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Wind-inflated cone reduces turbulence that ordinarily occurs in air just behind square-back truck traveling at high speed. Wind around truck would enter slits in folded cone and automatically deploy it. Energy lost to air turbulence greatly reduced, and fuel consumed by truck reduced accordingly. In addition, less air turbulence means less disturbance to nearby vehicles on highway.
The effects of free-stream unit Reynolds number, angle of attack, and nose shape on the aerothermal environment of a 3-ft basediameter, 12.5 deg half-angle cone were investigated in the Langley 8-foot high temperature tunnel at Mach 6.7. The average total temperature was 3300 R, the freestream unit Reynolds number ranged from 400,000 to 1,400,000 per foot, and the angle of attack ranged from 0 deg to 10 deg. Three nose configurations were tested on the cone: a 3-in-radius tip, a 1-in-radius tip on an ogive frustum, and a sharp tip on an ogive frustum. Surface-pressure and cold-wall heating-rate distributions were obtained for laminar, transitional temperature in the shock layer were obtained. The location of the start of transition moved forward both on windward and leeward sides with increasing free-stream Reynolds numbers, increasing angle of attack, and decreasing nose bluntness.
It is shown experimentally that the seed metals which can cause cone development on ion bombarded metal targets need not to have a lower sputtering yield as widely believed but rather a higher melting point. By lowering the bombarding ion energy to near sputtering threshold values (less than 100 eV) the growth of genuine single crystal whiskers which point in all directions not related to the direction of ion incidence is observed. It is concluded that (intentional or unintentional) seed cones are the result of an interplay among whisker growth, surface movement of atoms, and the effects of sputtering.
A comparison of transition on wavy-wall and smooth-wall cones in a Mach 3.5 wind tunnel is made under conditions of either low freestream noise (quiet flow) or high freestream noise (noisy flow). The noisy flow compares to that found in conventional wind tunnels while the quiet flow gives transitional Reynolds numbers on smooth sharp cones comparable to those found in flight. The waves were found to have a much smaller effect on transition than similar sized trip wires. A satisfatory correlating parameter for the effect of waves on transition was simply the wave height-to-length ratio. A given value of this ratio was found to cause the same percentage change in transition location in quiet and noisy flows.
Shatter cone fragments were recovered from rock cores at two previously suspected, but heretofore unverified, impact structures in Illinois. Both sites are buried features known from geophysical surveys and drill holes. Shatter cones are accepted widely as field criteria of meteoritic impact. Detection of these shock indicators in both the Glasford Structure and the Des Plains Disturbance upgrades these sites in Earth's inventory of known and suspected impact structures from possible impact sites with compatible structure and morphology to probable impact structures which possess also evidence of shock metamorphism.
A 12.5 degree half cone with tangential slot injection at Mach 6.95 was studied to determine the heating rates to the surface of the body near and far downstream of the slot. The cone had a zero degree angle of attack. The heating rates were obtained using a computer program that was developed at NASA-Langley Research Center. The concentration of nitrogen from the slot into the boundary layer was also determined. The ratio of slot to freestream was varied to determine its effect on heating. The numerical heating rates were compared to other correlations obtained from experimental studies as well as theoretical laminar and turbulent results.
Experimental longitudinal and lateral-directional aerodynamics were obtained for a generic aerodynamics were obtaiend for a generic winged-cone configuration having possible application as a transatmospheric vehicle concept. Data were obtained at Mach numbers from 0.6 to 20.0; Reynolds numbers, based on model length, between 2.5 and 5.3 million; and angles of attack from -4 to 20 deg. Results indicate a longitudinal center-of-pressure travel of about 23 percent of the fuselage length for the test Mach number range, with longitudinal instabilities noted at high-supersonic to hypersonic Mach numbers. These instabilities are coupled with directional instability at similar Mach numbers. Predictions with analytic codes, namely, the USAF DATCOM and the tangent-cone option of the Hypersonic Arbitrary Body Program, provided fair agreement with the experimental aerodynamic characteristics at low angles-of-attack.
An inviscid discrete vortex model, with newly derived expressions for the tangential velocity imposed at the separation points, is used to investigate the symmetric and asymmetric vortex separation on cones and tangent ogives. The circumferential locations of separation are taken from experimental data. Based on a slender body theory, the resulting simultaneous nonlinear algebraic equations in a cross-flow plane are solved with Broyden's modified Newton-Raphson method. Total force coefficients are obtained through momentum principle with new expressions for nonconical flow. It is shown through the method of function deflation that multiple solutions exist at large enough angles of attack, even with symmetric separation points. These additional solutions are asymmetric in vortex separation and produce side force coefficients which agree well with data for cones and tangent ogives.
This paper considers the previously unidentified waveforms in the Uranian magnetosphere, involving decreasing frequency with time, which were recorded during the Voyager-2 flyby of Uranus. Applying to these waveforms the basic theory of the resonance cone emission in the X mode for a homogeneous plasma, it is shown that the observed waveforms and their features can be created by bands of X-mode waves on the resonance cone. It is demonstrated that the theory can produce simultaneously the arching downward shape of the waveform and the decreasing frequency of the periodic modulation.
Computations of the hypersonic flow around sharp cones were carried out using the PNS code with attention given to the heat transfer predictions around the transition region. Results of calculations performed over 5, 8, and 10 deg half-angle sharp cones in the Mach number range of 7 to 10 are presented. It is noted that calculations of this type have become an integral part of the general design procedure for hypersonic vehicles such as the National Aerospace Plane and the Space Shuttle.
