Blunt-body configurations are the most common geometries adopted for non-lifting re-entry vehicles.Hypersonic re-entry vehicles experience different flow regimes during flight due to drastic changes in atmospheric den...Blunt-body configurations are the most common geometries adopted for non-lifting re-entry vehicles.Hypersonic re-entry vehicles experience different flow regimes during flight due to drastic changes in atmospheric density.The conventional Navier-Stokes-Fourier equations with no-slip and no-jump boundary conditions may not provide accurate information regarding the aerothermodynamic properties of blunt-bodies in flow regimes away from the continuum.In addition,direct simulation Monte Carlo method requires significant computational resources to analyze the near-continuum flow regime.To overcome these shortcomings,the Navier-Stokes-Fourier equations with slip and jump conditions were numerically solved.A mixed-type modal discontinuous Galerkin method was employed to achieve the appropriate numerical accuracy.The computational simulations were conducted for different blunt-body configurations with varying freestream Mach and Knudsen numbers.The results show that the drag coefficient decreases with an increased Mach number,while the heat flux coefficient increases.On the other hand,both the drag and heat flux coefficients increase with a larger Knudsen number.Moreover,for an Apollo-like blunt-body configuration,as the flow enters into non-continuum regimes,there are considerable losses in the lift-to-drag ratio and stability.展开更多
Electric vertical take-off and landing(eVTOL)aircraft with multiple lifting rotors or prop-rotors have received significant attention in recent years due to their great potential for next-generation urban air mobility...Electric vertical take-off and landing(eVTOL)aircraft with multiple lifting rotors or prop-rotors have received significant attention in recent years due to their great potential for next-generation urban air mobility(UAM).Numerical models have been developed and validated as predictive tools to analyze rotor aerodynamics and wake dynamics.Among various numerical approaches,the vortex method is one of the most suitable because it can provide accurate solutions with an affordable computational cost and can represent vorticity fields downstream without numerical dissipation error.This paper presents a brief review of the progress of vortex methods,along with their principles,advantages,and shortcomings.Applications of the vortex methods for modeling the rotor aerodynamics and wake dynamics are also described.However,the vortex methods suffer from the problem that it cannot deal with the nonlinear aerodynamic characteristics associated with the viscous effects and the flow behaviors in the post-stall regime.To overcome the intrinsic drawbacks of the vortex methods,recent progress in a numerical method proposed by the authors is introduced,and model validation against experimental data is discussed in detail.The validation works show that nonlinear vortex lattice method(NVLM)coupled with vortex particle method(VPM)can predict the unsteady aerodynamic forces and complex evolution of the rotor wake.展开更多
基金the National Research Foundation of Korea funded by the Ministry of Education,Science and Technology(NRF 2017-R1A2B2007634),South Korea.
文摘Blunt-body configurations are the most common geometries adopted for non-lifting re-entry vehicles.Hypersonic re-entry vehicles experience different flow regimes during flight due to drastic changes in atmospheric density.The conventional Navier-Stokes-Fourier equations with no-slip and no-jump boundary conditions may not provide accurate information regarding the aerothermodynamic properties of blunt-bodies in flow regimes away from the continuum.In addition,direct simulation Monte Carlo method requires significant computational resources to analyze the near-continuum flow regime.To overcome these shortcomings,the Navier-Stokes-Fourier equations with slip and jump conditions were numerically solved.A mixed-type modal discontinuous Galerkin method was employed to achieve the appropriate numerical accuracy.The computational simulations were conducted for different blunt-body configurations with varying freestream Mach and Knudsen numbers.The results show that the drag coefficient decreases with an increased Mach number,while the heat flux coefficient increases.On the other hand,both the drag and heat flux coefficients increase with a larger Knudsen number.Moreover,for an Apollo-like blunt-body configuration,as the flow enters into non-continuum regimes,there are considerable losses in the lift-to-drag ratio and stability.
基金The National Research Foundation of Korea(NRF-2017-R1A5A1015311 and 2021R1C1C1010198),South Korea.Author information。
文摘Electric vertical take-off and landing(eVTOL)aircraft with multiple lifting rotors or prop-rotors have received significant attention in recent years due to their great potential for next-generation urban air mobility(UAM).Numerical models have been developed and validated as predictive tools to analyze rotor aerodynamics and wake dynamics.Among various numerical approaches,the vortex method is one of the most suitable because it can provide accurate solutions with an affordable computational cost and can represent vorticity fields downstream without numerical dissipation error.This paper presents a brief review of the progress of vortex methods,along with their principles,advantages,and shortcomings.Applications of the vortex methods for modeling the rotor aerodynamics and wake dynamics are also described.However,the vortex methods suffer from the problem that it cannot deal with the nonlinear aerodynamic characteristics associated with the viscous effects and the flow behaviors in the post-stall regime.To overcome the intrinsic drawbacks of the vortex methods,recent progress in a numerical method proposed by the authors is introduced,and model validation against experimental data is discussed in detail.The validation works show that nonlinear vortex lattice method(NVLM)coupled with vortex particle method(VPM)can predict the unsteady aerodynamic forces and complex evolution of the rotor wake.