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The purpose of this paper is to present a novel method to design and manufacture rapid prototyping (RP) lightweight photopolymer‐resin models for wind‐tunnel tests. This method can ensure the structural configuration similarity considering model deformation under aerodynamic loads.

Photopolymer‐resin based on RP technique was used to fabricate DLR‐F4 models. Testing in a subsonic and transonic wind tunnel was carried out and the test results were compared to analyze performance predictions.

RP photopolymer‐resin wind‐tunnel models fabricated by the design methods yielded satisfactory aerodynamic performance. The methods can decrease the model's weight and prevent resonance occurrence among the models, wind‐tunnel, and support system, shorten the processing period, and lead to decrease in manufacturing period and cost.

Stiffness shortage of the thin components, such as wing tip, often leads to deformation occurrence under aerodynamic loads in transonic wind‐tunnel tests, which has significant influence on aerodynamic characteristics of the test models. Therefore, model deformation should be taken into account in the design process.

This design and manufacture method, aerodynamic and structural combination design and structural optimization, can obtain RP lightweight photopolymer‐resin wind‐tunnel models for satisfactory aerodynamic performance, which makes RP techniques more practical for manufacturing transonic wind‐tunnel test models, considering deformation induced by aerodynamic forces such as lift force. The methods also present an inexpensive way to test and evaluate preliminary aircraft designs, in both academia and industry.

The purpose of this paper is to introduce a novel method for developing static aeroelastic models based on rapid prototyping for wind tunnel testing.

A metal frame and resin covers are applied to a static aeroelastic wind tunnel model, which uses the difference of metal and resin to achieve desired stiffness distribution by the stiffness similarity principle. The metal frame is made by traditional machining, and resin covers are formed by stereolithgraphy. As demonstrated by wind tunnel testing and stiffness measurement, the novel method of design and fabrication of the static aeroelastic model based on stereolithgraphy is practical and feasible, and, compared with that of the traditional static elastic model, is prospective due to its lower costs and shorter period for its design and production, as well as avoiding additional stiffness caused by outer filler.

This method for developing static aeroelastic wind tunnel model with a metal frame and resin covers is feasible, especially for aeroelastic wind tunnel models with complex external aerodynamic shape, which could be accurately constructed based on rapid prototypes in a shorter time with a much lower cost. The developed static aeroelastic aircraft model with a high aspect ratio shows its stiffness distribution in agreement with the design goals, and it is kept in a good condition through the wind tunnel testing at a Mach number ranging from 0.4 to 0.65.

The contact stiffness between the metal frame and resin covers is difficult to calculate accurately even by using finite element analysis; in addition, the manufacturing errors have some effects on the stiffness distribution of aeroelastic models, especially for small-size models.

The design, fabrication and ground testing of aircraft static aeroelastic models presented here provide accurate stiffness and shape stimulation in a cheaper and sooner way compared with that of traditional aeroelastic models. The ground stiffness measurement uses the photogrammetry, which can provide quick, and precise, evaluation of the actual stiffness distribution of a static aeroelastic model. This study, therefore, expands the applications of rapid prototyping on wind tunnel model fabrication, especially for the practical static aeroelastic wind tunnel tests.

The purpose of this paper is to propose a new approach of using additively manufactured parametric models in the wind tunnel test-based aerodynamic shape optimization (ASO) framework and to present its applicability test results obtained from a realistic aircraft design problem.

For aircraft shape optimization, the following three methodologies were used. First, as a validation study, the possibility of using rapid prototyping (RP) model in the wind tunnel test was verified. Second, through the wind tunnel test-based ASO, the application and feasibility of the real fighter aircraft shape optimization were verified. A generic fighter configuration is parameterized to generate various test models using additive manufacturing. Wind tunnel tests are conducted to measure their stability criteria in high angle of attack (AOA). Finally, a computational fluid dynamics (CFD) study was performed and analysis procedures, costs and results compared to the wind tunnel test were compared and reviewed.

RP technology can significantly reduce the time and cost of generating parametric wind tunnel models and can open up new possibilities for wind tunnel tests to be used in the rigorous aerodynamic design loop. There was a slight difference between the results of the RP model and the metallic model because of rigidity and surface roughness. However, the tendency of the aerodynamic characteristics was very similarly predictable. Although there are limitations to obtaining precise aerodynamic data, it is a suitable method to be applied to comparative studies on various shapes with large geo-metric changes in the early phase of design. The CFD analysis indicates that the wind tunnel-based ASO using the RP model shows the efficiency corresponding to the CFD shape optimization.

The RP parametric models may have various assembly error sources and rigidity problems. The proposed methodology may not be suitable for collecting the accurate aerodynamic database of a final design; rather, the methodology is more suitable to screen out many configurations having fairly large shape variation in the early stage of the design process.

