Fluid Dynamics Analyses (CFD)
For small watercraft, agricultural sprayer tanks and rotationally moulded vessels, we analyse free-surface motion, hydrodynamic behaviour and flow-induced loads using numerical fluid dynamics (CFD). We then combine the resulting pressure and force maps with mechanical and hydrostatic analyses to design shells and support structures against realistic load scenarios.
Hydrodynamic Performance and Stability of Small Watercraft
Canoes, kayaks, small inshore fishing boats and light sailing/day boats are governed by similar hydrodynamic limitations. Draft, bow shape, keel line, beam and volume distribution determine both drag and primary/secondary stability. With numerical fluid dynamics (CFD) analyses we visualise wave patterns on the free surface, flow lines around the hull and the pressure distribution, so hull-form decisions are tied to quantified data instead of intuition alone.
In this project the customer asked for a single-seater canoe that is tolerant to different levels of user error and difficult to capsize. Speed was not the main priority; the focus was on a hull that does not easily ship water, offers forgiving roll behaviour and feels trustworthy for a wide user base. Using CFD, we varied hull form, volume distribution and freeboard height, then compared the resulting flow field, buoyancy and stability characteristics.
Key questions we address with CFD
- Free surface and wave pattern: how prone the canoe is to rolling under different wave and loading conditions, and which combinations trigger sudden instability.
- Pressure and buoyancy distribution: how the centre of buoyancy shifts along the hull as user weight and seating position change.
- Drag: whether we maintain the safety-oriented hull form without causing unnecessary energy loss over the target speed range.
- Trim and stability: pitch and roll behaviour, capsize threshold and the recovery window.
How this feeds into design decisions
- Defining a beam, freeboard and volume-distribution window where users are kept out of the water but can still paddle comfortably.
- Quantifying an acceptable stability band for different user weights (for example child vs adult).
- Helping rental operations choose hull forms that are more forgiving against user mistakes.
- If an existing model is available, preparing a comparative table between the current and proposed hulls in terms of capsize angle, comfort and load distribution.
As a result, target hydrodynamic performance for the intended use can be expressed numerically in terms of speed, stability and safety, and hull design is steered to meet these criteria.
Sloshing and Dynamic Loads in Agricultural Tanks
In sprayer tanks mounted on tractors or trailers, at 30–70% filling levels, braking, acceleration and uneven ground cause the liquid to surge back and forth. The resulting wave motion, local pressure peaks and horizontal forces act on both the tank shell and the chassis. With sloshing analyses we track free-surface motion, pressure fields and time-dependent horizontal forces, then derive a safe load envelope to be used in design.
In this project we examined how a 2000 L polyethylene sprayer tank mounted on a tractor behaves under sudden braking at 50% filling. The sloshing analysis captured free-surface motion, peak wave pressures and the horizontal forces transmitted to tank-to-chassis connections as a function of time. From these results we derived equivalent static loads to be used in mechanical design.
Main aspects in our sloshing studies
- Free-surface motion: wave height at different filling levels and impact behaviour on front/rear walls.
- Pressure field: local pressure peaks during braking and load concentrations where the wave crest hits.
- Global forces and moments: time-dependent horizontal forces and overturning moments transmitted from tank to chassis.
- Effect of filling level: how the load envelope changes for 30%, 50% and 70% filling and which range is most critical.
How this feeds into design decisions
- Defining equivalent static loads for tank feet and connection brackets based on real sloshing behaviour.
- Pinpointing regions of the chassis that need reinforcement (for example under tank supports and side beams).
- Evaluating whether internal baffles or flow-guiding elements are required and, if so, assessing their placement numerically.
- Building a load envelope for different braking profiles (normal vs emergency) and speed ranges, then setting design safety factors accordingly.
This way, the question “what really happens during braking?” for agricultural tanks is answered not by guesswork but by pressure and force values mapped against filling level, speed and braking profile — giving an engineering-grade load scenario.
Other CFD Projects (Case-Based)
Beyond watercraft and agricultural tanks, we also run project-specific CFD studies for more specialised flow problems related to rotational moulding. Here the goal is not a generic product family but to numerically reveal a particular use case and clarify the design decisions around it.
Examples directly related to rotational products
- Mixing time, dead volume and homogeneity analysis in tanks equipped with mixers.
- Investigation of air pockets and venting behaviour during filling/emptying of rotational tanks.
- Pressure loss and uneven flow distribution assessment in collectors and piping manifolds.
- Dedicated studies for auxiliary equipment such as fans and ducted flow that interact with rotational products.
Our project-based approach
- For each project we first clarify the scenario, target outputs and acceptance criteria.
- Where needed we link CFD results with mechanical or hydrostatic analyses to capture load transfer.
- Results are delivered as colour maps, numerical tables and a concise report with design recommendations.
- For recurring work we propose analysis templates that can be standardised in the future.
Scope & Deliverables
What We Analyse
- Sloshing: time-dependent pressure and horizontal load maps.
- Mixing: time to homogeneity and dead-volume regions.
- Filling/emptying: air pockets, residual volume at the bottom, inlet effects.
- Piping/headers: pressure loss and unbalanced flow distribution.
- Where required, mapping CFD results onto mechanical/hydrostatic models to study load transfer.
Our Deliverables
- Colour maps for pressure, velocity, concentration and free-surface shape (selected time steps).
- Tables for key metrics such as ppeak, Fx,max, mixing time and dead-volume ratio.
- One-page executive summary plus key design decision highlights.
- CAD screenshots with annotated revision suggestions (baffles, openings, sump geometry etc.).
- If requested, a combined summary document where CFD-based loads are linked to mechanical/hydrostatic analysis reports.
Frequently Asked Questions
- CAD: STEP/Parasolid model including critical internal details and openings.
- Fluid properties: type, density (ρ), viscosity and operating temperature range.
- Scenario: filling level, speed/acceleration profile, mixer speed or pump flow rate and similar operating data.
- Targets (if any): for example maximum dead-volume percentage, acceptable mixing time or pressure limits.