The Combined Power of Tecplot 360 and FLOW-3D® Help Engineers Improve Flow Energy Dissipation

The Challenge

Create a way to optimally transport waste water

Hydro science is a complex discipline. Researchers in the Civil Engineering Department's Hydraulic Engineering Section at the University of Wuppertal in Germany are using FLOW-3D ® CFD flow modeling software and Tecplot 360 visualization software to analyze the flow of wastewater through underground pipes to help determine the optimal way to transport the wastewater.

Sometimes, urban wastewater is transported in large underground pipes or channels with very large diameters. In this study, a pipe with a diameter of 2.4 m (DN2400) needed to connect up with another pipe that was 2.2 m in diameter (DN2200) and 4.5 m lower than the first pipe.

The Researcher

Mario Oertel, a PhD candidate at the University of Wuppertal, has used Tecplot software for only one month, but he is already seeing the benefits of its advanced visualization capabilities. To help him understand the complex simulation results produced by FLOW-3D ®, he is using Tecplot 360 visualization software to plot the results.

The Solution

Use CFD and Effective Visualization to Find a Design that Would Efficiently Dissipate the Energy of Water Flow

To obtain efficient energy dissipation, several design scenarios were proposed. Among the options, Oertel says, were a simple shaft, or freefalling water, helices or a cascade structure. However, since there is no standard solution for the existence of large discharges, the planned cascade structure might have problems dissipating the energy. As a result, the research team decided to explore the cascade design in order to obtain efficient energy dissipation.

"It is necessary to dissipate energy with each of the cascade's steps," Oertel explains. "The water flows with very high velocities in a supercritical order through this pipe so there is a high energy in this system. In addition, the level differences between the two pipes also bring additional energy into it. We presumed several problems to get optimal energy dissipation with these cascades and needed to take a deeper look into the resulting flow situation."

Using the cascade building design, only a small part of the energy is dissipated. After the solution from this cascade design was calculated in FLOW-3D ®, Oertel used Tecplot software to visualize the FLOW-3D ® results, which enabled him to better understand the flow characteristics of the proposed cascade design.

In addition to the 3D plots he produces to get a good look at the overall system, Oertel uses Tecplot 360 to create 2D plots to get a better look at specific cross sections of the model. The Tecplot results gave the researchers a better understanding of the velocity and the energy in different cross sections, as well as, the stream traces influenced by the turbulence in the areas of the different steps. "It is important for us to get this information because it shows if the energy dissipation is working well or not. At the same time we're able to estimate the stress on the structure," says Oertel.

Analyzing the Results

The plots revealed that the steps had a negative influence on the energy dissipation because the flow velocities were too high for large discharges. There the supercritical inflow into the structure makes it impossible to dissipate the energy in an efficient way. "For low discharges, the dissipation was good," says Oertel. "But when 20 m3/s are flowing through the pipe, the cascade structure has no chance to influence the flow significantly."

Therefore another solution was explored to handle the supercritical flow regime. The final build up structure was a Two-Steps-Shaft with steps in varying space directions (x and y). With this structure the energy can be well dissipated and the water starts flowing into the lower pipe at lower velocities due to hydrostatic pressure influence.

Oertel credits Tecplot 360 and it's FLOW-3D ® data loader for its ability to handle large data files, its easy-to-use interface, and its ability to export many different formats. "The export features enable me to send the results via email to my colleagues," says Oertel. "Tecplot 360 also enables me to export *.esp files for my PhD thesis, so I have the best quality for my graphics."