Dear Pravin,
Now it appears that the problem is not with the size of the turbulent wind field, but that there is a numerical instability in your model. Warnings regarding a “small angle approximation violation”, a simulation crash, or very large deflections that occur in the time series near the start of a simulation are good signs of a numerical instability. Please use “Search…” in the upper right of the forum to search for “small angle assumption” to see how others have solved similar problems in the past e.g. see my post dated Nov 04, 2010 in the following forum topic: Error in FAST, working in ADAMS - #3 by Jason.Jonkman.
Best regards,