DescriptionOpen-channel flow over rough riverbeds is a core application of multi-phase flow modeling in Fluent, where the water-air interface must be resolved alongside the effects of bed roughness on velocity and flow behavior. This CFD study uses ANSYS Fluent to simulate open-channel two-phase flow in natural river systems, examining how bed roughness influences flow characteristics relevant to water resource management and flood control.MethodologyThe channel geometry is built with a rough bed representation, and appropriate meshing strategies are applied to resolve flow near the bed surface. Two-phase flow properties are configured to define the water and air phases within the domain, with free surface modeling used to capture the dynamic interface between the two. Bed roughness is incorporated through surface roughness parameters and geometric representations, configured to capture its influence on velocity profiles and overall flow behavior. Boundary conditions are set at the inlet and outlet to represent realistic river flow scenarios, with appropriate conditions defined for the free surface, channel walls, and bed. Solver parameters, including time-stepping and convergence criteria, are configured for the open-channel flow simulation, with progress monitored throughout the solving process to ensure stability.Results AnalysisPost-processing generates visualizations of velocity fields and streamlines to characterize water flow patterns within the rough channel, along with velocity profiles and water surface behavior relevant to assessing river flow characteristics. Free surface behavior is examined to capture the water-air interface dynamics throughout the channel. These results provide insight into how bed roughness and channel geometry shape open-channel flow, supporting applications in river training works, flood prediction, and erosion control strategies within civil and hydraulic engineering practice.

Pollution Spread in a Stagnant River, ANSYS Fluent TrainingDescriptionThis project simulates the entry and spread of a pollutant into a stagnant river using ANSYS Fluent.The core of this case is open-channel flow — flow in a channel or river whose upper surface is open to the atmosphere and free to deform, rather than being fully enclosed by walls. In open-channel problems the position and shape of the free surface is part of the solution, and gravity governs how the water and anything riding on it settle and move. A river receiving a discharge is a natural example: the pollutant enters at the surface and spreads across it, so tracking that free surface is essential, which is exactly what the open-channel (free-surface VOF) approach is built for.The application itself is an environmental one. Water pollution from industrial waste is a serious concern: chemical by-products discharged into rivers endanger aquatic life and can enter the human food chain through it, causing disease. Simulating how a pollutant disperses once it reaches a river helps predict how far and how fast contamination travels.The 3-D geometry was built in Design Modeler, with a river inlet width of 11.05 m. The domain was meshed in ANSYS Meshing with 161,562 elements, and because the spreading process evolves in time, a transient solver is used.Simulation MethodologyThe two phases — water and pollutant — are handled with the VOF multiphase model. The pollutant enters through a non-uniform profile partway along the river and diffuses into the water. Because its density is lower than that of water, it floats and spreads along the free surface. Turbulence is solved with the realizable k-ε model using scalable wall functions, pressure-velocity coupling is SIMPLE, and momentum and the volume fraction use second-order upwind discretization. The river water itself is initially stagnant, and the pollutant enters at 8 m/s.Results & ConclusionAfter solving, contours of velocity, pressure, and pollutant volume fraction were obtained. The results show the pollutant progressively diffusing into the river water over time, with the pressure near the pollutant inlet higher than elsewhere. The cross-sectional pressure contour also shows pressure increasing with depth, as expected for a body of water under gravity.

DescriptionThis project simulates pollution transport in a meandering river using ANSYS Fluent, investigated through CFD analysis. Water pollution is the contamination of water bodies — usually the result of human activity — in a way that harms their legitimate uses. Such pollution prevents a body of water from delivering the ecosystem services it would otherwise provide, and it is broadly classified as either surface water pollution or groundwater pollution.The model was built in 3D using Design Modeler. The river's width at the inlet is 14.035 m, and the pollutant enters through two circular profiles, each 3 m in diameter. Meshing was performed in ANSYS Meshing, producing 762,433 elements. Because of the time-dependent nature of the problem, a transient solver was used.MethodologyThis study employs the VOF (Volume of Fluid) multiphase model to solve the two-phase flow field. To represent the free surface of the river, the open channel option within the multiphase module was enabled, allowing the air–water interface and the gravity-driven surface flow to be captured accurately.Pollutant enters the river through two circular inlet profiles near its start and then diffuses into the water. Because the pollutant is less dense than water, it accumulates at the river's surface, and the flow carries it downstream, spreading the contamination along the channel.The Realizable k-epsilon viscous model with scalable wall functions was used to resolve the turbulent flow. Pressure-velocity coupling was handled with the SIMPLE scheme. A second-order upwind scheme was applied to the momentum equations, while a first-order upwind scheme was used for the turbulent kinetic energy and turbulent dissipation rate. Water enters the domain at 35 m/s, and the pollutant enters at 5 m/s.ConclusionOnce the solution was complete, contours of velocity, pressure, pollutant volume fraction, water volume fraction, eddy viscosity, and streamlines were extracted and presented across different time steps.As the results show, the pollutant enters the river through the two circular inlet profiles and gradually diffuses across the water surface over time. Driven by the river's flow, the pollution spreads along the free surface and ultimately leads to widespread contamination of the channel.

