The familiar logarithmic-velocity wall law is often used in the sense that the mean velocity is a function of the wall shear stress τw, the distance from the wall y, the density of fluid ρ and the viscosity of fluid μ. However, the law should be changed to include the pressure gradient in the case of constant τw as well as in the case of vanishing τw. Based on the wall law applicable to finite and vanishing τw, the slip velocity, which is analytic with respect to the pressure gradient and the friction velocity, is proposed in the logarithmic velocity law and the half-power law. The universal constants in the slip velocity are estimated using experimental data.

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A finite-difference procedure is applied to analyse the fully developed laminar flow characteristics in a pipe rotating about a perpendicular axis. We propose a new combination of two parameters of K_L and number R_o as characteristic non-dimensional numbers. The four flow regimes are classified for large and srmall K_L, R_o. We present a numerical formula for friction factor which is valid for wide range of K_L and R_o. The formula agrees well with experimental data.

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Fully developed turbulent flows in a duct of square cross section are numerically simulated by the LES technique using 160, 000 computational grid points. Reynolds numbers based on the bulk velocity and the duct width are 6, 200 and 67, 400. The representative secondary motion near the corner is reasonably reproduced. The near wall behavior of the Reynolds stress and the corresponding pressure field obtained by LES have elucidated the mechanism of the turbulence-driven secondary flow. The essential factor is the rapid attenuation of the turbulence stress due to the wall effect. The pressure distribution, on the other side, has the gradient along the wall. The imbalance between them causes the secondary motion.

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The fully developed turbulent flows in a square duct are predicted with the anisotropic low-Reynolds-number k-ε turbulence model which is valid right up to the wall. Particular attention has been paid to the predictions in both regions close to the corner and the wall, where the experimental measurement is difficult and the numerical predictions are also still not reported. Predicted contours of all three mean velocity components and six Reynolds stresses are in detail compared with previous experimental data. It is found that most features of this flow are simulated excellently by the present anisotropic k-ε model.

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A three-dimensional turbulent boundary layer formed when an initially collateral boundary layer encounters transverse wall motion is calculated using a second-moment closure applicable up to a wall. The numerical solutions are extensively compared with an experiment by Lohmann, including the distributions of all the Reynolds stress components. In the inner layer, the turbulence model produces reasonable shear stress components parallel to the wall. This leads to a good prediction of the magnitude and direction of the wall shear stress. In the outer layer, however, a very rapid growth of the transverse shear stress component found in the experiment is not reproduced by the model. A modification of the redistribution model whose effect is limited to the outer layer in developing flows would be desirable.

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In this work, we report the fractal aspect of iso-velocity sets in the turbulent boundary layer. The iso-velocity sets are one-dimensional point sets defined by an instantaneous velocity signal. We use both a box counting algorithm and a method of the probability distribution function. The analysis is carried out carefully with clarification of the region of scale similarity. Iso-velocity sets clearly indicate fractal features except for near the local mean velocity, and their dimensions vary less than 0.4 in space. Scale similarity extends from the kolmogorov scale to the large eddy scale. Instantaneous turbulent energy fields also show fractal features and have a close connection with iso-velocity sets.

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We have investigated the mechanism of tulip flame formation in a closed vessel by means of numerical analysis. We simulated the unsteady motions of two-dimensional reactive flows using the explicit MacCormack scheme. The numerical model contained compressibility, viscosity, heat conduction, molecular diffusion, reaction, and convection. It was shown in the simulation that the flame is initially convex toward the unburned gas and that a cusp forms at the center of the flame ; then the cusp grows and the tulip-shaped flame forms. The history of flame shapes was qualitatively consistent with the experimental results. It is essential to tulip flame formation that the heat release rate is decreased when the semi-elliptic flame reaches the side walls. The cusp on the flame is caused by this and the flame becomes tulip shaped. The growth of the cusp can be explained by the flame close to the wall running faster because of much consumption of the unburned gas and by the hydrodynamic instability of premixed flame fronts.

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A higher order method of lines is devised for the numerical simulation of two-dimensional shear layers. The spatial derivatives of the Navier-Stokes equations are discretized by means of the modified differential quadrature (MDQ) method. The resulting system of ordinary differential equations in time is then integrated by the Runge-Kutta-Gill (RKG) scheme. The elliptic (Poisson) equation is solved by means of a new variable order multigrid method. The numerical simulations of roll-up and pairing (2-eddy and 4-eddy) cases are carried out with 8th order of spatial accuracy. The numerical solutions suggest that the present higher order method is possible to simulate the vortex motions, i. e., roll-up and pairing.

