Simulation of gravity currents using the thermal lattice Boltzmann method

Abstract

SUMMARYThe lattice Boltzmann method (LBM) is becoming an effective numerical technique of computational fluid dynamics (CFD). In this study, with some new thermal LBM schemes being proposed, the LBM is used to simulate the gravity current prior to backdraft (a particular and hazardous phenomenon in compartment fire) within laminar restrictions. The dimensionless time for gravity current traveling from the opening to the rear wall of a bench-scale compartment is calculated under different opening geometries, respectively, including: full end opening, upside-slot end opening, middle-slot end opening, downside-slot end opening, and slot ceiling opening. The application is very successful and the results show that the dimensionless time under the slot ceiling opening is the longest. Among the slot end openings, similar dimensionless time has been obtained for the upside-slot and middle-slot end openings, which is shorter than the downside-slot end opening. For the full end opening, the shortest dimensionless time is obtained. Finally, some valuable advices are given for fire protection engineering.

Development of a lattice Boltzmann method for two‐layered shallow‐water flow

“…Last but not least, it is interesting to observe that the values of the y velocity component, calculated by the LBM, had an order of magnitude belonging to the range: 10 6 6 O .v/ 6 10 4 ms 1 . This fact shows the consistency of the LBM numerical simulation, because the geometry of the fluid domain causes a shallow-water flow with negligible y velocity component, described theoretically by the 1D shallow-water Equation (18). The percentage of mass variation had an order of magnitude of: O(10 5 -10 4 /% for all of the considered LBM simulations and so it is possible to claim that the conservation of mass was complied with.…”

“…In the past decades this different perspective has been developed in fluid mechanics and has led to the formulation of an efficient and robust model, valid for several flows . The main idea is that the macroscopic description of the flow, that is, the description made by means of fields of macroscopic quantities (pressure, velocity components, temperature, etc.)…”

“…An interesting strategy, aimed to overcome such difficulties, could consist in formulating a completely different mathematical model of the same flow, starting from a different perspective. In the past decades this different perspective has been developed in fluid mechanics and has led to the formulation of an efficient and robust model, valid for several flows [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. The main idea is that the macroscopic description of the flow, that is, the description made by means of fields of macroscopic quantities (pressure, velocity components, temperature, etc.)…”

“…Since its introduction in fluid mechanics, the LBM has had a tremendous development, which is continuing and is documented by the huge production of scientific works. This is not the right place to give a detailed review of the literature, but it is worth mentioning the most important recent books and papers [12][13][14][15][16][17][18][19][20][21] on the topic. The reason for such a powerful development is the intrinsic simplicity of the LBM in representing even complex flows as multiphase flows, flows in complex boundaries, turbulent flows, etc.…”

Hydrodynamic analysis of fully developed turbidity currents over plane beds based on self‐preserving velocity and concentration distributions

“…In the same line, the large eddy simulation along with direct numerical simulation was also applied to simulate the turbidity currents [Mahdinia et al, 2011;Dutta et al, 2012]. On the other hand, as a new trend in simulation of gravity currents, the application of the thermal lattice Boltzmann method was also reported [Lizhong et al, 2011;Prestininzi et al, 2013]. However, in derivation of the full depth-averaged models, similarity solutions were sought for the convenience [Parker et al, 1986], assuming the velocity, concentration, and TKE distributions to preserve similarity.…”