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, first, 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 “practically ergodic.” 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. 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.
The research leading to these results has received funding from the Spanish Ministry for Science and Innovation under Grant No. TRA2010-16988, “Caracterización Numérica y Experimental de las Cargas Fluido-Dinámicas en el transporte de Gas Licuado.” Part of this work was carried out while G. Bulian was at ETSIN-UPM in two occasions, in the framework of the “Lifelong Learning Programme Italia - Erasmus - Staff Mobility for Teaching” (2012, 2013). The authors would also like to acknowledge the support of Jordi Mas-Soler (ETSIN-UPM) and Filippo Castellana (DYNATECH - University of Genova) during the experimental campaign, UPM-INSIA Angel Martin for assistance in the vibration measurements and GTT staff, namely Laurent Brosset, Eric Gervaise and Thibaut Loysel, for providing access to the PCB sensors set. Finally, the authors thank Hugo Gee for the English proof-reading of the article.
II. CASE STUDY AND EXPERIMENTAL SETUP
III. THE PHYSICAL PHENOMENON
IV. STATISTICAL ANALYSIS OF IMPACT PRESSURE
A. General considerations
B. Ensemble domain analysis of maximum impact pressure: Identification of transient and stationary regions
C. From ensemble domain to time-domain: Justifying the usual working assumption of (practical) ergodicity
D. Checking for linear correlation between different events
E. Consequences of the assumption of independent identically distributed (i.i.d.) maximum impact pressures at different impact events and of (practical) ergodicity
- Statistical analysis
- Impact phenomena
- Impact testing
- Free surface
- High pressure
Data & Media loading...
Article metrics loading...
Full text loading...