13 An LES study and ... in-line tube-banks Table 1: Comparison of results for r.m.s pressure distribution C ′ p uniform values of fluctuating pressure distributions around the first cylinder from the findings of Shim [27]. One must suspect this according to the work of Norberg[40] at a comparable Reynolds number that C ′ P exhibits a very low level at the frontal stagnation line ( θ = 0 $^{o}$). Second, it can be observed that the general trend is in reasonably good agreement with the measurements of [27] except for the first column cylinder. Moreover, the position of first peak as shown in the figure 9b corresponds to the same angle in the figure 6a that indicates the tripping of laminar boundary layer separation. The second peak after the shoulder of the cylinder results from the reattachment of boundary layer separation on the surface. Table 1 shows a comparison of r.m.s value and maximum value of pressure fluctuations from the present LES computation with the experimental values of Shim[27] and NorbergNorberg. It can be observed that the values from the present calculations match very well with the measurements, especially for the angular position within the windward side at which the maximum r.m.s value of fluctuating pressure occurs. In addition, one interesting point is that the width of wakes from the second, third and fourth column cylinder is very close. The maximums on downstream cylinders are caused by the impingement of shedding-vortex from the upstream cylinders. The low r.m.s values of pressure fluctuation compared with experimentally measured ones on the leeward side result from the relatively weak wake predicted by the present LES with wall-layer modelling. It is also worthwhile emphasizing that the calculated results at θ = 90 o are significantly higher that the value at a comparable Re = 10 k compiled in Norberg [40] for a single circular cylinder. Case Maximum of C ′ p C ′ $_{p}$(90$^{o}$) Present LES ( Re$_{g}$ = 15270) C1 0.236(110 $^{o}$) 0.159 C2 0.584(40 . 4 $^{o}$) 0.425 C3 0.640(40 . 4 $^{o}$) 0.441 C4 0.544(36 . 7 $^{o}$) 0.377 Experiments [27] C1 0.457(110 $^{o}$) 0.438 C2 0.641(40 $^{o}$) 0.539 C3 0.658(40 $^{o}$) 0.592 C4 0.658(40 $^{o}$) 0.582 Experiments [40] Single cylinder Re = 10 k 0.292 0.282