Jose M. Caram

Bio: Jose M. Caram is an academic researcher. The author has contributed to research in topics: Orbiter & Wind tunnel. The author has an hindex of 7, co-authored 13 publications receiving 203 citations.

Shuttle Orbiter Experimental Boundary-Layer Transition Results with Isolated Roughness

Abstract: The effect of isolated roughness on the windward surface boundary layer of the Shuttle Orbiter has been experimentally examined in the NASA Langley Research Center 20-InchMach 6 Tunnel. The size and location of isolated roughness elements (intended to simulate raised ormisalignedShuttleOrbiter Thermal Protection System tiles and protruding gap Ž ller material) were varied to systematically examine the response of the boundary layer. Global heat transfer images of the windward surface of a 0.75%-scaleOrbiter at an angle of attack of 40 deg were obtained over a range of Reynolds numbers using phosphor thermography and were used to infer the status of the boundary layer. Computationalpredictions were performed to provide both laminar and turbulent heating levels for comparison to the experimental data and to provide  owŽ eld parameters used for investigatingboundary-layer transition correlations. A variety of roughness heights and locations along the windward centerline were used. The roughness-transition correlation, using the predicted edge parameters Re /Me and k/ , was well behaved. The off-centerline results illustrate the potential for an asymmetric transition pattern to be isolated to one side of the vehicle, thereby causing the increased yawing moments experienced in  ight.

Isolated Roughness Induced Boundary-Layer Transition: Shuttle Orbiter Ground Tests and Flight Experience

Abstract: Recent Orbiter wind tunnel data and flight data have been used to evaluate boundary-layer transition induced by discrete-roughness elements on the Orbiter windward surface. Orbiter flow field calculations have been used to compute transition parameters and disturbance parameters for correlating the results and comparing the trends. Existing transition correlations have been modified and applied to the Orbiter. These correlations provide a means to predict transition on the Orbiter given a known isolated roughness element. Furthermore, these data and data reduction methods provide information and guidance for the prediction of transition due to &screte-roughness elements on future winged reentry vehicles.

Effect of Isolated Roughness Elements on Boundary-Layer Transition for Shuttle Orbiter

Abstract: A 1.75% scale model of the Shuttle Orbiter has been tested in the Mach 8 Tunnel B at the Arnold Engineering Development Center with and without isolated roughness elements. Heat e ux gauges on the windward surface permitted the evaluation of heat transfer distributions and boundary-layer transition trends on the Orbiter’ s windwardsurface.Thedataobtainedduringthecurrentprogramhavebeenreviewedandcomparedwithtransition resultsfrom previoustestsusing both a smooth model and thosewith distributed roughness. Resultsindicated that, for many test conditions, a single, relatively small roughness element can be effective in promoting boundary-layer transition, i.e., moving transition close to the roughness element.

Overview of X-38 Hypersonic Wind Tunnel Data and Comparison with Numerical Results

Abstract: A NASA team of engineers has been organized to design a crew return vehicle for returning International Space Station crew members from orbit. The hypersonic characteristics of this X-23/X-2&4 derived crew return vehicle (designated X-38) are being evaluated in various wind tunnels in support of this effort. Aerodynamic data has been acquired in three NASA hypersonic facilities at Mach 20, and Mach 6. Computational Fluid Dynamics tools have been applied at the appropriate wind tunnel conditions to make comparisons with portions of this data. Experimental data from the Mach 6 Air and CF4 facilities illustrate a net positive pitching moment increment due to density ratio, as well as increased elevon effectiveness. Chemical nonequilibrium computational fluid dynamics solutions at flight conditions reinforce this conclusion.

Effects of Roughness on Hypersonic Boundary-Layer Transition

Abstract: The effect of roughness on hypersonic boundarylayer transition has been studied for three primary purposes: to trip a laminar layer to turbulence, to determine whether naturally occurring roughness is expected to cause early transition, and to determine the largest allowable roughness that will not affect the location of transition. Roughness is often divided into two classes: isolated roughness in which each protuberance can be considered separately, and distributed roughness similar to sandpaper, in which the roughness elements are many and are not considered separately. The effects of roughness on hypersonic transition are reviewed, considering the physics of the process, known parametric effects, some of the common correlations, and a few case studies. The three or more modes by which roughness can affect transition are outlined. At hypersonic edge Mach nunbers, it requires very large roughness heights to affect transition. Various correlations are often used to estimate the effect of roughness; several of these are described, although none provide good agreement with all the data.

