Open-Channel Two-Phase Flow in Rough Rivers — ANSYS Fluent CFD SimulationDescriptionWelcome to the Open-Channel Two-Phase Flow in Rough Rivers CFD Simulation module. This project introduces civil and hydraulic engineers to the world of river hydraulics using ANSYS Fluent. Open-channel flow — water moving with a free surface under gravity — governs how rivers behave, shaping flood patterns, erosion processes, and overall water-resource dynamics. What sets a natural river apart from an idealized channel is the roughness of its bed, which strongly influences the velocity profile and the water surface. This module shows how to represent that roughness realistically and capture its effect on the flow. Within the Hydraulic & Civil: Beginner CFD Training Package, it builds on the waterfall case by moving from free-fall flow into fundamental open-channel hydraulics, applying the two-phase VOF method to a natural watercourse.MethodologyThe workflow begins with creating a basic geometry representing an open channel with a rough bed and applying an appropriate meshing strategy for accurate flow analysis. The two-phase flow is set up by defining the properties of water and air within ANSYS Fluent. A central part of the setup is representing the rough river bed: bed roughness is modeled through surface-roughness parameters or geometric representation, and the model settings are configured so that the roughness properly influences the water flow patterns and velocity profiles. The boundary conditions specify inlet flow rates and outlet conditions to represent the river scenario, along with free-surface and wall boundary conditions for the water surface, the channel walls, and the bed. The solver parameters — including time-stepping and convergence criteria — are configured to suit an open-channel hydraulic simulation, and the solution is monitored for stability throughout.AnalysisPost-processing focuses on extracting meaningful insight from the river flow. Velocity fields and streamlines are visualized to understand the flow behavior over the rough bed, while velocity profiles and water-surface behavior are examined to assess the river's hydraulic characteristics and potential flood scenarios. Free-surface visualization reveals the dynamic water–air interface along the channel. By the end of this project, you'll be able to set up and run a basic open-channel flow simulation with a rough bed in ANSYS Fluent, capture flow patterns and velocity profiles in a natural channel, interpret the free surface and velocity results, and apply those insights to river management, flood control, and erosion-control strategies.

Ogee Spillway CFD Simulation, ANSYS Fluent TrainingDescriptionThe primary function of a spillway is to safely discharge excess water during high-flow events such as floods, protecting the dam body from damage caused by overtopping or excessive pressure. Spillways typically consist of a vertical plate oriented in the direction of flow, with an upper edge that may be sharp-crested, curved, or wide, depending on the design. Common spillway types include open channel, chute, stepped, siphon, ogee, side channel, and labyrinth configurations.This project simulates an ogee spillway using ANSYS Fluent, investigating the behavior of water flow after passing over the spillway crest in the presence of surrounding airflow.The geometry was designed in Design Modeler, modeled as a horizontal cylinder with a horizontal inlet for the mixture flow and two vertical outlets for the separated gas and liquid streams. The domain was meshed in ANSYS Meshing using an unstructured mesh totaling 10,959 cells.MethodologySince the channel involves two distinct fluid phases, a two-phase flow model was applied using the VOF (Volume of Fluid) approach, with water defined as the primary phase and air as the secondary phase. Because the boundary between the two phases is sharply defined, the sharp interface modeling option was used to accurately capture the behavior at the water-air boundary.ConclusionPost-processed results include contours of velocity, pressure, and the mass fraction of water and air. The results show water striking the dam body and beginning to overflow at the spillway's upper edge. The excess flow then slides down the spillway's curved slope at reduced pressure, helping to dissipate the incoming flow's energy and preventing floodwaters from intensifying further downstream.

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.

