Hello everyone!
I would like to simulate an airflow over a pipe in Ansys Fluent. I want the flow at outlet of the pipe to be swirled.
How can I define the Swirl flow at the exit of the pipe?
Thank you!
Thank you for you reply.
But I mean by the question that I would like to add a BC or a User Defined Function at the outlet to make the swirl.
But I don't know how to do that!
Hi,
This completely depends on the geometry, boundary condition, and the model you use. To get an obvious swirl flow, I suggest modifying the pipe wall to have small helical fins.
Hi Hayder Ibrahim Mohammed,
Thank you for your suggestion!
I would like to use a UDF to modify the direction of the velocity vector at the exit of the pipe. Do you think this is possible?
With the UDF, everything is possible, but I guess developing such UDF is very difficult. you have to know the equations that controlling that type of motion.
Dear Doctor
Go To
A Study of the Swirling Flow Pattern when Using TurboSwirl in the Casting Process
Haitong Bai
Doctoral Thesis
Stockholm 2016
ISBN 978-91-7729-211-1
"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 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."
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