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The objective of this paper is to clarify the effect of the spanwise wavelength of an initial disturbance on the secondary instability of mixing layers. To achieve this purpose, we have performed a direct numerical simulation of a three-dimensional mixing layer using a spectral method. The results are reported for the case of an initial hyperbolic tangent velocity profile with periodic excitation. From these results, we have obtained the following conclusions : 1) streamwise and transverse velocity fluctuations are slightly affected by the initial spanwise wavelength ; 2) spanwise velocity fluctuation and streamwise vorticity reflect the effect of the initial spanwise wavelength ; and 3) the spanwise perturbation that has the wavelength equal to one-third of the streamwise wavelength has the maximum growth rate.

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The transition mechanism in a plane wake was studied by means of direct numerical simulations. The incompressible time-dependent Navier-Stokes equations were solved using finite difference method in the streamwise direction, pseudospectral Fourier method in the cross-stream direction, and a third-order compact Runge-Kutta scheme for time advancement. The unstable eigenfunctions of the Orr-Sommerfeld equations were used to perturb the Gaussian inlet profile. The numerical methods applied to the spatially developing wake, as well as, the time developing wake, are described in this paper. The numerical results reveal that the phase jitter around the fundamental frequency plays a critical role in generating vortices of random shape and spacing, so does an effective acceleration to the turbulent wake.

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The backward-facing step flow that has many applications in engineering was calculated by directly solving the Navier-Stokes equation using the third-order upwind finite-difference scheme. First of all, the influence of mesh sizes on the numerical results was studied by comparison with the experimental results, and the appropriate mesh sizes were determined. Next, the calculated results with three different step ratios were compared with the experimental results by hot-wire anemometer and flow visualization. These results showed good agreement. The vortex development in the recirculation zone behind the step was clarified by the calculated results and the experimental results.

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Investigation of the copability of the large eddy simulation (LES) for the application of practical problems and the basic study of turbulence is necessary. In order to extend the capability of the LES for more complex flow fields, we have already studied the artificial wall boundary condition to the LES which is based on the two-layer model. In this paper, the artificial wall boundary condition for the LES using the generalized velocity law of the wall expressed by the wall coordinates was constructed. This wall boundary condition is adapted to the plane channel flow and the availability of this method is checked. If Spalding's law of the wall is used, the computational mean velocity profiles are not so much affected by the grid resolution in the direction normal to the wall. The effects of the grid resolution appear in the GS turbulent intensities, but these effects are limited to near the wall only.

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The Smagorinsky model is the most popular and useful subgrid-scale (SGS) model of the large eddy simulation (LES). In previous studies of the LES, the Smagorinsky model with the constant coefficient C_s has been applied to several flow fields. Because there are various scales of turbulence, it is difficult to describe the engineering-type flow fields by using a constant Smagorinsky coefficient. Recently, improvement of the SGS model was made by considering C_s in the Smagorinsky model as the nonconstant coefficient. The SGS length scale variation was studied by Yoshizawa, and the form of variable C_s was presented from a statistical analysis. In this paper, this SGS model was optimized in both the decay of isotropic turbulence and the plane channel flow turbulence simultaneously, and an attempt to construct the new SGS model as the more universal Smagorinsky model was mode.

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Three-dimensional incompressible laminar and turbulent flows within a curved square duct are analyzed by using momentum equations in the physical component tensor form with a finite volume method for a boundary-fitted coordinate system. The solution algorithm is the SIMPLE method applied to the curvilinear coordinate. The closure of Reynolds equations is made by the standard two equation k-ε model. The use of equations by the physical component tensor form gives the superior accuracy for the analysis and the easier treatments for boundary conditions than by the semi-Cartesian form equations. The results are compared not only with the experimental data of an open literature but also with the results by a different method employing the semi-Cartesian form equations with a non-staggered grid system. In these comparisons, the solutions by the present method were in better agreement with the experimental data than those by the other method.

