Explicit algebraic models for turbulent flows with buoyancy effects
2013 (English)Report (Other academic)
An explicit algebraic model for the Reynolds stresses and turbulent heat fluxis presented for turbulent parallel shear flows in which buoyancy forces arepresent. The derivation is based on a model framework for two-dimensionalmean flows that was already presented in a previous work (Lazeroms et al.2013), and new test cases are investigated here. The model is formulated interms of the Reynolds-stress anisotropy and a normalized heat flux, which areexpanded as a linear combination of appropriate basis tensors. The coefficientsin this expansion can be found from a system of 18 linear equations. Thisformulation is complemented with a nonlinear equation for a quantity relatedto the total production-to-dissipation ratio, the solution of which is modelledwith an appropriate expression. Fully explicit model expressions are found fortwo fundamentally different flow geometries: a horizontal channel for whichthe temperature gradient is aligned with gravity, and a vertical channel wherethe temperature gradient and gravity are perpendicular. In the first case, weconsider both stable and unstable stratification, while in the second case, bothmixed and natural convection flows are investigated. Comparison with DNSdata shows that the model gives predictions that are substantially better thanstandard eddy-viscosity/eddy-diffusivity models.
Place, publisher, year, edition, pages
Fluid Mechanics and Acoustics
IdentifiersURN: urn:nbn:se:kth:diva-122473OAI: oai:DiVA.org:kth-122473DiVA: diva2:622619
QC 201507012013-05-222013-05-222015-07-01Bibliographically approved