Tsung-Yen Na

Flow of a viscoelastic fluid over a stretching sheet

This paper presents a study of the flow of an incompressible second-order fluid past a stretching sheet. The problem has a bearing on some polymer processing application such as the continuous extrusion of a polymer sheet from a die.

A note on the falkner-skan flows of a non-newtonian fluid

Abstract Non-similar solutions are established for the boundary layer flow of a homogeneous incompressible fluid of second grade past a wedge placed symmetrically with respect to the flow direction. The variation of the skin-friction with respect to the non-Newtonian parameters is discussed.

Laminar natural convection over a frustum of a cone

The problem of laminar, natural convection flow over a vertical frustum of a cone is treated in this paper. The thermal boundary condition at the wall include both the constant wall temperature and the constant wall heat flux cases. The governing differential equations are solved by a combination of quasilinearization and finite-difference methods. Numerical solutions are obtained for a range of Prandtl numbers. The solutions are found to approach to the solutions for a full cone if the flow is far downstream or the radius of the cross-section at the leading edge is very small.

Natural convection flow of a non-Newtonian fluid between two vertical flat plates

SummaryThe natural convection of a homogeneous incompressible fluid of grade three is investigated between two infinite parallel vertical plates. The effect of the non-Newtonian nature of fluid on the skin friction and heat transfer are studied.

Natural convection over a vertical wavy frustum of a cone

Abstract The effects of wavy surfaces on natural convection over a vertical frustum of a cone is studied in this paper. We consider the boundary-layer regime where the Grashof number Gr is very large and assume that the wavy surface have O(1) amplitude and wavelength. The transformed boundary layer equations are solved numerically using the Keller-box method. Detailed results for the local Nusselt number and wall temperature are presented for a selection of parameter sets consisting of the wavy surface amplitude, half cone angle and Prandtl number.

Free convection flow past a vertical flat plate embedded in a saturated porous medium

Abstract A numerical solution for the free convection flow past a vertical semi-infinite flat plate embedded in a highly saturated porous medium by allowing the plate to have a non-uniform temperature or a non-uniform heat flux distributions has been developed. Both local heat transfer rate and excess surface temperature as a function of the distance along the plate are tabulated for a few cases of prescribed wall temperature and heat flux distributions. Such tabulations serve as a reference against which other approximate solutions can be compared in the future.

Numerical solution of natural convection flow past a non-isothermal vertical flat plate

The problem of natural convection over a semi-infinite flat plate with non-uniform wall temperature is studied by using a numerical method. The local rates of heat transfer as a function of the distance along the plate are tabulated for a range of Prandtl numbers (0.01 to 100) and for a few cases of wall temperature distributions. Such tabulations serve as a reference against which other approximate solutions can be compared in the future.

Periodic heat transfer in fins with variable thermal parameters

Periodic heat transfer in a convecting fin with temperature dependent thermal conductivity and coordinate dependent heat transfer coefficient, is analyzed using a perturbation analysis. The zero-order problem, which corresponds to steady-state fin behaviour, is solved by quasilinearization. A method of complex combination is used, in conjunction with a noniterative numerical scheme, to solve the first-order and the second-order problems. The nonlinear nature of the problem gives rise to a nonoscillatory component in the second-order term, which causes a net change in the mean values of temperature and heat transfer rate. The direction of change depends on the thermal conductivity parameter α. For α μ 0, the mean temperature is increased, while the mean heat transfer rate is decreased. For α < 0, the effect is opposite. Detailed results showing the effects of various parameters on temperature distribution, heat transfer rate and time-averaging fin efficiency are presented and discussed.

Heat transfer in turbulent pipe flow based on a new mixing length model

A new model for the heat transfer in turbulent pipe flow is presented based on a modified form of the mixing length theory developed by Cebeci [1] for boundary layer flow problems. The model predicts the velocity and temperature distributions and the Nusselt number for fluids with low, medium and high Prandtl numbers (Pr=.02 to 15) and fits the available experimental data very accurately for values of Reynolds number exceeding 104. Expressions for the eddy conductivity and for the turbulent Prandtl number are presented and shown to be dependent upon the Reynolds number, the Prandtl number, and the distance from the tube wall.

Laminar natural convection over a slender vertical frustum of a cone

The problem of laminar, natural convection flow over a slender frustum of a cone is treated in this paper. The governing differential equations are solved by a combination of quasi-linearization and finite-difference methods. Numerical solutions are obtained for Pr=0.7 and for a range of values of the transverse curvature parameter. It is shown that the effect of transverse curvature is of great significance in such flows.ZusammenfassungIn diesem Bericht ist das Problem der laminaren natürlichen Konvektionsströmung an einem dünnen Kegelstumpf behandelt. Die maßgebliche Differentialgleichung ist durch eine Verbindung von Quasilinearisation und Differenzenverfahren gelöst. Eine numerische Lösung für Pr=0.7 wird für verschiedene Werte eines Krümmungsparameters angegeben. Es ist gezeigt, daß in solchen Strömungen dieser Krümmungsparameter eine große Bedeutung besitzt.