1.6 Pneumatic mode

The following variables are in the pneumatic namelist group. If there is a corresponding typeset variable, the notation for that variable is also listed.

Required input variables:

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  d_barrel ($d_{\text{barrel}}$): Inner diameter of the barrel. Floating-point number. Units of m. Note that the projectile outer diameter is assumed to be the same as the barrel inner diameter for the moment.

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  d_chamber ($d_{\text{chamber}}$): Inner diameter of the chamber. Floating-point number. Units of m. The hydraulic diameter ($d_{\text{h}}=4A/P$ where $A$ is area and $P$ is perimeter) can be used if the chamber is non-cylindrical but still elongated.

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  d_e ($d_{\text{e}}$): Effective diameter of the valve. Floating-point number. Units of m. This includes the vena contracta and energy losses due to turbulence, so the effective area is smaller than the actual area available and could be much smaller than the actual area available. Also, because energy losses due to turbulence are a factor, the effective diameter may not correspond to any actual flow area and only means that the flow restriction acts like an orifice of the effective diameter.

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  l_travel ($l_{\text{travel}}$): Distance the base of projectile moves before exiting the barrel. Floating-point number. Units of m. Sometimes called the barrel length, which could be misleading as the material the barrel is constructed from is often longer.

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  m_proj ($m_{\text{proj}}$): Mass of the projectile. Floating-point number. Units of g.

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  p_chamber ($p_{\text{chamber}}$): Initial gauge pressure of the chamber. Floating-point number. Units of kPa.

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  p_fd_proj ($p_{\text{fd,proj}}$): Magnitude of equivalent pressure of dynamic friction on the projectile. Floating-point number. Units of kPa.

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  p_fs_proj ($p_{\text{fs,proj}}$): Pressure difference required to overcome static friction on the projectile. Floating-point number. Units of kPa.

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  vol_chamber ($V_{\text{chamber}}$): Volume of the chamber. Floating-point number. Units of m³.

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  vol_dead ($V_{\text{dead}}$): Dead volume. For pneumatics, this is all the volume from where the valve ends to the base of the projectile. Floating-point number. Units of m³.

Optional input variables:

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  actual_rc: Expected BlasterSim return code corresponding to experimental muzzle velocity set via actual_v_muzzle. Integer. Default value is 0. Ignored outside of BlasterSim validation tests. Used when the projectile should not expected to exit the barrel by setting actual_rc = 1; see § 3.1.1 for other rc codes. The default actual_rc value of 0 is for when the projectile does leave the barrel.

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  actual_v_muzzle ($v_{\text{muzzle}}$): Experimental muzzle velocity for comparison/validation purposes. Floating-point number. Units of m/s. Default value is $0.0$ m/s. Ignored by BlasterSim outside of validation tests, but you can use it to keep track of your own measurements.

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  actual_v_muzzle_n: Sample size for experimental muzzle velocity measurement. Integer. Default value is 0. Ignored outside of BlasterSim validation tests.

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  actual_v_muzzle_stdev (${\sigma }_{v,\text{muzzle}}$): Experimental muzzle velocity standard deviation for comparison/validation purposes. Floating-point number. Units of m/s. Default value is $0.0$ m/s. Ignored by BlasterSim outside of validation tests, but you can use it to keep track of your own measurements.

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  b ($b$): Critical pressure ratio of the valve. Floating-point number. Unitless. Default value is $0.5$.

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  dt ($\mathrm{\Delta }t$): Time step. Floating-point number. Units of s. Default value is $10.0\cdot {10}^{-6}$ s.

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  p_atm ($p_{\text{atm}}$): Atmospheric pressure. Floating-point number. Units of kPa. Default value is $101.325$ kPa.

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  t_opening ($t_{\text{opening}}$): Time required for the valve or flow restriction to fully open. Floating-point number. Units of ms. Default value is $0.0$ ms. See § 2.1.6 for a list of estimated valve opening times.

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  temp_atm ($T_{\text{atm}}$): Atmospheric temperature. Floating-point number. Units of K. Default value is $288.15$ K ($15.00$ C).