摘目的 探讨前庭电刺激对脑卒中患者侧倾功能障碍的疗效。方法 2023年2月至10月,选取南京医科大学第一附属医院脑卒中侧倾患者30例,随机分为对照组(n=15)和试验组(n=15)。对照组接受常规康复训练与前庭伪电刺激,试验组接受常规康复训练与前庭电刺激,共2周。干预前后分别采用侧倾行为评估量表(SCP)、主观视觉垂直感知(SVV)、线段划消试验(LCT)、星消试验(SCT)、Berg平衡量表(BBS)、Holden功能性步行分级(FAC)和Barthel指数(BI)进行评估。结果 干预后,除对照组SVV方向性和稳定性以及SCT外,两组其余指标均改善(|t|> 2.461, Z> 3.000, P <0.05),且试验组SCP、SVV稳定性、LCT和FAC均优于对照组(|t|> 2.189, Z=-2.862, P <0.05);干预前后差值比较,除LCT外,试验组均大于对照组(|t|> 2.382, P <0.05)。相关性分析显示,SCP与SVV方向性和稳定性、SCT、BBS、BI评分以及FAC均相关(|r|> 0.381, P <0.05)。结论 前庭电刺激能改善脑卒中患者的侧倾、平衡、步行功能和日常生活活动能力,可能与改善空间认知功能障碍,特别是垂直感知有关。
