A cubic spline spatial fitting is used for spatial interpolation and
a three-point Lagrangian formula for temporal interpolation. The
validation of the FORTRAN code was performed by using a natural
convection problem of a hot cylinder located at the center of a
square enclosure with cold walls. The computational domain is
given by 2.5 2.5, and the coarse grid size by Dxc ¼ Dyc ¼ 0.05, and
the fine grid size by Dxf ¼ Dyf ¼ 0.025. The case of Ra ¼ 104,
Ra ¼ 5 104 and Ra ¼ 1 105 were simulated while the tube
diameter d is given as 1. The averaged Nusselt numbers are 3.20,
4.03, and 4.99, respectively, which are comparable to the data of
3.23, 4.03, and 4.89 obtained by Peng et al. [7]. Fig. 3 shows the
temperature contours and streamline comparison for the case of
Ra ¼ 104. The mesh number dependent test was also performed,
which indicated that 200 200 mesh size for both the coarse and
fine grids has an adequate accuracy for the present problem.
Therefore the following numerical results are those having the
mesh numbers of 200 200 for both the coarse and fine grids. In
order to make a comparison with the experimental data, we adjust
the non-dimensional relaxation times of sf and sg, so that the
Prandtl number is about 3.53, which is approximately equal to the
value of water at temperature of 50 C.
Fig. 1. The geometry configuration of the numerical model.
Fig.
A cubic spline spatial fitting is used for spatial interpolation anda three-point Lagrangian formula for temporal interpolation. Thevalidation of the FORTRAN code was performed by using a naturalconvection problem of a hot cylinder located at the center of asquare enclosure with cold walls. The computational domain isgiven by 2.5 2.5, and the coarse grid size by Dxc ¼ Dyc ¼ 0.05, andthe fine grid size by Dxf ¼ Dyf ¼ 0.025. The case of Ra ¼ 104,Ra ¼ 5 104 and Ra ¼ 1 105 were simulated while the tubediameter d is given as 1. The averaged Nusselt numbers are 3.20,4.03, and 4.99, respectively, which are comparable to the data of3.23, 4.03, and 4.89 obtained by Peng et al. [7]. Fig. 3 shows thetemperature contours and streamline comparison for the case ofRa ¼ 104. The mesh number dependent test was also performed,which indicated that 200 200 mesh size for both the coarse andfine grids has an adequate accuracy for the present problem.Therefore the following numerical results are those having themesh numbers of 200 200 for both the coarse and fine grids. Inorder to make a comparison with the experimental data, we adjustthe non-dimensional relaxation times of sf and sg, so that thePrandtl number is about 3.53, which is approximately equal to thevalue of water at temperature of 50 C.Fig. 1. The geometry configuration of the numerical model.Fig.
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