Pond Overflow — ANSYS Fluent CFD SimulationDescriptionWhen water spills over an ogee overflow and discharges into a pond, the way it behaves depends heavily on whether the flow runs as a free surface or under pressure. Capturing that difference is essential for designing spillways and overflow structures that handle their intended flow safely. In this project, you'll use ANSYS Fluent to simulate water flowing over an ogee overflow into a pond, comparing two distinct flow regimes side by side. Within the Hydraulic & Civil: Beginner CFD Training Package, this project moves from open channels toward hydraulic structures, introducing overflow behavior and the important distinction between free-surface and pressurized flow.MethodologyThe model is built in two dimensions in ANSYS DesignModeler as an ogee overflow leading into a pond, and two separate cases are studied. In the first, the flow is a free surface reaching the overflow at a defined height with a flow rate of 140 kg/s; in the second, the water flows under pressure with a flow rate of 420 kg/s. The geometry is configured in two variants — one that includes an upstream region before the overflow and one that omits it — and the inlet is split into separate water-flow and airflow sections. Meshing is carried out in ANSYS Meshing using a semi-structured grid, with roughly 20,100 elements for the free-flow case and 16,400 for the pressure-flow case. Because both cases involve a moving interface between air and water, a two-phase Volume of Fluid (VOF) model is used, with air defined as the primary phase and water as the secondary phase.AnalysisFrom the results, you'll examine 2D contours of pressure and velocity along with the volume-fraction field that reveals the free surface and the path of the water into the pond. You'll also obtain a plot of static pressure along the flow direction for both models, allowing a direct comparison between the free-surface and pressurized regimes. By the end of this project, you'll be able to set up a two-phase free-surface flow in ANSYS Fluent using the VOF model, configure and compare multiple flow scenarios on a single hydraulic structure, and interpret the results to understand how overflow conditions change the pressure and velocity behavior.

Stepped Spillway (Stair Spillway) — ANSYS Fluent CFD SimulationDescriptionWelcome to the Stepped Spillway (Stair Spillway) CFD Simulation module. This project introduces civil and hydraulic engineers to stepped spillways and their analysis using ANSYS Fluent. A stepped spillway replaces the smooth face of a conventional spillway with a series of steps, and this stepped profile dramatically increases energy dissipation, reduces the risk of cavitation, and improves water aeration — advantages that have made it a favored choice in modern dam design. As the capstone of the Hydraulic & Civil: Beginner CFD Training Package, it brings together the two threads developed across the package — hydraulic structures and complex multiphase flow — combining a stepped structure with the strong aeration and energy dissipation that make it the most demanding case in the set.MethodologyThe workflow begins with creating a basic geometry representing a stepped spillway and applying an appropriate meshing strategy for accurate flow analysis. The water properties are defined in ANSYS Fluent, and the boundary conditions are set to represent the stepped spillway scenario — inlet flow rates and outlet pressure conditions, together with wall and free-surface boundary conditions for the stepped surface and the water–air interface. The solver parameters, including time-stepping and convergence criteria, are configured to suit a stepped spillway hydraulic simulation, and the solution is monitored for stability and convergence throughout. The setup is designed to capture the flow tumbling down the steps and the strong air–water interaction that drives the aeration and energy dissipation characteristic of these structures.AnalysisPost-processing focuses on the flow patterns and energy dissipation along the steps. Velocity fields and streamlines are visualized to understand how the water moves over the stepped profile, while the energy-dissipation characteristics are analyzed to assess how efficiently the structure reduces the flow energy from step to step. Air-entrainment patterns are identified to reveal how the stepped spillway promotes aeration as the water descends. By the end of this project, you'll be able to set up and run a basic stepped spillway simulation in ANSYS Fluent, capture stepped-flow patterns and energy dissipation, interpret the aeration behavior, and apply those insights to stepped spillway design and performance evaluation for modern dam engineering and flood control.