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A numerical scheme for analyzing the unsteady two-dimensional incompressible viscous flow using a general curvilinear coordinate grid is proposed. In this scheme, the unsteady Navier-Stokes equations are solved by a convective-difference scheme using a staggered square grid in transformed space and an interpolation formula considering TVD concept. And an elliptic equation of pressure is solved by the iteration scheme. The continuity condition in the scheme is identically satisfied and the spurious errors are completely removed by the similar manner to the MAC scheme. As numerical examples square cavity, U-type duct and backward-facing step duct flows were calculated. The calculated results show that the scheme has a good accuracy as a second-order scheme and is stable for the high Reynolds numbers flows.

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The difficulty of numerical analysis for high Reynolds flow is due to non linearity of the convective term in the Navier-Stokes equation. To resolve the difficulty, some methods of discretization of the convective term, such as the QUICK method, QUICKEST method and third-order upwind difference method, have been proposed. In this paper, the root mean square error and the artificial damping of the potential are discussed by solving the three-dimensional advection equation, i.e., the rotating sphere problem.

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Incompressible viscous flow in a three-dimensional cubic cavity is studied by the finite difference method. The marker and cell (MAC), the simplified MAC (SMAC), and the highly simplified MAC (HSMAC) methods are applied to calculate the pressure field. All spatial derivatives in the Navier-Stokes equation are approximated by central difference, and the Euler forward scheme is used to integrate time-dependent terms. The staggered mesh system is employed in this calculation. As a result, the difference of the solution methods for the pressure in three-dimensional calculation affects pressure distribution and velocity distribution in a cubic cavity, which is different from the effect by two-dimensional calculation.

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Since free surface flows are seen in nature phenomena and artificial systems, the analysis for these flows has been more important in mechanical engineering. However, theoretical analyses are almost impossible because the boundary conditions are nonlinear equations in analyzing the free surface flows. Thus, numerical analyses are needed. Finite element method (FEM) which can be used for unstructured grid can easily treat boundary conditions. Thus, FEM is used in many technological fields. In this thesis, free surface flow problems were analyzed using the finite element method. In solving these problems, an arbitrary Lagrangian-Eulerian (ALE) kinematical description of the fluid domain was adopted, in which the nodal point can be displaced independently of the fluid motion. The ALE method was introduced into the Generalized Simplified Marker and Cell (GSMAC) method. Damping out the alternating errors was examined in this scheme.

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A simple finite-element method for incompressible viscous flow is presented. This method is a simplified version of the GSMAC finite-element method, and it is applicable to large systems. Navier-Stokes equations in rotational form and the equation of continuity are employed as the governing equations. A time dependent solution is obtained by the following procedures. (1) Prediction of velocity field by explicit time advancement. (2) Correction of both velocity and Bernoulli function by simultaneous relaxation satisfying the equation of continuity. Unsteady flow in a lid-driven cubic cavity at the Reynolds number of 5000 is numerically investigated to verify the present method. Velocity profiles in the cavity are in good agreement with the experimental results by Prasad. The present method is stable in three-dimensional analysis and non physical pressure oscillations are not observed.

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A new finite-element formulation, the high-speed GSMAC-FEM (generalized simplified marker and cell finite-element method), for incompressible viscous flow analysis is developed. The high-speed GSMAC-FEM is a stable and cost-efficient FEM method. The spatial discretization is simplified by a lumped mass matrix and 1-point quadrature. The wiggles are suppressed effectively by hourglass matrices and its effective coefficients which are adjusted to element shapes. Moreover, a new time marching algorithm which requires less effort to satisfy the continuity equation is applied. The time marching algorithm is an extension of the well-known HSMAC-FDM (highly simplified marker and cell finite difference method), and the algorithm runs more than twice as fast as the HSMAC time marching algorithm. The performance of the high-speed GSMAC-FEM scheme is examined by the analysis of the two-dimensional lid-driven cavity flow, and of the flow around circular cylinder. Last of all, one of the applications of the high-speed GSMAC-FEM with the k-ε turbulence model, i.e. the flow around a cube in a turbulent stream, is demonstrated.

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The computational technique cannot serve as a convenient tool for fluid-dynamical problems until the time-consuming processes are removed from the computations. This situation motivates the authors to propose an improved adjustment of the relaxation factor for solving the elliptic difference equations of fluid dynamics. This paper is an attempt to design a model reference adaptive controller for the efficient iterative solver of Au=b, investigating the influence of the choice of error norms on the iteration stopping criterion. The Dirichlet problem of Poisson's equation and the two-dimensional driven cavity flow will be examined to demonstrate the efficient function of the present adaptive controller.

