Objectives To investigate the near-wall rotating cylindrical wake and hydrodynamic characteristics, flow around cylinder at typical gap ratios is investigated.

Methods A numerical simulation of flow around a near-wall rotating cylinder with different gap ratios (G/D = 0.2, 0.8, 1.4) and rotation rates at Reynolds numberRe = 200 was carried out to compare the cylindrical wake and hydrodynamic characteristics at different gap ratios and rotation rates.

Results The results show that: For G/D = 0.2, the cylindrical vortex shedding is significantly suppressed and the lift and drag force on the cylindrical surface remain steady. For G/D = 0.8 and G/D = 1.4, at low rotation rates, the "wake vortex" is shed and is similar to the 2S pattern, with sinusoidal periodic fluctuations in the lift and drag coefficients and small amplitude; at higher positive rotation rates, the cylindrical wake pattern is the stable D pattern with no vortex shedding (changing from D⁺ to D⁻ pattern as the rotation rate increases), the "wake vortex layer" is separated from the "wall vortex layer", the "wall vortex" is shed multi-periodically, the lift and drag coefficients are fluctuating multi-periodically and the amplitude is increasing significantly; at higher reverse rotation rates, the cylindrical surface is wrapped by a positive boundary layer, with no vortex shedding and no fluctuations in lift and drag.

Conclusions The results can provide a reference for the development of high efficient flow control technology.