A laminar walljet on a moving wall

Summary The laminar wall jet from a momentum source at the leading edge on a wall which is moving in the same direction with uniform velocity is considered. It is shown that a solution is possible starting at the leading edge and proceeding all the way downstream. For smallx (x measures distance along the wall) we find the solution by using a natural coordinate expansion in powers ofx ^1/2. For largex, the asymptotic solution is approached through eigensolutions and the two coordinate expansions are then joined by a numerical solution of the full equations.With 2 Figures     

Flow analysis in a channel with a moving wall

Numerical results obtained by solving the complete system of Navier-Stokes equations for a channel with one movable surface are evaluated.     

Conjugate heat exchange in the initial stage of reflection of a viscous shock wave from a wall

A numerical solution of the conjugate heat-exchange problem for reflection of a normally incident viscous shock wave from a rigid wall is used to find the nonsteady-state temperature of the wall and the thermal flux into the wall.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 51, No. 2, pp. 217–224, August, 1986.     

Double-crystal diffractometer study of thermal neutron specular reflection

A double-crystal diffractometer with perfect crystals is used to study the specular reflection of thermal neutrons. If the mirror surface is placed between the crystals then it is possible to separate the effects of surface reflectivity and surface geometry. The critical angle can be determined with an accuracy of 1″ even if the mirror curvature reaches 1′.     

Steady-state temperature field of a wall with cylindrical cooling channels

The Bubnov-Galerkin method is combined with the structural method worked out by Rvachev to solve the problem of the steady-state temperature field of a wall with cylindrical cooling channels in a two-row arrangement.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 30, No. 2, pp. 355–359, February, 1976.     

Electroacoustic waves of a moving domain wall superlattice in a ferroelectric crystal

The dispersion properties of electroacoustic wave modes confined by a superlattice of 180° domain walls uniformly moving in a tetragonal ferroelectric crystal are considered. It is shown that the manifold of partial electroacoustic interfacial waves in the superlattice is restricted to the first allowed band, the configuration of which in the plane of spectral variables can significantly vary under the action of moving domain walls. For the partial electroacoustic interfacial waves with the Bloch wavenumbers χ π/d (where d is the lattice half-period), the motion of domain walls is predicted to result in splitting of the modes of a static superlattice into pairs, which is invariant with respect to reversal of the direction of motion.     

Micropolar boundary layer flow at a stagnation point on a moving wall

The theory of micropolar fluids due to Eringen is used to formulate a set of boundary layer equations for 2-dimensional flow of an incompressible, constant density micropolar fluid at a stagnation point on a moving wall. The governing boundary layer equations are solved numerically. The development of the velocity of distribution has been illustrated for several positive and negative values of the wall velocity. A discussion is provided for the dependence of the important flow characteristics on the material parameters.     

Calculation of the cooling of a liquid moving in an underground channel

An approximate solution is obtained for a problem of the cooling of a liquid moving a channel. The problem is solved on the basis of the use of the Laplace transform and the variational method.     

Calculation of heating and cooling of products moving longitudinally in a fluidized bed

An analysis is made of the problem of the heating and cooling of a metal product moving through two sequentially arranged chambers containing a fluidized bed in the presence of a return flow of heat by thermal conduction along the axis of the product.     

Ultrasonic reflection from a stressed interface

In seeking to develop an NDE technique for verifying the serviceability of NiTi couplers for plumbing unions, it was found that the reflection coefficient for a normally incident ultrasonic wave correlated with the stress level at the NiTi-tubing interface. Current theory pertaining to interface reflection is not complete but, even at present status, there is semiquantitative accord between theoretical predictions and normalized data for reflection coefficient versus stress level. These results are at fixed frequency and with comparable surface roughness. Variation of either frequency or surface roughness further affects the reflection coefficient. Current studies are being pursued to define this effect.     

Elastic oscillations induced by a moving domain wall in yttrium orthoferrite plate

Elastic oscillations induced in a 0.1-mm-thick yttrium orthoferrite plate by a moving domain wall have been observed for the first time. The results of model calculations show that these oscillations correspond to Lamb flexural waves.     

Effect of initial turbulence on the efficiency of cooling a permeable wall

The effect of turbulence in the outer stream (=1.7, 5.3, 9.3%) on convective heat transfer is analyzed in the case of flow around impermeable and permeable plates.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 36, No. 6, pp. 965–971, June, 1979.     

