git.gag.com Git - debian/openrocket/blob - core/src/net/sf/openrocket/models/atmosphere/AtmosphericConditions.java

   1 package net.sf.openrocket.models.atmosphere;
   2
   3 import net.sf.openrocket.util.BugException;
   4 import net.sf.openrocket.util.MathUtil;
   5 import net.sf.openrocket.util.Monitorable;
   6 import net.sf.openrocket.util.UniqueID;
   7
   8 public class AtmosphericConditions implements Cloneable, Monitorable {
   9
  10         /** Specific gas constant of dry air. */
  11         public static final double R = 287.053;
  12
  13         /** Specific heat ratio of air. */
  14         public static final double GAMMA = 1.4;
  15
  16         /** The standard air pressure (1.01325 bar). */
  17         public static final double STANDARD_PRESSURE = 101325.0;
  18
  19         /** The standard air temperature (20 degrees Celcius). */
  20         public static final double STANDARD_TEMPERATURE = 293.15;
  21
  22
  23
  24         /** Air pressure, in Pascals. */
  25         private double pressure;
  26
  27         /** Air temperature, in Kelvins. */
  28         private double temperature;
  29
  30         private int modID;
  31
  32
  33         /**
  34          * Construct standard atmospheric conditions.
  35          */
  36         public AtmosphericConditions() {
  37                 this(STANDARD_TEMPERATURE, STANDARD_PRESSURE);
  38         }
  39
  40         /**
  41          * Construct specified atmospheric conditions.
  42          *
  43          * @param temperature   the temperature in Kelvins.
  44          * @param pressure              the pressure in Pascals.
  45          */
  46         public AtmosphericConditions(double temperature, double pressure) {
  47                 this.setTemperature(temperature);
  48                 this.setPressure(pressure);
  49                 this.modID = UniqueID.next();
  50         }
  51
  52
  53
  54         public double getPressure() {
  55                 return pressure;
  56         }
  57
  58         public void setPressure(double pressure) {
  59                 this.pressure = pressure;
  60                 this.modID = UniqueID.next();
  61         }
  62
  63         public double getTemperature() {
  64                 return temperature;
  65         }
  66
  67         public void setTemperature(double temperature) {
  68                 this.temperature = temperature;
  69                 this.modID = UniqueID.next();
  70         }
  71
  72         /**
  73          * Return the current density of air for dry air.
  74          *
  75          * @return   the current density of air.
  76          */
  77         public double getDensity() {
  78                 return getPressure() / (R*getTemperature());
  79         }
  80
  81
  82         /**
  83          * Return the current speed of sound for dry air.
  84          * <p>
  85          * The speed of sound is calculated using the expansion around the temperature 0 C
  86          * <code> c = 331.3 + 0.606*T </code> where T is in Celcius.  The result is accurate
  87          * to about 0.5 m/s for temperatures between -30 and 30 C, and within 2 m/s
  88          * for temperatures between -55 and 30 C.
  89          *
  90          * @return   the current speed of sound.
  91          */
  92         public double getMachSpeed() {
  93                 return 165.77 + 0.606 * getTemperature();
  94         }
  95
  96
  97         /**
  98          * Return the current kinematic viscosity of the air.
  99          * <p>
 100          * The effect of temperature on the viscosity of a gas can be computed using
 101          * Sutherland's formula.  In the region of -40 ... 40 degrees Celcius the effect
 102          * is highly linear, and thus a linear approximation is used in its stead.
 103          * This is divided by the result of {@link #getDensity()} to achieve the
 104          * kinematic viscosity.
 105          *
 106          * @return      the current kinematic viscosity.
 107          */
 108         public double getKinematicViscosity() {
 109                 double v = 3.7291e-06 + 4.9944e-08 * getTemperature();
 110                 return v / getDensity();
 111         }
 112
 113
 114         /**
 115          * Return a copy of the atmospheric conditions.
 116          */
 117         @Override
 118         public AtmosphericConditions clone() {
 119                 try {
 120                         return (AtmosphericConditions) super.clone();
 121                 } catch (CloneNotSupportedException e) {
 122                         throw new BugException("CloneNotSupportedException encountered!");
 123                 }
 124         }
 125
 126         @Override
 127         public boolean equals(Object other) {
 128                 if (this == other)
 129                         return true;
 130                 if (!(other instanceof AtmosphericConditions))
 131                         return false;
 132                 AtmosphericConditions o = (AtmosphericConditions) other;
 133                 return MathUtil.equals(this.pressure, o.pressure) && MathUtil.equals(this.temperature, o.temperature);
 134         }
 135
 136         @Override
 137         public int hashCode() {
 138                 return (int) (this.pressure + this.temperature*1000);
 139         }
 140
 141         @Override
 142         public int getModID() {
 143                 return modID;
 144         }
 145
 146         @Override
 147         public String toString() {
 148                 return String.format("AtmosphericConditions[T=%.2f,P=%.2f]", getTemperature(), getPressure());
 149         }
 150
 151 }