FILE PARSING OF NASA S THERMAL DATA AND CALCULATION OF VARIOUS PARAMETERS

FILE PARSING

Often in the real world, a large amount of data which is used for development purpose are stored in .txt or.DAT file formats but these files contain very large amounts of data which is difficult to enter them back manually and make use of them

BUT

These files are stored in a pattern which when figured out can be inputted or converted easily into usable data with lines of code, this process is called file parsing

Now to give u an example

PART 1:

let's consider this data

THERMO
   300.000  1000.000  5000.000
! GRI-Mech Version 3.0 Thermodynamics released 7/30/99
! NASA Polynomial format for CHEMKIN-II
! see README file for disclaimer

this data consists of coefficients to calculate specific heat, enthalpy and entropy

now if we start inputting this data manually like

global low temp =200

global mid temp=1000

global high temp=5000

a1=2.5694e+00

so to overcome that we need to observe a pattern

so if we see here

• in the first line, we have the name of the file
• in the next three lines, we have a description of the data

to get this data we are going to write a code in Matlab

f1=fopen(\'THERMO.DAT\',\'r\')
fgetl(f1)
a=fgetl(f1)
b=strsplit(a,\' \')
global_low_temperature=str2num(b{2})
global_mid_temperature=str2num(b{3})
global_high_temperature=str2num(b{4})
for i=1:3
    a=fgetl(f1)
end

The first line of the code

f1=fopen(\'THERMO.DAT\',\'r\') --is used to open the file in which the data is stored and assign it to a variable f1,\'r\' represents the permission to read

second line

fgetl(f1) is a command used to get a line (we have to keep in mind that the number of times we use this command is the line number which it is going to print out, so if we have used this command 5 times on the sixth time it's going to get the sixth line)

third line

a=fgetl(f1); is used to load the second line and store it in variable 'a' (as it contains some of the usable data)

fourth line

b=strsplit(a,\' \') splits the string \'a\' into different string where ever there is a \'space\' with the command \'strsplit\' and stores the elements in array \'b\'

fifth line

global_low_temperature=str2num(b{2}); converts the string element which is stored at index of the array \'b\' into a integer value and store them into the variable

similarly sixth, the seventh line

8th,8th,10 is a loop is used to get the unwanted description

for 5TH LINE OF THE DATA, we observe useful content which is written in a specific pattern which repeats itself

O                 L 1/90O   1               G   200.000  3500.000  1000.000    1
 2.56942078E+00-8.59741137E-05 4.19484589E-08-1.00177799E-11 1.22833691E-15    2
 2.92175791E+04 4.78433864E+00 3.16826710E+00-3.27931884E-03 6.64306396E-06    3
-6.12806624E-09 2.11265971E-12 2.91222592E+04 2.05193346E+00                   4
O2                TPIS89O   2               G   200.000  3500.000  1000.000    1
 3.28253784E+00 1.48308754E-03-7.57966669E-07 2.09470555E-10-2.16717794E-14    2
-1.08845772E+03 5.45323129E+00 3.78245636E+00-2.99673416E-03 9.84730201E-06    3
-9.68129509E-09 3.24372837E-12-1.06394356E+03 3.65767573E+00                   4

• The data starts with the species name and ends with local temp data

to get this data we can write a code

the first line consisting of different types of data like characters , integers so

c=fgetl(f1);
b=strsplit(c);
species=string(b(1));
llt=str2num(b{length(b)-3});
lmt=str2num(b{length(b)-1});
lht=str2num(b{length(b)-2});

here

in 1st line

c=fgetl(f1); we are loading the data from file and store in the variable in c

2nd line

b=strsplit(c); splits the line into cell elements and store them into an array \'b\'

3rd line

species(i)=string(b(1)); will convert cell elements to string elements and store them in the species variable, here b(1) represents the first element of array b

4th,5th,6th line

llt=str2num(b{length(b)-3});
lmt=str2num(b{length(b)-1});
lht=str2num(b{length(b)-2}); are used to convert string elements to integer values using\'str2num\' command

2.56942078E+00-8.59741137E-05 4.19484589E-08-1.00177799E-11 1.22833691E-15    2
 2.92175791E+04 4.78433864E+00 3.16826710E+00-3.27931884E-03 6.64306396E-06    3
-6.12806624E-09 2.11265971E-12 2.91222592E+04 2.05193346E+00                   4

these lines of data contain coefficients to retrieve them

            c=fgetl(f1)
            s=findstr(c,\'E\');
            a1=str2num(c(1:s(1)+3));
            a2=str2num(c(s(1)+4:s(2)+3));
            a3=str2num(c(s(2)+4:s(3)+3));
            a4=str2num(c(s(3)+4:s(4)+3));
            a5=str2num(c(s(4)+4:s(5)+3)); 

here in 2nd line

s=findstr(c,\'E\'); we are finding a particular string \'E\' as it appears in every coefficient and notes the index of array \'c\' at which they appear and store them in another array \'s\'

