Flow-3d Hydro

[Alysa Guillama]

Theaccuracy and robustness of the sharp-interface tracking VOF methods in FLOW-3D have been enhanced by combing them with fluid particles. The new particle species, called VOF particles, are used in place of the VOF function to track small fluid ligaments and droplets in the computational domain, achieving better conservation of fluid volume and momentum.

This example represents a sludge decanter that models a mixture of water and sludge entering a decanter and separating. Water is allowed to flow in and out at the back side of the decanter to maintain a relatively fixed level in the decanter. A sampling volume in the bottom of the decanter is used to measure the amount of sludge captured at the bottom. When the sludge mass in the sampling volume reaches 200 kg, a valve opens to release the sludge. The valve closes when the sludge mass drops below 180 kg.

In this simulation, oxygen bubbles are injected from two diffusers at the bottom of the container and allowed to rise in water. As the bubbles rise, oxygen dissolves into water. The image on the left shows the concentration of dissolved oxygen in water. The image on the right shows the water velocity which is induced by the rising oxygen bubbles.

Viscosity is defined as a function of both solid content (density) and strain rate. In this example a dense fluid region slides down into a quiescent pool which at time zero is layered with a dense settled fluid region and clear water above.

In this simulation of air entrainment at a free surface due to a vertical impinging jet, inclusions of air at the free surface jet contact are entrained into the bulk of the body of water after which they will rise or may also be entrained along with ambient flow. FLOW-3D HYDRO offers different methods to model this process. This particular model uses a 2 phase VOF with LES turbulence, although 1 phase VOF with the air entrainment model in FLOW-3D HYDRO is more commonly used.

Disinfection of water is an important part of wastewater/water treatment processes. One method of disinfection uses chlorine added to the water in a Contact Tank. This simulation models the interactions between chlorine and a pathogen in a contact tank. The simulation first models the hydrodynamics of the contact tank. Then the disinfection process is modelled using a scalar model to represent the chlorine and pathogen and is coupled with a reaction kinetics model to model the consumption of the chlorine and the decay of the pathogen due to disinfection.

This FLOW-3D HYDRO CFD simulation uses the Hybrid 3d/Shallow Water model to better understand and more efficiently model bridge hydraulics. The simulation fully couples the 3D model with a 2D shallow water model together in one run. The surrounding areas to the bridge were modelled in full 3D, while the upstream and downstream areas of the river were modelled using a 2D shallow water model.

Development of a hydraulic jump simulated with FLOW-3D HYDRO. The top view is a ray-traced rendering of the flow; the bottom view, a 2D slice of the velocity field. This simulation was postprocessed with FLOW-3D POST, our new postprocessor for visualization and analysis across FLOW-3D products.

Baffle drop shafts transport storm water to underground tunnels for storage and transport. FLOW-3D HYDRO can be used to compare drop shaft design elements such as shaft diameter and baffle spacing, which affect the flow velocity, amount of entrained air entrained, and other flow features.

Under certain flow conditions tangential dropshaft are effective by promoting the formation of a vortex core in the dropshaft as the flow is propagated to lower elevations. FLOW-3D HYDRO offers multiple modeling approaches to help engineers model free surface flow characteristics, and evaluate the energy dissipation, downdraft and air entrainment behaviors of the system.

Culvert capacity and bridge overtopping: as the upstream flow rate increases, the culvert may become pressurized, resulting in a complex hydraulic control made up of a culvert coupled with an overtopping weir flow.

FLOW-3D HYDRO example of flow in a baffle drop structure: advanced free surface modeling capabilities deliver an extraordinarily accurate representation of the flow, even in very complex conditions like those found in a drop structure. Courtesy NEORSD, Wade Trim, and IIHR.

This simulation shows the turbulent intensity and volume of entrained air caused by a vertical jet plunging into a moving cross stream. The air entrainment and transport process actually involves three separate models that work together: the air entrainment model, variable density model, and drift flux models are used to approximate the air entrained at the free surface as well as the motion of the entrained air within the fluid.

