1.7 Springer mode

The following variables are in the springer 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_e ($d_{\text{e}}$): Effective diameter of the flow restriction. Floating-point number. Units of m. This includes the vena contracta, so likely the effective area is smaller than the actual area available.

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  d_plunger ($d_{\text{plunger}}$): Inner diameter of the plunger tube. Floating-point number. Units of m.

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  delta_pre (${\mathrm{\Delta }}_{\text{pre}}$): Precompression of the spring. In other words, the amount the spring is compressed at zero draw length. Floating-point number. Units of m. Note that some define a precompression length which is the length of the spring at zero draw length rather than the amount the spring is compressed. The delta/$\mathrm{\Delta }$ notation was chosen to emphasize that BlasterSim uses the amount the spring is compressed. See figure 1.2 for a graphical definition of ${\mathrm{\Delta }}_{\text{pre}}$.

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  k ($k$): Spring stiffness. Floating-point number. Units of N/m.

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  l_draw ($l_{\text{draw}}$): Plunger draw length. Floating-point number. Units of m.

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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_plunger ($m_{\text{plunger}}$): Mass of the plunger. Does not include the mass of the spring. Floating-point number. Units of g.

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

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  m_spring ($m_{\text{spring}}$): Mass of the spring. Floating-point number. Units of g.

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  p_fd_plunger ($p_{\text{fd,plunger}}$): Magnitude of equivalent pressure of dynamic friction on the plunger. 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_plunger ($p_{\text{fs,plunger}}$): Pressure difference required to overcome static friction on the plunger. 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_dead ($V_{\text{dead}}$): Dead volume. For springers, this is all the volume from where the plunger tube 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 flow restriction. 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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  temp_atm ($T_{\text{atm}}$): Atmospheric temperature. Floating-point number. Units of K. Default value is $288.15$ K ($15.00$ C).