This experimental work characterises the fluid response of isothermal water in a horizontal cylinder (Fig. 1) with a fill level of 30%. This parametric study investigates three forcing amplitudes and eleven forcing frequencies for each respective amplitude. Images captured using a high-speed camera are used to quantify global sloshing amplitudes, using the lateral motion of the centre of gravity (COG). Free surface elevations at the left and right sidewalls are also quantified. The maximum displacements obtained, for all three forcing amplitudes tested, show a softening non-linear response. In this work we refer to the maximum response as the largest sloshing amplitude recorded for each forcing amplitude (A). We show asymmetry in the steady state between the left and right sidewall run up, where the forcing amplitude (A = 2mm) and the excitation frequency ratio is near its maximum response.
The aviation industry is committed to make net-zero carbon aviation a reality. A promising alternative fuel for commercial aviation is liquid hydrogen (LH2). This fuel has the potential to reduce the environmental impact of the aviation sector, alongside this, the inherently high specific energy density (nearly three times that of traditional aviation fuel) makes LH2 a natural alternative fuel. LH2 is a cryogenic fluid, cryogenic fuel tanks typically have a similar shape to that of any common pressure vessel, where curved geometries are utilised to remove high stress areas at sharp corners. Thus, the geometry being considered in this research (Fig. 1) is a horizontally orientated cylinder. This presents a novel aspect of this work, as most sloshing research has focused on: upright cylinders, spherical containers, and rectangular geometries.
There are a wide range of engineering challenges related to LH2 fuel tanks that must be addressed, one of these challenges being pressure variations in LH2 fuel tanks. In the past, rapid pressure drops have been reported in both experimental campaigns and operational environments with cryogenic fluids (Ludwig et al., 2013; Montsarrat, 2017; Moran et al., 1994). This pressure drop stems from liquid sloshing, where complex fluid motion leads to heat and mass transfer and the associated pressure variations. This phenomenon could lead to structural instability, saturation of the liquid phase, cavitation, and consequent issues with fuel delivery to the consumer. Experimental testing with LH2 has displayed that the rate of condensation and thus pressure drop is greater for large amplitude sloshing (Moran et al., 1994). This has also been demonstrated in experimental tests with liquid nitrogen where the dependency of wave amplitudes on pressure drop has been investigated (Ludwig et al., 2013). A critical Reynolds number (Eq. 1) containing wave amplitude (b), angular wave frequency (ω) and kinematic viscosity (υ) was proposed (Ludwig et al., 2013). Below the critical Reynolds number sloshing does not distinctly effect heat transfer. Therefore, there is no significant pressure drop below the critical Reynolds number.
