  We present analytic results for warehouse systems involving pairs of
carousels. Specifically, for various picking strategies, we show that the
sojourn time of the picker satisfies an integral equation that is a contraction
mapping. As a result, numerical approximations for performance measures such as
the throughput of the system are extremely accurate and converge fast (e.g.\
within 5 iterations) to their real values. We present simulation results
validating our results and examining more complicated strategies for pairs of
carousels.
