SPH simulation for flows that splash, churn and break apart
Smoothed particle hydrodynamics follows liquid as moving particles rather than through a fixed mesh, which makes it the practical way to see how oil moves in a gearbox, how a stirred tank mixes or how liquid slams inside a tank.
Some free-surface flows are too violent or too tangled for conventional CFD. Oil thrown off gear teeth breaks into sheets and droplets, water breaking over a deck lands as green water, and liquid slamming inside a tank folds over on itself. Meshing the fluid around moving gears and shafts, and following a surface that keeps fragmenting, is where mesh-based methods become slow and fragile.
More about SPH simulation
Smoothed particle hydrodynamics (SPH) represents the liquid as a large number of particles, each carrying its own mass, velocity and pressure and interacting with its neighbours. There is no fluid mesh to distort, so the free surface can split and rejoin freely, and moving parts such as gears, shafts and impellers pass through the domain without remeshing. The study shows where the liquid goes, which surfaces stay wetted, and the forces and torque the liquid applies.
SixGate™’s engineers turn the results into design changes: a baffle in the sump, an oil guide or catch tray, a different fill level, or a breather or air intake moved clear of the splash zone.
Typical uses: automotive and electric drive gearboxes, industrial gear units, axles, stirred tanks, fuel and coolant tanks, and liquid handling equipment.
What an SPH study tells you
Does oil reach every gear and bearing?
Wetting of gear meshes, bearings and seals at each speed and fill level, showing which components run short of oil.
How much power is lost to churning?
Drag torque from oil on the rotating gears and shafts, so fill level and sump shape can be traded against lubrication.
How does a stirred tank mix?
How liquid moves around the impeller and baffles at your fill level and speed, showing where it circulates and where it stalls.
What loads does splashing liquid apply?
Impact pressures and forces on tank walls, baffles, covers and nearby structures, ready for a structural assessment.
Will the liquid stay where it should?
Leakage paths, overflow and spill from breathers, vents and open containers under motion or tilt.
What we model
Gearbox and transmission lubrication
Splash-lubricated gear trains with rotating gears and shafts, showing oil distribution, wetting and churning torque.
Green water and slamming
Water breaking over decks, hatches and equipment, and the slamming pressures it brings.
Violent sloshing
Tanks under sudden acceleration or impact, where the surface breaks up and slams against walls and baffles.
Splashing and fling-off
Liquid thrown from rotating or moving parts such as shafts, chains and couplings, and the surfaces it reaches.
Moving and rotating geometry
Gears, shafts, wheels and paddles moved through the liquid at prescribed speeds or along prescribed paths, with no remeshing.
Wetting and exposure
Which surfaces see liquid over time, used to judge lubrication of components or the exposure of parts that must stay dry.
Before you start
What to send us
- CAD of the gearbox, tank or vessel and its moving parts (STEP or native)
- Speeds, motion paths or the manoeuvre to be simulated
- The liquid and its properties at operating temperature
- Fill level or water depth
- The components that must be wetted, or kept dry
- Known problems, such as noisy gears, hot bearings or water ingress
When is SPH better than conventional CFD?
When the free surface breaks up violently or the geometry moves in complex ways, such as meshing gears. For calmer free surfaces, or flows where boundary layers and heat transfer dominate, mesh-based CFD is usually the better tool.
Can you predict churning losses?
Yes, as drag torque on the rotating parts at each speed and fill level. The figures are most useful for comparing designs against each other, such as two fill levels or baffle positions.
Does an SPH study include the air?
Most SPH studies model the liquid only, with the air treated as empty space. That suits splashing and sloshing, where the air has little effect on where the liquid goes.
Can you model an electric drive unit as well as a conventional gearbox?
Yes. Electric drive units raise the same questions of oil distribution and churning, often at higher input speeds, and the oil may also be cooling the motor.
Send us your gearbox or tank
