Spikes occurs in data plots

zhuzhangkr · January 20, 2016, 02:51

Hi, everyone!

Recently i'm solving a wedge dropping problem. i applied overset mesh technique and DFBI module to simulate the drop motion of wedge body in a computational domain...

However, when checking my result plots, i found some spikes in my pressure results... it means, there are some results are extremely high or low.. For example, the pressure at first time step could be as high as 2kPa... horrible!
BTW, i give the wedge body an initial velocity of 3 m/s... so i guess something wrong at discrete momentum eq. or divergence or somewhere..

some numerical conditions: segregated implicit flow... VOF method... laminar... no-slip B.C..

This's reaaaally a headache problem i can't explain...

Is there anyone who know this?? Really appreciate it!!

fluid23 · January 20, 2016, 11:01

are your time steps converging?

fluid23 · January 20, 2016, 11:02

and is the time step size appropriate?

zhuzhangkr · January 20, 2016, 21:36

Quote:

Originally Posted by MBdonCFD

and is the time step size appropriate?

Thanks for response!

My time step is 1e-5 s... in order to keep Convective Courant Number under 1.0 during whole simulation... Unsteady condition is selected therefore time step is fixed during computation..

January 20, 2016, 02:51	Spikes occurs in data plots	#1
zhuzhangkr New Member zhu zhang Join Date: Jul 2015 Posts: 5 Rep Power: 11	Hi, everyone! Recently i'm solving a wedge dropping problem. i applied overset mesh technique and DFBI module to simulate the drop motion of wedge body in a computational domain... However, when checking my result plots, i found some spikes in my pressure results... it means, there are some results are extremely high or low.. For example, the pressure at first time step could be as high as 2kPa... horrible! BTW, i give the wedge body an initial velocity of 3 m/s... so i guess something wrong at discrete momentum eq. or divergence or somewhere.. some numerical conditions: segregated implicit flow... VOF method... laminar... no-slip B.C.. This's reaaaally a headache problem i can't explain... Is there anyone who know this?? Really appreciate it!!

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January 20, 2016, 11:01		#2
fluid23 Senior Member Matt Join Date: Aug 2014 Posts: 947 Rep Power: 18	are your time steps converging?

January 20, 2016, 11:02		#3
fluid23 Senior Member Matt Join Date: Aug 2014 Posts: 947 Rep Power: 18	and is the time step size appropriate?