Why Use CFD

What is CFD?

CFD (Computational Fluid Dynamics) is a sophisticated mathematical analysis technique used for predicting the behavior of fluid in the flow field of interest, heat and mass transfer (e.g., precipitation, dissolution), phase change (e.g., melting, freezing, boiling), chemical reaction (e.g., combustion), mechanical movement (e.g., motion of pistons, fans and impeller), and even the stresses or deformation of related solid structures.  However, in layman's term, CFD is the computer solutions of a number of fundamental equations to predict pretty much any type of fluid motion.

The CFD analysis starts with dividing (or discretizing) the geometry to be modeled into usually a large number of small computational cells.  Discretization is the method of approximating the differential equations by a system of algebraic equations for the variables at some set of discrete locations in space and time.  The discrete locations are normally referred to as the "grid" or the "mesh".  This analysis is iteratively solving equations for the conservation of mass, heat, and momentum, and the dissipation of motion into turbulence.  The additional effects mentioned above are added into the solution procedure if needed.  The results are often presented graphically to assist in visualizing what's actually happening in the flow domain.

The generation of the computational grid is often the most labor intensive part of the CFD project.  The quality of the grid is extremely important and can strongly influence the solution – sometimes also determining whether or not a converged solution can be achieved at all.  The most important qualification about a computational meshing is that it must define enough points to capture everything of interest that is happening in the computational domain without becoming so extensive that unreasonable computation times are required.  If there are too few points included, some of the critical information about the flow regime may be completely lost.  It should also be noted that CFD models employ a number of assumptions to simplify the simulation procedure.  Thus CFD results may or may not exactly reflect reality.  Nevertheless, CFD has a proven track of record in accurately modeling a large number of situations.

Why use CFD?

In many industries, the design, scale-up, and operations of equipment rely heavily upon empiricism and correlations of overall parameters for non-ideal or non-equilibrium conditions.  Local effects are mostly not taken into account in design correlations.  Nonidealities introduced by scaling up of bench-top or pilot-scale equipment are usually difficult, if not possible, to predict empirically.  On the other hand, CFD allows for an in depth analysis of the fluid mechanics and local effects in many types of processing equipment, and through CFD analysis, we can quickly achieve improved performance, better reliability, more confident scale-up, improved product consistency, and even higher productivity.

CFD is an analysis tool capable of providing superior visualization and extensive information about flow-related phenomena in many different types of processing equipment that would not otherwise be available through conventional laboratory experiments.  Consequently, better and faster development will lead to shorter design cycles and compress the time between the conceptual stage and field implementation.  This will clearly be advantageous in the diagnosis and troubleshooting of existing equipment, evaluating retrofit designs, and hence minimizing down time.  Most importantly, it is apparent that process optimization will result in a substantial saving of time and expense. 

Over the years, AMWEL has acquired comprehensive knowledge for the optimization of designs and process efficiencies in oil and gas related equipment.  Occasionally, AMWEL provides CFD simulations for some companies even with their own CFD capability.  AMWEL can assist the clients to spend their valuable time on evaluating the CFD results and further designing improvements.