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The cellular automaton method, which can generate the Navier-Stokes equation, is expected to be an effective technique for simulating fluid motion numerically. Because of its complete discreteness, this method has the advantage of implementing the statistical mechanical property of fluid motion through use of the specially designed massive parallel hardware. The present paper aims at representing the boundary conditions of the inflow-outflow, the rigid walls and the moving walls using the cellular automaton concepts. The boundary conditions approximated in this paper will be applied to calculate Poiseuille flow, Couette flow, the cavity flow and von Karman street problem. The present microscopic expression of the boundary conditions to the cellular automaton model of fluid dynamics will describe the reasonable alternative to the traditional macroscopic boundary conditions. Then computational efficiency of vectorization and parallelism for the present algorithm of the collision process in the model will be examined by several flow problems.

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The cellular automaton method has been intensively applied computational fluid dynamics because of its advantages of representing the statistical mechanical property of fluid flow on massive parallel computers. The present paper focuses on describing the thermally driven phenomena by means of using the multiparticle model and on demonstsrating the Benard-convection problem as a numerical experiment. It also aims at examining the vectorized and parallelized algorithm for the mini-supercomputers to calculate the processes of collisions and translations of a large number of particles in the thermally driven flow.

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The unstructured upwind method is proposed to solve compressible flow with complicated boundaries or an arbitrarily shaped mesh. The flux difference splitting (FDS) scheme and flux vector splitting (FVS) scheme, which are extended to the unstructured grid system, are compared. The Euler equation is discretized by the control volume method. All conserved variables are stored at the cell center. The MUSCL approach for the cell-centered unstructured grid is proposed to obtain higher-order accuracy. A three-stage Runge-Kutta method is used for the time stepping scheme. The present calculation methods are applied to two-dimensional front-facing step flows. The results demonstrate that the present MUSCL approach is effective to obtain high resolution, and the triangular mesh solver is comparable to the uniform orthogonal mesh solver. FDS gives slightly better resolution than FVS.

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A numerical method has been developed for solving the equations of compressible fluids by using the particle method. In our method, the particles move at the acceleration or velocity which is defined for each equation. In addition to the density, the acceleration and the velocity are expressed by the summation of the contribution from each particle, which has a pre-determined amount of a physical attribute. To show the validity of our method, the wave equation, Burgers equation and the equation for a compressible fluid, both with and without a diffusion term, all one-dimensional, are considered. The generation of the shock and expansion waves, the formation of the steady shock wave, and the interactions of the linear waves and of the nonlinear shock waves, are successfully simulated by our method.

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We present a new Monte Carlo simulation procedure which is capable of capturing aggregate structures in a suspension where fine particles are dispersed. The algorithm we call the "cluster-moving" Monte Carlo algorithm involves moving aggregates (clusters) as unitary particles at every certain Monte Carlo step. We discuss here the theoretical background of the cluster-moving Monte Carlo algorithm. The results of simulations for a model system, i.e., magnetic fluids, have shown that the new algorithm produces much more rapid convergence than the conventional one for unstable dispersion systems and reproduces the physically reasonable aggregate structures of fine particles.

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A parallel subdomain technique is proposed for the speedup of the direct-simulation Monte Carlo method (DSMC method, hereafter). The total molecular number in a decomposed domain can be used for the estimation of a processor load balance. Two methods of domain decomposition naturally arise : a static domain decomposition and a dynamic domain decomposition. A simple rarefied gas flow over a flat plate without thickness is simulated by the DSMC method using a parallel computer system with Transputers. By static domain decomposition, the speedup ratio is 3.49, the parallel efficiency 87%, and by dynamic domain decomposition, the speedup ratio is 3.71, the efficiency 93%.

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Parallel computation of thermohydraulic problem is examined using four transputers in array. Geometric and algorithmic parallelisms are tested with Parallel FORTRAN for two-dimensional thermal conduction and cavity flow problems. The speedup ratio and efficiency of the parallel computations are measured in terms of the number of transputers, mesh size and time steps. The results obtained show the geometric parallelism to be more effective than the algorithmic one. This is because the former requires data communication only at domain boundaries while the latter for all of the mesh points. The efficiency of the parallel computation is evaluated for the two-dimensional thermal conduction and compared with the measured values. The speedup ratio and efficiency for a very large parallelism are also estimated.

