# How to Start CFD - Simulation for Beginners

## What is CFD (Computational Fluid Dynamics) and CFD Software?

Applying CFD simulation as a beginner or the question how to start computing fluid mechanic cases is not really complicated if you use NOGRID software. CFD (Computational Fluid Dynamics) is a branch of fluid mechanics that uses numerical analysis to solve problems that involve fluid flows. Computers are used to perform the computations required using CFD software to simulate the interaction of the fluid with boundaries defined by initial and boundary conditions. Fluid mechanics is the science that studies the physical behavior of fluids which are are mathematically stated through differential equations, the Navier-Stokes equations.

## Navier-Stokes equations

The fundamental basis of almost all CFD problems are the Navier–Stokes equations. The Navier–Stokes equations are a statement of the balance of momentum, but sometimes the equations for conservation of mass and the balance of energy are added.

In order to solve the Navier–Stokes equations the fluid domain must be discretized, which means the volume occupied by the fluid is divided into discrete cells (the mesh). The Finite Volume Method (FVM) is a common approach used in CFD codes, as it has an advantage in memory usage and solution speed, especially for large problems, high Reynolds number turbulent flows and source term dominated flows (like combustion). The Finite Element Method (FEM) is used in structural analysis of solids, but is also applicable to fluids. The Finite Difference Method (FDM) has historical importance and is easy to implement. It is currently only used in few specialized codes, which handle complex geometry with high accuracy and efficiency.

Figure 1: Navier-Stokes equations used in NOGRID software

## CFD software from NOGRID

NOGRID points CFD software based on the meshless Finite Pointset Method (FPM), is a software package for simulation tasks in the wide area of flow and continuum mechanical problems. The software doesn't solve only fluid flows, but also problems with elastic or plastic deformations. More generally spoken, NOGRID points considers all the viscous as well as elastic/plastic stress tensors and any mixture of it.

NOGRID points does not require a grid or mesh, in contrast to software products based on classical numerical methods, such as Finite Elements or Finite Volumes, where the generation of meshes takes a long time. NOGRID points can excellently be applied in case of all problems, where grid-based methods reach their limits due to the necessary remeshing. The CFD software is based on one of the latest technologies in the area of numerical flow simulation.

Figure 2: Stream lines in a 2-fluid heat exchanger computed with NOGRID points

## Introducing CFD Software in your Company

Introducing CFD software within a company requires very often some prearrangements. As Users know, a lot of parameters and conditions influence the final product feature and its quality. For example if the fluid viscosity is not known exactly, the results of the simulation can vary a lot.

The same is valid for the initial conditions. From practical point of view very often it is not possible to measure the initial temperature of a fluid completely. Companies are trying to measure the temperature in research projects, but the measured temperature is very often fluctuating (especially in glass industry).

For all these reasons the engineer has to make assumptions for the simulation and prove and adapt the simulation results by experiment.

Usually 3 steps are required for introducing the CFD software in your company:

1. Proof-of-concept phase
2. Pilot phase
3. Production phase

One of the ways to do a proof-of-concept is to create a benchmark and compute these benchmarks with the new simulation tool. The number of benchmark variations to be investigated in this phase depends on the branch, but should not be lower than 3. Due to the complex physics in each branch certainly more tests are required. This first phase will use the simulation tool on a small scale, with sufficient time to explore different ways in which it can be used. Objectives should be set for this proof-of-concept phase in order to accomplish what is needed within the current organizational context.

In the second phase, the pilot phase, one or more qualified designers/engineers start to evaluate the simulation software in the in-house production environment. The Users try to find best agreement between experiment and simulation:

1. Measure all experimental data available for the production case or benchmark
2. Compute the process by adapting the properties and the conditions until you reach best agreement between simulation and reality

After step 2 the User can start to change the product design or the real process conditions and prove it by simulation. If a good agreement is found also for the new benchmark, then the simulation was successful and should be able to predict futures product/production changes correctly .

Most unknown conditions and properties are found in this pilot phase. Furthermore a pilot phase is expected to have issues or problems – they should be solved in ways that can be used by everyone later on. The pilot project should experiment with all kinds of different products at different locations in order to include all possible conditions within the settings. The objectives for a pilot project for a new tool are:

• To learn more about the tool in detail and estimate and evaluate unknown conditions and material properties
• To see how the tool fits real process
• To decide on standard ways of using the tool that will work for all potential users
• To evaluate the pilot project against its objectives (have the benefits been achieved at reasonable cost?).

Finally, if the pilot phase is finished successfully one can start the third phase – the production phase. In this phase the software is rolled out to all designers/engineers in order to optimize a product or process or simply to check if a new product will produce difficulties or simply work fine without doing anything before going to production.

## Nogrid's strengths

NOGRID's particular strengths are the rapid preprocessing (no fluid grid needs to be generated, only the boundary mesh, inner finite points are generated automatically depending on User setting initially and during computation) and the outstandingly short computation time even for complicated cavities.
As you can see in the image below, the boundary of the geometry still requires a mesh to allow the interior finite points to detect the boundary. The boundary must therefore be meshed and the finite points inside are automatically generated during the simulation controlled by User specifications.

## What is CFD from NOGRID?

CFD solves the fundamental equations that define the fluid flow process. With CFD software from NOGRID every engineer makes better decisions by predicting, analyzing and controlling fluid flow, heat and mass transfer or chemical reaction. By using NOGRID software you receive information on essential flow characteristics as for example flow distribution. Using it additional to testing and experimentation NOGRID software helps to improve the evaluation of your design – resulting in better construction and operation parameters, increasing planning security and money savings due to faster time to the marketplace for your product or process.

## Choose NOGRID

With NOGRID, you choose professional CFD software and services – our aim is helping you to be successful. When you decide to work with NOGRID you choose close cooperation with a dynamic, flat hierarchies-organization. Short information channels result in quick and accurate professional support and service. Our team consists of highly qualified employees, who are experts in fields such as numerical simulation or computational fluid dynamics. Based on our know-how, we are pleased to offer the following services, responding to your individual requirements:

## TRAINING

In our two-days training courses you will learn, how to use NOGRID CFD software efficiently. Our technical support team will teach you how to handle and solve different cases.

For more details please refer to Training Courses →

## Technical Support

We offer full professional support from the minute you start using our software, by telephone or by email. Contact us, when ever needed.

For more details please refer to Software Support

## Service

Lack of time or resources and other constraints often make outsourcing an attractive solution. We help you with your flow modeling needs. Based on our engineering expertise in this field we offer individual numerical simulation services matching the unique needs of your organization.

For more details please refer to Simulation Services →

Göttelmannstr. 13B
55130 Mainz, Germany
info@nogrid.com