Three-Dimensional Simulation of Balloon Dynamics by the Immersed Boundary Method Coupled to the Multiple-Relaxation-Time Lattice Boltzmann Method - Volume 17 Issue 5 - Jiayang Wu, Yongguang Cheng, Chunze Zhang, Wei Diao

With the implementation of the most stringent water resources management system and the advancement of the construction process of reservoir terrace basins, the research and application of the theory and method of joint operation of reservoir groups are becoming more and more important. The Differential Evolution Adaptive Metropolis (DREAM) algorithm is a sampling algorithm based on the Markov Chain Monte Carlo method proposed in recent years. The algorithm satisfies ergodicity and is good at handling problems with multivariate nonlinearity, high dimensionality, and multi-peaks, and as such the algorithm is a new global optimization solution. This paper elaborated the solution mechanism of the standard DREAM algorithm, and the algorithm was applied to the optimal operation model of the reservoir group in Jialing River. First, we optimized and analyzed the multi-objective supply operation model of the reservoir group water in Jialing River. Then the multi-attribute decision-making and evaluation index system of water supply operation rules for the reservoir group to assess the optimization of the operation model was adopted. Finally based on the results of the evaluation, the best water supply operation scheme for the reservoir group of Jialing River was selected. The results show that the Baozhusi Reservoir can fully meet the planned water supply requirements in dry years, while the two reservoirs, Shengzhong and Tingzikou, need to be weighed against the evaluation indexes of water supply operation. The research provides a theoretical basis for the DREAM algorithm in the optimal operation of the reservoir group and the actual operation scheme for the reservoir group of Jialing River.

The temperature distribution and pollutant distribution in large reservoirs have always been a hotspot in the field of hydraulics and environmentology, and the three‐dimensional numerical modeling that can effectively simulate the interactions between the temperature fields, concentration fields, and flow fields needs to be proposed. The double‐diffusive convection lattice Boltzmann method is coupled with a single‐phase volume of fluid model for simulating heat and contaminant transfer in large‐scale free surface flows. The coupling model is used to simulate the double‐diffusive natural convection in a cubic cavity and the temperature distribution of a model reservoir. The mechanism of convection‐diffusion, gravity sinking flow, and the complexity of the temperature and the pollutant redistribution process are analyzed. Good agreements between the simulated results and the reference data validate the accuracy and effectiveness of the proposed coupling model in studying free surface flows with heat and contaminant transfer. At last, the temporal and spatial variations of flow state, water temperature stratification, and pollutant transport in the up‐reservoir of a pumped‐storage power station are simulated and analyzed by the proposed model. The obtained variations of the flow field agree well with the observations in the physical model test and in practical engineering. In addition, the simulated temperature field and concentration field are also consistent with the general rules, which demonstrates the feasibility of the coupling model in simulating temperature and pollutant distribution problems in realistic reservoirs and shows its good prospects in engineering application.

Water wave dynamics and its engineering application have always been a key issue in the field of hydraulics, and effective and efficient numerical methods need to be proposed to perform three-dimensional (3-D) simulation of large-scale water fluctuation in engineering practice. A single-phase free-surface lattice Boltzmann method (SPFS-LB method) is coupled with a large-eddy simulation approach for simulating large-scale free water surface flows, and the simulation is accelerated on a GPU (graphic processing unit). The coupling model is used to simulate the evolution process of dam-break wave after complete and partial dam-break. The formation mechanism of horizontal and vertical vortices in water after partial dam-break and the advance and evolution process of dam-break flow on non-contour riverbed are analyzed. The method has been verified to be reasonable and can obtain a more accurate time curve of water level fluctuation. Applying this method to practical arch dams, discharge coefficients consistent with empirical formulas can be obtained by comparison and analysis, and the surface flow phenomena (such as tongue diffusion, surface fragmentation, and surface fusion) can be well simulated by this method. In addition, based on the key technology of parallel computing on a GPU, the implementation of the SPFS-LB model on a GPU unit achieves tens of millions of lattice updates per second, which is over fifty times higher than that on a single CPU chip. It is proved that the proposed method for large-scale water fluctuations can be used to study practical engineering problems. The mathematical model method realizes the efficient and accurate simulation of practical physical problems.

Landslide-induced tsunami waves pose significant risks to vessels navigating or anchored in affected water bodies. To address this issue, a validated smoothed particle hydrodynamics (SPH) framework coupled with Delta-SPH method and Shifting Algorithm was assessed and then employed to investigate the impact of such waves on vessels, considering key influential factors such as landslide thickness, length, initial position, initial water depth, vessel width, and slope-to-vessel distance. The results indicate that the heave and sway motions of the vessel are primarily influenced by the initial wave, while the roll motion is mainly affected by the secondary waves. Among the parameters examined, the landslide thickness, slope-to-vessel distance, and initial water depth have the most significant effects on the maximum heave, sway, and roll values, with relative differences of 125.5%, 177.4%, and 223.0%, respectively. Variations in initial water depth led to different landslide motion patterns: the riverbed movement pattern and the chute movement pattern, which predominantly govern the generation process of secondary waves. Additionally, prediction equations for the maximum heave, sway, and roll motions of were proposed to quantitatively assess the impacts of various initial factors on vessel motion characteristics. The prediction equations reveal that the heave motion is predominantly affected by the landslide volume, the sway motion is predominantly affected by the slope-to-vessel distance, and the roll motion is primarily governed by the landslide length and initial water depth. The research provides insight into the dynamic responses of vessels under landslide-induced tsunami waves, offering valuable guidance for disaster prevention and mitigation efforts.