 flow compress fluid obstacl flow compress fluid obstacl well classic hydrodynam steadi stream frictionless incompress fluid exercis result forc obstacl rigid sphere immers develop resist attribut viscos sharp edg neg pressur accompani helmholtz case resist involv natur wake extend obstacl infinit distanc system disturb veloc mathemat extend infin remain attach obstacl resist absenc resist assert incompress fluid suppos small degre compress water affect conclus hand high rel veloc exceed sound fluid entir alter condit worth examin question close effect compress amen mathemat treatment 