Yoshine Ueda

Transition Measurement of Natural Laminar Flow Wing on Supersonic Experimental Airplane NEXST-1

layer. In this paper, the results of the transition measurement are introduced and compared with the numerically predicted results. The transition locations detected experimentally are in good agreement with the predicted locations, and the natural laminar flow effect is confirmed in the aerodynamic design conditions of the supersonic experimental airplane NEXST-1. Nomenclature C = local chord length CL = lift coefficient of full configuration Cp = surface pressure coefficient Cprms = fluctuation (rms) of surface static pressure of the wind tunnel E = dc output of the hot-film sensor e = ac output of the hot-film sensor H = altitude M = Mach number p = local surface pressure measured by the dynamic pressure transducer PPRT = local total pressure measured by the Preston tube Rec = Reynolds number based on the mean aerodynamic chord S = semispan length Tblow = time from the beginning of the blow in the windtunnel test Tlo = time from the liftoff in the flight test TTC = local temperature measured by the thermocouple X = chordwise position Xtip = axial length from the tip of the wind-tunnel model Y = spanwise position � = angle of attack ’ = circumferential angle from the top line on the nose 0 = fluctuation

Pressure Gradient Effects on Supersonic Transition over Axisymmetric Bodies at Incidence

Boundary-layer transition on axisymmetric bodies at a nonzero angle of attack in Mach 2 supersonic flow was investigated using experimental measurements and linear stability analysis. Transition over four axisymmetric bodies (namely, the Sears–Haack body, the semi-Sears–Haack body, the straight cone, and the flared cone) with different axial pressure gradients was measured in two different facilities with different unit Reynolds numbers. The semi-Sears–Haack body and flared cone were designed specifically to achieve a broader range of axial pressure distributions. Measurements revealed a dramatic effect of body shape on transition behavior near the leeward plane of symmetry. For a body shape with an adverse pressure gradient (that is, a flared cone), the measured transition patterns show an earlier transition location along the leeward symmetry plane in comparison with the neighboring azimuthal locations. For a nearly zero pressure gradient (that is, the straight cone), such leeward-first transition is ob...

Boundary-layer transition on an axisymmetric body at incidence at Mach 1.2

Experimental investigation of the boundary-layer transition on an axisymmetric nose model at 1- and 2-deg incidence was conducted at Mach 1.2. The configuration of the model is the forward part of a Sears-Haack body defined to have minimum wave drag caused by volume at 0-deg incidence in supersonic flow. Transition locations were obtained with small surface roughness on the order of 0.1 μ using an infrared camera. An unsteady pressure transducer was applied to investigate instability mechanisms that lead to transition. These results show that the most aft transition occurred on the leeward ray rather than on the windward rays as observed on sharp cones. Tollmien-Schlichting instability dominated the transition process on the windward ray, and crossflow instability was assumed to dominate on the side similar to the transition on the sharp cones. However, transition occurred more aft on the leeward ray than for the case of the sharp cones, and the transition front was determined by turbulent wedges formed as a consequence of the more forward transition on the side. The disturbance believed to be a traveling crossflow wave was observed at 1-deg incidence, and its measured frequency was in good agreement with the maximum amplified frequency, which was calculated using a compressible linear e N code.

Stability Characteristics of Supersonic Natural Laminar Flow Wing Design Concept

Japan Aerospace Exploration Agency (JAXA) developed a natural laminar flow (NLF) wing design concept to reduce supersonic friction drag for a future SST, and confirmed remarkable transition delay in the flight test conducted in 2005. After the test, stability characteristics on the NLF wing was numerically analyzed in detail, being compared with them on a typical non-NLF wing. The NLF wing has strongly rapid acceleration near leading edge (LE) and then gradual acceleration in chordwise region. Such a chordwise velocity distribution generates rapid decrease of maximum crossflow (C-F) velocity and change of its direction. According to linear stability theory with local parallel flow approximation, this feature contributes to suppress the growth of amplification rates based on the C-F instability.

Transition Within Leeward Plane of Axisymmetric Bodies at Incidence in Supersonic Flow

Boundary layer transition along the leeward symmetry plane of axisymmetric bodies at nonzero angle of attack in supersonic flow was investigated experimentally and numerically as part of joint research between the Japan Aerospace Exploration Agency (JAXA) and National Aeronautics and Space Administration (NASA). Transition over four axisymmetric bodies (namely, Sears-Haack body, semi-Sears-Haack body, straight cone and flared cone) with different axial pressure gradients was measured in two different facilities with different unit Reynolds numbers. The semi-Sears-Haack body and flared cone were designed at JAXA to broaden the range of axial pressure distributions. For a body shape with an adverse pressure gradient (i.e., flared cone), the experimentally measured transition patterns show an earlier transition location along the leeward symmetry plane in comparison with the neighboring azimuthal locations. For nearly zero pressure gradient (i.e., straight cone), this feature is only observed at the larger unit Reynolds number. Later transition along the leeward plane was observed for the remaining two body shapes with a favorable pressure gradient. The observed transition patterns are only partially consistent with the numerical predictions based on linear stability analysis. Additional measurements are used in conjunction with the stability computations to explore the phenomenon of leeward line transition and the underlying transition mechanism in further detail.

Evaluation of Computations and Transition Prediction Method for Aircraft High-Lift Configuration

In this study, the three-dimensional flow computations over a realistic aircraft high-lift configuration with a flow-through nacelle with a pylon mounted beneath the main wing are performed using an unstructured mesh method to investigate the influence of the boundary-layer transition on the aerodynamic forces, the capability of a transition prediction method, and the influence of brackets to support the high-lift devices. First, the influence of the boundary-layer transition on the aerodynamic forces is shown by comparison of the computational results with/without the boundary-layer transition. Then a transition prediction method based on the e N method and semi-empirical approaches is evaluated. The capability and areas to be improved are discussed. The influence of brackets to support the high-lift devices on the aerodynamic forces is also discussed. Interference of disturbed wakes by the slat supports to the flows on the main wing and flap is shown.

Compressible Boundary-Layer Transition on an Axisymmetric Body at Incidence

Experimental investigation of the boundary-layer transition on an axisymmetric nose model at 1and 2-deg incidence was conducted at Mach 1.2. The configuration of the model is the forward part of a Sears-Haack body defined to have minimum wave drag due to volume at 0-deg incidence in supersonic flow. Transition locations were obtained with small surface roughness on the order of 0.1 micron using an infrared camera. An unsteady pressure transducer was applied to investigate instability mechanisms that lead to transition. These results show that the most aft transition occurred on the leeward ray rather than on the windward rays as observed on sharp cones. Tollmien-Schlichting instability dominated the transition process on the windward ray and crossflow instability was assumed to dominate on the side similar to the transition on the sharp cones. However, transition occurred more aft on the leeward ray than for the case of the sharp cones and the transition front was determined by turbulent wedges formed as a consequence of the more forward transition on the side. The disturbance believed to be a traveling crossflow wave was observed at 1-deg incidence and its measured frequency was in good agreement with the maximum amplified frequency, which was calculated using a compressible linear eN code.