How do I model a ball joint with high inertial moment stiffness?
The conservative approach would be to add a constant moment at one end of the flexible joint. Back to Index Question 69: Please confirm the recommended value of the added mass coefficient, Cm for a circular cylinder according to DNV Rules for Submarine Pipeline Systems – 1981 – Fig. A.7. Answer: Sorry for the confusion Cm and Ci are inter-changeable in Autopipe i.e mass (inertia) coefficient in Buoyancy, Wave Load Hydrodynamic Data dialogs. So Autopipe (Cm)is inertia coefficient but DNV 81 (Cm) is the added mass coefficient. Where Autopipe Mass coefficient (Cm) is the inertia coefficient(i.e. 1 + added mass coeff) [where added mass coeff = Range 2.29 to 1.0 (no fixed boundary) as per DNV’81 Figure A.7), hence Autopipe Cm(Ci) = 3.29 to 2.0] We will be updating the program and help in v7.0 to clarify the definition of these coefficients. The only Cm (inertia) used in the modal analysis is the Cm value in the buoyancy loading dialog.
