Numerical Simulation Of Viscous Flow Past Two Tandem Circular Cylinders Of Different Diameters

In recent years, with oil and gas in land exploit exhausted, oil and gasexploitation move to deep-sea, it require marine structures unit such as offshoreplatforms、risers more security. In offshore oil and gas projects, it often usesmultiple-pipelines of different diameters in pipeline pave due to technicalconsiderations and economical requirements. Now, study in flow behaviors and VIVof multiple-pipelines with different diameters is not much, the paper use numericalmeasure to study flow past two tandem cylinders of different diameters.The paper summarizes current study about flow past multiple-pipelines, andanalyzes questions in flow past two cylinders of different diameters. Viscous flow pastcircular cylinders with different diameter ratio and spacing ratio is numericallysimulated by Fluent in the paper. Gap ratio G/D analyzed in simulation is0.2、0.4、0.8、1、1.5、2、3、6, and diameter ratio d/D is0.2、0.4、0.6、0.8, Re is200. The resultsinclude velocity distribution、streamlines、vorticity of wake flow and lift、dragcoefficients、vortex shedding frequency and so on.Effects of G/D and d/D on vortex shedding characteristics、lift and dragcoefficients of large and small cylinders、vortex shedding frequency are investigatedbased on the obtained simulation results. The analyses show that vortex sheddingcharacteristics display different forms with different gap ratio, when gap smaller thanthe critical gap, it displays single-wake shedding mode; when gap larger than thecritical gap, it displays two-wake shedding mode; the critical gap increases with d/Dincreases; lift and drag coefficients of large and small cylinders as well as frequency fchange sharply near the critical gap; large and small cylinders have same vortexshedding frequency f, but f decreases as d/D increases; it displays different wakeshedding mode with different Re in same G/D and d/D.