The boundary layer flow of a Reiner-Rivlin fluid near a spinning cone

Summary The steady motion of an incompressible inelastic Reiner-Rivlin fluid near a spinning cone has been studied and a similarity solution has been presented. It has been shown that the flow patterns can be obtained from Srivastava-Jain's work. But the pressure distribution is not the same and we have given the numerical values of the pressure in two tables and have also shown their variation in two figures.Sponsored by the Mathematics Research Center, United States Army, Madison Wisconsin under Contract No.: DA-11-022-ORD-2059.     

Finite element analysis of incompressible laminar boundary layer flows

A numerical procedure was developed to solve the two-dimensional and axisymmetric incompressible laminar boundary layer equations using the semi-discrete Galerkin finite element method. Linear Lagrangian, quadratic Lagrangian, and cubic Hermite interpolating polynomials were used for the finite element discretization; the first-order, the second-order backward difference approximation, and the Crank-Nicolson method were used for the system of non-linear ordinary differential equations; the Picard iteration and the Newton-Raphson technique were used to solve the resulting non-linear algebraic system of equations. Conservation of mass is treated as a constraint condition in the procedure; hence, it is integrated numerically along the solution line while marching along the time-like co-ordinate. Among the numerical schemes tested, the Picard iteration technique used with the quadratic Lagrangian polynomials and the second-order backward difference approximation case turned out to be the most efficient to achieve the same accuracy. The advantages of the method developed lie in its coarse grid accuracy, global computational efficiency, and wide applicability to most situations that may arise in incompressible laminar boundary layer flows.     

Study of laminar boundary layer separation on a cone at an angle of attack

Experimental data are obtained on the position of the line of separation as a function of angle of attack, cone apex angle, and flow Mach number.     

Stability of laminar boundary layer on an elastic surface in an incompressible fluid

Interest in the present problem arose after the publication of the results of the experiments of Kramer [1–3]. In addition to the studies indicated in [4], the articles [5–8] are devoted to the question of the interaction of a flexible elastic surface with the boundary layer. In the present paper the problem of the interaction of an elastic surface with disturbances arising in the boundary layer is posed as in [4]. The approximate nature of the methods of solving the problem of the hydrodynamic stability of the laminar boundary layer leads to a difference in the final computational formulas even in the case when authors use the same Heisenberg-Tollmien-Schlichting-Lin scheme. Therefore, in what follows we present a comparison of the data on the stability of the boundary layer on a solid wall obtained by several authors with the calculations using the formulas, which are then generalized to the case of the elastic surface.The author wishes to thank G. I. Petrov and V. A. Medvedev for discussions of the present study.     

Stability of a laminar boundary layer in an incompressible fluid with variable physical properties

The stability of plane-parallel flows of an incompressible fluid with variable kinematic viscosity in the presence of solid walls has been discussed in [1–5]. The stability of Couette flow is considered in [1]. The method of solution, which is the same as that used in [2], differs from the Tollmien-Schlichting method, since the expansion of the solutions in powers of R which is used assumes the smallness of this quantity. A general formulation of the problem of stability of a nonuniform fluid is presented in [3]. Di Prima and Dunn [4] used the Galerkin method to study the stability of the boundary layer relative to vortex-like disturbances in the case of variable kinematic viscosity. Since the development of this sort of disturbance depends only weakly on the form of the velocity profile in the boundary layer, a marked change of the viscosity had little effect on the critical Reynolds number. This same problem is considered in [5], The present author was not able to find in the literature any references to study of the stability of the laminar boundary layer in an incompressible fluid with variable kinematic viscosity relative to disturbances of the Tollmien-Schlichting type, with the exception of mention in [4] of an unpublished work of MacIntosh which showed the essential dependence of the critical Reynolds number on the viscosity gradient.In Section 1 an analysis is made of the effect of variability of the kinematic viscosity on the stability of the boundary layer relative to Tollmien-Schlichting waves under the condition of constant fluid density.Two approaches are possible to the study of the development of disturbances in a heterogeneous fluid. On the one hand, we can assume that the displacement of the fluid particles does not cause changes in the distribution of p(y) and _*(y), i.e., the velocity pulsations are not accompanied by pulsations of and _*. This will be the case if a particle which is characterized by the quantities ₁, ₁ entering a layer with the different values _{2 2}, instantaneously alters its properties so that its density becomes equal to ₂, and its kinematic viscosity becomes equal to ₂. On the other hand, we can consider that a fluid particle moving from layer 1 into layer 2 fully retains the properties which it had in layer 1. In this case the velocity pulsations naturally lead to pulsations of the quantities and _*.In actuality, the phenomenon develops along some intermediate scheme, since the particle alters its properties as it moves in a heterogeneous fluid. The degree of approximation of the process to the first or second scheme depends on the rate of these changes. The analyses below are based on the first scheme.     

