Top panels: changes in velocity (left-hand panel) and density (right-hand panel) to 10R₁ in the equatorial plane of the 3D wind model around the primary star due to orbital motion towards the south. In front of the star (blue colour in online figure) the wind velocity difference in the observer’s frame decreases from V_r =  −85 km   s^-1 at the surface to > −10  km   s^-1 for r > 3R₁. Behind the star (red colour in online figure) it increases from −85 km   s^-1 to <10 km   s^-1 for r > 3R₁. At larger distances from the surface the difference of wind velocity with the stationary wind (V_r = 0) model is <10 km   s^-1 and becomes symmetric in all directions around the binary. Bottom left-hand panel: wind velocity for ψ = 0 (solid drawn line), π/3 (dash-dotted line), 2π/3 (dashed line), and π (short-dashed line). The curves are shifted to the right by + 1R₁ for clarity. Bottom right-hand panel: radial wind density contrast at these ψ angles for f = 1 (see Sect. 5.2).