Abstract:
Our recently published papers reporting results of Direct
Numerical Simulation (DNS) of forced convection flows in
porous media suggest that in a porous medium the size of
turbulent structures is restricted by the pore scale. Since the
turbulent kinetic energy is predominantly contained within large
eddies, this suggests that turbulent flow in a porous medium may
carry less energy that its counterpart in a clear fluid domain.
We use this insight to develop a practical model of turbulent
flow in composite porous/fluid domains. In such domains, most
of the flow is expected to occur in the clear fluid region;
therefore, in most cases the flow in the porous region either
remains laminar or starts its transition to turbulence even if the
flow in the clear fluid region is fully turbulent. This conclusion
is confirmed by comparing appropriate Reynolds numbers with
their critical values. Therefore, for most cases, using the
Forchheimer term in the momentum equation and the thermal
dispersion term in the energy equation may result in a
sufficiently good model for the porous region. However, what
may really affect turbulent convection in composite domains is
the roughness of the porous/fluid interface. If particles or fibers
that constitute the porous medium (and the pores) are relatively
large, the impact of the roughness on convection heat transfer in
composite porous/fluid domains may be much more significant
than the impact of possible turbulence in the porous region. We
use the above considerations to develop a practical model of
turbulent flow in a composite porous/fluid domain,
concentrating on the effect of interface roughness on turbulence.
Description:
Papers presented at the 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Portoroz, Slovenia on 17-19 July 2017 .
