A hydrocyclone (1) for separating a liquid mixture into a heavy fraction including heavy particles and alight fraction, comprising a housing (2) forming an elongated separation chamber (3) having a circumferential wall (4), abase end (5),an apex end (6),at least one inlet member (7) for supplying a liquid mixture into the separation chamber (3), at least one of the inlet member/s(7) positioned at the base end (5), a first outlet member (8) for discharging separated light fraction from the separation chamber (3)at the base end (5), a second outlet member (9) for discharging separated heavy fraction from the separation chamber (3) at the apex end (6),means (10) for supplying the liquid mixture to the separation chamber (3) via the at least one inlet member (7), so that during operation a liquid stream is generated as a helical vortex (11) about a centre axis (12) in the separation chamber (3), said helical vortex (11) extending from the base end (5) to the apex end (6), a first flow deflection means arranged in the circumferential wall (4) which comprises at least one member(14) in the path 13 of the liquid stream showing a decrease of the radius of the separation chamber, followed by an increase of the radius of the separation chamber,where in the at least one member comprises a rounded curve portion 14a for transporting the heavy particles.