Getting to know NFLOW LBM : Two-dimensional Flow Simulation

The second episode of NFLOW LBM is on the two-dimensional cavity flow.

Unlike the previous simulation where a flow around a cylinder in a pipe was simulated using the LBM with SRT (Single Relaxation Time), the two-dimensional cavity flow was simulated using the LBM with MRT (Multiple Relaxation Times).

NFLOW LBM uses the Boltzmann Equation to simulate flows and is especially useful for modeling and computing phase separation, evaporation, condensation and heat transfer.

Additionally, parallelizing NFLOW LBM is easy due to the local nature of the calculations. It has a high calculation speed and is expected to be widely used in various industries, including aerospace, biology, semiconductors, and more.

The video footage below shows a two-dimensional lid-driven cavity flow simulated using the LBM with MRT.

< Lid-driven cavity flow >

A cavity refers to a hollow space. In the cavity shown above, when the upper wall moves in one direction with a constant velocity, it drives an internal flow within the cavity. The simulation above shows that the velocity of the wall gradually develops the flow inside the cavity due to the viscosity of the fluid.

With SRT, all moments have the same relaxation time, which fixes Prandtl number to a single value. By using MRT, one can use different relaxation times for different moments and therefore can use different Prandtl number for different moments.

Also, using SRT to simulate high Reynolds number flows typically leads to numerical instability. MRT can mitigate this numerical instability with a slight increase in the number of calculations and be used obtain stable solutions in scenarios where SRT solvers are numerically unstable.

In this simulation, a lid-driven cavity flow with Reynolds number of 7,500 and the cavity aspect ratio of 1.5 is simulated using the LBM with MRT. It was not possible to simulate this flow using SRT due to the numerical instabilities, whereas by using MRT, it was possible to obtain a stable solution.

The 2D lid-driven cavity flow is a very well-established flow case with a lot of published data to compare against. By using the LBM with MRT to simulate the lid-driven cavity flow, we were able to verify that our LBM solver can accurately simulate flows with moderately high Reynolds numbers.

So far, we have introduced <Two-dimensional cavity flow simulation> using NFLOW LBM.

NFLOW LBM will be officially launched soon and will show high-performance and realize your product within a short time.

Please look forward to our new official launch. Thank you.

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