Fig. 3

\({\hat{\text{R}}}_{\text{o}} = 1\) contour lines for different temperatures. Observed points for \({\hat{\text{R}}}_{\text{o}} = 1\) (circles) were fitted with natural logarithmic functions (solid lines) on the non-dimensional D₁–D₂ space for each temperature, where D₁ = T_wet/T_o and D₂ = T_on/T_int. The x-axis in this figure is shown on a logarithmic scale. Each color represents a different temperature, which applies both to the circles and the lines. No line was drawn for 19 ◦C because almost no combination of conditions lead to \({\hat{\text{R}}}_{\text{o}} > 1\). A natural logarithmic function fitted to all the observed points of \({\hat{\text{R}}}_{\text{o}} = 1\) reads as D₂ = −0.27 log D₁ + 0.94 (≡f_o), and the area ±1.5 in y-direction from it is denoted as transient zone. Note that the figure contains the results from all the values of T_wet, T_on and X_dist tested, as well as temperatures