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Check whether if the flow is laminar, transitional or turbulent with reynolds numbers using Matlab

Problem

Reynolds number is a dimensionless property, it is used to find the flow type of the fluid. This data is useful is Fluid Mechanics, Heat and Mass transfer and many other subjects. But for our discussion the user will enter the Reynold's number and we will determine the type of the flow using the table below. We will accomplish the task using Matlab.

Flow Type Renolds Number(Re)
Laminar Re< 2300
Transient 2300<Re<4000
Turbulent Re>4000

If you want to know more about Reynolds number then refer to the following links:
1) The engineers toolbox
2) www.efm.leeds.ac.uk
3) Reynolds Number - Wikipedia
This is a main part in Fluid mechanics. You can search more about Reynolds number more in Fluid mechanics books.

Solution

We will ask the user to input the value of Reynolds number and then using the if elseif and else statements we display the type of flow in a neat and beautiful format using the fprintf statement.
Some of the concepts you need to know to solve this problem are as follows:

Program

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re = input('Please enter the Reynold''s number: ');

%We will use the table to write the if elseif and else statements

if re < 2300
    fprintf('The flow is Laminar\n')
elseif 2300<re && re<4000
    fprintf('The flow is Transient\n');
else
    fprintf('The flow is Turbulent\n');
end
I have saved this program as reynolds.m on my local computer

Explanation

Line 1: We are asking the user to input the value of the Reynold's number. You can observe that in the string used in the input function Reynold's is having '' instead of '. If you want to print an apostrophe (') in matlab then in usual programming you will add a backslash(\) in front of the apostrophe('). but here is matlab to do escaping for (') you will have to add two apostrophe('') to do the escaping. Know more about escaping from here: 
Line 3: This is a matlab comment.
Line 5: We are starting an if statement to check if the number(Reynold's) is less than 2300 so that we can execute the next line
Line 6: If the condition or re<2300 is true then the fprintf will get executed and the program comes to halt.
Line 7: This works similar to the if statement but here it is checking if the number that the user has entered is greater than 2300 and also less than 4000. You may have a doubt why I have used two conditions 2300<re and 4000>re to evaluate. The reason is if I will use 2300<re<4000, Matlab checks any condition from left to right. Also remember that a number which is not a zero is always a true if used in condition or if used with Boolean in Matlab. Now to make it simple for you, let us assume that the user has entered a number 5000, Matlab first checks if the number is greater than 2300(2300<re<4000), and that condition is true, now the equation 2300 < re< 400 changes to (True<4000) and which is true(Check True < 400 in your matlab session.). So this condition is true and the elseif statement gets executed displaying the user that the value is transient. But this is not the case for 5000, which is turbulent. So if we have used two conditions, the first condition is true and the second condition is false. Now True && False is False and the elseif statement doesn't gets executed. To know more about Boolean values you can refer:
Line 9: If any of the above conditions in the if elseif doesn't get executed, i.e. if the conditions are not true then the else statement along with line 10 gets executed. 
Line 10: We will display the user that the value he/she has entered is trubulent.

Try it your self

1) In the above program if the user enters 2300 then it will say that the value is Turbulent which is not true in the real case. Modify the above program such that it gives a relevant output. Comment your program in the comment box below.
2) Write a function in matlab which will return the type of fluid flow. Comment your program in the comment box below.

Input/Output 

transient, laminar, turbulent flow determination using Reynold's number using Matlab
Determine the type of fluid flow using Matlab

Final Note

As always if you have any doubt or couldn't understand anything or have any suggestions please do contact me first. I will be happy to help you. You can contact me from here: Contact me
The above program was high lighted using hilite.me web app.
The table was generated easily using csstablegenerator
Keywords: reynolds, fluid flow
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