Computational Fluid Dynamics

Today, thanks to the great advancement of computer performance, the numerical computation of fluid flow problems by means of Computational Fluid Dynamics (CFD) has become widely adopted in the industry. Inherent to being the world’s leading dredging equipment supplier, many of IHC Merwede’s products heavily rely on the principles of fluid flow, such as (among many others) centrifugal pumps, pipe systems, cutter heads and of course ship hulls. Consequently, CFD currently serves as a solid base for the continuously ongoing efforts on improving current design concepts as well as new product innovation at IHC Merwede.

Principles
The term Computational Fluid Dynamics refers to a numerical technique in which mathematical equations describing the motion of fluid flow are solved (on a computer) in order to obtain a flow field within a region of interest. These mathematical equations are derived from the physical principles of conservation of mass, momentum and energy which apply to all fluids. The advantage of such a method is that the resulting flow fields are purely driven by physics as opposed to those obtained by empirical relations.

In the process of CFD, the domain of interest (e.g. pump or pipe) is subdivided into a large number of cells (or elements) referred to as the computational mesh. Within each cell of the mesh, the above described conservation principles are enforced. Together with appropriate boundary conditions this results in the numerical solution of the flow field in the region under consideration. In the first place, this solution consists of the so-called dependent variables such as velocity and pressure within each cell. Next, these variables can be used to compute global quantities of interest such as for example pump characteristics (head, power, efficiency) or the total drag of a ship hull.

Note that with this approach a detailed image of the flow field is obtained, as the solution comprises the flow variables at each cell of the mesh. This allows for easy visualisation of the flow in regions where measurements can be very difficult or even impossible to obtain. Insight into the physical flow phenomena that play an important role in the problem under consideration is of utmost importance as it provides the guidelines for improvement of existing products. For example, identification of strong vortices in centrifugal pumps responsible for excessive wear allows specific measures to prevent these flow structures from developing. In this way, CFD play a key role in the continuous product development and innovation research at MTI Holland.