VIV Numerical Benchmark

In the previous benchmark study organized by the 26^th ITTC Ocean Engineering Committee, all participants selected two-dimensional unsteady RANS methodology. The turbulence models were used with the assumption that the flow is fully developed to the turbulent status.

It was concluded from the study that the drag crisis phenomenon on the stationary smooth cylinder was not predicted in the numerical studies. It is well known that the drag crisis is caused by the instability of separated shear layer in critical range (3x10⁵< Re_D <3.5x10⁵). At the critical Reynolds numbers, the transition point is located very close to the point of flow separation. As a result, the shear layer eddies cause the mixing of flow in boundary layer so that the flow is energized and the flow separation is delayed. The delay of separation point leads to the reduction of the drag coefficient. The methodology based on two-dimensional, unsteady RANS with turbulence models is not sufficient to simulate the physical phenomenon (ITTC Ocean Engineering Committee Report, 2011). It is necessary to predict the complicate flow phenomenon using other CFD methods.

The objective of this study is to predict the drag crisis phenomenon with suitable CFD methods and compare with the experimental data by MARIN.

Specifications of the Cases

The benchmark cases for a smooth stationary cylinder in a cross flow are given below:

• Re = 6.31E+04, 1.26E+05, 2.52E+05, 3.15E+05, 5.06E+05, and 7.57E+05

• Calculation of minimum of 40 vortex shedding cycles of which 20 are used for analysis

• Providing time series of C_D and C_L in the data sheet in excel format as shown in the Results Sheet (see File)

• Derivation of Strouhal number, mean/RMS drag and lift coefficients C_D and C_L and presentation in the Results Sheet
  

• Presentation of flow contours and vorticity plots as shown in the Results Sheet
  

Checklist for Submission

• Contact information of the participant

• Answering all the questions in the Answer Sheet

• Including the C_L and C_D time series (at least 20 cycles) in the Data Sheet

• Including C_L and C_D and Strouhal number in the Results Sheet

• Presentation of flow contours and vorticity plots as illustrated in the Results Sheet

References

Wilde et al., 2003, “Experimental investigation of the sensitivity to in-line motions and magnus-like loft productions on Vortex-Induced Vibrations,” Proc. 13^th ISOPE, Hawai, Vol. III, pp. 593-598.

Wilde et al., 2001, “Experiments for high Reynolds numbers VIV on riser,” Proc. 11^th ISOPE, Stavanger, Vol. III, pp. 400-405.

Wilde et al., 2004, “Cross section VIV model test for novel riser geometries,” Proc. Deep Offshore Technology Conference (DOT), New Orleans, paper 12-3-Jaap de Wilde.

Wilde, J.J. and Huijsmans, R.H.M., 2004, “Laboratory investigation of long riser VIV response,” Proc. 14^th ISOPE, Toulon, Vol. III, pp. 511-516.

Wilde et al., 2006, “Experimental investigation into the vortex formation in the wake of an oscillating cylinder using particle image velocimetry,” Proc. 16^th ISOPE, San Francisco, Paper 2006-JSC-434, pp. 798-805.