When a steadily flowing gas flows from a larger-diameter pipe to a smaller-diameter pipe, what happens to (a) its speed, (b) its pressure, and (c) the spacing between its streamlines?

Solution 47E The continuity equation can be used here, which states that Av = constant where A = cross section and v = speed. The gas flows to a smaller diameter pipe. Hence from the above equation, cross-section decrease is accompanied by an increase in speed. When there is an increase in speed, there will be a decrease in pressure. The pipe gets narrower, hence the streamlines get loser.