To induce a swirling motion at the exit of a conduit using Fluent, you can set a tangential velocity component at the inlet boundary, representing the rotational flow entering the conduit. In the 3D simulation, both radial and tangential velocity components must be specified at the inlet.

In the 2D scenario, the governing equations for the simulation are the Reynolds-Averaged Navier-Stokes (RANS) equations, accounting for two spatial dimensions (x and y) and time (t).

For the 3D case, the simulation's governing equations are also the Reynolds-Averaged Navier-Stokes (RANS) equations, but they consider three spatial dimensions (x, y, and z) and time (t)."

Thank you Abdellatif M. Sadeq for your response!

In your opinion, what is the adequate turbulence model in this case ?

The k-ε, k-ω, SST, and realizable k-ε models are commonly used RANS turbulence models for swirling flows. The k-ε model is preferred for its computational efficiency and ability to handle moderate to high turbulence intensity flows with well-established swirling patterns. The k-ω model performs well in specific swirling flow scenarios, particularly near walls and in separated flows. The SST model is a hybrid model that transitions between k-ω and k-ε based on flow conditions, making it versatile for various applications, including swirl-induced motion with flow separation and reattachment. The realizable k-ε model is an advanced version that provides improved predictions for swirling flows with complex patterns.

The choice of the best turbulence model depends on specific flow conditions, accuracy requirements, and available computational resources, emphasizing the need for sensitivity analyses and model comparison to select the most appropriate one for accurate simulations.

You're right ! Thanks

If the conduit is crossed by the flow. In that case, the conduit is inside a flow domaine.

How to define the boundary conditions at the conduit exit?

In ANSYS Fluent, when a conduit is inside a flow domain, you can define the boundary conditions at the conduit exit. This involves selecting the appropriate boundary condition type, such as Pressure Outlet, Outflow, or Mass Flow Outlet, and setting the necessary parameters, such as pressure or mass flow rate. Ensure proper mesh refinement near the exit and create a separate boundary zone for applying the specified conditions. Run the simulation to observe the flow behavior and verify that the boundary conditions align with your analysis objectives and the physical phenomenon being simulated.

how to do that? the exit of conduit is not available in fluent to define in it BC.

You need to Identify the cell or face corresponding to the conduit exit, as this is the specific location where you intend to define the boundary conditions.

Dear Doctor

Go To

A Study of the Swirling Flow Pattern when Using TurboSwirl in the Casting Process

Haitong Bai, 2016, Sweden

ISBN 978-91-7729-211-1

"Abstract

The use of a swirling flow can provide a more uniform velocity distribution and a calmer filling condition according to previous studies of both ingot and continuous casting processes of steel. However, the existing swirling flow generation methods developed in last decades all have some limitations. Firstly, the swirl blade inserted in the SEN in the continuous casting process or in the runner in the ingot casting process is difficult to manufacture. Furthermore, it results in a risk of introducing new non-metallic inclusions to the steel during casting if the quality of the swirl blade is not high. Another promising method that has widely been investigated is the electromagnetic stirring that requires a significant amount of energy. Recently, a new swirling flow generator, the TurboSwirl device, was proposed. The asymmetry geometry of the TurboSwirl can make the fluid flowing to form a rotational motion automatically. This device was first studied for ingot casting. It is located in the intersection between the horizontal runner and the vertical runner connected to the ingot mold. The swirling flow generated by the TurboSwirl device can achieve a much calmer filling of the liquid steel compared to the conventional setup and also to the swirling flow generated by the swirl blade method.

Higher wall shear stresses were predicted by computational fluid dynamics (CFD) simulation in the TurboSwirl setup, compared to the conventional setup. In this work, the convergent nozzle was studied with different angles to change the swirling flow pattern. It was found that the maximum wall shear stress can be reduced by changing the convergent angle between 40º and 60º to obtain a higher swirl intensity. Also, a lower maximum axial velocity can be obtained with a smaller convergent angle. Furthermore, the maximum axial velocity and wall shear stress can also be affected by moving the location of the vertical runner and the convergent nozzle. A water model experiment was carried out to verify the simulation results of the effect of the convergent angle on the swirling flow pattern. The intensive swirling flow and the shape of the air-core vortex in the water model experiment could only be accurately simulated by using the Reynolds Stress Model (RSM). The simulation results were also validated by the measured radial velocity in the vertical runner with the help of the ultrasonic velocity profiler (UVP).

The TurboSwirl device was further applied to the design of the submerged entry nozzle (SEN) in the billet continuous casting process. The TurboSwirl was reversed and connected to a traditional SEN to generate the swirling flow for the numerical simulations and the water model experiments. The periodic characteristic of the swirling flow and asymmetry flow pattern were vi observed in both the simulated and measured results. The detached eddy simulation (DES) turbulence model was used to catch the time-dependent flow pattern and the predicted results agree well with measured axial and tangential velocities. This new design of the SEN with the reverse TurboSwirl could provide an almost equivalent strength of the swirling flow generated by an electromagnetic swirling flow generator. It can also reduce the downward axial velocities in the center of the SEN outlet and obtain a more calm meniscus and internal flow in the mold. Furthermore, a divergent nozzle was used to replace the bottom straight part of the SEN. This new divergent reverse TurboSwirl nozzle (DRTSN) could result in a more beneficial flow pattern in the mold compared to the straight nozzle. The swirl number is increased by 40% at the SEN outlet with the DRTSN compared to when using the straight nozzle. The enhanced swirling flow help the liquid steel to generate an active flow below the meniscus and to lower the downwards axial velocity with a calmer flow field in the mold. The results also show that the swirl intensity in the SEN is independent of the casting speed. A lower casting speed is more desired due to a lower maximum wall shear stress. An elbow was used to connect the reverse TurboSwirl and the tundish outlet to finalize the implementation of the reverse TurboSwirl in the continuous casting process. A longer horizontal runner could lead to a more symmetrical flow pattern in the SEN and the mold."

Thank you Sundus F Hantoosh for you response !