Getting to know "NFLOW LBM"


< Simulation of a flow around a cylinder in a pipe >

We’ve brought you an update regarding “NFLOW LBM” !

NFLOW LBM might sound unfamiliar because up until now, we’ve been only posting news about NFLOW SPH.

NFLOW LBM will soon be officially launched, and today we’re going to take a look at a simulation done with NFLOW LBM.

First, let’s learn about LBM.

LBM is the abbreviation of the “lattice Boltzmann Method”, which uses the particle distribution (a probability density function) to simulate fluid flow.

On the other hand, traditional grid-based CFD solvers are Eulerian, which randomly divide the simulation space and find the approximate solutions to the Navier-Stokes equations. It calculates the approximate solution at each discretized cell. Traditional CFD methods require a tremendous time and effort in discretizing the solution space to accurately model the geometry and flow regions of interest.

Furthermore, traditional CFD methods solve for steady-state flows, and may have limitations in accurately describing the physics of a highly unsteady flow. LBM is being regarded as a noteworthy alternative to overcome to shortcomings of traditional grid-based Eulerian CFD solvers.

The LBM models geometries with boundary conditions and do not require the generation of a complex grid. Complex geometries can be resolved with a combination of uniform, higher-density grid blocks near the surface and the appropriate boundary conditions. Additionally, as LBM is inherently an unsteady flow solution method, it is not limited to solving quasi-steady flows. NFLOW LBM can be used for a variety of situations, including accurate and efficient thermal conduction analysis, turbulent flow analysis, highly unsteady flow analysis, and HVAC simulation.

Now, let’s take a look at a simple simulation done by NFLOW LBM.

< Simulation around a cylinder in a pipe >

Can you see the motion of the fluid in the video footage?

This video footage shows the flow around a cylinder in a pipe, which is an incompressible, isothermal flow. It’s a simple flow that’s often used to validate the accuracy of a solver.

What is an incompressible, isothermal flow?

It refers to a flow where changes in the density and temperature of a fluid volume are negligible during the flow.

Through the video, we were able to observe the unsteady flow around a cylinder as fluid moves through a pipe.

The table below compares the drag coefficient of the cylinder between that obtained from NFLOW LBM and that from literature, when the Reynolds number is 100. It demonstrates that NFLOW LBM predicted the drag coefficient of the cylinder in this flow within a 1.5% margin with that published in literature, and serves as evidence for its fidelity.

So far, we’ve looked at NFLOW LBM as it solves a simple flow.

We will continue to update you with news related to NLOFW LBM!

Please look forward to future updates regarding NFLOW LBM and E8IGHT!

Thank you :)

Image Source :

Bao, Y.B., Meskas, J.: Lattice Boltzmann Method for Fluid Simulations. Department of Mathematics, Courant Institute of Mathematical Sciences, New York University, New York (2011)

Ref[*] Djebedjian, B., Renaudeaux, J.P. et Giat, M., Numerical Study of the Drag Coefficient of an Infinite Circular Cylinder at Low and Moderate Reynolds Numbers using the FLUENT Code, Proceedings of the International Congress on Fluid Dynamics and Propulsion, December 29-31, 1996, Cairo, Egypt, Vol. III, pp. 771-781.

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