An apparatus is disclosed including: a housing including a conduit having an inlet port and an outlet port； an insert at least partially disposed within the conduit and including a tapered portion extending from a narrower end proximal the inlet port to a wider end distal the inlet port； and a facility for adjusting the position of the insert within the conduit. In some embodiments, the apparatus is configured to receive a mixed flow of liquid and gas at the inlet port, direct the mixed flow through the conduit around a portion of the insert disposed within the chamber, and outlet the mixed flow at the outlet port.