Stability of the laminar boundary layer in an incompressible gas bearing a solid impurity

The article considers the problem of the effect of solid particles suspended in a gas on the stability of the laminar boundary layer with respect to Tollmin-Schlichting waves. An actual scheme for calculating stability is proposed, based on Lin's method. It is shown that, with small values of the concentration of the impurity, s, the critical Reynolds number depends on the parameter =s ( is the dimensionless relaxation time of a particle), increasing with an increase in this parameter. An impurity consisting of asymmetric particles leads to a smaller increase of the stability than an impurity consisting of spherical particles of the same mass.Translated from Izvestiya Akademii Nauk SSSR. Mekhanika Zhidkosti i Gaza, No. 2, pp. 103–110, March–April, 1971.     

Similarity conditions for heat transfer in incompressible two-dimensional laminar boundary layer flow

Summary Similarity conditions are presented for the solution of some problems of heat transfer in incompressible two-dimensional boundary layer flow. The treatment holds for forced convection as well as for free convection. For free convection no a priori restriction is made with respect to geometry or temperature distribution of the solid surface. For forced convection the treatment is restricted to uniform bulk flow parallel to a flat surface of non-uniform temperature or heat flux. The results are summarized in some tables that facilitate comparison with older work.     

Effects of blowing or suction on the laminar boundary layer flow over a rotating cone

The effects of suction or blowing at the surface of a rotating cone in a quiet fluid on the skin friction and heat transfer are described. The equations which govern the fluid motion and thermal energy transfer are transformed by the boundary layer approximations and the resulting equations are solved under the condition that the suction or blowing velocity varies as x ⁿ (x: distance measured from the apex of the cone, n: arbitrary constant). The solutions are obtained as a perturbation from the basic laminar flow of an incompressible viscous fluid over the impermeable rotating cone. Detailed numerical calculations are performed for the case of an isothermal rotating cone with uniform blowing or suction, i.e. n=0, the Prandtl number being 0.72. Results are given for the shear stress, heat transfer and velocity and temperature fields. It is shown from the analysis that suction sharply increases the circumferential shear stress and the heat transfer at the surface.Nomenclature c proportional constant - C _fx dimensionless skin friction factor, _x /(V ²) - C _fx0 dimensionless skin friction factor for an impermeable cone - C _fy dimensionless circumferential skin friction factor, _y /(V ²) - C _fy0 dimensionless circumferential skin friction factor for an impermeable cone - c _p specific heat at constant pressure - f _k function of - g _k function of - h heat transfer coefficient, q/(T _w–T ) - k thermal conductivity of fluid - n arbitrary constant - Nu _x local Nusselt number, hx/k - Nu _x0 local Nusselt number for an impermeable cone - Pr Prandtl number - q heat transfer rate - r radius of a circular cross section of the cone, x sin - R _x Reynolds number, Vx/ - T temperature - T _w surface temperature of the cone - T temperature of the surrounding fluid - u fluid velocity in x-direction - v fluid velocity in y-direction - V circumferential velocity at the cone surface, r - w fluid velocity in z-direction - x coordinate along meridional section - y coordinate along a circular cross section - z coordinate perpendicular to both x and y - perturbation parameter, cx ⁿ /(x sin )^1/2 - dimensionless z-coordinate, z( sin /)^1/2 - _k function of - kinematic viscosity - density of fluid - _x skin friction in x-direction - _y circumferential skin friction - stream function - angular speed of the cone     

Three-dimensional laminar boundary layer on a blunt body

We consider the Prandtl laminar boundary layer which occurs with stationary flow about a blunted cone at an angle of attack. The solution of the Prandtl equations is sought using a finite difference method. It is found that a smooth solution of the problem exists only in the vicinity of the rounded nose of the body, while far from the nose the solutions acquire a singularity; in the problem symmetry plane (on the downwind side) there is a discontinuity of the first derivatives of the velocity components and the density. In the study of the Prandtl boundary layer in the problem of stationary flow about a pointed cone at an angle of attack, it has been shown [1] that the self-similar solution (dependent on two independent variables) of the Prandtl equations has a discontinuity of the first derivatives in the problem symmetry plane (on the downwind side of the cone). The suggestion has been made that in the three-dimensional problem of flow about a blunt cone at an angle of attack the solutions of the Prandtl equations may also be discontinuous. The present study was carried out to clarify the nature of the behavior of the solutions of the three-dimensional Prandtl equations. To this end we considered stationary supersonic flow of an ideal gas past a blunted cone. The results of this study (as well as those of [1]) were obtained using a numerical, finite-difference method. However, an analysis of the numerical results (investigation of the scheme stability, reduction of step size, etc.) shows that the properties of the solutions of the finite-difference equations are not in this case a result of numerical effects, but reflect the behavior of the solutions of the differential equations. The mathematical problem on the boundary layer which is considered in this study will be formulated in §2; this formulation is due to K. N. Babenko.     

