In an ideal frictionless gas (zero viscosity), the flow after the object has passed through will be identical to the flow before the object, so in that sense th

In an ideal frictionless gas (zero viscosity), the flow after the object has passed through will be identical to the flow before the object, so in that sense the air moves "seamlessly" around the object. But during this process, the pressure of the gas still changes. You can think of this as just newton's second law: in order to change the velocity of an air packet, you must apply a force to it, and pressure is just force per area. So any time a gas flows in anything other than a straight line, you know that there was a pressure gradient involved and the pressure was not constant. It's a common example in fluid mechanics textbooks to derive the flow of a zero-viscosity gas around a cylinder, you can get an exact solution e.g. here: http://brennen.caltech.edu/fluidbook/basicfluiddynamics/potentialflow/singularities/cylinder.pdf http://brennen.caltech.edu/fluidbook/basicfluiddynamics/pote... . Note that in this example there is no drag, but there are two zones of high pressure in front of and behind the cylinder. Those zones would have higher-than-ambient temperature.