Forced convection heat transfer from a heated circular cylinder with arbitrary surface temperature distributions

A Fredholm-type boundary integral expression for evaluation of the forced convection heat transfer from an object with arbitrary surface temperature distributions is proposed. The Fredholm kernel function for a heated circular cylinder was calculated by numerical simulation of the forced convection fields, and then generalized heat transfer coefficients for arbitrary surface temperature distributions were defined. By use of the generalized heat transfer coefficients, it is shown that the difference in local heat transfer characteristics between the case of an isothermal cylinder and that of a uniform heat flux one can be interpreted only as the difference of the surface temperature distributions. Moreover, the mechanism of the effect of the surface temperature distribution on the characteristics of forced convection heat transfer from a cylinder is clarified in detail through the generalized heat transfer coefficients. © 1999 Scripta Technica, Heat Trans Asian Res, 28(6): 484–499, 1999     

Determination of dynamic pressure on infinite piezoelectric hollow cylinder from electric potential difference measurement

An analytical method is developed for evaluating the dynamic pressure acted at the surface of infinite piezoelectric hollow cylinder by measuring the electric potential difference between the internal and external surfaces. By virtue of the separation of variables method and the orthogonal expansion technique, the inverse boundary problem is transformed to a second kind Volterra integral equation about the unknown dynamic pressure. The interpolation method is employed to solve the integral equation and the dynamic pressure is determined. The present method is suitable for the hollow cylinder with arbitrary thickness subjected to arbitrary dynamic pressure. Numerical experiments are also presented.     

TRANSIENT THERMOELASTIC CONTACT STRESS IN A SHORT-LENGTH CIRCULAR CYLINDER

This paper is a treatment of a transient thermoelastic contact problem in a short-length circular cylinder, to which a heated rigid band is bonded. The problem may be reduced to that of solving dual-series equations. The solution meets the boundary conditions on both the lateral surface and the plane ends of the cylinder. The radial, hoop, and axial stresses have singularities at the end of a rigid band on the cylindrical surface.     

A mathematical model for atmospheric ice accretion and water flow on a cold surface

A mathematical model is developed to describe ice accretion and water flow on a cold substrate of arbitrary shape. It is shown how the model may be applied to practical substrate shapes, such as flat surface, cylinder and aerofoil. A numerical scheme to solve the governing equations is then described. Results are presented for an aerofoil under conditions appropriate to in-flight icing and for a cylinder in conditions for atmospheric icing.     

Magneto-Thermo-Elastic Stresses Induced by a Transient Magnetic Field in a Conducting Hollow Circular Cylinder

We investigate the dynamic and quasi-static behavior of magneto-thermo-elastic stresses induced by a transient magnetic field in a conducting hollow circular cylinder. A transient magnetic field defined by an arbitrary function of time acts on the outer surface of the hollow cylinder and parallel to it. The fundamental equations of plane axisymmetrical electromagnetic, temperature and elastic fields are formulated, and solutions for the magnetic field, eddy current, temperature change and dynamic and quasi-static solutions for stresses and deformations are analytically derived in terms of the arbitrary function. The stress solutions are determined to be sums of a thermal stress component caused by eddy current loss and a magnetic stress component caused by the Lorentz force. The case of a magnetic field defined by a smoothed ramp function with a sine-function profile is examined in particular, and the dynamic and quasi-static behavior of the stresses and deformations are numerically calculated.     

Film condensation with lateral mass flux about a body of arbitrary shape in a porous medium

Under an appropriate distribution of lateral mass flux at the boundary, similarity solution is obtained to the problem of film condensation in a porous medium along the surface of a body of arbitrary shape. The thickness of the liquid layer, the temperature profiles, and the Nusselt number are calculated. It is found that the results depend strongly on the lateral mass flux at the boundary.     

