Day-long origin-destination (OD) demand estimation for transportation forecasting is advantageous in terms of accuracy and reliability because it is not affected by hourly variations in the OD distribution. In this paper, we propose a method to estimate the time coefficient of day-long OD demand to estimate hourly OD demand and to predict hourly traffic for urban transportation planning of a large-scale road network that lacks discrete-time rich traffic data. The model proposed estimates the time coefficients from observed link flows given a proven day-long OD demand based on a bilevel formulation of the generalized least square and semidynamic traffic assignment (OD-modification approach). The OD-modification approach is formulated as a static user-equilibrium assignment with elastic demand, based on the residual demand at the end of each period. Our model does not require setting many parameters regarding the OD demand matrices and the discrete-time dynamic traffic assignments. Applying the model to large-scale road network demonstrates that it efficiently improves estimation accuracy because the 24-hour time coefficients of survey data are slightly biased and may be modified properly. In addition, the methods that partially relax the assumption of OD-modification approach and transform the estimated demand into demand based on departure time are examined.

Laminar/turbulent flows of compressible fluid in micro-tubes were simulated to investigate the effect of compressibility on local pipe friction factor. The numerical procedure based on arbitrary-Lagrangian-Eulerian method solves compressible momentum and energy equations. The Lam-Bremhorst Low-Reynolds number turbulence model was adopted to calculate eddy viscosity coefficient and turbulence energy. The computations were performed for a wide range of Reynolds number and Mach number including laminar/turbulent choked flows. It was found that in laminar regimes the ratio of the Darcy friction factor to its conventional (incompressible flow's) value is a function of Mach number. The same thing is observed for the Fanning friction factor. On the other hand, in turbulent regimes, the ratio is still a function of Mach number for the Darcy friction factor but takes about unity for the Fanning friction factor. These facts can be seen in choked flows. The correlation between Darcy friction factor and Fanning friction factor was found to be a function of only Mach number, when adiabatic flow is assumed. Prediction of static pressure distribution and Reynolds number (mass flow rate) using modified one dimensional theory is introduced.

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Laminar/turbulent flows of compressible fluid in microtubes were simulated numerically to obtain the effect of compressibility on the local pipe friction factors. For gaseous flows, the effect of compressibility had not been clarified except for laminar flow whose Mach number is less than 0.45, so the present work extended this to handle higher speed flows including choked ones and turbulent flows. The numerical procedure based on arbitrary-Lagrangian-Eulerian method solves two-dimensional compressible momentum and energy equations. The Lam-Bremhorst Low-Reynolds number turbulence model was adopted to calculate eddy viscosity coefficient and turbulence energy. The physical domain of simulation with the back region downstream from the outlet of the micro-tube was used to be able to calculate the case of under-expansion flow in the tube. The orthogonal curvilinear grid was used for the computational mesh to obtain accurate results. The computations were performed for a wide range of Reynolds number and Mach number including laminar/turbulent choked flows. It was found that in laminar regimes the ratio of the Darcy friction factor to its conventional (incompressible flow’s) value is a function of Mach number and the same goes for the Fanning friction factor. On the other hand, in turbulent regimes, the ratio is still a function of Mach number for the Darcy friction factor but is equal to about unity for the Fanning friction factor. Namely, the Fanning friction factor of gaseous flow in micro-tubes coincides with Blasius formula, even when Mach number is not small and compressibility effect appears. This fact can be seen in choked flow.

A finite volume method (FVM) on distorted meshes for discretizing the energy equation's conduction term is presented. In this method, it is possible to compose the computational mesh of general quadrilateral elements (cells), namely, the cells are not required to be rectangular. The gradient of temperature on the cell's surface is computed to be second‐order accurate. Therefore, the error of numerical results by this method is smaller than using the traditional multilateral element method (MEM). The error does not depend on the degree of mesh distortion. The formulation based only on Taylor's theorem is straightforward. These are advantageous features to revise the fluid flow computation programs (based on FVM) that neglected the heat conduction term of the energy equation. The test calculations show that the convergence tendency of the numerical error using this method with the distorted mesh is the same as using an ordinary 2‐node central difference scheme on a constant‐interval rectangular mesh. By this method a conduction term was added to the energy equation of a SALE [1] program which had neglected that term originally, and z numerical calculation of a fluid flow with a heat transfer problem was performed. The numerical result of the present method with the distorted mesh well agrees with the analytical solution and the result of REM with a rectangular mesh. © 2011 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library (wileyonlinelibrary.com/journal/htj). DOI 10.1002/htj.20375

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