Run error--N61 Emergency stop

XXXIMMY · August 2, 2022, 22:06

Hi Reef3d Team,

When I simulate the motion state of the floating body passing through the bridge pier, the CFD model encounter Emergency stop -- N61 velocity exceeding critical value.

How do I deal with this issue? The attachment is the control file, ctrl file, floating file and motion file for the model.

Thanks in advance.

Kind regards
Linxi

kamath · August 3, 2022, 09:04

Hi,
This may take some effort to solve, but here are some pointers:

Use "S" structures in control.txt in place of O.

Why is the tank 10 m high if you have a water depth of only 1.6 m? May be you can save some grids there?

The motion file is quite sparse, this can result in large gradients being calculated for the motion of the object, try including more points for time and position (compared to just two positions you currently have)

Grid size and CFL number could also play a role.

Hope that helps

XXXIMMY · August 3, 2022, 10:07

I am sincerely appreciate for your suggestions.

In the more points for time and position you mentioned, how to define the non-straight navigation path of the floating body?

Hope to get more detailed information.

Thanks in advance.

Kind regards
Linxi

kamath · August 4, 2022, 06:44

Prescribing complex pathways for forced motion is not possible currently

XXXIMMY · August 7, 2022, 20:44

Thank you for the reply.

In addition, there might be a problem in the simulation.

Since the flow field is often unstable during the simulation (probably because the inflow boundary is defined by the flow), how to use reef3d to open the flow velocity boundary?

I would be very grateful to hear from you.

Kind regards
Linxi

August 3, 2022, 09:04		#2
kamath Senior Member Arun Kamath Join Date: Nov 2014 Location: Trondheim, Norway Posts: 265 Rep Power: 13	Hi, This may take some effort to solve, but here are some pointers: Use "S" structures in control.txt in place of O. Why is the tank 10 m high if you have a water depth of only 1.6 m? May be you can save some grids there? The motion file is quite sparse, this can result in large gradients being calculated for the motion of the object, try including more points for time and position (compared to just two positions you currently have) Grid size and CFL number could also play a role. Hope that helps __________________ Arun X years with REEF3D

August 4, 2022, 06:44		#4
kamath Senior Member Arun Kamath Join Date: Nov 2014 Location: Trondheim, Norway Posts: 265 Rep Power: 13	Prescribing complex pathways for forced motion is not possible currently __________________ Arun X years with REEF3D

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August 3, 2022, 10:07		#3
XXXIMMY New Member zhangzhang Join Date: Aug 2022 Posts: 9 Rep Power: 3	I am sincerely appreciate for your suggestions. In the more points for time and position you mentioned, how to define the non-straight navigation path of the floating body? Hope to get more detailed information. Thanks in advance. Kind regards Linxi

August 7, 2022, 20:44		#5
XXXIMMY New Member zhangzhang Join Date: Aug 2022 Posts: 9 Rep Power: 3	Thank you for the reply. In addition, there might be a problem in the simulation. Since the flow field is often unstable during the simulation (probably because the inflow boundary is defined by the flow), how to use reef3d to open the flow velocity boundary? I would be very grateful to hear from you. Kind regards Linxi