Its unreasonable velocity field is presented and the optimal retrofitting scheme to the exhaust passage is provided to get a relative reasonable velocity field.

The flow field in gas burner's outport is measured by the five-hole probe. Reasonable velocity information was obtained in the experiment and gained some experience in applying the five-hole probe.

Now, I would think that it is reasonable to ask the following question: What is the average velocity, for instance, between time zero and time four?