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We present an experimental and numerical study of the flow downstream of honeycomb flow straighteners for a range of Reynolds numbers, covering both laminar and turbulent flow inside the honeycomb cells. We carried out experiments with planar particle image velocimetry (PIV) in a wind tunnel and performed numerical simulations to perform an in-depth investigation of the three-dimensional flow field. The individual channel profiles downstream of the honeycomb gradually develop into one uniform velocity profile. This development corresponds with an increase in the velocity fluctuations which reach a maximum and then start to decay. The position and magnitude of the turbulence intensity peak depend on the Reynolds number. By means of the turbulence kinetic energy (TKE) budget it is shown that the production of TKE is dominated by the shear layers corresponding to the honeycomb walls. The near-field and far-field decay of the turbulence intensity can be described by power laws where we used the position where the production term of the TKE reaches its maximum as the virtual origin.