This simulation shows the water treatment process in a chlorine contact tank. Probes are used to measure the concentration of bacteria, oxygen, chlorine, and a biodegradable substrate at three points along the flow of water through the tank. FLOW-3D simulation can be used to test the design of a contact tank to ensure enough residence time for proper disinfection and avoid regions where water is allowed to remain in the tank for too long.

This simulation shows sedimentation in a circular clarifier. 2D clips are used to show the profiles of sludge settling at the bottom of the tank. The separation and removal of solids from wastewater through settling tanks like this one is often part of the activated sludge process, following aeration.

FLOW-3D HYDRO is the ideal tool for the design and analysis of fish passage structures. Highly accurate 3D simulations of complex free surface conditions provide advanced investigations of upstream passage success through the evaluation of flow velocities, depths, drop heights and turbulence characteristics along potential movement pathways. In this simulation, the flow velocities and pattern are analyzed in a culvert with spoiler baffles.

Spillway plunge pools can cause significant sediment scour, which can lead to dangerous conditions at the foot of the dam and undermine the stability of the adjacent slopes. CFD simulations such as the one shown in this video can be used to analyze velocity, air entrainment, tailwater elevation and other spillway characteristics to mitigate sediment scour and other issues in dam safety.

Energy dissipating structures such as the baffles shown in this simulation can be used in some culverts and open channels to limit acceleration of the flow through the channel and help minimize downstream erosion.

Marine outfalls discharge untreated or primary treated flows into a submarine environment. Depending on its makeup, discharge can be either positive, negative or neutrally buoyant, which can affect its dispersion rate. This simulation shows the dispersion of a positively buoyant discharge plume as it exits the outfall.

FLOW-3D HYDRO can be used in the design analysis of submerged and emerged rubble-mound breakwaters to evaluate wave run-up, reflection, and hydrodynamic forces under different structural and environmental conditions.

In this simulation of a diversion tank, the moving objects model is used to simulate the opening of a sluice gate, which helps regulate the flow of storm water in a combined sewer overflow (CSO) system.

FLOW-3D is an industry leader in free-surface flow modeling and is used by dam professionals to address a wide range of design problems for existing and proposed projects. Dam safety professionals and design engineers around the world rely on the efficiency and accuracy of FLOW-3D to easily generate discharge rating curves for complex spillways and control structures. With our advanced free surface modeling capabilities, FLOW-3D HYDRO can be used to simulate flow over a variety of weir shapes and gate-controlled structures.

FLOW-3D HYDRO is an industry leader in free-surface flow modeling and is used by dam professionals to address a wide range of design problems for existing and proposed projects. Dam safety professionals and design engineers around the world rely on the efficiency and accuracy of FLOW-3D HYDRO to easily generate discharge rating curves for complex spillway and control structures. With our advanced free surface modeling capabilities, FLOW-3D HYDRO can be used to simulate flow through complex geometries such as the non-linear weir shown in this example.

This FLOW-3D HYDRO simulation shows sediment scour formation and a dune formation for a 2D case. The FLOW-3D HYDRO results are validated against the Chatterjee experiments.

In this FLOW-3D HYDRO simulation of a flow over a sharp-crested weir, our state-of-the-art postprocessor was used to illustrate the flow velocity and pressure at the free surface and the flow velocity in a 2D slice (top right). The addition of a flux surface to the model allows the user to report the volume flow rate over time.

All FLOW-3D products are powered by the same multiphysics solver engine, while customized user interfaces allow for easy, intuitive and error-free modeling workflows. Whether on in-house HPC clusters or our cloud computing solutions, FLOW-3D products scale seamlessly to thousands of CPU cores.

This is a simulation of an automotive flywheel or bell housing, showing velocity contours of aluminum alloy during fast shot of a high pressure die casting process. This is part of a design phase to evaluate different gating options, the 5 gates here simulate filling from a runner upward and below the parting line to accomplish 80-millisecond casting fill. The animation helps visualize the highly turbulent fill clearly indicating first and last regions to fill. Among other things, it helps in understanding the moving metal front and potential cold shots that result from this gating configuration.

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