Latin Letters
Ain	impeller inflow area	Q	flow rate
ch	heat capacity	Rcn	Cone radius
Ck	turbulence kinetic energy coefficient	R d1	Diffuser blade inlet radius
Cr	radial component of velocity	R d2	Diffuser blade outlet radius
Cstot*	energy dissipation coefficient	Rhub	Hub arc radius
Ct	tangential component of velocity	R i1	Impeller blade inlet radius
Cvrel	relative velocity coefficient	R i2	Impeller blade outlet radius
Cφ	flow rate coefficient	Rin	Impeller inflow radius
Cω	production term coefficient in SST model	Rshr	Shroud arc radius
F 1	blending function in SST model	s*	specific entropy
fib	impeller blade frequency	Sij	strain tensor
fimp	impeller frequency	Sp	spanwise position
fTEv	diffuser trailing-edge stall frequency	t	time
g	acceleration of gravity	T	temperature
Gz	relative impeller blade channel position	Tin	temperature at inlet boundary
hb	Height of impeller/diffuser blade	Tout	temperature at outlet boundary
hcn	Height of cone	u	velocity
hhub	Height over cone on hub	U i2	Rotational linear speed at impeller outlet
hsta	static enthalpy	Vc	sound speed
htot	total enthalpy	Vin	velocity at inlet boundary
k	turbulence kinetic energy	Vout	velocity at outlet boundary
lk-ω	turbulence scale in SST model	Vrel	relative velocity
Lsp	sound power level	WA	sound power
Mt	specific turbulence kinetic energy	Wref	reference sound power
n	Rotational speed	x	coodinate component
P	turbulence production term in SST model	y +	dimensionless height off-wall
P1, P2, P3, P4	monitoring point 1 to 4	Zd	Diffuser blade number
pin	pressure at inlet boundary	Zi	Impeller blade number
pout	pressure at outlet boundary
Greek Letters
αε	model constant in acoustic analogy	μt	eddy viscosity
βk	model constant in SST model	ρ	density
ΔCstot	specific entropy difference coefficient	σk	model constant in SST model
δij	Kroneker delta	σω	model constant in SST model
ε	eddy dissipation rate	ϕ	denotation for arbitrary parameter
λt	thermal conductivity		in governing equations
μ	dynamic viscosity	ω	specific turbulence dissipation rate
Acronyms
CFD	computational fluid dynamics	LNR	low noise region
EXP	experiment	LVR	low Cvrel region
GGI	general grid interface	RANS	Reynolds-averaged Navier-Stokes
HKR	high k region	REV	impeller revolution
HNR	high noise region	RMS	root mean square
HVR	high Cvrel region	SS	blade suction side
LE	blade leading-edge	SST	shear stress transport
LKR	low k region	TE	blade trailing-edge