The laminar boundary layer near a body corner point

A method is developed for calculating the characteristics of a laminar boundary layer near a body contour corner point, in the vicinity of which the outer supersonic stream passes through a rarefaction flow. In the study we use the asymptotic solution of the Navier-Stokes equations in the region with large longitudinal gradients of the flow functions for large values of the Reynolds number, the general form of which was used in [1].The pressure, heat flux, and friction distributions along the body surface are obtained. For small pressure differentials near the corner the solution of the corresponding equations for small disturbances is obtained in analytic form.The conventional method for studying viscous gas flow near body surfaces for large values of the Reynolds number is the use of the Prandtl boundary layer theory. Far from the body the asymptotic solution of the Navier-Stokes equations in the first approximation reduces to the solution of the Euler equations, while near the body it reduces to the solution of the Prandtl boundary layer equations. The characteristic feature of the boundary layer region is the small variation of the flow functions in the longitudinal direction in comparison with their variation in the transverse direction. However, in many cases this condition is violated.The necessity arises for constructing additional asymptotic expansions for the region in which the longitudinal and transverse variations of the flow functions are quantities of the same order. The general method for constructing asymptotic solutions for such flows with the use of the known method of outer and inner expansions is presented in [1].In the following we consider the flow in a laminar boundary layer for the case of a viscous supersonic gas stream in the vicinity of a body corner point. Behind the corner the flow separates from the body surface and flows around a stagnant zone, in which the pressure differs by a specified amount from the pressure in the undisturbed flow ahead of the point of separation. A pressure (rarefaction) disturbance propagates in the subsonic portion of the boundary layer upstream for a distance which in order of magnitude is equal to several boundary layer thicknesses. In the disturbed region of the boundary layer the longitudinal and transverse pressure and velocity disturbances are quantities of the same order. In this study we construct additional asymptotic expansions in the first approximation and calculate the distributions of the pressure, friction stress, and thermal flux along the body surface.     

Quasifrozen dusty laminar boundary layer on a blunt body

Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 169–172, November–December, 1990.     

Characteristics of laminar-turbulent boundary layer transition on a cone

The effect of the unit Reynolds number and the Mach number on the transition on a slender circular cone is experimentally investigated. The perturbation spectra in the boundary layer on the cone are measured. It is shown that the location of the transition is determined by the perturbation level at the frequencies causing transition.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 23–27, November–December, 1985.     

Similar laminar boundary layers in incompressible micropolar fluids

Summary A search for similar solutions reveals as only possible similar boundary layer flow in micropolar fluids the flow near a stagnation point. The corresponding equations have been solved numerically by means of a shooting method. Consideration is given not only to the coupling parameterC ₁ and the microdiffusivity parameterC ₂ but also to the microinertia parameterC ₃. It is shown that macroscopic properties of steady boundary layer flows are not very much affected by these parameters, while the microrotation and therefore the inner structure of the layer is very sensitive to all three parameters. These properties of the microstructure can become important in certain unsteady flow problems; then also the macroscopic behaviour may be different to the behaviour of Newtonian fluids.

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Zusammenfassung In der vorliegenden Untersuchung wird gezeigt, daß ähnliche Grenzschichten in mikropolaren Flüssigkeiten nur in der Nähe eines Staupunkts existieren. Die zugehörigen gewöhnlichen Differentialgleichungen werden mit einem Einschießverfahren numerisch gelöst. Neben dem KopplungsparameterC ₁ und dem MikrorotationsparameterC ₂ wird dabei auch der Einfluß der Mikroträgheit im ParameterC ₃ berücksichtigt. Es zeigt sich, daß diese Parameter die makroskopischen Eigenschaften stationärer Grenzschichtströmungen relativ wenig beeinflussen, während sich die Mikrorotation und damit die innere Struktur der Grenzschicht mit diesen Parametern sehr stark ändern kann. Man kann vermuten, daß diese Eigenschaften mikropolarer Flüssigkeiten bei instationären Vorgängen durchaus auch im makroskopischen Verhalten zu größeren Abweichungen gegenüber newtonschen Flüssigkeiten führen können.

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With 6 figures and 1 table     

Vortex stretching in a laminar boundary layer flow

 A new technique to produce controlled stretched vortices is presented. The initial vorticity comes from a laminar boundary layer flow and the stretching is parallel to the initial vorticity. This low velocity flow enables direct observations of the formation and destabilization of vortices. Visualizations are combined with quasi-instantaneous measurements of a full velocity profile obtained with an ultra-sonic pulsed Doppler velocimeter. Several modes of destabilization are observed and include pairing of two vortices, hairpin deformation, and vortex breakdown into a coil shape. Received: 3 April 1996/ Accepted: 4 October 1996