COMPUTATION OF BUOYANCY-DRIVEN FLOW IN AN ECCENTRIC CENTRIFUGAL ANNULUS WITH A NONORTHOGONAL COLLOCATED FINITE-VOLUME ALGORITHM

A computational study is performed on two-dimensional mixed convection in an annulus between a horizontal outer cylinder and a heated, rotat ing, eccentric inner cylinder. The computation has been done using a n on-orthogonal grid and a fully collocated finite volume procedure. Sol utions are iterated to convergence through a pressure correction schem e and the convection is treated by Van Leer's MUSCL scheme. The numeri cal procedure adopted here can easily eliminate the 'Numerical leakage ' phenomenon of the mixed convection problem whereby strong buoyancy a nd centrifugal effects are encountered in the case of a highly eccentr ic annulus. Numerical results have been obtained for Rayleigh number R a ranging from 7 x 10(3) to 10(7), Reynolds number Re from 0 to 1200 a nd Prandtl number Pr from 0.01 to 7. The mixed rotation parameter sigm a (= Ra/PrRe2) varies from infinity (pure natural convection) to 0.01 with various eccentricities epsilon. The computational results are in good agreement with previous works which show that the mixed convectio n heat transfer characteristics in the annulus are significantly affec ted by sigma and epsilon. The results indicate that the mean Nusselt n umber Nu increases with increasing Ra or Pr but decreases with increas ing Re. In the case of a highly eccentric annulus the conduction effec t becomes predominant in the throat gap. Hence the crucial phenomenon on whereby Nu first decreases and then increases can be found with inc reasing eccentricity. (C) 1998 John Wiley & Sons, Ltd.