Question

Flight-Path Angle (degrees) Coefficient of Lift -0182 0.056 0.097 0.238 0.421 0.479 0.654 0.792 0.924 1.035 1.076 1.103 1.120 1.121 1.121 1.099 1.059 0 10 12 14 15 16 17 18 19 20 21 Assume that we would like to use linear interpolation to determine the coefficient of lift for additional flight-path angles that are between -4 degrees and 21 degrees. Write a C program that allows the user to enter the data for two points and a flight-path angle between those points. The program should then compute the corresponding coefficient of lift

Answer 1

The following shows a sample program run using the input file tunnel.txt (user input in bold).

Range of flight-path angles: -4 to 21 degrees

Please enter a flight-path angle in degrees: -3
Lift coefficient for -3 degrees: -0.119

Would you like to enter another value (Y/N)? y
Please enter a flight-path angle in degrees: -5
****Sorry, -5 is not within data range****

Would you like to enter another value (Y/N)? Y
Please enter a flight-path angle in degrees: 5.5
Lift coefficient for 5.5 degrees: 0.59575

Would you like to enter another value (Y/N)? N


Here is the data file "tunnel.txt":

-4 -0.182
-2 -0.056
0 0.097
2 0.238
4 0.421
6 0.479
8 0.654
10 0.792
12 0.924
14 1.035
15 1.076
16 1.103
17 1.120
18 1.121
19 1.121
20 1.099
21 1.059


And here is my code:
Code:
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#include <iostream>
#include <string>
#include <fstream>

using namespace std;

//Define constants and declare function prototypes
const int T=100;
double maxval(const double x[], int n);
double minval(const double x[], int n);

int main()
{
// Declare objects
int tpts(0);
double y[T], flight_range, coef_lift;
string filename;
ifstream tunnel;

// Prompt user for file name and open date file.
cout << "Enter the name of the data file";
cin >> filename;
tunnel.open(filename.c_str());
if (tunnel.fail())
{
cout << "Error opeing input file\n";
}
else
{
// Read a data value from the file
tunnel >> flight_range >> coef_lift;

// While there is room in the array and
// end of file was not encountered,
// assign the value to the array and
// input the next value.
while (tpts <= T-1 && !tunnel.eof())
{
y[tpts] = flight_range;
tpts++;
tunnel >> flight_range;
}

// Find and print the maximum value
cout << "Range of flight-path angles: " << minval(y,tpts) << " to " << maxval(y,tpts) << " degrees"<< endl;



// Close file and exit program
tunnel.close();
}
return 0;
}

/* ------------------------------------------------------*/
/* This function returns the maximum */
/* value in the array x with n elements */

double maxval(const double x[], int n)
{
// Declare local objects
double max_x;

// Determine maximum value in the array
max_x = x[0];
for (int k=1; k<=n-1; k++)
{
if (x[k] > max_x)
max_x = x[k];
}

// Return maximum value
return max_x;
}

/* ------------------------------------------------------*/
/* This function returns the minimum */
/* value in an array x with n elements */

double minval(const double x[], int n)
{
// Declare objects
double min_x;
// Determine minimum value in the array
min_x = x[0];
for (int k=1; k<=n-1; k++)
{
if (x[k] < min_x)
min_x = x[k];
}

// Return minimum value
return min_x;