The thermal state of a porous wall under conditions of transpiration cooling

Results of numerical experiment are used for analysis of fields of temperature in a laminar boundary layer, in a porous wall, and in a cooling gas delivery chamber, as well as for analysis of heat transfer and of distribution of the temperature difference between the cooling gas and the porous wall frame and cooling efficiency. It is demonstrated that heat transfer between a porous wall of finite thickness and a high-temperature gas flow differs significantly from heat transfer with preassignment of the same intensity of injection and of the homogeneous thermal boundary condition directly on the surface subjected to flow. One of the reasons for this is the formation of wall temperature variable along the boundary layer.     

High-speed thermal stress cleaving by moving heat with mist cooling

Two types of different trials were examined experimentally to increase a cleaving velocity in thermal stress cleaving. One is a partial cooling by water mist spray on the propagating crack surface and the other is a preformation of a slightly high-temperature zone by preheating. It is known that when other cleaving conditions are fixed, the cleaving velocity decreases with increase in width of the target object. This characteristic of thermal stress cleaving is often considered as a shortcoming for practical applications. Therefore, improvement of the cleaving efficiency by increasing a cleaving velocity is one of the important issue in the thermal stress cleaving. It was found experimentally that the maximum attainable cleaving velocity was increased from 38 to 55 mm/s when mist cooling was employed in addition to the usual laser beam heating of 10 W magnitude for 31 mm width specimen. On the other hand, the most effective preheat technique realized more than 400% increase in the cleaving velocity for 62 mm width specimen. The background why these two types of different approaches both contribute to improve the cleaving velocity was discussed based on the linear elastic fracture mechanics.     

Optical reflection from a semiinfinite nonlinear crystal

Multistability of the reflection coefficient as a function of incident amplitude is theoretically demonstrated to be possible for a semiinfinite optically homogeneous medium with the Kerr nonlinearity. The multistability arises at certain relations between the system parameters. The treatment is essentially free from the assumption that field envelopes vary slowly in space. Underlying physical processes are described.     

The adsorption of surfactants at the air-liquid interface from complex mixtures,measured by specular neutron reflection

The specular reflection of neutrons, in combination with isotopic labeling, has been shown to be a powerful technique for the study of surfactant absorption at the air-liquid interface. It can be used to obtain adsorbed amounts in complex multicomponent systems and to determine the structure of the adsorbed monolayer. The adsorption of the alkyl polyoxyethylene nonionics surfactant and mixtures of anionic and cationic surfactants with the nonionic surfactants is described. The effects of temperature, electrolyte, and less polar solvents (the addition of sorbitol) to the adsorption and structure are discussed.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

Nonsimilar second order viscoelastic boundary layer flow at a stagnation point over a moving wall

An analysis is presented to investigate the fluid dynamic characteristics of a steady, laminar second order viscoelastic boundary layer flow at a two-dimensional stagnation point over a moving wall. The governing boundary layer equations have been solved by means of a series solution approach. Numerical solutions for the series functions have been given in tabular form. The development of the velocity distribution has been illustrated for several positive and negative values of the wall velocity. The values of the Weissenberg numbers ranged from 0 to 0.3.     

Flow transport in a microchannel induced by moving wall contractions: a novel micropumping mechanism

A novel micropumping mechanism based on a theoretical model that describes flow transport in a microchannel induced by moving wall contractions in the low Reynolds number flow regime is presented. The channel is assumed to have a length that is much greater than its width (d = W/L << 1{\delta = W/L \ll 1}) and the upper wall is subjected to prescribed, non-peristaltic, localized moving contractions. Lubrication theory for incompressible viscous flow at low Reynolds number (R _e ~ δ) is used to model the problem mathematically and to derive expressions for the velocity components, pressure gradient, wall shear stress, and net flow produced by the wall contractions. The effect of contraction parameters such as amplitude and phase lag on the time-averaged net flow over a single cycle of wall motions is studied. The results presented here are supported by passive particle tracking simulations to investigate the possibility of using this system as a pumping mechanism. The present study is motivated by collapse mechanisms observed in entomological physiological systems that use multiple contractions to transport fluid, and the emerging novel microfluidic devices that mimic these systems.