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A thermal striping phenomenon characterized by a random temperature fluctuation occurs in the region immediately above the fast breeder reactor core due to the temperature difference of the core outlet coolant between subassemblies. Then the random temperature fluctuation applies a thermal stress to in-vessel structures. In this paper, we have investigated the intensity of the temperature fluctuation in water by implementing the algebraic stress turbulence model (ASM) including the second-order momentum of turbulence and the fuzzy controller to determine an optimum time step size in a general-purpose thermohydraulic analysis code. From the analysis, it is concluded that the characteristics of the temperature fluctuation intensity can be estimated efficiently by the ASM.

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This paper presents the renormalization group analysis for the turbulence problem. This procedure does not require any experimentally adjustable parameters. The following numerical values for important constants of turbulent flows can be derived : for instance, the Kolmogorov constant for the inertial-range spectrum Ck=1.605 ; turbulent Prandtl number for high-Reynolds-number heat transfer ; Pt=0.7179 ; A differential k-ε model is derived in the high-Reynolds-number regions of the flow where the algebraic relation ν=0.0846 k²/ε. A differential LES model is also derived, as is the Smagorinsky constant Cs=0.00615.

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The turbulence-generation mechanism in the intake and compression processes of an engine with a square cylinder is investigated by performing a three-dimensional numerical simulation. Emphasis is placed on the influences of the intake turbulence and the compression effect on the TDC turbulence. The compressible Navier-Stokes equations are solved without any explicit turbulence models. The employed numerical algorithm is an extended version of the ICE method, and the third-order upwind scheme is employed for the convective terms. The obtained computational results agreed well with the experimental visualization using freon as the working fluid under the Mach-number condition over 0.5. It is shown that the drastic transition to turbulence near TDC is grasped by computations using this numerical method.

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As a simple model of a large-scale structure in the laminar boundary layer, the development of the disturbance is calculated using a three-dimensional discrete vortex filament method. The filament is stretched by the streamwise velocity and the top region of the disturbance is deformed by the induced velocity. As a result, the velocity profile of the boundary layer is affected by the developing disturbance. The initial disturbance stretches in the downstream direction, the hairpin-shaped structure deforms, and a unique vortex ring pinches out from the top region of the structure.

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In vacuum evaporation processing technologies, the recovery of the evaporated substance is of great importance. The inefficient vapor should be liquefied and collected on the recovery plate, which is located so as to face the vapor source. In this paper, the numerical analysis on the dynamic behavior of a droplet grown to detach from the recovery plate is presented. The liquid was taken to be molten metal, which has a larger surface tension than other commonly used liquids. In the flow analysis with the freely-moving boundary, the numerical model of the surface tension has been of interest. Therefore, in order to analyze the high-deformation phenomena, such as the falling droplet, the instabilities on the boundary should be investigated and treated carefully. Here, the boundary height function was defined by multiple coordinates, which provided an effective method of recognizing the complicated boundary precisely. The experiment using a liquid Bi droplet also demonstrated the validity of this method.

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This paper describes the numerical simulation of the fiber orientation and dispersion for fiberfilled polymer melts in entry and exit flows. First we calculated the viscoelastic flow field of matrix fluids. The higher elastic fluid shows the larger normal stress difference in a die and swells more after extrusion. The velocity profile in the die depends on the shear viscosity, and the shear-thinning viscosity makes the swell smaller. Next we calculated the fiber orientation and dispersion using the velocity fields of the matrix fluids. The fibers tend to array along the streamlines in acceleration flow and perpendicularly to the flow direction in deceleration flow. In the shear flow, the long fibers array along the streamline and the short fibers rotate. The fiber orientation state is less affected by the flow field with increasing interaction between fibers. The fiber dispersion state depends on the inlet boundary of the flow field.

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A numerical analysis is made on the turbulent boundary layers with injection and suction through a slit using the five different turbulent models. The five models are three eddy viscosity models (zero-, one- and two-equation models) and two different types of Reynolds stress model. Published experimental data on the skin friction factor, the mean velocity profiles, and Reynolds stress profiles are used to assess the performance of the model calculations. The applicabilities of these models on the turbulent boundary layers with injection and suction are discussed.

