# Unsteady AND Steady mode for Fully Developped Flow

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 April 14, 2004, 00:05 Unsteady AND Steady mode for Fully Developped Flow #1 Dominique Guest   Posts: n/a Hello! Here's the situation : I am simulating the effect of conjugate heat transfer for a carbon rod which has a heated tip (by a laser) and which is parallely located in a gaz flow (hence forced convection). As a start, I am considering the problem of a flow over a flat plate (but in a 2D axisymmetric system) WITHOUT any energy involved (I am just solving the equations for the flow). I am interested in the STEADY-STATE of the whole phenomena but I decided to simulate the flow first in unsteady mode until I would obtain a (somewhat) nearly fully-developped flow (it's still oscillating a little but I guess it can't get better in unsteady-mode). Now I wanted to "finalize" the fully-developped flow in STEADY-STATE to obtain a "real" mathematically fully-developped flow (So that not oscillation at all would occur). The problem that I get is that as soon as I start my simulation in steady-state (after nearly 10,000 converging iterations in unsteady-state) my residuals starts to diverge (even after 700-800 more iterations). I don't really like the idea of trial-and-error with the different relaxation schemes, I would prefer to understand why my residuals starts to diverge as soon as I enter the steasy-state mode. Regards, Dominique P.S.: Any one of you tried some microfabrication simulations with FLUENT (made essentially for the aeronautical field)?

 April 14, 2004, 16:48 Re: Unsteady AND Steady mode for Fully Developped #3 ap Guest   Posts: n/a If your flow is unsteady you can't simulate it using the steady solver. To do steady calculations, you need to be sure of the existence of the steady state. Hi ap