In this work, we define a family of explicit a posteriori error estimators for Finite Volume methods in computational fluid dynamics. The proposed error estimators are inspired by the Variational Multiscale method, originally defined in a Finite Element context. The proposed error estimators are tested in simulations of the incompressible Navier-Stokes equations, the thermally-coupled Navier-Stokes equations, and the fully-coupled compressible large eddy simulation of the HIFiRE Direct Connect Rig Scramjet combustor.