DescriptionA spillway is a hydraulic structure designed to regulate the water level stored behind a dam or levee, typically discharging excess flow into a downstream riverbed. Several spillway configurations exist, each suited to different site and capacity requirements.As incoming water raises the reservoir level beyond the dam's storage capacity, the surplus volume must be safely released downstream through the spillway. This project simulates a labyrinth spillway positioned at the center of a channel, designed to manage and control the stored water height behind it.The 3D geometry was built in Design Modeler, and an unstructured mesh was generated in ANSYS Meshing, producing 464,175 elements. Using ANSYS Fluent's Make Polyhedral function, this element count was later reduced to 99,248, improving computational efficiency without sacrificing accuracy.MethodologyThe simulation is run as a transient (unsteady) case to properly capture the time-dependent behavior of the fluid. A pressure-based solver is used, appropriate for the incompressible working fluid. Gravitational effects are included by applying an acceleration of 9.81 m/s² in the negative Y-direction. Multiphase behavior is captured using the VOF (Volume of Fluid) model to track the interacting fluid phases throughout the simulation.ConclusionThe water level retained behind the spillway stabilizes at a height equal to the spillway's own height, while any inflow exceeding the dam's storage capacity is directed over it. This excess water passes through the labyrinth spillway and continues downstream, helping maintain a controlled reservoir level.The contours and animations reveal turbulent behavior as incoming water pushes the stored fluid toward the downstream side. Once the flow overtops the dam structure, it accelerates noticeably before reaching the outlet.

Water Wheel (Pelton Wheel), ANSYS Fluent CFD Simulation TrainingDescriptionThis project simulates the performance of a water wheel — a classic example of a Pelton turbine — using ANSYS Fluent.Most water wheels are mounted vertically on a horizontal axis, though horizontal mounting on a vertical shaft is also possible. The fluid flow equations are solved using the averaged form of the Navier-Stokes equations within ANSYS Fluent.The turbine has a diameter of 0.7 m, with the free surface boundary positioned 0.2 m below the wheel's center. Water velocity ranges between 3 and 5 m/s, depending on average river conditions, from which the turbine's rotational speed is determined to avoid drag or disruption in the flow — in this simulation, the turbine rotates at 60 rpm.MethodologyThe wheel's blades are positioned perpendicular to specific turbine sections to reduce friction and increase nozzle thrust, while a portion of the turbine remains outside the water. As a result, the wheel operates across two distinct phases — water and air — as it rotates about its axis, modeled using the VOF (Volume of Fluid) multiphase model.The turbine geometry was designed in SOLIDWORKS and divided into smaller sections to improve both geometric detail and mesh quality. The model was split into two rotating (Rotor) regions and one stationary (Stator) region: the rotor comprises the turbine itself along with a surrounding cylinder, while the static region encloses this rotating cylinder.Meshing was performed in ICEM CFD. The rotor section was meshed using an unstructured grid, with finer mesh density applied at the turbine's leading edge to capture the complex flow behavior and high gradients present in that region. The stationary zone used a structured mesh, which reduces overall element count while maintaining high mesh quality. The two separately meshed regions were then coupled together to form the complete domain.Impeller rotation was applied incrementally, with 3 degrees of rotation per time step — a value that should be reduced further for higher simulation accuracy. This motion was handled using the Mesh Motion approach, with the static and rotating mesh regions sliding relative to one another across a shared interface boundary.ConclusionThe results clearly capture the wheel's continuous rotational motion as it interacts with the incoming water stream, with velocity and pressure contours highlighting how the flow strikes each bucket in sequence to sustain the wheel's rotation. The VOF-based volume fraction contours trace the air-water interface as it deforms around the submerged buckets, showing the free surface dipping and recovering as each bucket enters and exits the water.Pathlines around the turbine illustrate how incoming flow is redirected by the curved bucket geometry, transferring momentum to the wheel and producing the torque that drives its rotation. Together, these results confirm that the coupled rotor-stator mesh motion setup successfully reproduces the expected physical behavior of a Pelton-type water wheel operating at the free surface, providing a validated basis for evaluating design changes such as bucket geometry, submersion depth, or rotational speed in further studies.

