Embedded Files
ANSYS MESH USERS GUIDE
http://www1.ansys.com/customer/content/documentation/130/wb_msh.pdf
what is your cell skewness?
33.3.9.4. Checking the Skewness
Skewness is one of the primary quality measures for a mesh. Skewness determines how close to ideal (i.e., equilateral or equiangular) a face or cell is (see Figure 33.29).
Figure 33.29Â Ideal and Skewed Triangles and Quadrilaterals
Note:
Table 33.1: Skewness Ranges and Cell Quality lists the range of skewness values and the corresponding cell quality.
Table 33.1Â Skewness Ranges and Cell Quality
According to the definition of skewness, a value of 1 indicates an equilateral cell (best) and a value of 0 indicates a completely degenerate cell (worst). Degenerate cells (slivers) are characterized by nodes that are nearly coplanar (colinear in 2D).
Highly skewed faces and cells are unacceptable because the equations being solved assume that the cells are relatively equilateral/equiangular.
FLUENT"
Mesh Quality:
Orthogonal Quality ranges from 0 to 1, where values close to 0 correspond to low quality.
Minimum Orthogonal Quality = 5.28346e-02
Maximum Aspect Ratio = 1.21810e+02
overlapping named selctions in ansys fluent
Exporting Meshes or Faceted Geometry
Exporting Meshes or Faceted Geometry
When the same entity is a member of more than one Named Selection, those Named Selections are said to be “overlapping.” If you are exporting a mesh into the ANSYS FLUENT, POLYFLOW, CGNS, or ICEM CFD format (or faceted geometry into the TGrid format), and overlapping Named Selections are detected, the export will fail and you must resolve the overlapping Named Selections before proceeding. For details, see Showing Geometry in Overlapping Named Selections.Â
https://www.sharcnet.ca/Software/Fluent13/help/wb_msh/msh_export.html
LaTEX code:
7/18/12
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\begin{document}
\title{\Large \bf Salt River Project Spray Inlet Turbine Fuel Systems}
\begin{figure}
\centering
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\author{Michael Thompson$^{1}$,
Kevin Hargrave$^{2}$,
\\
\footnotesize Deapartment of Mechanical and Aerospace Engineering, Arizona State University, Tempe, AZ, USA \\
}
\date{July 31, 2012}
\maketitle
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% ABSTRACT %%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{abstract}
The aim of this reserach is to reduce the mesh size of an inlet trubine system. The
mesh size is approximately 500,000 element size. The computatioal time to run a simulation for this size mesh
is computationally expensize. The need to decrease the element size of the mesh is crucial in this project to increase computational time.
\end{abstract}
\vspace{.3in}
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\section{INTRODUCTION}
The purpose of this reserach to use FLUENT to determine what are the size of the dropplets from the TURBINE.
\subsection{Set Up}
\begin{itemize}
\item ECG 150. Set up the configuration for no machine
\end{itemize}
\subsection{To Do}
\begin{itemize}
\item Need to remesh the geometry file to decrease the number of elements
\item Need Signature from Dr. Lee for Isaac access to ISTB2 275
\item Need to Vary the temperature for the inlet
\end{itemize}
\subsection{Research Objectives}
\begin{itemize}
\item Decrease the number of elements in the mesh for faster convergence
\item Determine what are the size of the droplets? Sauter Mean Diameter (SMD) = 7.5 microns (droplets from the injector).
\item run steady state simulations for two phase flow mixing
\item How many particels are in the flow?
\end{itemize}
\section{Design of Simulations in FLUENT}
\begin{table}
\caption{Design of Simulations in FLUENT}
\begin{center}
\begin{tabular}{lllll}
\hline\\
Parameter & Simulatons (1-12) & Simulatons (1-12) & Simulatons (1-12) & Simulatons (1-12)\\
\hline\\
Temperature (F) &77 & 94 & 107 & 122\\
Relative Humidity \\(percent) & 27,20,10 & 27,20,10 & 27,20,10 & 27,20,10\\
Water Mass \\Fraction&0.005193 & 0.009454 & 0.0143 & 0.0216\\
Grids ON & All & All & All & All \\
(SMD) \\Injectors droplet size \\(microns) & 7.25,14.5,21.75,29 & 7.25,14.5,21.75,29 & 7.25,14.5,21.75,29 &7.25,14.5,21.75,29\\
\hline
\end{tabular}
\end{center}
\end{table}
%48 simulations will be ran
\begin{table}
\caption{Nomenclature }
\begin{center}
\begin{tabular}{llrlr}
\hline\\
Parameter & Descrition\\
\hline\\
T & Temoerature \\
$\phi$ &Relative humidity \\
mf & mass fraction \\
AB & Grid 1, 15 injectors simulated in FLUENT \\
C & Grid 2, 35 injectors simulated in FLUENT \\
D & Grid 3, 65 injectors simulated in FLUENT \\
E & Grid 4, 115 injectors simulated in FLUENT \\
\hline
\end{tabular}
\end{center}
\end{table}
Data was used From the Estimated Performance Summary on page 1 given from the case description from the combustion turbine characteristics. From SRP data, the four temperatures that were used in their case studies of the inlet to the turbine are used in the desing of simulations
in FLUENT. We will be creating simulations based on these temperatures along with the relative humidity, while running different grids of injetors. We expect that as the ambient temperature is increased the number of particles should decrease along with the size of the particles. FLUENT will be needed to solve 48 simulations from the desing of simulations and varrying parameters.
