AERODYNAMIC CHARACTERISTICS OF LEGS ON JACK-UP TYPE OFFSHORE OIL RIG.

THIS PAPER STUDIES THE EFFECT OF WIND ACTION UPON A LEG THAT HAS A TRIANGLE LATTICE-TYPE TRUSS COMPOSED OF CHORDS, HORIZONTAL AND DIAGONAL BRACES. A WIND TUNNEL TEST WAS CARRIED OUT BY USING A TWO-DIMENSIONAL MODEL. THE RESULTS OBTAINED ARE AS FOLLOWS: (1) THE DRAG FORCE ACTING ON THE LEG IS ALMOSTINDEPENDENT OF WIND DIRECTION AND THE VALUE OF THE DRAG COEFFICIENT IS EQUAL TO 1. 10 IN WIND DIRECTION DEFINED AS ″BETA″ = 0 D. ; (2) THE MEASURED STROUHAL VALUE FOR THE MAIN CHORD WITH RACKS IS 0. 184; (3) THE GENERATION OF A KARMAN VORTEX IS CONSIDERABLY AFFECTED BY EXISTENCE OF RACKS OF MAIN CHORDS. THE LIFT COEFFICIENT DUE TO WIND-INDUCED VIBRATION DEPENDS ON THE AMPLITUDE; (4) THE MAIN CHORD IS CONSIDERED TO BE A MAJOR DETERMINANT OF THE AERODYNAMIC CHARACTERISTICS OF A LEG STRUCTURE. THE POSITION OF THE LEG WITH RESPECT TO WIND DIRECTION REMARKABLY AFFECTS ITS REACTION CHARACTERISTICS;(5) IT IS RECOGNIZED THAT THE AERODYNAMIC CHARACTERISTICS OF A GIVEN LEG HAVE NO INFLUENCE UPON THOSE OF OTHER LEGS.