Water inflow into mountain tunnels exhibits high variability and nonlinear seepage behavior,leading to significant prediction inaccuracies and poor pattern recognition when conventional analytical methods are applied....Water inflow into mountain tunnels exhibits high variability and nonlinear seepage behavior,leading to significant prediction inaccuracies and poor pattern recognition when conventional analytical methods are applied.This study proposes a dynamic water inflow prediction method specifically designed for mountain tunnels.The method is based on groundwater dynamics theory,employing nonDarcian law as the governing equation and deriving analytical solutions applicable to both confined and phreatic aquifer conditions.The method incorporates spatiotemporal variations along the tunnel alignment,enabling both short-term and long-term dynamic predictions of water inflow.The study examines the nonlinear characteristics of the seepage field during tunnel water inrush.The research findings indicate that the predictive results are consistent with the hypothesized two-stage water inflow pattern,with relative errors for key parameters,such as maximum water inflow,normal water inflow,and duration of water inflow,remaining within 10%.The magnitude of water inflow is positively correlated with the permeability coefficient,head height;it is negatively correlated with the axial distance to the tunnel face and the non-Darcian influence coefficient.Both water inflow and water pressure are subject to non-Darcian effects within a defined influence zone extending approximately 1.3 times the tunnel diameter.Comparisons with established predictive methods,numerical simulations,and data from existing tunnel projects confirm the effectiveness of the proposed method.Moreover,the method was successfully applied to a mountain tunnel in the Tibet Plateau region in southwestern China,where it achieved prediction errors within 3%to 8%,demonstrating high reliability.展开更多
To improve the rotor off-axis response prediction, aerodynamic models must include the wake distortion effects of the maneuvering rotor. And the crux of the matter is to obtain a precise wake curvature parameter KR. A...To improve the rotor off-axis response prediction, aerodynamic models must include the wake distortion effects of the maneuvering rotor. And the crux of the matter is to obtain a precise wake curvature parameter KR. A Peters-He finite-state wake model is improved to incorporate the operating-state-dependent KR to embody maneuver-induced effects. The curvature parameter KR varies with rotor forward speed, thrust and maneuvering angular rate according to a smoking experiment. Moreover, aerodynamic force/moment experiment indicates that after a quasi-step angular input, both on-axis and off-axis rotor responses show that an overshoot and its amplitude increases with the pitching rate. The comparison between theoretical and experimental results shows that the operating-state-accurate curvature parameter must be adopted to obtain accurate aerodynamic forces/moments, especially for the off-axis response. Additionally, combined with a dynamic wake distortion model, the obtained correlation agrees well with experimental data.展开更多
The muhi-body analysis of the aeroelastic stability of the tiltrotor aircraft is presented. Muhi-body dynamic differential equations are combined with the equations of the unsteady dynamic inflow model to establish th...The muhi-body analysis of the aeroelastic stability of the tiltrotor aircraft is presented. Muhi-body dynamic differential equations are combined with the equations of the unsteady dynamic inflow model to establish the complete unsteadily aeroelastic coupling analytical model of the tiltrotor. The stability of the tiltrotor in the helicopter mode is analyzed aiming at a semi span soft-inplane tihrotor model with an elastic wing. Parametric effects of the lag stiffness of blades and the flight speed are analyzed. Numerical simulations demonstrate that the multibody analytical model can analyze the aeroelastic stability of the tiltrotor aircraft in the helicopter mode.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
基金the financial support provided by the Key Laboratory of Urban Underground Engineering of Ministry of Education,Beijing Jiaotong University(Grant Nos.TUL2024-05)。
文摘Water inflow into mountain tunnels exhibits high variability and nonlinear seepage behavior,leading to significant prediction inaccuracies and poor pattern recognition when conventional analytical methods are applied.This study proposes a dynamic water inflow prediction method specifically designed for mountain tunnels.The method is based on groundwater dynamics theory,employing nonDarcian law as the governing equation and deriving analytical solutions applicable to both confined and phreatic aquifer conditions.The method incorporates spatiotemporal variations along the tunnel alignment,enabling both short-term and long-term dynamic predictions of water inflow.The study examines the nonlinear characteristics of the seepage field during tunnel water inrush.The research findings indicate that the predictive results are consistent with the hypothesized two-stage water inflow pattern,with relative errors for key parameters,such as maximum water inflow,normal water inflow,and duration of water inflow,remaining within 10%.The magnitude of water inflow is positively correlated with the permeability coefficient,head height;it is negatively correlated with the axial distance to the tunnel face and the non-Darcian influence coefficient.Both water inflow and water pressure are subject to non-Darcian effects within a defined influence zone extending approximately 1.3 times the tunnel diameter.Comparisons with established predictive methods,numerical simulations,and data from existing tunnel projects confirm the effectiveness of the proposed method.Moreover,the method was successfully applied to a mountain tunnel in the Tibet Plateau region in southwestern China,where it achieved prediction errors within 3%to 8%,demonstrating high reliability.
文摘To improve the rotor off-axis response prediction, aerodynamic models must include the wake distortion effects of the maneuvering rotor. And the crux of the matter is to obtain a precise wake curvature parameter KR. A Peters-He finite-state wake model is improved to incorporate the operating-state-dependent KR to embody maneuver-induced effects. The curvature parameter KR varies with rotor forward speed, thrust and maneuvering angular rate according to a smoking experiment. Moreover, aerodynamic force/moment experiment indicates that after a quasi-step angular input, both on-axis and off-axis rotor responses show that an overshoot and its amplitude increases with the pitching rate. The comparison between theoretical and experimental results shows that the operating-state-accurate curvature parameter must be adopted to obtain accurate aerodynamic forces/moments, especially for the off-axis response. Additionally, combined with a dynamic wake distortion model, the obtained correlation agrees well with experimental data.
文摘The muhi-body analysis of the aeroelastic stability of the tiltrotor aircraft is presented. Muhi-body dynamic differential equations are combined with the equations of the unsteady dynamic inflow model to establish the complete unsteadily aeroelastic coupling analytical model of the tiltrotor. The stability of the tiltrotor in the helicopter mode is analyzed aiming at a semi span soft-inplane tihrotor model with an elastic wing. Parametric effects of the lag stiffness of blades and the flight speed are analyzed. Numerical simulations demonstrate that the multibody analytical model can analyze the aeroelastic stability of the tiltrotor aircraft in the helicopter mode.
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.
