CFD Simulations of Pressure Loss in Pipes with Different Geometries

Abstract: The passive security systems protect the passengers when the car has an
important accident. These systems are based in a good and strength car
structure to not deform the passenger cabin. In Gestamp Hardtech are
producing pieces with an important strength without increasing the car
weight. These pieces are produced using the hot stamping process and one of
the most important parts of this process is how the piece is cooled after it
is transformed to the final shape. Is in this point is where this master
thesis could help studying the hot stamping tool cooling system that
transfer de heat from the tool to the cooling water.

In this study we used the computational fluid dynamics (CFD) that is an
important tool to obtain results in fluids problems. This method based on:
the RANS (Reynolds average Navier Stokes equations) and in the k – epsilon
model to closure it, the approximation to the derivation formulas and the
space discretization on a mesh: gives us the solution that we are searching
with enough accuracy and without spending a lot of time.

The Master Thesis has been done in two different parts:

The first part studies different standardized pipes using a hexahedral mesh
and steady simulation to obtain the pressure drop in different cases and the
flow shape in the outlet. The results are compared to standard results and
format to be in agreement.
The results were enough good for the quality that we need: RMS around 10-4,
Y plus between 150 and 10 and the minimum face angle always over 20. The
drop pressure found is similar than the studied bibliography and it is show
in the report tables.

The second part the studies the hot stamping tool’s cooling system. A
tetrahedral mesh was used. In this case we centre our study in the flow rate
in each tool’s channel. The results indicate variation of 30% between the
different channels. They need a posterior validation with experimental data.