
Solvent 

What is CFD? 


Computational Fluid Dynamics (CFD) is a branch
of engineering that deals with the numerical solution of the equations
governing the conservation of mass, momentum, energy, and related
parameters. The numerical solution is obtained over a finite number
of locations (called grid points) in the calculation domain. A discretization
method is used to convert the parent differential equation into algebraic
relations involving the values of the dependent variables for a group
of grid points. A suitable algorithm is used for the solution of these
algebraic equations. Some examples of the commonly used discretization
methods are the finitedifference method, finitevolume method, and
finiteelement method. Here, we give a brief overview of the finitevolume
method, which is the basis of SOLVENT; for other methods, please refer
to appropriate textbooks.


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FiniteVolume Method 



In the finitevolume (or controlvolume)
method, the calculation domain is divided into a number of nonoverlapping
control volumes such that there is one control volume surrounding
a grid point. The differential equation is integrated over each control
volume. Piecewise profiles expressing the variation of the dependent
variable between two grid points are used to evaluate the required
integrals. The result is the algebraic equation containing the values
of the dependent variables for a group of grid points. The most attractive
feature of the finitevolume method is that the resulting solution
would imply integral conservation of quantities such as mass, momentum,
and energy is exactly satisfied over any group of finite volumes and,
thus, over the entire calculation domain. This property exists for
any number of grid pointsnot just when the number of grid points
becomes large. 

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Steps in a CFD Simulation 



In broad terms, CFD simulation of a physical situation involves
the following steps:
 Specification of the geometric details.
 Specification of the equations to be solved (i.e., the mathematical
model). In addition to the basic equations governing the conservation
of mass, momentum, and energy, these equations will include, for
example, the equations for turbulence model, combustion model,
and radiation model.
 Specification of the boundary and initial conditions.
 Specification of the transport properties.
 Use of a numerical method for solving the equations. Often
special techniques must be employed to resolving the coupling
between various equations (e.g., the velocitypressure coupling);
these details are part of the numerical method.
 Postprocessing of the numerical results.




Advantages of CFD 



Use of a CFD model allows you to analyze your problem
in much greater detail, in much shorter time, and at a much lower
cost compared to testing. A CFD model provides complete details of
your problems. For example, you obtain the values of pressure, velocity
components, temperature, etc., over the entire calculation domain.
CFD gives you the ability to simulate realistic conditions. You no
longer have to resort to smallscale or coldflow models. CFD is an
ideal complement to traditional testing and experimentation. It gives
you an insight into the physical processes and enables you to improve
your design. 



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