Water Discharge of a Rotating Tank, ANSYS Fluent CFD Simulation TrainingDescriptionThis project simulates the water discharge of a rotating tank using ANSYS Fluent, applying the Volume of Fluid (VOF) model to solve the two-phase flow field, with air as the primary phase and water as the secondary phase. The tank rotates about the Y-axis at 80 rev/min, with water discharging through two circular orifices located at the bottom of the tank.The geometry was generated in Design Modeler, modeling the tank as a cylinder with a diameter of 1 m and a height of 0.75 m, with each orifice measuring 150 mm in diameter. The domain was meshed in ANSYS Meshing using an unstructured grid throughout, totaling 470,369 elements.MethodologySeveral assumptions were applied to the simulation: given the incompressible nature of the flow, a pressure-based solver was selected, the simulation was run as transient, and gravitational effects were included at -9.81 m/s² along the Y-axis. The tank wall was assigned a rotational speed of 80 rpm about the Y-axis.Key simulation settings included:Multiphase model: VOF with two Eulerian phases (air and water), sharp interface modeling, and explicit formulationViscous model: Standard k-epsilon with scalable wall functionsMaterial properties: Air (density 1.225 kg/m³, viscosity 1.7894×10⁻⁵ Pa·s); water (density 998.2 kg/m³, viscosity 0.001003 Pa·s)Boundary conditions: Pressure outlet at both the main outlet and orifice; tank wall defined as a moving wall rotating at 80 rev/min about the Y-axis (origin at 0,0,0)Solution methods: SIMPLE pressure-velocity coupling, PRESTO! for pressure discretization, second-order upwind for momentum, first-order upwind for turbulent kinetic energy and dissipation rate, and a compressive scheme for volume fractionAdaption controls: A cylindrical registration region (0.5 m radius, extending along Y from 0 to 0.6 m) used to define the initial water patchInitialization: Standard method, with the water phase patched into the defined cylindrical region at a volume fraction of 1Run settings: Time step size of 0.02 s, maximum 20 iterations per time step, over 700 total time stepsConclusionResults include contours of pressure, water volume fraction, eddy viscosity, and streamlines. The results clearly show that, under the combined influence of gravity and the tank's rotational motion, the water within the cylindrical tank rotates about the Y-axis as it discharges through the orifices — with the volume fraction contours tracing how the water body deforms and thins near the orifice openings as it exits. The streamline patterns further illustrate the swirling discharge behavior induced by the tank's rotation, showing how angular momentum imparted by the moving wall carries through into the exiting flow. Together, these results confirm that the rotating reference imposed on the tank wall successfully couples with the VOF-tracked free surface to reproduce the expected swirl-driven discharge pattern through both orifices.

Sloshing Water in a Cube with Transitional Motion, ANSYS Fluent TrainingDescriptionThis project investigates the transitional motion of a cube containing water and air using ANSYS Fluent, examining how fluid sloshing develops as the container itself accelerates.The fluid domain geometry was designed in Design Modeler, with the computational grid generated in ANSYS Meshing using an unstructured mesh totaling 168,367 elements.MethodologyThe interaction between water and air within the cube is modeled using the Volume of Fluid (VOF) multiphase approach, chosen for its efficiency and precision in capturing the interface location between phases — making it one of the most widely used methods for multiphase flow investigation due to its favorable computational cost.The cube accelerates along the X-direction at 5 m/s², while gravitational acceleration acts along the -Y direction on the multiphase fluid. The simulation was run using an unsteady (transient) time solver.ConclusionThis project models a simplified sloshing scenario relevant to fluid containers subjected to acceleration, such as those found in moving carrier vehicles — where similar sloshing behavior commonly occurs.The results show that pressure on the cube's bottom surface varies systematically with position, increasing progressively further from the cube's front face. This trend reflects the fluid's inertial response to the applied acceleration: as the cube accelerates forward, water is driven toward the rear of the container, building up higher local pressure there. Gauge pressure at the bottom surface starts at 1290 Pa near the front and rises to a peak of 6500 Pa at the back face of the cube — a roughly five-fold increase that clearly demonstrates how translational acceleration reshapes the pressure distribution within a partially filled, sloshing container.

Jet Ski (Two-Phase Flow Study) — ANSYS Fluent CFD SimulationDescriptionThis project simulates the motion of a jet ski at the interface between water and air, capturing how a floating body disturbs the free surface as it moves. Flow around floating objects — boats, ships, jet skis — is one of the most common two-fluid phenomena around us, and wherever two fluids meet, the interaction and deformation of the interface becomes the central engineering question. Here the goal is to see how the jet ski rides the surface and reshapes the water behind it. Within the Open Channel Flow: Beginner CFD Training Package, this project applies free-surface modeling to a moving craft, building on the sea-wave case toward the flow around a real floating body.MethodologyThe physics is handled with the Volume of Fluid (VOF) multiphase model, which tracks the sharp water–air interface as it deforms around the moving body — the standard tool for free-surface and open-channel problems where the shape of the surface is itself a key result. The computational domain has an inlet where water enters at a mass flow rate of 50,000 kg/s and a pressure outlet, with the jet ski floating at the interface. The geometry is built in ANSYS Design Modeler and meshed in ANSYS Meshing as an unstructured mesh of roughly 1,748,941 elements — unstructured here to wrap cleanly around the curved hull geometry.AnalysisPost-processing provides contours of pressure and velocity, velocity vectors, and the water volume fraction. The volume-fraction field captures the free surface clearly and shows how the phases interact around the floating body — the jet ski is pushed by the flow, and a distinct wake sequence forms behind it, with water lifted above the undisturbed surface level. That surface jump is exactly the behavior you'd expect from a jet ski's interaction with the water, recovered directly from the simulation. By the end of this project, you'll be able to set up a VOF water–air free-surface case around a floating body, define mass-flow inflow and pressure-outlet conditions, and read free-surface deformation and wake structure from the volume-fraction and velocity fields.