Dynamic hydraulic jumps in oscillating containers

When the liquid in a tank undergoes sudden movement, as in the case of a :Fuel tank in an aircraft or in a marine vessel, it may be subjected to as many as 6 degrees of freedom. Three of these are in rotation; yaw, pitch and roll, and three in translation; sway, surge, and heave. Work is currently being conducted on simulating the effects of the liquid motion under roll conditions i;1 a rectangular tank of dimensions 1.9 x 0.94 x 1.2 m(3) located on a 6 degree of freedom simulator capable of mimicking the movements typical of an aircrafts performance. At present, water is being used to investigate the fluid motion when subjected to oscillating roll frequency of 0.35 Hz and oscillation amplitudes of 2.42(0), 3.50(0), and 4.71(0) for different liquid depths. It has been found that under such motions, typical of those obtained within the flight envelope of military, private and commercial aircraft, a dynamic hydraulic jump can occur. This jump is out of phase with the roll motion and is produced as the fluid abruptly changes direction within the tank. As the tank reaches its lowest rotational position in the roll manoeuvre the fluid level at this point of the tank increases rapidly against the end wall causing splashing, resulting in bubble formation and a fine spray. This change in direction increases the fluid depth and this has to move against the residual oncoming fluid that is at a much lower depth, resulting in a very dynamic, moving, wave that breaks and forms into a hydraulic jump comprised of air and liquid mixing. This preliminary investigation into the characterization of this phenomenon using water shows that the spatial characteristics of the hydraulic jump and the dynamic range of the resultant spray are affected by the amplitude of the tank oscillation.