CHARACTERISTICS OF 2-DIMENSIONAL WAVES ON A FALLING LIQUID-FILM

Regularly spaced two-dimensional waves are excited with input of contr olled disturbances to a water film falling down a vertical surface, an d phase velocities u(w), wave peak heights h(p) and wave separations l ambda are measured for a wide range of flow rates (Gamma = 20 similar to 86 x 10(-6) m(2)/s) and temperatures (5 similar to 23 degrees C) (c orresponding to Reynolds numbers Re = 14 similar to 90). The variables h(p) and u(w) are well described by the relations N-uw = 1.13K(F)(0.0 2)N(lambda)(0.31)Re(0.37) and N-hp = 0.49K(F)(0.044)N(lambda)(0.34)Re( 0.46), and also by N-hp = 0.425K(F)(0.019)N(uw)(5/4) and N-uw = 1.13K( F)(0.026)N(V)(1/2) where N-uw, N-hp, N-lambda, K-F N-V and Re are resp ectively dimensionless phase velocity, wave peak height, wave separati on, physical properties group, volume of liquid carried on a wave and Reynolds number. These correlations show that the two variables lambda and Gamma can be replaced by one variable, V or u(w), and they theref ore indicate that the waves are isolated from each other. Comparisons between these correlations and data obtained from the extensive litera ture on the subject are discussed in relation to the surface elasticit y. Shadowgrams of waves are also presented.