Spillway (2-D & Transient) CFD Simulation, Two-Phase Flow, ANSYS Fluent TrainingDescriptionThis project simulates the two-phase flow of water and air over an ogee spillway — the curved overflow structure used in dams to pass excess water safely downstream. When flow meets an obstruction, the water level rises behind it and accelerates over the crest; the ogee profile is specifically shaped to match the natural nappe of falling water, minimizing pressure problems and maximizing discharge efficiency. Capturing the free water surface as it spills over the crest is the core focus of this simulation — a classic application of free-surface CFD in civil and hydraulic engineering.The geometry was built in Design Modeler and meshed in ANSYS Meshing using a structured mesh totaling 12,846 elements. A structured mesh was chosen here because the spillway's smooth, well-defined geometry suits a clean, flow-aligned grid.MethodologyThe physics is handled using the Volume of Fluid (VOF) multiphase model, tracking the sharp air-water interface as it deforms over the spillway crest, with the standard k-ε model closing the turbulence equations. Since the primary objective is to observe the water accelerating and forming its surface profile as it moves over the crest, the simulation was solved as transient.Water enters the computational domain at a mass flow rate of 0.05 kg/s and flows over the spillway against the surrounding air phase.ConclusionResults include contours of pressure, velocity, and phase volume fraction extracted across the domain, revealing the water surface profile as it passes over the crest, the flow's acceleration down the spillway face, and the pressure distribution along the structure — precisely the quantities a hydraulic engineer relies on to assess discharge capacity and surface pressure loading.

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.

DescriptionThis project simulates the three-phase flow of water, air, and sand over a circular weir using ANSYS Fluent, investigated through CFD analysis. When an obstacle is placed in the path of a flow, it causes the fluid level to rise behind it and the velocity to increase, eventually leading the fluid to spill over the obstacle; structures of this kind are known as weirs. Weirs take various forms depending on their intended use and are widely employed in civil and agricultural water management — for controlling and measuring flow in irrigation channels, canals, and other water-conveyance systems central to agriculture.The model was built in 2D using SpaceClaim. Meshing was performed in ANSYS Meshing, producing 4,770 elements.MethodologyIn this simulation, water enters the computational domain at a velocity of 1 m/s and flows over a sand bed situated behind the weir. As it passes over the weir, the flow lifts some of the sand and carries it downstream.The standard k-epsilon model is used to solve the turbulent flow equations, while the Eulerian multiphase model is employed to capture the motion of and interaction between the three phases — water, air, and sand.ConclusionOn completion of the solution, two-dimensional contours of the volume fraction of the air, water, and sand phases, along with pressure, streamlines, and velocity vectors, were obtained.As the sand volume fraction contour shows, the water flow lifts a portion of the sand from the bed and transports it as it spills over the weir. Over the long term, the sand bed behind the weir is washed away entirely, and the emptied region behind the circular obstacle becomes a tangential path for the water — illustrating the sediment-transport and scouring behavior that is important when designing weirs for irrigation and agricultural water systems.

Archimedes Screw Turbine (AST), CFD Simulation, ANSYS Fluent TutorialDescriptionThis project simulates an Archimedes Screw Turbine (AST) — also known as an Archimedes screw generator or screw turbine — consisting of 3 blades, using ANSYS Fluent. This hydraulic machine applies the principle of the Archimedean screw to convert the potential energy of upstream flow into kinetic energy.The turbine is modeled as installed within a river, with water flowing through it via a fixed-level inlet positioned in an upper box of the domain. The turbine is set at a 30-degree angle relative to the ground, with water entering from the upper level. The outlet is defined with zero gauge pressure, while all remaining surfaces are treated as stationary walls.The 3D geometry was designed in Design Modeler, featuring two rectangular boxes at the turbine's inlet and outlet ends that guide the flow into and out of the turbine. The turbine's interior and exterior radii measure 0.5 m and 1 m, respectively. The domain was meshed in ANSYS Meshing, generating over 2 million elements.MethodologyThe turbine's rotational motion is modeled using an unsteady Mesh Motion approach, with the rotating zone containing the screw turbine rotating independently within the domain.The VOF model defines the water and air phases, with the domain's upper level maintaining a fixed water level via the Open Channel Flow boundary condition. Turbulence is resolved using the standard two-equation k-epsilon model.ConclusionResults include 2D and 3D contours and vector fields for water pressure and velocity. Water flow enters through the upper box, passes over the turbine blades, and exits through the outlet face.Turbine output power was calculated by multiplying the moment obtained from ANSYS Fluent by the turbine's angular velocity (1.05 rad/s, corresponding to 10 rpm), yielding a maximum output of approximately 5 kW at this operating speed. The moment parameter's variation over the course of the solution is captured to illustrate this calculation.Static pressure contours across the domain further show a clear pressure decrease as the flow passes through the channel, consistent with the expected energy extraction occurring as water moves through the turbine.

