A set of canonical problems in sloshing. Part 2: Influence of tank width on impact pressure statistics in regular forced angular motion

Continuing along the path of previous papers in this series, the present paper addresses, experimentally, sloshing in a rectangular tank under harmonic angular forcing. Since lateral and roof impacts are relevant in sloshing assessment and present distinct dynamics, these have been studied. Water and oil have been used in order to obtain data for high and moderate Reynolds numbers. With the aim of addressing effects induced by the three-dimensionality of the flow, a study of the influence of the tank width on pressure statistics has also been conducted. For this purpose, a tank which can be adjusted to 4 different widths by replacing the side plates was built. For each combination of fluid, tank width and filling level, a total of 120 experiments, each comprising 120 peaks, have been conducted, allowing an analysis in time and ensemble domains to be performed. Impact pressure statistics are presented including mean values, percentiles, and exceedance probability graphs

A set of canonical problems in sloshing. Part 0: Experimental setup and data processing

In a series of attempts to research and document relevant sloshing type phenomena, a series of experiments have been conducted. The aim of this paper is to describe the setup and data processing of such experiments. A sloshing tank is subjected to angular motion. As a result pressure registers are obtained at several locations, together with the motion data, torque and a collection of image and video information. The experimental rig and the data acquisition systems are described. Useful information for experimental sloshing research practitioners is provided. This information is related to the liquids used in the experiments, the dying techniques, tank building processes, synchronization of acquisition systems, etc. A new procedure for reconstructing experimental data, that takes into account experimental uncertainties, is presented. This procedure is based on a least squares spline approximation of the data. Based on a deterministic approach to the first sloshing wave impact event in a sloshing experiment, an uncertainty analysis procedure of the associated first pressure peak value is described

Repeatability and Two-Dimensionality of Model Scale Sloshing Impacts

Canonical test cases for sloshing wave impact problems are presented and discussed. In these cases the experimental setup has been simpli\ufb01ed seeking the highest feasible repeatability; a rectangular tank subjected to harmonic roll motion has been the tested con\ufb01guration. Both lateral and roof impacts have been studied, since both cases are relevant in sloshing assessment and show speci\ufb01c dynamics. An analysis of the impact pressure of the \ufb01rst four impact events is provided in all cases. It has been found that not in all cases a Gaussian \ufb01tting of each individual peak is feasible. The tests have been conducted with both water and oil in order to obtain high and moderate Reynolds number data; the latter may be useful as simpler test cases to assess the capabilities of CFD codes in simulating sloshing impacts. The repeatability of impact pressure values increases dramatically when using oil. In addition, a study of the two-dimensionality of the problem using a tank con\ufb01guration that can be adjusted to 4 di\ufb00erent thicknesses has been carried out. Though the kinematics of the free surface does not change signi\ufb01cantly in some of the cases, the impact pressure values of the \ufb01rst impact events changes substantially from the small to the large aspect ratios thus meaning that attention has to be paid to this issue when reference data is used for validation of 2D and 3D CFD codes

Experimental sloshing pressure impacts in ensemble domain: Transient and stationary statistical characteristics

The present paper focuses on the analysis of impact pressure registrations from repeated model scale sloshing experiments under harmonic rotational excitation. A series of more than 100 experiments, each one encompassing more than 100 impact events, has been conducted seeking the highest feasible repeatability. Different excitation periods, that cover the main features of the impact dynamics, have been considered in a preliminary screening, describing the main features of the impact dynamics. Since, even under a nominally deterministic excitation, the pressure at each impact is characterized by a high variability, a statistical approach is used treating the impact pressure as a stochastic process. For one selected excitation period, the statistical analysis focuses on the ensemble distribution of the maximum pressure during each impact event. Particular attention is given to the evolution of such distributions, in order to detect the variations in the statistical characteristics of the process. This is achieved by, \ufb01rst, identifying the presence and the length of the transient phase and, second, by characterizing the process at stationary state. The statistics of impact pressure for different peaks are discussed mostly in the ensemble domain. Linking the latter with the time domain analysis is made by checking that the problem can be considered \u201cpractically ergodic.\u201d The \u201cpractical ergodicity\u201d of the process is dealt with by checking to what extent steady state ensemble statistical information can be obtained from a single long run experiment. Statistical checks for correlation and independence of maximum impact pressures are also carried out to test the hypothesis of independent identically distributed random variables. The method of analysis presented in this paper through the considered example case is general in nature and is considered to be highly portable. In particular, it is considered to allow for a more thorough understanding of non-deterministic events such as those considered herein, by looking at them from a sound statistical perspective. The thorough description of the whole experimental setup makes the presented data suitable for comparison purposes and for validation of theoretical/numerical approaches

Three SPH Novel Benchmark Test Cases for free surface flows

Abstract\u2014Benchmark Test Cases have been used by SPHERIC interest group members for the validation of SPH models and their corresponding computer implementations. Since the use of SPHERIC benchmark test cases as validation reference for SPH implementations has slightly declined in the most recent editions, we think it might be interesting to document three novel test cases with the aim of enriching the database with complementary validation data. The first proposed test case is a wave impact problem in a rectangular tank. The time history of the motion of the tank and the pressure of the first instances of lateral and roof impacts for both water and oil are provided. An analysis of the two-dimensionality and repeatability of the pressure peaks is provided. The second proposed test case treats the coupling of the angular motion of a sloshing tank and a single degree of freedom structural system. Finally, the third proposed test case, is a canonical fluid structure interaction problem consisting in the interaction between a free surface sloshing flow and an elastic body. As both SPH practitioners and experimentalists, regardless of the discussion provided in this paper, we are committed to improving these test cases for future use. We hope to increase our experimental skills and capabilities not only in light of experience from our own simulations but mainly by receiving a feedback from the SPH community

Repeatability and Practical Ergodicity of 2D Sloshing Experiments

The present paper focuses on the statistical analysis of impact pressure peaks registers in 2-D harmonic motion model scale sloshing experiments. A series of 100 experiments each comprising about 100 impact events has been conducted, seeking the highest feasible repeatability. The statistical analysis focuses on the ensemble distribution of the maximum pressure during these impact events. Particular attention is given to the time domain evolution of such distributions, in order to separate stochastic transient from stochastic steady state. Statistical characteristics of impact pressure for different peaks are discussed in the ensemble domain. Particular attention is given to the connection between the characteristics of the ensemble distribution of impact pressure and the process of CFD validation. Finally, the (practical) ergodicity of the process is dealt with by checking to what extent steady state ensemble statistical information can be obtained from a single long run experiment

A combined Experimental and SPH Approach to Sloshing and Ship Roll Motions

Passive anti-roll tanks have been used for a long time in ships to damp their roll motion. The coupled roll motion response of a single degree of freedom (SDOF) system to which a passive anti-roll tank has been attached is considered in the present paper. The performance of the anti-roll tank has been studied both experimentally and numerically, with weakly compressible SPH. The sloshing flows inside the tank comprise the onset of breaking waves. In order to characterise the wave breaking effects on the response curves, tests have been performed with liquids of different viscosity, the increasing viscosity preventing the onset of breaking waves. The capabilities of SPH to treat this coupling problem are assessed and the results show that SPH is able to capture a part of the physics involved in the addressed phenomena but further work remains still to be done