3rd line

a1(i)=str2num(c(1:s(1)+3)); converts the strings into integers ,here c(1:s(1)+3) represents the string elements which lie in between 1 and (s(1)+3) as s(1) stores values of the indexes of \'E\' in string \'c\'

similarly 4th,5th,6th,7th

this code applies to the next 2 lines of the data also

PART 2:

But, what if we contain a large file of data which is in a pattern and repeats itself in a particular sequence

here comes the use of for loops

we can use the above codes and put them in a for loop, but this time them variables are going to arrays

so here is the code for repetitive data blocks

for i=1:53
    
    for j=1:4
        c=fgetl(f1);
        if j==1
            b=strsplit(c);
            species(i)=string(b(1));
            llt(i)=str2num(b{length(b)-3});
            lmt(i)=str2num(b{length(b)-1});
            lht(i)=str2num(b{length(b)-2});
        
        elseif (j==2)
            s=findstr(c,\'E\');
            a1(i)=str2num(c(1:s(1)+3));
            a2(i)=str2num(c(s(1)+4:s(2)+3));
            a3(i)=str2num(c(s(2)+4:s(3)+3));
            a4(i)=str2num(c(s(3)+4:s(4)+3));
            a5(i)=str2num(c(s(4)+4:s(5)+3)); 
        elseif (j==3)
            s=findstr(c,\'E\');
            a6(i)=str2num(c(1:s(1)+3));
            a7(i)=str2num(c(s(1)+4:s(2)+3));
            a8(i)=str2num(c(s(2)+4:s(3)+3));
            a9(i)=str2num(c(s(3)+4:s(4)+3));
            a10(i)=str2num(c(s(4)+4:s(5)+3)); 
        else (j==4)
            s=findstr(c,\'E\');
            a11(i)=str2num(c(1:s(1)+3));
            a12(i)=str2num(c(s(1)+4:s(2)+3));
            a13(i)=str2num(c(s(2)+4:s(3)+3));
            a14(i)=str2num(c(s(3)+4:s(4)+3));
        end            
    end
end

by doing this we have successfully read the entire data file and allocated the values in a meaning full fashion and store them in variables

PAR 3:

Coming to the calculation part

here we are going to calculate different parameters sung the data we have parsed

element=input(\'enter the element name : \',\'s\')
i=find(species==element)

in the 1st line

element=input(\'enter the element name : \',\'s\')

we are asking to select a species and store it in the variable \'element\', \'s\' is needed when we are inputting aa string

2nd line

i=find(species==element) we are finding the index of the string which we have entered in the 'a' array \' species\'

1)MOLECULAR WEIGHT CALCULATION

mol_wt=molecular_weight(element)

here we are calling the function which calculates the molecular weight of the element which we have inputted above, we are sending the element string as an argument

here is the function

function [wt]=molecular_weight(element)
l=[\'H\',\'C\',\'N\',\'O\',\'A\',\'R\'];
atomic_weight=[1 12 14 16 40 0];
wt=0
for i=1:length(element)
    v=isletter(element(i));
    if v==1
        n=find(l==element(i));
        wt=wt+atomic_weight(n);
    else 
        j=i-1;
        n=find(l==element(j));
        wt=wt+atomic_weight(n);
        
    end
end

end

• here basically we have entered the elements that appear on the file and stored them into an array \'l\'
• then we have stored their respective atomic weights into another array
• we have initialized the variable \'wt\' to \'0\'
• we have created a for loop to calculate the weight of every element of the molecule
• we check if the particular character to the string is a number or a letter by using the command isletter() which returns 1 if it is a letter and 0 if it is a number
• if it is a letter we will search it the \'l\' array and find its index
• we will then use this index to find the atomic weight of that particular element in atomic_weight array
• the equation wt=wt+atomic_weight(n) updates the value of wt for every cycle
• but if the string is not a letter i mean that the before element has multiple atoms, so we should add te previous element again
• so v=0 now we will find the atomic weight of the element which is present at j=j-1
• we will then search for this element with index j=j-1 in \'l\' array and then use it to update the wt

let's take an example

Element=\'H2O2\'

