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Local variation of the time-averaged (a) pressure coefficient, (b) skin friction coefficient, (c) Nusselt number, (d) fast Fourier transformation of the lift coefficient, and (e) the slip-velocity for the no-slip and superhydrophobic stationary cylinders.
Source publication
Numerical simulation of convective heat transfer over a stationary and transversely oscillating partial super-hydrophobic cylinder has been performed using OpenFOAM libraries. Superhydrophobicity of the cylinder surface has been addressed by means of a partial slip boundary condition. Applying the slip condition to the surface of the stationary cyl...
Contexts in source publication
Context 1
... This diagram could be used to associate the value of slip length to a desired slip coefficient. For the purpose of determining the accuracy of this diagram, Kn = 0.2 is selected, where the corresponding value of the slip coefficient is found to be β = 0.1. The local distribution of form drag and the skin friction coefficient are also shown in Fig. 8(a) and (b), respectively. As can be seen, the pressure difference between the front and rear stagnation points shows a 24 percent decrease for the superhydrophobic cylinder, which is responsible for the pressure drag reduction mentioned above. Furthermore, superhydrophobicity significantly reduces the skin friction coefficient over most ...
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... superhydrophobicity significantly reduces the skin friction coefficient over most of the cylinder surface, showing a 65 percent decrease of its maximum value. Figure 8(c) illustrates the local variation of the Nusselt number for both the no-slip and superhydrophobic cylinders. It is clear that heat transfer is enhanced near the front and rear stagnation points. ...
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... the front stagnation point which explains the larger value of N u at this position. This trend stems from higher rates of convection due to slip in this region, as shown by the velocity vectors in Fig. 9(b) and (c). Spectral analysis of the lift coefficient is also carried out by means of the fast Fourier transform and the result is reported in Fig. 8(d). The figure proves that superhydrophobicity increases the dimensionless vortex shedding frequency, i.e., the Strouhal number by almost 21 percent, from 0.193 to 0.233. This increasing trend is in accordance with the results reported in previous studies [61]. It is seen that the maximum value of the normalized power density reduces ...
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... shedding frequency, i.e., the Strouhal number by almost 21 percent, from 0.193 to 0.233. This increasing trend is in accordance with the results reported in previous studies [61]. It is seen that the maximum value of the normalized power density reduces remarkably for the superhydrophobic cylinder, which shows a 70 percent decrease. Finally, Fig. 8(e) depicts the variation of the mean dimensionless slip-velocity along the surface of the cylinder, which has been normalized using the free-stream velocity. It is shown that the amount of U * slip rises to its maximum value at θ around 65 • , and after falling down to zero at the separation point, remains extremely low in the wake ...
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