\clearpage
\section{Grid Refinement Case Studies}
To validate the the grid we may be able to do a grid refinement case study. The goal is reduce the number of elements in the mesh size.
\subsection{Optimization}
Help in efficient meshing with ANSYS Workbench engineering simulation from Youtube video. This is a good way to visually
validate the proximity based size function.
\begin{description}
\item[Making a more efficient geometry.] Simplify fillets by Face delete command.
Then extend the command to other fillets to delete other fillets to smoothen out the geometry.
\end{description}
\begin{itemize}
\item A proximity based mesh method was used. The method looks for small gap. We specify the number of cells within the gap.
\end{itemize}
\begin{itemize}
\item We requested 2 number oc cells for the gaps. The minumium size is $4 \times 10^-3$.
\end{itemize}
\begin{table}
\caption{Cell element Comparison}
\begin{center}
\begin{tabular}{llrlr}
\hline\\
Picture & Nodes Before & Nodes After & Cells Before & Cells After\\
\hline\\
CFD Mesh &856,123 & 695,863 & 505,019 & 399,144\\
& & 23percent reduction & & 27 percent reduction\\
&562, 123& 390,271 & 2,035,975 & 1,469,804\\
CFD Mesh & & 23percent reduction & & 27 percent reduction\\
\hline
\end{tabular}
\end{center}
\end{table}
\clearpage
\section{Mesh}
The mesh is shown here in the next two figures.
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%How to you insert a video file here????
%\begin{figure}[h!]
%\centering
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%\caption{My animation}
%\label{Anim1}
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\maketitle
\setcounter{page}{1}
\pagenumbering{roman}
\clearpage
\tableofcontents
\newpage
\listoftables
\newpage
\section{User Define Function}
A user defined function will be created to limit the coalescence size of the droplet. From the FLUENT manual on pages 230, 231, and 232.
An Example Code is found here: DEFINE DPM SPRAY COLLIDE
Description
You can use DEFINE DPM SPRAY COLLIDE to side-step the default ANSYS FLUENT spray
collision algorithm. When droplets collide they may bounce (in which case their velocity
changes) or they may coalesce (in which case their velocity is changed, as well as their
diameter and number in the DPM parcel). A spray collide UDF is called during droplet
tracking after every droplet time step and requires that Droplet Collision is enabled in the
Discrete Phase Model dialog box.
Usage
DEFINE DPM SPRAY COLLIDE(name,tp,p)
Argument Type Description
symbol name UDF name.
Tracked Particle *tp Pointer to the Tracked Particle data structure which
contains data related to the particle being tracked.
Particle *p Pointer to the Particle data structure where particles p
are stored in a linked list.
Function returns
void
There are three arguments to DEFINE DPM SPRAY COLLIDE: name, tp, and p. You supply
name, the name of the UDF. tp and p are variables that are passed by the ANSYS FLUENT
solver to your UDF. When collision is enabled, this linked list is ordered by the cell that
the particle is currently in. As particles from this linked list are tracked, they are copied
from the particle list into a Tracked Particle structure.
Example
The following UDF, named mean spray collide, is a simple (and non-physical) example
that demonstrates the usage of DEFINE SPRAY COLLIDE. The droplet diameters are
assumed to relax to their initial diameter over a specified time t relax. The droplet
velocity is also assumed to relax to the mean velocity of all droplets in the cell over the
same time scale.
/***********************************************************
DPM Spray Collide Example UDF
************************************************************/
(pound sign) include "udf.h"
(pound sign)include "dpm.h"
(pound sign)include "surf.h"
$DEFINE_DPM_SPRAY_COLLIDE (mean_spray_collide,tp,p)$
{
/* non-physical collision UDF that relaxes the particle */
/* velocity and diameter in a cell to the mean over the */
$/* specified time scale t_relax */$
$const real t_relax = 0.001; /* seconds */
/* get the cell and Thread that the particle is currently in */
cell_t c = P_CELL(tp);
Thread *t = P_CELL_THREAD(tp);$
/* Particle index for looping over all particles in the cell */
Particle *pi;
/* loop over all particles in the cell to find their mass */
/* weighted mean velocity and diameter */
int i;
$real u_mean[3]={0.}, mass_mean=0.;
real d_orig = P_DIAM(tp);
real decay = 1. - exp(-t_relax);
begin_particle_cell_loop(pi,c,t)$
{
$mass_mean += P_MASS(pi);
for(i=0;i<3;i++)
u_mean[i] += P_VEL(pi)[i]*P_MASS(pi);$
}
$end_particle_cell_loop(pi,c,t)
/* relax particle velocity to the mean and diameter to the */
/* initial diameter over the relaxation time scale t_relax */
if( mass_mean > 0. )$
{
for(i=0;i<3;i++)
$u_mean[i] /= mass_mean;
for(i=0;i<3;i++)
P_VEL(tp)[i] += decay*( u_mean[i] - P_VEL(tp)[i] );
P_DIAM(tp) += decay*( P_INIT_DIAM(tp) - P_DIAM(tp) );
/* adjust the number in the droplet parcel to conserve mass */
P_N(tp) *= CUB( d_orig/P_DIAM(tp) );$
}
}
\subsection{Simulation 1, Vary Inlet Temperature}
\noindent Here's my list:
\begin{enumerate}
\item Steady state simulation with 200 iterations
\item The residuals are changed from default, $10^{-3}$ to $10^{-6}$ to increase accuracy of the system
\item Species Mass fraction = 1-degreeF = 1- 0.117 - 0.9883. The species mass fraction is at 27 percent relative humidity
\item If the temperature is greater than 100 degreesF than use thermodynamics book on page 953 to get correct value.