length(element)=4

the first character of this element string is \'H\' which is a letter so

v=isletter(element(i)); will give ,v=1,j=j

2nd char =2,v=0,j=j-1

3rd char=O,v=1,j=j

2nd char =2,v=0,j=j-1

so the method will return

H+H+O+O=1+1+16+16=34

2)SPECIFIC HEAT CALCULATION

for calculation of specific heat we are going to call a function and pass all the coefficients and the temperature limits of the particular element as arguments to the function

cp=specific_heat(a1(i),a2(i),a3(i),a4(i),a5(i),a6(i),a7(i),a8(i),a9(i),a10(i),a11(i),a12(i),a13(i),a14(i),llt(i),lmt(i),lht(i));

here is the function

function [cp]=specific_heat(a1,a2,a3,a4,a5,a6,a7,a8,a9,a10,a11,a12,a13,a14,llt,lmt,lht)
x=llt
y=lmt
z=lht
r=0.08206;
t=linspace(x,z,(z-x))
for i=1:length(t)
    if t(i)<=lmt
        c(i)=(a1+a2.*t(i)+a3.*t(i).^2+a4.*t(i).^3+a5.*t(i).^4)*r;
    else
        c(i)=(a8+a9.*t(i)+a10.*t(i).^2+a11.*t(i).^3+a12.*t(i).^4)*r;
    end
end
figure(1)
plot(t,c)
title(\'specific_heat\')
xlabel(\'temperature\')
ylabel(\'specific_heat\')
cp=c
end

• here we are going to define a temperature variable which ranges from Local Lower temperature to Local Higher Temperature of the element which we want
• now we are going to calculate for loop to calculate values of cp ate every temperature
• in the loop, we are going to check if the temperature is lower or higher w.t.r Local Mid Temperature as there are different coefficient to the 2 ranges
• after calculating these values are stored in C() array
• and then we are going to plot al these values w.r.t temperature

SPECIFIC HEAT VS TEMPERATURE graph for O2

SPECIFIC HEAT VS TEMPERATURE graph for N2

SPECIFIC HEAT VS TEMPERATURE graph for CO2

3)ENTHALPY CALCULATION

Similar to specific heat here also we call a function and send a similar set of arguments

here is the function

function [h]=enthalpy(a1,a2,a3,a4,a5,a6,a7,a8,a9,a10,a11,a12,a13,a14,llt,lmt,lht)
x=llt
y=lmt
z=lht
r=0.08206;
t=linspace(x,z,(z-x))
for i=1:length(t)
    if t(i)<=lmt
        H(i)=(a1+a2.*t(i)./2+a3.*(t(i).^2)./2+a4.*(t(i).^3)./3+a5.*(t(i).^4)./4+a6./t(i))*r.*t(i);
    else
        H(i)=(a8+a9.*t(i)./2+a10.*(t(i).^2)./2+a11.*(t(i).^3)./3+a12.*(t(i).^4)./4+a13./t(i))*r.*t(i);
    end
end
figure(2)
plot(t,H)
title(\'Enthalpy\')
xlabel(\'temperature\')
ylabel(\'Enthalpy\')
h=H
end

this function is similar to that of specific heat with just the formulas to calculate the result differing

ENTHALPY VS TEMPERATURE graph for O2

ENTHALPY VS TEMPERATURE graph for N2

ENTHALPY VS TEMPERATURE graph for CO2

3)ENTROPY CALCULATION

Similar to the above calculations here also we call a function and send a similar set of arguments

here is the function

function [s]=entropy(a1,a2,a3,a4,a5,a6,a7,a8,a9,a10,a11,a12,a13,a14,llt,lmt,lht)
x=llt
y=lmt
z=lht
r=0.08206;
t=linspace(x,z,(z-x))
for i=1:length(t)
    if t(i)<=lmt
        S(i)=(a1.*log(t(i))+a2.*t(i)+a3.*(t(i).^2)./2+a4.*(t(i).^3)./3+a5.*(t(i).^4)./4+a7)*r;
    else
        S(i)=(a8.*log(t(i))+a9.*t(i)+a10.*(t(i).^2)./2+a11.*(t(i).^3)./3+a12.*(t(i).^4)./4+a14)*r;
    end
end
figure(3)
plot(t,S)
title(\'Entropy\')
xlabel(\'temperature\')
ylabel(\'Entropy\')
s=S
end

this function is also similar to that of specific heat with just the formulas to calculate the result differing

ENTROPY VS TEMPERATURE graph for O2

ENTROPY VS TEMPERATURE graph for N2

ENTROPY VS TEMPERATURE graph for CO2