A blade for a rotor of a wind turbine having a substantially horizontal rotor shaft, said rotor comprising a hub, from which the blade extends substantially in a radial direction when mounted to the hub, the blade having a longitudinal direction (r) with a tip end and a root end and a transverse direction, the blade further comprising: - a profiled contour (40, 42, 50) including a pressure side and a suction side, as well as a leading edge and a trailing edge with a chord having a chord length extending there between, the profiled contour, when being impacted by an incident airflow, generating a lift, wherein - the blade is provided with a flow guiding device added to and protruding from the profiled contour (40, 42, 50) of the blade on the pressure side of the blade, wherein - the flow guiding device has a front surface facing toward an oncoming airflow and having an proximal point located at the profiled contour (40, 42, 50) and a distal point located at a distance from the profiled contour (40, 42, 50) of the blade, wherein - the profiled contour (40, 42, 50) has a surface normal at the proximal point, and wherein - the front surface comprises at least a first portion, which is angled towards the oncoming airflow and the leading edge of the blade so that an average tangent or median line to said first portion forms a first angle (Θ) with the surface normal being larger than 0 degrees, wherein the average tangent further is angled forward compared to a second normal to the chord, so that the median line and the second normal forms a second angle (α) being at least 5 degrees, and wherein - the flow guiding device is adapted to generate a separation of airflow downstream of the flow guiding device between the flow guiding device and the trailing edge of the blade, and wherein - the front surface is concave. - a profiled contour (40, 42, 50) including a pressure side and a suction side, as well as a leading edge and a trailing edge with a chord having a chord length extending there between, the profiled contour, when being impacted by an incident airflow, generating a lift, wherein - the blade is provided with a flow guiding device added to and protruding from the profiled contour (40, 42, 50) of the blade on the pressure side of the blade, wherein - the flow guiding device has a front surface facing toward an oncoming airflow and having an proximal point located at the profiled contour (40, 42, 50) and a distal point located at a distance from the profiled contour (40, 42, 50) of the blade, wherein - the profiled contour (40, 42, 50) has a surface normal at the proximal point, and wherein - the front surface comprises at least a first portion, which is angled towards the oncoming airflow and the leading edge of the blade so that an average tangent or median line to said first portion forms a first angle (Θ) with the surface normal being larger than 0 degrees, wherein the average tangent further is angled forward compared to a second normal to the chord, so that the median line and the second normal forms a second angle (α) being at least 5 degrees, and wherein - the flow guiding device is adapted to generate a separation of airflow downstream of the flow guiding device between the flow guiding device and the trailing edge of the blade, and wherein - the front surface is concave.