We describe a new numerical 3D relativistic hydrodynamical code and present the results of three validation tests .
A comparison of an axisymmetric jet simulation using the 3D code , with corresponding results from an earlier 2D code , reveal that a ) the enforcement of axisymmetry in the 2D case had no significant influence on the global morphology and dynamics ; b ) although 3D studies typically have lower resolution than those using 2D , limiting their ability to fully capture internal jet structure , such 3D studies can provide a reliable model of global morphology and dynamics .

The 3D code has been used to study the deflection and precession of relativistic flows .
We find that even quite fast jets ( \gamma \sim 10 ) can be significantly influenced by impinging on an oblique density gradient , exhibiting a rotation of the Mach disk in the jet ’ s head .
The flow is bent via a potentially strong , oblique internal shock that arises due to asymmetric perturbation of the flow by its cocoon .
In extreme cases this cocoon can form a marginally relativistic flow orthogonal to the jet , leading to large scale dynamics quite unlike that normally associated with astrophysical jets .
Exploration of a \gamma = 5 flow subject to a large amplitude precession ( semi-angle 11 \fdg 25 ) shows that it retains its integrity , with modest reduction in Lorentz factor and momentum flux , for almost 50 jet-radii , but thereafter , the collimated flow is disrupted .
The flow is approximately ballistic , with velocity vectors not aligned with the local jet ‘ wall ’ .
However , sufficiently large changes in flow direction take place within the jet that for observers close to the jet axis , significant changes in Doppler boost would be evident along the flow .

We consider simple estimators of the flow emissivity in each case and conclude that a ) while the oblique internal shocks which mediate a small change in the direction of the deflected flows have little impact on the global dynamics , significantly enhanced flow emission ( by a factor of 2 - 3 ) may be associated with such regions ; and b ) the convolution of rest frame emissivity and Doppler boost in the case of the precessed jet invariably leads to a core-jet-like structure , but that intensity fluctuations in the jet can not be uniquely associated with either change in internal conditions or Doppler boost alone , but in general are a combination of both factors .