TABLE OF CONTENTS There are two options when coupling separate aerodynamic and structural dynamic codes. The simplest method to couple separate aerodynamic and structural dynamic codes is weak coupling, wherein there is no intermediate exchange of information between the two solvers at each time level. At each time level the fluid is solved using the current structural position to give aerodynamic loads on the structure, and these are then used to solve for a new structural position. This is simply repeated for each time level. Hence, the fluid and structure are not synchronised in time, and there is always a phase lag between the two. This phase lag will be time-step dependent, and this has been examined earlier.
Alternatively strong coupling can be used, wherein there is exchange of information between the two solvers. At each real time level the aerodynamic loads are computed, then the structural position that results from those loads are computed. The aerodynamic loads around this new structural position are then recomputed, and this iterative procedure is repeated until the fluid and structure are perfectly synchronised at each real time level. This is more complex to code than weak coupling, but ensures there is no phase lag between fluid and structure. A flight control system is integrated with the aero-structural code in the next section, and it is clearly desirable that no phase lag is present in this case.
In fact, earlier it has been shown (Djayapertapa and Allen, 2001) that only for low numbers of...
