| Description |
1 online resource (19 pages) : illustrations (chiefly color). |
|
text txt rdacontent |
|
computer c rdamedia |
|
online resource cr rdacarrier |
| Series |
NREL/PR ; 2C00-72822 |
|
NREL/PR ; 2C00-72822.
|
| Note |
Slideshow presentation. |
|
"AlChE Annual Meeting 2018, Pittsburch, PA, USA, 29th October 2018." |
| Bibliography |
Includes bibliographical references. |
| Funding |
DE-AC36-08GO28308 |
| Note |
Description based on online resource; title from PDF title page (NREL, viewed April 29, 2022). |
| Summary |
The time integration of the granular phase in coupled computational fluid dynamics (CFD) - discrete element method (DEM) simulations presents a unique computational challenge brought about by the large variations in particle collisional time scales. Particles in the dilute regions of the computational domain can be advanced with large time steps while dense regions require much smaller time increments. However, the time step size in most solvers is globally set as the limit for accuracy and stability imposed by the collisions and is typically orders of magnitude less than that required away from collisions. This work addresses this precise issue and provides a strategy to avoid the use of a global conservative small time step size for the entire set of particles.A novel time stepping algorithm for CFD-DEM solvers using a partitioning approach using orthogonal recursive bisection (ORB) that allows for variable time steps among particles is described and its computational performance is compared against baseline explicit methods, typically used in several CFD-DEM solvers. ORB has advantages of being relatively quick and easy to update incrementally and has the required heuristic behavior (i.e., it will split the region in half with a cluster on each side) when groups of particles are well separated (clustered). The algorithm presented in this work uses a local time stepping approach to resolve collisional time scales for subsets of particles that are present at the leaves of the ORB, thereby resulting in substantial reduction of computational cost. The parallel implementation of this method where a ``knapsack" algorithm is used in tandem with ORB for effective load-balancing is also presented, where a best possible partitioning is obtained based on number of particles and local time-stepping costs. The algorithm is tested against benchmark problems with varying particle distributions that include fluidized bed and riser flow scenarios. Preliminary results indicate that the approach is 2-3X faster than traditional explicit methods for problems that involve both dense and dilute regions, while maintaining the same level of accuracy. |
| Subject |
Cooling systems -- Mathematical models.
|
|
Computational fluid dynamics.
|
|
Discrete element method.
|
|
Systèmes de refroidissement -- Modèles mathématiques.
|
|
Dynamique des fluides numérique.
|
|
Méthode des éléments discrets.
|
|
discrete element method.
|
|
Computational fluid dynamics
|
|
Discrete element method
|
| Indexed Term |
adaptive timestepping |
|
computational fluid dynamics |
|
discrete element method |
| Added Author |
Grout, Ray, author.
|
|
National Renewable Energy Laboratory (U.S.), issuing body.
|
|
United States. Office of Fossil Energy, sponsoring body.
|
| Added Title |
Orthogonal recursive bisection (ORB) based time advancement algorithm for computational fluid dynamics-discrete element method solvers |
| Standard No. |
1823579 OSTI ID |
| Gpo Item No. |
0430-P-09 (online) |
| Sudoc No. |
E 9.22:NREL/PR-2 C 00-72822 |
|