TRANSIENT THERMOELASTIC SOLUTION OF A MULTILAYERED ORTHOTROPIC HOLLOW CYLINDER FOR AXISYMMETRIC PROBLEMS

The thermoelastic dynamic solution of a multilayered orthotropic hollow cylinder in the state of axisymmetric plane strain is obtained. By the method of superposition, the displacement is divided into two parts: one is quasi static and the other is dynamic. The quasi-static solution is derived by the state-space method, and the dynamic solution is obtained by the separation-of-variables method coupled with the initial parameter method as well as the orthogonal expansion technique. The present method is suitable for a multilayered orthotropic hollow cylinder consisting of arbitrary layers and subjected to arbitrary axisymmetric thermal loads. Numerical results are finally presented and discussed.     

ANALYTICAL SOLUTION OF A PYROELECTRIC HOLLOW CYLINDER FOR PIEZOTHERMOELASTIC AXISYMMETRIC DYNAMIC PROBLEMS

By virtue of the separation of variables technique, the piezothermoelastic axisymmetric dynamic problem of a pyroelectric hollow cylinder is transformed to a second kind of Volterra integral equation about a function with respect to time, which can be solved successfully by means of the interpolation method. Then the solution of displacements, stresses, electric displacements, and electric potential are obtained. The present method is suitable for a pyroelectric hollow cylinder with an arbitrary thickness subjected to arbitrary thermal loads. Numerical results are presented.     

Thermal boundary condition effects on forced convection heat transfer

We propose a numerical solution of an adjoint problem of forced convection heat transfer to evaluate the mean heat transfer characteristics under arbitrary thermal boundary conditions. Using the numerical solution of the adjoint problem under the Dirichlet condition, which can be computed by slightly modifying a conventional heat transfer code, we obtain an influence function of local surface temperature on total heat transfer. As a result, the total heat transfer for arbitrary surface temperature distributions can be calculated by the influence function. Similarly, using the numerical solution of the adjoint problem under the Neumann condition, we can also obtain an influence function of the local heat flux on the mean surface temperature. The influence functions for a circular cylinder and for an in-line square rod array are presented to illustrate the capability of this method. © 1999 Scripta Technica, Heat Trans Asian Res, 28(3): 227–238, 1999     

An Experimental Study of the Drag Force on a Cylinder Exposed to an Argon Thermal Plasma Cross Flow

Experimental data are presented concerning the drag force on a cylinder exposed to an argon plasma cross flow with temperatures about 10~4 K and velocities about 10~2m/s. Using a method of sweeping a cylindrical probe across an argon plasma jet, the total drag force on the cylinder can be measured as a function of the lateral distance of cylindrical probe with respect to the plasma-jet axis. Through the Abel inversion, the drag force for per unit of cylinder length and thus the drag coefficient of cylinder have been measured under plasma conditions and compared with the values obtained from the standard drag curve of the cylinder in an isothermal flow. Experimental results show that the measured drag forces are always less than their counterparts read from the standard drag curve with the same Reynolds numbers based on the oncoming plasma properties. The drag force on the cylinder exoposed to a thermal plasma flow is shown to be approximately proportional to the square root of cylinder diameter in the present experiment and it increases slightly with increasing surface temperature of the cylinder. It is also shown that applying a voltage between the drag probe and the anode of the plasma jet generator has little effect on the drag force of cylinder under the experimental conditions. The drag force on a cylinder with finite length exposed to an argon plasma with the axis parallel to the plasma jet is independent of ratio of cylinder length to its dismeter L/d for the cases when L/d≤1.     

ON THE BEHAVIOR OF STEADY TIME-HARMONIC OSCILLATIONS IN THERMOELASTIC MATERIALS WITH VOIDS

We study the spatial behavior in a cylinder made of an isotropic and homogeneous thermoelastic material with voids when it is subjected to plane boundary data varying harmonically in time on its lateral surface and on one of the bases. For oscillations with an angular frequency lower than a critical frequency, we show that some appropriate measures associated with the amplitude of the vibration decays exponentially with the distance to the bases.     