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In the present paper, a new scheme suitable for the schock-boundary layer interaction is proposed and unsteady separated flows around airfoils at high attack angles are investigated numerically. The TVD scheme based on Roe's approximate Riemann solver for the explicit part of the convective term and the block pentadiagonal inverse matrix method based on the upwind difference scheme of the third order for the implicit part of the convective term are employed. The diagonal matrix solver introduced here is very efficient and economical. It is solved by the iterative method to maintain the time accuracy of the second order. This iterative method for the diagonal scheme is very effective in reducing computational effort. As an example, interaction between separated vortices and schock wave is simulated numerically.

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The high-speed GSMAC-FEM (generalized simplified marker and cell finite-element method) is a stable and cost-efficient FEM method for incompressible viscous flow analysis. Using the high-speed GSMAC-FEM, the gas flow and the heat transfer in the moving-bed heat exchanger are analyzed. In the Navier-Stokes equation, Ergun's equation is used for body force which is a drag caused by the small-scale flow around pebbles, and the experimental heat transfer coefficient is used for the computation of heat sink and heat source terms in gas and pebble energy equations, respectively. The analyzed pressure distributions and temperature distributions nearly agree with the experimental results. Using this scheme, a high-efficiency heat exchanger, i.e. heat exchanger with uniform gas flow, can be designed cost-effectively.

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This study dealt with gas flow and heat transfer processes in a packed bed which consisted of capsules containing PCM. The influence of the diameter's ratio of the packed bed to a capsule on maldistribution of gas flow was discussed by numerical simulation. The rate of convective heat transfer in the packed bed was measured and simulated by changing the direction of blowing gas and the sizes of the packed bed. The measured heat transfer coefficient from gas to capsules was remarkably smaller than that estimated by Ranz's equation. Exergy efficiency was also used to optimize the gas flow rate.

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A numerical method was developed to solve three-dimensional incompressible viscous flow in complicated geometries using a domain decomposition technique. Each complicated flow domain was decomposed into several subdomains. Curvilinear coordinates were numerically generated in each subdomain using the boundary-fitted coordinate transformation technique. The method was adopted to solve some benchmark problems. For a two-dimensional cavity flow, the obtained flow velocity distributions agreed very well with the numerical results given by Ghia et al. The calculated flow velocity distributions in a 180°curved pipe were also in good agreement with the experimental ones. The method was applied to the analysis of flows with a large Reynolds number (≒10⁴) in piping elements. The calculations indicated a strong secondary flow and eddy train produced at an elbow. In a diffuser, eddies were found to be produced almost symmetrically with respect to the central axis for a small expansion angle, but the flow pattern became more unsymmetric and unsteady for a larger expansion angle. The insufficient recovery of pressure in the diffuser was found to be caused by the generation of eddies.

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This paper presents an iterative calculation method of computing node pressures and consumptions at all nodes in steady-state pipeline networks by means of a node admittance matrix which is used as an analytical method for topological electrical networks. This method has advantages in that the topological characteristics of the networks are automatically recognized when the node admittance matrix is established according to a simple rule, and the convergence of iterative calculation is always atteained in a wide range of initial values. This paper shows that introduction of a relaxation factor is effective in successfully attaining the convergence. The influence of the relaxation factor on the convergence is also discussed and the practical range of the factor is recommended. The comparison of computed results between the traditional Hardy-Cross method and the method presented herein shows good agreement.

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A three-dimensional analysis method for potential flow with moving liquid surfaces using a boundary element method-(BEM) has been developed. The flow is treated as potential flow and is solved by BEM. The Bernoulli equation is integrated by the Stiffly Stable 3rd algorithm. The structures are modeled by isoparametric shell elements of the finite element method and by Green's strain tensor. The equation of an elastic body is integrated by the Newmark-β method. The equations of flow and structures are alternately solved at each time step.

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Effects of flame stretch and flame curvature on the extinction of turbulent premixed flames in a stagnation point flow have been studied experimentally. A lean propane/air mixture has been used. The bulk stretch rate was varied from 15 s^-1 to 60 s^-1, while the turbulent intensity of velocity fluctuation in the approach flow was varied up to 0.6 m/s. In the near extinction limits, the local stretch rate was estimated by measuring the mean centerline velocity with LDV and the local flame curvature was measured by using the laser tomographic method. The local stretch rate decreases, while the stretch rate due to the local flame curvature increases with increasing turbulent intensity. As a result, it is proposed that the sum of these two stretch rates plays a key role in flame extinction.

