COBEM99

S25 Métodos Numéricos

Title:

AN INVESTIGATION OF THE FLOW AROUND TWO CIRCULAR CYLINDERS IN TANDEM ARRANGEMENTS

Summary :

THE SHEDDING OF VORTICES AND FLOW INTERFERENCE BETWEEN TWO CIRCULAR CYLINDERS IN TANDEM ARRANGEMENTS ARE INVESTIGATED NUMERICALLY IN THIS PAPER FOR VARIOUS VALUES FOR THE GAP BETWEEN THE CYLINDERS. THE CALCULATIONS ARE CARRIED OUT ON A THREE-NODED UNSTRUCTURED FINITE ELEMENT MESH. ALL THE SIMULATIONS ARE PERFORMED THROUGH THE FINITE-ELEMENT METHOD. THE MESH IS FINER CLOSE TO THE CYLINDER WALL IN ORDER TO HAVE A BETTER DESCRIPTION OF THE BOUNDARY-LAYER. THE MAIN APPLICATION OF THE PRESENT INVESTIGATION IS TO DETERMINE THE EFFECTIVE DRAG COEFFICIENT OF A BUNDLE OF RISERS EXISTING IN OFFSHORE PLATFORMS USED FOR OIL EXPLORATION. THESE RISERS ARE SUBJECT TO CURRENTS AND OSCILLATORY FLOW DUE TO WAVES, FLOWS WITH A VERY HIGH DEGREE OF COMPLEXITY, WITH CHANGES OF INTENSITY AND DIRECTION AS THE DEPTH OF WATER INCREASES. THE BRAZILIAN OFFSHORE PLATFORMS ARE LOCATED IN THE ATLANTIC OCEAN WHERE DEPTHS OF WATER OF MORE THAN 1,000 M ARE VERY COMMON. PRODUCTION OF MORE THAN 100,000 BARRELS OF OIL PER DAY IN ONE SINGLE PLATFORM HAS ALREADY BEEN ESTABLISHED. IN SUCH CONDITIONS A BETTER UNDERSTANDING OF THE VORTEX DYNAMICS CAUSING VIBRATION OF RISERS IS ESSENTIAL.

Author :

Ferrari Jr. , José Alfredo
Meneghini, Julio Romano
Saltara, Fábio 0
Siqueira, Cesareo de La Rosa

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