Dimensional Stagnation Point Research Articles

Heat and mass transfer at a general three- dimensional stagnation point.

Simultaneous effects of heat and mass transfer on properties of stagnation point flows analyzed over full range of velocity gradients

Some viscous flows of a saturated ferro-fluid under the combined influence of thermal and magnetic field gradients

The purpose of the present investigation is to examine theoretically the magneto-thermomechanical interaction between a flowing, viscous, incompressible, heated ferrofluid and a cold wall in the presence of a spacially varying magnetic field. Specifically, the following two problems are treated: (i) the two dimensional stagnation point flow of a heated saturated ferrofluid against a cold wall under the influence of the magnetic field due to a magnetic doublet located some distance behind the stagnation point and, (ii) the two dimensional parallel flow of a heated saturated ferrofluid along a wall, whose temperature decreases linearly with distance from the leading edge, under the influence of the magnetic field due to two equally directed line currents which are perpendicular to the flow plane and equidistant from the wall. In each of the above cases, the effect of the magneto-thermomechanical interaction on the velocity and temperature boundary layer profiles with the attendant effect on the wall skin friction and heat transfer are analyzed and discussed.

Radiative cooling of a uniform gas flow.

References 1 Neuringer, J. L. and Mclllroy, W., Incompressible two dimensional stagnation point flow of an electrically conducting viscous fluid in the presence of a magnetic field, J. Aerospace Sci. 25,19^-198 (1958). 2 Lykoudis, P. S., On a class of magnetic laminar boundary layers, 1958 Heat Transfer and Fluid Mechanics Institute (Stanford University Press, Stanford, Calif., 1958), p. 176. 3 Rossow, V. J., On flow of electrically conducting fluids over a flat plate in the presence of a transverse magnetic field, NACARept. 1358(1958). 4 Bush, W. B., Compressible flat plate boundary-layer flow with an applied magnetic field, J. Aerospace Sci. 27, 49-58 (1960). 5 Cess, R. D., Magnetohydrodynamic effects upon heat transfer for laminar flow across a flat plate, J. Heat Transfer C82, 87-93 (1960). 6 Wu, J. C., Growth of magnetohydrodyriamic boundary layers, ARS J. 31, 562 (1961). 7 Kauzlarich, J. L. and Cambel, A. B., The momentum integral approximation for compressible magnetogasdynamic boundary-layer flow, J. Appl. Mech. 30, 269 (1963). 8 Hartree, D. R. and Womersley, J. R., A method for the numerical or mechanical solution of certain types of partial differential equations, Proc. Roy. Soc. (London) A161, 353 (1937). 9 Smith, A. M. O. and Clutter, D. W., Solution of the incompressible laminar boundary-layer equations, AIAA J. 1,2002-2071(1963). 10 Jaffe, N. A., Solutions of the magnetofluid-dynamic boundary layer equations for a flat plate with a moving transverse magnetic field source or crossed electric field in the spanwise direction, Douglas Rept. LB-31693 (November 1964). 11 McCune, J. E. and Sears, W. R., On the concepts of moving electric and magnetic fields in magnetohydrodynamics, J. Aerospace Sci. 26, 674-675 (1959).

Axially-Symmetric and Two-Dimensional Stagnation Point Flows of a Certain Visco-Elastic Fluid

A sixth degree profile is used in kármàn-Pohlhausen method for the study of the axially-symmetric flow of a certain single-relaxation-time viscoelastic liquid near a stagnation point, instead of a fourth degree profile used by Sharma. It is found that both the boundary layer thickness and the skin friction decrease with the increase of the viscoelastic parameter-results just the reverse of the corresponding results of the earlier paper, but in agreement with the results of Rathna and Rajeshwari for another model. The reasons for the difference have also been examined. The two dimensional stagnation point flow has also been investigated.

Poisson's Ratio for Honeycomb Sandwich Cores

0.1 0.2 0.3 0.4 0.6 PsMs 0.8 1.0 2.0 constant specific heats, constant Prandtl Number, isothermal wall, and similar boundary-layer profiles. The latter assump­ tion—'that is, that the dimensionless velocity and thermal pro­ files are functions of a single variable—is physically correct at the stagnation line of the cylinder. Values of the heat-transfer parameter obtained from these solutions are plotted in Fig. 1 versus the ratio (psp:s/pw^w) where subscript s now denotes values in the external flow at the stagna­ tion line of the cylinder as well as the stagnation point of a body of revolution. The solutions for /3 = 0.5 and X = 1.0 are applied to a body of revolution by the use of Mangler's transformation relating two- dimensional and axisymmetric flows. Since the Sutherland viscosity formula and constant Prandtl Number are used in reference 1, as well as in the present solutions, the close agreement between the present results for (3 = 0.5 and Eq. (1) indicates that the heat-transfer parameter at a stagnation point is not sensitive to the effects of dissociation on density and specific heat within the boundary layer. For equilibrium disso­ ciation and Lewis Number 1, the heat-transfer rate at a three- dimensional stagnation point can then be calculated from the equation1 qw = VPwfjLw(dUe/dx)s ((hs - hw)/a) (Nu/VRe). (2) where the symbols are those of reference 1, and all quantities are evaluated in the real-gas flow except {Nu/\/Re) which may be obtained from either Eq. (1) or a solution of the boundary-layer equations for a perfect gas with Sutherland's viscosity formula provided that the value of psVs/pwVw applying to the solution is equal to the real-gas value. The heat transfer at the stagnation line of a yawed cylinder is also calculated from Eq. (2) except that hs should be replaced by the adiabatic wall enthalpy given by the equation2 A N INTERESTING mechanical property of honeycomb cores is •^ *• their Poisson's ratio: it is very sensitive to cell geometry and can assume values from zero to about three. Large values may be observed when flexing some slabs of honeycomb with flat cell walls, while rippled-wall honeycombs demonstrate zero Poisson's ratio. The ratio of anticlastic curvatures is indicative of the value of Poisson's ratio for axial loading in the plane of the slab.