Computational fluid dynamics, or more commonly known as CFD, is a field of study used to solve different types of fluid flow problems. It provides both qualitative and sometimes quantitative analysis by combining very difficult mathematical models, numerical approximations, and computer software.
The Navier-Stokes equations are a set of non-linear partial differential equations with very few exact solutions that exist. These equations represent a mathematical model that is valid for the entire field of flow being analyzed. This means there are an infinite number of points in any flow field being analyzed where a solution to these equations exist. In order to realistically solve a problem, the field of flow is broken up in small chunks with a finite number of discrete points. The result of this process of discretization is what is referred to as a mesh.
There are several different methods used to approximate the Navier-Stokes equations that you can read about in more detail. Essentially, at each point in the mesh there will be algebraic approximations of the Navier-Stokes equations that are used to solve the problem. The numerical method used to approximate the solution may use a combination of conservation equations (mass, momentum, energy), a combination of continuous functions of the fluid (pressure, velocity, etc.), and several others. The method chosen is typically defined by the software program that is purchased by the user. It is important to make sure the method being used is compatible with the problem. This is one reason the user needs to understand the fluid problem being analyzed. The numerical methods are solved using an iterative approach until some convergence criteria are met. This is where the software is needed to run calculations at millions of different points within the flow field.
CFD is beneficial because it is a user-friendly way to quickly solve many different types of flow problems. This provides users with a general understanding of fluid mechanics a tool to solve otherwise very complex fluid flow problems. A program can quickly be changed from running calculations that determine the maximum entrainment of a thermocompressor (which was discussed in an earlier blog post), the pressure drop through a new rotary joint, fluid path through a tank to optimize heater placement, maximize the performance of PTX® syphon equipment, etc.
Without CFD some of those could be obtained experimentally, and some of them would have required over simplifications of fluid mechanic equations. CFD is a widely-used tool across many product lines to further optimize the performance and ensure our customers get the best product possible.