1  /****************************************************************
     2   * FUNCTION gas - specifies the working gas properties          *
     3   * FILENAME:       gas.c                                        * 
     4   * PROGRAMMER:     izzi urieli                                  *
     5   * DATE:           95/12/02                                     *
     6   * LAST MODIFICATION: 96/08/16 by I Urieli                      *
     7   * INCLUDE:        <stdio.h>, <string.h>, "define.h"            *
     8   * GLOBAL VARIABLES:                                            *
     9   *    FILE *infile - pointer to the input data file             *
    10   *    FILE *outfile - pointer to the output data file           *
    11   *    FILE *printfile - pointer to the print output file        *
    12   *    double rgas - gas constant (Joules/kg.K)                  *
    13   *    double cp - specific heat at const pressure (J/kg.K)      *
    14   *    double cv - specific heat at const volume (J/kg.K)        *
    15   *    double gama - ratio (cp / cv)                             *
    16   *    double mu0 - dynamic viscosity at ref temp t0 (kg.m/s)    *
    17   *    double t0 - reference temperature (273 K)                 *
    18   *    double t_suth - Sutherland constant for dynamic viscosity *
    19   *    double prandtl - Prandtl number (0.71)                    *
    20   * PROTOTYPE:      void gas(void);                              *
    21   * PRE:  global variables infile, outfile and printfile have    *
    22   *       been specified                                         *
    23   * POST: global variables rgas, cp, cv, gama, mu0, t0, t_suth,  *
    24   *       and Prandtl have been specified                        *
    25   ****************************************************************/
    26  #include <stdio.h>
    27  #include <stdlib.h>
    28  #include "define.h"
    29  
    30  void gas()
    31  {
    32     char mygas[3];
    33  
    34     fgetc(infile); /* remove "return" char from input buffer */
    35     do {
    36        printf("enter gas type: h2 (hydrogen), he (helium),ai (air): ");
    37        fflush(stdin);
    38        fgets(mygas, 3, infile);
    39        if (strcmp(mygas, "h2") == 0) {
    40           fprintf(outfile, "\n%s\n", mygas);
    41           printf(" gastype is hydrogen\n");
    42           fprintf(printfile, "\n gastype is hydrogen\n");
    43           gama = 1.4;
    44           rgas = 4157.2;
    45           mu0 = 8.35e-6;
    46           t_suth = 84.4;
    47        }
    48        else if (strcmp(mygas, "he") == 0) {
    49           fprintf(outfile, "\n%s\n", mygas);
    50           printf("\n gastype is helium\n");
    51           fprintf(printfile, " gastype is helium\n");
    52           gama = 1.67;
    53           rgas = 2078.6;
    54           mu0 = 18.85e-6;
    55           t_suth = 80.0;
    56        }
    57        else if (strcmp(mygas, "ai") == 0) {
    58           fprintf(outfile, "\n%s\n", mygas);
    59           printf(" gastype is air\n");
    60           fprintf(printfile, "\n gastype is air\n");
    61           gama = 1.4;
    62           rgas = 287.0;
    63           mu0 = 17.08e-6;
    64           t_suth = 112.0;
    65        }
    66        else {
    67           printf(" gastype %s is undefined\n", mygas);
    68           strcpy(mygas, "un");
    69        } 
    70     } while (strcmp(mygas, "un") == 0);
    71     cv = rgas / (gama - 1.0);
    72     cp = gama * cv;
    73     t0 = 273.0;
    74     prandtl = 0.71;
    75  }
condor{t.gentry}14: