Numerical simulation methods of aerodynamic heating were compared by considering the inuence of numerical schemes and turbulence models,and attempting to investigate the applicability of numerical simulation methods o...Numerical simulation methods of aerodynamic heating were compared by considering the inuence of numerical schemes and turbulence models,and attempting to investigate the applicability of numerical simulation methods on predicting heat flux in engineering applications. For some typical cases provided with detailed experimental data,four spatial schemes and four turbulence models were adopted to calculate surface heat flux. By analyzing and comparing,some inuencing regularities of numerical schemes and turbulence models on calculating heat flux had been acquired. It is clear that AUSM＋-up scheme with rapid compressibilitymodified high Reynolds number k鈥撓？model should be appropriate for calculating heat flux. The numerical methods selected as preference above were applied to calculate the heat flux of a 3-D complex geometry in high speed turbulent flows. The results indicated that numerical simulation can capture the complex flow phenomena and reveal the mechanism of aerodynamic heating. Especially,the numerical result of the heat flux at the stagnation point of the wedge was well in agreement with the prediction of Kemp鈥揜iddel formula,and the surface heat flux distribution was consistent with experiment results,which implied that numerical simulation can be introduced to predict heat flux in engineering applications.展开更多
In this work, a novel airframe/propulsion integration design method of the wing-body configuration for hypersonic cruise aircraft is proposed, where the configuration is integrated with inward-turning inlets. With the...In this work, a novel airframe/propulsion integration design method of the wing-body configuration for hypersonic cruise aircraft is proposed, where the configuration is integrated with inward-turning inlets. With the help of this method, the major design concern of balancing the aerodynamic performance against the requirements for efficient propulsion can be well addressed. A novel geometric parametrically modelling method based on a combination of patched class and shape transition（CST） and COONs surface is proposed to represent the configuration, especially a complex configuration with an irregular inlet lip shape. The modelling method enlarges the design space of components on the premise of guaranteeing the configuration integrity via special constraints imposed on the interface across adjacent surfaces. A basic flow inside a cone shaped by a dual-inflection-point generatrix is optimized to generate the inward-turning inlet with improvements of both compression efficiency and flow uniformity. The performance improvement mechanism of this basic flow is the compression velocity variation induced by the variation of the generatrix slope along the flow path. At the design point, numerical simulation results show that the lift-to-drag ratio of the configuration is as high as 5.2 and the inlet works well with a high level of compression efficiency and flow uniformity. The design result also has a good performance on off-design conditions. The achievement of all the design targets turns out that the integration design method proposed in this paper is efficient and practical.展开更多
Dragonflies are highly skilled flyers in the natural world,capable of performing flight maneuvers such as lateral flight,hovering,and backward flight—many of which are difficult for human aircraft to achieve.The exce...Dragonflies are highly skilled flyers in the natural world,capable of performing flight maneuvers such as lateral flight,hovering,and backward flight—many of which are difficult for human aircraft to achieve.The exceptional flight abilities of dragonflies are closely related to their wings.The wrinkled and venous structures on their wings provide aerodynamic advantages that flat wings with equal thickness,equal projected area,and identical shape profiles do not possess.At the same time,dragonfly wings have a certain degree of flexibility,which causes deformation under aerodynamic forces during flight.This deformation,in turn,affects the aerodynamic characteristics of the wings.To reveal the impact of the wing wrinkling and flexibility on the aerodynamic properties,this study established a three-dimensional CFD model and CSD model of the dragonfly’s wrinkled forewing based on previous measurements and research results using 3D modeling software.Modal analysis was performed to verify the model’s accuracy.Using the CFD method and a CFD/CSD bidirectional fluid-structure coupling calculation method,numerical simulations were conducted on the aerodynamic characteristics of both rigid and flexible wrinkled forewings,as well as flat forewings with equal thickness,equal projected area,and identical shape profiles during gliding flight.The results showed that the stronger leading-edge vortex and the attached vortices within the wrinkled structure improve the aerodynamic performance of the dragonfly’s forewings.Additionally,for the wrinkled forewings,the flexibility factor causes the wing veins and membrane to deform under aerodynamic loads.The pressure difference between the upper and lower surfaces of the flexible forewing is reduced compared to the rigid forewing,leading to a decrease in both lift and drag.However,in terms of the final result,the aerodynamic performance of the dragonfly’s forewings is enhanced.展开更多
A new vortex sheet model was proposed for simulating aircraft wake vortex evolution.Rather than beginning with a pair of counter-rotating cylindrical vortices as in the traditional models, a lift-drag method is used t...A new vortex sheet model was proposed for simulating aircraft wake vortex evolution.Rather than beginning with a pair of counter-rotating cylindrical vortices as in the traditional models, a lift-drag method is used to initialize a vortex sheet so that the roll-up phase is taken into account. The results of this model report a better approximation to a real situation when compared to the measurement data. The roll-up induced structures are proved to influence the far-field decay.On one hand, they lead to an early decay in the diffusion phase. On the other hand, the growth of linear instability such as elliptical instability is suppressed, resulting in a slower decay in the rapid decay phase. This work provides a simple and practicable model for simulating wake vortex evolution, which combines the roll-up process and the far-field phase in simulation. It is also proved that the roll-up phase should not be ignored when simulating the far-field evolution of an aircraft wake vortex pair, which indicates the necessity of this new model.展开更多
文摘Numerical simulation methods of aerodynamic heating were compared by considering the inuence of numerical schemes and turbulence models,and attempting to investigate the applicability of numerical simulation methods on predicting heat flux in engineering applications. For some typical cases provided with detailed experimental data,four spatial schemes and four turbulence models were adopted to calculate surface heat flux. By analyzing and comparing,some inuencing regularities of numerical schemes and turbulence models on calculating heat flux had been acquired. It is clear that AUSM＋-up scheme with rapid compressibilitymodified high Reynolds number k鈥撓？model should be appropriate for calculating heat flux. The numerical methods selected as preference above were applied to calculate the heat flux of a 3-D complex geometry in high speed turbulent flows. The results indicated that numerical simulation can capture the complex flow phenomena and reveal the mechanism of aerodynamic heating. Especially,the numerical result of the heat flux at the stagnation point of the wedge was well in agreement with the prediction of Kemp鈥揜iddel formula,and the surface heat flux distribution was consistent with experiment results,which implied that numerical simulation can be introduced to predict heat flux in engineering applications.