The wind tunnel test-based ASO can replace or supplement CFD-based ASO. In areas where CFD accuracy is low, such as high AOA flight characteristics, RP model wind tunnel-based ASO can be a research method that can secure both efficiency and accuracy advantages, providing ten times more effective in terms of cost and time. The wind tunnel test is used to obtain aerodynamic data at the final stage of shape design. It can be extended to a comparative study of several shapes in the early design phase. This procedure can be applied for both industrial level and educational aircraft design activities.

This study is the application to be applied as a parametric study on the whole aircraft, rather than using the RP model applying a simple partial control surface or configuration change of a part of the wing. The possibility of using the RP model was confirmed by comparing and verifying each other in a medium-sized wind tunnel using a relatively large RP model and a metallic model. It was verified that it can be applied in the shape design process, not the shape verification in the traditional design procedure, and a comparison with the CFD method was also performed. With further development and validation efforts, the new design framework may become an industrial standard for future aircraft development.

The purpose of this paper is to present the benefits offered by rapid prototyping (RP) models for wind‐tunnel testing as part of fourth‐year aerospace engineering student projects. Ways of overcoming some of the difficulties associated with the 3D printing technology are also discussed.

Polymer‐based RP was used to fabricate two‐aircraft models, which included stiffening metallic inserts. Testing in a subsonic‐wind tunnel was carried out and the results compared to analytic performance predictions.

Low‐cost rapid prototypes of wind‐tunnel models yielded satisfactory aerodynamic performance. The savings in acquisition cost and time allowed incorporating actual testing in the aircraft design process within the framework of a tight academic budget and schedule.

Conducting real‐wind‐tunnel testing contributes significantly to the educational experience of students; however, it had rarely been carried out when metal model fabrication was the only option. In contrast, RP facilitates an enhanced and more realistic learning experience by offering a quick and affordable means of model manufacturing.

Simple methods of reinforcing polymer‐based models were incorporated, thus presenting an inexpensive way to test and evaluate preliminary aircraft designs, in both academia and industry.

In view of the strength and stiffness deficiencies of current photopolymer resin models under high aerodynamic loads, the purpose of this paper is to introduce a preliminary design and manufacturing technique for hybrid lightweight high‐speed wind‐tunnel models with internal metal frame and surface photopolymer resin based on rapid prototyping (RP).

Internal metal frame structure was designed to be of regular configurations that can be conveniently fabricated by conventionally mechanical manufacturing methods. Outer resin components were designed to meet configuration fidelity and surface quality, which were fabricated by RP apparatus. Combination of aerodynamics and structure was utilized to accomplish structural design, strength and stiffness calibration and vibration analysis. Structural design optimization and manufacturing method of the validated hybrid AGARD‐B models were studied by analysis of manufacturing precision, surface quality processing and mechanical capability.

The method with internal metal frame and outer resin has dramatically improved the overall strength and stiffness of RP parts of the hybrid AGARD‐B model, and it is suitable to construct the high‐speed wind‐tunnel models with complex internal structure. The method could decrease the model's weight and prevent resonance occurrence among the models, wind‐tunnel and support system, and shorten processing period, and also it leads to decrease in manufacturing period and cost.

Stiffness of thin components for outer resin configuration is somewhat poor under high aerodynamic loads in a high‐speed wind‐tunnel test, and the effect of deformation of the components on the experimental results should be taken into account.

This method can enhance the versatility of using RP technique in the fabrication of high‐speed wind‐tunnel models, especially for experimental models with complex structure. Aerodynamic and structural combination design and structural optimization for hybrid models make RP techniques more practical for manufacturing high‐speed wind‐tunnel models.

The purpose of this paper is to find the optimum design of diffuser of supersonic wind tunnel in order to access the minimum overall pressure drop in wind tunnel, using evolutionary algorithm.

The authors developed a genetic algorithm (GA) code to calculate the shape of a diffuser with flexible walls in order to have the maximum pressure recovery. The two-dimensional turbulent and compressible flow was analyzed numerically using shear-stress transport and Advection Upstream Splitting Method (AUSM)+ turbulence models and its optimization with GA.

The results of this study indicate that elitist GA promises a powerful method for optimization of the wind tunnel diffuser. Separation zone is reduced by 22.2 percent at the convergent part of diffuser and 56 percent at the divergent part of diffuser. The efficiency of new optimized wind tunnel diffuser increased by 83 percent in comparison to the sample of supersonic wind tunnel.

It has been observed that AUSM+ method and shape design optimization using GA are robust and efficient technique to optimize wind tunnel diffuser.

