Kazuhiro Kusunose

Extension of Wake-Survey Analysis Method to Cover Compressible Flows

We summarize the work accomplished over the last several years on wake-survey analysis method developments at Boeing. Betz and Maskells lift-and-drag equations are extended to cover compressible flows. The small perturbation method is employed to expand the general lift-and-drag equations in the momentum integral forms, assuming downstream states that differ only slightly from the state of approach. Introducing new, simpler, and cleaner expansion procedures, it is proven that both the lift and drag of an airplane model can be predicted accurately by simply measuring flow variables inside of the model wake region. This result enables the practical application of quantitative wake surveys for accurate lift-and-drag predictions of airplane models. To demonstrate the current lift-and-drag prediction capabilities, some wake-survey analysis results from previously published data are recalculated. Because wake surveys are not needed outside of the model wake region, one complete wake survey analysis for a nonpowered engine case, including data acquisitions and reductions, can now be finished in approximately 10-15 min

Experimental Investigation of Vortex Generator Effect on Two- and Three-Dimensional NASA Common Research Models

Aerodynamic characteristics of twoand three-dimensional NASA common research model (2D-CRM and 3D-CRM) with co-rotating vortex generators (VGs) were investigated to clarify the influence of the three-dimensionality of the wings on the VGs effect. The base height of the VGs was 1.5 times of the boundary layer thickness at the VGs location. The direction of the VGs on the 3D-CRM was toe-out which meant the leading edge of the VGs turned to the wing tip. The Mach numbers in the 2Dand 3D-CRM experiment were 0.74 and 0.85 considering the sweepback angle of the 3D-CRM. The lift coefficient and the oil flow visualization showed that the effect of the VGs on the 3D-CRM was much larger than that on the 2D-CRM. From the comparison between the experiments and the CFD results, we concluded that the difference between 2Dand 3D-CRM was mainly caused by the crossflow due to the swept wing. The cross-flow enhances the effect of the co-rotating toe-out VGs on the swept wings. The installation drag of VGs was also investigated for the 3D-CRM and validated an empirical method to estimate the installation drag. At CL conditions below the design CL = 0.5, the VGs increased the total drag as expected, while at CL conditions above the design CL, the VGs decreased the total drag because the VGs suppressed the separation and the effect exceeded the installation drag of the VGs.

Vortex Generator Installation Drag on an Airplane Near Its Cruise Condition

A method is discussed for predicting the drag increment caused by the installation of a blade-type vortex generator (VG) on a transonic-transport airplane. The original Nash and Bradshaw magnie cation concept of roughness drag is extended to cover compressible e ows and then is applied to VG blades to estimate the VG installation drag on an airplane. Thedrag of a VG blade placed on a wing will beamplie ed dueto thegrowth of the boundary layerwith distance along thewing surface. Nash and Bradshaw showed that thedegree of magnie cation cannot be approximated simply by the ratio of local to freestream dynamic pressure ( q effect). To demonstrate the magnie cation effects, some VG installation drag analyses for transonic-transport airplane models are performed using the new magnie cation factor formula. It can be seen that the agreement between these predicted drag increments and the wind-tunnel test results is good, but the drag increment based on the q effect is seriously underestimated.

Wave drag extraction from profile drag based on a wake-integral method

This study targets the extraction of the wave drag acting on a model at transonic speeds from the flow variables measured at a wake survey station. In order to accomplish this extraction, it is necessary to determine the contribution of the shock wave to the model wake. Separating the shock wake portion from the model wake is possible by recognizing two distinct sources of entropy production existing within the flow field. The first source results from fluid particles flowing through viscous (rotational) layers (e.g. boundary layers along the body surface and wakes). The second one results from fluid particles flowing through shock waves. Because a normal (or weak curved) shock does not generate vorticity in the flow field, the shock wake and the vertical wake portions of the model wake are separable by checking the vorticity level in the wake. Once they are separated, wave drag can be extracted from the profile drag. A simple wave drag extraction method, which does not require a complex and cumbersome manipulation of the total pressure profile, is discussed here. To demonstrate its wave drag prediction capability, typical transonic wake survey results for a transonic transport configuration are presented.

Effect of Vortex Generators on Transonic Swept Wings

This paper examines the effects of corotating blade-type vortex generators on transonic sweptback wings using computational fluid dynamics studies. Infinite-span (two-dimensional) swept wings are first considered to understand the basic physics of vortex generators. Sweep angles are given virtually to the wings by changing the freestream direction. Vortex generators are placed on the wings, and the visualized interactions of their tip vortices with the boundary layer reveal the relationship between the effect of the vortex generators and the wing sweep angle. The physics of vortex-generator tip vortices are then described to explain how vortex generators on swept wings efficiently suppress shock-induced separation by mixing boundary layers. It is also shown that the vortex-generator angle of incidence to the local flow can slightly improve the effect of the vortex generators but that wing sweep angle has a greater influence on their effect. Based on the discussion of infinite-span wings, the computational...

Aerodynamic/Sonic Boom Performance Evaluation of Innovative Supersonic Transport Configurations

In this research, biplane wing/twin-body fuselage innovative configurations are discussed as a next-generation supersonic transport candidate. Those aerodynamic performance as well as sonic boom performance are investigated by using numerical approaches. The aerodynamic performance is evaluated by inviscid compressible Euler equations using an unstructured mesh finite-volume method, and then the sonic boom performance is evaluated by an augmented Burgers equation. Thanks to the successful interactions of shock waves between the biplane wing as well as the twin-body fuselages, remarkable drag reduction and better sonic boom performance have been realized simultaneously at our design Mach number of 1.7. The superiority of the proposed supersonic transport configuration over conventional configurations is clearly demonstrated.

Low-Boom/Low-Drag Design Optimization of Innovative Supersonic Transport Configuration

The generation of shock waves is inevitable in supersonic cruise, which results in the generation of wave drag as well as sonic boom on the ground. Some innovative concepts such as the supersonic b...