Step-by-step approach in running unsteady flow in LES using Fluent

Taiwo_Oni · December 2, 2013, 06:03

Dear all,
Based on what I have gathered from various sources, please I want to know if the following is the correct step-by-step approach in running unsteady flow in LES using Fluent:
1. Start by running a steady state flow simulation using a Reynolds-averaged turbulence model such as standard

-

, etc. Run until the flow field is reasonably converged and then use the solve/initialize/ init-instantaneous-vel text command to generate the instantaneous velocity field out of the steady-state RANS results.
2. Run LES until the flow becomes statistically steady.
4. Continue until you get statistically stable data.

5. Zero out the initial statistics using the solve/initialize/init-flow-statistics text command. Before you restart the solution, enable Data Sampling for Time Statistics.Thank you.

Taiwo_Oni · December 2, 2013, 06:10

Dear all,
Based on what I have gathered from various sources, please I want to know if the following is the correct step-by-step approach in running unsteady flow in LES using Fluent:
1. Start by running a steady state flow simulation using a Reynolds-averaged turbulence model such as standard

-

, etc. Run until the flow field is reasonably converged and then use the solve/initialize/ init-instantaneous-vel text command to generate the instantaneous velocity field out of the steady-state RANS results.
2. Run LES until the flow becomes statistically steady.
4. Continue until you get statistically stable data.

5. Zero out the initial statistics using the solve/initialize/init-flow-statistics text command. Before you restart the solution, enable Data Sampling for Time Statistics.
Thank you.

sbaffini · December 2, 2013, 14:12

Basically yes. Point 4 is not usually performed.

raunakjung · October 24, 2016, 22:27

Did you succesfully perform LES ?
When using /solve/initialize/init-instantaneous-vel while carrying out LES i am getting the error
Error : (segmentation fault)
Error Object : #f
What could be the problem ? How to solve it ? "

sbaffini · October 25, 2016, 03:48

A segmentation fault usually means that some memory location has been accessed (i.e., a variable) but that wasn't present. In practice, it is probable that you forgot to make some of the steps necessary to follow the procedure. Maybe:

1) Perform the preliminary RANS calculation (i don't remember if a specific RANS model is needed)

2) Activate LES after the RANS

or maybe you did something that erased the previous RANS solution.

December 2, 2013, 06:03	Step-by-step approach in running unsteady flow in LES using Fluent	#1
Taiwo_Oni New Member Taiwo Join Date: Oct 2011 Location: UK Posts: 21 Rep Power: 14	Dear all, Based on what I have gathered from various sources, please I want to know if the following is the correct step-by-step approach in running unsteady flow in LES using Fluent: 1. Start by running a steady state flow simulation using a Reynolds-averaged turbulence model such as standard - , etc. Run until the flow field is reasonably converged and then use the solve/initialize/ init-instantaneous-vel text command to generate the instantaneous velocity field out of the steady-state RANS results. 2. Run LES until the flow becomes statistically steady. 4. Continue until you get statistically stable data. 5. Zero out the initial statistics using the solve/initialize/init-flow-statistics text command. Before you restart the solution, enable Data Sampling for Time Statistics.Thank you.

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December 2, 2013, 06:10		#2
Taiwo_Oni New Member Taiwo Join Date: Oct 2011 Location: UK Posts: 21 Rep Power: 14	Dear all, Based on what I have gathered from various sources, please I want to know if the following is the correct step-by-step approach in running unsteady flow in LES using Fluent: 1. Start by running a steady state flow simulation using a Reynolds-averaged turbulence model such as standard - , etc. Run until the flow field is reasonably converged and then use the solve/initialize/ init-instantaneous-vel text command to generate the instantaneous velocity field out of the steady-state RANS results. 2. Run LES until the flow becomes statistically steady. 4. Continue until you get statistically stable data. 5. Zero out the initial statistics using the solve/initialize/init-flow-statistics text command. Before you restart the solution, enable Data Sampling for Time Statistics. Thank you.

December 2, 2013, 14:12		#3
sbaffini Senior Member Paolo Lampitella Join Date: Mar 2009 Location: Italy Posts: 2,152 Blog Entries: 29 Rep Power: 39	Basically yes. Point 4 is not usually performed.

October 24, 2016, 22:27		#4
raunakjung Senior Member raunak jung pandey Join Date: Jun 2016 Posts: 102 Rep Power: 9	Did you succesfully perform LES ? When using /solve/initialize/init-instantaneous-vel while carrying out LES i am getting the error Error : (segmentation fault) Error Object : #f What could be the problem ? How to solve it ? "

October 25, 2016, 03:48		#5
sbaffini Senior Member Paolo Lampitella Join Date: Mar 2009 Location: Italy Posts: 2,152 Blog Entries: 29 Rep Power: 39	A segmentation fault usually means that some memory location has been accessed (i.e., a variable) but that wasn't present. In practice, it is probable that you forgot to make some of the steps necessary to follow the procedure. Maybe: 1) Perform the preliminary RANS calculation (i don't remember if a specific RANS model is needed) 2) Activate LES after the RANS or maybe you did something that erased the previous RANS solution.