This paper deals with the numerical investigation of the in-cylinder flow structures under steady-state conditions utilizing the finite-volume CFD package, STAR CCM+. Two turbulence models were used to simulate the turbulent flow structure namely, Realizable k-ε and Reynolds Stress Turbulence Model, RSTM. Three mesh densities of polyhedral type are examined. The three-dimensional numerical investigation has been conducted on an engine head of a pent-roof type (Lotus) for a number of fixed valve lifts (2mm, 5mm, 8mm) at two pressure drops 2451.662 Pa and 6227.222 Pa that is equivalent to engine speeds of 2500 and 4000 RPM respectively. This correlation between pressure drop and engine speed is provided by Lotus engineering according to real engine studies. Based on the comparison between two turbulence models, the turbulent flow structure was simulated using RSTM model for a number of tumble and swirl planes. The nature of the flow structure together with discussions on the influence of the pressure drop and valve lift parameters on the flow structures were presented and discussed. Computed results for the mean and fluctuations velocities were validated against previously published experimental data of Picton  from Laser Doppler Anemometry (LDA) measurements on the same head cylinder. The CFD velocity fields, obtained under steady-state conditions, were used to calculate swirl and tumble ratios. Calculated swirl and tumble ratios that were obtained by both turbulence models and Particle Image Velocimetry (PIV) measured data were compared.