This paper describes a combined computational and experimental study o
f the flow between contra-rotating disks for -1 less than or equal to
Gamma less than or equal to 0 and Re phi 10(5), where Gamma is the rat
io of the speed of the slower disk to that of the faster one and Re ph
i is the rotational Reynolds number of the faster disk. For Gamma = 0,
the rotor-stator case, laminar and turbulent computations and experim
ental measurements show that laminar Batchelor-type flow occurs: there
is radial outflow in a boundary layer on the rotating disk, inflow on
the stationary disk and a rotating core of fluid between. For Gamma =
-1, the laminar computations produce Batchelor-type flow: there is ra
dial outflow on both disks and inflow in a free shear layer in the mid
-plane, on either side of which is a rotating core of fluid. The turbu
lent computations and the velocity measurements for Gamma = -1 show St
ewartson-type flow: radial outflow occurs in laminar boundary layers o
n the disks and inflow occurs in a non-rotating turbulent core between
the boundary layers. For intermediate values of Gamma, transition fro
m Batchelor-type flow to Stewartson-type flow is associated with a two
-cell structure, the two-cells being separated by a streamline that st
agnates on the slower disk; Batchelor-type flow occurs radially outwar
d of the stagnation point and Stewartson-type flow radially inward. Th
e turbulent computations are mainly in good agreement with the measure
d velocities for Gamma= 0 and Gamma = -1, where either Batchelor-type
flow or Stewartson-type flow occurs; there is less good agreement at i
ntermediate values of Gamma, particularly for Gamma = -0.4 where the d
ouble transition of Batchelor-type flow to Stewartson-type flow and la
minar to turbulent flow occurs in the two-cell structure.