Pressure Drop in Expansion Flow – Thin Thin Swe


The following figures compare the velocity field in expansion flow and contraction flow. The flow is for micro-fluidic devices; hence, the flow is laminar and in low Reynolds number region.  

The difference between expansion flow and contraction flow is that some of the flow in expansion flow is re-circulated as the flow from the small channel empties into the large channel. The re-circulation of the flow was not the case for contraction flows.

  Figure1. Typical Expansion Flow                         Figure2. Typical Contraction Flow

                Re =10, 3:1 axisymmetric                         Re = 10, 3:1 axisymmetric

Mesh Refinement

Re = 10:

Expansion Flow                                                         Contraction Flow

Elements                       KL                                                               Elements                                 KL 

    1760                        0.4330                                            1760                     19.2209

    7040                        0.5402                                            7040                     19.3029

  28160                        0.5867                                          28160                     19.3440

As compared above, the accuracy is sufficient, and the excess pressure drop in expansion flow is much less than that in contraction flow.

 

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