\item The relative humidity for 100degree F is about 70 percent
\item Mass fraction = 1-degreeF
\item If the temperature is greater than 100 degreesF than use thermodynamics book on page 953 to get correct value
\item The relative humidity for 100degree F is about 70 percent
\item The Discrete Phase Model (DPM) will be used heavily in this study of mixing flows.
\item Contours of DPM anbd DDM for number of particles will be looked at to count the number of particles after simulation is done.
\end{enumerate}
\subsection{Simulation 2, Vary Inlet Temperature}
\noindent Here's my list:
\begin{enumerate}
\item Steady state simulation with 200 iterations
\item Temperature = 105 degree F = 40.5 degree C
\item From thermodynamics book on page 953 the relative humidity is 27 percent
\item From thermodynamics book on page 953 the water mass fraction = 13g/kg = 0.013 kg/kg = 0.013
\item The red line curves are the relative humidity on page 953 in the thermodynamics book
\item The Discrete Phase Model (DPM) will be used heavily in this study of mixing flows.
\item Contours of DPM anbd DDM for number of particles will be looked at to count the number of particles after simulation is done.
\end{enumerate}
\section{Actual Model}
\begin{enumerate}
\item An Inlet to Turbine is the real model. The turbine has 28 rows of injectors with 4 grids. The grids are AB, C, D, and E. Each row has 52 injectors.
The grid arrangment is as follows: AB has 3 rows of injectors with 2 GPM, C grid has 4 rows with 6 GPM, D grid has 7 rows of injectors with 18 GPM, E grid has 14
rows of injectors with 26 GPM.
\end{enumerate}
\section{CAD Model}
\begin{enumerate}
\item An Inlet to Turbine is the cad model. The cad model has a full set of injectors, a solencer, mixing of two phase flow. The CAD model follows up intil the compressor. The compressor is not modeled. The CAD model has a total of 230 injectors. The nozzle is defined as the injector.
\end{enumerate}
\section{FLUENT}
\begin{enumerate}
\item Define, injecttions, highlight all to change the the point properties or to change water properties
\item water temperature is 27degree c or 300 degree K
\item The relative humidity for 100degree F is about 70 percent
\item Mass fraction = 1-degreeF
\item If the temperature is greater than 100 degreesF than use thermodynamics book on page 953 to get correct value
\item The relative humidity for 100degree F is about 70 percent
\item The Discrete Phase Model (DPM) will be used heavily in this study of mixing flows.
\item Contours of DPM anbd DDM for number of particles will be looked at to count the number of particles after simulation is done.
\item The maximum = $3.95 \times 10^{7}$ particles
\item The minimum = 1
\item Models, discrete phase, particle step size (0.02sec)
\item Spray Model, Droplet Collision, Droplet Breakup, Break Model (tab)
\item Particle Tracks, Graphics and annimation, particle variable, Particle Diameter (Based on time step size = 0.02 sec for 1 second of particle movement
\item $200/4 = 50 DPM \times 0.02 sec = 1$ second of particle movement
\item Number of iteration per DPM continuous iteration = 4
\item To do each time highlight and release from injector located in display
\end{enumerate}
\begin{eqnarray}
Drag = 0.5 \times \rho V^2 C_{D} A
\end{eqnarray}
\section{CFD VALLIDATION}
\subsection{Grid Refinement Case Studies}
To validate the the grid we may be able to do a grid refinement case study.
\subsection{Experimental studies with nozzle case Studies}
To validate the numerical simulations we may be able to conduct nozzle tests for validation.
\section{FUTURE WORK}
\subsection{Transient Case}
To validate steady state simulatons a transient simulation may be done. The simulaton may look at vorticity effects of the swirlig of the flow.
\subsection{Experimental studies with nozzle case Studies}
The experimental studies will be conducted in teh future with a nozzle. A LDV laser will be used.
The first steps are to begin bringing back to life
the device. The first step is to plug everything in and to see if the device works. Next, find the manual.
To validate the numerical simulations we may be able to conduct nozzle tests for validation.
\begin{thebibliography}{15}
\bibitem{c1}
where is our ref
\end{thebibliography}
\end{document}
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