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1.: Bearman and Obasaju [2] experimental results where the bold line is A/D = 0 and Re = 20, 000 (a) Vortex shedding frequency versus reduced velocity (b) Distribution of mean pressure around an oscillating square-section cylinder

1.: Bearman and Obasaju [2] experimental results where the bold line is A/D = 0 and Re = 20, 000 (a) Vortex shedding frequency versus reduced velocity (b) Distribution of mean pressure around an oscillating square-section cylinder

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Numerical investigations (2D URANS) of flow past a square cylinder Work Description: External flows past bluff bodies, such as square cylinders, have been studied experimentally very well because of their technical applications. Despite the numerous experimental investigations, numerical simulations of such flows have drawn the interest of many re...

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... main objective was to In their studies the vortexshedding frequency n was estimated from the power spectra of pressure fluctuations recorded at the center of a side face of the square section. Figure 2.1a represents the shedding frequency of the stationary model A/D = 0, where A is the oscillation amplitude and D is the section dimension which remains constant. ...
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... mean pressure distribution around the cylinder was also measured. Figure 2.1b shows the pressure coefficient distribution along the points A − B − C − D, this shows clearly the pressure recovery due to the detachment of the boundary layer. ...
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... square aluminum cylinder was of diameter D = 4 cm, and length L = 39 cm, resulting in a blockage of 7% and an aspect ratio of 9.75. Figure 2.2 shows the deviation of phase-averaged velocity (u) profiles from the time averaged (u) profiles for two selected phases, one during acceleration (phase 5) and one during deceleration (phase 15). ...
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... it is known, the vortex shedding frequencies are not sensitive to the aspect ratio, and the ratios calculated in the simulations were in good agreement with published results. In this study, the time averaged pressure coefficient (C p ) distribution shown in Figure 2.3a is in a good agreement with the published experimental data and the numerical results. On the side-surface (0.5 ≤ x p ≤ 1.5) and the back surface (1.5 ≤ x p ≤ 2) C P does not show a large variation. ...
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... the side-surface (0.5 ≤ x p ≤ 1.5) and the back surface (1.5 ≤ x p ≤ 2) C P does not show a large variation. The mean streamwise velocity distribution along the centre-line (x 2 = 0) of the square is shown in Figure 2.3b. In the upstream region the results show a moreover good agreement with the experimental results from Durao et al. [13]. ...
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... inlet boundary is located at a distance 12H from the center of the cylinder and the outlet is located 30H downstream. Figure 2.4a shows that the mean pressure distribution is predicted fairly well by all models. ...
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... the modified model predicts fairly well the mean drag coefficient, the results for the mean pressure behind the rear corner C appears to show a faster rate of reduction than is suggested by the data. Figure 2.4b is a plot of the time averaged streamwise velocity along the center-line. The size of the recirculation zone downstream of the cylinder is captured quiet well by the modified model when the grid D2 is used to obtain a similar blockage ratio as in Lyn's experiments. ...
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... the diatomic gas assumption, γ = 1.4 and in the Figure 2.5 ρ/ρ ∞ is plotted as a function of M from zero to sonic flow. For M < 0.32 the value of ρ deviates from ρ 0 less than a 5%, and for all practical purposes the flow can be treated as incompressible. ...
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... methodologies depend on the problem to be considered and on the numerical methods used. Pope [7] provides a list of example cases where LES can be applied. As it is already known, turbulent flows contain a wide range of length and time scales. The range of eddy sizes that might be found in a flow is shown schematically on the left hand side of Fig. 2.6. The right-hand side of this figure shows the time Theoretical Background history of a typical velocity component at a point in the flow. What this image enlighten is the fact that LES provides a cost efficient solution for representing the large scale motions. If a more accurate representation of the small scales is required then ...
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... is important to state the difference between the Reynolds decomposition and the previous formulation. Here, the filtered velocity U (x, t) is a random field and in general the filtered residual is not zero, u = 0. Figure 2.7 shows a sample velocity field U (x) and the corresponding filtered field U (x) for a Gaussian filter with ∆ ≈ 0.35. Here it is evident that U (x) follows the general trends of U (x). ...
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... the average is over all time, then the resulting equations are the traditional steady RANS equations, the mean flow defined by the average is steady. Figure 2.8 shows a visual representation of how each of the described methods represent the turbulent flow over a bluff body. ...
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... the other hand, the computational cost for SST was almost three times lower than for the LES simulations. Figure 2.9 shows the main differences when representing the flow using the SST, SAS and LES methodologies. ...

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