Binary Water Droplet Collision Issue

oscar_z · August 22, 2024, 11:56

Hi,

I'm currently simulating binary water droplet collisions using STAR-CCM+ with the following parameters:

- Droplet Diameter: 400 microns
- Water Density: 1000 kg/m³
- Water Viscosity: 0.001 Pa·s
- Air Density: 1 kg/m³
- Air Viscosity: 1.8e-5 Pa·s
- Surface Tension: 0.072 N/m
- Relative Velocity: 1 m/s
- Mean CFL Number: 0.5
- Max CFL Number: 1.0

I placed one droplet in a box that is 800 microns long with all six surfaces set as Symmetry Planes. The droplet is given a [1, 0, 0] velocity to make it hit the right surface. However, the droplet deforms significantly as it travels.

Could someone please advise on what might be wrong with my simulation? I have attached some pictures for reference.

Isosurface.jpg

Mesh.jpg

Models Used.jpg

Thank you!
Oscar

Voluped · August 27, 2024, 09:39

Consider using a different boundary condition, such as no-slip walls for the surfaces that the droplet may contact. Also An 800-micron box might be too small for a 400-micron droplet, especially given the high relative velocity.

JBeilke · August 27, 2024, 16:02

I did similar things in the past and it never worked with AMR. Best to use a fine cartesian mesh with all cells of the same size.

August 22, 2024, 11:56	Binary Water Droplet Collision Issue	#1
oscar_z New Member Join Date: Aug 2024 Posts: 1 Rep Power: 0	Hi, I'm currently simulating binary water droplet collisions using STAR-CCM+ with the following parameters: - Droplet Diameter: 400 microns - Water Density: 1000 kg/m³ - Water Viscosity: 0.001 Pa·s - Air Density: 1 kg/m³ - Air Viscosity: 1.8e-5 Pa·s - Surface Tension: 0.072 N/m - Relative Velocity: 1 m/s - Mean CFL Number: 0.5 - Max CFL Number: 1.0 I placed one droplet in a box that is 800 microns long with all six surfaces set as Symmetry Planes. The droplet is given a [1, 0, 0] velocity to make it hit the right surface. However, the droplet deforms significantly as it travels. Could someone please advise on what might be wrong with my simulation? I have attached some pictures for reference. Isosurface.jpg Mesh.jpg Models Used.jpg Thank you! Oscar

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August 27, 2024, 09:39		#2
Voluped New Member Join Date: Oct 2023 Posts: 6 Rep Power: 2	Consider using a different boundary condition, such as no-slip walls for the surfaces that the droplet may contact. Also An 800-micron box might be too small for a 400-micron droplet, especially given the high relative velocity.

August 27, 2024, 16:02		#3
JBeilke Senior Member Joern Beilke Join Date: Mar 2009 Location: Dresden Posts: 511 Rep Power: 20	I did similar things in the past and it never worked with AMR. Best to use a fine cartesian mesh with all cells of the same size.