Flight Data for Boundary-Layer Transition at Hypersonic and Supersonic Speeds

Abstract: Published e ight data for boundary-layer transition at hypersonic speeds are surveyed. The survey is limited to measurements reported in the open literature and carried out at hypersonic and high-supersonic speeds, on vehicles for which ablation is believed to be negligible or small. The emphasis is on work that may be suitable for validation of advanced transition-estimation methods that are based on simulation of the physical mechanisms, such as e N , the parabolized stability equations, and direct numerical simulations. Brief discussions are presented for each report. Known comparisons to the advanced simulation methods are also presented. Nomenclature Me = Mach number at the boundary-layer edge Res = Reynolds number at transition onset, based on arc length from the leading edge and local conditions at the boundary-layer edge ReT = Reynolds number at transition onset, based on arc length and conditions at the boundary-layer edge ReT/ft = unit Reynolds number per foot, at the boundary-layer edge at transition onset Reµ = Reynolds number at transition, usually onset, based on momentum thickness and conditions at the boundary-layer edge Te = temperature at the boundary-layer edge Tr = recovery temperature at the wall Tw = wall temperature xT = arc length to transition onset, from the nose µc = cone half-angle, deg

Review and synthesis of roughness-dominated transition correlations for reentry applications

Abstract: Nomenclature a = constant; Fig. 1 C , C 0 = constants k = roughness element height, ft N k = average roughness element height, ft L = vehicle length, ft M = Mach number n = exponent; Fig. 1 N R = Poll’s transition parameter; Eq. (1) Reke = roughnessReynolds number based on height k and edge conditions Rekk = roughnessReynolds number based on height k and conditions at k Reμ = Reynolds number based on height μ and edge conditions U = velocity component parallel to test surface or velocity component perpendicularto attachment line, ft /s V = velocity component parallel to attachment line, ft/s X = generalized disturbanceparameter or axial coordinate along windward centerline x = coordinate perpendicular to attachment line, ft Y = generalized transition parameter ® = angle of attack, deg ± = smooth-wall laminar boundary-layer thickness, ft = Poll’s length scale [Eq. (2)], ft μ = smooth-wall laminar boundary-layermomentum thickness, ft 1 = viscosity, lbm/ft ¢ s o = kinematic viscosity, ft2/s 1⁄2 = density, lbm/ft

Hypersonic Boundary-Layer Trip Development for Hyper-X

Abstract: Boundary-layer trip devices for the Hyper-X forebody have been experimentally examined in several wind tunnels.Fivedifferenttripconegurationswerecomparedinthreehypersonicfacilities:theNASALangleyResearch Center 20-Inch Mach 6 Air and 31-Inch Mach 10 Air tunnels and in the HYPULSE Reeected Shock Tunnel at the General Applied Sciences Laboratory. Heat-transfer distributions, utilizing the phosphor thermography and thin-elm techniques, shock system details, and surface streamline patterns were measured on a 0.333-scale model of the Hyper-X forebody. Parametric variations include angles of attack of 0, 2, and 4 deg; Reynolds numbers based on model length of 1.2 ££ 10 6‐15.4 £ 10 6 ; and inlet cowl door simulated in both open and closed positions. Comparisons of boundary-layer transition as a result of discrete roughness elements have led to the selection of a trip coneguration for the Hyper-X Mach 7 eight vehicle.

Computational Aerothermodynamic Design Issues for Hypersonic Vehicles

Abstract: A brief review of the evolutionary progress in computational aerothermodynamics is presented. The current status of computational aerothermodynamics is then discussed, with emphasis on its capabilities and limitations for contributions to the design process of hypersonic vehicles. Some topics to be highlighted include: (1) aerodynamic coefficient predictions with emphasis on high temperature gas effects; (2) surface heating and temperature predictions for thermal protection system (TPS) design in a high temperature, thermochemical nonequilibrium environment; (3) methods for extracting and extending computational fluid dynamic (CFD) solutions for efficient utilization by all members of a multidisciplinary design team; (4) physical models; (5) validation process and error estimation; and (6) gridding and solution generation strategies. Recent experiences in the design of X-33 will be featured. Computational aerothermodynamic contributions to Mars Pathfinder, METEOR, and Stardust (Comet Sample return) will also provide context for this discussion. Some of the barriers that currently limit computational aerothermodynamics to a predominantly reactive mode in the design process will also be discussed, with the goal of providing focus for future research.