Time saving or consuming FLUENt

sachindra · September 12, 2015, 02:38

Hi friends. I have a question. Is FLUENT time consuming or time saving software. Because when we solve a steady flow problem then it takes few minutes to converge but when we go for unsteady problem it will take more than a weak. Then What can we categorize this time factor in FLUENT. I need the the answer from any FLUENT people

AHF · September 12, 2015, 04:50

Quote:

Originally Posted by sachindra

Hi friends. I have a question. Is FLUENT time consuming or time saving software. Because when we solve a steady flow problem then it takes few minutes to converge but when we go for unsteady problem it will take more than a weak. Then What can we categorize this time factor in FLUENT. I need the the answer from any FLUENT people

more than a week ?

i think it's depend on your problem and also time step setting

LuckyTran · September 16, 2015, 00:20

The time-saving vs time-consuming is more related to your modelling approach than the software.

Basically, a steady simulation is an unsteady simulation with only 1 time-step (but very large dt). It depends on whether there is any time-scale to your problem. If your problem is stationary, then the choice of dt doesn't matter explicitly and the computational cost of an unsteady versus steady simulation scales with the total number of iterations that you perform:

For unsteady: number of time steps x number of iterations per time-step
vs
For steady: number of iterations

But if your problem has transients and you are trying to arrive at a stationary point (i.e. reach steady state) then the number of time-steps needed is proportional to the time-scale of the transient process (e.g. the time-constant of the problem).

If you choose to model your problem in an expensive way, then it will become an expensive problem.

September 12, 2015, 02:38	Time saving or consuming FLUENt	#1
sachindra New Member sachindra Join Date: Apr 2013 Posts: 2 Rep Power: 0	Hi friends. I have a question. Is FLUENT time consuming or time saving software. Because when we solve a steady flow problem then it takes few minutes to converge but when we go for unsteady problem it will take more than a weak. Then What can we categorize this time factor in FLUENT. I need the the answer from any FLUENT people

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September 16, 2015, 00:20		#3
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,751 Rep Power: 66	The time-saving vs time-consuming is more related to your modelling approach than the software. Basically, a steady simulation is an unsteady simulation with only 1 time-step (but very large dt). It depends on whether there is any time-scale to your problem. If your problem is stationary, then the choice of dt doesn't matter explicitly and the computational cost of an unsteady versus steady simulation scales with the total number of iterations that you perform: For unsteady: number of time steps x number of iterations per time-step vs For steady: number of iterations But if your problem has transients and you are trying to arrive at a stationary point (i.e. reach steady state) then the number of time-steps needed is proportional to the time-scale of the transient process (e.g. the time-constant of the problem). If you choose to model your problem in an expensive way, then it will become an expensive problem.