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Numerical computations and experiments have been carried out to study heat transfer characteristics in natural convection along a vertical finite-length heated plate of uniform temperature. Numerical results were obtained for the Grashof number in a range of 0.1 to 10⁵ and for the Prandtl number of 0.71. The average heat transfer coefficients were measured for the Grashof number in a range of 50 to 10⁶. The numerical results are in good agreement with the experimental results. The fluid goes up along the plate and it turns near the upper end of the plate because of cooling by the cold surrounding fluid in the upper space. As a consequence, a fluid circulation forms beside the plate. The local heat transfer coefficient is high at both the lower and upper ends of the plate and maitains an almost constant value in the middle portion. The correlations obtained from the numerical and experimental results are as follows : Nu=2.03Gr^0.0221(0.1≤Gr≤4), Nu=1.63Gr<0.178>(4≤Gr≤10⁶).

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Spanwise eddy diffusivity of heat was measured in a flat-plate turbulent boundary layer with a constant spanwise temperature gradient and different intensities of free-stream turbulence. Comparison was made with the usual kinematic eddy viscosity measured in parallel. According to the experimental results, the ratio of these eddy diffusivities is strongly influenced by the free-stream turbulence. However, in the vicinity of the wall, this ratio approaches a certain universal distribution which is independent of the intensity of free-stream turbulence.

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The principle of Sasaki's method for surface-temperature measurement is that the temperature of the measuring junction of a thermocouple indicated by a meter in the couple circuit is the temperature of the surface of a body if the junction temperature has been so adjusted that the meter shows no deflection when the junction makes a brief light contact with the surface. Hence, this method does not sensibly affect the surface conditions, and one can eliminate the main errorproducing factor common to the contact methods of temperature measurement. However, an inevitable bias error occurs because of radiation shielding when a finite-size thermocouple junction is brought close to the wall surface. In the present study, we have analyzed the conjugate heat transfer in a body whose surface temperature is being measured, and have developed a simple equation to estimate the foregoing inherent bias error.

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Computed tomography (CT) essentially assumes that rays such as X-rays propagate straight within the body ; therefore, it is difficult to apply this assumption to bodies which scatter the incident rays. Since the living tissues are very strong light-scattering media, realization of optical-CT scanners is not considered easy, although it is highly desired because of its possible ability to measure the oxygenation states in the body with a noninvasive method. This report shows how optical-CT imaging is possible by the use of time-resolved spectroscopy. The object is a cylindrical scattering medium containing a coaxial small cylinder with both scattering and absorption, while the reference is only the scattering cylinder. The light transmission data are generated by the Monte Carlo method. The temporal variations of the difference in the optical density between the object and reference provide the projection data necessary for the CT reconstruction procedure. The obtained image reflects the profile of the difference in the absorption coefficient between the object and the reference with satisfactory accuracy and spacial resolution.

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Operation factors affecting carbon conversion efficiency were investigated experimentally by using the bench-scale 6 T/D coal gasification test facilities. Factors investigated include : (1) fourteen kinds of coal, (2) enriched oxygen concentration, and (3) the gasifier stoichiometric ratio. Test results were represented individually as the characteristics curves. The combination of the test results and the chemical equilibrium calculation made it possible to predict the operation condition to attain given gasification performance.

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The effects of combustion temperature on the real rate of heat release in combustion of unsteady sprays were investigated with a rapid compression-expansion machine. The total heat loss from gases to the combustion chamber walls was calculated from the measured local heat flux at 11 points on the combustion chamber wall surfaces. In experiments, an oxygen-argon-helium mixture was used instead of air to achieve a high combustion temperature. It turned out that the high combustion temperature yields slower combustion. This result seems to be mainly caused by the slower mixing rate due to the high viscosity of burning gases.

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An experimental study was made to determine the time histories of vapor concentration and its fluctuation in the combustion chamber of a spark ignition engine. Laser Rayleigh scattering was applied for remote, nonintrusive, point probing of the vapor concentration in the combustion chamber, which was caused by the continuous injection of Freon-12 into an intake port. The conventional engine was modified to make the optical diagnostics accessible. The results showed that the concentration fluctuation consisted of a temporal concentration fluctuation in a specific cycle and a cyclic variation of the temporal mean concentration in this particular cycle, which could be separated and measured accurately by the present experimental apparatus. It was also found that the concentration fluctuation increased and reached a peak, after which it decreased during intake and compression strokes. The concentration fluctuation was largely affected by the air fuel ratio and engine speed.

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