Submarine Movement in Water by Dynamic Mesh (1-DOF), ANSYS FluentDescriptionThis simulation models the motion of a submarine in water using the Dynamic Mesh method in ANSYS Fluent, with a computational domain containing both air and water phases at a defined water level, with the submarine positioned within this domain.The submarine geometry was designed first, followed by a computational domain incorporating two-phase (air-water) flow around it. Both were modeled in 3D using Design Modeler. The domain includes distinct inlet and outlet sections, with symmetry conditions applied to the four surrounding faces.Meshing was carried out in ANSYS Meshing using an unstructured mesh totaling 316,846 elements.MethodologySince the submarine moves within the computational domain, affecting the surrounding grid elements, the mesh requires continuous, time-dependent updates based on the displacement occurring at adjacent mesh boundaries. This is achieved through the dynamic mesh model, applying smoothing and remeshing methods, with the submarine's wall defined as a Rigid Body.The submarine is constrained to a single degree of freedom (1-DOF), permitted to rotate only about its central axis (x-axis), with no translational or additional rotational motion. This rotational behavior is defined through a UDF, with rotational velocity varying between +1.5 rad/s and -1.5 rad/s over the 0–3 second simulation window.The rigid body settings also require specifying the spatial coordinates of the submarine's center of gravity and its axis of rotation.Since the domain contains two phases, the VOF multiphase model is applied, with air occupying the upper region and water the lower region. To represent the submarine operating in open sea conditions, wave behavior is introduced via the open channel wave boundary condition — incoming water enters at an average velocity of 10 m/s along the horizontal (x-axis), with the wave trough set at -10.16 m and its crest at 0 m. Inlet airflow enters at atmospheric pressure (zero relative pressure), with air discharged at atmospheric pressure as well.Given the dynamic mesh foundation of this model, the simulation is run as a transient (time-dependent) case, spanning 3 seconds with a time step of 0.01 seconds — necessarily unsteady due to the dynamic mesh method employed.ConclusionThe results include 2D contours of velocity and volume fraction for both water and air phases, along with 2D pathlines around the submarine — captured on a plane perpendicular to the submarine's horizontal axis (parallel to the Y-Z plane) at multiple points throughout the simulation.Consistent with the defined UDF, the submarine exhibits reciprocating rotational motion about its central axis, alternating between clockwise and counterclockwise rotation over the course of the simulation.

