Three-Dimensional Problem of Radiative Gasdynamics of the Apollo-4 Command Module during Superorbital Atmospheric Entry

The three-dimensional problem of radiative gasdynamics of the superorbital entry of the Apollo-4 command module into the dense terrestrial atmosphere at an angle of attack of 25° is numerically solved. The flow conditions corresponding to the flight velocity V_∞ = 10.5 km/s at an altitude H = 67.3 km are considered in detail. The distributions of the densities of convective and radiative heat fluxes along the surface in a flow are obtained. The spectral composition of the thermal radiation attaining the surface is studied. The results of the calculations are successfully compared with the data of two-dimensional calculations.     

Damping characteristics of a reentry vehicle at hypersonic velocities

The experimental equipment, model, test conditions, and methods used for determining the streamwise damping on a setup with free oscillations on rolling bearings are described. Characteristics of aerodynamic damping of the model with two positions of the rotation axis and Mach numbers M_∞ = 2, 4, and 6 are measured. Irregular oscillations of the model with a greater displacement of the rotation axis with respect to the longitudinal axis are found to arise at M_∞ = 2.     

Radiative melting of ice layer adhering to a vertical surface

This paper is concerned with melting of a vertical ice layer adhering to the substrate by using radiating heat source of halogen lamps having a large fraction of short wave beam or nichrome heater having a comparatively large fraction of long wave one. From the present experimental results, it can be seen that the heating of short wave radiation produces a peculiar melting behavior of strongly rough melting-surface due to the internal melting at the grain boundary of ice-surface. On the other hand, for the case of long wave radiation the melting-surface becomes very smooth. The melting rate of clear ice layer by short wave radiation obtained from halogen lamps is smaller than that of cloudy ice layer due to the good penetration of short wave fraction through the clear ice layer. Moreover, the raising of temperature of ice-substrate interface could offer a feasibility of removing ice layer from the structure subject to atmospheric icing. Concludingly, it is clarified that the melting rate of ice layer could be predicted numerically by using the band model of extinction coefficient or absorption coefficient presented in this study.

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Schmelzen einer Eisschicht an einer senkrechten Wand durch Strahlung

Zusammenfassung Diese Arbeit behandelt das Schmelzen einer senkrechten Eisschicht auf einer Unterlage mit Hilfe von Halogen-Lampen mit einem hohen Anteil an kurzen Wellen und Nichromheizern mit einem hohen Anteil an langen Wellen. Aus diesen Versuchen läßt sich ableiten, daß die Heizung durch kurzwellige Strahlung ein eigentümliches Schmelzverhalten mit sehr rauher Oberfläche hervorruft, verursacht durch Schmelzen an den Korngrenzen der Eisoberfläche. Bei langwelliger Heizung wird die Oberfläche sehr glatt. Die Abschmelzrate einer Klareisschicht bei kurzwelliger Heizung durch Halogen-Lampen ist geringer als die einer Opaleisschicht wegen des besseren Eindringens der kurzen Wellen in das klare Eis. Der Temperaturanstieg an der Grenze Eis — Unterlage bietet die Möglichkeit der Enteisung von Bauteilen, die der atmosphärischen Vereisung ausgesetzt sind. Es folgt, daß die Abschmelzrate einer Eisschicht, numerisch vorausberechnet werden kann, indem man das Bandmodell des Extinktions- und des Absorptionskoeffizienten dieser Arbeit verwendet.

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Nomenclature A transmission, defined in equation (4) - a monochromatic absorption coefficient of clear ice - C constant - E_b monochromatic emissive power - h_i thickness of ice layer - h_in initial thickness of ice layer - h_m thickness of substrate - k₀ extinction coefficient for h₀ 0 - k_s modified extinction coefficient - k monochromatic extinction coefficient - L_i latent heat of melting - n index number, defined in equation (2) - heat flux absorbed at surface of substrate - q_r0 radiant heat flux impinged onto ices-urface - q_ri{y} radiant heat flux in ice layer - S distance from initial ice-surface to transient melting-surface - T_b temperature of radiating heat source - T_i temperature in ice layer - T_m temperature in substrate - T environmental temperature - T₁ temperature of surface of ice layer - T₂ temperature of substrate-surface - T₃ temperature of back side surface of substrate - t time - y distance from initial ice-surface - Z ratio of backward radiative heat flux to forward one for cloudy ice Greek Symbols heat transfer coefficient - _i thermal diffusivity of ice - _m thermal diffusivity of substrate - _i thermal conductivity of ice - _m thermal conductivity of substrate - wavelength - _c critical wavelength - _i density of ice - Stefan-Boltzmann constant     

Analysis of the reasons for an aerodynamic hysteresis in flight tests of the Soyuz reentry capsule at the hypersonic segment of its descent

With the use of a mathematical model developed for describing hysteresis functions of aerodynamic forces and moments depending both on the angle of attack and on the rate of its variation, the emergence of a hysteresis in flight tests of the Soyuz reentry capsule at the hypersonic segment of its descent is found to be induced by damping.     

Radiative heat transfer at the leading edge of a body during intense evaporation

The problem of the flow of a radiating gas near the leading part of a body during intense vaporization of its surface is solved. Significant radiative heating occurs when a sufficiently dense gas flows past the body, thus a gasdynamic model of the flow is used according to which the flow takes place in a shock layer and a vapor layer separated by the contact surface. The radiant energy flux from the shock layer is partially absorbed by a vapor layer and falls on the surface of the body, causing intense vaporization.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 190–192, March–April, 1975.     

