A turbine airfoil comprising: an outer wall delimiting an airfoil interior, the outer wall extending span-wise along a radial direction of a turbine engine and being formed of a pressure sidewall and a suction sidewall joined at a leading edge and a trailing edge, at least one partition wall positioned in the airfoil interior connecting the pressure and suction sidewalls along a radial extent so as define a plurality of radial cavities in the airfoil interior, an elongated flow blocking body positioned in at least one of the radial cavities so as to occupy an inactive volume therein, the flow blocking body extending in the radial direction and being spaced from the pressure sidewall, the suction sidewall and the partition wall, whereby a first near-wall cooling channel is defined between the flow blocking body and the pressure sidewall, a second near-wall cooling channel is defined between the flow blocking body and the suction sidewall, and a connecting channel is defined between the flow blocking body and the partition wall, the connecting channel being connected to the first and second near-wall cooling channels along a radial extent to define a radially extending internal cooling channel (B-E), a flow splitter feature located at an inlet of the internal cooling channel (B-E) and being shaped to create a flow separation region downstream of the flow splitter feature in the connecting channel, whereby coolant flow velocity is locally increased in the first and second near-wall cooling channels in relation to the connecting channel, to enhance heat transfer between the coolant and the outer wall. an outer wall delimiting an airfoil interior, the outer wall extending span-wise along a radial direction of a turbine engine and being formed of a pressure sidewall and a suction sidewall joined at a leading edge and a trailing edge, at least one partition wall positioned in the airfoil interior connecting the pressure and suction sidewalls along a radial extent so as define a plurality of radial cavities in the airfoil interior, an elongated flow blocking body positioned in at least one of the radial cavities so as to occupy an inactive volume therein, the flow blocking body extending in the radial direction and being spaced from the pressure sidewall, the suction sidewall and the partition wall, whereby a first near-wall cooling channel is defined between the flow blocking body and the pressure sidewall, a second near-wall cooling channel is defined between the flow blocking body and the suction sidewall, and a connecting channel is defined between the flow blocking body and the partition wall, the connecting channel being connected to the first and second near-wall cooling channels along a radial extent to define a radially extending internal cooling channel (B-E), a flow splitter feature located at an inlet of the internal cooling channel (B-E) and being shaped to create a flow separation region downstream of the flow splitter feature in the connecting channel, whereby coolant flow velocity is locally increased in the first and second near-wall cooling channels in relation to the connecting channel, to enhance heat transfer between the coolant and the outer wall.