Dear @RyanDavies19 ,
I am interested in testing the Vortex-Induced Vibration (VIV) features of Moordyn. Two simple test cases have been established: one without VIV and another with VIV. The water depth is set at 300 meters, and a freely floating object is tethered by a line to a fixed point at the bottom. The configuration for the VIV case is as follows, with the Cl value adjusted to 0 for the case without VIV. The background current is 0.2 m/s in the positive x-direction.
--------------------- MoorDyn Input File ------------------------------------
MoorDyn input file of the mooring system
----------------------- LINE TYPES ------------------------------------------
TypeName Diam Mass/m EA BA/-zeta EI Cd Ca CdAx CaAx Cl dF cF
(name) (m) (kg/m) (N) (N-s/-) (N-m^2) (-) (-) (-) (-) (-) (-) (-)
rope 0.008 0.08 7.6e6 -1 30 2.0 1.1 0.15 0 0.8 0.08 0.18
---------------------- POINT PROPERTIES --------------------------------
ID Type X Y Z Mass Volume CdA Ca
(#) (-) (m) (m) (m) (kg) (mˆ3) (m^2) (-)
1 Fixed 0 0 -300 0 0 0 0
2 Free 0 0 -199.97 500 0.7 0.4 0.5
---------------------- LINES ----------------------------------------
ID LineType AttachA AttachB UnstrLen NumSegs LineOutputs
(#) (name) (#) (#) (m) (-) (-)
1 rope 1 2 100 100 -
---------------------- OPTIONS -----------------------------------------
2 writeLog Write a log file
0.00008 dtM time step to use in mooring integration (s)
1025.0 WtrDnsty water density (kg/m^3)
300 WtrDpth water depth (m)
1.0 dtIC time interval for analyzing convergence during IC gen (s)
0 TmaxIC max time for ic gen (s)
4.0 CdScaleIC factor by which to scale drag coefficients during dynamic relaxation (-)
0.001 threshIC threshold for IC convergence (-)
1 ICgenDynamic - 0 for stationary solver, 1 for upscaled drag legacy solver
1 Currents
0 disableOutTime
0 dtOut Time step size to be written to output files. zero:coupling timestep
------------------------- need this line --------------------------------------
The velocity file is as follows
--------------------- MoorDyn steady currents File ----------------------------------
Tabulated file with the water currents components
z (m), ux (m/s), uy (m/s), uz (m/s)
-300.0 0.2 0 0
0 0.2 0 0
The positions of the float are recorded every second. Since the implemented VIV model simulates only cross-flow VIV, I expect the X and Z coordinates of the free float to remain consistent between the cases with and without VIV, while some oscillations in the Y coordinate should be observable for the VIV case.
However, the results indicate that the free floats in these two cases reach different final X and Z positions. Could you provide an explanation for this phenomenon?
Dear @RyanDavies19 ,
I am interested in testing the Vortex-Induced Vibration (VIV) features of Moordyn. Two simple test cases have been established: one without VIV and another with VIV. The water depth is set at 300 meters, and a freely floating object is tethered by a line to a fixed point at the bottom. The configuration for the VIV case is as follows, with the Cl value adjusted to 0 for the case without VIV. The background current is 0.2 m/s in the positive x-direction.
The velocity file is as follows
The positions of the float are recorded every second. Since the implemented VIV model simulates only cross-flow VIV, I expect the X and Z coordinates of the free float to remain consistent between the cases with and without VIV, while some oscillations in the Y coordinate should be observable for the VIV case.
However, the results indicate that the free floats in these two cases reach different final X and Z positions. Could you provide an explanation for this phenomenon?