Radiative mixed convection flow of an Oldroyd-B fluid over an inclined stretching surface

A mixed convection flow of an Oldroyd-B fluid in the presence of thermal radiation is investigated. The flow is induced by an inclined stretching surface. The boundary layer equations of the Oldroyd-B fluid in the presence of heat transfer are used. Appropriate transformations reduce partial differential equations to ordinary differential equations. A computational analysis is performed for convergent series solutions. The values of the local Nusselt number are numerically analyzed. The effects of various parameters on velocity and temperature are discussed.     

Radiative properties of mixed nested cylindrical wire arrays on Zebra at UNR

The dynamics of mixed nested cylindrical wire arrays were studied at the UNR Zebra generator with our existing theoretical and experimental tools to better understand the contributions of each array to the emitted radiation. In particular, experimental results of mixed brass (70% Cu, 30% Zn) and Al (5056, 5% Mg) nested cylindrical wire arrays are analyzed and compared. The loads used brass in the inner array and Al in the outer array, or alternately, Al in the inner array and brass in the outer array, with a mass ratio of 1:1 (outer to inner). Consequently, radiative properties of K-shell Al and Mg ions and L-shell Cu and Zn ions are compared as functions of the placements of the brass and Al wires on the inner and outer arrays. Results show that the placement of brass and Al, whether on the inner or outer array, dramatically affects the intensity of the X-ray emission. Specifically, the ratio of Cu L-shell to Al K-shell emissions changed from 4 when Al is in the outer array to 40 when brass is in the outer array, and the total radiated yield was highest when the brass was on the outer array (18 kJ, versus 15 kJ when brass is on the inner array). Each load was fielded twice to vary the timing of the time-gated imaging and spectral diagnostics. This provides a more complete understanding of the evolution of the plasma parameters over the X-ray pulse and highlights the importance of the time-gated diagnostics.     

The value of the entropy at the surface of paraboloids

The author studies the magnitude of the entropy at paraboloid surfaces in supersonic perfect gas flow using the numerical results of the solution to the problem of three-dimensional flow past a blunt nose [1]. We first discuss briefly the state of the problem and information on the method of [1] and then present the main conclusions of the study and some data confirming these conclusions.In conclusion, the author thanks V. V. Rusanov for valuable comments and discussion and E. I. Nazhestkin for performing the computer computations and participating in the analysis of the computational results.     

Radiative heating of bodies entering the atmosphere of venus

The problem of the trajectory of a blunt body in a CO₂+N₂ gas mixture simulating the atmosphere of Venus is considered.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.4, pp. 135–139, July–August, 1992.     

Heat transfer at the nose of a blunt body in a rarefied supersonic flow of a nitrogen-hydrogen mixture

The temperature-recovery factor and specific heat flux have been measured at the nose of a spherically blunted body in a low-density supersonic stream of a nitrogen-hydrogen mixture. The experiments were carried out in the transition flow regime from continuous to free-molecular flow. The measurements show that the values of the recovery factor and heat flux in the mixture are larger than in the pure gases.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 6, pp. 88–91, November–December, 1973.The authors are grateful to I. F. Zavarzina and P. G. Itin for assistance.     

Stress state of transversally isotropic body with elliptical crack in the presence of a uniform heat flux at its surface

S. P. Timoshenko Institute of Mechanics, National Academy of Sciences of Ukraine, Kiev. Translated from Prikladnaya Mekhanika, Vol. 31, No. 3, pp. 24–32, March, 1995.     

不同头部形状子弹侵彻钢板的跳弹及规律研究

采用LS-DYNA软件中的拉格朗日有限元方法,对不同头部形状子弹侵彻钢板问题进行了三维数值模拟研究,并与实验结果进行比较分析,结果表明:平头、圆头、尖头子弹侵彻剩余速度计算结果与实验结果吻合较好,相对误差都在10%以内,从而验证了数值分析模型的有效性。在此基础上分别计算了入射速度为400 m/s、500 m/s、600 m/s和倾角分别为50°、55°、60°、65°、70°、75°状态下的平头、圆头、尖头子弹侵彻圆形钢板模型,得出了不同头部形状跳弹规律、跳弹临界角范围、侵彻过程所消耗的动能,为子弹头部形状设计提供了参考。     

Effect of nose shape on hypersonic flow past slender blunt bodies at an angle of attack

We examine some characteristics of hypersonic flow past slender blunt bodies of revolution at a small angle of attack 1, where is the relative body thickness. It is shown that, within the framework of hypersonic theory, for a correct-consideration of the effect of the conditions in the transitional section between the nose and the lateral surface it is necessary, in the general case, to specify the circumferential distribution of the force effect for the nose and the mass of the gas. For small , the effect of the nose, just as in two-dimensional flows [1–4], shows up only through its drag coefficient c_x, for =0. On this basis, the similarity law [1–4] for flow past such bodies, with arbitrary form of the lateral surface and differing in the shape of the nose blunting, which is valid over the entire disturbed region, with the exception of a small vicinity of the nose, is extended to the case in question.The notation r₀ and L maximum nose radius and characteristic body length - V, M, and density, velocity, Mach number, and adiabatic exponent of the gas in the approaching stream - , V²i, and V²p density, enthalpy, and pressure - x, r, and coordinate system of the cylindrical body with its center at the transitional section between the nose and the side surface - Vu, Vv, and Vw corresponding velocity components