Influence of aerodynamic configuration of a streamline box girder on bridge flutter and vortex-induced vibration

Streamline box girders are widely applied in the design and construction of long-span bridges all over the world. In order to study the influence of modifications of aerodynamic configuration and accessory components on flutter and vortex-induced vibration （VIV）, more than 60 cases were tested through a 1：50 scale section model. The test results indicates that the aerodynamic configuration and accessory components of streamline box girders can signifi- cantly affect the wind-induced vibration of bridge, which is in good agreement with the experience of past researchers. From the tests carried out, it is observed that if the horizontal angle of the inclined web of the streamline box girder is below 16°, the critical flutter wind speed of bridge will increase remarkably, and the VIV will diminish. The test results also show that the 15° inclined web can restrain the formation of vortex near the tail, and consequently improve the performance of aerodynamic stability of long-span bridges. Finally, a new streamline box girder with 15° inclined web was presented and strongly recommended in the aerodynamic configuration design of long-span bridges.

Stealth Considerations for Aerodynamic Configurations Design of Missiles

The aerodynamic design of a strategic weapon is of interest, especially when the radar signatures are included in the conceptual design phase. The basics of stealth configurations and stealth mechanisms for missiles are reviewed. The Radar Cross Sections （RCS） of some generic missiles are predicted and compared to analyze the trade-offs involved between low RCS and aerodynamic performance. The consideration of RCS prediction in the conceptual design phase gives a quick insight into the stealth performance prior to detailed design.

Hypersonic I-shaped aerodynamic configurations

Hypersonic vehicles,which flight at Mach numbers greater than 5,will serve as a more convenient and efficient transport tool than present subsonic airplanes for long-distance journeys in future.Typically,it only takes a couple of hours from Beijing to New York at hypersonic speed.Recent interest

Aerodynamic configuration integration design of hypersonic cruise aircraft with inward-turning inlets

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.

Comparisons and applications of numerical simulation methods for predicting aerodynamic heating around complex configurations

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.

Trim Drag Prediction for Blended-Wing-Body UAV Configuration

A rapid method of the trim drag prediction for the blended-wing-body unmanned aerial vehicle(UAV)configuration is proposed.The method consists of four steps.The first step is to parameterizedly model the blended-wing-body UAV configuration;the second is to analyze the aerodynamics of the geometric model;the third is to create aerodynamic surrogate model;and the final step is to predict the trim drag using the surrogate model.Hence,a tool for trim drag prediction is developed by integration of the four steps.The impacts of the allocation of control surfaces,position of gravity center and planform parameters on the trim drag are investigated by using the tool.Results show that using the control surface in outer wing for trim has an advantage of lower trim drag,and the position of gravity center has a primary impact on the trim drag.Moreover,the planform has secondary impacts on the trim drag.

Aerodynamic stability evolution tendency of suspension bridges with spans from 1000 to 5000 m

Aerodynamic instability owing to aerostatic and flutter-related failures is a significant concern in the wind-resistant design of long-span suspension bridges.Based on the dynamic characteristics of suspension bridges with spans ranging from 888 to 1991 m,we proposed fitted equations for increasing spans and base frequencies.Finite element models of suspension bridges with increasing span from 1000 to 5000 m were constructed.The structural parameters were optimized to follow the fitted tendencies.To analyze the aerodynamic instability,streamlined single-box section(SBS),lattice truss section(LTS),narrow slotted section(NSS),and wide slotted section(WSS)were considered.We performed three-dimensional(3-D)full-mode flutter analysis and nonlinear aerostatic instability analysis.The flutter critical wind speed continuously decreases with span growth,showing an unlimited approaching phenomenon.Regarding aerostatic instability,the instability wind speed decreases with span to approximately 3000 m,and increases when the span is in the range of 3000 to 5000 m.Minimum aerostatic instability wind speed with SBS or LTS girder would be lower than observed maximal gust wind speed,indicating the probability of aerostatic instability.This study proposes that suspension bridge with span approximately 3000 m should be focused on both aerostatic instability and flutter,and more aerodynamic configuration optimistic optimizations for flutter are essential for super long-span suspension bridges with spans longer than 3000 m.

Aerodynamic Design Methodology for Blended Wing Body Transport

This paper puts forward a design idea for blended wing body（BWB）.The idea is described as that cruise point,maximum lift to drag point and pitch trim point are in the same flight attitude.According to this design idea,design objectives and constraints are defined.By applying low and high fidelity aerodynamic analysis tools,BWB aerodynamic design methodology is established by the combination of optimization design and inverse design methods.High lift to drag ratio,pitch trim and acceptable buffet margin can be achieved by this design methodology.For 300-passenger BWB configuration based on static stability design,as compared with initial configuration,the maximum lift to drag ratio and pitch trim are achieved at cruise condition,zero lift pitching moment is positive,and buffet characteristics is well.Fuel burn of 300-passenger BWB configuration is also significantly reduced as compared with conventional civil transports.Because aerodynamic design is carried out under the constraints of BWB design requirements,the design configuration fulfills the demands for interior layout and provides a solid foundation for continuous work.

Theoretical fundamentals of airframe/ propulsion integration for high-speed aircraft

Fundamental features of aerodynamic interference and integration of airframes and air-breathing jet engines for high-speed flight vehicles are studied within the framework of supersonic small perturbation theory.Both the influence of airframe components on air intakes performance and influence of intakes on vehicle external aerodynamics are under consideration.Analytical relations and specific examples show that significant favorable interference between airframes and air intakes can be realized by using preliminary compression of the flow in front of intakes at flight Mach numbers exceeding approximately 3.