Simulation of Single sphere settling in water

[Christopher Cheung]

Dear all，

Recently, I am using openlb’s particle module to simulate the settlement of a sphere in a fluid (water). The process is as follows:

A box with dimensions of 2 m × 2 m × 4 m is full of water and a
sphere is placed in the water at the height of 3.5 m. The sphere starts moving under the action of gravity and its movement is influenced by the forces from water, including the buoyancy and viscous force.

The LBM domain is discretized into a lattice of
50 × 50 × 100 cells and the grip spacing of the lattice is δx = 0.04 m.

The DEM sphere is placed inside the domain and the radius of
the sphere is 0.25 m, about 6.25 LBM cells. The density of sphere is ρ = 1250 kg/m3. The Poisson’s ratio of the sphere is 0.3 and the Young’s modulus is 1 × 108 Pa. The density of the fluid is ρ = 1000 kg/m3, the kinematic viscosity is v = 10−4 m2/s.

I referred to the examples of “bifurcation3d” and “magnetic particles Euler-Larange” in OpenLB.

However, my problem is that there is no change in the surrounding fluid (including velocity and pressure) during the settlement of the sphere, which seems to be because the sphere is not acting on the liquid. So I would like to ask how I should solve this problem.

[mathias]

Dear Cheung,

we have several models implemented in OpenLB. The one your have chosen is a sub-grid model with no-back coppling. So what you observe is corect.

An overview about particle-fluid models you will find in https://publikationen.bibliothek.kit.edu/1000061601 .

Further, I recomment our next spring school. There, we offer a talk and hands on on at least two different model implentations in OpenLB.

Best
Mathias

[Christopher Cheung]

Dear Mathias
Thank you so much. I’m referring to the paper you recommended to me. It does give me some guidance， to some extent, it solved my confusion.

Best
Cheung

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