基金supported by the ‘‘111" Project of China (No. B17037)
文摘In this work, a novel airframe/propulsion integration design method of the wing-body configuration for hypersonic cruise aircraft is proposed, where the configuration is integrated with inward-turning inlets. With the help of this method, the major design concern of balancing the aerodynamic performance against the requirements for efficient propulsion can be well addressed. A novel geometric parametrically modelling method based on a combination of patched class and shape transition（CST） and COONs surface is proposed to represent the configuration, especially a complex configuration with an irregular inlet lip shape. The modelling method enlarges the design space of components on the premise of guaranteeing the configuration integrity via special constraints imposed on the interface across adjacent surfaces. A basic flow inside a cone shaped by a dual-inflection-point generatrix is optimized to generate the inward-turning inlet with improvements of both compression efficiency and flow uniformity. The performance improvement mechanism of this basic flow is the compression velocity variation induced by the variation of the generatrix slope along the flow path. At the design point, numerical simulation results show that the lift-to-drag ratio of the configuration is as high as 5.2 and the inlet works well with a high level of compression efficiency and flow uniformity. The design result also has a good performance on off-design conditions. The achievement of all the design targets turns out that the integration design method proposed in this paper is efficient and practical.
基金supported by the National Natural Science Foundation of China(grant number 12362026 and 11862017).
文摘Dragonflies are highly skilled flyers in the natural world,capable of performing flight maneuvers such as lateral flight,hovering,and backward flight—many of which are difficult for human aircraft to achieve.The exceptional flight abilities of dragonflies are closely related to their wings.The wrinkled and venous structures on their wings provide aerodynamic advantages that flat wings with equal thickness,equal projected area,and identical shape profiles do not possess.At the same time,dragonfly wings have a certain degree of flexibility,which causes deformation under aerodynamic forces during flight.This deformation,in turn,affects the aerodynamic characteristics of the wings.To reveal the impact of the wing wrinkling and flexibility on the aerodynamic properties,this study established a three-dimensional CFD model and CSD model of the dragonfly’s wrinkled forewing based on previous measurements and research results using 3D modeling software.Modal analysis was performed to verify the model’s accuracy.Using the CFD method and a CFD/CSD bidirectional fluid-structure coupling calculation method,numerical simulations were conducted on the aerodynamic characteristics of both rigid and flexible wrinkled forewings,as well as flat forewings with equal thickness,equal projected area,and identical shape profiles during gliding flight.The results showed that the stronger leading-edge vortex and the attached vortices within the wrinkled structure improve the aerodynamic performance of the dragonfly’s forewings.Additionally,for the wrinkled forewings,the flexibility factor causes the wing veins and membrane to deform under aerodynamic loads.The pressure difference between the upper and lower surfaces of the flexible forewing is reduced compared to the rigid forewing,leading to a decrease in both lift and drag.However,in terms of the final result,the aerodynamic performance of the dragonfly’s forewings is enhanced.
基金supported by the Boeing-COMAC Aviation Energy Conservation and Emissions Reduction Technology Center (AECER)
文摘A new vortex sheet model was proposed for simulating aircraft wake vortex evolution.Rather than beginning with a pair of counter-rotating cylindrical vortices as in the traditional models, a lift-drag method is used to initialize a vortex sheet so that the roll-up phase is taken into account. The results of this model report a better approximation to a real situation when compared to the measurement data. The roll-up induced structures are proved to influence the far-field decay.On one hand, they lead to an early decay in the diffusion phase. On the other hand, the growth of linear instability such as elliptical instability is suppressed, resulting in a slower decay in the rapid decay phase. This work provides a simple and practicable model for simulating wake vortex evolution, which combines the roll-up process and the far-field phase in simulation. It is also proved that the roll-up phase should not be ignored when simulating the far-field evolution of an aircraft wake vortex pair, which indicates the necessity of this new model.
