River current energy is regarded as one of the most environmentally friendly sources of electricity. Because it doesn't produce power by holding water in a reservoir and causing a height differential, a river current (or hydrokinetic) device is not a dam. Turbines placed inside rivers immediately harvest the kinetic energy of flowing water. Like Egypt's river Nile can be used to study this type of energy. A submerged horizontal axis turbine like Archimedes spiral turbine AST can capture the kinetic energy from the river stream contained in the hydro-kinetic energy conversion process. This type of renewable energy meets electric power demand in distant riverside areas, widely acknowledged as a novel and rare alternative. The main objective of this work is to use CFD to simulate and design an Archimedes spiral turbine that can extract power from the water current stream energy. The numerical analysis indicates that the best available water current speed is 2.5 m/s, and the best Gap Ratio (GR) between the blade of hydrokinetic AST is 0.95 and has a maximum power coefficient of 30.08% at a TSR of 2. The effect of aerofoil blades of hydrokinetic AST deduced that the NACA4401 is the best aerofoil shape to achieve a higher-power coefficient Cp of 31.2%. However, the maximum CP of the conventional hydrokinetic AST is 24.9%, which means that the new design with a Gap Ratio (GR) equal to 0.95 and NACA4401 aerofoil blades enhanced the performance by a relative increase equals 25.3%.