while loops , error in use of the word else and else

Question

Eti Rastogi 2020-9-14

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/593476-while-loops-error-in-use-of-the-word-else-and-else

评论： Rik 2020-9-14

Screen Shot 2020-09-14 at 1.25.23 AM.png

在 MATLAB Online 中打开

tank_radius = tank_diameter/2; % finding tank radius

Length_cylindrical_section = (total_tank_length - (2*tank_radius)); % finding length of cylindrical section

% using variables A, B and C to calculate the total tank volume

A = ((pi*(tank_diameter)^2) *((3*tank_radius) - tank_diameter)/3);

B = ((tank_radius)^2) * (acos((tank_radius -tank_diameter)/tank_radius));

C = (tank_radius) - (tank_diameter)*(sqrt((2*tank_radius*tank_diameter)- (tank_diameter)^2));

tank_volume_max = A+Length_cylindrical_section*(B-C);

% using fluid heights to find total volume tolerance

fluid_height1 = tank_radius + (0.5*fluid_height_increment);

fluid_height2 = tank_radius - (0.5*fluid_height_increment);

v_tol = (tank_volume_max * (fluid_height1)) - (tank_volume_max * (fluid_height2));

fluid_height = 0

A = ((pi*(fluid_height)^2) *((3*tank_radius) - fluid_height)/3);

B = ((tank_radius)^2) * (acos((tank_radius - fluid_height)/tank_radius));

C = (tank_radius) - (fluid_height)*(sqrt((2*tank_radius*fluid_height)- (fluid_height)^2));

fluid_volume = A+Length_cylindrical_section*(B-C);

fluid_height1 = tank_radius + (0.5*fluid_height_increment);

fluid_height2 = tank_radius - (0.5*fluid_height_increment);

v_tol = (fluid_volume * (fluid_height1)) - (fluid_volume * (fluid_height2));

safe_tank_volume = safety_percent*tank_volume_max

index_count = 1;

while fluid_volume <= (tank_volume_max - v_tol )

Fluid_height = fluid_height + fluid_height_increment;

index_count = index_count+1;

fprintf('The final fluid volume is %.2f m^3. /n' , fluid_volume);

end

plot (fluid_volume ,fluid_height);

xlabel = 'Fluid Height [m]';

ylabel = 'Fluid Volume [m^3]' ;

title = ' Fluid Volume vs Fluid Height';

%% ____________________

%% FORMATTED TEXT & FIGURE DISPLAY

fprintf(' Tank Radius is %.2f m /n' , tank_radius);

fprintf(' Length of Cylindrical section is %.2f m /n' ,Length_cylindrical_section);

fprintf(' Tank volume is %.2f m^3 /n' ,tank_volume);

fprintf(' Total volume tolerance is %.2f m^3 /n' ,v_tol);

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Eti Rastogi 2020-9-14

i am trying to convert the flowchart into a mathlab script but it is running indefinately and doesnt account for all the changes in the height.

Rik 2020-9-14

Is this a duplicate of your other question? Please edit this one and close that one, or explain what is the difference.

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Answer 1

Jon 2020-9-14

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/593476-while-loops-error-in-use-of-the-word-else-and-else#answer_494413

在 MATLAB Online 中打开

At least one problem you have is in the loop:

while fluid_volume <= (tank_volume_max - v_tol )
    Fluid_height = fluid_height + fluid_height_increment;
    index_count = index_count+1;
    fprintf('The final fluid volume is %.2f m^3. /n' , fluid_volume);
    
end

The termination for this loop is based upon the fluid volume being greater than or equal to the allowable tank volume, but note that you never update the fluid volume inside of the loop. You change the fluid height, but then don't do anything with that value. So since the calculated fluid volume doesn't change the loop runs forever.