Numerical simulation of heat transfer in a pipe with non-homogeneous thermal boundary conditions

Abstract

Direct numerical simulations of heat transfer in a fully-developed turbulent pipe flow with circumferentially-varying thermal boundary conditions are reported. Three cases have been considered for friction Reynolds number in the range 180-360 and Prandtl number in the range 0.7-4. The temperature statistics under these heating conditions are characterized. Eddy diffusivities and turbulent Prandtl numbers for radial and circumferential directions are evaluated and compared to the values predicted by simple models. It is found that the usual assumptions made in these models provide reasonable predictions far from the wall and that corrections to the models are needed near the wall.

The influence of thermal boundary conditions on turbulent forced convection pipe flow at two Prandtl numbers

“…Note that the wall-normal location is limited to 0 < y + < 180, since for y + > 180 mainly production and dissipation balance [26]. Except for a slightly too low dissipation of the present LES (maximum 7% A more recent simulation for IF by Antoranz et al [31], who applied the same high-order method as the one considered in this work for the same domain size, shows good agreement with the present results also for the peak values of temperature variance and streamwise turbulent heat flux.…”

Analysis free oscillations of a non-homogeneous pipe along's thickness and length, taking into account the resistance of the external environment

“…Let's solve the equation using approximate analytical methods. In the first stage let's use the method of separation into variables, in the next stage Bubnov-Galerkin method [7,8].…”

Extended proper orthogonal decomposition of non-homogeneous thermal fields in a turbulent pipe flow

“…The datasets to be analysed in this paper were generated by direct numerical simulations (DNS) of a fully-developed turbulent pipe flow, with circumferentially-varying heat flux boundary condition. For completeness, we provide here the most important details of the computations; further details can be found in [17].…”

“…Direct numerical simulations of fully-developed turbulent flow and heat transfer in pipes, in which the temperature is regarded as a passive scalar, have been instrumental in understanding the mechanism of turbulent transport in pipes with non-homogeneous thermal forcing. Antoranz et al [17] performed DNS simulations of incompressible flow in pipes with sinusoidal heating on the upper part and adiabatic conditions in the lower part, considering constant fluid properties. The friction Reynolds number (based on the pipe radius) was equal to 180 and 360 and the Prandtl number was equal to 0.7 and 4.…”

“…They found good correlation between the first POD modes of thermal fluctuations and the first modes of the velocity fluctuations, as they were both highly influenced by the wavy wall geometry. In the present work, the dataset of Antoranz et al [17] is analysed with POD and EPOD aiming at a better understanding of the heat transfer problem.…”