The spatial distribution of collisionless ions collected by aspherical object of radius much larger than the Debye length, in aflowing plasma, is calculated using a particle-in-cell code. Theresults provide the first rigorous theoretical calibration of a `Mach probe' in a plasma with negligible magnetic field. They are alsoapplicable, for example, to spacecraft-plasma interactions. Ion toelectron temperature ratios 0.1<Ti/ZTe<10 are explored. Qualitativedifferences are observed between the results for low and highTi/ZTe, arising from ion dynamics in the wake. However, apractically universal form for the upstream to downstream currentdensity ratio dependence on flow velocity is observed for Ti/ZTe≲3.