A note on waveless subcritical flow past a submerged semi-ellipse

The flow of water over a broad obstruction usually creates a downstream wave train. However, it has been shown that for some objects and discrete values of flow rate and height and length of the obstruction, there are no downstream waves – and hence zero wave drag on the object. Here we revisit this problem and complete an examination of the parameter space for flow over a semi-ellipse. A rich pattern of waveless solutions that merge into each other is detected.