Two successive drops impinging onto an inclined steel plate

The impact characteristics of two successive water drops impinging onto a steel plate with various oblique angle were experimentally investigated by using the free-falling drop technique incorporated with a drop severance device. The experiments had focused particularly on the influence of the oblique angle (Φ =15° and 45°) of the impinged solid surface on the impact phenomena. The single drop impinging process was firstly examined as a reference, namely Case 1. Thereafter, based on the result of Case 1, the second drop was introduced to achieve two successive drops impingement at three different impinging conditions identified by the time intervals (Δt), namely Case 2: Δt = Δt1 (the leading drop starting spreading); Case 3: Δt = Δt2 (the leading drop reaching its maximum spreading); and Case 4: Δt =Δt3 (the leading drop reaching its maximum height in the contract process). For a given initial drop diameter, the spreading diameter (dw) increased as the oblique angle increased from Φ =15°~ 45°. As the oblique angle was further increased to 45°, the spreading diameter reached its maximum value and stabilized. The maximum film height was obtained under the impinging condition of Case 3 for all of the considered oblique angles (Φ = 15° and 45°). As the oblique angles increased, the steady height of the drop decreased.