Analytical solutions for radiation-driven winds of hot stars including the important finite cone angle effect (see Pauldrach et al., 1986; Friend and Abbott, 1986) are derived which approximate the detailed numerical solutions of the exact wind equation of motion very well. They allow a detailed discussion of the finite cone angle effect and provide for given line force parameters k, alpha, delta definite formulas for mass-loss rate M and terminal velocity v-alpha as function of stellar parameters.
The unsteady, compressible, double and single thin-layer Navier-Stokes equations are used to numerically study for the passive control of steady and unsteady, supersonic asymmetric flows around circular and noncircular cones. The main computational scheme of the present study is the implicit upwind, flux-difference splitting, finite-volume scheme. Passive control of flow asymmetry is studied by using a vertical fin in the leeward plane of geometric symmetry and side strakes with and without thickness at different orientations. The study is focused on circular-section cones since they are the most potential section-shapes for strong flow asymmetry. Side-strakes passive control has been shown to be more efficient and practical than the vertical-fin passive control.
The weakly relativisitic dielectric tensor for a system of electrons comprised of cold and energetic populations, embedded in a neutralizing background, is reformulated in terms of an infinite series representation in powers of lamba = alpha ck(perpendicular)/omega (c), where alpha-squared is a parameter proportional to the average thermal energy of the energetic electrons, k(perpendicular) is the perpendicular component of the wave vector k, and omega (c) is the electron gyrofrequency. The energetic electrons are assumed to have a loss-cone feature in the perpendicular momentum space. The present formalism can be used in the problem of cyclotron maser as well as more general gyroharmonic maser (i.e., multiharmonics) emissions resulting from weakly relativistic loss-cone electrons. This is because, unlike the previous theories in which certain approximations such as the single-harmonic approximations are made, the present formalism retains contributions from the entire harmonics.
The unsteady, compressible, single and double thin-layer, Navier-Stokes equations are used to solve for steady and unsteady, asymmetric, supersonic flow around pointed bodies with noncircular sections at high incidence and zero side slip. The equations are solved by using an implicit, upwind, flux-difference splitting finite-volume scheme. Since the flow is locally conical, the solutions are presented on a cross-flow plane at the axial station of unit. The grid is generated by using a modified Joukowski transformation. The computational applications cover noncircular sections with elliptic and diamond shapes. Unsteady asymmetric vortex shedding has been captured at large angles of attack. It is shown that for the same flow conditions and same cross-section fineness ratio, the diamond-section cones develop less flow asymmetry than the elliptic-section cones. Passive control of flow asymmetry was also demonstrated computationally.
A laser transit anemometer (LTA) system was used to probe the boundary layer on a slender (5 degree half angle) cone model in the Langley unitary plan wind tunnel. The anemometer system utilized a pair of laser beams with a diameter of 40 micrometers spaced 1230 micrometers apart to measure the transit times of ensembles of seeding particles using a cross-correlation technique. From these measurements, boundary layer profiles around the model were constructed and compared with CFD calculations. The measured boundary layer profiles representing the boundary layer velocity normalized to the edge velocity as a function of height above the model surface were collected with the model at zero angle of attack for four different flow conditions, and were collected in a vertical plane that bisected the model's longitudinal center line at a location 635 mm from the tip of the forebody cone. The results indicate an excellent ability of the LTA system to make velocity measurements deep into the boundary layer. However, because of disturbances in the flow field caused by onboard seeding, premature transition occurred implying that upstream seeding is mandatory if model flow field integrity is to be maintained. A description and results of the flow field surveys are presented.
The results are presented of an analytic and experimental research program involving a Sikorsky S-55 helicopter tail cone directed ultimately to the improved structural analysis of airframe substructures typical of moderate sized helicopters of metal semimonocoque construction. Experimental static strain and dynamic shake-testing measurements are presented. Correlation studies of each of these tests with a PC-based finite element analysis (COSMOS/M) are described. The tests included static loadings at the end of the tail cone supported in the cantilever configuration as well as vibrational shake-testing in both the cantilever and free-free configurations.
A self-consistent numeric two-dimensional code using kinetic-wave particle equations has been developed and applied to the maser dynamics of the solar corona. Time histories generated by the code reveal details of the evolution of the linear phase, the saturation and subsequent relaxation of the loss cone. Quantitative values are obtained for the saturation time, the amount of the converted free energy, the critical wave energy level for onset of maser diffusion, the velocity and pitch angle range of the resonant particles, and the relative importance of the different magnetoionic modes and harmonics. A wide range of initial conditions is covered by varying the loss-cone distribution and the ambient cold plasma parameters.
The supersonic viscous flow over a 5-degree half-angle cone at an angle of attack of four times the cone half-angle is studied computationally using both the conical and the three-dimensional Navier-Stokes equations. The numerical solutions were obtained with an implicit, upwind-biased algorithm. Asymmetrical flowfields of the absolute-instability type are found using the conical-flow equations which agree with published results. However, the absolute instabilities of the originally symmetric flow found with the conical equations do not occur in the three-dimensional simulations, although spurious asymmetric three-dimensional flows for symmetric bodies arise if the grid resolution is insufficient in the nose region. The asymmetric flows computed with the three-dimensional equations are convective instabilities and are possible if the local Reynolds number exceeds a critical value and a fixed geometric asymmetry is imposed. A continuous range of asymmetries can be developed, depending on the size of the disturbance and the Reynolds number. As the Reynolds number is increased, the asymmetries demonstrate a bistable behavior at levels of side force consistent with those predicted using the conical equations. Below a certain critical Reynolds number, any flow asymmetries arising from a geometrical asymmetry are damped with increasing distance downstream from the geometrical asymmetry.