Periodic heat conduction in a solid homogeneous finite cylinder

Analytic solution of the steady periodic, non-necessarily harmonic, heat conduction in a homogeneous cylinder of finite length and radius is given in term of Fourier transform of the fluctuating temperature field. The solutions are found for quite general boundary conditions (first, second and third kind on each surface) with the sole restriction of uniformity on the lateral surface and radial symmetry on the bases. The thermal quadrupole formalism is used to obtain a compact form of the solution that can be, with some exception, straightforwardly extended to multi-slab composite cylinders. The limiting cases of infinite thickness and infinite radius are also considered and solved.     

直喷式柴油机缸内气体运动模拟

本文应用任意拉格朗日－欧拉法对直喷式柴油机缸内气体运动进行了数值模拟。此方法采用可按规定速度运动的任意四边形网格单元。     

Unsteady Forced Convection Heat Transfer Over a Semicircular Cylinder at Low Reynolds Numbers

An unsteady two-dimensional numerical simulation is performed to investigate the laminar forced convection heat transfer for flow past a semicircular cylinder in an unconfined medium. The Reynolds number considered in this study ranges from 50 to 150 with a fixed Prandtl number (Pr = 0.71). Two different configurations of the semicircular cylinder are considered; one when the curved surface facing the flow and the other when the flat surface facing the flow. Fictitious confining boundaries are chosen on the lateral sides of the computational domain that makes the blockage ratio B = 5% in order to make the problem computationally feasible. A finite volume-based technique is used for the numerical computation. The flow and heat transfer characteristics are analyzed with the streamline and isotherm patterns at various Reynolds numbers. The dimensionless frequency of vortex shedding (Strouhal number), drag coefficient, and Nusselt numbers are presented and discussed. Substantial differences in the global flow and heat transfer quantities are observed for the two different configurations of the obstacle chosen in the study. It is observed that the heat transfer rate is enhanced substantially when the curved surface is facing the flow in comparison to the case when the flat surface is facing the flow.     

Fractional Order Thermoelastic Problem for an Infinitely Long Solid Circular Cylinder

In this study, we consider an infinitely long solid circular cylinder, whose lateral surface is traction free and subject to a known surrounding temperature. The problem is in the context of the fractional order thermoelasticity theory. The medium is assumed to be initially quiescent. The solution is obtained by a direct approach without the customary use of potential functions. Laplace transform technique is used to obtain the general solution for any set of boundary conditions. The inversion process is carried out using a numerical method based on Fourier series expansions. Numerical results are given and represented graphically.     

Effect of stochastic thermal input on elastic and thermal properties of an infinitely long annular cylinder

Random elastic and thermal properties for an infinitely long solid conducting circular cylinder are investigated under the effect of random thermal input. The problem is considered in the context of a generalized thermoelasticity theory with one relaxation time. The lateral surface of the solid is traction free and subjected to known stochastic temperature, driven by an additive Gaussian white noise. Laplace transform technique is used to obtain the solution in the transformed domain. Statistically, we derive and analyze the mean and variance for temperature, displacement and stress. Numerical inversion of the transformed solution is carried out, represented graphically and discussed.     

Experimental study of convective heat transfer on a finned rotating cylinder

In this study, the local convective heat transfer from a rotating finned cylinder to the surrounding air was evaluated using an infrared thermographic experimental set up. Solving the inverse conduction heat transfer problem allows the local convective heat transfer coefficient to be identified. We used the specification function method, along with spatio-temporal regularization, to develop a model of local convective heat transfer in order to take lateral conduction and 2D geometry into account. This model was tested using rotational Reynolds numbers (based on the cylinder diameter and the peripheral speed) between 4300 and 17 900. The local heat transfer on the fin surface was analyzed to determine the influence of the rotational Reynolds number and the influence of the height and spacing of the fins. In this paper, we propose an efficiency definition that allows the optimal geometrical configuration of the finned cylinder to be identified for the given operating conditions.