Computation of Viscous Incompressible Flows with Heat Transfer Using Godunov-Projection Method

Inspired by the physiological network of insects, which have dimensions on the order of micrometers to millimeters, we study the airflow within a single model insect tracheal tube. The tube undergoes localized rhythmic wall contractions. A theoretical analysis is given to model the airflow within the tracheal tube. Since flow motions at the microscale are dominated mainly by viscous effects, and the tube has radius, R, that is much smaller than its length, L, (i.e. δ = R/L ≪ 1), lubrication theory for axisymmetric, viscous, incompressible flows at low Reynolds number (Re ∼ δ) is used to model the problem mathematically. Expressions for the velocity field, pressure gradient, wall shear stress and net flow produced by the driving tube wall contractions are derived. The effect of the contraction amplitudes, time lag, and spacing between two sequences of contractions on the time-averaged net flow over a single cycle of wall motions is investigated. The study presents a new, insect-inspired mechanism for valveless pumping that can guide efforts to fabricate novel microfluidic devices that mimic these physiological systems. A x-ray image that shows the tracheal network of the respiratory system of an insect (Carabid beetle) and the associated locations of these rhythmic contractions are shown in figure (1) to promote this study.

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Development of High Order LES Solver for Heat Transfer Applications Based on the Open Source OpenFOAM Framework

Volume 5B: Heat Transfer ◽

10.1115/gt2015-43279 ◽

2015 ◽

Cited By ~ 1

Author(s):

Luca Mangani ◽

David Roos Launchbury ◽

Ernesto Casartelli ◽

Giulio Romanelli

Keyword(s):

Heat Transfer ◽

Open Source ◽

Gas Turbines ◽

Incompressible Flows ◽

Stokes Equations ◽

Turbulence Models ◽

Local Heat Transfer ◽

Local Heat ◽

High Order ◽

Computational Time

The computation of heat transfer phenomena in gas turbines plays a key role in the continuous quest to increase performance and life of both component and machine. In order to assess different cooling approaches computational fluid dynamics (CFD) is a fundamental tool. Until now the task has often been carried out with RANS simulations, mainly due to the relatively short computational time. The clear drawback of this approach is in terms of accuracy, especially in those situations where averaged turbulence-structures are not able to capture the flow physics, thus under or overestimating the local heat transfer. The present work shows the development of a new explicit high-order incompressible solver for time-dependent flows based on the open source C++ Toolbox OpenFOAM framework. As such, the solver is enabled to compute the spatially filtered Navier-Stokes equations applied in large eddy simulations for incompressible flows. An overview of the development methods is provided, presenting numerical and algorithmic details. The solver is verified using the method of manufactured solutions, and a series of numerical experiments is performed to show third-order accuracy in time and low temporal error levels. Typical cooling devices in turbomachinery applications are then investigated, such as the flow over a turbulator geometry involving heated walls and a film cooling application. The performance of various sub-grid-scale models are tested, such as static Smagorinsky, dynamic Lagrangian, dynamic one-equation turbulence models, dynamic Smagorinsky, WALE and sigma-model. Good results were obtained in all cases with variations among the individual models.

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Model Order Reduction of Turbulent Mixed Heat Transfer Problems by Projection Method

The International Journal of Multiphysics ◽

10.21152/1750-9548.14.3.301 ◽

2020 ◽

Vol 14 (3) ◽

Keyword(s):

Heat Transfer ◽

Projection Method ◽

Model Order Reduction ◽

Order Reduction ◽

Model Order ◽

Transfer Problems

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