This email from chengjiao.ren@uwa.edu.au originates from outside Imperial. Do not click on links and attachments unless you recognise the sender. If you trust the sender, add them to your safe senders list to disable email stamping for this address.

 

Dear Nekar++ users,

Hope the email finds you well.
 
I would like to know if anyone has tried restarting a VIV problem in VCS Mapping solver? In my case (VIV of a circular cylinder), when restarting a simulation from a flow field (restart2 in the attached figure 1, "*.map" for mapping and "*.fld" for initial conditions),  the force in the motion direction has large fluctuations at the initial few steps. These large fluctuations cause subsequent inconsistent evolutions for all signals compared with the original ones.  This issue is found for a forced vibration case when the domain has an initial acceleration, as per figure 2 below.
 
Noted that if we compare the Fy evolution (restart 2 in figure 1) with that of the restart 1 (only define the “u,v,w,p” in “*.fld” file for initial conditions), they are quite similar. I therefore suppose if the p field due to coordinate transform is not considered in “*.map”, resulting in significant changes on forces when the domain has non-zero acceleration.
 
Does anyone have any suggestions on restarting a VIV case? Since the initial difference doesn’t decay during the simulation, it cannot be ignored currently.
 
 
Thanks in advance.
Chengjiao
 
 
 
                 Figure 1, a free vibration case where the cylinder has 1-dof in y-direction                                     Figure 2, a forced vibration case where the cylinder is forced to vibrate in x-direction.
 

Dr Chengjiao Ren
 
Research Associate
School of Engineering • Perth WA 6009 Australia 
+61 413077330 • chengjiao.ren@uwa.edu.au