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Explicit converging faster compared to implicit

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Old   January 20, 2012, 05:43
Default Explicit converging faster compared to implicit
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Hello, can anyone tell me are there any cases where the explicit scheme converges faster compared to implicit, if so why does that happen?
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Old   January 20, 2012, 18:16
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If the physical timestep is very small, i.e. close to the explicit time step, explicit schemes will be faster.
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Old   January 21, 2012, 05:14
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Thanh for d reply cfdnewbie. Can u just eloborate it a bit more...also some of d example cases if u can...
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Old   January 21, 2012, 11:58
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it totally depends on your physics, your implementation and your hardware. It is not clear-cut, so there's no classical example. The smaller the timescales governing the flow, the larger your available number of cpus, the likelier the explicit scheme is to outperform the implicit one.
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Old   January 22, 2012, 17:57
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Quote:
Originally Posted by harish_0689@ View Post
Hello, can anyone tell me are there any cases where the explicit scheme converges faster compared to implicit, if so why does that happen?
Depends on what you mean with converge. Do you mean "convergence to steady state" or do you mean "convergence in the linear solver" or something else?

Explicit schemes are faster at each time-step since they do not need to solve a system of equations.

However, implicit schemes can take much larger time-steps. If you have implicit treatment of the non-linear terms then you also need some way to deal with this.

So basically:

Quote:
Originally Posted by cfdnewbie
If the physical timestep is very small, i.e. close to the explicit time step, explicit schemes will be faster.
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Old   January 23, 2012, 08:00
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i mean its convergence to the steady state.
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