Self-Propelled Submarine Motion, Dynamic Mesh (6-DOF)DescriptionThis project simulates the motion of a self-propelled submarine floating on the water surface using the dynamic mesh method in ANSYS Fluent.This product is the fourth chapter of the Dynamic Mesh Training Course.The computational domain includes both air and water at a defined level, with the self-propelled submarine floating at the water's surface. The 3D geometry was designed using AutoCAD, CATIA, and ICEM CFD, with the submarine measuring 16.25 m in horizontal length and featuring several impellers with a diameter of 0.825 m at its rear.A cylindrical computational region was defined around the submarine within a larger cubic domain representing the full computational space. Meshing was carried out in ICEM CFD using a hybrid mesh — unstructured near the submarine hull, transitioning to a generally structured mesh across the remainder of the domain — totaling 2,802,219 elements.MethodologySince the grid cells shift position over time due to displacement at adjacent boundaries, the dynamic mesh model was used to capture this instantaneous grid movement. Three computational zones were established around the submarine, with smoothing and remeshing methods applied to handle the dynamic mesh behavior.Six degrees of freedom (6-DOF) were used to define the submarine's motion, allowing translational and rotational movement across all six directions. Mass and moment-of-inertia properties for the 6-DOF behavior were defined via a UDF.The submarine's hull was defined as a Rigid Body, along with a small surrounding cylindrical region also treated as rigid — together forming an integrated body capable of moving and rotating without internal mesh deformation. A larger cubic region surrounding this rigid zone was defined as a Deforming region to accommodate the motion. The rigid body definition also required specifying the submarine's center of gravity and its position within the model, with the submarine positioned floating at the water's surface.The VOF multiphase model was used to represent air in the upper portion of the domain and water in the lower portion, with both phases flowing horizontally (X-axis) at 1.62 m/s and exiting at atmospheric pressure. The open channel condition was applied at the outlet to define the water level, with the free surface set at 1.084824 m and the domain floor positioned at -100 m.Given the dynamic mesh foundation of this model, the simulation was run as transient, spanning 10 seconds with a time step of 0.001 seconds.ConclusionResults include 2D contours of velocity and volume fraction for both air and water phases across the floating submarine's surrounding regions, presented on the X-Y and Y-Z planes at the final second of the simulation. Additionally, diagrams tracking the submarine's translational and rotational displacement along all three axes (X, Y, Z) are provided, capturing the full 6-DOF motion behavior induced by the self-propulsion and surrounding flow conditions.

Fish Cage Floating on Seawater CFD Simulation by FSI Method, ANSYS FluentDescriptionThis project simulates a fish cage floating on the surface of seawater using the Fluid-Structure Interaction (FSI) method in ANSYS Fluent.The 3D geometry was designed in Design Modeler, representing a computational domain containing seawater, airflow, and a circular fish breeding cage. Since the model is perfectly symmetrical, only half of the geometry was modeled to reduce computational cost, with an inlet section, an outlet section, and symmetry conditions applied along the lateral faces.The domain was meshed in ANSYS Meshing, totaling 4,922,130 elements. Given the nature of FSI problems, a transient solver was used throughout.MethodologySince the fish breeding cage floats within the computational domain, seawater flow directly strikes the cage, requiring a two-way fluid-structure interaction to capture the coupled behavior between fluid and solid. This was implemented using the FSI method within the ANSYS Workbench environment.Because the fluid mesh structure changes around the geometry as the FSI simulation progresses, a Dynamic Mesh was required, using smoothing and remeshing methods to accommodate the time-dependent mesh changes. Two-way FSI was established through System Coupling in ANSYS Workbench, which required defining the model separately in both Fluent and Transient Structural, then coupling their solution processes.This coupling required two distinct data transfers: first, a Force transfer from the model wall in Fluent to the corresponding wall in Transient Structural — representing the force exerted on the cage as fluid flow strikes it; and second, a displacement transfer from the wall in Transient Structural back to Fluent — representing how the cage's structural deformation, in turn, alters the surrounding fluid flow.Since the fish cage operates within a two-phase domain (seawater and air), the VOF multiphase model was used, with air occupying the upper region and seawater the lower region. To represent the cage floating in open seawater, wave behavior was introduced via the Open Channel Wave boundary condition — incoming air and seawater entered at an average velocity of 3.08 m/s along the horizontal (y-axis), with the seawater floor set at -15 m and the free surface at 0 m. Airflow was discharged at atmospheric pressure.ConclusionResults were obtained from both Fluent and Transient Structural, all corresponding to the simulation's final time step (0.05 s). Transient Structural results include deformation, strain, and stress contours across the fish cage's structural body.Fluent results include 2D contours of velocity, pressure, and water/air volume fraction on the mid-plane (matching the symmetry plane), along with pressure distribution across the cage's body surface. The seawater wave surface itself was also extracted, showing 2D pressure and velocity contours and velocity vectors along it — clearly capturing the waves generated by the Open Channel Wave boundary condition in the volume fraction results.Structurally, the maximum deformation was observed in the thin connecting bars linking the cage's top and bottom holders — highlighting these as the most mechanically stressed components under the combined wave and current loading.