For faster new product introduction aerospace companies are interested in reducing the time it takes to make wind tunnel models. The increased capabilities of rapid prototyping technologies has made them attractive for this purpose. A study was done of rapid prototyping technologies and their ability to make components for wind tunnel models in a timely and cost effective manner. Components and corresponding fabrication technologies were put into three categories: non‐structurally loaded, lightly loaded and highly loaded according to the stress endured during wind tunnel tests. Rapid prototyping technologies were found capable for non‐structurally loaded parts, but numerically controlled machining was still best for any part enduring significant loads.

The purpose of this paper is to understand the natural wind field characteristics of the tunnel entrance section and analyzing the aerodynamic performance of high-speed railway trains (HSRTs) under natural winds.

Three typical tunnel entrance section sites, namely, tunnel–bridge in a dry canyon (TBDC), tunnel–bridge in a river canyon (TBRC) and tunnel–flat ground (TF), are selected to conduct a continuous wind field measurement. Based on the measured wind characteristics, the natural winds of the TBDC and TF sites are reconstituted and imported into the two corresponding full-scale computational fluid dynamics models. The aerodynamic loads of the HSRT running on TBDC and TF with reconstituted winds are simply analyzed.

The von Kármán spectrum can be used to describe the wind field at the tunnel entrance section. In the reconstituted natural wind condition, a time-varying feature of wind speed distribution and leeward side vortex around the HSRT caused by the wind speed fluctuation is found. The fluctuating amplitude of aerodynamic loads at the TBDC infrastructure is up to 97.9% larger than that at the TF infrastructure.

The natural wind characteristics at tunnel entrance sections on the high-speed railway are first measured and analyzed. A numerical reconstitution scheme considering the temporal and spatial variation of natural wind speed is proposed and verified based on field measurement results. The aerodynamic performance of an HSRT under reconstituted natural winds is first investigated.

This paper aims to propose a dedicated measurement methodology able to simultaneously determine the stability derivative C_mα and the pitch damping coefficient sum C_mq + C_mα in a wind tunnel using a single and almost non-intrusive metrological setup called MiRo.

To assess the MiRo method’s reliability, repeatability and accuracy, the measurements obtained with this technique are compared to other sources like aerodynamic balance measurements, alternative wind tunnel measurements, Ludwieg tube measurements, free-flight measurements and computational fluid dynamics (CFD) simulations. Two different numerical approaches are compared and used to validate the MiRo method. The first numerical method forces the projectile to describe a pure oscillation motion with small amplitude along the pitch axis during a rectilinear flight, whereas the second numerical approach couples the one degrees of freedom simulation motion equations with CFD methods.

MiRo, a novel and almost non-intrusive technique for dynamic wind tunnel measurements, has been validated by comparison with five other experimental and numerical methodologies. Despite two completely different approaches, both numerical methods give almost identical results and show that the holding system has nearly no impact on the dynamic aerodynamic coefficients. Therefore, it could be assessed that the attitude of MiRo model in the wind tunnel is very close to the free-flight one.

The MiRo method allows studying the attitude of a projectile in a wind tunnel with the least possible impact on the flow around a model.

The purpose of this paper is to use a computational technique to simulate the flow in a two-dimensional (2D) wind tunnel where the effect of the solid walls facing the model has been addressed using a porous geometry so that interference arriving at the solid walls are duly damped and a flow suction procedure has been adopted at the side wall to minimize the span-wise effect of the growing side wall boundary layer.

A CFD procedure based on discretization of the Navier–Stokes equations has been used to model the flow in a rectangular volume with appropriate treatment for solid walls of the confined volume in which the model is placed. The rectangular volume was configured by stacking O-Grid sections in a span-wise direction using geometric growth from the wall. A porous wall condition has been adapted to counter the wall interference signatures and a separate suction procedure has been implemented for reducing the side wall boundary layer effects.

It has been shown that through such corrective measures, the flow in a wind tunnel can be adequately simulated using computational modeling. Computed results were compared against experimental measurements obtained from IAR (Institute for Aerospace, Canada) and NAL (National Aeronautical Laboratory, Japan) to show that indeed appropriate corrective means may be adapted to reduce the interference effects.

The solutions seemed to converge a lot better using relatively coarser grids which placed the shock locations closer to the experimental values. The finer grids were more stiff to converge and resulted in reversed flow with the two equation k-w model in the region where the intention was to draw out the fluid to thin down the boundary layer. The one equation Spalart–Allmaras model gave better result when porosity and wall suction routines were implemented.

This method could be used by industry to point check the results against certain demanding flow conditions and then used for more routine parametric studies at other conditions. The method would prove to be efficient and economical during early design stages of a configuration.

The method makes use of an O-grid to represent the confined test section and its dual treatment of wall interference and blockage effects through simultaneous application of porosity and boundary layer suction is believed to be quite original.