Cavitation in Hydraulic Machinery, Valves, Piping, and Marine Systems

Nomenclature

The following nomenclature defines the symbols and abbreviations used in this article. Unless otherwise stated, quantities are expressed in SI units.

Symbol	Definition	SI unit or status
A	Exposed area used in erosion measurements	m²
$C_p$	Pressure coefficient	dimensionless
$f_0$	Small amplitude bubble resonance frequency	Hz
$F_L$	Liquid pressure recovery factor for a control valve	dimensionless
H	Pump or turbine head	m
$h_{f,s}$	Suction line friction and minor loss	m
M	Absolute NPSH margin	m
$M_R$	NPSH margin ratio	dimensionless
MDER	Mean depth of erosion rate	m s⁻¹ or µm h⁻¹
n	Rotational speed	s⁻¹ or r min⁻¹
$NPS{H}_A$	Net positive suction head available	m
$NPS{H}_R$	Net positive suction head required	m
$NPS{H}_3$	NPSH at a 3 percent pump head drop	m
$N_{ss}$	Suction specific speed under a stated unit convention	convention dependent
p	Absolute static pressure	Pa
$p_B$	Pressure at the bubble wall	Pa
$p_v$	Saturation vapor pressure	Pa
$p_{vc}$	Pressure at the vena contracta	Pa
$P_h$	Hydraulic power	W
$P_{shaft}$	Pump shaft power	W
Q	Volumetric flow rate	m³ s⁻¹
R	Bubble radius	m
$t_c$	Ideal collapse time	s
V	Mean liquid velocity	m s⁻¹
$V_{R(r)}$	Local resultant propeller velocity at radius r	m s⁻¹

Greek Letters

Symbol	Letter name	Meaning in this chapter
γ	Gamma	Surface tension
κ	Kappa	Polytropic exponent
μ	Mu	Dynamic viscosity
ρ	Rho	Liquid or solid density
σ	Sigma	Cavitation number
${\sigma }_v$	Sigma	Valve cavitation index
${\sigma }_T$	Sigma	Thoma cavitation coefficient
η	Eta	Efficiency
Δ	Delta	Finite difference or measured change