Abstract:

Computational Fluid Dynamics (CFD) is the knowledge area that numerically simulates the flow of fluids. These computational tools, once validated, allow a spatial visualization of a phenomenon under study and have a high precision degree, allowing a better understanding of fluid mechanics.

During the last years, CFD has become a widely used tool in the industry, since the simulation cost is minor than the one of laboratories’ experimentation. Additionally, CFD is an effective tool for comparing design alternatives, investigating specific flow characteristics, and, in some cases, might be the only viable option for studying certain engineering flows. Consequently, it is not surprising the increase on the demand for engineers capable of handling these tools.

However, CFD tools are not yet commonly featured in undergraduate programs and textbooks. As a consequence, CFD products are often used as a “black box”, where users provide minimal inputs (eg geometry and input speed / free flow) without knowing exactly what the software performs. One way to partially address CFD in undergraduate engineering courses is to introduce computational simulation by validating laboratory experiences previously performed by students. This allows to overlap theoretical, experimental and computational simulation knowledge. This paper presents the integration of the CFD in a Fluid Mechanics course, corresponding to the 3rd level of the Civil Engineering degree in Civil Works at the University of Talca, Chile.

In particular, the determination of the fluid flow rate is an area of paramount application, and there are numerous devices that allow its measurement. Some examples of differential pressure flowmeters meters are the Venturi tube, the orifice plate or the nozzles. They basically consist of an element that throttles the flow and generates a change in the piezometric load, which translates into a loss of energy.

For some industries, knowing the flow rate becomes critical to maintain the production’s quality. Consequently, the use of flow meters and controllers is essential. Flow rates obtained with theoretical equations tend to be slightly higher than actual flows. Therefore, correction factors such as the discharge coefficient (Cd) are introduced. The Cd values are normally obtained from curves that are a function of the Reynolds number.

This work integrates theoretical, laboratory and computer simulation teaching in a generic course on fluid mechanics. The students will become capable to understand the deviation between theoretical and real measurements, and to calculate, through their own experience, the discharge coefficients. The applied integration method consists of three steps. First, the teacher explains in the classroom the theoretical foundations regarding the measurement experience and the fundamentals of CFD. Second, students experiment on a laboratory bench, taking measurements in an orifice plate tube and in a Venturi tube. Finally, the students propose and develop a computational model based on CFD that simulates these same elements of flow measurement using ANSYS Fluent. The validity of the model is checked by comparing the results obtained in the experimental measurements with those obtained by CFD simulation. Once the model has been validated, the students compare the discharge coefficients obtained in their computational simulation with the theoretical values from the literature.

Keywords:

CFD, Fluid Dynamics, integration, Civil Engineering.